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Astron. Astrophys. 360, L13-L16 (2000)

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Letter to the Editor

The influence of inverse Compton scattering on GRB afterglows: one possible way to flatten and steepen the light curves

D.M. Wei 1,2 and T. Lu 3,4

1 Chinese Academy of Sciences, Purple Mountain Observatory, Nanjing, P.R. China
2 Chinese Academy of Sciences, National Astronomical Observatories, P.R. China
3 Nanjing University, Department of Astronomy, Nanjing, 210093, P.R. China
4 Chinese Academy of Sciences, Laboratory for Cosmic-Ray and High-Energy Astrophysics, Institute of High Energy Physics, Beijing, 100039, P.R. China

Received 16 May 2000 / Accepted 18 July 2000


The fireball model of gamma-ray bursts predicted that when the energetic blast wave encountered the surrounding medium, there will be afterglow emission, and the subsequent afterglow observations appeared to confirm this prediction. In this simplest fireball model, the electrons have been accelerated to a power law energy distribution in a relativistic blast wave, then they give afterglow emission through synchrotron radiation. Up to now synchrotron radiation is believed to be the main mechanism of GRB emission, however, here we will show that under some circumstances, the inverse Compton scattering (ICS) may play an important role, and can change the light curves of GRB afterglows. Here we investigate the effects of ICS in the relativistic case (the surrounding medium density [FORMULA]) and in the non-relativistic case (for both [FORMULA] and [FORMULA]), we find that in the relativistic case the effect of ICS is usually important, while in the non-relativistic case, this effect is usually unimportant, unless the surrounding medium density is very high. We show that if ICS is important, then it can flatten and steepen the light curves of GRB afterglows, and this may provide the explanation for some afterglow observations.

Key words: gamma rays: bursts – shock waves – ISM: jets and outflows

© European Southern Observatory (ESO) 2000

Online publication: August 17, 2000