1. Andrei M. Beloborodov Columbia University
Blast waves from GRBs
Andrei M. Beloborodov
Columbia University
Blast wave
2. GeV – TeV flashes

2. Meszaros, Rees (1993)
Sari, Piran (1999)

4. Self-similar adiabatic blast wave: m = constG 2
(Blandford, McKee 1976)

5. Thompson & Madau (2000), Beloborodov (2002)

7. Beloborodov (2002)

11. Beloborodov (2005)

12. GRB blast wave at the deceleration stage

13. GRB blast wave at the deceleration stage16
R ~ c ~ ( /300) cm
t G G
b b n n

14. Optical flash in GRB
The optical synchrotron flash is emitted by relativistic electrons (Lorentz factor ~ 100 in the fluid frame).
The electrons are also exposed to the GRB photons which have ~ keV energy in the fluid frame.
Compton cooling of the flash electrons by GRB photons and
Production of GeV-TeV flash much stronger than its optical counterpart.
(Akerlof et al. 1999)

15. Expected GeV-TeV flashes
Flash spectrum below GeV has the same slope as the low-energy part (0.1 MeV) of the main GRB. At higher energies –- fast-cooling spectrum ( E ).
The flash is a few times longer than the prompt GRB.
The flash has a smooth light curve.
1/2
(Beloborodov 2005)

16. GRB
Gonzalez et al. 2003

17. Summary
The huge G makes the explosion qualitatively different from other known explosions:
-- MeV radiation front opens the gap (R ~ cm)
-- blast wave is loaded with e+/- pairs (R ~ cm)
-- survived neutrons leak out of the decelerated ejecta
and change the shock mechanism (R ~ cm)
Swift will observe the early stage of the explosion. A flat optical spectrum is expected from e+/- loaded blast wave.
GeV-TeV flashes must be produced by GRBs, which can be easily observed by GLAST. 15 16 16 17