Gupta 2007 Prompt阶段的高能光子

主要内容:
考虑不同可能的高能光子的产生，企图GLAST能观测到。

精彩摘抄:


文章信息:
Prompt Emission of High Energy Photons from Gamma Ray Bursts

Authors: Nayantara Gupta, Bing Zhang

(Submitted on 10 Apr 2007)

Abstract: Within the internal shock scenario we consider different mechanisms of high energy photon production inside a Gamma Ray Burst (GRB) fireball and derive the expected high energy photon spectra from individual GRBs during the prompt phase. The photon spectra of leptonic and hadronic origins are compared within different sets of parameter regimes. Our results suggest that the high energy emission is dominated by the leptonic component if energy carried by electrons is not unreasonably small (e.g. $\epsilon_e > 10^{-3}$). For very small values of $\epsilon_e$ the hadronic emission component may be comparable to the leptonic component in the GeV-TeV regime. However, a much larger energy budget of the fireball is required to account for the same level of the observed sub-MeV spectrum. The fireballs are therefore extremely inefficient in radiation. For canonical bulk Lorentz factors of the fireballs (e.g. $\Gamma=400$), emissions above $\sim 10$ GeV are attenuated by two-photon pair production processes. For even higher Lorentz factor fireballs, emissions of 10 TeV - PeV due to $\pi^0$-decay can escape from the internal shocks, but they are generally attenuated by external soft photons. The reprocessed emission would contribute to the diffuse gamma-ray background. GLAST LAT can detect prompt emission of bright long GRBs above 100 MeV.

Comments:

17 pages 10figures submitted to MNRAS

Subjects:

Astrophysics (astro-ph)

Cite as:

arXiv:0704.1329v1 [astro-ph]