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arXiv 0801.1869astro-ph
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用BATSE和EGRET观测明亮高能伽马射线暴的宽带光谱特性

Broadband Spectral Properties of Bright High-Energy Gamma-Ray Bursts Observed with BATSE and EGRET

Y. Kaneko, M. M. Gonzalez, R. Preece, B. L. Dingus, M. S. Briggs

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18 pages (emulateapj) including 7 figures & 2 tables. Accepted for publication in ApJ
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摘要：

本文对15个BATSE伽马射线暴（GRB）的宽谱（单位为$\sim30 $ keV $-200 $ MeV）进行了时间积分谱分析。有些γ射线暴谱非常硬，其谱峰能量高于BATSE LAD通带极限$\sim$ 2 MeV。在这种情况下，它们的高能谱参数（峰值能量和高能幂律指数）不能单独由BATSE LAD数据充分约束。利用EGRET的TASC量能计在多MeV能带观测到几十个明亮的BATSE伽玛暴，有效面积大，能量分辨率高。因此，结合BATSE和TASC数据，提供了跨越四十年能量（$30 $ keV $-200 $ MeV）的光谱，允许具有良好统计的宽带光谱分析。研究GRB瞬发辐射的这种宽带高能谱是至关重要的，因为它们为理解其伽马射线发射机制提供了关键线索。在15个GRB谱中，我们发现了两个具有显著高能过剩的情况，以及另一个具有极高峰值能量（\epeak $\gtrsim$ 170 MeV）的情况。在MeV能量及以上观测到的伽马射线暴数量非常有限，只有少数仪器能够以如此高的灵敏度观测到这一能量带的伽马射线暴。因此，我们在这里提出的分析结果也应该有助于预测伽玛暴观测与当前和未来的高能仪器，如AGILE和GLAST，以及地面甚高能望远镜。

英文摘要：

We present the spectral analysis of duration-integrated broadband spectra (in $\sim30 $keV$-200 $MeV) of 15 bright BATSE gamma-ray bursts (GRBs). Some GRB spectra are very hard, with their spectral peak energies being above the BATSE LAD passband limit of $\sim$2 MeV. In such cases, their high-energy spectral parameters (peak energy and high-energy power-law indices) cannot be adequately constrained by BATSE LAD data alone. A few dozen bright BATSE GRBs were also observed with EGRET's calorimeter, TASC, in multi-MeV energy band, with a large effective area and fine energy resolution. Combining the BATSE and TASC data, therefore, affords spectra that span four decades of energy ($30 $keV$-200 $MeV), allowing for a broadband spectral analysis with good statistics. Studying such broadband high-energy spectra of GRB prompt emission is crucial, as they provide key clues to understanding its gamma-ray emission mechanism. Among the 15 GRB spectra, we found two cases with a significant high-energy excess, and another case with a extremely high peak energy (\epeak $\gtrsim$ 170 MeV). There have been very limited number of GRBs observed at MeV energies and above, and only a few instruments have been capable of observing GRBs in this energy band with such high sensitivity. Thus, our analysis results presented here should also help predict GRB observations with current and future high-energy instruments such as AGILE and GLAST, as well as with ground-based very-high-energy telescopes.

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