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					                          Gamma-Ray Bursts
Gamma-ray Large Area    observation with GLAST
Space Telescope




                                Nicola Omodei,

                       on behalf of the LAT GRB science
                                working group


                         SWIFT AND GRBS: UNVEILING THE
                             RELATIVISTIC UNIVERSE
                              San Servolo, June 2006
                                          The GLAST mission
                                 (Gamma-ray Large Area Space Telescope)


Tracker
                       g                       LAT                         The GLAST satellite has two telescopes:

                                                                           Large Area Telescope:
                                                                           Pair Conversion
                                                                           Detect photons between 20 MeV - 300GeV




                 e+         e-                                             Tracking system:
                                                                               Silicon Strip Detectors
                                                 ACD                       Calorimeter:
                                                                               CsI Cristals (8.5 r.l., hodoscopic)
Grid                                Calorimeter                            Anticoincidence:
                                                                               Segmented ACD

                                                                     Launch Vehicle           Delta II – 2920-10H
                                                                     Launch Location          Kennedy Space Center
                                                                     Orbit Altitude           565 Km
                                                                     Orbit Inclination        28.5 degrees
                                                                     Orbit Period             95 Minutes
Nicola Omodei @ INFN Pisa                                                     Date            Late 2007
                                                                     Launch Swift Conference San Servolo (Venice) 5 June 2006 2
                                 -Gamma-Ray Bursts observation with GLAST-
                                     The GLAST mission
                            (Gamma-ray Large Area Space Telescope)

                                                                        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)




Nicola Omodei @ INFN Pisa   -Gamma-Ray Bursts observation with GLAST-       Swift Conference San Servolo (Venice) 5 June 2006 3
                                                                        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
       GLAST                                                 •    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
                                       TDRSS                               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)

                                                                                                           Users
                            White Sands                       GCN                                          community



Nicola Omodei @ INFN Pisa      -Gamma-Ray Bursts observation with GLAST-      Swift Conference San Servolo (Venice) 5 June 2006 4
                                                      GLAST Simulations

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


                                          Combined signal from GBM (BGO NaI) and LAT detectors
         Simulated Data
          (HEASARC)




Nicola Omodei @ INFN Pisa            -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 5
                                             The initial distribution
                                                                              Duration                     Fluence
•    Start with BATSE Catalog
      – Sample GRB characteristics
             • Duration, Flux,spec. index, etc.
•    Simulate 1 year of GLAST.




                                                                           Spectral Index: Low E    Spectral Index: High E

           BATSE: (Green) Simulation: (Blue)




Nicola Omodei @ INFN Pisa      -Gamma-Ray Bursts observation with GLAST-       Swift Conference San Servolo (Venice) 5 June 2006 6
                                                   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)



                                                                                            GRB rate

                                                                              GBM           200/yr

                                                                              LAT           100/yr
                                                                                            (70/yr >10 counts)

          LAT GRB sensitivity extrapolating the spectrum from BATSE
          energies to LAT energies assuming an annual rate of 650 GRB/yr.
          EBL attenuation included.

Nicola Omodei @ INFN Pisa         -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 7
                                GLAST Simulations: (Detectors)


          GBM: NaI6                                    GBM: BGO                                                                       LAT




   •    Two Methods for detector
        simulation:
          – Full Simulation using GEANT4.

                                                            Normalized Counts/sec/keV
          – Parameterized Response
            Function.
   •    Simulate response of both GBM
        and LAT.
   •    Energy Spectrum
          – Combined detectors cover
            ~7 decades in energy.
                                                                                        10           Energy (keV)                 108
Nicola Omodei @ INFN Pisa   -Gamma-Ray Bursts observation with GLAST-                        Swift Conference San Servolo (Venice) 5 June 2006 8
                            “Unveiling” the GRB High Energy Emission
                                                                             Composite spectrum of 5 EGRET Bursts
  •    LAT is an important tool for
                                                                                                 Dingus et al. 1997
       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.
                                                                                      No evidence
  •    GLAST vs EGRET                                                                   of cutoff

         –   Larger effective area
         –   Wider FoV
         –   Shorter deadtime
  •    GLAST can search for extended/delayed
       high energy emission
  •    GLAST can search for high Energy
       cutoff                                                                               Reconstructed c.o.
                                                                                               5.5±1.5 GeV
         –   10 % Energy resolution
                                                                                                G=220±60
         –   Characteristics of the source
         –   EBL Absorption (see next page)

                                                                           Simulated GRB with
                                                                             c.o. at 4.5 GeV

Nicola Omodei @ INFN Pisa      -Gamma-Ray Bursts observation with GLAST-    Swift Conference San Servolo (Venice) 5 June 2006 9
                                                  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                                                               z = 6.3
                            No EBL Absorption                                                 EBL Absorption




    EBL attenuation important only for very high redshift burst.
Nicola Omodei @ INFN Pisa         -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 10
                            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.
                  dE           E                                                                    20 bright
              v=      c 1   g 
                  dp     
                              EQG 
                                   
                                                                                                      GRBs @
                                                                                                      1 Gpc w/ QG.
         – Look for delayed arrival of
           photons as a function of energy.
               E  d 
 t  10 ms   g    CM  using EQG = EPlank
              1 GeV  1 Gpc 

   •    LAT provides a means to
                                                                                                      Dispersion
        measure the high energy
        photons and arrival.                                                                          due to QG.
         – System clock: 50 ns
   •    Other observations required to                                                                  Norris, Bonnell,
                                                                                                        Marani, Scargle
        localize and measure redshifts.                                                                 1999
                                                                                                        Omodei, Cohen-
                                                                                                        Tanugi, Longo,2004

Nicola Omodei @ INFN Pisa     -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 11
                                     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




   ~2020
                                                        GBM                         LAT
        2007
                            XRT             BAT
        2005

                      0.1 keV    10 keV 100 KeV             1 MeV       30 MeV                    300 GeV

Nicola Omodei @ INFN Pisa       -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 12
                                                        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!                                                                GLAST launch*
•      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!                                                              *Simulated data


    Nicola Omodei @ INFN Pisa   -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 13
                                                BACKUP SLIDES




Nicola Omodei @ INFN Pisa   -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 14
                                            Thin
                                                               GLAST/LAT performance
                                           Thick




                                                          Energy Resolution: ~10% (~5% off-axis)
                                                          PSF (68%) at 100 MeV ~ 5o
          Intrinsic resolution of the tracker             PSF (68%) at 10 GeV ~ 0.1o
                                                          Field Of View: 2.4 sr
                                                          Point Source sens. (>100 MeV): 3x10-9 cm-2 s-1




                                           Thin
                                          Thick                                F.o.V.: 2.4 sr
                                        Full Tkr

Nicola Omodei @ INFN Pisa      -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 15
                                            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)




Nicola Omodei @ INFN Pisa      -Gamma-Ray Bursts observation with GLAST-   Swift Conference San Servolo (Venice) 5 June 2006 16

				
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posted:5/20/2010
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