  In this work, we have modeled the hydrodynamic evolution of the GRBs fireball
in violent interaction with the external medium (the ISM) surrounding the burst
source by assuming a power law distribution of the accelerated relativistic
electrons. For this purpose, a computer code based only on the contribution of
the predominant synchrotron radiation mechanism was developed. Light curves for
the afterglow emissions following several GRBs over the X-ray and the visible R
frequency bands were calculated. Their comparison to observed data by the
XRT/Swift satellite and Earth telescopes, respectively, points out fair overall
agreements, thus confirming the validity of our hydrodynamic simulation based
on the model of Feng et al. (2002).
