1. Physical Implications of the Subthreshold GRB GBM-190816 and Its Associated Subthreshold Gravitational-wave Event.
- Author
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Yang, Yi-Si, Zhong, Shu-Qing, Zhang, Bin-Bin, Wu, Shichao, Zhang, Bing, Yang, Yu-Han, Cao, Zhoujian, Gao, He, Zou, Jin-Hang, Wang, Jie-Shuang, Lü, Hou-Jun, Cang, Ji-Rong, and Dai, Zi-Gao
- Subjects
GAMMA ray bursts ,GRAVITATIONAL waves ,ENERGY dissipation ,SIGNAL-to-noise ratio ,CONFIDENCE intervals ,GLIOBLASTOMA multiforme ,LUMINOSITY - Abstract
The LIGO/Virgo and Fermi collaborations recently reported a possible joint detection of a subthreshold gravitational-wave (GW) event and a subthreshold gamma-ray burst (GRB), GBM-190816, that occurred 1.57 s after the merger. We perform an independent analysis of the publicly available data and investigate the physical implications of this potential association. By carefully studying the following properties of GBM-190816 using Fermi/GBM data, including signal-to-noise ratio, duration, f-parameter, spectral properties, energetic properties, and its compliance with some GRB statistical correlations, we confirm that this event is likely a typical short GRB. Assuming its association with the subthreshold GW event, the inferred luminosity is erg s
−1 . Based on the available information of the subthreshold GW event, we infer the mass ratio q of the compact binary as (90% confidence interval) according to the reported range of luminosity distance. If the heavier compact object has a mass >3 solar masses, q can be further constrained to. The leading physical scenario invokes an NS–BH merger system with the NS tidally disrupted. Within this scenario, we constrain the physical properties of such a system (including mass ratio q, the spin parameters, and the observer's viewing angle) to produce a GRB. The GW data may also allow an NS–BH system with no tidal disruption of the NS (the plunge events) or a BH–BH merger. We apply the charged compact binary coalescence theory (for both a constant charge and an increasing charge for the merging members) to derive the model parameters to account for GBM-190816 and found that the required parameters are extreme. Finally, we argue that the fact that the observed GW–GRB delay timescale is comparable to that of GW170817/GRB 170817A suggests that the GW–GRB time delay of these two cases is mainly defined by the timescale for the jet to propagate to the energy dissipation/GRB emission site. [ABSTRACT FROM AUTHOR]- Published
- 2020
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