CAN WE PROBE THE LORENTZ FACTOR OF GAMMA-RAY BURSTS FROM GeV–TeV SPECTRA INTEGRATED OVER INTERNAL SHOCKS?
CAN WE PROBE THE LORENTZ FACTOR OF GAMMA-RAY BURSTS FROM GeV–TeV SPECTRA INTEGRATED OVER INTERNAL SHOCKS?
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DOI：
10.1088/0004-637x/722/1/440
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发表时间：
2009-04
期刊：
影响因子：
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通讯作者：
Junichi Aoi;K. Murase;Keitaro Takahashi;K. Ioka;S. Nagataki
中科院分区：
文献类型：
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作者：
Junichi Aoi;K. Murase;Keitaro Takahashi;K. Ioka;S. Nagataki
本文通过数值计算和解析计算，重新讨论了伽玛射线暴瞬发相中电子-正电子对产生的高能光谱截止。我们表明，传统的指数和/或破幂律截止应大幅修改为一个较浅的破幂律在实际观测中，整合从不同的内部冲击排放。由于陡化对观测来说是微小的，这种“涂抹”效应通常会降低以前对伽玛暴外流的洛伦兹因子的估计。我们将我们的公式应用于最近由费米卫星上的大面积望远镜探测器探测到的GRB 080916 C，发现最小洛伦兹因子可以是10600（甚至更小的值），这低于但与之前的结果10900一致。观测陡峭的能量（所谓的“对断裂能量”）对于在未来的观测中诊断洛伦兹因子和/或发射位置至关重要，特别是当前和未来的切伦科夫望远镜，如MAGIC，VERITAS和CTA。
We revisit the high-energy spectral cutoff originating from the electron–positron pair creation in the prompt phase of gamma-ray bursts (GRBs) with numerical and analytical calculations. We show that the conventional exponential and/or broken power-law cutoff should be drastically modified to a shallower broken power law in practical observations that integrate emissions from different internal shocks. Since the steepening is tiny for observations, this “smearing” effect can generally reduce the previous estimates of the Lorentz factor of the GRB outflows. We apply our formulation to GRB 080916C, recently detected by the Large Area Telescope detector on the Fermi satellite, and find that the minimum Lorentz factor can be ∼600 (or even smaller values), which is below but consistent with the previous result of ∼900. Observing the steepening energy (the so-called “pair-break energy”) is crucial to diagnosing the Lorentz factor and/or the emission site in future observations, especially current and future Cherenkov telescopes such as MAGIC, VERITAS, and CTA.