THE SPECTRAL FEATURES OF GAMMA-RAY BURSTS AT LOWER AND HIGHER ENERGY COMPONENTS - A POSSIBLE WAY TO DISTINGUISH BETWEEN COSMOLOGICAL AND GALACTIC ORIGINS OF GAMMA-RAY BURSTS
Dm. Wei et Ks. Cheng, THE SPECTRAL FEATURES OF GAMMA-RAY BURSTS AT LOWER AND HIGHER ENERGY COMPONENTS - A POSSIBLE WAY TO DISTINGUISH BETWEEN COSMOLOGICAL AND GALACTIC ORIGINS OF GAMMA-RAY BURSTS, Monthly Notices of the Royal Astronomical Society, 290(1), 1997, pp. 107-112
The isotropic and inhomogeneous distribution of gamma-ray burst source
s (GRBs) detected by the Burst and Transient Source Experiment (BATSE)
suggests that the GRBs are located either at cosmological distances o
r in an extended Galactic halo. Both models predict that the sudden re
lease of a huge amount of energy will result in a foreball, and the in
teraction between fireball and interstellar medium can produce non-the
rmal gamma-ray emission. In this paper we discuss the spectral feature
s of GRBs at lower and higher energy bands based on the shock model pr
oposed by Meszaros & Rees. We find that for the cosmological model, th
e optical flash is nearly impossible to observe since the synchrotron
self-absorption frequency is always above similar to 10(15) Hz, but th
e TeV emission due to inverse Compton scattering (ICS) is possible to
detect if the absorption by the intergalactic radiation field is small
. For the Galactic model, the situation is just the opposite; both the
self-absorption frequency and the efficiency of the ICS are lower tha
n those in the cosmological model. We suggest that this may provide a
way to distinguish between Galactic and cosmological origin of GRBs.