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arXiv 2107.00533astro-ph.HEgr-qc
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中子星合并双星中潮汐$g$模式共振的广义相对论处理。II。作为短伽马射线暴的前兆耀斑的触发器

General-relativistic treatment of tidal $g$-mode resonances in coalescing binaries of neutron stars. II. As triggers for precursor flares of short gamma-ray bursts

Hao-Jui Kuan, Arthur G. Suvorov, Kostas D. Kokkotas

摘要:

在某些短的伽马射线暴中,观测到了在主事件发生前$\sim$秒出现的前兆耀斑。当轨道频率为几百赫兹时,这些耀斑可能与内旋的最后几个周期有关。在这些最后的周期中,潮汐力可以共振地激发吸气恒星中的准正常模式,导致其振幅迅速增加。已经表明,这些模式可以施加足够强的应变到中子星地壳煽动屈服。由于$g$ -模式的典型频率是$\sim 100\text{ Hz}$,它们与轨道频率的共振与前兆定时相匹配,因此需要进一步研究。采用现实的状态方程和解决的广义相对论脉动方程,我们研究了$g$模式的共振在合并准圆双星,在那里我们考虑不同的恒星自转速率,分层程度,和磁场结构。我们表明,对于某些恒星参数的组合,共振激发的$g_1$ -和$g_2$ -模式可能会导致地壳破裂和触发前兆耀斑。

英文摘要:

In some short gamma-ray bursts, precursor flares occurring $\sim$ seconds prior to the main episode have been observed. These flares may then be associated with the last few cycles of the inspiral when the orbital frequency is a few hundred Hz. During these final cycles, tidal forces can resonantly excite quasi-normal modes in the inspiralling stars, leading to a rapid increase in their amplitude. It has been shown that these modes can exert sufficiently strong strains onto the neutron star crust to instigate yieldings. Due to the typical frequencies of $g$-modes being $\sim 100\text{ Hz}$, their resonances with the orbital frequency match the precursor timings and warrant further investigation. Adopting realistic equations of state and solving the general-relativistic pulsation equations, we study $g$-mode resonances in coalescing quasi-circular binaries, where we consider various stellar rotation rates, degrees of stratification, and magnetic field structures. We show that for some combination of stellar parameters, the resonantly excited $g_1$- and $g_2$-modes may lead to crustal failure and trigger precursor flares.

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