Title of article :
Exact versus Approximate Solutions in Gamma-Ray Burst Afterglows
CarloyLucianoyBianco، نويسنده , , RemoyRuffini، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی 1 سال 2005
We have recently obtained the exact analytic solutions for the relativistic equations relating the radial and time coordinates of a relativistic, thin uniform shell expanding in the interstellar medium in the fully radiative and fully adiabatic regimes. Here we reexamine the validity of the constantindex power-law relation between the Lorentz gamma factor and its radial coordinate, which is usually adopted in the gamma-ray burst (GRB) literature on the grounds of an "ultrarelativistic" approximation. Such expressions are found to be mathematically correct but only approximately valid in a very limited range of physical and astrophysical parameters and in an asymptotic regime that is reached for a very short time only, if at all, and they are shown to be nonapplicable to GRBs.
gamma rays , ISM , Observations , bursts , kinematics and dynamics , relativity
Journal title :