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arXiv 1802.07730astro-ph.HE
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高能伽马射线暴的环境

The Environments of the Most Energetic Gamma-Ray Bursts

B. P. Gompertz, A. S. Fruchter, A. Pe'er

摘要:

我们分析了费米卫星探测到的长伽马射线暴(LGRB)样本的性质,该样本在X射线和光学/近红外波长处具有光谱红移和良好的后续覆盖。LGRB余辉的演化取决于外部介质的密度分布,使我们能够根据观测结果将风或ISM类环境分开。我们这样做是通过确定的环境,提供了最好的协议之间的估计$p$,指数的基本幂律分布的电子能量,确定的行为的余辉在不同的光谱/时间制度。在触发后的11个休息帧小时,我们发现类似ISM和类似风的环境之间大致相等。我们进一步发现,2 $σ$分离的即时发射能量分布的风一样,ISM一样的爆发。我们研究了激波的物理参数,并计算了密度和磁场能量的(简并)乘积($ε_B$)。我们表明,$ε_B$必须是$\ll 10^{-2}$,以避免隐含的密度可与星系际介质。最后,我们发现最精确的约束观测对$p$的不一致程度超出了仅基于观测误差的预期。这表明了标准余辉理论中没有包含的其他误差来源。对于第一次,我们提供了一个测量的内在误差,它可以表示为一个错误的估计$p$的大小$0.25 \pm 0.04$。当这个误差被包括在拟合中时,具有已识别环境的LGRB的数量大幅下降,但两种类型之间的平均划分仍然存在。

英文摘要:

We analyze the properties of a sample of long gamma-ray bursts (LGRBs) detected by the Fermi satellite that have a spectroscopic redshift and good follow-up coverage at both X-ray and optical/nIR wavelengths. The evolution of LGRB afterglows depends on the density profile of the external medium, enabling us to separate wind or ISM-like environments based on the observations. We do this by identifying the environment that provides the best agreement between estimates of $p$, the index of the underlying power-law distribution of electron energies, as determined by the behavior of the afterglow in different spectral/temporal regimes. At 11 rest-frame hours after trigger, we find a roughly even split between ISM-like and wind-like environments. We further find a 2$σ$ separation in the prompt emission energy distributions of wind-like and ISM-like bursts. We investigate the underlying physical parameters of the shock, and calculate the (degenerate) product of density and magnetic field energy ($ε_B$). We show that $ε_B$ must be $\ll 10^{-2}$ to avoid implied densities comparable to the intergalactic medium. Finally, we find that the most precisely constrained observations disagree on $p$ by more than would be expected based on observational errors alone. This suggests additional sources of error that are not incorporated in the standard afterglow theory. For the first time, we provide a measurement of this intrinsic error which can be represented as an error in the estimate of $p$ of magnitude $0.25 \pm 0.04$. When this error is included in the fits, the number of LGRBs with an identified environment drops substantially, but the equal division between the two types remains.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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