Exoclimes_Conference_booklet1

A Comparison of Exoplanet Atmospheric Retrieval Techniques
Michael Line!— University of California Santa Cruz
Secondary eclipse spectra allow us to infer the temperatures and compositions of
exoplanet atmospheres. A variety of statistical approaches exist to determine the most
probable set of temperatures and compositions such as Markov Chain Monte Carlo and
Optimal Estimation. I will give an overview of these approaches in the context of the
Bayesian formalism and discuss the similarities and differences in their derived posterior
probabilities. I will show in which regimes optimal estimation is appropriate and in which
regimes MCMC approaches are necessary. Finally, as a side, I will discuss the potential
pitfalls of statistical determinations of the atmospheric C/O ratio.
Young and Planetary-Mass: Connecting Low-Gravity Field Brown Dwarfs and
Directly Imaged Gas-Giant Planets!
Michael Liu — University of Hawaii, Institute for Astronomy!
Direct detections of young gas-giant exoplanets and recent identification of very young
field brown dwarfs are strengthening the observational link between the exoplanet and
brown dwarf populations, enriching our understanding of both classes of objects. However,
studies to date have typically focused on individual discoveries. We present a large
comprehensive study of the youngest field brown dwarfs, comprising both previously
known objects and our new discoveries from the Pan-STARRS-1 wide-field survey. These
objects have physical properties that overlap young gas-giant planets and thus are
promising analogs for studying exoplanet atmospheres at high S/N and spectral resolution
down to ~5 Jupiter masses. We combine high-quality spectra and parallaxes to study their
spectral energy distributions, luminosities, temperatures and ages. We demonstrate that
the peculiar IR colors and magnitudes of the planets around 2MASS J1207-39 and HR
8799 do occur in some young brown dwarfs, but these properties do not have a simple
correspondance with age. We find that young field brown dwarfs can have unusally low
temperatures (but they are not underluminous, as often claimed). To help provide a
reference for upcoming extreme-contrast imaging surveys, we establish a grid of spectral
standards and benchmarks, based on membership in nearby young moving groups, in
order to calibrate gravity (age) and temperature diagnostics in near-IR spectroscopy.
Finally, we use our data to critically examine the possibility that free-floating objects and
companions may share different evolutionary histories, thereby complicating the "brown
dwarf-exoplanet connection”.
MagAO/VisAO Optical Imaging of beta Pictoris b: A Comparative Study of
Exoplanets and Brown Dwarfs!
Jared! Males — University of Arizona
We used the Magellan AO system's visible wavelength diffraction limited camera, VisAO,
to image the ~10 Jupiter mass exoplanet beta Pictoris b. This is the first ground-based
direct image of an exoplanet at wavelengths less than 1 micron. Using our photometry,
combined with existing JHK measurements, we compare beta Pic b to field brown dwarf
spectra. Our analysis yields a rigorous empirical determination of the planet's spectral
type, and through this an estimate of effective temperature. Our photometry highlights the
extreme diversity amongst the directly imaged extrasolar giant planets and both field and
companion brown dwarfs, yet points to remarkable similarities in formation and evolution
despite this diversity.
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