galac%c transients in the mev band - nasagalac%c variability in the gev band • compact binaries...
TRANSCRIPT
Galac%cTransientsintheMeVBand
LizHaysNASAGSFC
Galac%cVariabilityintheGeVBand• CompactBinaries– Gammabinaries(LS+61303,LS5039,HESSJ0632,J1018--cyclical)
– MSPs(pulsar/wind–transi%onal)– CygnusX-3(microquasarjet)– Novae(shock–truetransient)
• Other– EtaCarinae(collidingwindbinary--cyclical)
– Crabnebulaflares(reconnec%on?--repeatsatrandom)
– Solarflares(reconnec%on--repeatsatrandom)
Novae
NovashocksproduceGeVpar%cles
Ackermann,M.etal.2014
RadioimagingofexpandingsynchrotronemissionChomiuketal.2014
Symbio%candclassicalnovaeproducegammas
GammaCharacteris%cs
TrackingEvolu%onofShock
Metzgeretal.2015
Analogtocore-collapseSN-novaeprovidepossibilityfor%me-dependentstudyofnon-rela%vis%cshocksusingop%cal/UV/X-ray/gamma-raylightcurves.Ejectaprovidesareasonablygoodhadroniccalorimeter.
Ques%onsforMeV• WhatistheshapeofthespectrumbelowfewhundredMeV?
– Hadronicfavoredbutnotaclearcase– SNRshowanevolu%onfromleptonictohadronic
• Increaseddetec%onrate?– ~30-35/yrexpectedintheMilkyWay.LATobserves~1/yr.Someof
thisshouldbedistance.– Enhancedangularresolu%onandsensi%vityat~100MeVhelpfulin
makingdetec%onsinregionsofhigherGalac%cbackground• Extendedgamma-raylightcurve
– Hintsofextendedlightcurve,butatthresholdforLAT• Someconclusions:
– Sensi%vitysub-100MeVimportantforcharacterizingspectrumandexpandingpopula%on(morechancestotrackbroadbandlightcurves)
– Angularresolu%onimportanttodis%nguishinbrighterregionsofGalaxy
CrabNebulaFlares
CrabFlares:ExtremelyRapidVariability
Buehler, R. et al. 2012, ApJ, 749, 26
Meyer, M. et al. 2013, ApJL
Crabfluxdoublesasquicklyas5-8hrs.
FermiTOO
PushingLimitsofPar%cleAccelera%on
R.Buehler
Diffuseshockaccelera%ondoesnotworkFlaresaretoofast!Par%cleenergyexceedssynchrotronlimit~160MeVStrongevidenceforreconnec%on
CrabNebula:SpectralEvolu%onSufficientsta%s%csinLATtopar%%onthespectralfitinto11binsofconstantflux(BayesianBlocksanalysis)
FlaresfromotherPWN?
• Notcrazy,buttheCrabisaspecialobject– Extremelyhighmagne%cfield– Extremelyhighpeakenergyforsynchrotronpeak(MSH15-52peakslowerbutextendsintoMeV)
– Nearby– Knownformorphologychangesinotherbands
Ques%onsforMeV
• Whatissub-~100MeVbehaviorofnebuladuringandfollowingflares?
• Are/Howareflaresconnectedtolonger%mescalehardX-rayvariability?
• WhatistheMeVvariability?– HardX-ray/songammamonitoringstudiescurrentlyhavelowsensi%vityonshort%mescales
ThoughtsfortheFuture• Withmoderateresolu%on,goodprospectsfortransientstudiesneartheGalac%cplane– LATvariablesourcesaremainlyiden%fied
• IngeneralLAThasdetectedvariabilityforsourcespeakingintheLATband–nonthermalsourcestendtobevariable--goodprospectsfordiscoveriesinsourceclassesnotobservedbyLAT,e.g.SGRs/magnetars,microqusars,accre%ngpulsars
• Angularresolu%onisausefultoolforGalac%cstudies,evenfortransients