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arXiv 0807.0355astro-ph
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费米Gamma Ray太空望远镜的伽马射线暴预测

Gamma Ray Burst Predictions for the Fermi Gamma Ray Space Telescope

Truong Le, Charles D. Dermer

备注：
9 pages, 6 figures, Accepted for publication in ApJ; this version contains an additional section that discusses the fluence estimates and uncertainties for EGRET GRBs
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摘要：

报道了费米伽玛射线空间望远镜伽玛暴探测率唯象模型的计算结果。这一估计是基于BATSE 4 B GRB注量分布、EGRET在100 MeV - 5 GeV和BATSE在20 keV - 2 MeV下测量的注量的平均比率以及5个EGRET火花室GRB的平均EGRET GRB谱。在100 MeV - 5 GeV能量下，当注量比为10%、数谱指数α 1 = -2时，我们估计费米大面阵望远镜视场中每年约有20个和4个伽玛暴，其中至少有5个光子的能量分别为E > 100 MeV和E > 1 GeV。我们还估计在费米视场中每年约有1.5个伽玛暴，其中至少检测到1个能量E > 10 GeV的光子。对于这些参数，我们估计= 1 - 2伽玛暴每年检测到费米望远镜与超过100个伽马射线与E >~ 100$ MeV。对α_1 =-2.2、不同注量比和AGILE γ射线卫星作了比较预报。利用100 MeV - 10 GeV注量与20 keV - 20 MeV注量的关系图对不同类别的伽玛暴进行分类，被认为是寻找不同类别的伽玛暴的一种方法，特别是寻找短硬和长持续时间伽玛暴类别之间的光谱差异，以及寻找伽玛暴中的硬成分。

英文摘要：

Results of a phenomenological model to estimate the GRB detection rate by the Fermi Gamma ray Space Telescope are reported. This estimate is based on the BATSE 4B GRB fluence distribution, the mean ratio of fluences measured at 100 MeV - 5 GeV with EGRET and at 20 keV - 2 MeV with BATSE, and the mean EGRET GRB spectrum for the 5 EGRET spark-chamber GRBs. For a 10% fluence ratio and a number spectral index alpha_1 = -2 at 100 MeV - 5 GeV energies, we estimate a rate of ~ 20 and 4 GRBs per yr in the Fermi Large Area Telescope field of view with at least 5 photons with energy E > 100 MeV and E > 1 GeV, respectively. We also estimate ~ 1.5 GRBs per yr in the Fermi FoV where at least 1 photon with energy E > 10 GeV is detected. For these parameters, we estimate = 1 - 2 GRBs per year detected with the Fermi telescope with more than 100 gamma rays with E >~ 100$ MeV. Comparison predictions for alpha_1 = -2.2, different fluence ratios, and the AGILE gamma-ray satellite are made. Searches for different classes of GRBs using a diagram plotting 100 MeV - 10 GeV fluence vs. 20 keV - 20 MeV fluence is considered as a way to search for separate classes of GRBs and, specifically, spectral differences between the short-hard and long duration GRB classes, and for hard components in GRBs.

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