Blast waves from GRBs Andrei M Beloborodov Columbia

Blast waves from GRBs Andrei M. Beloborodov Columbia University 1. Blast wave 2. Ge. V – Te. V flashes

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

Self-similar adiabatic blast wave: m G 2 = const (Blandford, Mc. Kee 1976)

Thompson & Madau (2000), Beloborodov (2002)

Beloborodov (2002)

Beloborodov (2005)

GRB blast wave at the deceleration stage

GRB blast wave at the deceleration stage 16 Rb ~ tb Gn c ~ 10 (G n /300) cm

Optical flash in GRB 990123 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 ~ ke. V energy in the fluid frame. (Akerlof et al. 1999) Þ Compton cooling of the flash electrons by GRB photons and Þ Production of Ge. V-Te. V flash much stronger than its optical counterpart.

Expected Ge. V-Te. V flashes 1. Flash spectrum below Ge. V has the same slope as the low-energy part (0. 1 Me. V) of the main GRB. At higher energies –- fast-cooling spectrum ( E 1/2 ). 2. The flash is a few times longer than the prompt GRB. 3. The flash has a smooth light curve. (Beloborodov 2005)

GRB 941017 Gonzalez et al. 2003

Summary • The huge G makes the explosion qualitatively different from other known explosions: -- Me. V radiation front opens the gap 15 (R ~ 10 -- blast wave is loaded with e+/- pairs (R ~ 10 16 cm) -- survived neutrons leak out of the decelerated ejecta 16 17 and change the shock mechanism (R ~ 10 --10 cm) • Swift will observe the early stage of the explosion. A flat optical spectrum is expected from e+/- loaded blast wave. • Ge. V-Te. V flashes must be produced by GRBs, which can be easily observed by GLAST.