Neutrinos from supernovae

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Neutrinos from supernovae

Neutrinos from supernovae Gravitational collapse Observations of SN1987A What could be learnedabout neutrinos"From neutrinos.....". DK&ER,lecture 10


Natural sources of neutrinosat 10 kpci.e. Galaxycenter"From neutrinos.....". DK&ER,lecture 10


Previous Supernovae observed inour GalaxyThe remnants of thesupernova thatTycho Brahe observedin 1572- still scorching- 10 million °C hot.The most recent SNvisible with the bare eyewas observed by Keplerin 1604"From neutrinos.....". DK&ER,lecture 10


Previous Supernovae observed inour GalaxyThe most recent SNvisible with the bare eyewas observed by Keplerin 1604yellow – Hubble (visible)red – Spitzer (infrared)green/blue – Chandra (rtg)"From neutrinos.....". DK&ER,lecture 10


Supernova Remnant Puppis Ainsert:- a small source ofrtg emission- probably a young- neutron star running awaywith velocity of 960km/s"From neutrinos.....". DK&ER,lecture 10


Previous Supernovae observed inour GalaxyOnly 8 supernovae have been observed in our Galaxy:Chinese records: 185, 386, 392 and 1006Later: 1054, 1181, 1572, 1604However all of them were relatively close to solar system.More distant SN are invisible – hidden by interstellar gasCurrently many SNs are observed in other gallaxies"From neutrinos.....". DK&ER,lecture 10


Supernova 1987AFeb 1984On Feb 23, 1987 a supernova was observed optically in the Large MagellanicCloud at a distance of 170 000 light years (50 kpc)At that time 2 large underground detectors searched for proton decays:Kamiokande and IMB. They inspected their signals and found4 hours earlier......"From neutrinos.....". DK&ER,lecture 10Mar 8, 1987


Detector IMB"From neutrinos.....". DK&ER,lecture 10


Observations of SN1987AIMB (Irvine-Michigan-Brookhaven)Raw dataAfter standard analysisrejecting atmospheric muons"From neutrinos.....". DK&ER,lecture 10


Neutrinos from Supernova 1987A inKamiokandeUniversaltimeon Feb23,1987"From neutrinos.....". DK&ER,lecture 10Neutrinos arrived 3-4hours earlier thanphotons because photonscould not get throughthe outer layers of SNbefore they thinnedenough.


IMBevents"From neutrinos.....". DK&ER,lecture 10


Observations of neutrinos from SN 1987AIMB Kamiokande Baksan LSDLocation Ohio,US Japan Russia France(Mont Blanc)Detector type water Cerenkov liquid scintillatorDetector mass 6800 2140 200 90(tons)Threshold(MeV) 19 7.5 10 5Number of events 8 11 5 ???Time of 1st 7:35:41 7:35:35 7:36:12 2:52:37event (UT)Absolute time 0.05 60 +2 0.002accuracy (sec) -54"From neutrinos.....". DK&ER,lecture 10


Neutrinos from Supernovae"From neutrinos.....". DK&ER,lecture 10


Stellar evolution"From neutrinos.....". DK&ER,lecture 10


Road to gravitational collapseMain thermo-nuclear reactions:Reaction Ignition temp.(millions K)4 1 H--> 4 He 103 4 He--> 8 Be + 4 He--> 12 C 10012C + 4 He--> 16 O2 12 C--> 4 He + 20 Ne 60020Ne + 4 He-->n + 23 Mg2 16 O--> 4 He + 28 Si 15002 16 O-->2 4 He + 24 Mg 40002 28 Si--> 56 Fe 6000When mass of the iron core exceeds1.4 solar masses the gravitation wins."From neutrinos.....". DK&ER,lecture 10gravitational collapse


Stellar evolutionInterplanetarynebulaGravitation energy is transformedinto heat; a gas-dust cocoon forms.NeutronStarBlackDwarfProtostarStellar wind carries away a fraction of mass.Fusion reactions start changing H into He, ahydrostatic equilibrium sets in..A large, dense, cool nebula (up to 10 6 M o , temp.~10 K)SNA gravitating matter condensation grows to~10-100 M oWhiteDwarfStarM ~Red Super-GiantRed GiantEnergy supply is depleted, radiation pressuredecreases. Stellar core contracts, its temperaturegrows, igniting hydrogen in the envelope. New energysupply leads to expansion of external layers.M ~M ~ 8MIncrease of surface with aconstant energy production rateleads to decreased power andenvelope temperature.BlackHoleM >> Stellar core contracts, temperature rises, makingpossible nuclear fusion of heavier elements."From neutrinos.....". DK&ER,lecture 10


Stellar Evolution"From neutrinos.....". DK&ER,lecture 10


StellarDimensions1. White dwarf2. Red dwarf3. Sun4. Red Giant5. Blue Giant"From neutrinos.....". DK&ER,lecture 10


Stellar Evolution"From neutrinos.....". DK&ER,lecture 10


Stellar evolutionsInitial star mass 30 10 3 1 0.3(in solar masses)Luminosity (sun=1) 10000 1000 100 1 0.004(during principal sequence)Livetime during princ. seq. 0.06 0.1 0.3 10 800(in billion years)Livetime as red giant 0.01 0.03 0.10 0.30 0.80(billions of years)Nuclear reactions stop at iron silicon oxygen carbon heliumFinal fate SN SN planetary solar solarnebula wind windEjected mass 24 8.5 2.2 0.3 0.01(in solar masses)Nature of final state black neutron white dwarfs (all 3)hole starMass of final state 6 1.5 0.8 0.7 0.3density (g/cm3) 5x10 14 3x10 15 2x10 7 1x10 7 1x10 6"From neutrinos.....". DK&ER,lecture 10


Gravitational Collapse"From neutrinos.....". DK&ER,lecture 10


Neutrinos from Supernovae• 56 Fe has maximum binding energyno more fusion and no moreheat production• When a core of iron reaches a Chandrasekhar mass ofthe gravitation wins and the core collapses• Electrons of iron atoms are absorbed by protons:1.4 ⋅ M prompt neutrinosneutron star• Heat gives rise to gammas which produce e + e - pairs and then:thermal neutrinos"From neutrinos.....". DK&ER,lecture 10


SN neutrino propertiesNeutrino luminosityvs timeThermal spectra(Fermi-Dirac distribution)Beacom and Vogel"From neutrinos.....". DK&ER,lecture 10


Neutrinos from SN 1987A – E vs angleDistribution of the angle withrespect to the direction from SNIsotropic distributionindicates mostly:rather than:(cross section smaller byorders of magnitude.)"From neutrinos.....". DK&ER,lecture 10However some anisotropyremains puzzling.


Neutrinos from SN 1987A – E vs timeFor 2 events of energies E 1 , E 2 inMeV and time difference t secthe neutrino mass in eV:where D is distance in kpcNote thresholds:Kamiokande 7.5 MeVIMB 19 MeV"From neutrinos.....". DK&ER,lecture 10


Neutrinos from gravitational collapseOccurs for a star heavier than 8 solar masses when its core exceedsChandrasekar’s limit of M=1.4 solar mass.A neutron star of a radius of r about 20 km is formed.The released energy is „neutron star binding energy”:99% of this energy is carried away by neutrinos;neutrino luminosity L~ 3x10 53 ergs1% goes into kinetic energy of the envelope particlesOnly 0.01% goes into lightAnd yet it’s 10 49 ergs while our sun emits 10 33 ergs/sec"From neutrinos.....". DK&ER,lecture 10One SN shines as10 16 Suns!


Neutrinos from gravitational collapseTotal neutrino luminosity L~ 3x10 53 ergsPrompt pulse lasts only several msechence its total luminosity is smallAlmost all L is carried away by thermal neutrinosapproximately obeying „equipartition of energy”:However energies of ν µ and ν τ are less degraded byinteractions than that of ν e"From neutrinos.....". DK&ER,lecture 10


Analysis of the observed eventsThermal neutrinos should be described by Fermi-Dirac distribution.Their fluence (i.e. flux integrated over time):T – temperatureE – neutrino energythis spectrum wasassumed for theanalysisFrom the measurements of onEarth one can calculate:"From neutrinos.....". DK&ER,lecture 10L in ergsΦ fluence in cm -2T in MeVD distance in kpc


Neutrinos from SN 1987A- resultsExperiment: IMB KamiokandeTemperature (MeV)Fluence (x 10 10 cm -2 )Average energy (MeV)Total ν e energy (x10 52 ergs)Total energy released(x10 53 ergs)Assuming :a) a distance of 49 kpcb)equipartition of energy between different flavors"From neutrinos.....". DK&ER,lecture 10


What have we learned aboutneutrinos from SN1987ALifetimeMasssecFor 2 neutrinos of energies E 1 (MeV) and E 2 (MeV)and the difference between their flight times δt (sec)their mass m (eV) :m 2 =19.4 ⋅δt⎛D 1 2E − 1 2⎝⎜1E 2⎞⎠⎟where D (kpc) is the distancefrom the supernova.However one has to take into account a possibility that the time profileof the neutrino emission can mimick the pulse modulation due to the finitemass"From neutrinos.....". DK&ER,lecture 10


What have we learned aboutneutrinos from SN1987AMagnetic momentelmgt interaction would flip ν helicity into RHand ν would carry away energy withoutinteracting - contrary to the observation thatalmost all the binding energy has beenaccounted forElectric chargea charged ν would experience an energydependent delay due to its curved pathin the intergalactic and galactic mgt field."From neutrinos.....". DK&ER,lecture 10


Test of equivalence principleThe fact that the fermions (neutrinos) and bosons (photons) reached theEarth within 3 hours provides a unique test of the equivalence principle ofgeneral relativity. The gravitational field of our Galaxy causes a signifcanttime delay, about 5 months, in the transit time of photons from theSN1987A.The observation of Feb. 23, 1987, proved that the neutrinos and therecorded photons are acted by the same gravitationally induced time delaywithin 0.5%"From neutrinos.....". DK&ER,lecture 10


Actually neutrinos arrived earlier...About 3 hours earlier than light.Photons had to wait until theenvelope gets thin enough topass through."From neutrinos.....". DK&ER,lecture 10


SN1987A"From neutrinos.....". DK&ER,lecture 10


SN 1987ASeven years later..photos by HubbleSpace Telescope"From neutrinos.....". DK&ER,lecture 10


SN 1987A"From neutrinos.....". DK&ER,lecture 10


Expected signals from future SNin Super-Kamiokande:Andromeda M31Eg. for an SN in theGalactic center at 10 kpc:Hopefully other thanelectron antineutrinoscould be studied .SN neutrinos arealready flying to us"From neutrinos.....". DK&ER,lecture 10


Expected signals from future SNIn ICARUS:CC current:ν e+ 40 Ar → e − + 40 K *ν e+ 40 Ar → e + + 40 Cl *NC current:(E thr= 1,5 MeV)(E thr= 7,5 MeV)40 K * → 40 K + γ (4.4 MeV)ν + 40 Ar → ν + 40 Ar *ν + e − → ν + e −40 Ar * → 40 Ar + γ (1.5 MeV)There is a possibility to separateelectron neutrinos and antineutrinosand study very low energy part of the neutrino spectrum."From neutrinos.....". DK&ER,lecture 10


Expected signals from SN remnants(SNR neutrinos)Observation of a single SNrelies on a very brief signal –trivial separation frombackground but a very rareevent.However the Universe is full ofneutrinos from all previous SNflying around. One only needs toseparate them from backgroundof other neutrinos.The expected rate of SNRneutrinos is very modeldependent but experimentallywe may be close to detect them.arXiv:hep-ph/0408031"From neutrinos.....". DK&ER,lecture 10


Expected signals from SN remnants(SNR neutrinos)Expected rate of SNRevents in a future 3 ktonIcarus type detector.The distribution of electronor positron energy."From neutrinos.....". DK&ER,lecture 10arXiv:hep-ph/0408031


Expected rate of gravitational collapseEstimates from:in Milky Way• Historical observations: only 8 observed, however all within 5 kpcfrom the Sun (other obscured by dust in galactic disk).When one corrects for this and for the fact that not all observedSN resulted from core collapse one gets: one SN per 20 years• Birth rate of pulsars – model dependent: one SN per 10 or 100 yearsAll pulsars result from core collapse, but not all SN leave a pulsarbehind• Oxygen abundance in the Galaxy: one SN per 10 years.Most of oxygen originates in core collapses."From neutrinos.....". DK&ER,lecture 10


Supernovae with and without corecollapse.Core collapse only for SN II and Ib.SN Ia:A binary system including e.g. a white dwarf.White dwarf (carbon/oxygen) accretesmatter from the companion and increasesits mass until new fusion reaction starts.The whole star is destroyed in the explosion."From neutrinos.....". DK&ER,lecture 10


Future observations of neutrinosfrom SN Super-Kamiokande can „see” a few neutrinos from the near-by galaxy,M31, in the Andromeda constellation, 2.1 million light years away One SN in 10-50 years in our Galaxybut mostly invisible in optical spectrum For a Galactic SN thousands of events in SKand hundreds in Icarus Network of instant SN warning exists to point telescopes in a SNdirection. Experiments should minimize their dead time. Possible observation of neutrinos from cumulated SNRUnique way to learn about collapsing mechanism and about neutrinos"From neutrinos.....". DK&ER,lecture 10


Future observations of neutrinosfrom SNEta Carinae is a massiveand unstable star withstrong stellar winds.Perhaps a futuresupernova?"From neutrinos.....". DK&ER,lecture 10

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