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arXiv 2308.06151astro-ph.HE
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黑洞-中子星并合产生的短伽马射线暴中的准周期振荡

Quasi-periodic oscillation in short gamma-ray bursts from black hole-neutron star mergers

Yan Li, Rong-Feng Shen, Bin-Bin Zhang

AI总结:

本文提出黑洞-中子星并合中吸积盘因 Lense-Thirring 进动带动喷流准周期摆动,可在短伽马射线暴光变曲线中产生约0.01-0.1秒的准周期调制,为识别自转-轨道错位并合系统提供新方法。

摘要:

短时标伽马射线暴(sGRBs)通常被归因于双中子星(NSs)的并合或中子星与黑洞(BH)的并合。前者已由事件 GW170817 得到证实,而后者仍缺乏直接证据。本文考虑后一种情形:一颗中子星被快速自转的低质量黑洞潮汐瓦解,物质吸积到黑洞上并驱动相对论性喷流,从而产生短伽马射线暴。并合双星的轨道很可能与黑洞自转方向存在夹角。因此,黑洞周围的 Lense-Thirring 进动可能使超爱丁顿吸积的厚盘以刚体方式进动。我们提出,初始与黑洞自转轴对齐的喷流会被来自吸积盘的外流偏转并准直,从而被迫随盘一起进动。这将在短伽马射线暴的伽马射线光变曲线中产生准周期振荡或调制,准周期约为 $\sim 0.01-0.1$ 秒。这种调制的出现可能相对于光变曲线的触发时刻有所延迟。这一特征为黑洞-中子星并合所独有,可能已在少数已观测到的短伽马射线暴(如 GRB 130310A)中显现,并且携带着并合系统的自转-轨道取向信息。识别这一特征将为揭示自转-轨道错位的黑洞-中子星并合系统提供一种新途径,而这类系统很可能被当前主要针对对齐系统的引力波搜寻策略所遗漏。

英文摘要:

Short-duration gamma-ray bursts (sGRBs) are commonly attributed to the mergers of double neutron stars (NSs) or the mergers of a neutron star with a black hole (BH). While the former scenario was confirmed by the event GW170817, the latter remains elusive. Here, we consider the latter scenario in which, a NS is tidally disrupted by a fast spinning low-mass BH and the accretion onto the BH launches a relativistic jet and hence produces a sGRB. The merging binary's orbit is likely misaligned with the BH's spin. Hence, the Lense-Thirring precession around the BH may cause a hyper-accreting thick disk to precess in a solid-body manner. We propose that a jet, initially aligned with the BH spin, is deflected and collimated by the wind from the disk, therefore being forced to precess along with the disk. This would result in a quasi-periodic oscillation or modulation in the gamma-ray light curve of the sGRB, with a quasi-period of $\sim 0.01-0.1$ s. The appearance of the modulation may be delayed respective to the triggering of the light curve. This feature, unique to the BH-NS merger, may have already revealed itself in a few observed sGRBs (such as GRB 130310A), and it carries the spin-obit orientation information of the merging system. Identification of this feature would be a new approach to reveal spin-orbit-misaligned merging BH-NS systems, which are likely missed by the current gravitational-wave searching strategy principally targeting aligned systems.

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