| Abstract : | The time-averaged spectrum of Gamma-Ray Burst(GRB) is often well fitted by an
empirical smooth broken power-law function terms as Band model.
However, the physical interpretation of this Band function is still
being debated. Two competitive models are the synchrotron emission from
a non-thermal particle distribution accelerated at a shock front
(synchrotron shock model) or a relativistically expanding fireball
with a predominant thermal spectrum. Successful explanation of many
GRBs using a multi-temperature black body spectrum support the later
while significant detection of polarised emission from the GRB favors
the synchrotron shock model. We perform a detailed study of the evolving
fireball model with its temperature evolving as a function of its
radius. The numerical code developed under this scenario is coupled
with X Spec as a local model and used to fit the time-averaged spectrum
of GRB xxx. The main fit parameters are the photospheric temperature and
radius, the Lorentz factor of the expansion, and the index describing the
temperature evolution. The best-fit parameters obtained are critically
analysed to validate the fireball model. |
