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arXiv 0909.0857astro-ph.HEastro-ph.CO
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超级巨星及其X射线爆发

Supercollapsars and their X-ray Bursts

S. S. Komissarov, M. V. Barkov

摘要:

宇宙中最早的恒星质量可能非常大,可达$10^3M_\odot$。如果大量诞生,这样的大质量恒星会对随后的恒星形成产生强烈的影响,产生强烈的电离辐射,并用重元素污染原始气体。它们会留下巨大的黑洞,这些黑洞可以作为活跃星系核的超大质量黑洞的种子。考虑到预期的快速旋转,这些恒星将以超大质量双星的形式结束生命,并驱动强大的磁主导喷流。在这封信中,我们调查的可能性,观察到类似的长伽马射线暴与正常的类星体的高能发射的爆发。我们表明,在超巨星坍缩过程中,Blandford-Znajek机制可以产生强大的喷流作为几个$\times10^{52}$尔格/秒,并释放高达$10^{54}$尔格的黑洞旋转能量。由于更高的内在时间尺度和更高的红移,爆发的初始亮相可以持续大约$10^4$秒,而中央引擎将保持活跃大约一天。由于红移很高,预计爆发的光谱会很柔和,能量分布峰值在20- 30 keV左右。峰值总通量密度相对较低,为$10^{-7}{erg} {cm}^{-2} {s}^{-1}$,但并不高。如果每一个由3- $σ$宇宙学波动产生的暗物质小晕都产生一个超巨星,那么整个天空中这种爆发的频率可能达到每年几十次。

英文摘要:

The very first stars in the Universe can be very massive, up to $10^3M_\odot$. If born in large numbers, such massive stars can have strong impact on the subsequent star formation, producing strong ionising radiation and contaminating the primordial gas with heavy elements. They would leave behind massive black holes that could act as seeds for growing supermassive black holes of active galactic nuclei. Given the anticipated fast rotation, such stars would end their live as supermassive collapsars and drive powerful magnetically-dominated jets. In this letter we investigate the possibility of observing the bursts of high-energy emission similar to the Long Gamma Ray Bursts associated with normal collapsars. We show that during the collapse of supercollapsars, the Blandford-Znajek mechanism can produce jets as powerful as few$\times10^{52}$erg/s and release up to $10^{54}$erg of the black hole rotational energy. Due to the higher intrinsic time scale and higher redshift the initial bright phase of the burst can last for about $10^4$ seconds, whereas the central engine would remain active for about one day. Due to the high redshift the burst spectrum is expected to be soft, with the spectral energy distribution peaking at around 20-30keV. The peak total flux density is relatively low, $10^{-7}{erg} {cm}^{-2} {s}^{-1}$, but not prohibitive. If one supercollapsar is produced per every mini-halo of dark matter arising from the 3-$σ$ cosmological fluctuations then the whole sky frequency of such bursts could reach several tens per year.

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