Fermi GBM Science Highlights. of the GBM Team.
Gamma-Ray Burst Monitor (GBM) on Fermi The Large Area Telescope (LAT) GBM BGO detector. 200 kev -- 40 MeV 126 cm2, 12.7 cm Spectroscopy Bridges gap between NaI and LAT. GBM NaI detector. 8 kev -- 1000 kev 126 cm2, 1.27 cm Triggering, localization, spectroscopy. http://fermi.gsfc.nasa.gov/ssc/
Science with background-limited detectors S GRB Solar Flare SGR NaI TGF BGO Occultation: 111 monitored sources Pulsars: 8 persistent, 16 transient, 5 more monitored.
GBM Monthly Triggers 100 75 Number of triggers 50 25 0 Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Month (beginning July 2008)
GBM Catalog: 2 years of GRBs Duration distribution Hardness-duration relation Paciesas et al. in prep.
GBM GRB spectra: the same old models? Table 1. BEST GRB models 100 80 All Good PL SBPL BAND COMP Fluence Spectra 113 (23%) 67 (14%) 75 (15%) 231 (48%) Peak Flux Spectra 152 (31%) 48 (10%) 69 (14%) 214 (44%) 60 40 20 0 10 100 1000 10000 BAND E peak (kev) Extending the EPeak distribution: Better study of short bursts. Goldstein et al. in prep. (d) Max Count Rate 4000 3000 PL COMP SBPL BAND le mean 2000 and standard deviation of the parameter distributions igh-energy Photon Flux Energy Flux 1000 E peak (kev) E break (kev) data cuts. Index (ph s 1 cm 2 ) (10 7 erg s 1 cm 2 ) Fig. 7. Distributions of E break and E peak from fluence spectral fits. comparison between the distribution of GOOD E break and E break with n NaI 8-200 kev shows the distributions of GOOD E peak for BAND, SBPL, and COMP. 7(c the comparison between the distribution of GOOD paramters and all pa Fluence Spectra 1 2 3 4 5 # of Free Model Parameters 1.36 3.96 +7.72 1.97 - - - 2.93 +3.49-223.75 +483.80 123.80-2.82 +3.49 1.34 4.01 +10.54 2.34 2.29 +0.47 0.65 221.42 +432.04 129.12 129.74 +290.08 74.39 2.93 +3.78 1.54 4.48 +11.4 1.96 2.17 International +0.36 Cosmic Ray Conference, Beijing 2011 0.47 185.58 +428.94 81.01 175.50 +664.50 100.64 2.92 +3.77 1.39 4.48 +11.05 2.57 2.25 +0.34 204.75 +359.36 122.71 +240.41 2.92 +3.96 4.03 +9.38 Guiriec et al. 2010 BGO > 1 MeV
GBM GRB spectra: Low-energy excess α Epeak β GRB090902b Count spectrum: deviations from Band function at LE nufnu spectrum: deviations from Band function at LE nufnu spectrum: addition of powerlaw improves fit
Fermi GRB spectra: High-energy excess! α Epeak β GRB090902b: LAT data consistent with additional power-law. Abdo et al. ApJ, 2009. Epeak GRB 090902B α β Extra power law at low and high
GBM GRB spectra: thermal signature? νf ν GRB100724B: Count spectra show systematic deviations in heart of GBM energy range. Count spectra residuals improve with addition of blackbody. νf ν Guiriec et al., ApJL, 2011 Danger of extrapolating Band function to higher energies? Can this explain low LAT GRB rate?
LAT emission implies large Γ GRB 080916C Is low LAT GRB rate a result of ϒϒ --> e+e- at the source for the undetected GRBs? Abdo et al., Science 2009.
GBM 1st GRB Catalog fluences Fluence at GBM energies appears to be main limiting factor for detectability in LAT.
Soft Gamma-ray Repeaters 5 different sources, one of them seen in 2 outbursts, 1 of them newly discovered using the GBM triggers to identify source as an SGR. Recently discovered Swift SGR 1834.9-0846 showed one GBM burst. SGR 0501+4516 29 bursts in Aug 2008 Lin et al., ApJ 2011 http://gammaray.nsstc.nasa.gov/gbm/science/magnetars
Accreting pulsar project: monitoring 19 sources monitored with periods between 0.5 and 1000 s http://gammaray.nsstc.nasa.gov/gbm/science/pulsars GBM
Accreting pulsar project: monitoring + long-term behavior Monitoring of LMXB shows torque reversal GBM Historic
Accreting pulsar project: monitoring + long-term behavior = science! Studying flux and spectrum during torque reversal challenges models. GBM Historic Fill Gap with Swift BAT Camero-Arranz et al., ApJ 2010
Pulsars: Outburst monitoring XTE J1946+274 63.52 4U 0115+634 V 0332+53 XTE J1946+274 2S 1417-624 IGR J19294+1816 Swift J0513.4-65 EXO 2030+375 Cep X-4 GRO J1008-57 A 0535+26 MXB 0656-072 RX J0440.9+4431 GX 304-1 SAX J2103.5+4545 A 1118-616 MAXI J1409-619 54800 55000 55200 55400 55600 Time (MJD) 12-50 kev Pulsed Flux Frequency (mhz) 12-50 kev RMS Flux 2-20 kev Rate 15-50 kev Rate Barycentric Frequency (mhz) (kev cm -2 s -1 ) 63.50 63.48 63.46 63.44 63.42 (kev cm -2 s -1 ) 3-12 kev Rate (counts s -1 ) (counts cm -2 s -1 ) 0.25 0.20 0.15 0.10 0.05 0.00 55300 55400 55500 55600 55700 Time (MJD) 0.25 0.20 0.15 0.10 0.05 0.00 (counts s -1 ) 63.54 63.52 63.50 63.48 63.46 63.44 63.42 4 2 0-2 0.25 0.20 0.15 0.10 0.05 0.00-0.05 0.03 0.02 0.01 0.00 Fermi/GBM RXTE/ASM MAXI/GSC Swift/BAT -0.01 55200 55300 55400 55500 55600 55700 Time (MJD) 0.06 Frequency Residuals (mhz) 0.04 0.02 0.00-0.02-0.04-0.06 ν o co ν 55400 55500 55600 55700 Time (MJD)
Earth Occultation Project: monitoring fluxes and spectra. Cyg X-1 state transitions. Case et al. in prep. http://gammaray.nsstc.nasa.gov/gbm/science
Earth Occultation Project: monitoring reveals strange behavior in our standard candle. Wilson-Hodge et al., ApJ 2011
The active sun: The June 12th M-Class flare Nuclear lines Preliminary Preliminary Brem Pion decay Nuclear lines Nuclear lines Pion decay e+ brem e - 100s kev and e - /p 100s MeV accelerated within s Abdo et al. in prep.
Terrestrial Gamma-ray Flashes < 1-25 ms duration (most < 1 ms). V. Hard spectra > 30 MeV Associated with thunderstorms. Runaway electron processes.
TGFs and lightning VLF discharge time: 30% of GBM TGFs have associated discharge, most within 20 μs of peak Storm under Fermi Short TGF = γ-ray TGF Connaughton et al., JGR 2010 Storm at magnetic footprint x Long TGF = e - beam TGF
Electron Beam TGFs and magnetic mirroring
Electron beam TGFs have 10-20% positrons! Briggs et al. 2010
GBM Science in First 3 Years of Fermi GBM GRB observations allow broad-band and detailed spectral analyses, giving clues to physical mechanisms. GBM is contributing to SGR science through spectral and temporal analyses. TGF science is proving unexpectedly rich for GBM. The sun is active! Our first HE gamma-ray flare has been seen & studied. Occultation and pulsar projects help monitor the galaxy!