Kumar 2007 伽玛暴外流的辐射模型

主要内容:
认为内激波，外激波等都不能解释伽玛暴本身的辐射。电磁模型倒是可能。

精彩摘抄:


文章信息:

astro-ph/0702319 [abs, ps, pdf, other] :

Title: The nature of the outflow in gamma-ray bursts
Authors: P. Kumar, E. McMahon (University of Texas, Austin), A. Panaitescu (LANL), R. Willingale, P. O'Brien (Leicester), D. Burrows (Penn State), J. Cummings, N. Gehrels, S. Holland (NASA GSFC), S. B. Pandey (Mullard), D. Vanden Berk (Penn State), S. Zane (Mullard)
Comments: Accepted to MNRAS Letters. 6 pages, 2 figures, & 2 tables

The Swift satellite has enabled us to follow the evolution of gamma-ray burst (GRB) fireballs from the prompt gamma-ray emission to the afterglow phase. The early x-ray and optical data obtained by telescopes aboard the Swift satellite show that the source for prompt gamma-ray emission, the emission that heralds these bursts, is short lived and that its source is distinct from that of the ensuing, long-lived afterglow. Using these data, we determine the distance of the gamma-ray source from the center of the explosion. We find this distance to be 1e15-1e16 cm for most bursts and we show that this is within a factor of ten of the radius of the shock-heated circumstellar medium (CSM) producing the x-ray photons. Furthermore, using the early gamma-ray, x-ray and optical data, we show that the prompt gamma-ray emission cannot be produced in internal shocks, nor can it be produced in the external shock; in a more general sense gamma-ray generation mechanisms based on shock physics have problems explaining the GRB data for the ten Swift bursts analyzed in this work. A magnetic field dominated outflow model for GRBs has some attractive features, although the evidence in its favor is inconclusive. Finally, the x-ray and optical data allow us to provide an upper limit on the density of the CSM of about 10 protons per cubic cm at a distance of about 5e16 cm from the center of explosion.