Fermi GBM Science Highlights.

Transcription

1 Fermi GBM Science Highlights. of the GBM Team.

2 Gamma-Ray Burst Monitor (GBM) on Fermi The Large Area Telescope (LAT) GBM BGO detector. 200 kev MeV 126 cm2, 12.7 cm Spectroscopy Bridges gap between NaI and LAT. GBM NaI detector. 8 kev kev 126 cm2, 1.27 cm Triggering, localization, spectroscopy.

3 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.

4 GBM Monthly Triggers Number of triggers Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Month (beginning July 2008)

5 GBM Catalog: 2 years of GRBs Duration distribution Hardness-duration relation Paciesas et al. in prep.

6 GBM GRB spectra: the same old models? Table 1. BEST GRB models 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%) BAND E peak (kev) Extending the EPeak distribution: Better study of short bursts. Goldstein et al. in prep. (d) Max Count Rate 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 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 # of Free Model Parameters International Cosmic Ray Conference, Beijing Guiriec et al BGO > 1 MeV

7 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

8 Fermi GRB spectra: High-energy excess! α Epeak β GRB090902b: LAT data consistent with additional power-law. Abdo et al. ApJ, Epeak GRB B α β Extra power law at low and high

9 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?

10 LAT emission implies large Γ GRB C Is low LAT GRB rate a result of ϒϒ --> e+e- at the source for the undetected GRBs? Abdo et al., Science 2009.

11 GBM 1st GRB Catalog fluences Fluence at GBM energies appears to be main limiting factor for detectability in LAT.

12 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 showed one GBM burst. SGR bursts in Aug 2008 Lin et al., ApJ

13 Accreting pulsar project: monitoring 19 sources monitored with periods between 0.5 and 1000 s GBM

14 Accreting pulsar project: monitoring + long-term behavior Monitoring of LMXB shows torque reversal GBM Historic

15 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

16 Pulsars: Outburst monitoring XTE J U V XTE J S IGR J Swift J EXO Cep X-4 GRO J A MXB RX J GX SAX J A MAXI J Time (MJD) kev Pulsed Flux Frequency (mhz) kev RMS Flux 2-20 kev Rate kev Rate Barycentric Frequency (mhz) (kev cm -2 s -1 ) (kev cm -2 s -1 ) 3-12 kev Rate (counts s -1 ) (counts cm -2 s -1 ) Time (MJD) (counts s -1 ) Fermi/GBM RXTE/ASM MAXI/GSC Swift/BAT Time (MJD) 0.06 Frequency Residuals (mhz) ν o co ν Time (MJD)

17 Earth Occultation Project: monitoring fluxes and spectra. Cyg X-1 state transitions. Case et al. in prep.

18 Earth Occultation Project: monitoring reveals strange behavior in our standard candle. Wilson-Hodge et al., ApJ 2011

19 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.

20 Terrestrial Gamma-ray Flashes < 1-25 ms duration (most < 1 ms). V. Hard spectra > 30 MeV Associated with thunderstorms. Runaway electron processes.

21 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

22 Electron Beam TGFs and magnetic mirroring

23 Electron beam TGFs have 10-20% positrons! Briggs et al. 2010

24 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!