1. Gamma-Ray Bursts prospects for GLAST

2. GRBs I Basic phenomenology
Flashes of high energy photons in the sky (typical duration is few seconds).
Isotropic distribution in the sky
Cosmological origin accepted (furthest GRBs z ~ 7 – billions of light-years).
Never seen two GRBs from the same location (destructive phenomenon?).
Extremely energetic and short:the greatest amount of energy released in a short time (not considering the Big Bang).
Sometimes x-rays and optical radiation observed after days/months (afterglows).

3. GRB observations First detected...
... in early ‘70 by military satellites (Vela).
Originally connected with Neutron Stars (NSs) in the Milky Way.
Then CGRO came...
EGRET (10 MeV-10 GeV): ~ 1 burst per year.
BATSE (10 keV-10 MeV): ~ 1 burst per day.
Distribution in the sky found to be isotropic.
Cosmological origin?
The afterglow era...
BeppoSax: X-ray afterglows ->
Direct observation of the “host galaxy”
A “smoking gun” for extragalactic origin!
Keck: optical afterglow.
And the Swift Era…
On going mission
Dedicated to GRB (x-ray follow up)
New understanding of GRB afterglow…more open questions?
The GLAST era
High energy emission
Connection to low energy
New discovery window: region of the EM spectra previously uncovered

4. GRB
This bursts remains an enigma, and it is a perfect “key study” for GLAST

5. Another enigma “Extra component”
BATSE + EGRET joint analysis:
2 separate components
Independent time evolution (extended HE emission)
Spectral index of the HE component: -1
Cut-off at higher energies: where?
How common in GRB?
Very promising picture for GLAST!

6. The GLAST mission (Gamma-ray Large Area Space Telescope)
The GLAST satellite has two telescopes:
Large Area Telescope:
Pair Conversion
Detect photons between 20 MeV GeV
Tracking system:
Silicon Strip Detectors
Calorimeter:
CsI Cristals (8.5 r.l., hodoscopic)
Anticoincidence:
Segmented ACD
Tracker
ACD
Calorimeter
Grid
LAT g
e e-
Launch Vehicle Delta II – H
Launch Location Kennedy Space Center
Orbit Altitude 565 Km
Orbit Inclination ~24.5 degrees
Orbit Period 95 Minutes
Launch Date Late 2007

7. 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)
10-4
10-5
10-6
10-7
10-8
10-9
10-10

8. GLAST & GRB GLAST TDRSS White Sands GCN Users community
Operational modes
Sky survey (full coverage every 3 hours)
Pointing mode
GBM and LAT will both have triggers!
GBM will detect ~ 200 burst per year
>60 burst per year within the FoV of the LAT detector
Alert to GCN ~ 10 seconds
GBM < 15o initially, update <5o
LAT > ~10 arcmin depending on burst
Downlink and communications
Bursts alerts sent on ground in near real-time (TDRSS)
TDRSS: full science data downlink (~ 8 times a day)
Autonomous repoint
In case of intense bursts GLAST can repoint to keep the burst in the LAT FoV. Dwell time: initially 5 hr (adjustable)
GLAST
TDRSS
Users community
White Sands
GCN

9. GRB data flow... ISOC ISOC BAP GCN S/C GIOC 1) GBM & LAT trigger
GBM GCN notice (10s)
BAP
GBM gnd analysis GCN notice (30min)
GCN
Alert message
Alert message
LAT GCN notice (15 s)
L1 processing 24 hours
GBM ground analysis circular? (36 hours)
S/C
GIOC
4-12 hours
GCN notice (6-14 hours)
Final GBM analysis
Full Downlink
GCN Report (24-72 hours)
GBM GRB Catalog
LAT Ground analysis circular (24-48 hours)
1) GBM & LAT trigger
4-12 hours
L1 processing 1 hour
ISOC
ASP follow-up LAT analysis
(spectra, localisation, lc, afterglow etc)
Manual follow-up LAT analysis
GRB LAT catalog
Joint LAT/GBM analysis
Joint LAT/GBM catalog
ISOC

10. Manual follow-up LAT analysis
GRB data flow...
GBM GCN notice (10s)
BAP
GBM gnd analysis GCN notice (30min)
GCN
Alert message
Alert message
LAT GCN notice (15 s)
L1 processing 24 hours
GBM ground analysis circular? (36 hours)
S/C
GIOC
GCN notice (6-14 hours)
No LAT GRB found!
4-12 hours
Final GBM analysis
Full Downlink
GBM GRB Catalog
2) GBM trigger only...
4-12 hours
L1 processing 1 hour
ISOC
ASP follow-up LAT analysis
(searching for GRB...)
Manual follow-up LAT analysis
Searching...
Upper limit
Around 30-50% of the time, the GBM alert will be spurious.
Source Deoccultation, CR precipitation, Solar Flares
Similar Procedure for any non-LAT trigger (Swift)
ISOC

11. Manual follow-up LAT analysis
GRB data flow...
GBM GCN notice (10s)
BAP
GBM gnd analysis GCN notice (30min)
GCN
Alert message
Alert message
LAT GCN notice (15 s)
L1 processing 24 hours
GBM ground analysis circular? (36 hours)
S/C
GIOC
4-12 hours
GCN notice (6-14 hours)
Final GBM analysis
Full Downlink
GCN Report (24-72 hours)
GBM GRB Catalog
LAT Ground analysis circular (24-48 hours)
3) GBM trigger only...
4-12 hours
L1 processing 1 hour
ISOC
ASP follow-up LAT analysis
(searching for GRB...)
Manual follow-up LAT analysis
Searching...
Found! Analyze it!
Similar Procedure for any non-LAT trigger (Swift)
Joint LAT/GBM analysis
Joint LAT/GBM catalog
ISOC

12. LAT GRB Sensitivity Phenomenological model for GRB simulations:
From BATSE energy to LAT energy
Sampling observables form BATSE distribution
See the LAT response
Comparison with the BATSE catalog:
Bimodal distribution in duration and fluences for long and short bursts
Fluence - Duration correlation

13. Study the LAT GRB sensitivity
The numbers depend on the assumed model: here we are extrapolating from BATSE to LAT energies! (MeV - GeV)
Reasonable model: LAT can detect prompt emission from GRB (some per year)
IRF dedicated to GRB (see next): double the number of low energy photons!
(update sensitivity/plots… coming soon!)

14. On Board Science Most of the detected photons have on-board tracks
Onboard Reconstruction available
GRB alert algorithms:
Clustering Histogram rate (in different region of the sky)
Advanced trigger alg based on spatial and temporal clustering
First Localization estimation => First GCN via TDRESS!

15. High energy emission... SSC component not in the BATSE energy range
Possible detection by EGRET (?) ,

16. Connection between X-Ray flashes and Gamma-Ray Emisison...
Galli and Piro, 2006
Predictions in the context of External-Shock model:
Gamma-Flares as IC from X-Ray Flashes
Possible target for GLAST (and maybe Seen by EGRET The 17th February 1997)
Simulations for the GLAST/LAT
See Galli’s Talk

17. Other on going activities…
Quantum Gravity and GRBs. Scargle, Norris, Bonnell
Pair Attenuation Signatures in Evolving Gamma-Ray Burst Spectra Matthew G. Baring and Brenda L. Dingus
Time Dependence of Pair Opacity in GRB Internal Shocks. Johann Cohen-Tanugi, Jonathan Granot, Eduardo Do Couto e Silva

18. Conclusions
Gamma-Ray Burst is a very promising Scientific Target for GLAST
GBM and LAT simultaneous observations
GBM: “Peak energy” determination
Cosmology with GRB (Amati and Ghirlanda relations)
LAT: IC, but mainly a new “Discovery Window”
GRB Science Group: good in shape!
Simulations
Preparation to the analysis
Theory, predictions, and Speculations...
ISOC Support
Infrastructure, Science Operations
Multi-frequency approach:
Near IR telescope (Afterglow follow-up)
X-ray afterglow (Swift)
Synergy with TeV telescopes
TeV emission?
Absorption for cosmological attenuation
Rapid response (MAGIC)

19. …GeV-TeV synergy
ACTs: 10% duty cycle, 5˚ fov. Some of them can slew in few minutes (20% of the sky)
need ~1˚ location accuracy (LAT only)
Some back-of-the-envelope calculations:
Joint observation: Number of LAT alerts * duty cycle * sky coverage
ACT: 50 * 0.1 * 0.2 ~ 1 GRB/yr suitable for combined GeV-TeV observations
EAS: 50 * 1 * 0.2 ~ 10 GRB/yr suitable for combined GeV-TeV observations

20. GRB analysis 7 decades in energy
Data Challenge 2, Service Challenges
Spectral analysis and light curves for GBM and LAT
7 decades in energy
Combined signal from GBM (B0 N0) and LAT detectors

21. GRB hybrid model
LAT and GBM joint spectral fit with BB+BPL+Exp cut-off.
Possibility to obtain GBM and LAT simulation simultaneously

22. Model “Independent” studies
Systematic variation of the parameters
Trigger request: 5 photons and TS=25.
Most of the GRB are in the “Background free” regime!
Support the study for new IRFs