When Did the Remnant of GW170817 Collapse to a Black Hole?

被引：89

作者：

Gill, Ramandeep ^{[1
,2
]}

Nathanail, Antonios ^{[1
]}

Rezzolla, Luciano ^{[1
]}

机构：

[1] Inst Theoret Phys, Max von Laue Str 1, D-60438 Frankfurt, Germany

[2] Open Univ Israel, Dept Nat Sci, 1 Univ Rd,POB 808, IL-4353701 Raanana, Israel

来源：

ASTROPHYSICAL JOURNAL | 2019年 / 876卷 / 02期

基金：

欧盟地平线“2020”;

关键词：

gamma-ray burst: general; gravitational waves; stars: jets; stars: neutron; stars:; winds; outflows; GAMMA-RAY BURSTS; R-PROCESS NUCLEOSYNTHESIS; NEUTRINO-DRIVEN WINDS; EXTENDED EMISSION; MAGNETIC-FIELDS; MASS EJECTION; MAXIMUM MASS; OBSERVATIONAL EVIDENCE; STRUCTURED JETS; STAR MERGERS;

D O I：

10.3847/1538-4357/ab16da

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The main hard pulse of prompt gamma-ray emission in GRB 170817A had a duration of similar to 0.5 s, and its onset was delayed with respect to the gravitational-wave chirp signal by t(del) approximate to 1.74 s. Detailed follow-up of the subsequent broadband kilonova emission revealed a two-component ejecta-a lanthanide-poor ejecta with mass M-ej,M-blue approximate to 0.025 M-circle dot that powered the early but rapidly fading blue emission and a lanthanide-rich ejecta with mass M-ej,M-red approximate to 0.04 M-circle dot that powered the longer-lasting redder emission. Both the prompt gamma-ray onset delay and the existence of the blue ejecta with a modest electron fraction, 0.2 less than or similar to Y-e less than or similar to 0.3, can be explained if the collapse to a black hole (BH) was delayed by the formation of a hypermassive neutron star. Here we determine the survival time of the merger remnant by combining two different constraints, namely, the time needed to produce the requisite blue-ejecta mass and that necessary for the relativistic jet to bore its way out of the expanding ejecta. In this way, we determine that the remnant of GW170817 must have collapsed to a BH after t(coll) = 0.98(-0.26)(+0.31)s. We also discuss how future detections and the delays between the gravitational and electromagnetic emissions can be used to constrain the properties of the merged object.

引用

页数：16

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