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伽马射线暴瞬发模拟的一般方案

A general scheme for modeling gamma-ray burst prompt emission

Pawan Kumar, Erin McMahon, UT Austin

备注：
Published in MNRAS Jan 2008, 56 pages
发表信息：
Mon.Not.Roy.Astron.Soc.384:33,2008
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摘要：

本文描述了一种模拟伽马射线暴瞬发辐射的一般方法。我们发现，要通过同步加速器过程产生爆发，需要非物理条件--源与爆炸中心的距离（$R_γ$）必须大于$\sim 10^{17}$ cm和源洛伦兹因子$\gta 10^3$ ;对于如此高的洛伦兹因子，减速半径即使周围介质中的颗粒的数密度小至$\sim 0.1$ cm $^{-3}$，（$R_d$）也小于$R_γ$。结果$R_γ> R_d$与早期的X射线和光学余辉数据相矛盾。同步加速器自康普顿（SSC）过程的效果要好得多。有一个大的解决方案空间的一个典型的伽玛射线暴即时发射将通过SSC过程中产生。在SSC模型中，发现伴随爆发的瞬时光辐射非常明亮（$\lta$ 14 mag;对于$z\sim2$），这超过了大多数GRB观测到的通量（或上限）。电子的连续加速可以显著地减少光通量，并将其降低到观察到的极限。（节录）

英文摘要：

We describe a general method for modeling gamma-ray burst prompt emission. We find that for the burst to be produced via the synchrotron process unphysical conditions are required -- the distance of the source from the center of the explosion ($R_γ$) must be larger than $\sim 10^{17}$cm and the source Lorentz factor $\gta 10^3$; for such a high Lorentz factor the deceleration radius ($R_d$) is less than $R_γ$ even if the number density of particles in the surrounding medium is as small as $\sim 0.1$ cm$^{-3}$. The result, $R_γ> R_d$, is in contradiction with the early x-ray and optical afterglow data. The synchrotron-self-Compton (SSC) process fares much better. There is a large solution space for a typical GRB prompt emission to be produced via the SSC process. The prompt optical emission accompanying the burst is found to be very bright ($\lta$ 14 mag; for $z\sim2$) in the SSC model, which exceeds the observed flux (or upper limit) for most GRBs. Continuous acceleration of electrons can significantly reduce the optical flux and bring it down to the observed limits. (Abridged)

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