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arXiv 1105.3209astro-ph.HE
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雨燕1644+57:最长的伽马射线暴?

Swift 1644+57: The Longest Gamma-ray Burst?

Eliot Quataert, Dan Kasen

摘要:

斯威夫特最近发现了一个不寻常的伽马射线和X射线瞬变(Sw 1644+57),最初被确定为长持续时间的伽马射线暴(GRB)。然而,~ 10 keV的X射线发射持续了一个多月,亮度与其峰值相当。源与其宿主星系中心的天体测量重合,以及其他考虑因素,促使人们解释Sw 1644+57是由星系中心10^{6-7} M_太阳黑洞的爆发产生的。在这里,我们考虑另一种可能性,即Sw 1644+57确实是一个长持续时间的伽玛暴,尽管特别长。我们讨论的一般性质非常长的持续时间,低功率GRB样瞬变与大质量恒星的核心崩溃。中子星(磁星)的自旋下降和黑洞的吸积都可以为这样的事件提供动力。通过磁星自旋下降产生低功率、持续时间很长的GRB的要求与通过磁星自旋下降为极其明亮的超新星提供动力的要求相似,这表明这两种不寻常的瞬变类型之间可能存在联系。另外,Sw 1644+57可能与最微弱的核心坍缩爆炸有关:一颗名义上失败的超新星中旋转的红超巨星的坍缩可以为太阳质量的黑洞提供长达100天的吸积动力;黑洞吸积产生的喷流不可避免地解开了祖先的外壳,导致一次微弱的~ 10^{49}尔格爆炸。在中子星和黑洞的模型中,喷流可以在几天内穿过宿主恒星,其动力学光度约为10^{45-46}尔格/秒,足以为观测到的Sw 1644+57的发射提供动力。

英文摘要:

Swift recently discovered an unusual gamma-ray and x-ray transient (Sw 1644+57) that was initially identified as a long-duration gamma-ray burst (GRB). However, the ~ 10 keV x-ray emission has persisted for over a month with a luminosity comparable to its peak value. The astrometric coincidence of the source with the center of its host galaxy, together with other considerations, motivated the interpretation that Sw 1644+57 was produced by an outburst from a 10^{6-7} M_sun black hole at the center of the galaxy. Here we consider the alternate possibility that Sw 1644+57 is indeed a long-duration GRB, albeit a particularly long one. We discuss the general properties of very long-duration, low-power GRB-like transients associated with the core-collapse of a massive star. Both neutron star (magnetar) spindown and black hole accretion can power such events. The requirements for producing low-power, very long-duration GRBs by magnetar spindown are similar to those for powering extremely luminous supernovae by magnetar spindown, suggesting a possible connection between these two unusual types of transients. Alternatively, Sw 1644+57 be associated with the faintest core-collapse explosions: the collapse of a rotating red supergiant in a nominally failed supernova can power accretion onto a solar-mass black hole for up to ~ 100 days; the jet produced by black hole accretion inevitably unbinds the outer envelope of the progenitor, leading to a weak ~ 10^{49} erg explosion. In both neutron star and black hole models, a jet can burrow through the host star in a few days, with a kinetic luminosity ~ 10^{45-46} ergs/s, sufficient to power the observed emission of Sw 1644+57.

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