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arXiv 1506.07862astro-ph.HEphysics.space-ph
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短暴与长暴的界限

On the limit between short and long GRBs

Mariusz Tarnopolski

摘要:

到目前为止,已经确定了两类伽玛暴,这是毫无疑问的,并规定了不同的物理场景- NS-NS或NS-BH合并,以及大质量恒星的崩溃,分别为短和长伽玛暴。通过观测持续时间$T_{90}$的双峰分布推断了两个不同种群的存在,并且通过在BATSE 1B的分组数据中的两个峰值之间拟合抛物线获得了短和长GRB之间的常用$2\,{\rm s}$极限。在此,通过极大似然(ML)方法,将两个高斯的混合拟合到来自BATSE、$Swift$、$BeppoSAX$和$Fermi$的数据集,以搜索可能用作两个GRB类的新的、更适当的极限的局部最小值。结果发现,$Swift$和$BeppoSAX$分布是单峰的,因此不存在局部最小值,$Fermi$与传统的限制是一致的,而BATSE给出的限制显着更长(等于$3.38\pm 0.27\,{\rm s}$)比$2\,{\rm s}$。这些新的值改变了所检查的样品中短和长伽玛暴的比例,并意味着所观察到的$T_{90}$持续时间是依赖于探测器的,因此,由于它们的仪器规格不同,没有通用的限制值可能适用于所有的卫星。正因为如此,再加上两个高斯分量的强烈重叠,短伽玛暴与并合、长伽玛暴与双星的直接关联是不明确的。

英文摘要:

Two classes of GRBs have been identified thus far without doubt and are prescribed to different physical scenarios -- NS-NS or NS-BH mergers, and collapse of massive stars, for short and long GRBs, respectively. The existence of two distinct populations was inferred through a bimodal distribution of the observed durations $T_{90}$, and the commonly applied $2\,{\rm s}$ limit between short and long GRBs was obtained by fitting a parabola between the two peaks in binned data from BATSE 1B. Herein, by means of a maximum likelihood (ML) method a mixture of two Gaussians is fitted to the datasets from BATSE, $Swift$, $BeppoSAX$, and $Fermi$ in search for a local minimum that might serve as a new, more proper, limit for the two GRB classes. It is found that $Swift$ and $BeppoSAX$ distributions are unimodal, hence no local minimum is present, $Fermi$ is consistent with the conventional limit, whereas BATSE gives the limit significantly longer (equal to $3.38\pm 0.27\,{\rm s}$) than $2\,{\rm s}$. These new values change the fractions of short and long GRBs in the samples examined, and imply that the observed $T_{90}$ durations are detector dependent, hence no universal limiting value may be applied to all satellites due to their different instrument specifications. Because of this, and due to the strong overlap of the two-Gaussian components, the straightforward association of short GRBs to mergers and long ones to collapsars is ambiguous.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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