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arXiv 0909.2470astro-ph.HE
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GRB 090902 B的费米观测:瞬发和延迟发射中的一个不同光谱分量

Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission

GBM collaboration, LAT Collaboration, The Swift Team

摘要:

本文报道了费米天文台上的伽马射线暴监测仪(GBM)和大面积望远镜(LAT)对明亮的长伽马射线暴GRB 090902 B的观测。这是LAT观测到的最亮的伽玛暴之一,在瞬发阶段探测到了数百个光子。红移z = 1.822,这是费米探测到的最明亮的爆发之一。时间分辨光谱分析揭示了一个显着的幂律分量的LAT数据,这是不同于通常的带模型发射,是在亚MeV的能量范围。这个幂律分量似乎从GeV范围外推到最低能量,并且比$\sim$ 50 keV以下和100 MeV以上的能带分量更强烈。波段分量在整个爆发过程中经历了大量的光谱演化,而幂律分量的光子指数在大部分的瞬发阶段保持不变,然后在接近尾声时显著变硬。在提示阶段之后,幂律发射在LAT数据中持续到触发后1 ks,其通量下降为$t^{-1.5}$。LAT探测到了一个迄今为止从伽玛射线暴中测量到的能量最高的光子,$33.4_{-3.5}^{+2.7}$ GeV。该事件在GBM触发后82秒到达,在GBM频带中提示相位发射结束后$\sim$ 50秒到达。我们讨论了这些结果的影响模型的伽玛射线暴发射和约束模型的河外背景光。

英文摘要:

We report on the observation of the bright, long gamma-ray burst, GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component both below $\sim$ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly towards the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as $t^{-1.5}$. The LAT detected a photon with the highest energy so far measured from a GRB, $33.4_{-3.5}^{+2.7}$ GeV. This event arrived 82 seconds after the GBM trigger and $\sim$ 50 seconds after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the Extragalactic Background Light.

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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