Exoclimes_Conference_booklet1
Exoclimes_Conference_booklet1
Exoclimes_Conference_booklet1
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PROGRAMME & ABSTRACTS<br />
1
3<br />
! General information! ! ! ! 4<br />
!<br />
! Programme!! ! ! ! ! 5<br />
!<br />
! List of Participants! ! ! ! 10<br />
! Abstract of contributions! ! ! 14<br />
!<br />
Insights from Solar System planets! ! 14<br />
Terrestrial planets! ! ! ! 22<br />
Super-Earths and hot Neptunes! ! 31<br />
Hot Jupiters: observations! ! ! 38<br />
Hot Jupiters: models! ! ! ! 51<br />
Young giant planets and brown dwarfs! 57
Presentation<br />
Venue<br />
Davos is a winter resort in the East of Switzerland, at 1560 m one of the<br />
highest town in the Alps. Its showpiece is the <strong>Conference</strong> Centre, which<br />
hosts the World Economic Forum every year.<br />
<strong>Exoclimes</strong><br />
Previous <strong>Exoclimes</strong> conferences have taken place in Exeter, UK, in<br />
September 2010, and Aspen, CO in January 2012. The objective of these<br />
conferences is to bring together specialists of the Earth, Solar System<br />
planets and exoplanets to discuss the new field of comparative<br />
planetology outside the Solar System.<br />
Contact<br />
In case of need during the conference, contact the organisers at<br />
exoclimes@gmail.com or call +41 77 418 58 12.<br />
Emergency numbers in Switzerland are<br />
117 for police,<br />
118 for fire and<br />
144 for ambulance.<br />
4
<strong>Exoclimes</strong> III<br />
Exploring the Diversity of Planetary Atmospheres<br />
Davos 9-14 February 2014<br />
Monday 10th<br />
Programme<br />
8:00! Desk opens<br />
8:50! Welcome address<br />
Session: Earth-like atmospheres<br />
9:00! Exotic atmospheres (review): Pierrehumbert<br />
9:40! A new perspective on the inner edge of the habitable zone: Leconte<br />
10:05! Break<br />
10:30! Paleo-climates (review): Abbot<br />
11:10! Exoplanetary extreme space weather: Cohen<br />
11:35! Terrestrial planet atmospheres in the aftermath of giant impacts: Lupu<br />
12:00 ! Lunch break<br />
Session: Interiors<br />
17:00! Interior-atmosphere interactions (review): Elkins-Tanton<br />
17:40! Earth’s interior dynamics (review): Tackley<br />
18:05! Break<br />
18:20! Magneto-hydro-dynamics: T. Rogers<br />
19:00! Evening break<br />
5
Programme<br />
Tuesday 11th<br />
Session: Exoplanet observations<br />
8:30! Exoplanet transit observations (review): Desert<br />
9:10! Characterising exoplanet atmospheres with HST/WFC3: Mandell<br />
9:35! Revealing distant worlds with ground-based spectroscopy: Stevenson<br />
10:00! Break<br />
10:30! Exoplanet eclipse/phase observations (review): Knutson<br />
11:10! Observation highlights –<br />
! Ground-based detection of water in hot Jupiters: Birkby<br />
! Probing the atmosphere of non-transiting planets: Brogi<br />
! 2D mapping of the eccentric planet HAT-P-2b: de Wit<br />
! Mapping clouds in exoplanet atmospheres: Demory<br />
! Measuring the reflection signal of HD 189733b: Evans<br />
! Atmosphere of exo-Neptune HAT-P-11b: Fraine!<br />
! Transmission spectroscopy of super-Earth GJ1214b: Kreidberg<br />
! HST/STIS transmission spectral survey: Nikolov<br />
12:00 ! Lunch break<br />
14:00! Workshop on transit observations: Sing<br />
Session: Clouds and hazes<br />
17:00! Photochemistry (review): Moses<br />
17:40! Overcoming remote sensing challenges for cloudy atmospheres: Barstow<br />
18:05! Break<br />
18:20! Recent advances in exoplanet climate simulations: Showman<br />
19:00! Evening break<br />
6
Wednesday 12th<br />
Session: Circulation models<br />
8:30! Exoplanet circulation models (review): Menou<br />
9:10! Non-hydrostatic, deep-atmosphere hot Jupiter climate models : Mayne<br />
9:35! Water loss from N2/CO2-atmosphere terrestrial planets: Wordsworth<br />
Programme<br />
10:00! Break<br />
Session: Evaporation and energy<br />
10:30! Global energy budgets for terrestrial and gas giant exoplanets: Read<br />
11:10! Models of exoplanet evaporation: Owen<br />
11:35! Enshrouded close-in exoplanets : Haswell<br />
12:00 ! Lunch break<br />
Session: Outer Solar System<br />
17:00! Titan’s atmosphere (review): Mitchell<br />
17:40! Measurement of the atmospheres of Europa, Ganymede and Callisto: Wurz<br />
18:05! Break<br />
18:20! Jupiter’s atmosphere (review): Kaspi<br />
19:00! Evening break<br />
7
Programme<br />
Thursday 13th<br />
Session: Brown dwarfs and directly-imaged planets<br />
8:30! Brown dwarf observations (review): Apai<br />
9:10! Results from the “Weather on other worlds” Spitzer campaign : Metchev<br />
9:35! Doppler imaging of a nearby cloudy brown dwarf: Crossfield<br />
10:00! Break<br />
10:30! Model brown dwarf spectra (review): Barman<br />
11:10! Connecting low-gravity brown dwarfs and directly-imaged planets: Liu<br />
11:35! The mid-infrared properties of directly-imaged planets: Skemer<br />
12:00 ! Lunch break<br />
Session: Synthetic spectra<br />
17:00! Model exoplanet spectra (review): Fortney<br />
17:40! Simulated transit spectra of Earth and Jupiter: Irwin<br />
18:05! Break<br />
18:20! Poster session<br />
19:00! Evening break<br />
8
Friday 14th<br />
Session: Atmospheric retrieval<br />
8:30! Chemical characterisation of super-Earths: Madhusudhan<br />
8:55! A comparison of exoplanet retrieval techniques: Line<br />
9:20! The atmospheres of GJ1214b and GJ436b: Benneke<br />
9:40 ! Discussion<br />
Programme<br />
10:00! Break<br />
Session: Theory<br />
10:30! Helium-dominated atmosphere on Neptune-size GJ436b: R. Hu<br />
10:55! Ionisation regimes structuring planetary atmospheres: Helling<br />
11:20! Ocean transport in the climate of exoplanets around M-dwarf stars:<br />
! Y. Hu<br />
11:40 ! Atmospheric super-rotation: Lewis<br />
12:00 ! Lunch break<br />
Session: Earth-like exoplanets<br />
17:00! Climate dynamics (review): Schneider<br />
17:40! Climate and photochemistry of potentially habitable exoplanets: Tian<br />
18:05! Break<br />
18:20! The prospects for characterizing the atmospheres of rocky exoplanets:<br />
! Charbonneau<br />
19:00! Evening break<br />
9
Participants<br />
PARTICIPANTS<br />
Dorian! Abbot! University of Chicago<br />
Miquela! Abbot! University of Chicago<br />
Nadine! Afram! Kiepeneheuer Inst. für Sonnenphysik! p. 51<br />
Suzanne! Aigrain! University of Oxford<br />
Yann! Alibert! University of Bern! p. 22<br />
David! Amundsen! University of Exeter! p. 52<br />
Daniel! Angerhausen! Rensselaer Polytechnic Institute! p. 38<br />
Daniel! Apai! University of Arizona<br />
Jeremy! Bailey! University of New South Wales! p. 39<br />
Travis! Barman! University of Arizona<br />
Joanna! Barstow! University of Oxford! p. 14<br />
Jean-Loup! Baudino! LESIA, Observatoire de Paris! p. 57<br />
Jacob! Bean! University of Chicago<br />
Thomas! Beatty! Ohio State University! p. 58<br />
Björn! Benneke! California Institute of Technology! p. 31<br />
Andrei! Berdyugin! FINCA, University of Turku! p. 39<br />
Svetlana! Berdyugina! Kiepeneheuer Inst. für Sonnenphysik! p. 22<br />
Zachory! Berta-Thompson! Massachusetts Inst. of Technology! p. 32<br />
Jayne! Birkby! Leiden Observatory! p. 39<br />
Jasmina! Blecic! University of Central Florida! p. 52<br />
Kimberly! Bott! University of New South Wales! p. 52<br />
Vincent! Bourrier! Institut d’Astrophysique de Paris! p. 40<br />
Matteo! Brogi! Leiden Observatory! p. 40<br />
Carolyn! Brown! University of Southern Queensland<br />
Matthew! Browning! University of Exeter<br />
Ben! Burningham! University of Hertfordshire! p. 58<br />
Ludmila! Carone! CmPA, KU Leuven! p. 23<br />
David! Charbonneau! Harvard University! p. 23<br />
Ofer! Cohen! Harvard-Smithsonian CfA! p. 24<br />
Vincent! Coudé du Foresto! Paris Observatory / Bern University<br />
Nicolas! Cowan! Northwestern University! p. 32<br />
Ian! Crossfield! Max Plank Institute for Astrophysics! p. 58<br />
Nicolas! Crouzet! Dunlap Institute, University of Toronto! p. 41<br />
Patricio! Cubillos! University of Central Florida! p. 41<br />
Mario! Damasso! INAF-Astrophysical Obs. of Torino! p. 32<br />
Remco! de Kok! SRON / Leiden Observatory! p. 41<br />
Julien! de Wit! Massachusetts Institute of Technology! p. 42<br />
Laetitia! Delrez! University of Liège<br />
Brice-Olivier! Demory! Massachusetts Institute of Technology! p. 42<br />
Jean-Michel! Desert! University of Colorado<br />
Hannah! Diamond-Lowe! University of Chicago<br />
10
Ian! Dobbs-Dixon! NYU Abu Dhabi! p. 53<br />
Caroline! Dorn! University of Bern<br />
Diana! Dragomir! University of California/LCOGT! p. 33<br />
Benjamin! Drummond! University of Exeter<br />
Siegfried! Eggl! IMCCE, Observatoire de Paris! p. 24<br />
Lindy! Elkins-Tanton! DTM, Carnegie Institution<br />
Justin! Erwin! University of Arizona! p. 53<br />
Lisa! Esteves! University of Toronto! p. 43<br />
Tom! Evans! University of Oxford! p. 43<br />
Jacqueline! Faherty! Carnegie Institution of Washington, DTM<br />
Sean! Faulk! University of California, Los Angeles! p. 14<br />
Dora! Fohring! Durham University! p. 43<br />
Doris! Folini! ETH Zürich<br />
Jonathan! Fortney! University of California-Santa Cruz<br />
Jonathan! Fraine! University of Maryland! p. 33<br />
Richard! Freedman! SETI Institute<br />
Sebastien! Fromang! CEA Saclay<br />
Antonio! GarcÌa Muñoz! RSSD, European Space Agency! p. 19<br />
Neale! Gibson! European Southern Observatory! p. 43<br />
Daniel! Gisler! Kiepeneheuer Institut für Sonnenphysik! p. 15<br />
John Lee! Grenfell! German Aerospace Centre (DLR)! p. 24<br />
Simon! Grimm! University of Zurich! p. 53<br />
Sandrine! Guerlet! Laboratoire de Métrologie Dynamique! p. 15<br />
Aimee! Hall! University of Cambridge! p. 34<br />
Joseph! Harrington! University of Central Florida! p. 44<br />
Carole! Haswell! The Open University! p. 44<br />
Christiane! Helling! University of St Andrews! p. 59<br />
Kevin! Heng! University of Bern! p. 54<br />
Klemens! Hocke! University of Bern<br />
Jens! Hoeijmakers! Leiden Observatory<br />
Derek! Homeier! CRAL/ENS-Lyon! p. 59<br />
Yasunori! Hori! National Astronomical Observatory Japan! p. 34<br />
Andrew! Howard! University of Hawaii<br />
Renyu! Hu! California Institute of Technology! p. 34<br />
Yongyun! Hu! Peking University! p. 25<br />
Nicolas! Iro! Klimacampus - University of Hamburg! p. 54<br />
Patrick! Irwin! Oxford University! p.16<br />
Kate! Isaak! ESTEC, European Space Agency<br />
Joshua! Kammer! California Institute of Technology! p. 35<br />
Yohai! Kaspi! Weizmann Institute of Science<br />
Tiffany! Kataria! University of Arizona! p. 25<br />
Hajime! Kawahara! University of Tokyo! p. 45<br />
Lucyna! Kedziora-Chudczer University of New South Wales! p.16<br />
Participants<br />
11
Participants<br />
Sara! Khalafinejad! Hamburg Observatory<br />
Flavien! Kiefer! IAP! p. 60<br />
Cevahir! Kilic! University of Bern! p. 26<br />
Daniel! Kitzmann! Technical University Berlin! p. 55<br />
Heather! Knutson! California Institute of Technology<br />
Daniel! Koll! University of Chicago! p. 36<br />
Thaddeus! Komacek! University of Arizona! p. 55<br />
Tommi! Koskinen! University of Arizona! p. 56<br />
Nadia! Kostogryz! Kiepeneheuer Inst. für Sonnenphysik p.16<br />
Laura! Kreidberg! University of Chicago! p. 36<br />
Oleksii! Kuzmychov! Kiepeneheuer Inst. für Sonnenphysik!p. 60<br />
Panayotis! Lavvas! CNRS (France)<br />
Alain! Lecavelier! Institut d’Astrophysique deParis! p. 56<br />
Jeremy! Leconte! CITA/LMD! p. 26<br />
Jae-Min! Lee! University of Zurich! p. 60<br />
Emmanuel! Lellouch! Observatoire de Paris<br />
Stephen! Lewis! The Open University! p. 17<br />
Michael! Line! University of California-SC! p. 61<br />
Jeffrey! Linsky! University of Colorado<br />
Michael! Liu! University of Hawaii! p. 61<br />
Joe! Llama! University of St Andrews! p. 45<br />
Eric! Lopez! UC Santa Cruz! p. 36<br />
Roxana! Lupu! SETI Institute! p. 27<br />
Nikku! Madhusudhan! University of Cambridge! p. 37<br />
Jared! Males! University of Arizona! p. 61<br />
Luigi! Mancini! Max Planck Insitute for Astronomy<br />
Avi! Mandell! NASA Goddard! p. 46<br />
Nadejda! Marounina! Laboratoire de Planetologie, Nantes! p. 17<br />
Stephen! Marsden! University of Southern Queensland! p. 27<br />
Nathan! Mayne! University of Exeter! p. 56<br />
Victoria! Meadows! University of Washington<br />
Joao! Mendonca! University of Bern! p.18<br />
Kristen! Menou! Columbia University<br />
Stephen! Messenger! Massachusetts Inst.of T echnology<br />
Stanimir! Metchev! University of Western Ontario! p. 62<br />
Alison! Mitchell! University of Californa LA<br />
Jonathan! Mitchell! University of Californa LA<br />
Pilar! Montanes-Rodriguez Inst. de Astrofisica de Canarias! p. 18<br />
Caroline! Morley! University of California-Santa Cruz! p. 62<br />
Katie! Morzinski! University of Arizona! p. 62<br />
Julie! Moses! Space Science Institute<br />
Norio! Narita! National Astronomical Obs. Japan! p. 37<br />
Nikolay! Nikolov! University of Exeter! p. 46<br />
Lisa! Nortmann! Institut für Astrophysik Göttingen! p. 47<br />
Joseph! O'Rourke! California Institute of Technology! p. 47<br />
12
James! Owen! CITA! p. 48<br />
Hannu! Parviainen! University of Oxford! p. 48<br />
Enric! Palle! Instituto de Astrofisica de Canarias! p. 48<br />
Raymond! Pierrehumbert!University of Chicago<br />
Frédéric! Pont! University of Exeter<br />
Max! Popp! Max Planck Institute for Meteorology! p. 28<br />
Ramses! Ramirez! Pennsylvania State University<br />
Peter! Read! University of Oxford! p. 19<br />
Tyler! Robinson! NASA Ames Research Center! p. 20<br />
Leslie! Rogers! California Institute of Technology! p. 37<br />
Tamara! Rogers! University of Arizona<br />
Sarah! Rugheimer! Harvard University<br />
Josiane! Salameh! Max Planck Institute for Meteorology! p. 28<br />
Tapio! Schneider! ETH Zürich<br />
Henriette! Schwarz! Leiden Observatory! p. 49<br />
Aomawa! Shields! University of Washington! p. 29<br />
Adam! Showman! University of Arizona<br />
Avi! Shporer! Caltech/JPL! p. 49<br />
David! Sing! University of Exeter<br />
Andrew! Skemer! University of Arizona! p. 63<br />
Kevin! Stevenson! University of Chicago! p. 50<br />
Paul! Tackley! ETH Zürich<br />
Zhihong! Tan! Caltech/JPL! p. 29<br />
Feng! Tian! Peking University! p. 29<br />
Kamen! Todorov! ETH Zürich! p. 50<br />
Pascal! Tremblin! University of Exeter<br />
Vincent! Van Eylen! Aarhus University! p. 50<br />
Tamas Norbert ! Varga! Eötvös Lorand University<br />
Giovanni! Vladilo! INAF-Astrophysical Obs. of Torino<br />
Hannah! Wakeford! University of Exeter! p. 51<br />
Yuwei! Wang! Peking University<br />
Paul Anthony! Wilson! University of Exeter! p. 63<br />
Peter! Woitke! University of St Andrews! p. 57<br />
Robin! Wordsworth! University of Chicago! p. 30<br />
Peter! Wurz! University of Bern! p. 20<br />
Aurélien! Wyttenbach! University of Geneva! p. 38<br />
Fei! Yan! ESO! p. 21<br />
Jun! Yang! University of Chicago! p. 30<br />
Angela! Zalucha! SETI Institute! p. 21<br />
Robert! Zellem! University of Arizona! p. 51<br />
Andras! Zsom! Massachusetts Institute of Technology! p. 31<br />
Participants<br />
13
TALKS/POSTERS ABSTRACTS *<br />
INSIGHTS FROM SOLAR SYSTEM PLANETS<br />
Gloomy planets: overcoming remote sensing challenges for cloudy atmospheres<br />
Joanna K. Barstow — University of Oxford<br />
For most known planets, our only knowledge about their atmospheres comes from remote<br />
sensing and spectroscopic analysis. There are often multiple, degenerate atmospheric<br />
states that could produce the observed spectra, and usually more complex atmospheric<br />
models result in greater numbers of permitted atmospheric states. The inclusion of clouds<br />
in an atmospheric model increases its complexity. The size of the cloud parameter space,<br />
the nature of the condensate, size of condensate particles, number density and location<br />
within the atmosphere all influence spectral features.<br />
Recent analyses of the best-studied extrasolar planets, such as HD 189733b and GJ<br />
1214b, indicate that clouds are as ubiquitous outside the solar system as they are inside it.<br />
Their probable presence on these planets can no longer be ignored, but the quality and<br />
spectral coverage of remote sensing data for exoplanets and the outer planets in our own<br />
solar system limits our ability to draw conclusions about their nature. We are left with a<br />
vast, underconstrained model parameter space to explore. In addition, the presence of<br />
uncharacterised clouds in planetary atmospheres can prevent us from placing constraints<br />
on temperature structure and chemistry due to model degeneracy, or can result in<br />
mistaken conclusions based on incorrect assumptions.<br />
I explore the significance of different cloud properties for reflection, emission and<br />
transmission spectra of planetary atmospheres, including examples such as the extremely<br />
detailed characterisation of the H2SO4 cloud on Venus, the hints of enstatite clouds on HD<br />
189733b, and the possibility of Titan-like hydrocarbon hazes on GJ 1214b. I will present<br />
suggestions for a framework to explore cloudy solutions for data-poor planets.<br />
The structure of the Intertropical Convergence Zone over a wide range of<br />
atmospheric circulations simulated with an idealized GCM!<br />
Sean Faulk — UCLA!<br />
One of the most prominent features of the Earth's large-scale circulation in low latitudes is<br />
the intertropical convergence zone (ITCZ), where tropical precipitation is concentrated in a<br />
relatively narrow latitudinal band. Given that small changes in the ITCZ can result in large<br />
local changes in precipitation, factors that control its structure and position have been<br />
widely investigated in the literature. In other planetary settings such as Mars and Titan, it<br />
has been argued that an ITCZ can migrate significantly off the equator into the summer<br />
hemisphere, perhaps even to the summer pole. The dynamical, thermodynamical and<br />
radiative mechanisms controlling seasonal ITCZ migrations has only begun to be explored.<br />
Exploration of the ITCZ behavior in a wide parameter space is important to understand the<br />
fundamental dynamics of the Earth's ITCZ and also to characterize climates on other<br />
planets. Here, we examine the structure of the ITCZ over a wide range of atmospheric<br />
* Arranged by topic in six categories. See the list of participants (p.10) to find page of specific abstract<br />
14
circulations with an idealized General Circulation Model (GCM), in which an atmospheric<br />
model with idealized physics is coupled to an aquaplanet slab ocean of fixed depth and the<br />
top-of-atmosphere insolation is varied seasonally. A broad range of circulation regimes is<br />
studied by changing the thermal inertia of the slab ocean, the planet rotation rate and<br />
radius while keeping the seasonal cycle of insolation fixed. The climates of Earth, Mars<br />
and Titan will be discussed in this context, and implications for classifying exoplanet<br />
climates will be drawn.<br />
A search for hot water vapor in the atmosphere of Venus during the 2012 transit<br />
Daniel Gisler — Kiepenheuer-Institut für Sonnenphysik<br />
We have observed the Venus transit in 2012 using the Scatter-free Observatory for Limb<br />
Active Regions and Coronae (SOLARC), located on the summit of Haleakala, Maui. The<br />
SOLARC is a 45 cm off-axis Gregorian telescope. This telescope design minimizes<br />
scattered light, that is critical for photon-limited observations. The data has been collected<br />
with the Optical Fiber Imaging Spectralpoarimeter (OFIS). Our goal is to search for water<br />
vapor lines absorbing solar light passing through the Venusian atmosphere and evaluate<br />
the sensitivity of our spectropolarimetric technique to detect water and other constituents<br />
in atmospheres of transiting exoplanets. Here we present the data and analyze Stokes I,<br />
Q, U spectra extracted from the solar disk and the Venus limb and night side. We estimate<br />
limits on the water vapor partial pressure and compare these with measurements by space<br />
missions and probes.<br />
Development of a new Global Climate Model of Saturn's stratosphere<br />
Sandrine Guerlet — Laboratoire de Météorologie Dynamique, Paris!<br />
Recent observations of Saturn’s stratospheric thermal structure and composition have<br />
revealed new phenomena: an equatorial oscillation in temperature, reminiscent of the<br />
Earth's Quasi-Biennal Oscillation ; strong meridional contrasts of hydrocarbons ; a warm<br />
“beacon” associated with the powerful 2010 storm. Those signatures cannot be<br />
reproduced by 1D photochemical and radiative models and suggest that atmospheric<br />
dynamics plays a key role. This motivated us to develop a complete 3D General<br />
Circulation Model (GCM) for Saturn, based on the LMD’s hydrodynamical core, to explore<br />
the circulation, seasonal variability, and wave activity in Saturn's atmosphere.<br />
In order to closely reproduce Saturn's radiative forcing, a particular emphasis was put in<br />
obtaining fast and accurate radiative transfer calculations. Our radiative model uses<br />
correlated-k distributions and spectral discretization tailored for Saturn's atmosphere. We<br />
include an internal heat flux, ring shadowing and both tropospheric and stratospheric<br />
aerosols.<br />
Firstly, we will present a comparison of temperature fields obtained with this new<br />
seasonal, radiative equilibrium model to that inferred from Cassini/CIRS observations.<br />
Even in the absence of dynamics, our model qualitatively reproduces the overall<br />
meridional temperature gradient between the summer and the winter hemispheres in the<br />
lower stratosphere except in the equatorial region, where the temperature structure is<br />
governed by the dynamical equatorial oscillation. Our model can also reproduce the<br />
“temperature knee” observed around 200 mbar, which is caused by heating at the top of<br />
the tropospheric aerosol layer.<br />
15
Finally, we will show GCM simulations coupling the 3D dynamical core to this radiative<br />
model, and discuss the large-scale stratospheric circulations driven by the radiative<br />
forcing.<br />
Simulated transit spectra of Earth and Jupiter<br />
Patrick Irwin — University of Oxford<br />
In recent years, increasingly accurate measurements have been made of the transit<br />
spectra of hot Jupiters, such as HD 189733b, from the visible through to mid-infrared<br />
wavelengths. These have been modelled to derive the likely atmospheric structure and<br />
composition of these planets. As measurement techniques improve, the transit spectra of<br />
super-Earths such as GJ 1214b are becoming increasingly accessible, allowing model<br />
atmospheric states to be fitted for this class of planet also. While it is not yet possible to<br />
constrain the atmospheric states of solar system-like planets such as the Earth or Jupiter<br />
from such measurements, it is hoped that this might one day become practical; if so, it is of<br />
interest to determine what we might infer from such measurements. In this work we have<br />
constructed atmospheric models of Earth and Jupiter from 0.2 - 15 microns that are<br />
consistent with ground-based and satellite observations. From these models we calculate<br />
the primary and secondary transit spectra (with respect to the Sun) that would be observed<br />
by a remote observer, many light years away, and also directly imaged spectra, assuming<br />
that this one day becomes technically feasible. From these spectra we test how well<br />
optimal estimation retrieval models can determine the atmospheric states and compare<br />
these with the “ground truths” in order to assess: a) the inherent difficulty in using transit<br />
spectra observations to observe solar system-like targets; b) the relative merits of primary<br />
versus secondary transit spectra; and c) the optimal wavelength coverage, resolutions and<br />
sensitivities required to retrieve useful information about the atmospheres of such planets.<br />
D/H ratios in methane in the atmosphere of giant planets and Titan!<br />
Lucyna Kedziora-Chudczer — University of New South Wales<br />
We present observations of the GNIRS/GEMINI high resolution spectra at 1.58 and 2.03<br />
microns for the giant planets of our Solar System and Saturn's moon Titan. We fitted the<br />
atmospheric absorption spectra of these objects using the VSTAR line-by-line radiative<br />
transfer modelling to estimate the D/H ratios from deuterated methane in both bands.<br />
Deuteration of the outer planets can be used not only as a diagnostic of initial conditions in<br />
the solar nebula during formation of giant planets but also to help to determine the location<br />
at which planets accreted the bulk of their mass. We estimated that based on D/H ratio<br />
derived for Titan, the Saturnian system formed close to its current location, which has<br />
implication on previously proposed migration theories.<br />
Vertical structure of gas-planet atmospheres inferred from methane bands<br />
Nadiia Kostogryz — Kiepenheuer-Institut für Sonnenphysik<br />
Visible and near infrared spectra of the Jovian planets in the Solar system are dominated<br />
by methane absorption features. These bands are very useful for determining the vertical<br />
cloud structure of planetary atmospheres as was proposed by Morozhenko (1984) and<br />
implemented for the Uranus atmosphere by Kostogryz (2013). The fact that the diffusely<br />
reflected radiation is formed at different effective depths in the atmosphere allows to<br />
constrain the vertical cloud structure. The cloud height and opacity strongly influence the<br />
16
geometric albedo of the planet and, therefore, are needed for constructing a realistic<br />
atmosphere model. Here we extend this method to exoplanetary atmospheres. We<br />
simulate methane spectra from atmospheres with various cloud structure and analyze<br />
them as observed spectra to infer the cloud properties. We investigate limits on the<br />
spectral resolution and signal-to-noise ratio for this technique to be applied to hot Jupiter<br />
atmospheres.<br />
Atmospheric super-rotation in solar system and extra-solar planetary atmospheres<br />
Stephen R. Lewis — The Open University, UK<br />
Super-rotation is a common phenomenon in solar system planetary atmospheres. Out of<br />
the four substantial atmospheres possessed by solid bodies in the solar system, the slowly<br />
rotating planet, Venus, and moon, Titan, are both well-known to have atmospheres that<br />
rotate on average substantially more quickly than does the solid surface underneath. The<br />
more rapidly rotating planets, Mars and Earth, have much weaker global super-rotation,<br />
but both can exhibit time-varying prograde jets near the equator which rotate more rapidly<br />
than the local surface. Atmospheric super-rotation is not restricted to planets with solid<br />
surfaces and shallow atmospheres. Cloud-tracking observations of the gas giants Jupiter<br />
and Saturn show that they both possess rapid prograde equatorial jets and hence exhibit<br />
local super-rotation.<br />
Simplified global circulation models of extra-solar planets, including representations of<br />
hot Jupiters and Earth-like planets rotating at different rates, can also show sustained<br />
super-rotating equatorial jets in different dynamical regimes. In the extra-solar planet<br />
cases in particular, the quantitative results are highly sensitive to model parameters.<br />
In each case the detailed mechanism, or combination of mechanisms, which produces<br />
the super-rotating jets might vary, but all require longitudinally asymmetric motions, waves<br />
or eddies, to transport angular momentum up-gradient into the jets. The mechanism is not<br />
always easy to diagnose from observations and requires careful modelling. We review<br />
both observations of solar system planets and recent global circulation model results,<br />
combined in the case of Mars and Earth in the form of atmospheric reanalyses by data<br />
assimilation, together with simplified extra-solar planet simulations.<br />
Generation and early evolution of Titan's atmosphere<br />
Nadejda Marounina! — LPGN!<br />
Titan is the only satellite of the Solar System with a substantial atmosphere (1.47 bar),<br />
which is primarily composed of N2 (~98%) and CH4 (~ 2%). The low Ar/N2 ratio measured<br />
by the Huygens probe in Titan's atmosphere indicates that the nitrogen was incorporated<br />
as NH3 and possibly other nitrogen-bearing easily condensible compounds. Therefore, a<br />
conversion mechanisms is needed to explain the present-day N2-dominated atmosphere.<br />
Different conversion scenarios have been proposed (endogenic conversion, atmospheric<br />
impact chemistry...). Here we evaluate a scenario recently proposed by Sekine et al.<br />
(2011) involving an impact-induced conversion of NH3, stored as hydrate in Titan’s icy<br />
crust, and subsequent degassing of N2 during the Late Heavy Bombardement. Using the<br />
scaling laws derived from their experimental study, we computed the balance between the<br />
degassed N2 and the erosion of the atmosphere by impact (Shuvalov 2009) for an impact<br />
population characteristic of the Late Heavy Bombardment (LHB). Our numerical model<br />
include a parameterized description of the radiative and thermodynamical equilibria of the<br />
atmosphere (Lorenz et al. 1999).<br />
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Our results show that whatever the size of NH3-enriched crustal reservoirs, N2 production<br />
by impacts is not able to counterbalance the atmospheric loss by impact erosion for<br />
realistic size distribution of impactors. We show that in order to preserve a substantial<br />
atmosphere on Titan after the LHB, an initially massive atmosphere (5-times present-day<br />
mass) is required. Our results indicate that a very efficient conversion mechanism should<br />
have occurred during the accretion and shortly after to produce such a massive N2<br />
atmosphere.<br />
During accretion the impact heating may have been strong enough to melt the superficial<br />
icy layer and form an ocean, which volatile species outgassed and form a primitive<br />
atmosphere (Monteux et al., in prep). We are currently developing a new numerical model<br />
of a liquid-vapor equilibrium for various initial oceanic composition to investigate how a<br />
massive atmosphere may be generated during the satellite growth and how it may then<br />
evolve toward a composition dominated by N2. More generally, our model may address<br />
how atmosphere may be generated in water-rich objects, which may be common around<br />
other stars.<br />
Simulating the atmospheric circulation of Venus!<br />
Joao Mendonca — University of Bern!<br />
Venus is the most Earth-like astronomical object in terms of size, mass and orbital<br />
properties in our Solar system. Despite these similarities, Venus is slowly rotating in the<br />
opposite direction, has the most massive atmosphere of the terrestrial planets and is<br />
covered by an opaque and highly reflective cloud layer. These differences are important to<br />
drive the Venus atmospheric circulation to a very distinct regime from Earth's, with strong<br />
atmospheric super-rotation and a variety of other atmospheric dynamic features such as<br />
the observed large-scale wave patterns, which are not well understood.<br />
I will summarise the main efforts of the last three decades to simulate the Venus<br />
atmospheric circulation using general circulation models, and the most likely mechanisms<br />
driving the atmosphere to the actual observed circulation. Recently in Lebonnois et al.<br />
2011, it was shown that Venus general circulation models that use simplified<br />
representations of heating, cooling and friction processes, obtained very distinct results,<br />
which raised concerns about the intrinsic numerical errors and assumptions in the routines<br />
that solve the dynamical behaviour of the flow. These problems and the latest results by<br />
modern models, which use more physically-based parameterizations (Lebonnois et al.<br />
2010 & Mendonca 2013) will be discussed and compared. In our new model (Mendonca<br />
2013), the Venus atmospheric circulation in the cloud region is well represented.<br />
Additionally, the results are sensitive to some radiative properties near the surface and<br />
also to the amount of clouds. Despite the progress, there are still modelling difficulties<br />
which I will address in this work. I will also analyse and describe the main implications that<br />
the Venus climate modelling has in the exploration of exo-climes.<br />
Transmission spectra of Jupiter from Ganymede during eclipses!<br />
Pilar Montañès-Rodrìguez — Instituto de Astrofìsica de Canarias !<br />
Transit spectroscopy data from several hot Jupiter planets are already being collected from<br />
several space and ground-based instruments. And more temperate Jupiter-like planets are<br />
expected to be characterized in the near future. In this framework, an investigation of the<br />
spectral features of Jupiter, in transmission, as if it were observed from a distant star, can<br />
greatly contribute to the modeling efforts of such planetary atmospheres. Here, we present<br />
observations of the near-infrared transmission spectrum of Jupiter with LIRIS at the WHT,<br />
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as reflected from Ganymede's surface during an eclipse. When Ganymede is in the umbra<br />
of Jupiter, only sunlight that has traversed the Jupiter atmosphere is illuminating its<br />
surface. By taking observations of Ganymede before and during an eclipse, we are able to<br />
retrieve Jupiter's atmospheric fingerprints.<br />
Disk-integrated reflection light curves of planets!<br />
Antonio Garcìa Muñoz — ESA-RSSD, ESTEC<br />
The light scattered by a planet atmosphere contains valuable information on the planet’s<br />
composition and aerosol content. Typically, the interpretation of that information requires<br />
elaborate radiative transport models accounting for the absorption and scattering<br />
processes undergone by the star photons on their passage through the atmosphere. I<br />
have been working on a particular family of algorithms based on Backward Monte Carlo<br />
(BMC) integration for solving the multiple-scattering problem in atmospheric media. BMC<br />
algorithms simulate statistically the photon trajectories in the reverse order that they<br />
actually occur, i.e. they trace the photons from the detector through the atmospheric<br />
medium and onwards to the illumination source following probability laws dictated by the<br />
medium’s optical properties. BMC algorithms are versatile, as they can handle diverse<br />
viewing and illumination geometries, and can readily accommodate various physical<br />
phenomena. As will be shown, BMC algorithms are very well suited for the prediction of<br />
magnitudes integrated over a planet’s disk (whether uniform or not). Disk-integrated<br />
magnitudes are relevant in the current context of exploration of extrasolar planets because<br />
spatial resolution of these objects will not be technologically feasible in the near future. I<br />
have been working on various predictions for the disk-integrated properties of planets that<br />
demonstrate the capacities of the BMC algorithm. These cases include the variability of<br />
the Earth’s integrated signal caused by diurnal and seasonal changes in the surface<br />
reflectance and cloudiness, or by sporadic injection of large amounts of volcanic particles<br />
into the atmosphere. Since the implemented BMC algorithm includes a polarization mode,<br />
these examples also serve to illustrate the potential of polarimetry in the characterization<br />
of both Solar System and extrasolar planets. The work is complemented with the analysis<br />
of disk-integrated photometric observations of Earth and Venus drawn from various<br />
sources.<br />
Comparative global energy budgets for the climates of terrestrial and gas giant<br />
planets<br />
Peter Read — University of Oxford<br />
The weather and climate on Earth are generally determined by the amount and distribution<br />
of incoming solar radiation. This must be balanced in equilibrium by the emission of<br />
thermal radiation from the surface and atmosphere, but the precise routes by which<br />
incoming energy is transferred from the surface, through the atmosphere and back out to<br />
space are important features that characterize the current climate. This has been analysed<br />
by several groups over the years, based on combinations of numerical model simulations<br />
and direct observations of the Earth’s climate system. The results are often presented in<br />
schematic form (Trenberth et al. 2009) to show the main routes for the transfer of energy<br />
into, out of and within the climate system. Although relatively simple in concept, such<br />
diagrams convey a great deal of information about the climate system in a compact form,<br />
and are especially valuable pedagogically at school and undergraduate level.<br />
Such an approach has not so far been adopted in any systematic way for other planets of<br />
the Solar System, let alone beyond, although quite detailed climate models of several<br />
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planets are now available, constrained by many new observations and measurements.<br />
Here we analyse the global transfers of energy within the climate systems of a range of<br />
terrestrial planetary bodies within the Solar System, including Mars, Titan and Venus, as<br />
simulated by relatively comprehensive numerical circulation models. These results will<br />
then be presented in schematic form for comparison with the “classical” global energy<br />
budget analysis of Trenberth et al. for the Earth, highlighting the important similarities and<br />
differences. We also consider how to extend this approach towards other Solar System<br />
and extra-solar planets, including Jupiter, Saturn and hot Jupiter exoplanets.<br />
A ~0.1 bar Rule for Tropopause Temperature Minima in Thick Atmospheres of<br />
Planets and Large Moons<br />
Tyler Robinson — University of Washington<br />
Tropopause temperature minima are fundamental for understanding planetary atmospheric<br />
structure. Inversions in the stratospheres of Earth, Jupiter, Saturn, Titan, Uranus, and<br />
Neptune lead to temperature minima that, remarkably, all occur near 0.1 bar, despite very<br />
different insolation, atmospheric composition, gravity, and internal heat flux. We have<br />
explored this common 0.1 bar tropopause using an analytic 1-D radiative-convective<br />
model. We find that tropopause temperature minima always lie in the radiative regime,<br />
above the radiative-convective boundary. Thus, the shared 0.1 bar tropopause arises from<br />
the common physics of radiative transfer. Model fits to solar system worlds show that the<br />
gray infrared optical depth where the tropopause minimum occurs is ~0.1. Furthermore,<br />
the gray infrared optical depths at a pressure of 1 bar are typically of order a few. These,<br />
along with a commonly used power-law scaling between pressure and optical depth, set<br />
the tropopause pressure at ~0.1 bar. Moving beyond the solar system, we show that the<br />
typical gray infrared optical depth of the tropopause minimum is ~0.1 for a wide range of<br />
plausible atmospheric compositions. This optical depth marks the transition into an upper<br />
region of an atmosphere that is very transparent to thermal radiation. Here, shortwave<br />
absorption can dominate the temperature profile and, thus, create an inversion and<br />
corresponding temperature minimum. These findings imply that the common 0.1 bar<br />
tropopause levels seen in the solar system atmospheres are more universal. Thus, we<br />
hypothesize that many exoplanets will possess a 0.1 bar tropopause temperature<br />
minimum.<br />
Measurement of the atmospheres of Europa, Ganymede, and Callisto<br />
Peter Wurz — Physics Institute, University of Bern!<br />
The regular Jovian satellites are believed to be formed at the end of Jupiter's formation<br />
epoch, from the collisional accretion of solids originating in the Solar Nebula, and captured<br />
in a disk orbiting around the planet. The solids taking part to the formation of the satellites<br />
therefore originate from the initial protoplanetary disk, and have probably experienced<br />
lower temperature and pressure conditions as has the material incorporated in Jupiter, and<br />
their chemical composition has been probably less altered. By measuring the composition<br />
of the Jovian satellites, it is therefore possible to set constraints on the chemical<br />
composition of building blocks of planets and satellites, and ultimately on the<br />
thermodynamical conditions in the Solar Nebula.<br />
The Particle Environment Package (PEP) suite has been selected for the JUICE mission<br />
of ESA, which contains instruments for the comprehensive measurements of electrons,<br />
ions and neutrals. One of the instruments is the Neutral and Ion Mass spectrometer<br />
instrument (NIM). NIM is a time-of-flight neutral gas and thermal ion mass spectrometer<br />
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optimised for exospheric investigations. NIM will measure the composition of the<br />
exospheres of Europa, Ganymede, and Callisto. Various physical processes are acting on<br />
the surfaces of Jupiter’s icy moons to promote material from the surface into the<br />
exosphere. These are thermal desorption (sublimation), photon stimulated desorption, ioninduced<br />
sputtering, and micro-meteorite impact vaporisation, with sputtering being the<br />
most important surface release process. Sputtering releases all species present on the<br />
surface more or less stoichiometrically into the exosphere, allowing deriving the chemical<br />
composition of the surface from these measurements. However, the chemical composition<br />
of the surface is modified by the bombardment of energetic electrons and ions, and<br />
ultraviolet radiation, which has to be accounted for in the chemical analysis.<br />
High-resolution and high-SNR transmission spectrum of Earth’s atmosphere<br />
obtained from a lunar eclipse!<br />
Fei Yan — European Southern Observatory & National Astronomical Observatories,<br />
Chinese Academy of Sciences!<br />
With the rapid developments in the exoplanet field, more and more terrestrial exoplanets<br />
are being detected. Characterising their atmospheres using transit observations will<br />
become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric<br />
transmission spectrum of our Earth will be an ideal template for comparison with future<br />
exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to<br />
that of an exoplanet transit, we have obtained a high resolution and high signal-to-noise<br />
ratio transmission spectrum of the Earth’s atmosphere.<br />
We will present the transmission spectrum together with our 1-D atmospheric spectral<br />
model. From the model-fit, the column densities of the various atmospheric species are<br />
calculated. Some intersting results from this work are discussed, such as the forwardscattered<br />
sunlight, the oxygen isotopes, the souces of NO2.<br />
Extreme Planetary Classes in Our Own Solar System: The Atmospheric Circulation<br />
of Pluto and Triton!<br />
Angela Zalucha — SETI Institute!<br />
Pluto and Triton (Neptune's largest moon) are often called “sister worlds” due to their<br />
nearly identical atmospheric composition, size, and temperature. While the bulk<br />
temperature and composition have been constrained by ground-based stellar occultation<br />
observations and the Voyager 2 flyby of Neptune, the circulation patterns at all scales are<br />
still not known due to the difficulty in observing wind remotely. Pluto and Triton, or “ice<br />
dwarfs”, are quite unusual compared with other known planetary bodies, in that efficient<br />
methane absorption in the atmosphere creates at strong temperature inversion<br />
(temperature increasing with height) near the surface that has been dubbed the<br />
stratosphere. Such a configuration is extremely stable and prevents vertical motion, which<br />
impacts flow in the other directions as well (for example, Hadley cells, ubiquitous on<br />
terrestrial planets and perhaps super-Earths, are not expected to exist). Moreover, much<br />
like Mars, it is thought that these sister worlds have a volatile cycle where the main<br />
atmospheric constituent (here molecular nitrogen) condenses and sublimates throughout<br />
the year, even to the point of atmospheric collapse.<br />
Within the past few years, there has been a surge of interest in Pluto's global circulation<br />
patterns. This problem has posed a challenge unprecedented from other planetary bodies.<br />
First, Pluto's year is about 250 Earth years, requiring long simulation times.Second, Pluto's<br />
atmosphere and surface are thought to be strongly coupled radiatively, requiring both a<br />
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sophisticated atmosphere and surface model. The properties (emissivity, configuration of<br />
ices, thermal inertia, and total surface ice inventory) of Pluto's surface are not well<br />
constrained. Various groups have used different general circulation models (GCMs) to<br />
predict the atmospheric circulation of Pluto. I will discuss results from the MIT Pluto GCM,<br />
which after several years of atmosphere-only studies (e.g. Zalucha and Michaels 2013) is<br />
now coupled to a sophisticated surface model.<br />
TERRESTRIAL PLANETS<br />
Maximum planet size for habitability<br />
Yann Alibert! — University of Bern<br />
The conditions that a planet must fulfill in order to be habitable are not precisely known.<br />
However, it is comparatively easier to define conditions under which a planet is very likely<br />
not habitable. Finding such conditions is moreover important as it can help to select, in an<br />
ensemble of potentially observable planets, which ones should be observed in more<br />
details for characterization studies. Assuming, as in the case of the Earth, that the<br />
presence of a C-cycle is a necessary condition for long-term habitability, we derive, as a<br />
function of the planetary mass, a radius above which a planet is likely not habitable. For<br />
this, we compute the maximum radius a planet can have in order to fulfill two constraints:<br />
surface conditions compatible with the existence of liquid water, and no ice layer at the<br />
bottom of a putative global ocean. We demonstrate that, above a given radius, these two<br />
constraints cannot be met. For this, we compute internal structure models of planets, using<br />
a 5-layer model (core, inner mantle, outer mantle, ocean and atmosphere), for different<br />
masses and composition of the planets (in particular Fe/Si ratio of the planet). Our results<br />
show that for planets in the Super-Earth mass range (1-12 Mearth), the overall maximum<br />
size that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when<br />
considering planets with higher Fe/Si ratios, and taking into account irradiation when<br />
computing the gas envelope structure.<br />
Remote detection of biosignatures on Earth-like planets<br />
Svetlana Berdyugina — KIS, Freiburg<br />
Life on Earth is aware of light polarization and makes good use of it for its survival and<br />
growth. In all cases, it is the solar light that is reflected, processed and analyzed by life<br />
forms, and the same circumstances are expected to exist on all habitable planets.<br />
Photosynthesis, in particular, is very likely to arise on another planet and can produce<br />
conspicuous biosignatures. Recently, it was demonstrated that polarized reflected light can<br />
be detected from exoplanetary atmospheres. We focus now on identifying biological<br />
polarization effects, e.g., selective light absorption or scattering by biogenic molecules.<br />
This helps to enhance the reliability of other biomarkers for distant detection of life which<br />
can be contaminated by non-biological sources. Here we present a laboratory study of<br />
reflected light polarization from various terrestrial plants and non-biological samples (rocks<br />
and sands). We use these measured reflection spectra to synthesize polarized spectra of<br />
Earth-like planets with various contributions from the land, photosynthetic organisms,<br />
ocean, atmosphere, and clouds. We estimate the required photometric and polarimetric<br />
sensitivity to detect such planets in habitable zones of nearby stars.<br />
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Weather on strange new worlds: Large scale atmospheric dynamics on tidally<br />
locked terrestrial planets around an M dwarf star<br />
Ludmila Carone — KU Leuven, Center for mathematical Plasma-astrophysics<br />
!<br />
It is likely that the first habitable extrasolar planet with an atmosphere will be discovered<br />
around an M star. Indeed, several terrestrial planets have already been discovered around<br />
such stars. These planets will probably be tidally locked. Therefore, the climate dynamics<br />
of a terrestrial exoplanet — even in the habitable zone — might be very different from the<br />
Earth. Firstly, the rotation will be slower and we would therefore not expect mid-latidude<br />
cyclones but rather a barotropic atmosphere. Secondly, the temperature varies rather with<br />
longitude than with latitude leading to circulation between the dark and cold hemisphere.<br />
Because there are many unknowns with exoplanets, in particular with terrestrial<br />
exoplanets, we decided to explore the dynamics of a greenhouse atmosphere on a tidally<br />
locked planet with a medium-size parameter study. We used an idealized global threedimensional<br />
dry circulation model (GCM) with an idealized forcing, adopting MITgcm<br />
(http://mitgcm.org). As a first step, different day-night temperature differences, rotation<br />
periods, time scales for radiation and surface friction, and surface pressures were<br />
investigated. The emerging large scale dynamics of the atmosphere was compared with<br />
previous studies and with observations and models of Venus and Titan; the latter being the<br />
closest analogues in the Solar System. Our goal is to identify, on the one hand, features<br />
that are robust against parameter change — like superrotation and Hadley-like circulation<br />
cells — and, on the other hand, to investigate climate patterns that vary strongly with<br />
different assumptions: like the surface wind and temperature, and large scale vortices.<br />
This not only broadens our understanding about the different mechanisms at play in<br />
atmospheres, but may also lead to a better coupling between observations of transiting<br />
terrestrial exoplanets and atmospheric models.<br />
The Prospects for Characterizing the Atmospheres of Rocky Exoplanets!<br />
David!Charbonneau — Harvard University!<br />
The coming decade brings the promise of direct spectroscopic characterization of the<br />
atmospheres of rocky planets orbiting other nearby stars. The most accessible planets will<br />
be those that orbit M-dwarfs, owing to the diminutive stature, low-luminosities, and<br />
preponderance of these stars. This talk will present a quantitative evaluation of the<br />
prospects for this path informed by the most recent data: I will begin by presenting an<br />
analysis of the complete Kepler dataset to determine the rate of occurrence of such<br />
planets. I will combine this with the catalog of nearby stars to evaluate the likely distance<br />
to the closest transiting systems, and the likely characteristics of the stellar host. I will then<br />
address the sensitivity of the NASA TESS Mission, the MEarth transit survey, and other<br />
ongoing projects to detect such objects. I will conclude by presenting the likely signal-tonoise,<br />
resolution, and wavelength coverage that should be delivered by the James Webb<br />
Space Telescope, the Giant Magellan telescope, and other large ground-based<br />
telescopes. Using the technique of transmission spectroscopy, some of these telescopes<br />
should be able to investigate such planetary atmospheres beginning as early as 2018,<br />
provided the community has identified the targets. The goal of this presentation will be to<br />
leave the audience with a quantitative understanding of what we can, and cannot, hope to<br />
measure in this time frame, and thus to assist them in directing their research efforts<br />
accordingly.<br />
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Exoplanetary Extreme Space Weather<br />
Ofer Cohen — Harvard-Smithsonian CfA!<br />
Exoplanetary research is driven by the ultimate goal of defining whether life can exist<br />
beyond the Earth and the solar system, while recent searches for exoplanets are focused<br />
increasingly on detecting rocky, Earth-like planets around M-dwarf stars, which are by far<br />
the most numerous type of star in the Universe. The “planet habitability” problem is a<br />
cross-disciplinary topic where commonly, a planet is defined as habitable if its surface<br />
temperature allows water to exist in a liquid form. However, there are other factors that can<br />
impact planet habitability. M-dwarf stars are very active magnetically and their X-ray and<br />
ultraviolet radiation in their habitable zones is much higher than we experience near the<br />
Earth.<br />
The physics of the solar atmosphere, the interplanetary environment, and the upper<br />
atmospheres of planets in the solar system, including the Earth, is governed by the<br />
radiation environment, electromagnetic forces, and the interaction between charged<br />
particles and magnetic fields. In particular, the atmosphere of the Earth is shielded from<br />
the intense radiation in space and from the solar wind by the Earth’s intrinsic magnetic<br />
field. Here we present a set of numerical models, which were developed to study solar<br />
system objects, and their application to exoplanetary, M-dwarf systems. These models<br />
include detailed physical processes that are known to be important for solar system<br />
bodies, but are commonly neglected in the context of exoplanets. Specifically, we<br />
investigate the role of the planetary magnetic field in shielding the planetary atmosphere<br />
from erosion by the extreme space environment in which it resides. Our study estimates<br />
what planetary field strengths are necessary for protection from the caustic space<br />
environment of M-dwarfs, and demonstrates how coronal mass ejections from M-dwarfs<br />
affects the planet’s magnetospheres, and how much atmosphere is likely to be stripped<br />
away in the larger events.<br />
Defining Habitable Zones in Gravitationally Interacting Systems!<br />
Siegfried Eggl — IMCCE Observatoire de Paris!<br />
Calculating the extent of liquid-water habitable zones around main sequence stars<br />
becomes challenging for systems with more than two gravitationally interacting bodies,<br />
since the evolution of planetary orbits has to be taken into account. Given the recent<br />
progress in determining liquid-water habitable zones within binary star systems we present<br />
a generalized methodology to identify habitable-zone boundaries in multistar and<br />
multiplanet systems.<br />
Planning follow-up Space Missions searching for Atmospheric Spectral<br />
Biosignatures from a sample of potentially habitable Earth-like Exoplanets!<br />
John Lee Grenfell — Planetary Research Inst. DLR Berlin!<br />
Next generation missions which aim at the atmospheric characterization of rocky<br />
extrasolar planets could provide initial information on the amounts of carbon dioxide and<br />
water molecules in the atmospheres of hot to temperate Super-Earths. Follow-up studies<br />
may be needed however to search for (likely weaker) atmospheric biosignature signals<br />
from a sample of Super-Earths. Until now, most studies have focused on the effects of<br />
atmospheric carbon dioxide and water upon planetary climate, hence (potential)<br />
habitability. There is, however, potentially additional information held in such data. On<br />
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Earth, atmospheric carbon dioxide is strongly affected by life itself (e.g. vegetation<br />
enhances weathering) so that on a “dead Earth” the atmospheric carbon dioxide would be<br />
significantly higher than on its living counterpart. This could represent an additional<br />
selection procedure for follow-up studies searching for biosignatures from a sample of<br />
habitable planets. A difficult challenge when applying such a technique is to constrain<br />
abiotic processes affecting atmospheric carbon dioxide e.g. hydrology, geochemistry and<br />
outgassing. Life itself may also regulate the carbon-silicate cycle, hence stabilize climate,<br />
but the extent and means of this process if it exists are not well known. Forty years ago a<br />
cluster of studies focused on “live” and “dead” Earths in the context of the Gaia hypothesis<br />
and the effect on the carbon cycle. There is now a need to revisit this work with newgeneration<br />
models but with a focus on exoplanetary habitability. In this work we discuss<br />
possible selection procedures for follow-up studies which search for biosignatures given a<br />
sample of rocky Super-Earths with known atmospheric carbon dioxide and water<br />
abundances. We apply a radiative column model to calculate consistent CO2 and H2O<br />
abundances for dead Earth scenarios.<br />
The role of ocean heat transport in climates of tidally locked exoplanets around M-<br />
dwarf Stars<br />
Yongyun Hu! — Peking University!<br />
The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar<br />
radiation between the dayside and nightside. Previous work has focused on the role of<br />
atmospheric heat transport in preventing atmospheric collapse on the nightside for<br />
terrestrial exoplanets in the habitable zone around M-dwarfs. In the present paper, we<br />
carry out the first simulation with a fully coupled atmosphere-ocean general circulation<br />
model (AOGCM) to investigate the role of ocean heat transport in climate states of tidally<br />
locked habitable exoplanets around M-dwarfs. Our simulation results demonstrate that<br />
ocean heat transport substantially extends the area of open water along the equator,<br />
showing a lobster-like spatial pattern of open water, instead of an “eyeball”. For sufficiently<br />
high-level greenhouse gases or strong stellar radiation, ocean heat transport can even<br />
lead to complete deglaciation of the nightside. Our simulations also suggest that ocean<br />
heat transport likely narrows the width of M-dwarfs’ habitable zone. This study provides the<br />
first demonstration of the importance of exo-oceanography in determining climate states<br />
and habitability of exoplanets.<br />
Updates to the SPARC/MITgcm: Modeling the atmospheric circulation of terrestrial<br />
exoplanets!<br />
Tiffany Kataria — University of Arizona<br />
As the detection and characterization of exoplanets moves toward smaller planets in the<br />
super-Earth and terrestrial regimes, atmospheric circulation modeling continues to play an<br />
important role in helping to understand ground-and space-based observations of their<br />
atmospheres. These models must range from planets with thick atmospheric envelopes<br />
and no surface (for super Earths) to planets with thinner atmospheres and rocky surfaces<br />
(for terrestrial exoplanets). To that end, we present a summary of terrestrial planet updates<br />
to our model, the Substellar and Planetary Atmospheric Radiation and Circulation<br />
(SPARC) model, which couples the MIT General Circulation Model with a two-stream, nongrey<br />
implementation of the multi-stream, non-grey radiative transfer code developed by<br />
Marley and McKay (1999). These updates include an implementation of moist and dry<br />
convective schemes, a boundary layer scheme, and a surface energy balance which self-<br />
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consistently calculates the ground temperature. We present early results from studies<br />
looking at the role of clouds on the dynamics and habitability of terrestrial exoplanets<br />
orbiting M-dwarfs. Using these models, we will identify fundamental dynamical<br />
mechanisms that drive their atmospheres and constrain their thermal structures, which will<br />
inform future observations of transiting terrestrial exoplanets, particularly at secondary<br />
eclipse.<br />
Modeling of Habitable Planets - the Underlying Atmospheric Dynamics<br />
Cevahir Kilic! — University of Bern!<br />
Instrumentation to detect new planets develops continually and enabled the scientific<br />
community to characterize exoplanets in terms of physical parameters, such as size and<br />
mass, as well as identify possible atmospheres. Furthermore, the CHEOPS satellite<br />
program will provide the possibility for an improved characterization also in terms of<br />
habitability of exoplanets. The increasing number of newly detected planets raises issues<br />
of possible other habitable worlds.<br />
To investigate the atmospheric dynamics of habitable planets, we use a hierarchy of<br />
general circulation models (GCMs). In a first step, we carry out these simulations using a<br />
three-dimensional atmospheric GCM of intermediate complexity, the so-called Planet<br />
Simulator.<br />
For this study, sensitivity simulations varying different basic parameters of the planet are<br />
performed to explore the range of habitability. Each simulation is carried out over 30 model<br />
years. In doing so, we have modified gravity, radius, sidereal day, atmospheric<br />
composition, distance to the star, and obliquity of the ecliptic. These simulations uses an<br />
Earth-like environment (e.g., Earth land mask), which allows us to compare our<br />
investigations with Earth observations. The range of surface temperatures determines the<br />
habitability of a planet. Our simulations show, inter alia, that an increase in radius leads to<br />
a reduction of the global mean temperature. We also find an impact on the amplitude of<br />
the seasonality given by the gravity of the planet. The difference between maximum and<br />
minimum temperature is enhanced with increasing gravity. Additionally, the variation of the<br />
gravity changes the atmospheric structure: an increased gravity leads to a more stable<br />
atmosphere above 700 hPa and to generally stronger wind fields and lower surface<br />
temperatures on the planet. Furthermore, basic dynamical features such as the number of<br />
jet streams will be assessed in the sensitivity simulations. The next steps also include a<br />
model adaption with different land masks (e.g., aqua-planet).<br />
A new perspective on the inner edge of the habitable zone: 3D modeling of runaway<br />
greenhouse processes on Earth like planets<br />
Jeremy Leconte — LMD (Paris) / CITA (Toronto)<br />
Because current exoplanets detection methods are biased toward shorter-period orbits,<br />
most planets discovered to date have a higher equilibrium temperature than the Earth. If<br />
water is available at the surface, the amount of water vapor is expected to increase as the<br />
planet warms, enhancing, in turn, the atmospheric greenhouse effect.<br />
It has been shown that, above a certain critical insolation, this destabilizing greenhouse<br />
feedback can "runaway" until all the oceans are evaporated. It has also been suggested<br />
that warming may sufficiently increase stratospheric humidity to cause oceans to escape<br />
to space before the runaway greenhouse occurs. However, the value of the critical<br />
insolations triggering these processes remain uncertain because they have so far been<br />
evaluated with unidimensional models that cannot account for dynamical effects and cloud<br />
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feedback that are key stabilizing features of planetary climates. Understanding and<br />
modeling these processes is thus critical to accurately determine the extent of the<br />
"Habitable Zone" around other stars.<br />
We present results from a 3D global climate model specifically developed to describe hot,<br />
extremely moist atmospheres to quantify Earth like planets climate response to an<br />
increased insolation. In contrast with previous studies, we find that clouds have a<br />
destabilizing feedback on the long term warming. However, subsident, unsaturated regions<br />
created by the Hadley circulation have a stabilizing effect that is strong enough to defer the<br />
runaway greenhouse limit to higher insolation than inferred from 1D models. Because of<br />
these unsaturated regions, the stratosphere remains cold and dry enough to hamper<br />
atmospheric water escape, even at large fluxes.<br />
Finally, we will discus the implications of these results for Venus early water history and<br />
the extent of the habitable zone around low mass stars when the rotation of the planet can<br />
be tidally synchronized.<br />
Terrestrial planet atmospheres in the aftermath of giant impacts!<br />
Roxana Lupu — SETI Institute!<br />
The final assembly of terrestrial planets is now universally thought to have occurred<br />
through a series of giant impacts, such as Earth's own Moon-forming impact. After the<br />
impact the surface of the surviving planet can remain hot for millions of years, making it<br />
potentially detectable by direct imaging surveys. Here we explore the atmospheric<br />
structures and spectral signatures of post-giant-impact terrestrial planets enveloped by<br />
thick atmospheres derived from vaporized rock material. The atmospheric chemistry is<br />
computed self-consistently for compositions reflecting either the bulk silicate Earth (BSE,<br />
including the crust, mantle, atmosphere and oceans) or Earth's continental crust (CC). We<br />
compute atmospheric profiles for surface temperatures ranging from 1000 to 2200 K,<br />
surface pressures of 10 and 100 bar, and surface gravities of 10 and 30 m/s 2 . Our<br />
calculations using extensive line lists bring a significant improvement over previous<br />
models, but still do not include cloud formation and aerosol opacities. We find that the<br />
post-giant-impact atmospheres are dominated by H2O and CO2, while the formation of<br />
CH4, and NH3 is quenched due to short dynamical timescales. Other important<br />
constituents are HF, HCl, NaCl, and SO2. Estimates including photochemistry and vertical<br />
mixing show atmospheric enhancements in sulfur-bearing species, particularly SO2, which<br />
produces strong spectral features. Estimated luminosities for post-impact planets, although<br />
lower than predicted by previous models, show that the hottest post-giant-impact planets<br />
will be detectable with the planned 30 m-class telescopes. Finally, we use the models to<br />
describe the cooling of a post-impact terrestrial planet and briefly investigate its time<br />
evolution. We find that the cooling timescale for post-giant impact Earths ranges between<br />
10 5 and 10 6 years, where the slower cooling is associated with the planet going through a<br />
runaway greenhouse stage.<br />
The impact of stellar winds on exoplanetary magnetospheres<br />
S.C. Marsden — University of Southern Queensland<br />
The habitable zone of an exoplanet is traditionally defined by the range<br />
of orbital distances where planetary surface temperatures are expected to<br />
allow for liquid water. However, given that stellar winds can erode<br />
planetary atmospheres even when a magnetosphere is present, it is proposed<br />
that considerations of planetary habitability include stellar wind<br />
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pressure.The Bcool project is an international collaboration studying the<br />
magnetic fields of solar-type stars and whose results can be used for<br />
stellar wind studies. Using a simple wind model we show that an exoplanet<br />
like the present-day Earth would generally need to orbit outside the<br />
traditional habitable temperature zone of many solar-type stars to<br />
maintain the size of its magnetosphere. However, planets orbiting within<br />
the classical temperature habitable zone of solar-type stars should<br />
possess magnetospheres that although compressed, are likely to protect the<br />
planet's atmosphere and hence allow for the planet to be habitable.<br />
An aqua planet under strong solar forcing!<br />
Max Popp — Max Planck Institute for Meteorology<br />
A modified version of the general circulation model ECHAM6 is used to investigate the<br />
impact of increased total solar irradiance (TSI) on an aqua planet on a present-day Earthlike<br />
orbit. We find that the present-day Earth-like climate destabilizes for a TSI between<br />
1.06 and 1.08 times the present-day Earth value (S0). The aqua planet does not, however,<br />
go into a Runaway Greenhouse, but attains a new steady state with global-mean seasurface<br />
temperatures exceeding 335 K. This warm state is characterized by a low<br />
meridional temperature gradient, a weak meridional circulation without polar cells, a moist<br />
stratosphere and convection-dominated cloud formation. As the TSI is further increased,<br />
the planet remains in the same regime of warm steady states for TSIs of at least up to 1.2<br />
S0, because the cloud albedo increases as well, and balances the increased forcing. In<br />
these states, the volume mixing ratio of water vapor in the upper atmosphere may attain<br />
values as large as 0.015. This large mixing ratio exceeds the “Moist Greenhouse” limit<br />
(Kasting et al. 1993) and suggests that a planet in such a warm state would hence be<br />
subject to a rapid loss of water.<br />
Climate dynamics of a coupled Aquaplanet<br />
Josiane Salameh — Max Planck institute for Meteorology<br />
The idea behind an Aquaplanet, an idealized configuration of the current Earth with all the<br />
landmasses removed, is not recent. However, most of the research is conducted with<br />
stand-alone atmospheric models. Thus, the originality behind considering the coupled<br />
Aquaplanet setup, highlights the ocean's impact and allows us to directly interpret the<br />
fundamental processes and feedbacks between ocean and atmosphere without any land<br />
interference.<br />
As for the few coupled Aquaplanet studies lately conducted on General Circulation<br />
Models (GCM), they showed an extreme disparity regarding the final climate state. The<br />
range of states discovered lies between a warm climate qualified with a lack of sea-ice<br />
formation and a cold climate where sea-ice extend at the poles. Then, the existence of<br />
three equilibrium states was verified while integrating the same GCM from different<br />
random initial conditions.<br />
The climate of a coupled Aquaplanet remains an open question. Therefore, our task is to<br />
analyze the atmospheric-oceanic circulations of a coupled Aquaplanet while contributing to<br />
this discrepancy in previous results. The simulations are executed on “ICON”, based on an<br />
icosahedral triangular grid. Effects of rotation on Hadley cell's magnitude and extent, winds<br />
distribution and others were already theoretically discussed and numerically tested. In<br />
order to achieve a higher physical understanding of the Earth rotation rate and its effect on<br />
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the global circulation features, especially the ocean, our future goal is to consider variable<br />
rotation rates in our coupled Aquaplanet setup.<br />
The Effect of Host Star Spectral Energy Distribution on Planetary Climate<br />
Aomawa Shields — University of Washington!<br />
Planetary climate can be affected by the interaction of the host star spectral energy<br />
distribution with the wavelength-dependent reflectivity of ice and snow. We have explored<br />
this effect with a hierarchy of models. Results from both one-dimensional radiative transfer<br />
and energy balance models and a three-dimensional general circulation model indicate<br />
that terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger icealbedo<br />
feedback. We found that ice extent is much greater on a planet orbiting an F-dwarf<br />
star than on a planet orbiting a G- or M-dwarf star at an equivalent flux distance, assuming<br />
fixed CO2 (present atmospheric level on Earth). The surface ice-albedo feedback effect<br />
becomes less important at the outer edge of the habitable zone for main-sequence stars,<br />
where the maintenance of surface liquid water requires high atmospheric CO2<br />
concentrations. We show that 3-10 bar of CO2 will entirely mask the climatic effect of ice<br />
and snow, leaving the outer limits of the habitable zone unaffected by the spectral<br />
dependence of water ice and snow albedo. However, less CO2 is needed to maintain open<br />
water for a planet orbiting an M-dwarf star than would be the case for hotter mainsequence<br />
stars. We also explore the sensitivity of climate hysteresis to spectral energy<br />
distribution, and examine how changes in planetary rotation rate and atmospheric<br />
composition affect our results.<br />
Marine Boundary Layer Clouds and their Interaction with the Large-scale<br />
Atmospheric Circulation: An Idealized-GCM Study<br />
Zhihong Tan! — California Institute of Technology / ETH Zurich<br />
Cloud feedback is one of the central uncertainties in climate modeling, and the short-wave<br />
radiative feedback of marine boundary layer (MBL) clouds is the most significant<br />
contributor to these uncertainties. We have incorporated a physically motivated eddy<br />
diffusivity/mass flux closure for convective turbulence coupled to a probabilistic cloud<br />
scheme in an idealized aquaplanet GCM to develop improved turbulence and cloud<br />
parameterizations and to study and constrain the physical mechanisms giving rise to cloud<br />
feedbacks. Subtropical MBL clouds are observed in simulations with the idealized GCM.<br />
We study their response to changes in the longwave optical depth and in the ocean heat<br />
flux to determine the sign and magnitude of MBL cloud feedback over a wide range of<br />
climates. We compare our results with previous modeling and observational studies, such<br />
as the reported dependence of the MBL cloud fractions on the lower troposphere stability.<br />
We discuss the mechanisms underlying the MBL cloud feedback and the degree to which<br />
they can be expected to be robust, as well as the interaction of MBL processes with the<br />
large-scale atmospheric circulation.<br />
Climate and Photochemistry of Known Potentially Habitable Exoplanets<br />
Feng Tian — Tsinghua University!<br />
Several potentially habitable planets are known today. What are the environments like on<br />
them Are they inhabited What are the potential signatures of life on them These are<br />
important scientific questions for the coming decade(s). Photochemistry is important for<br />
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the climate on exoplanets by providing important species affecting radiation. On the other<br />
hand, climate may pose important constraints on atmospheric composition, based on<br />
which different schemes of photochemistry can perform. In this work we will discuss the<br />
interplays between exoplanet climate and atmospheric composition and photochemistry,<br />
focusing on potentially habitable exoplanets such as HD40307g and the GJ667C planets.<br />
Water loss from terrestrial planets with N2/CO2 atmospheres!<br />
Robin!Wordsworth! — University of Chicago!<br />
The initial volatile content delivered to terrestrial planets during accretion is most likely<br />
highly variable, with many planets receiving significantly more than Earth today possesses.<br />
Understanding how later processes such as photolysis-driven H2O loss affect planetary<br />
evolution is therefore vital to constraining the range of possibilities for both the early Solar<br />
System and for many recently discovered low-mass exoplanets. Here we discuss a range<br />
of calculations we have performed to study the dependence of water loss rates on a wide<br />
range of planetary parameters. We show through a combination of simple analysis and<br />
numerical climate models (1D and 3D) that the non-condensing atmospheric component<br />
plays a fundamental role in controlling water loss via regulation of the stratospheric cold<br />
trap. While CO2 can increase H2O transport to the high atmosphere over a small range of<br />
mixing ratios by increasing surface temperature, thermodynamic constraints and cooling of<br />
the middle/upper atmosphere act as a bottleneck on escape in other circumstances. The<br />
differing relationships of total stellar luminosity and stellar XUV with time for G-stars places<br />
strong limits on H2O loss rates for planets like Earth, although escape can reach higher<br />
values for planets with surface liquid water around M-stars. Because the carbon cycles of<br />
planets with ocean-covered surfaces are likely to be fundamentally different from that of<br />
Earth, our results have important implications for the likely surface and atmospheric<br />
characteristics of super-Earth exoplanets in the habitable zone.<br />
Oceanic Circulation of Tidally Locked Terrestrial Planets!<br />
Jun Yang — University of Chicago!<br />
A fully coupled oceanic-atmospheric general circulation model is modified to simulate the<br />
climate of tidally locked terrestrial planets. A central issue to be examined is to identify the<br />
determining factors of oceanic circulation and its associated heat transport in both zonal<br />
and meridional directions. In this study we will examine five planetary parameters: ocean<br />
depth, land-sea distribution, rotational period (equaling to orbital period), planetary radius,<br />
and gravity.<br />
All these simulations show an eastward current along the equator, transporting heat from<br />
dayside to nightside, and a meridional overturning circulation (MOC) in each hemisphere,<br />
transporting heat from tropics to high latitudes. The equatorial current is driven by the<br />
combined effect of surface wind streeses and Rossby waves in the ocean which transport<br />
eastward momentum from high latitudes to the equator. The MOC is driven by salinity and/<br />
or temperature contrasts between low and high latitudes. The salinity contrast results from<br />
sea ice formation at high latitudes which releases salt to the ocean, and from sea ice<br />
melting at low-latitude ice margins which decreases the salinity there. The strengths of the<br />
oceanic circulation and heat transport are signifcantly influenced by the five planetary<br />
parameters. We will further present how these parameters work.<br />
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Towards the Minimum Inner Edge Distance of the Habitable Zone<br />
Andras Zsom — Massachusetts Institute of Technology!<br />
We explore the minimum distance from a host star where an exoplanet could potentially be<br />
habitable in order not to discard close-in rocky exoplanets for follow-up observations. We<br />
find that the inner edge of the Habitable Zone for hot desert worlds can be as close as<br />
0.38 AU around a solar-like star, if the greenhouse effect is reduced (low relative humidity),<br />
and the surface albedo is increased.<br />
We consider a wide range of atmospheric and planetary parameters such as surface<br />
pressure, relative humidity, CO2 mixing ratio, surface gravity, etc. We argue that if the<br />
dominant mode of precipitation is rain, the potentially habitable region is maximized on the<br />
dry planet. Based on this argument, we estimate that relative humidity levels of 1% or<br />
more can be sufficient to maintain a liquid water cycle. If the surface pressure is too low<br />
(~0.1 bar), the water loss timescale of the planet is too short to support life. If the surface<br />
pressure is too high (~100 bars), we show using atmospheric circulation arguments, that<br />
the day-night side temperature difference on slow rotators is too small to enable an active<br />
water cycle. Intermediate surface pressures (~1-10 bars) can provide suitable conditions<br />
for a water cycle independent of the planetary rotation period. We additionally find that the<br />
water loss timescale is influenced by the atmospheric CO2 level, because it indirectly<br />
influences the stratospheric water mixing ratio.<br />
We also show that the expected transmission spectra of hot desert worlds are similar to<br />
an Earth-like planet. Therefore, an instrument designed to identify biosignature gases in an<br />
Earth-like atmosphere can also identify similarly abundant gases in the atmospheres of dry<br />
planets.<br />
SUPER-EARTHS AND HOT NEPTUNES<br />
The Atmospheres of GJ1214b and GJ436b: A Comprehensive Retrieval Study Based<br />
on Unprecedented Data from Two Large-Scale HST Campaigns<br />
Bjørn! Benneke — California Institute of Technology!<br />
In this talk, we present the scientific interpretation for two unprecedented HST WFC3<br />
campaigns to observe the transmission spectra of the warm exo-Neptune GJ436b and the<br />
warm super-Earth GJ1214b. We report statistically robust constraints on the atmospheric<br />
gas composition as well as the cloud properties such as cloud composition, cloud top<br />
altitude, and particle size distribution.<br />
Our main result for GJ1214b is that the observations require the presence of high-altitude<br />
clouds at high significance, independent of the atmospheric composition and mean<br />
molecular mass. We investigate the full range of physically plausible cloud properties that<br />
may explain the observations. For GJ436b we find that high-altitude clouds could similarly<br />
explain the observed flat transmission spectrum, suggesting that a similar cloud formation<br />
mechanism may be at play in the two planets. Alternatively, we suggest the intriguing<br />
possibility that GJ436b hosts an atmosphere which is strongly metal-enriched compared to<br />
the gas and ice giants in our solar system.<br />
The atmospheric constraints are obtained using a novel self-consistent inversion<br />
framework that combines the observational data with our prior understanding of<br />
atmospheric physics and chemistry in a statistically robust manner. The new framework<br />
makes full use of all information at hand and identifies the full range of scenarios that are<br />
both physically plausible and in agreement with the data. We describe the merits of this<br />
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new inversion framework for the interpretation of atmospheric spectra of both exoplanets<br />
and Solar System planets.<br />
How Do Mini-Neptunes Migrate<br />
Zachory Berta-Thompson — Massachusetts Institute of Technology!<br />
To understand an exoplanet, we need to know how it got where it is today. Because it<br />
transits a very nearby, very small star, the exoplanet GJ1214b is a useful laboratory for<br />
studying the physics of planets near the fuzzy boundary between super-Earths and sub-<br />
Neptunes. However, little is known about how GJ1214b migrated to its current close-in<br />
orbit. Was it scattered wildly inward and later tidally circularized, as many hot Jupiters<br />
appear to have been Or was it coaxed in smoothly and gently, as seems to be the case<br />
for the compact, coplanar, small-planet systems uncovered by Kepler To address this<br />
conundrum, we search for and analyze recurrent starspot occultations in closely-spaced<br />
transit light curves of GJ1214b taken with the Magellan, Gemini, and Hubble telescopes.<br />
We use these spot occultations to constrain the relative orientation of the planet’s orbit to<br />
the host star’s spin axis, which can be used to distinguish among possible scenarios for<br />
the migration history of the planet. This analysis bears not only on the one particularly<br />
useful GJ1214b system, but also on the processes that may shape many of the abundant<br />
close-in, low-mass, low-density exoplanets that populate our Galaxy.<br />
Water Cycling between Ocean and Mantle: Super-Earths need not be Waterworlds<br />
Nicolas Cowan — Northwestern University<br />
Large terrestrial planets are expected to have muted topography and deep oceans,<br />
implying they should be entirely covered in water, so-called waterworlds. Quantitatively, a<br />
planet ten times the mass of Earth is not expected to have exposed continents unless it<br />
has a water mass fraction less than 3x10^-5, roughly ten times drier than Earth.<br />
Waterworld climate is predicted to be less stable than that of planets with exposed<br />
continents. Water is partitioned, however, between a surface reservoir, the ocean, and an<br />
interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on<br />
geological timescales. Degassing of melt at mid-ocean ridges and serpentinization of<br />
oceanic crust are mediated by sea-floor pressure, providing a stabilizing feedback on longterm<br />
ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we<br />
develop a two-box model of the hydrosphere and derive steady-state solutions to the<br />
water-partitioning on terrestrial planets. Since hydrostatic pressure is proportional to<br />
gravity, super-Earths with a deep water cycle will tend to store most of their water in the<br />
mantle. We conclude that tectonically active terrestrial planets with H2O mass fractions<br />
less than 3x10 -3 will have both oceans and exposed continents.<br />
Transiting planets around nearby M dwarfs: updates from the APACHE Project<br />
Mario! Damasso — University of Padova<br />
Across the Alps, just few hundreds km from Davos as the crow flies, a search for<br />
transiting, small-size planets orbiting M dwarfs is in progress since July 2012: the APACHE<br />
Project (A PAthway toward the Characterization of Habitable Earths). APACHE is a survey<br />
“made in Italy” carried out as a collaboration between the Astronomical Observatory of the<br />
Autonomous Region of Aosta Valley and INAF-Torino Astrophysical Observatory, which will<br />
last five years and collect a huge database of photometric data. It uses five identical,<br />
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automatic 400mm telescopes to observe thousands of carefully selected nearby red<br />
dwarfs. Nearby, bright M dwarfs are optimal targets as host stars for transiting planets<br />
which can be extensively followed up to analyze their atmospheres, as demonstrated by<br />
the case of the extrasolar planet GJ 1214b.<br />
We present the results of the first observing season for several dozens of cool stars,<br />
including detailed simulations aimed at estimating the sensitivity of APACHE to transiting<br />
planets of different sizes. Moreover, we will discuss the results obtained for a sample of<br />
stars which have been also monitored spectroscopically with HARPS-N@TNG in the<br />
framework of the Large National Program GAPS.<br />
In the spotlight: small planets transiting bright stars!<br />
Diana!Dragomir — UC Santa Barbara/Las Cumbres Observatory Global Telescope<br />
The Kepler transit survey has resulted in the discovery of more than a dozen super-Earth<br />
planets. Super-Earths are of particular interest in exoplanet research because they<br />
constitute a class of objects which are not represented in our Solar System, though<br />
statistics from Kepler and radial velocity surveys suggest they are relatively common<br />
around other stars. Moreover, these planets can theoretically have a wide range of<br />
densities and therefore compositions which we have only very recently begun to explore<br />
observationally. While studies of super-Earth hosting systems based on Kepler photometry<br />
have contributed significantly to our understanding of these objects, follow-up observations<br />
of these planets' atmospheres prove difficult or impossible to carry out with existing<br />
instruments due to the faintness of most of the stars in the Kepler field. In order to better<br />
understand the nature of this class of planets, we must focus on super-Earths transiting<br />
bright stars (allowing for higher-precision observations) and/or small stars (leading to<br />
deeper transits more amenable to transmission spectroscopy measurements). I will focus<br />
on 55 Cnc e and HD 97658b, the two currently known transiting super-Earths which fall in<br />
the former category. The 55 Cnc system has been observed with the MOST space<br />
telescope for a total of 70 days over a period of three years. I will present results based on<br />
the analysis of these data, including constraints on the secondary eclipse (and hence the<br />
albedo) of 55 Cnc e, and discuss implications for the planet's atmospheric composition. I<br />
will also present MOST photometry of HD 97658b and describe the current state of<br />
knowledge of this low-density super-Earth's structure and composition, including a report<br />
on our efforts to probe its atmosphere with the HST and Spitzer.<br />
Atmospheric Composition of the ExoNeptune HAT-P-11b!<br />
Jonathan D.! Fraine!— University of Maryland<br />
We present new observations of the transiting exo-Neptune HAT-P-11b from a joint HST<br />
and warm Spitzer program to measure the transmission spectrum of its thick atmosphere.<br />
Our data cover a wide span of wavelength space, including warm Spitzer IRAC 3.6 & 4.5<br />
micron photometry and Hubble WFC3 1.1 - 1.7 micron spectroscopy from our<br />
observations, as well as Kepler's optical photometry centered at 632nm. Our WFC3<br />
spectroscopic observations are among the first using HST's new spatial scanning mode for<br />
optimised signal-to-noise spectroscopy. In addition, HAT-P-11 is one of the most active<br />
planet-hosting stars; observations of HAT-P-11b's atmosphere therefore allow us to shed<br />
light on the role that stellar activity may play in shaping the atmospheric chemistry of<br />
Neptune-sized planets. We use the Kepler photometry to model and remove the effects of<br />
the stellar activity during and surrounding our warm Spitzer transit observations. Our<br />
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combined observations provide constraints on the existence of clouds or hazes and the<br />
atmospheric chemistry at the day-night terminator.<br />
Neptunes in the Noise: Improved Precision in Exoplanet Transit Detection!<br />
Aimée E. Hall — Institute of Astronomy, University of Cambridge!<br />
SuperWASP is an established, highly successful ground-based survey that has already<br />
discovered over 80 exoplanets around bright stars. It is only with wide-field surveys such<br />
as this that we can find planets around the brightest stars, which are best suited for<br />
advancing our knowledge of exoplanetary atmospheres. However, complex instrumental<br />
systematics have so far limited SuperWASP to primarily finding hot Jupiters around stars<br />
fainter than 10th magnitude. By quantifying and accounting for these systematics up front,<br />
rather than in the post-processing stage, the photometric noise can be significantly<br />
reduced.<br />
In this paper, we present our methods and discuss preliminary results from our reanalysis.<br />
We show that the improved processing will enable us to find smaller planets<br />
around even brighter stars than was previously possible in the SuperWASP data. Such<br />
planets could prove invaluable to the community as they would potentially become ideal<br />
targets for the studies of exoplanet atmospheres.<br />
Water content and hydrogen-rich atmoshperes of sub-/super-Earths orbiting cool<br />
stars<br />
Yasunori Hori — National Astronomical Observatory of Japan!<br />
Over the past five years, close-in low-mass exoplanets orbiting cool stars has increased in<br />
number rapidly. Recently, transmission spectra in a planetary atmosphere during a primary<br />
eclipse have enabled us to explore the atmospheric compositions of super-Earths. Habitat<br />
environment and formation histories of close-in planets are closely related to volatile<br />
inventories in their atmospheres such as water and hydrogen. We have examined the<br />
water content and the amount of hydrogen-rich atmospheres of sub-/super-Earths around<br />
cool stars, performing 1,000 Monte Carlo simulations of planet formation. We have found<br />
that super-Earths with 1-30 Earth-mass are likely to possess more than 20-30wt% water<br />
mantles surrounded by thick H2-rich blankets: 0.1-20wt% H-He atmospheres for 1-10<br />
Earth-mass planets inside 0.1AU, such as GJ 1214b, and more than 50wt% for larger<br />
planets inside 1AU like GJ 436b. We have also shown that dry/wet sub-Earths with 0.1-1<br />
Earth-mass inside 1AU end in naked ones with less than 1wt% H-He atmospheres. Our<br />
results predict that sub-Earths in a habitable zone are wet but have almost no primitive<br />
atmosphere, while super-Earths near/in the zone, for example, GJ 581d, GJ 667Cc, and<br />
GJ 163c, contain abundant water and sufficient H2-rich atmospheres. Moderately-wet<br />
planets with 0.001-1wt% water similar to the Earth, i.e., land planets, are either a small<br />
fraction of sub-Earths near the inner edge or non-migrating planets near 1AU. In any case,<br />
water worlds of sub-/super-Earths in a multiple-planet system are common around cool<br />
stars.<br />
Helium-Dominated Atmosphere on Neptune-Sized Exoplanet GJ 436b<br />
Renyu Hu — California Institute of Technology!<br />
The composition of the atmosphere on exoplanet GJ 436b, the most characterized<br />
Neptune-sized exoplanet to date, has been a long-standing puzzle. The dayside emission<br />
34
of the planet shows that its atmosphere is poor in methane and rich in carbon monoxide<br />
and carbon dioxide, yet both equilibrium chemistry and disequilibrium chemistry models<br />
predict most carbon to be in the form of methane for the temperature of the planet. This<br />
contradiction is further intensified by the planet's large radius and low mean density, which<br />
requires the planet to have an extensive gas envelope. Here we provide an explanation for<br />
both the planet's emission spectrum and the planet\s radius. We propose that the<br />
atmosphere of GJ 436b is mainly composed of helium. We have used a recently<br />
established photochemistry-thermochemistry kinetic-transport model to compute the<br />
molecular composition of the thick atmosphere on GJ 436b, with the helium versus<br />
hydrogen ratio and the carbon and oxygen abundances as free parameters. The<br />
temperature of the atmosphere is self-consistently computed using grey-atmosphere<br />
approximation from the composition governed by disequilibrium chemistry. We find that a<br />
helium-dominated atmosphere with hydrogen elemental abundance less than 3% by<br />
number will have carbon dioxide and carbon monoxide as the main forms of carbon and<br />
little methane, and thus lead to spectral features consistent with observations. Such an<br />
atmosphere has mean molecular mass of ~4, only 2 times greater than that of a hydrogendominated<br />
atmosphere, and therefore the helium-dominated atmosphere can be extended<br />
enough to meet the mass-radius constraint of the planet. To form such a helium-dominated<br />
atmosphere on a Neptune-sized exoplanet, we suggest that efficient hydrodynamic<br />
atmospheric loss should have occurred in the early history of the planet. Hydrodynamic<br />
escape has removed most of the hydrogen from gas accretion, and also removed some of<br />
the helium, which resulted in the enrichment of helium in the planet's gas envelope. If this<br />
mechanism is correct, one would expect helium-dominated atmospheres to be common on<br />
Neptune and sub-Neptune sized exoplanets around M dwarfs.<br />
Exploring the Relationship Between Exoplanet Mass and Atmospheric<br />
Metallicity!<br />
Joshua Kammer — California Institute of Technology!<br />
Studies of hydrogen-dominated planetary atmospheres in our solar system have shown<br />
that as core mass fraction increases, so does atmospheric metallicity. This hypothesis<br />
holds true for Uranus and Neptune, as these planets have atmospheres more enriched<br />
relative to solar metallicity (30-40x) as compared to Jupiter (3x). Though these planets'<br />
bulk densities are comparable to many detected exoplanets in the same size range, it<br />
remains an open question whether the metallicities of exoplanet atmospheres also follow a<br />
similar trend. One way to explore the correlation between planet mass and atmospheric<br />
metallicity is by characterization of secondary eclipse emission spectra. For cooler<br />
exoplanets (T < 1000 K) atmospheric models predict that carbon chemistry should be<br />
dominated by CH4 rather than CO for an atmosphere of solar metallicity. Increasing the<br />
atmospheric metallicity will suppress the amount of methane and enhance CO, as<br />
proposed by Moses et al. (2013) to explain GJ 436b's unusually low methane-to-CO ratio.<br />
Here we present results and analysis of Spitzer 3.6 and 4.5 μm secondary eclipse<br />
observations of seven exoplanets with masses ranging from sub-Neptune to super-Jupiter<br />
in size. Although they do not provide unique constraints on all the relative abundances of<br />
water, methane, CO, and CO2, these measurements can reveal empirical trends in CH4-to-<br />
CO ratios for cooler exoplanets in this size range, and test the correlation between<br />
exoplanet mass and atmospheric metallicity.<br />
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Constraining the degeneracy of Super-Earth phase curve measurements<br />
Daniel D.B. Koll — University of Chicago!<br />
Thermal phase curve measurements of transiting exoplanets offer direct insight into how<br />
efficiently their atmospheres redistribute heat. These measurements already indicate<br />
distinct atmospheric circulation regimes on hot Jupiters, and stand to be a prime tool for<br />
remotely characterizing Super-Earth atmospheres. However, for Super-Earths the<br />
efficiency of atmospheric energy transport depends on a large number of difficult-toconstrain<br />
parameters (atmospheric composition & mass, presence/absence of condensible<br />
gases, surface type etc.). Assuming imperfect knowledge of these parameters, how<br />
degenerate are phase curve measurements Can we use phase curve measurements to<br />
robustly distinguish between different atmospheric scenarios, or do we need additional<br />
information from, e.g., transit spectroscopy<br />
To answer this question, it is necessary to comprehensively map out how the<br />
atmospheric energy transport depends on a large number of atmospheric parameters. To<br />
make the problem computationally tractable we non-dimensionalize the primitive equations<br />
and equations of grey-gas radiative transfer and find a reduced set of non-dimensional<br />
numbers that govern the atmospheric dynamics. We present simulations with an idealized<br />
dry global climate model (GCM) to demonstrate the utility of this approach. We also<br />
present results on how the atmospheric energy transport varies over the phase space<br />
spanned by these non-dimensional numbers, focusing on the relative roles of dynamics,<br />
radiation and uncertain model parameterizations.<br />
Transmission Spectroscopy of the Super-Earth Archetype GJ 1214b!<br />
Laura! Kreidberg — University of Chicago!<br />
Super-Earths, exoplanets intermediate in size between Earth and Neptune, are among the<br />
most prevalent planets in the Galaxy. Revealing the composition and formation histories<br />
of these common objects requires atmospheric characterization. I will present the results<br />
of an intensive observational campaign to study the atmosphere of the super-Earth<br />
archetype GJ 1214b. We observed 15 transits of the planet with the Hubble Space<br />
Telescope in the near-infrared, yielding the most precise exoplanet transmission spectrum<br />
measurement ever obtained in this wavelength range. Our measurements definitively<br />
distinguish between clear, high mean molecular weight atmospheric models and models<br />
with high-altitude clouds. I will also discuss preliminary results of a Gemini program to<br />
measure the transmission spectrum in the blue optical.<br />
Understanding Kepler's Super-Earths and Sub-Neptunes: Insights from Thermal<br />
Evolution and Photo-Evaporation!<br />
Eric Lopez — UC Santa Cruz<br />
NASA's Kepler mission has discovered a large new population of super-Earth and sub-<br />
Neptune sized planets. Although we have no analogous planet in our own solar system,<br />
such planets are incredibly common. Understanding the nature and formation of systems<br />
of these planets is one of the key challenges for theories of planet formation. We use<br />
models of thermal evolution and photo-evaporation to constrain the structure, composition,<br />
and evolution of low-mass planets. Over time Neptune-like planets with large H/He<br />
envelopes can be transformed into rocky super-Earths. We show that differences in mass<br />
loss history provide a natural explanation for many features of the Kepler multi-planet<br />
systems, such as large density contrast between Kepler-36b and Kepler-36c. For the<br />
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oader population of Kepler planets, we find that there is a threshold in bulk planet<br />
density, mass, and incident flux above which no low-mass transiting planets have been<br />
observed. We suggest that this threshold is due to XUV-driven photo-evaporation and<br />
show that it is well reproduced by our evolution models.<br />
Chemical Characterization of Super-Earths: Interiors, Atmospheres, and Formation<br />
Conditions<br />
Nikku! Madhusudhan — Yale University<br />
Recent advances in exoplanetary science are leading to unprecedented observations of<br />
super-Earths. The observed masses, radii, and temperatures of super-Earths provide<br />
constraints on their interior structures, geophysical conditions, as well as their atmospheric<br />
compositions. Some of the most recently detected super-Earths span a wide gamut of<br />
possible compositions, from super-Mercuries and lava planets to water worlds with thick<br />
volatile envelopes. In this work, we report joint constraints on the interior and atmospheric<br />
compositions of several super-Earths and discuss their possible formation scenarios using<br />
new and comprehensive hybrid models of their interiors, non-gray atmospheres, and<br />
formation conditions. Our model constraints are based on the masses and visible radii, as<br />
well as the latest infrared measurements of transmission and emission spectrophotometry<br />
where available, in addition to revised estimates of the stellar parameters. We will present<br />
a comparative analysis of several transiting super-Earths currently known and will discuss<br />
in detail two super-Earths (GJ 1214b and 55 Cancri e) which have atmospheric data<br />
available and which represent two distinct end members in the thermo-chemical phase<br />
space of super-Earth conditions. We will also discuss the implications of our results for the<br />
diversity of geochemical and geophysical conditions on super-Earths. We will conclude<br />
with comments on new observational, theoretical, and experimental efforts that are critical<br />
to detailed characterization of super-Earths.<br />
Multi-Color Simultaneous Transit Photometry of Planets around Cool Host Stars<br />
Norio Narita — National Astronomical Observatory of Japan<br />
Transmission spectroscopy is a powerful method to investigate planetary atmospheres for<br />
transiting exoplanets. For ground-based large (6-10 m class) telescopes, multi-object<br />
spectroscopy and high dispersion spectroscopy have shown successful results for this<br />
purpose. For smaller (1-2 m class) telescopes, multi-color simultaneous transit photometry<br />
provides an alternative and efficient way for transmission spectroscopy. In this talk, we<br />
focus on such multi-color simultaneous transit photometry for planets around cool host<br />
stars, including GJ1214, GJ3470, and WASP-80. We present some observational results<br />
taken in 2011 and 2012 seasons (e.g., Narita et al. 2013a, Narita et al. 2013b, Fukui et al.<br />
2013) and preliminary results for data taken in 2013 season.<br />
Characterizing the Demographics of Exoplanet Bulk Compositions<br />
Leslie Rogers — California Institute of Technology<br />
The Kepler Mission has discovered thousands of sub-Saturn-sized transiting planet<br />
candidates. Using planet interior structure models, we constrain the bulk compositions of<br />
the more than 50 known sub-Saturn-sized transiting planets with measured masses. Our<br />
model considers fully differentiated planets comprised of up to four layers: an iron core, a<br />
silicate mantle, a water mantle, and a gas envelope. We calculate the planet interior<br />
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structure by integrating the coupled differential equations describing an evolving selfgravitating<br />
body, employing modern equations of state for the iron, silicates, water, and<br />
gas. For any individual planet, a wide range of compositions is consistent with the<br />
measured mass and radius. We consider the planets as an ensemble, and discuss how<br />
thermal evolution, mass loss, and observational biases sculpt the observed planet massradius-insolation<br />
distribution. Understanding these effects is crucial for constraining the<br />
demographics of small planet bulk compositions and for extracting signatures of the planet<br />
formation process from the accumulating census of transiting planets with dynamical<br />
confirmation.<br />
Ground-based search for the transit of Alpha Cen Bb<br />
Aurelien Wyttenbach — Geneva Observatory<br />
In late 2012, a planet with a minimum mass of 1.13 earth mass may have been detected<br />
around Alpha Cen B with the HARPS spectrograph. With a 3.2 days orbit, the planet has a<br />
10% transit probability. However, with an expected transit depth of ~100 ppm, searching<br />
for the transit is challenging, especially from the ground because of correlated noise in the<br />
light curves. The extreme brightness of Alpha Cen B, and the close separation from Alpha<br />
Cen A (4") complicate the task further. We have developed and tested a method designed<br />
to beat down correlated noise, while coping with the brightness and duplicity of the Alpha<br />
Cen system, using high-resolution spectroscopy. Here, we present the first light curve of<br />
Alpha Cen B obtained using this method during one night of observations with UVES at<br />
the VLT.<br />
HOT JUPITERS: OBSERVATIONS<br />
Spectrophotometry with SOFIA: First results!<br />
Daniel!Angerhausen — Rensselaer Polytechnic Institute<br />
Over the past decade the transit method (measuring the small, wavelength-dependent<br />
variation in flux as an exoplanet passes in front of or behind its parent star) has produced<br />
a number of exciting characterization results. The NASA/DLR Stratospheric Observatory<br />
for Infrared Astronomy (SOFIA), a 2.5-meter infrared telescope on board a Boeing 747-SP,<br />
has a specific and unique phase space for these extremely precise time-domain<br />
spectrophotometric observations at IR wavelengths: It operates in the right wavelength<br />
regime, where the planet's black-body temperature peaks and contrast ratios between star<br />
and planet improve. The airborne observatory is able to avoid most of the perturbing<br />
variation of atmospheric trace gases that produce the dominant source of noise for<br />
ground-based observations in the near-infrared. These telluric molecules are also the<br />
species of interest in the exo-atmospheres. The SOFIA telescope is operating at much<br />
lower temperatures (~240 K) than ground-based telescopes (~273 K). Therefore thermal<br />
background contributions, the dominant noise source for transit observations at<br />
wavelengths longer than 3 micron, will be significantly reduced. The mobile platform<br />
SOFIA can observe time-critical events, such as the rare transits of long-period planets,<br />
under optimized conditions. After the end of Spitzer and until the start of the JWST<br />
mission, SOFIA will be the only observatory capable of NIR spectrophotometry of<br />
exoplanet atmospheres beyond 1.7 micron (the upper limit for HST after the last upgrade)<br />
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at an altitude where the impact of variable telluric absorption is small enough for high<br />
precision observations of the same molecules also present in exoplanet atmospheres.<br />
Here we present SOFIA's unique advantages in comparison to ground- and space-based<br />
observatories in this field of research and present the very first spectrophotometric<br />
exoplanet observations that were or will be conducted in SOFIA’s cycles 1 and 2.<br />
Characterisation of Exoplanets using Polarization!<br />
Jeremy Bailey — University of New South Wales!<br />
Light reflected from the atmospheres of extrasolar planets will be polarized, and the<br />
detection and measurement of that polarization provides a means of characterising the<br />
atmospheres that provides complementary information to that from spectroscopy. At<br />
UNSW we are building a new instrument with the aim of measuring polarization in the<br />
combined light of a star and hot Jupiter planet, and thus detecting the polarization of the<br />
planet. We have also incorporated polarization capability into our atmospheric modelling<br />
code VSTAR. Polarization is particularly sensitive to the presence of atmospheric clouds<br />
and hazes. I will describe our current progress on these developments, and discuss the<br />
potential of such techniques for the study of exoplanet atmospheres.<br />
Polarimetric detection and characterization of hot Jupiters!<br />
Andrei! Berdyugin — FINCA, University of Turku, Finland<br />
The light scattered in planetary atmospheres is linearly polarized perpendicular to the<br />
scattering plane. In general, when the planet rotates around the parent star, the scattering<br />
angle changes and the Stokes parameters Q and U of linear polarization vary. If the orbit is<br />
close to circular, two peaks per orbital period are observed. The observed polarization<br />
variability exhibits therefore the orbital period of the planet and reveals the inclination,<br />
eccentricity, and orientation of the orbit. Due to proximity to the star, hot giant planets with<br />
short orbital periods ("hot Jupiters") may develop extended peculiar atmospheres and<br />
halos which effectively scatter the light in the blue spectral region. This can give rise to a<br />
degree of polarization detectable with the currently existing modern polarimeters.<br />
Parameters of this polarization, e.g., wavelength dependence, are defined by physical<br />
conditions in the upper layers of the planetary atmosphere. Thus, polarimetry of hot "blue<br />
Jupiters" in combination with other methods of observations may be used to draw<br />
conclusions on properties of their atmospheres.<br />
Here we present new polarimetric observations of several hot Jupiters, both transiting<br />
and non-transiting, in three bands: blue, green, and red. These data were obtained with<br />
two instruments: (1) our new Double Imaging Polarimeter (DIPol-2) at the 60cm KVA<br />
telescope on La Palma, routinely providing polarimetric accuracy of 10 -5 , and (2) the FORS<br />
polarimeter at the VLT, ESO, with the maximum accuracy of 10 -4 . We analyze these data<br />
using our model calculations and infer planet orbit parameters and atmosphere reflectivity.<br />
We compare our results with measurements of the secondary eclipses of hot Jupiters.<br />
Detecting water in hot Jupiter atmospheres with high-resolution ground-based<br />
spectroscopy!<br />
Jayne!Birkby — Leiden Observatory<br />
The robust determination of the chemical make-up of exoplanet atmospheres is crucial to<br />
understanding their structure, formation, and evolution, particularly in the case of the major<br />
39
carbon- and oxygen-bearing species. We present ground-based high-resolution spectra<br />
from CRIRES/VLT at 3.2 microns of several transiting and non-transiting hot Jupiter<br />
atmospheres (51 Peg b, Tau Boo b, and HD 209458 b), in which we have searched for the<br />
radial velocity signature of water, methane and carbon dioxide molecules in the planetary<br />
atmospheres. We compare the results of our search with the detections of CO already<br />
reported in these hot Jupiter atmospheres, and discuss their temperature-pressure profiles<br />
and relative abundance ratios. Preliminary results indicate a significant abundance of<br />
water in 51 Peg b, consistent with tentative reports of water at 2.3 microns.<br />
Observation of Magnesium : A new Probe of Exoplanets' Thermospheres and<br />
Exopheres!<br />
Vincent Bourrier — Institut d'Astrophysique de Paris<br />
Transit observations of HD209458b in the UV revealed signatures of neutral magnesium<br />
escaping the planet upper atmosphere. The absorption detected in the MgI line arises from<br />
the transition region between the thermosphere and the exosphere, and provides<br />
unprecedented information on the physical conditions at the altitude where atmospheric<br />
escape takes place. These observations have been interpreted using a 3D particle model<br />
coupled with an analytical modeling of the atmosphere below the exobase. Thus we<br />
estimated the planetary wind velocity and the exobase altitude, and also obtained an new<br />
estimate of the atmospheric escape rate. More generally, we show that magnesium<br />
absorption lines provide a powerful tool to study the upper part of exoplanets'<br />
atmospheres. We identified a dozen of exoplanets with host stars bright enough for their<br />
atmosphere to be observed using the magnesium lines.<br />
Probing the atmospheres of non-transiting exoplanets: CO and H2O absorbtion in<br />
HD179949b!<br />
Matteo Brogi! — Leiden Observatory<br />
In recent years, ground-based high-resolution spectroscopy has become a powerful<br />
method for studying exoplanet atmospheres. It is capable to robustly identify molecular<br />
species via line matching, and to detect the radial velocity of the planet itself. Moreover, by<br />
targeting the planet thermal emission directly, it does not require the planet to transit.<br />
Thanks to this method, the mass and orbital inclination of non-transiting planets can be<br />
determined and their atmospheric composition studied.<br />
I will present our latest K-band observations of HD179949b with CRIRES at R=100,000.<br />
We detect an absorption signal from water vapour and carbon monoxide at SNR=6.5,<br />
meaning that the portion of the planet’s atmosphere probed by these observations does<br />
not have an inversion layer. The derived mass and orbital inclination for the planet are<br />
(0.98+/-0.04) Jupiter masses and (68+/-4) degrees respectively.<br />
Except for young, self-luminous directly-imaged planets, only high-resolution<br />
spectroscopy currently allows the atmospheric characterization of non transiting planets.<br />
With the next generation of ELTs and this technique, a complete census of this class of<br />
bodies will be possible, revealing for the first time their properties and actual mass<br />
distribution.<br />
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Spectroscopic observations of the hot-Jupiter HD 189733b with HST WFC3<br />
Nicolas Crouzet — Space Telescope Science Institute<br />
Spectroscopic observations of exoplanets are crucial to infer the composition and<br />
properties of their atmosphere. In particular, identifying molecular features and measuring<br />
their amplitude constrain the presence of and the effect of clouds, which are thought to<br />
play a major role in the atmosphere of hot-Jupiters. After a controversy on the reliability of<br />
NICMOS results, the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope<br />
now delivers hot-Jupiter spectra with much higher fidelity than HST NICMOS had in the<br />
past. We observed the well studied hot-Jupiter HD 189733b with WFC3 in the bandpass<br />
1.1 to 1.7 microns using the newly implemented spatial scanning mode, which largely<br />
increases the number of collected photons compared to the staring mode. Also, the<br />
spatially-scanned WFC3 data produce satisfactory results with a very straight-forward<br />
analysis, a welcome change from the old technique of staring-mode observations,<br />
especially those obtained with HST NICMOS (Crouzet et al. 2012). We will discuss the<br />
amplitude of absorption seen in the transmission spectrum and the inferred atmospheric<br />
composition for HD 189733b, and compare them with recent results by Deming et al.<br />
(2013) for the exoplanets HD 209458b and XO-1b using similar WFC3 data. Our data<br />
reinforces the idea that molecular features of hot Jupiters may be attenuated by the<br />
presence of clouds or haze. We derive the planetary emission spectrum using the same<br />
technique with observations made at secondary eclipse.<br />
A Closer Look at Correlated-Noise Measuring Techniques for Exoplanet Light<br />
Curves<br />
Patricio Cubillos — University of Central Florida<br />
Among the many exoplanet light-curve fits analyzed to date, it is not unusual to detect<br />
some degree of time correlation in the residuals (also known as correlated or red noise).<br />
An incorrect assessment of correlated noise can lead to under- or overestimating the<br />
uncertainties on the planet's physical parameters, giving more or less significance to the<br />
results than they should have. While the sources of correlated noise are not always<br />
known (e.g., from an inaccurate systematics treatment or some unaccounted astrophysical<br />
effect), there are methods that aim to assess the degree of correlated noise, like the RMSvs.-bin<br />
size plot, prayer beads, and wavelet-based likelihood fitting. Yet, there are no indepth<br />
statistical studies in the literature for some of the techniques currently used.<br />
We subjected these correlated-noise assessment techniques to basic tests on synthetic<br />
data sets to characterize their features and limitations.<br />
Initial results indicate, for example, that sometimes the RMS-vs.-bin size plot has large<br />
artifacts when the bin size is similar to the observation duration. Further, prayer beads<br />
rarely indicate the right level of correction for correlated noise. We have applied these<br />
techniques to several Spitzer secondary-eclipse hot-Jupiter light curves and discuss their<br />
implications.<br />
New possibilities for exoplanet observations at high spectral resolution<br />
Remco de Kok — SRON<br />
In the last few years there have been several detections of molecules in hot-Jupiter<br />
atmospheres using observations at very high spectral resolution (R=100,000), most<br />
notably using CRIRES on the VLT. These observations have the great advantage that they<br />
allow unambiguous detection of specific molecules. On the other hand, determining<br />
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abundances of molecules in the atmosphere has not yet been possible using only highresolution<br />
observation due to degeneracies. We will discuss what other high-resolution<br />
measurements can be performed with current instruments to obtain a better understanding<br />
of the chemistry and dynamics of hot-Jupiter atmospheres. We will present results from<br />
our sensitivity analysis of simulated CRIRES observations, showing at what wavelengths<br />
particular molecules are best detected. We will also discuss whether molecules can be<br />
detected from high-resolution thermal radiation from the night-side. We find that for some<br />
planets the night-side might even yield a larger signal than the day-side.<br />
2D mapping of the eccentric exoplanet HAT-P-2b!<br />
Julien!de Wit — Massachusetts Institute of Technology<br />
The class of close-in gas giant planets known as hot Jupiters provides an exceptional<br />
insight into atmospheric circulation, as these planets are expected to be both highly<br />
irradiated and in either synchronous or pseudo-synchronous orbits depending on their<br />
orbital eccentricity. We can probe atmospheric circulation through phase curve<br />
measurements, which tell us about their brightness as a function of longitude. Recently, a<br />
new observational tool, “eclipse mapping”, has been developed enabling the creation of<br />
maps that are resolved in both longitude and latitude, unlike phase curves. To date, only<br />
one planet (HD 189733b) has been successfully mapped using this technique. Here, we<br />
present the first two-dimensional maps of the eccentric exoplanet HAT-P-2b in the Spitzer<br />
4.5 micron bandpass. This map is derived from fourteen new secondary eclipses observed<br />
in the 4.5 micron band.<br />
The high eccentricity of HAT-P-2b leads to fundamental differences between its<br />
atmospheric circulation and that of HD189733b. A high eccentricity prevents tidal locking<br />
and implies time-variable stellar heating, hence time-variable forcing. HAT-P-2b is eclipsed<br />
post-periastron, hence we use eclipse mapping to gain insights into how its atmosphere<br />
responds to transient heating. In particular, HAT-P- 2b’s map will yield constraints on its<br />
radiative and advective time-scales and probe the spatial extent of its dayside thermal<br />
inversion. We will discuss the implication of our findings in the context of atmospheric<br />
circulation models that can be applied to a wide range of planets.<br />
Mapping Clouds in Exoplanet Atmospheres<br />
Brice-Olivier Demory — Massachusetts Institute of Technology<br />
Clouds and hazes are ubiquitous in the solar system's giant planet and brown-dwarf<br />
atmospheres. It has been long suggested that clouds would also play a strong role in<br />
shaping the spectra of exoplanets in general and hot Jupiters in particular. Recently,<br />
clouds have been reported in the atmosphere of HD189733b. We will present the first<br />
results of a program aiming at detecting and characterizing clouds in hot-Jupiter<br />
atmospheres. We use joint space-based visible+IR occultation and phase-curve<br />
photometry to reconstruct low-resolution maps of thick clouds. We will discuss the possible<br />
formation scenarios for these clouds and explore the degeneracies involved in the retrieval<br />
of the particles properties (coverage, size distribution, vertical extent, composition, shape,<br />
etc.). We will finally discuss how near-to-come space- and ground-based facilities will<br />
contribute to the detailed characterization of these clouds.<br />
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Characterising Exoplanets Using Kepler Phase-Curves!<br />
Lisa Esteves — University of Toronto!<br />
Although the Kepler mission is mainly aimed at searching for exoplanet transits, its highprecision<br />
photometry and long-term monitoring of the same field, makes it ideal to use for<br />
phase-curve measurements. Recently, using almost four years of Kepler data, we have<br />
been able to measure the phase-curve of eight Kepler objects. For five of these we<br />
present the very first phase-curve measurements, while for the other three objects we<br />
present greatly refined parameters. In addition we demonstrate how phase-curves<br />
measurements can be used as a very powerful tool for ruling out false positives within the<br />
Kepler planet candidate population.<br />
Measuring the reflection signal of HD189733b!<br />
Tom Evans — Oxford University!<br />
The multi-wavelength reflection signal of an exoplanet provides a valuable insight into the<br />
composition and structure of its atmosphere. In this talk, I will describe our measurement<br />
of a secondary eclipse of HD189733b across the 290-570nm wavelength range, made<br />
using HST/STIS. We found that the albedo of the planet decreases towards longer<br />
wavelengths in this range from approximately Ag=0.4 to Ag
data reduction stage crucial to our current understanding of exoplanet atmospheres. This<br />
has prompted the development of new, sophisticated techniques to robustly extract signals<br />
from transit data, and also a drive to use new observing facilities to re-observe and confirm<br />
exoplanet signals. Ground-based telescopes are now playing an increasingly prominent<br />
role, with multi-object spectrographs enabling differential ground-based spectrophotometry.<br />
These observations are now providing similar precision to space-based observations<br />
where appropriate comparison stars are available, and should allow us to verify spacebased<br />
spectra and ease our dependence on single instruments. Here, we present efforts<br />
to measure transmission spectra using the Gemini telescopes, with the GMOS multi-object<br />
spectrographs, and discuss how we extract the atmospheric signals in the presence of<br />
complex noise sources. We report transit observations of WASP-29, HAT-P-32 and<br />
(possibly) HAT-P-33, reaching sufficient precision to probe atmospheric features. These<br />
reveal featureless spectra possibly caused by the presence of clouds in the upper<br />
atmospheres, although further observations are required to confirm this.<br />
On the Statistical Significance of Trends in Exoplanetary Emissions!<br />
Joseph Harrington — University of Central Florida<br />
We have examined the fluxes of exoplanetary atmospheres as measured during<br />
secondary eclipses. Cowan and Agol (2011) and we (Harrington et al. 2007, 2010, 2011,<br />
2012, 2013) have noted that at equilibrium temperatures above about 2000 K (zero<br />
albedo, uniform redistribution), observed exoplanet fluxes are substantially higher than<br />
even the elevated equilibrium temperature predicts. With a substantial increase in the<br />
number of atmospheric flux measurements, we can now test the statistical significance of<br />
this trend. We can also cast the data on a variety of axes to search further for the physics<br />
behind both the jump in flux above about 2000 K and the wide scatter in fluxes at all<br />
temperatures.<br />
Enshrouded Close-In Exoplanets<br />
Carole Haswell — Open University<br />
Our near-UV HST observations of the extreme hot Jupiter WASP-12b revealed<br />
extended exospheric gas overfilling the planet\s Roche lobe and causing<br />
reproducible enhanced transit depths at 65 distinct wavelengths. There is<br />
complete absorption, i.e. zero emergent flux, in the cores of the very strong<br />
MgII h&k lines at all observed orbital phases.<br />
I will present several lines of evidence to show this is due to diffuse gas lost<br />
from WASP-12b, which enshrouds the entire planetary system. Our results suggest a new<br />
interpretation of the known correlation between hot Jupiter atmosphere type and host star<br />
activity as indicated by the cores of the very strong CaII H&K lines. I will present recent<br />
observations of the putative evaporating rocky exoplanet KIC 1255b. WHT/ULTRACAM<br />
simultaneous multiwavelength light curves obtained in July 2013 have implications for the<br />
dust scattering function,an empirical upper limit on the size of the planet, and the limitcycle<br />
mechanism which modulates the observed dust extinction. We used CFHT/<br />
ESPaDOnS to perform transmission spectroscopy searching for metal rich vapour<br />
expected to co-exist with the dust as the gas phase component of the planetary mass loss.<br />
Finally I will discuss the general implications of these findings for the Galaxy’s population<br />
of planets and for studies of star-planet interactions.<br />
44
Characterization of Exoplanets using Planetary Radial Velocimetry!<br />
Hajime Kawahara — The University of Tokyo!<br />
Recently radial velocity curves of exoplanets have been measured with the aid of the high<br />
dispersion instrument CRIRES on VLT (e.g. Snellen et al. 2010, Brogi et al. 2012, Rodleret<br />
al. 2012, Birkby et al. 2013). I consider the effect of planet’s spin on the planetary radial<br />
velocity. With simple assumptions, I find that the radial velocity curve is distorted by the<br />
planetary spin and this anomaly is characterized by spin radial velocity at equator and a<br />
projected angle on a celestial plane between the spin axis and the axis of orbital motion<br />
(Kawahara 2012). I will discuss the feasibility of the precise planetary radial velocity<br />
measurement for such as the spin measurement, with possible instruments in near future.<br />
Polarimetry of transiting exoplanetary systems!<br />
Nadiia!Kostogryz — Kiepenheuer-Institut für Sonnenphysik!<br />
Since the discovery of the first extrasolar planet, methods of their detection and<br />
characterization are rapidly developing. The best-characterized planets are so far those<br />
which were detected by different methods. Thanks to the recent high-accuracy polarimetric<br />
instruments, polarimetry has become an independent technique for characterizing<br />
exoplanetary systems as it yields information inaccessible to other methods. As was<br />
shown observed polarization variability due to scattering in the planetary atmosphere<br />
reveals the orbital period of the planet, inclination, eccentricity, orientation of the orbit as<br />
well as the nature of scattering particles in the planetary atmosphere.<br />
We present and discuss another polarimetric effect caused by a planet transiting the stellar<br />
disk and, therefore, breaking its symmetry and resulting in linear polarization of a partially<br />
eclipsed star. Such an effect was predicted in 1950 for binary stars, and it was first<br />
detected in the eclipsing binary Algol. Estimates of this effect for transiting planets were<br />
made only recently. In particular, we demonstrated that the maximum polarization for one<br />
of the brightest transiting planets HD189733b strongly depends on the centre-to-limb<br />
variation of linear polarization for the host star. However, observational and theoretical<br />
studies of the limb polarization have been largely concentrated on the Sun. As was shown<br />
in our previous study, we expect to observe a larger centre-to-limb linear polarization for<br />
cooler stars. Here we solve the radiative transfer problem for polarized light and simulate<br />
the centre-to-limb polarization for stars of different spectral classes taking into account<br />
various opacities. Knowing stellar limb polarization is also necessary for evaluating stellar<br />
contribution when interpreting scattering polarization from spatially unresolved planets at<br />
elongations. In addition, the radius of the grazing planet can be determined from transit<br />
polarimetry when transit photometric data become unreliable. Employing our simulations<br />
for all transiting exoplanets we select most promising targets for future polarimetric<br />
observations.<br />
Detecting Exoplanetary Magnetic Fields<br />
Joe Llama — University of St Andrews<br />
In this work we explore the possibility of detecting magnetic fields around extrasolar<br />
planets using asymmetries in their transit light curves. Observations of the very close-in,<br />
highly inflated planet WASP-12b have revealed an asymmetry in the near-UV light curve<br />
when compared to the optical transit. It has been suggested that this asymmetry may be<br />
caused by the stellar wind colliding with the magnetosphere of the planet, resulting in the<br />
formation of a magnetospheric bow shock. We show how modelling such a shock allows<br />
45
us to reproduce this transit asymmetry and to place constraints on the magnetic field<br />
strength of the planet.<br />
Characterizing Exoplanet Atmospheres with HST/WFC3<br />
Avi Mandell — NASA GSFC !<br />
The Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) provides the<br />
potential for spectroscopic characterization of molecular features in exoplanet<br />
atmospheres, a capability that has not existed in space since the demise of NICMOS on<br />
HST and the IRS on Spitzer. We present an analysis of transit spectroscopy for three<br />
extrasolar planets observed during the HST Cycle 18: WASP-12 b, WASP-17 b, and<br />
WASP-19 b. WASP-12 b and WASP-19 b are two of the hottest exoplanets discovered to<br />
date, while WASP-17 b has a much lower equilibrium temperature but has one of the<br />
largest atmospheric radii of known transiting planets; measurement of molecular<br />
absorption in the atmospheres of these planets offers the chance to explore several<br />
outstanding questions regarding the atmospheric structure and composition of these highly<br />
irradiated, Jupiter-mass objects. The observations cover a single primary transit for each<br />
planet, and we analyze the data using a strategy that allows us to correct for channel- or<br />
wavelength-dependent instrumental effects by utilizing the band-integrated time series and<br />
measurements of the drift of the spectrum on the detector over time. We achieve almost<br />
photon-limited results for individual spectral bins, but the uncertainties in the transit depth<br />
for the the band-integrated data are exacerbated by the uneven sampling of the light curve<br />
imposed by the orbital phasing of HST observations. Our final transit spectra for all three<br />
objects are consistent with the presence of a broad absorption feature at 1.4 microns most<br />
likely due to water. However, the amplitude of the absorption is less than that expected<br />
based on previous observations with Spitzer, possibly due to hazes absorbing in the NIR<br />
or non-solar compositions. The degeneracy of models with different compositions and<br />
temperature structures combined with the low amplitude of any features in the data<br />
preclude our ability to place unambiguous constraints on the atmospheric composition, but<br />
future observations with WFC3 to improve the S/N and/or a comprehensive multiwavelength<br />
analysis will allow us to better distinguish between different models.<br />
HST/STIS Transmission Spectral Survey: Probing the Atmospheres of HAT-P-1b and<br />
WASP-6b!<br />
Nikolay Nikolov — University of Exeter<br />
We present optical to near-infrared transmission spectra of HAT-P-1b and WASP-6b, part<br />
of a Large HST/STIS hot Jupiter transmission spectral survey (P.I. David Sing). The<br />
spectra for each target cover the regimes 290-570nm and 524-1027nm, with resolving<br />
power of R = 500. The HAT-P-1b data is coupled with a recent HST/WFC3 transit,<br />
spanning the wavelength range 1.087-1.687 micron (R=130), acquired in spatial scan<br />
mode. The WASP-6b data is complemented with Spritzer/IRAC 3.6 and 4.5 micron transit<br />
observations, part of a comparative exoplanetology program (P.I. Jean-Michel Desert). The<br />
transmission spectrum of HAT-P-1b shows a strong absorption signature shortward of<br />
550nm, with a strong blueward slope into the near-UV. We detect atmospheric sodium<br />
absorption at a 3.3-sigma significance level, but see no evidence for the potassium<br />
feature. The red data implies a marginally flat spectrum with a tentative absorption<br />
enhancement at wavelength longer than ~850nm. The combined STIS and WFC3 optical<br />
to NIR spectra differ significantly in absolute radius level (4.3+/-1.6 pressure scale<br />
heights), implying strong optical absorption in the atmosphere of HAT-P-1b. The optical to<br />
46
near-infrared difference cannot be explained by stellar activity, as simultaneous stellar<br />
activity monitoring of the G0V HAT-P-1b host star and its identical companion show no<br />
significant activity that could explain the result. The red transmission spectrum of<br />
WASP-6b is flat with tentative detection of sodium and potassium. We compare both<br />
spectra with theoretical atmospheric models which include haze, sodium and an extra<br />
optical absorber in the case of HAT-P-1b. We find that both an optical absorber and a<br />
super-solar sodium to water abundance ratio might be a scenario explaining the HAT-P-1b<br />
observations.<br />
Characterizing Hot Jupiter Atmospheres with Ground-Based Facilities: Instrument<br />
Performance and New Results<br />
Lisa Nortmann — University of Göttingen<br />
Transiting planets are of particular interest for exoplanet atmosphere science as the<br />
geometry of their orbits enables us to investigate atmospheric transmission spectra.<br />
During transit the upper layers of an exoplanet atmosphere are penetrated by its host<br />
star’s light. As a consequence the fingerprint of the atmospheric composition at the<br />
terminator region can be observed in form of a color dependent variation in the occultation<br />
depth. One of the biggest remaining challenges of multi-color transit observations is the<br />
proper removal of systematic noise signals. Such signals are frequently found to distort the<br />
light curves in data of both ground-based and space-based origin and in many cases their<br />
source is not well understood.<br />
Our group uses the ground-based facilities ESO/VLT+FORS2 and the Spanish 10-meter<br />
telescope GranTeCan+OSIRIS to probe the atmosphere of hot Jupiters with the technique<br />
of multi-object spectrophotometry. I will address our new findings regarding the source and<br />
nature of instrument specific systematics that we noticed to commonly affect data taken<br />
with these two instruments. Furthermore, I will introduce our approach to the correction of<br />
these noise signals, which allows us to retrieve high quality spectrophotometric data. As an<br />
example I will present the transmission spectra of the two hot Jupiters WASP-17b and<br />
HAT-P-32b which we obtained in the optical wavelength region between 500 and 1000 nm.<br />
In this broad wavelength interval the transmission spectra of hot Jupiters are predicted to<br />
exhibit sodium, potassium, water and titanium/vanadium oxide absorption. The abundance<br />
of these atmospheric species is of particular interest, as they serve as good indicators for<br />
the prevalent temperature and, consequently, can help to shed light on the mechanisms of<br />
heat re-distribution between the planet’s day and night side.<br />
A Secondary Eclipse Survey of the Hottest Exoplanets with Palomar and Spitzer!<br />
Joseph G. O'Rourke — California Institute of Technology<br />
Combined ground- and space-based secondary eclipse observations provide an<br />
invaluable window on the dayside emission spectra for transiting exoplanets, as<br />
demonstrated by recent studies of WASP-12b. Here, we present preliminary results from<br />
our survey of hot Jupiters with relatively high temperatures (>2000 K). We utilize<br />
secondary eclipse photometry at 3.6 and 4.5 µm taken with the IRAC camera aboard the<br />
Spitzer Space Telescope during the warm Spitzer mission and in the H and Ks bands with<br />
the WIRC camera at the Palomar 200-inch Hale Telescope. We discuss how the<br />
installation of a new diffusing filter in the WIRC filter wheel mitigates many of the<br />
systematic problems encountered during ground-based observations. With multiwavelength<br />
photometry and spectroscopy for a large sample of hot Jupiters, we can<br />
search for trends in atmospheric characteristics, including elemental abundances, C/O<br />
47
atios, and temperature profiles, that might be important clues to their formation and<br />
evolution.<br />
Models of exoplanet evaporation<br />
James! Owen — Canadian Institute for Theoretical Astrophysics<br />
Given the numerous exoplanets discovered at close separations to their parents stars,<br />
where the stellar UV & X-ray radiation fields can heat the upper layers of the planets<br />
atmosphere to 10 4 K, evaporation is bound to occur. I will discuss evaporation in the<br />
hydrodynamic limit which can be driven by either the EUV or X-ray radiation, and the<br />
associated mass-loss rates. I will argue that evaporation of close-in exoplanets does not<br />
occur in `energy-limited' sense where PdV work dominates the energy loss, but that<br />
radiative cooling and recombinations are dominant energy sinks. Finally, I will present the<br />
results of multi-dimensional calculations and discuss the role planetary and stellar<br />
magnetic fields play in exoplanet evaporation, along with the long term impact of<br />
evaporation on exoplanets.<br />
Transit Transmission spectroscopy with GTC: First results<br />
Enric Palle — Instituto de Astrofisica de Canarias<br />
Our group is presently conducting an observational campaign, using the 10-meter Gran<br />
Telescopio Canarias (GTC), to obtain long-slit spectra in the optical range of several<br />
planetary host stars (and a reference star) during a transit event. The GTC instrument<br />
OSIRIS consists of two CCD detectors with a field of view of 7.8 X 7.8 arcmin. We used<br />
OSIRIS in its long-slit spectroscopic mode, selecting the grism R=1000 which covers the<br />
spectral range of 520-1040 nm, and a custom-built slit of 12 arcsec of width. A Markov<br />
Chain Monte Carlo (MCMC) Bayesian approach is used for the transit fitting, and the level<br />
of red noise in the light curves is estimated using the method of Winn et al. (2008). Here,<br />
we will present refined planet parameters, planet color signatures, and the transmission<br />
spectrum of a set of know transiting exoplanets, namely: WASP-43b, HAT-P-12b,<br />
WASP-48b, and KIC 12557548b. With our instrumental setup, GTC has been able to<br />
reach precision down to 250 ppm (WASP-48b, V=11.06 mag) for each color light curve 15<br />
nm wide. We will also discuss the capabilities and advantages of GTC as tool for the<br />
follow up of faint Kepler targets, such as KIC 12557548b. The light curves obtained for this<br />
object with low resolution gratings allow us to reach 300 ppm in a 4-min sampled curve,<br />
thus revealing the detailed shape, small scale structures, and color information of<br />
individual transits of KIC12557548b.<br />
Characterisation of exoplanet atmospheres with KMOS<br />
Hannu Parviainen — University of Oxford<br />
We present our preliminary results and experiences with the KMOS (K-Band Multi-Object<br />
Spectrometer) instrument in the characterisation of exoplanet atmospheres using transit<br />
transmission spectroscopy, and detail our approach to the data reduction and analysis.<br />
Our experiences are mainly based on transits observed during the instrument's<br />
commissioning phase, and the investigation of the KMOS instrument's applicability to<br />
transit spectroscopy was an important secondary goal along with the science driver.<br />
48
Transit transmission spectroscopy offers a direct way to study the atmospheric properties<br />
of transiting exoplanets. However, the variations in the transit depth are small, of order<br />
10 -4 , and disentangling the minute changes in the transit signal from the systematic noise<br />
signals is all but trivial.<br />
KMOS is a NIR multi-object spectrometer capable of observing spatially resolved spectra<br />
of 24 2.8x2.8 arcsecond freely positionable fields simultaneously. Each field is<br />
implemented using an integral field unit (IFU) with a 14x14 pixel spatial resolution. The<br />
ability to observe simultaneous spectra from a number of separate fields allows for high<br />
flexibility in the selection of comparison stars for relative spectroscopy, facilitating the<br />
reduction of common systematics. However, the use of IFUs with small spatial footprints<br />
creates also new challenges that need to be overcome before the instrument's full<br />
potential can be used.<br />
Direct evidence of the inversion layer in HD 209458 b from high-dispersion<br />
spectroscopy<br />
Henriette Schwarz — Leiden University<br />
We present preliminary results from high-resolution thermal emission spectra of the hot<br />
Jupiter HD 209458 b. This bright transiting planet is interesting because it is a good<br />
candidate for a hot Jupiter with an inversion layer in its atmosphere. Snellen et al. (2010)<br />
observed HD 209458 b during a transit with high-resolution spectra at wavelengths around<br />
2.3 micron, and they detected molecular absorption from carbon-monoxide. The new dataset<br />
again uses the CRIRES spectrograph at VLT. This time we are looking at the thermal<br />
emission from the hot day-side of the planet at phases close to the secondary eclipse. We<br />
see no evidence for CO absorption in the thermal spectra, but an interesting hint of CO<br />
emission — the tell-tale sign of a thermal inversion layer high up in the atmosphere of this<br />
planet.<br />
Atmospheric characterization of the hot Jupiter Kepler-13b<br />
Avi Shporer — Caltech/JPL<br />
Kepler-13b (= KOI-13.01) is a unique transiting hot Jupiter. It is one of very few known<br />
short-period (1.76 day) planets orbiting a bright (V~10 mag) A-type star. Therefore, it is<br />
among the hottest and brightest planets currently known, motivating the study of its<br />
atmosphere. The availability of Kepler data allows us to measure the planet's occultation<br />
(secondary eclipse) and phase curve, in the optical, with very high precision, which we<br />
combine with occultations observed by the Warm Spitzer Mission at 3.6 micron and 4.5<br />
micron, and a ground-based occultation observation by the Wide-field Infra-Red Camera<br />
(WIRC), mounted on the Palomar 200 inch telescope, at the Ks band (~2.1 micron). Since<br />
the host star is the primary component of a visual binary system with ~1 arcsec separation,<br />
the two similar stars are fully blended in all our photometry. To correct the observed<br />
occultation depths for this dilution we modeled the stellar spectra, from the optical to the<br />
infrared, based on Keck/HIRES spectra that resolved the two stars. Our preliminary results<br />
indicate that the planetary atmosphere has a relatively high geometric albedo (Ag ~0.3)<br />
and a highly efficient heat distribution from the day side to the night side (epsilon ~0.9).<br />
This represents a deviation from previous studies in which the most highly irradiated hot<br />
Jupiters were found to have inefficient recirculation of energy from the day to the night<br />
sides. We also present revised atmospheric parameters for the planet-hosting star in this<br />
49
triple stellar system, and a revised planetary mass estimate based on the beaming effect<br />
and the tidal ellipsoidal distortion observed in the Kepler phase curve.<br />
Revealing Distant Worlds with Ground-Based Spectroscopy<br />
Kevin Stevenson — University of Chicago<br />
Uncovering the fundamental properties of exoplanetary atmospheres requires highprecision<br />
spectroscopy over a broad range of wavelengths. We are poised to make<br />
significant advances in our understanding of their composition and chemistry using<br />
currently-available, visible and near-infrared multi-object spectrographs attached to some<br />
of the largest telescopes in the world. With facilities such as Gemini, Keck, and Magellan,<br />
we are conducting an intensive survey of a representative sample of exoplanets to<br />
measure their transmission and dayside emission spectra. We will present high-quality<br />
spectra for several recently-observed exoplanets and discuss how these data constrain<br />
the molecular abundances, thermal profiles, and relevant chemistries of these planetary<br />
atmospheres.<br />
Updated Spitzer Secondary Eclipse Spectroscopy of HD189733b<br />
Kamen Todorov — ETH Zürich<br />
We analyze Spitzer Space Telescope time-series spectroscopy observations of HD<br />
189733b during 18 secondary eclipses at wavelengths between 5 and 14 microns. These<br />
measurements comprise the most extensive emission spectrum of any exoplanet to date.<br />
While some of these data sets have been analyzed previously by Grillmair et al. (2008),<br />
we examine eight of them for the first time. We remove the systematic effects from the<br />
spectral light curves using the most advanced techniques available, and measure the<br />
secondary eclipse depths as a function of wavelength. We use a modified version of a<br />
radiative transfer code by Richardson et al. (2003) to calculate three emergent spectrum<br />
models and compare our observational results with them, and with the best fit model<br />
(Burrows et al. 2008) adopted by Grillmair et al. in their earlier investigation. We can<br />
confidently exclude isothermal and gray atmospheres and confirm the water feature<br />
detected by Grillmair et al.<br />
Phase curves of close-in Kepler planets<br />
Vincent Van Eylen — Aarhus University!<br />
The Kepler satellite has provided a wealth of new data on transiting exoplanets. Its<br />
unprecedented precision allows for more than just analyzing the transit: for hot planets in<br />
an orbit of only a few days, the parts-per-million precision allows for the detection of<br />
planetary light throughout the full phase, as well as its absence during the secondary<br />
eclipse. For those tidally locked planets, the increase in received flux as we view more and<br />
more of the planet's day side allows us to make statements on the planetary reflection<br />
(albedo) and temperature. Measuring the depth of the occultation leads to estimates on<br />
the temperature of the (cold) planetary nightside. I present preliminary results on a<br />
comparative study of the sample of close in transiting exoplanets which were observed by<br />
Kepler.<br />
50
Water in the atmosphere of hot-Jupiter exoplanets<br />
Hannah Ruth! Wakeford — University of Exeter<br />
Using the Hubble Space Telescope’s WFC3 camera with an infrared low resolution grism,<br />
we observed a number of hot Jupiters from 1.1-1.7 µm, probing primarily the H2O<br />
absorption band at 1.4 µm. H2O is a key molecule for constraining hot-Jupiter<br />
atmospheres with the atmospheric C/O ratio playing a pivotal role in the relative H2O<br />
abundance. We present a variance in these hot Jupiter atmospheres with a strong H2O<br />
detection in the upper atmosphere of HAT-P-1b and new results from WASP-31b. The<br />
computed transmission spectra show a startling diversity in the observed abundance of<br />
H2O in the atmosphere of close-in giant planets allowing us to explore the nature of their<br />
relative environments.<br />
The 4.5 micron phase curve of HD 209458b!<br />
Robert Zellem — Lunar and Planetary Laboratory - University of Arizona!<br />
The hot Jupiter HD 209458b is one of the most favorable targets for full-orbit phase curve<br />
observations, as it is one of the brightest systems (V-mag = 7.65, K-mag = 6.308), has a<br />
large planet-to-star contrast, and offers a high signal-to-noise ratio and the ability to make<br />
high-precision measurements. This planet also serves as the archetype for a class of<br />
planets that have dayside temperature inversions; the differences between this class of<br />
planets and those lacking inversions (including HD 189733b) are currently not wellunderstood.<br />
Here we present the first full-orbit phase curve of HD 209458b observed with<br />
the Spitzer/IRAC 4.5 micron photometric band. Our data, which includes one primary<br />
transit and two secondary eclipses, was reduced with a pixel-mapping method to get within<br />
1.145 times the photon noise limit. We measure the brightness temperature of the<br />
observed phase curve. The results are modeled with radiative transfer models along with<br />
other primary transit and secondary eclipse data to determine the pressure level of the<br />
emissions. We then compare these results to predictions from global circulation models,<br />
including those where magnetic effects and thermal inversions are present in order to<br />
determine the effect that HD 209458b\s dayside temperature inversion has on its<br />
atmospheric circulation and chemistry.<br />
HOT JUPITERS: MODELS<br />
Effects of clouds on reflection properties of hot Jupiters!<br />
Nadine Afram — Kiepenheuer Institut für Sonnenphysik, Freiburg<br />
The presence of clouds in exoplanetary atmospheres may dramatically change their<br />
reflectivity properties. This can be detected during secondary eclipses and with the help of<br />
polarimetric techniques, independently of planet transits. Here, we model polarimetric<br />
phase curves and secondary eclipses for some very hot Jupiters with orbital periods<br />
shorter than 3 days (e.g., WASP-19b, HD189733b) using model atmospheres with and<br />
without clouds. We empirically adjust pressure-temperature profiles and the cloud<br />
composition and height and investigate how polarization and eclipse curves depend on<br />
atmosphere parameters. In particular, we consider such molecules and condensates as ,<br />
51
OH, H2, CO, CO2, CH4, NH3, MgO, MgSiO3, Mg2SiO4, Al2O3, etc. We compare our results with<br />
available polarimetric and photometric measurements for hot Jupiters.<br />
Testing radiative transfer schemes for use in global circulation models of hot<br />
Jupiters!<br />
David Skålid!Amundsen — University of Exeter!<br />
Several studies which have used adapted Global Circulation Models (GCMs) to interpret<br />
observations of hot Jupiters have now been published. Almost all of these studies involve<br />
simplified dynamical (e.g shallow water or primitive equations) and radiative transfer<br />
schemes (temperature forcing, grey or band-averaged absorption coefficients). We are<br />
adapting the UK Met Office GCM, the Unified Model, which solves the full 3D compressible<br />
Euler equations and includes a frequency dependent radiative transfer scheme (invoking<br />
the two-stream approximation and correlated-k method) for the study of hot Jupiters.<br />
We will discuss the adaptation of the radiative transfer scheme and the tests we have<br />
performed to verify its accuracy. By comparing to more accurate discrete-ordinate line-byline<br />
calculations we will demonstrate that this scheme yields fairly accurate fluxes and<br />
heating rates overall. In some cases, however, there are significant deviations, and we find<br />
the use of band-averaged absorption coefficients to be very inaccurate. Lastly, I will<br />
present some of the first results we have obtained after recoupling the dynamical core and<br />
radiative transfer schemes.<br />
An Open Source Python Thermochemical Equilibrium Abundances Code!<br />
Jasmina Blecic — University of Central Florida<br />
We present a Thermochemical Equilibrium Abundances code (TEA) that calculates the<br />
equilibrium abundances of the molecular species present at a given temperature and<br />
pressure in a planetary atmosphere. There are two approaches to calculating<br />
thermochemical equilibrium: by using equilibrium constants and reaction rates or by<br />
minimizing the free energy of the system. Although chemical equilibrium can be calculated<br />
almost trivially for several reactions present in the system, as the number of reactions<br />
increases, the number of equilibrium-constant relations becomes difficult to solve<br />
simultaneously. An advantage of the free-energy-minimization method is that each<br />
species present in the system can be treated independently, without specifying<br />
complicated sets of reactions. Therefore, just a limited set of equations needs to be<br />
solved. TEA is based on the Gibbs-free-energy minimization calculation, originally<br />
developed by White et al. (1958) and Eriksson (1971). The code is written entirely in<br />
Python and is available to the scientific community under an open-source license.<br />
VSTAR Models of a Hot Jupiter<br />
Kimberly Bott -- University of New South Wales<br />
Past analysis of HD 189733b's atmosphere has been a cause for some debate, with<br />
conflicting findings regarding polarized light, carbon dioxide and sodium abundances and<br />
the presence of a high altitude haze. I will present our model of HD 189733b's atmosphere<br />
using VSTAR (Versatile Software for Transfer of Atmospheric Radiation), a robust, line-byline,<br />
multiple scattering radiative transfer solution in a modular program, utilitizing its own<br />
chemical equilibrium model. Since the effective temperature of the planet is expected to be<br />
approximately 1100K, newly available high-temperature spectral line lists were used. The<br />
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planet’s dayside, terminator and reflected polarized light are modeled and compared to<br />
available data.<br />
Circumplanetary Jet Formation, Characteristics, and Observational Diagnostics<br />
Ian Dobbs-Dixon — University of Washington!<br />
Ubiquitous among multidimensional simulations of highly irradiated gas-giant planets is the<br />
development of circumplanetary jets in the equatorial region of the planet. These jets,<br />
many of which become supersonic, are the dominant dynamical feature, helping to shape<br />
all observable features and perhaps influencing the thermal evolution of the entire planet.<br />
However, observations of irradiated gas-giants suggest that not all planets form such jets.<br />
Despite their importance for interpreting observations, the precise physical mechanism for<br />
forming and sustaining jets remains an area of active research. We lay out a linear theory<br />
for the formation of these jets and compare our predicted behavior to results from<br />
multidimensional radiative-hydrodynamical simulations. We then further discuss a novel<br />
observational technique for detecting these jets during a single eclipse. A faster method of<br />
detecting a jet will allow for a much broader survey of systems, hopefully shedding light on<br />
the physical parameters of the system that help or hinder jet formation.<br />
Escape of Hydrogen from HD209458b!<br />
Justin!Erwin — University of Arizona!<br />
Recent modeling of the atmosphere of HD209458b has been used to interpret the Lymanline<br />
and other observations during transits. Koskinen et al. (2010) used a hydrostatic<br />
density profile in the thermosphere combined with the Voigt profile to estimate the Lymanalpha<br />
transit depths for an array of model parameters. A detailed photochemical-dynamical<br />
model of the thermosphere was developed by Koskinen et al. (2013a) and used to again<br />
estimate model parameters to fit not only the Lyman-alpha transits, but also the transits in<br />
the O I, C II and Si III lines (Koskinen et al., 2013b). Recently, Bourrier and Lecavelier<br />
(2013) modeled the escape of hydrogen from the extended atmospheres of HD209458b<br />
and HD189733b and used the results to interpret Lyman-alpha observations. They<br />
included acceleration of hydrogen by radiation pressure and stellar wind protons to<br />
simulate the high velocity tails of the velocity distribution, arguing that the observations are<br />
explained by high velocity gas in the system while Voigt broadening is negligible.<br />
In this work we connect a free molecular flow (FMF) model similar to Bourrier and<br />
Lecavelier (2013) to the results of Koskinen et al. (2013b) and properly include absorption<br />
by the extended thermosphere in the transit model. In this manner, we can interpret the<br />
necessity of the various physical processes in matching the observed line profiles.<br />
Furthermore, the transit depths of this model can be used to re-evaluate the atmospheric<br />
model parameters to determine if they need to be adjusted due to the existence of the<br />
extended hydrogen tail.<br />
Thor: A GPU code for simulating exoplanetry atmospheres<br />
Simon!Grimm — University of Zürich<br />
We present an implementation of a three-dimensional general circulation model (GSM),<br />
designed for simulating exoplanetary atmospheres, running fully parallel on Graphics<br />
Processing Units (GPU’s). The Code is developed for the <strong>Exoclimes</strong> Simulation Platform<br />
(ESP) and will be available as open source software. Thor solves the three dimensional<br />
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non hydrostatic Euler equations on a modified Yin-Yang grid, which consists of an<br />
equatorial belt and two polar caps, which are patched together using a fully conservative<br />
zonal interface algorithm, described by Wang (1995). The individual grids are solved with a<br />
horizontal explicit and vertical implicit (HEVI) finite difference scheme, where the vertical<br />
solution can be computed analytically. In this poster we present the implemented scheme<br />
and show as well results of the first tests, including a quantification of the conservation of<br />
energy, mass and momentum.<br />
Compared to other available CPU codes, Thor shows a speed-up of around one<br />
magnitude. Thor is written in Cuda C and runs on all Nvidia GPU's.<br />
The <strong>Exoclimes</strong> Simulation Platform!<br />
Kevin! Heng! — Center for Space and Habitability, University of Bern<br />
!<br />
The state of the art in performing 3D simulations of exoplanetary atmospheres centers<br />
around adapting GCMs (general circulation models), originally designed for the study of<br />
Earth. These Earth-centric tools suffer from fundamental shortcomings, including Earthcentric<br />
assumptions, the inability to model shocks, the exclusion of magnetic fields and the<br />
treatment of radiative transfer as if the atmosphere is static. We offer an alternative<br />
perspective: the design and development of a set of publicly available, theoretical and<br />
simulational tools for the general exoplanet community, partly to combat the growing "black<br />
box" culture in our field. I give a brief and broad review of the <strong>Exoclimes</strong> Simulation<br />
Platform (ESP), focusing on the GCMs and radiative transfer tools that are currently in<br />
development. I will also explain our decision to build the ESP entirely on GPUs, which<br />
gives our open-source tools a speed-up of at least an order of magnitude (two orders of<br />
magnitude for radiative transfer). I will describe how we plan to involve the community via<br />
a web portal (www.exoclime.org), which includes a Facebook page for soliciting feedback.<br />
VIPER: Toward a universal model for planetary climate<br />
Nicolas Iro — University of Hamburg<br />
With the discovery of an increasing number of planets outside our Solar System, we are<br />
becoming familiar with physical conditions and atmospheric compositions that span a<br />
much wider range that what covered by the planets of our solar system. Non-exhaustive<br />
examples are equilibrium temperatures ranging from 50K (Neptune) to over 3000K<br />
(WASP-12b, WASP18b); orbital eccentricity, ranging from 0-0.1 for solar system planets<br />
(except Mercury) and circularized close-in hot Jupiters to e = 0.93 (HD80606b). Other<br />
parameters relevant for atmospheric dynamical features are also quite diverse: the Rhines<br />
length and Rossby length are, e.g., much smaller than the planet radii for Solar-System<br />
planets, while they are comparable to the planetary radii for hot Jupiters and Neptunes,<br />
meaning that in the latter case typical circulation features are global. It seems timely and<br />
urgent to try to frame in a common framework our understanding of such a large variety of<br />
atmospheric conditions. We will present VIPER, the Versatile Interactive PlanetSimulator<br />
for Extrasolar Research. This project, under development, aims at developing the Planet<br />
Simulator, an already flexible climate model to a new level of modularity. In the next phase<br />
of the implementation, we will remove all parameterization pertaining to Earth, allowing for<br />
instance to study any planetary rotation rate and add a simple yet precise radiative<br />
scheme based on the k-distribution coefficients. This will allow us to model the climate on<br />
a variety of planetary conditions from early Mars to Super-Earths.<br />
54
Modelling of the Emission Spectrum of WASP-19b<br />
Lucyna Kedziora-Chudczer — University of New South Wales<br />
The VSTAR radiative transfer code was used to model the emission spectrum of the one<br />
of the most irradiated hot-Jupiters, WASP-19b. We examined models with different<br />
pressure-temperature profiles and C/O abundances ratios. We find that models with<br />
carbon enrichment above solar match the available data best. We also included upperatmosphere<br />
haze of varied particle sizes and find that particles
ongoing. This will help us understand, for given circumstances, how a planetary magnetic<br />
field could alter the wind structure on hot Jupiters and its effects on day-night temperature<br />
variations and planetary radii.<br />
Extended ionospheres on extrasolar giant planets!<br />
Tommi! Koskinen — University of Arizona<br />
Recent work on close-in extrasolar giant planets (EGPs) raises the possibility that their<br />
atmospheres are significantly affected by ion drag and Joule heating arising from thermal<br />
ionization of their atmospheres (e.g., Cho 2008, Batygin et al. 2010, Perna et al. 2010a,b).<br />
It is unclear, however, if large scale current systems are supported in the relatively weakly<br />
ionized atmospheres of close-in EGPs. We explore thermal ionization and photoionization<br />
of EGP atmospheres, and use the results to constrain the electrodynamic regimes at<br />
pressures ranging from 1 bar to the escaping thermosphere. In line with planetary<br />
atmospheres in the solar system, we find that the coupling of the ions to the neutral<br />
atmosphere is important at all pressure levels. Assuming a magnetic field similar to that of<br />
Jupiter, we find that both the electrons and ions are collisionally coupled to the neutrals<br />
below the 0.1-1 mbar level, but significant ion drag and Joule heating are possible at<br />
pressures lower than this. The conductivities that we calculate, however, imply that the<br />
upper atmospheres of close-in EGPs occupy a regime closer to the solar chromosphere<br />
than planetary ionospheres in the solar system — even at relatively high pressures in the<br />
stratosphere. Nevertheless, the generalized Ohm’s law for partly ionized media is still<br />
valid and we explore the resulting current systems based on this assumption.<br />
3-D modeling of atmospheric escape from Hot Jupiters !<br />
Alain Lecavelier — Institut d'Astrophysique de Paris!<br />
Transit observations in the Lyman-alpha line of the hot Jupiters HD209458b and<br />
HD189733b revealed strong signatures of neutral hydrogen escaping the planet's<br />
atmospheres. We will present our 3D particle model of the dynamics of the escaping<br />
atoms, which is used to calculate theoretical absorption profiles, and can be directly<br />
compared to the observations to constrain the physical conditions at high altitudes in the<br />
exosphere (such as the escape rate and the stellar ionizing flux). Recently, this model has<br />
also been used to interpret the observation of neutral magnesium probing the<br />
thermosphere-exosphere transition region. Simulations show the major influence of the<br />
stellar radiation pressure on the structure of the escaping gas cloud, which can also be<br />
shaped by stellar wind interactions, planetary gravity and self-shielding effects. This results<br />
in spectro-temporal variations of the absorption profile that could be used to further<br />
characterize the atmospheric escape. On a wider scale, our model can be used as a<br />
predictive tool to identify evaporating exoplanets with high-significance absorption<br />
features.<br />
Non-hydrostatic, deep-atmosphere hot Jupiter climate models<br />
Nathan Mayne — University of Exeter!<br />
We present results for the climate of hot Jupiter HD209458b derived using a global<br />
circulation model (GCM) which, using the same numerical scheme, can solve both the full<br />
unsimplified dynamical equations for a rotating atmosphere, as well as including increasing<br />
simplification to these equations. Our results show that the bulk atmospheric flow is largely<br />
56
obust to the canonical simplifications if short integration times and small vertical domains<br />
are used (i.e. shallow weather layers). However, for longer integrations and models<br />
incorporating a “deeper” (i.e. larger in vertical extent) atmosphere such simplifications to<br />
the dynamical equations produce different flows. We also explore the changes to the<br />
driving, or pumping, mechanisms for the large scale flow features in the atmosphere under<br />
improvements to the dynamical description. We have also adapted a more complete<br />
radiative transfer scheme for the physical conditions of hot Jupiters and I will outline<br />
progress coupling this to the dynamical code.<br />
Chemical disk evolution and element abundances of gas giants<br />
Peter Woitke — St. Andrews University!<br />
We discuss the chemical pre-conditions for planet formation, in terms of gas and ice<br />
abundances as function of time and position in a protoplanetary disk. Considering the<br />
standard core-accretion model for planet formation, the overwhelming majority of the mass<br />
of the gas giant will only be accreted onto the proto-planet in a final rapid run-away phase,<br />
using up the remaining gas in the planet feeding zone. This gas will contain only traces of<br />
refractory elements, and possibly only little amounts of elements like C, N and O, which<br />
may have frozen out as ices before. ProDiMo protoplanetary disk models are used to<br />
predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays<br />
play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water<br />
which freezes out quickly. Therefore, the carbon-to-oxygen ratio C/O in the gas phase is<br />
found to gradually increase with time in the disk, in a region bracketed by the water and<br />
CO ice-lines. C/O is found to exceed unity after about 7 Myrs, scaling with the cosmic ray<br />
ionization rate assumed.<br />
YOUNG GIANT PLANETS AND BROWN DWARFS<br />
A radiative-convective equilibrium model for young giant exoplanets: Comparison<br />
with observations and other existing models<br />
Jean-Loup Baudino — LESIA, Observatoire de Paris!<br />
We developed a radiative-convective equilibrium model for young giant exoplanets. Input<br />
parameters are the planet's surface gravity (g), effective temperature (Teff) and elemental<br />
composition. Under the additional assumption of thermochemical equilibrium, the model<br />
predicts the equilibrium temperature profile and mixing ratio profiles of the most important<br />
gases. Opacity sources include the H2-He collision-induced absorption and molecular lines<br />
from H2O, CO, CH4, NH3, VO, TiO, Na and K. Line opacity is modeled using k-correlated<br />
coefficients pre-calculated over a fixed pressure-temperature grid. Absorption by iron and<br />
silicate cloud particles is added above the expected condensation levels with a fixed scale<br />
height and a given optical depth at some reference wavelength. Scattering is not included<br />
at the present stage. Model predictions are compared with the existing photometric<br />
57
measurements of Planet Beta Pictoris b and Kappa And b in the J, H, Ks, L', NB 4.05, M'<br />
bands and with spectroscopic observations of the HR8799 planetary system to constrain<br />
Teff and g. Finally, our results are compared with those derived from other existing models.<br />
This model will be used to interpret future photometric and spectroscopic observations of<br />
exoplanets with SPHERE, mounted at the VLT with a first light expected in 2014.<br />
Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting<br />
Brown Dwarf KELT-1b!<br />
Thomas Beatty — Ohio State University!<br />
KELT-1b is a highly-irradiated, highly-inflated, 27 Jupiter-mass object transiting a bright<br />
(V=10.8) F5V star with a period of 1.2 days. KELT-1b offers a unique opportunity to study<br />
the atmosphere of a brown dwarf with known mass, radius, and approximate age, in a<br />
radiation environment similar to hot Jupiters. We present and discuss secondary eclipse<br />
observations of this system taken using the Spitzer Space Telescope and from the ground.<br />
We measure secondary eclipse depths of 0.196+/-0.01% at 3.6 μm and 0.200+/-0.012% at<br />
4.5 μm, corresponding to a fairly grey color of [3.6]-[4.6] = 0.07+/-0.11. Using four separate<br />
ground-based light curves, we find suggestive evidence for the secondary eclipse in the z<br />
band with a depth of 0.046+/-0.023%. These observations represent the first constraints<br />
on the atmospheric dynamics of a highly-irradiated brown dwarf, and are interesting in the<br />
context of both the atmospheres of irradiated giant planets at high surface gravity, and the<br />
atmospheres of brown dwarfs that are dominated by external, rather than internal, energy.<br />
In particular, as compared to objects of similar temperature, KELT-1b has a [3.6]-[4.6] color<br />
that is similar to isolated brown dwarfs, in contrast to lower surface gravity exoplanets,<br />
which tend to have redder colors.<br />
Critically testing atmospheric models with benchmark brown dwarfs<br />
Ben Burningham — University of Hertfordshire<br />
The current generation of wide-field surveys is probing such a volume that significant<br />
numbers of brown dwarfs are being identified as rare wide common proper motion binary<br />
companions to higher mass stellar primaries. If such systems are formed in the same<br />
manner as similarly separated stellar binaries then it follows that the composition and age<br />
of the primary may be used to infer the same properties for the low-mass companion,<br />
making such systems attractive calibrators for substellar and exoplanetary atmospheric<br />
(spectral) model grids. They are thus referred to as benchmark systems. In this<br />
contribution, I will discuss recent results from our search for substellar benchmarks,<br />
focusing on how the emerging grid of calibrated atmospheres can be used to provide new<br />
insights into the strengths and deficiencies of differing model approaches, and highlighting<br />
how benchmark systems have revealed that metallicity is as important as effective<br />
temperature for determining the SED of cool substellar objects. Finally, I will explore how<br />
the potential of benchmark brown dwarfs for breaking observational degeneracies can be<br />
realised to solve key science goals in exoplanetary science.<br />
Doppler imaging of a Nearby Cloudy Brown Dwarf<br />
Ian Crossfield — MPIA<br />
Brown dwarfs provide easily-observable analogues to young extrasolar planets with similar<br />
temperatures and radii but lower masses. Brown dwarfs are the first substellar objects for<br />
58
which cloud-induced temporal variability has been observed, but so far the<br />
characterization of these complex & dynamic atmospheres has been limited to lowresolution<br />
spectroscopy and photometry. We will present Doppler Imaging of a brown<br />
dwarf’s surface using high-resolution near-infrared spectroscopy. Future such observations<br />
will track the formation, evolution, and breakup of global weather patterns, and will provide<br />
revolutionary new benchmarks against which to compare global circulation models of<br />
cloudy substellar objects.<br />
Ionisation regimes structuring planetary atmospheres!<br />
Christiane Helling — University of St Andrews!<br />
The steady increase of the sample of extrasolar planets broadens our knowledge and at<br />
the same time, reveals our lack of understanding fundamental processes. For example<br />
does the habitability of a planet depend, amongst other things, on how much and which<br />
radiation reached the ground, how clouds form and which effect clouds have on the<br />
composition and on the electric state of the ambient gas from which they form.<br />
We have studied the formation of mineral clouds on planetary atmospheres by a kinetic<br />
approach which allows us to predict the size distribution and material composition of the<br />
cloud particles. These results have been used to study if such clouds can be charged and<br />
under which conditions an electric field breakdown, such as lightning or other transient<br />
luminous events, may occur. Our results suggest that different intra-cloud discharge<br />
processes dominate at different heights inside a cloud, and that the atmospheric volume<br />
affected by large-scale lightening discharges is larger in Brown Dwarfs than in planetary<br />
atmospheres. We demonstrate how different ionisation processes suggest that planets and<br />
brown dwarfs have stratified ionised atmospheres.<br />
Atmospheric cloud models from brown dwarfs to exoplanets<br />
Derek Homeier -- Centre de Recherche Astrophysique de Lyon/ENS-Lyon!<br />
State-of-the-art theoretical models of low-mass stars and brown dwarf atmospheres aim at<br />
a physically and chemically consistent simulation, generally evolving from the assumptions<br />
of hydrostatic and radiative equilibrium as well as a chemical equilibrium composition<br />
based on given input abundances. In further refinement more complex phenomena such<br />
as atmospheric dynamics and departures from chemical equilibrium by advection,<br />
photochemistry or condensate formation can be considered. This approach has allowed<br />
model grids based on a minimal set of parameters to reproduce observed properties of<br />
substellar objects with considerable success. Most important among these is without doubt<br />
the role of cloud opacity throughout the sequence from late-type stars to the coolest brown<br />
dwarfs known to date. I will present the results of the PHOENIX Settling models, which<br />
successfully describe the formation of different cloud types, from iron and silicate dust<br />
dominating in L dwarfs over sulphides and halides that become relevant in cooler T dwarfs,<br />
to the appearance of water ice and colder condensates in the latest Y dwarfs. These<br />
models can often be applied with little modification to lower mass objects such as directly<br />
imaged gas giants, highlighting the effects of lower gravity on atmospheric chemistry and<br />
cloud formation. However, as one explores more fully the domain of exoplanet<br />
atmospheres, increased complexity like global transport triggered by irradition, and<br />
atmospheric chemistry no longer based on scaled-solar compositions come into play.<br />
Consequently the direct retrieval of atmospheric properties from observed data, is often<br />
preferred in these cases, but with only few data points to constrain the models, may<br />
struggle to produce a unique and physically realistic solution. I shall show here how our<br />
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models can still be applied in this context to hot Neptunes and super-Earths to place<br />
constraints on atmospheric properties using the most recent transit spectroscopy results.<br />
New insights on beta Pictoris: discovery of two different populations<br />
Flavien Kiefer — Institut d'Astrophysique de Paris!<br />
High-resolution spectroscopic observations of beta Pictoris made with HARPS bring new<br />
information on the exocomets falling onto the star (FEB scenario). With more than a<br />
thousand spectra gathered between 2003 and 2011, we have around 6000 variable<br />
absorptions detected. Using this huge catalogue of events we achieved an unprecedented<br />
statistical and temporal study of beta Pic comets. We will present the results of this<br />
statistial analysis, and display the evidence that allowed us to discover two very different<br />
populations of comets in this young planetary system.<br />
Magnetic fields on L-type brown dwarfs!<br />
Oleksii Kuzmychov — Kiepenheuer-Institut für Sonnenphysik<br />
Several rapidly-rotating L-type dwarfs exhibit transient but periodic radio pulses that are<br />
possibly driven by electron-cyclotron maser (e.g., Hallinan et al. 2007, 2008). For this<br />
mechanism to work, a few kG magnetic field is required. In order to examine whether<br />
these objects possess such a strong magnetic field, we model polarized spectra of L-type<br />
brown dwarfs including transitions in diatomic molecules, such as CrH, FeH, and TiO. We<br />
compare these synthetic spectra with full Stokes spectra of two brown dwarfs measured at<br />
several rotational phases using the low-resolution spectropolarimeter LRIS at the Keck<br />
Observatory in August 2012. We are able to constrain the magnetic field strength in these<br />
objects and discuss implications of our results.<br />
Spectral Retrieval Analysis of the Directly Imaged exoplanets around HR 8799<br />
Jae-Min Lee — University of Zurich<br />
The direct-imaged exoplanets around HR 8799 are photometrically distinct from their<br />
parent star. Spectroscopic measurements along with photometric points between 1 and 5<br />
µm provide vital information on the thermal and chemical structure of the atmosphere,<br />
which have never been achieved from transiting exoplanets. However, it is still mysterious<br />
that the characteristics of the atmosphere show a mixture of brown dwarf and gas giant<br />
features, calling its radius, surface gravity and mass into a question. Here, we perform<br />
inverse modelling by exploiting an optimal estimation retrieval technique and sweep the<br />
parametrized radius and surface gravity space with phenomenological cloud scenarios.<br />
Unlike previous approaches, in which the cloud models are rather sophisticated, we<br />
minimise the number of cloud parameters, e.g., mono-disperse cloud particle size and<br />
optical depth of cloud. We find that the identity of the cloud material gives a non-detectable<br />
effect to our results because the refractive indices of most of materials plausible in this<br />
class of atmosphere are not distinguishable at these wavelengths. Also, we report physical<br />
properties of these planets, such as radius, surface gravity and mass, which can provide<br />
useful constraints for building its formation scenario.<br />
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A Comparison of Exoplanet Atmospheric Retrieval Techniques<br />
Michael Line!— University of California Santa Cruz<br />
Secondary eclipse spectra allow us to infer the temperatures and compositions of<br />
exoplanet atmospheres. A variety of statistical approaches exist to determine the most<br />
probable set of temperatures and compositions such as Markov Chain Monte Carlo and<br />
Optimal Estimation. I will give an overview of these approaches in the context of the<br />
Bayesian formalism and discuss the similarities and differences in their derived posterior<br />
probabilities. I will show in which regimes optimal estimation is appropriate and in which<br />
regimes MCMC approaches are necessary. Finally, as a side, I will discuss the potential<br />
pitfalls of statistical determinations of the atmospheric C/O ratio.<br />
Young and Planetary-Mass: Connecting Low-Gravity Field Brown Dwarfs and<br />
Directly Imaged Gas-Giant Planets!<br />
Michael Liu — University of Hawaii, Institute for Astronomy!<br />
Direct detections of young gas-giant exoplanets and recent identification of very young<br />
field brown dwarfs are strengthening the observational link between the exoplanet and<br />
brown dwarf populations, enriching our understanding of both classes of objects. However,<br />
studies to date have typically focused on individual discoveries. We present a large<br />
comprehensive study of the youngest field brown dwarfs, comprising both previously<br />
known objects and our new discoveries from the Pan-STARRS-1 wide-field survey. These<br />
objects have physical properties that overlap young gas-giant planets and thus are<br />
promising analogs for studying exoplanet atmospheres at high S/N and spectral resolution<br />
down to ~5 Jupiter masses. We combine high-quality spectra and parallaxes to study their<br />
spectral energy distributions, luminosities, temperatures and ages. We demonstrate that<br />
the peculiar IR colors and magnitudes of the planets around 2MASS J1207-39 and HR<br />
8799 do occur in some young brown dwarfs, but these properties do not have a simple<br />
correspondance with age. We find that young field brown dwarfs can have unusally low<br />
temperatures (but they are not underluminous, as often claimed). To help provide a<br />
reference for upcoming extreme-contrast imaging surveys, we establish a grid of spectral<br />
standards and benchmarks, based on membership in nearby young moving groups, in<br />
order to calibrate gravity (age) and temperature diagnostics in near-IR spectroscopy.<br />
Finally, we use our data to critically examine the possibility that free-floating objects and<br />
companions may share different evolutionary histories, thereby complicating the "brown<br />
dwarf-exoplanet connection”.<br />
MagAO/VisAO Optical Imaging of beta Pictoris b: A Comparative Study of<br />
Exoplanets and Brown Dwarfs!<br />
Jared! Males — University of Arizona<br />
We used the Magellan AO system's visible wavelength diffraction limited camera, VisAO,<br />
to image the ~10 Jupiter mass exoplanet beta Pictoris b. This is the first ground-based<br />
direct image of an exoplanet at wavelengths less than 1 micron. Using our photometry,<br />
combined with existing JHK measurements, we compare beta Pic b to field brown dwarf<br />
spectra. Our analysis yields a rigorous empirical determination of the planet's spectral<br />
type, and through this an estimate of effective temperature. Our photometry highlights the<br />
extreme diversity amongst the directly imaged extrasolar giant planets and both field and<br />
companion brown dwarfs, yet points to remarkable similarities in formation and evolution<br />
despite this diversity.<br />
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Comprehensive Results from the Weather on Other Worlds Spitzer Campaign:<br />
Photometric Variability Is Ubiquitous on L and T Dwarfs<br />
Stanimir Metchev — Western University!<br />
I will present the first comprehensive results from the ""Weather on Other Worlds"" Spitzer<br />
Exploration Science program: the most precise and comprehensive study of cloud-induced<br />
photometric variability in L and T dwarfs. We observe that 45% of L3-T8 dwarfs are<br />
variable, with amplitudes between 0.2%-5% at 3.6 and 4.5 micron. Contrary to<br />
expectations, the variability fraction is independent of spectral type, suggesting that cloud<br />
phenomena are present in ultra-cool dwarfs over the entire 700-2000 K effective<br />
temperature range surveyed in our program, and likely at even cooler temperatures.<br />
Combined with spin-axis and cloud/hole viewing geometry considerations, our findings<br />
indicate that cloud-induced variability is present on virtually all L3-T8 dwarfs. If the<br />
detected variability is caused by single large storms, rather than by multiple smaller ones,<br />
the measured amplitudes and temperature contrasts indicate that these features cover<br />
between 8%-40% of the visible disks of brown dwarfs. That is, atmospheric storms with<br />
sizes between approximately half to twice that of the Great Red Spot on Jupiter are<br />
ubiquitous on 700-2000 K brown dwarfs.<br />
Water Clouds in Y Dwarfs and Exoplanets!<br />
Caroline Morley — University of California Santa Cruz!<br />
A major frontier in the fields of directly imaged planets is finding and characterizing the<br />
coolest known objects. For planets with effective temperatures below about 450 K, it has<br />
long been known that water clouds will form and shape the infrared spectra of these<br />
objects. However, no previous modeling studies have systematically shown the effect that<br />
water clouds will have on the spectra of these cold planetary-mass objects. Within 1-2<br />
years, GPI and SPHERE will be able to directly image and characterize planets down to<br />
~300 K, so the time is right to better understand cool atmospheres dominated by water<br />
clouds.<br />
Cold brown dwarfs will also contain water clouds and they provide a test-bed for our new<br />
generation of cloudy atmosphere models. The newly-proposed spectral type Y includes<br />
brown dwarfs cooler than about 500 K, many of which will have water clouds. Over a<br />
dozen Y dwarfs have now been discovered and are beginning to be characterized;<br />
followup studies by various groups aim to measure their spectra, monitor them for<br />
variability, and measure their parallaxes. The models presented here will allow us to<br />
determine the physical properties of the Y dwarfs and allow us to compare the brown dwarf<br />
population to directly-imaged planets as they are discovered.<br />
Here we present a study of clouds in objects that bridge the gap between brown dwarfs<br />
and solar-system planets, with effective temperatures from 200 to 500 K. We present<br />
results for both planetary-mass objects and for Y dwarfs and compare models to available<br />
Y dwarf spectra to test their validity. We make predictions for the spectra, colors, and<br />
magnitudes of young giant planets and the Y dwarf population. We also predict the level of<br />
variability expected in the near- and mid-infrared.<br />
Direct imaging of exoplanets: Remote sensing of planetary systems and processes<br />
Katie Morzinski — University of Arizona!<br />
Beta Pictoris hosts a planet at sub-arcsecond separation, detected via high-contrast<br />
imaging. We observed Beta Pic b at first-light of the new Magellan adaptive optics<br />
62
instrument "MagAO" in December 2012, simultaneously with our visible-light and infrared<br />
cameras. I will present my MagAO imaging data of Beta Pic b at 5 passbands, providing a<br />
fuller picture of the planet's spectral energy distribution. This broad wavelength coverage<br />
will be crucial to determining the energy balance of new exoplanets as improved AO<br />
technology allows direct imaging to probe closer separations and lower masses. MagAO is<br />
unique in achieving diffraction-limited imaging from 0.6-5 microns, and will be vital to<br />
characterizing these planetary systems.<br />
The Mid-Infrared Properties of Directly-Imaged Exoplanets<br />
Andrew Skemer — University of Arizona!<br />
Self-luminous exoplanets emit the majority of their photons in the mid-infrared (>3 micron).<br />
However, the difficulty of working in the thermal infrared from the ground has precluded the<br />
detailed studies of exoplanets at these longer wavelengths.<br />
Using the low-emissivity adaptive optics systems at the LBT and Magellan, we present 6<br />
new photometric points on the HR 8799 planets and 1 new photometric point on 2M1207<br />
b. These data probe the 3-4 micron region where previous studies have found a 1-2<br />
magnitude discrepancy between their atmospheres and field brown dwarfs. For the HR<br />
8799 planets, we find a shallow 3-4 micron slope with only a hint of possible absorption in<br />
the methane 3.3 micron fundamental absorption band (possibly indicating the presence of<br />
patchy clouds). For 2M1207 b we find a similar if more extreme behavior, with no sign of<br />
methane absorption.<br />
The study has implications for understanding the broad properties of extrasolar giant<br />
planets, and suggests that future mid-infrared direct-imaging searches (particularly JWST)<br />
may need to reconsider their search strategy.<br />
A large near-IR photometric monitoring survey of 69 ultracool L &T brown dwarfs<br />
Paul Anthony!Wilson — University of Exeter<br />
As the brown dwarf atmosphere cools through the L-T spectral sequence a rapid shift from<br />
the red to the blue colours are observed across the L-T type transition. This shift in colour<br />
happens across a narrow effective temperature range, which is hard for 1-D atmosphere<br />
models to currently reproduce. Patchy clouds might be the explanation of the rapid change<br />
in colour observed over a narrow temperature range. The consequence of patchy clouds<br />
would be variations in the observed flux due to the rotation and evolution of the clouds.<br />
I will present the results from our large near-IR photometric monitoring campaign which<br />
covers 69 ultracool L & T type brown dwarfs. In particular I will discuss the frequency and<br />
amplitude of variability across the different spectral types highlighting that our survey finds<br />
new large amplitude variables across the L - T spectral range showing no preference for<br />
the transition. I will also talk about observing variability at the much cooler T-Y transition.<br />
63
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© Rough Guides / Map published on http://Switzerland.isyours.com<br />
cáäáëìê<br />
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The conference was organised with the<br />
support of the University of Exeter<br />
64