The Compton trail of gamma-ray bursts: A long-after glow

Institut de Physique Nucléaire d'Orsay, 15 rue Clémenceau, 91406 Orsay Cedex, France

Corresponding author: E. Parizot, parizot@ipno.in2p3.fr

Received: 28 January 2004
Accepted: 16 March 2004

Abstract

As they travel through the gas of the host galaxy, some of the gamma-rays emitted in a Gamma-Ray Burst (GRB) may experience Compton scattering and reach an observer even if he is not located in the direction of the primary photon beam. Such a process will last until the GRB photons have left their host galaxy, and the ambient electron density becomes negligible. We investigate the observability of this indirect GRB light, which would be seen as a faint trail along the path of the GRB photons, long after the initial event. We find that the so-called Compton trail of a 10⁵¹ erg GRB can easily be observed from Earth, wherever the explosion occurred in our Galaxy in the past few thousand years. Gamma-ray surveys of the Galaxy can therefore provide constraints on the true GRB rate (or number of GRBs per supernova), independently of the GRB beaming angle. We also calculate the expected light curve and shape of the emitting region as a function of time.