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Gamma-Ray Bursts observation with GLAST

Gamma-Ray Bursts observation with GLAST. Nicola Omodei, on behalf of the LAT GRB science working group. The GLAST satellite has two telescopes : Large Area Telescope: Pair Conversion Detect photons between 20 MeV - 300GeV Tracking system: Silicon Strip Detectors Calorimeter:

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Gamma-Ray Bursts observation with GLAST

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  1. Gamma-Ray Bursts observation with GLAST Nicola Omodei, on behalf of the LAT GRB science working group

  2. The GLAST satellite has two telescopes: Large Area Telescope: Pair Conversion Detect photons between 20 MeV - 300GeV Tracking system: Silicon Strip Detectors Calorimeter: CsI Cristals (8.5 r.l., hodoscopic) Anticoincidence: Segmented ACD Tracker LAT g e+ e- ACD Grid Calorimeter The GLAST mission (Gamma-ray Large Area Space Telescope) Launch Vehicle Delta II – 2920-10H Launch Location Kennedy Space Center Orbit Altitude 565 Km Orbit Inclination 28.5 degrees Orbit Period 95 Minutes Launch Date Late 2007

  3. Glast Burst Monitor 12 Sodium Iodide (NaI) Scintillation detectors Wide Field of View Burst trigger Coverage of the typical GRB spectrum (10 keV 1 MeV) 2 Bismunth Germanate (BGO) Scintillation detectors Spectral overlap with the LAT (150 keV-30 MeV) The GLAST mission (Gamma-ray Large Area Space Telescope)

  4. Mission Operation • Operational modes • Sky survey (full coverage every 3 hours) • Pointing mode • GBM and LAT can trigger independently • GBM will detect ~ 200 burst/year • >60 burst/year in LAT FoV • Position resolution • GBM < 15o initially, update <5o • LAT > ~10 arcmin depending on burst • Autonomous repoint • GLAST can slew to put/keep an intense burst in the LAT FoV. • Downlink and communications • Bursts data on ground in near real-time (TDRSS) • Burst alerts provided to GCN within ~10 sec. • Full science data ~ 8 times a day (TDRSS) GLAST TDRSS Users community White Sands GCN

  5. GLAST Simulations GRB models (+galactic extragalactic diffuse, thousands of AGNs, hundreds of pulsars, CR,…) • GRB MODELS: • Phenomenological: • Use observed distributions from BATSE. • Must extrapolate to LAT Energies. • Physical Models: • Example: Fireball Model (Piran, 1999) • Hybrid Thermal+Powe law model (Ryde) GLAST LAT simulators: GEANT 4 (Full MC) Parameterized IRF (fast simulator) GBM simulator Combined signal from GBM (BGO NaI) and LAT detectors Simulated Data (HEASARC)

  6. Duration Fluence Spectral Index: Low E Spectral Index: High E The initial distribution • Start with BATSE Catalog • Sample GRB characteristics • Duration, Flux,spec. index, etc. • Simulate 1 year of GLAST. BATSE: (Green)Simulation: (Blue)

  7. LAT GRB sensitivity • Consider different min. energies • Number of photons detected. • Number of GRB/yr vs Number of LAT counts • EBL attenuation included • MODEL DEPENDENT COMPUTATION !!! SFR (Porciani & Madau ‘01) Binary Mergers (Fryer ‘99) LAT GRB sensitivity extrapolating the spectrum from BATSE energies to LAT energies assuming an annual rate of 650 GRB/yr. EBL attenuation included.

  8. GLAST Simulations: (Detectors) • Two Methods for detector simulation: • Full Simulation using GEANT4. • Parameterized Response Function. • Simulate response of both GBM and LAT. • Energy Spectrum • Combined detectors cover~7 decades in energy. LAT GBM: NaI6 GBM: BGO Normalized Counts/sec/keV 10 Energy (keV) 108

  9. Composite spectrum of 5 EGRET Bursts Dingus et al. 1997 No evidence of cutoff “Unveiling” the GRB High Energy Emission • LAT is an important tool for understanding the high energy (> 50 MeV) of GRBs • EGRET detected a small # of high energy bursts • Prompt GeV emission w/o a high energy cut-off. • GLAST vs EGRET • Larger effective area • Wider FoV • Shorter deadtime • GLAST can search for extended/delayed high energy emission • GLAST can search for high Energy cutoff • 10 % Energy resolution • Characteristics of the source • EBL Absorption (see next page) Reconstructed c.o. 5.5±1.5 GeV G=220±60 Simulated GRB with c.o. at 4.5 GeV

  10. High Redshift GRBs • Modeled GRB observed by Swift 04-Sep-05. • Redshift: 6.3, BAT Fluence: 5.4 x 10-6 ergs/sec, Dur: ~500 s • Modeled two GRBs, one at z=0 and one at z=6.3 • Simulated GBM and LAT with response functions • Modeled EBL absorption for z=6.3 GRB. z = 0 No EBL Absorption z = 6.3 EBL Absorption EBL attenuation important only for very high redshift burst.

  11. Using GRBs as a Probe for New Physics • Measuring GRB at different redshift can be used as a probe for Lorentz Invariance Violation • Effects arise in some Quantum Gravity Models. • Look for delayed arrival of photons as a function of energy. • LAT provides a means to measure the high energy photons and arrival. • System clock: 50 ns • Other observations required to localize and measure redshifts. 20 bright GRBs @ 1 Gpc w/ QG. Dispersion due to QG. Norris, Bonnell, Marani, Scargle 1999 Omodei, Cohen-Tanugi, Longo,2004

  12. ~2020 XRT GBM BAT LAT 2007 2005 0.1 keV 10 keV 100 KeV 1 MeV 30 MeV 300 GeV GLAST and SWIFT era • GLAST can provide alerts to GRBs that Swift can point for follow on observations. • Precise measurements of the position will be given by Swift! • GLAST will frequently scan the position of the bursts hours after the Swift alerts, monitoring for High energy emission. • In these cases, we will have a broad spectral coverage of the GRB spectrum (from 0.1 keV to hundreds of GeV > 9 decades!!). • Swift is seeing 100 bursts per yr: ~ 20/yr will be in the LAT FoV

  13. Conclusions • GLAST will open a new window on the gamma-ray sky, exploring an uncovered region of the electromagnetic spectrum, with big impact on science! • The flight hardware is close to being integrated with the SC! • GLAST - GBM will detect ~200 bursts per year, > 60 suitable for LAT observations. • GLAST - LAT will independently detect ~ 100 bursts • GLAST will provide burst alerts rapidly (~ 10 seconds) • Burst position is provided by both the GBM (~5o) and LAT (1o-0.1o) in few seconds and sent to ground for afterglows follow-up. • GLAST can be repointed autonomously. • Spectral resolution typically 10% important for spectral studies (high energy cut-offs, inverse Compton peaks). • Joined LAT and GBM observations will study the relationship between GeV emission and keV-MeV • The large lever-arm is a key point for investigating fundamental questions like the breaking of the Lorentz Invariance due to Quantum Gravity effect. • Partnership between Swift and GLAST would open a new era for the gamma-ray astronomy! GLAST launch* *Simulated data

  14. BACKUP SLIDES

  15. Thin Thick Thin Thick Full Tkr GLAST/LAT performance Multiple scattering Energy Resolution: ~10% (~5% off-axis) PSF (68%) at 100 MeV ~ 5o PSF (68%) at 10 GeV ~ 0.1o Field Of View: 2.4 sr Point Source sens. (>100 MeV): 3x10-9 cm-2 s-1 Intrinsic resolution of the tracker F.o.V.: 2.4 sr

  16. GRB Spectrum with a Hybrid Model • Simulation (NaI+BGO+LAT) of a hybrid model consisting of a thermal, photospheric component (~100 keV) and a non-thermal synchrotron shock component with a high-energy cut-off. BATSE burst GRB 911016 used as calibration. (POSTER 3.52)

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