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arXiv 1209.4097astro-ph.HEastro-ph.COgr-qc
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黑洞-中子星并合产生的短伽玛暴中的脉动

Pulsations in Short GRBs from Black Hole-Neutron Star Mergers

Nicholas Stone, Abraham Loeb, Edo Berger

摘要:

短伽马射线暴(SGRB)的精确起源一直是相对论天体物理学中的一个重要问题。越来越多的观测证据表明,一个紧凑的双星系统合并为大多数SGRB的来源,但目前还不清楚如何区分观测中子星的祖先和黑洞-中子星的祖先。我们建议喷流进动的准周期信号作为起源于混合双星系统的SGRB的观测签名,并量化能够产生SGRB的混合双星的比例,以及进动幅度和周期的分布。在恒星质量的黑洞视界外破坏中子星的固有困难使喷流进动信号偏向于低振幅和高频率。通常预计进动周期为~ 0.01-0.1 s,盘-BH自旋错位为~10度,尽管足够高的粘度可能会阻止SGRB期间多个进动周期的积累。旋进喷流自然会比标准SGRB喷流在天空中覆盖更大的立体角,从而增强了即时发射和光学余辉的可观测性。

英文摘要:

The precise origin of short gamma ray bursts (SGRBs) remains an important open question in relativistic astrophysics. Increasingly, observational evidence suggests the merger of a binary compact object system as the source for most SGRBs, but it is currently unclear how to distinguish observationally between a binary neutron star progenitor and a black hole-neutron star progenitor. We suggest the quasi-periodic signal of jet precession as an observational signature of SGRBs originating in mixed binary systems, and quantify both the fraction of mixed binaries capable of producing SGRBs, and the distributions of precession amplitudes and periods. The difficulty inherent in disrupting a neutron star outside the horizon of a stellar-mass black hole biases the jet precession signal towards low amplitude and high frequency. Precession periods of ~ 0.01-0.1 s and disk-BH spin misalignments ~10 degrees are generally expected, although sufficiently high viscosity may prevent the accumulation of multiple precession periods during the SGRB. The precessing jet will naturally cover a larger solid angle in the sky than would standard SGRB jets, enhancing observability for both prompt emission and optical afterglows.

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