Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts
Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts
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DOI：
10.1093/pasj/psw009
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发表时间：
2016-06
影响因子：
2.3
通讯作者：
N. Ohmori;K. Yamaoka;M. Ohno;S. Sugita;R. Kinoshita;Y. Nishioka;K. Hurley;Y. Hanabata;M. Tashiro;J. Enomoto;Takeshi Fujinuma;Y. Fukazawa;W. Iwakiri;T. Kawano;M. Kokubun;K. Makishima;S. Matsuoka;T. Nagayoshi;Y. Nakagawa;Souhei Nakaya;K. Nakazawa;Tadayuki Takahashi;S. Takeda;Y. Terada;Y. Urata;Seiya Yabe;T. Yasuda;M. Yamauchi
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文献类型：
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作者：
N. Ohmori;K. Yamaoka;M. Ohno;S. Sugita;R. Kinoshita;Y. Nishioka;K. Hurley;Y. Hanabata;M. Tashiro;J. Enomoto;Takeshi Fujinuma;Y. Fukazawa;W. Iwakiri;T. Kawano;M. Kokubun;K. Makishima;S. Matsuoka;T. Nagayoshi;Y. Nakagawa;Souhei Nakaya;K. Nakazawa;Tadayuki Takahashi;S. Takeda;Y. Terada;Y. Urata;Seiya Yabe;T. Yasuda;M. Yamauchi
本文报道了2005年8月4日至2010年12月29日由日本朱雀宽频全天监测仪（WAM）观测到的1464次伽玛射线暴（GRBs）的t90和t50持续时间分布及其与光谱硬度的关系。在50 - 120,120 - 250,250 - 550 keV三个能量范围内，持续时间分布明显为双峰分布，但在550-5000 keV范围内则不清楚，可能是因为样本量有限。WAM持续时间随能量的增加呈- 0.058（- 0.034,+0.033）的幂律指数递减。硬度-持续时间关系揭示了短硬暴和长软暴的存在。随着能量的增加，短事件与长事件之比趋于较高。我们将WAM分布与其他八个GRB仪器测量的分布进行了比较。wamt90分布与INTEGRAL/SPI-ACS和Granat/PHEBUS非常相似，与Swift/BAT分布最不可能匹配。WAM的短：长事件比率（0.25:0.75）与Swift/BAT（0.08:0.92）有很大不同，但与CGRO/BATSE（0.25:0.75）几乎相同。为了解释BAT的这种差异，我们研究了三种影响：BAT触发类型、持续时间的能量依赖以及BAT和WAM之间的检测灵敏度差异。因此，我们发现比值差异主要可以用能量依赖来解释，包括短伽马射线暴的软扩展发射，以及可以探测弱/长伽马射线暴的BAT的灵敏度更高。通过触发效率曲线的计算，确定了BATSE和WAM具有相同的短：长事件比的原因。
We report on theT90andT50duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50–120, 120–250, and 250–550 keV), but is unclear in the 550–5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of −0.058(−0.034, +0.033). The hardness–duration relation reveals the presence of short–hard and long–soft GRBs. The short:long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAMT90distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short:long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity differences between BAT and WAM. As a result, we found that the ratio difference could be explained mainly by energy dependence including soft extended emissions for short GRBs and much better sensitivity for BAT which can detect weak/long GRBs. The reason for the same short:long event ratio for BATSE and WAM was confirmed by calculation using the trigger efficiency curve.