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arXiv 2009.10258astro-ph.HE
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快速伽马射线暴的谱峰能量

On Spectral Peak Energy of Swift Gamma-Ray Bursts

Z. B. Zhang, M. Jiang, Y. Zhang, K. Zhang, X. J. Li, Q. Zhang

摘要:

由于\textit{Swift} /BAT的能带较窄,目前还存在一些亟待解决的问题。我们系统地研究了283个\textit{Swift} /BAT伽马射线暴的性质,这些暴具有测量良好的谱峰能量($E_{\text p}$),置信度大于3 $σ$。有趣的是,\textit{Swift}爆发的持续时间($T_{90}$)分布仍然表现出明显的双峰性,其可靠的边界为$T_{90}\simeq$ 1.06 s,而不是先前污染样品(包括没有峰谱的爆发)的2 s,这与Fermi/GBM和\textit{Swift} /BAT星表中的$\sim$ 1.27 s和$\sim$ 0.8 s非常接近。\textit{Swift} /BAT短和长爆发具有相当的平均$E_{\text p}$值,每个中的$87^{+112}_{-49}$和$85^{+101}_{-46}$ keV,类似于对于两种类型的BATSE爆发所发现的,这表明传统的短硬/长软方案对于探测器的特定能量窗口可能是不成立的。在统计方面,我们也研究了不同方法对$E_{\text p}$估计的一致性,发现贝叶斯方法和BAND函数总是能给出一致的估计。相比之下,常用的截止幂律模型与其他两种方法相匹配,用于较低的$E_{\text p}$,并且将高估$E_{\text p}$超过70%,因为$E_{\text p}>$ 100 keV。X射线闪光、富X射线爆发和经典伽马射线暴的峰值能量可能具有从热主导到非热主导辐射机制的演化结果。最后,我们发现,$E_{\text p}$和观测的注量($S_γ$)在观察员框架相关的$E_p\simeq [S_γ/(10^{-5} erg\ cm^{-2})]^{0.28}\times 117.5^{+44.7}_{-32.4}$ keV建议是一个有用的指示GRB峰值能量。

英文摘要:

Owing to narrow energy band of \textit{Swift}/BAT, several urgent issues are required to pay more attentions but unsolved so far. We systematically study the properties of a refined sample of 283 \textit{Swift}/BAT gamma-ray bursts with well-measured spectral peak energy ($E_{\text p}$) at a high confidence level larger than 3$σ$. It is interestingly found that duration ($T_{90}$) distribution of \textit{Swift} bursts still exhibits an evident bimodality with a more reliable boundary of $T_{90}\simeq$1.06 s instead of 2 s for previously contaminated samples including bursts without well-peaked spectra, which is very close to $\sim$1.27 s and $\sim$0.8 s suggested by some authors for Fermi/GBM and \textit{Swift}/BAT catalogs, respectively. The \textit{Swift}/BAT short and long bursts have comparable mean $E_{\text p}$ values of $87^{+112}_{-49}$ and $85^{+101}_{-46}$ keV in each, similar to what found for both types of BATSE bursts, which manifests the traditional short-hard/long-soft scheme may not be tenable for the certain energy window of a detector. In statistics, we also investigate the consistency of distinct methods for the $E_{\text p}$ estimates and find that Bayesian approach and BAND function can always give consistent evaluations. In contrast, the frequently-used cut-off power-law model matches two other methods for lower $E_{\text p}$ and will overestimate the $E_{\text p}$ more than 70\% as $E_{\text p}>$100 keV. Peak energies of X-ray flashes, X-ray rich bursts and classical gamma-ray bursts could have an evolutionary consequence from thermal-dominated to non-thermal-dominated radiation mechanisms. Finally, we find that the $E_{\text p}$ and the observed fluence ($S_γ$) in the observer frame are correlated as $E_p\simeq [S_γ/(10^{-5} erg\ cm^{-2})]^{0.28}\times 117.5^{+44.7}_{-32.4}$ keV proposed to be an useful indicator of GRB peak energies.

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