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arXiv 1602.07698astro-ph.HE
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恒星致密天体的微潮汐破裂事件和超长伽玛暴的产生

Micro - tidal disruption events by stellar compact objects and the production of ultra-long GRBs

Hagai B. Perets, Zhuo Li, James C. Lombardi, Stephen R. Milcarek

摘要:

我们探索恒星/行星的完整/部分潮汐破裂事件(TDEs)的恒星致密物体(黑洞; BH;或中子星; NS),我们称之为微TDEs。质量为$M_{\star}$的恒星/行星的破坏可能会导致BH/NS周围形成碎片盘。碎片中一小部分$(f_{acc}=0.1$的有效吸积可能会产生明亮的高能长X射线/伽马射线耀斑,总能量高达$10^{3}-10^{4}\,s$尔格,可能类似于超长伽玛暴/X射线荧光。这种耀斑的能量取决于约束不良的吸积过程。如果大部分的盘物质通过强烈的外流被吹走,则可能会产生明显较暗的耀斑。我们提出了三个动力学的起源这样的中断。在第一种情况下,一颗恒星/行星在密集星团中与BH/NS近距离随机相遇后被潮汐破坏。我们估计在这种情况下,每个银河系的BH(NS)微TDE率为几个$\times10^{-6}$(几个$\times10^{-7}$)${\rm yr}^{-1}$。另一种情况涉及由于场中恒星的扰动而引起的宽伴星的相互作用,可能产生可比但较低的速率。最后,第三种情况涉及一个BH/NS,它在出生时获得了出生时的速度反冲,导致与一个双星伴星的近距离相遇和该伴星的潮汐破坏。这些事件可能与超新星有关,甚至与之前的GRB/XRF事件有关,并且可能在瞬间爆炸后数小时至数天发生;这些事件的发生率可能比从其他场景中获得的更大,这取决于之前的复杂双星恒星演化。

英文摘要:

We explore full/partial tidal disruption events (TDEs) of stars/planets by stellar compact objects (Black holes; BHs; or neutron stars; NSs), which we term micro-TDEs. Disruption of a star/planet with mass $M_{\star}$ may lead to the formation of a debris disk around the BH/NS. Efficient accretion of a fraction $(f_{acc}=0.1$ of the debris may then give rise to bright energetic long ($10^{3}-10^{4}\,s$), X-ray/Gamma-ray flares, with total energies of up to $(f_{acc}/0.1)\times10^{52}\,(M_{\star}/{0.6\,M_{\odot}})\,$ergs, possibly resembling ultra-long GRBs/XRFs. The energy of such flares depends on the poorly constrained accretion processes. Significantly fainter flares might be produced if most of the disk mass is blown away through strong outflows. We suggest three dynamical origins for such disruptions. In the first, a star/planet is tidally disrupted following a close random encounter with a BH/NS in a dense cluster. We estimate the BH (NS) micro-TDE rates from this scenario to be few$\times10^{-6}$ (few$\times10^{-7}$) ${\rm yr}^{-1}$ per Milky-Way galaxy. Another scenario involves the interaction of wide companions due to perturbations by stars in the field, likely producing comparable but lower rates. Finally, a third scenario involves a BH/NS which gain a natal velocity kick at birth, leading to a close encounter with a binary companion and the tidal disruption of that companion. Such events could be associated with a supernova, or even with a preceding GRB/XRF event, and would likely occur hours to days after the prompt explosion; the rates of such events could be larger than those obtained from the other scenarios, depending on the preceding complex binary stellar evolution.

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