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arXiv 0812.2470astro-ph
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最高红移伽马射线暴的起源

On The Origin Of The Highest Redshift Gamma-Ray Bursts

Krzysztof Belczynski, Daniel E. Holz, Chris L. Fryer, Edo Berger, Dieter H. Hartmann, Brian O'Shea

摘要:

GRB 080913和GRB 090423是迄今为止已知的最遥远的伽马射线暴(GRB),光谱测定的红移分别为z=6.7和z=8.1。在宇宙的这个早期阶段对爆发的探测极大地限制了伽马射线暴及其前身的性质。我们对早期恒星的形成和演化进行了总体综合研究,并计算了高红移下短持续时间和长持续时间的伽玛暴的形成率。第二星族恒星的伽玛暴速率峰值出现在z=7时,对于一个有效/快速混合的金属模型,而对于一个低效/缓慢的金属丰度演化模型,它出现在z=3时。结果表明,在红移范围6<z<10内,无论金属丰度演化模型如何,基本上所有的伽玛暴都起源于星族II星。这些恒星(金属丰度小,但不为零)是这一时期最有可能产生长伽玛暴和短伽玛暴(NS-NS或BH-NS合并)的祖先。虽然预测的内在率长和短的伽马射线暴是类似的,在这些高红移,观测选择效应导致更高(10倍)的观测率长伽马射线暴。我们的结论是,最近观察到的两个高Z伽玛暴事件是最有可能的长伽玛暴起源于人口II的双星。

英文摘要:

GRB 080913 and GRB 090423 are the most distant gamma-ray bursts (GRBs) known to-date, with spectroscopically determined redshifts of z=6.7 and z=8.1, respectively. The detection of bursts at this early epoch of the Universe significantly constrains the nature of GRBs and their progenitors. We perform population synthesis studies of the formation and evolution of early stars, and calculate the resulting formation rates of short and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z=7 for a model with efficient/fast mixing of metals, while it is found at z=3 for an inefficient/slow metallicity evolution model. We show that in the redshift range 6<z<10 essentially all GRBs originate from Population II stars, regardless of metallicity evolution model. These stars (having small, but non-zero metallicity) are the most likely progenitors for both long GRBs (collapsars) and short GRBs (NS-NS or BH-NS mergers) at this epoch. Although the predicted intrinsic rates of long and short GRBs are similar at these high redshifts, observational selection effects lead to higher (factor of 10) observed rates for long GRBs. We conclude that the two recently observed high-z GRB events are most likely long GRBs originating from Population II collapsars.

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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