Search for the signatures of a new-born black hole from the collapse of a supra-massive millisecond magnetar in short GRB light curves

DOI: 
10.1093/mnras/stx3229
Publication date: 
21/03/2018
Main author: 
Zhang Q.
IAA authors: 
Zhang, B.B.
Authors: 
Zhang Q., Lei W.H., Zhang B.B., Chen W., Xiong S.L., Song L.M.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Volume: 
475
Pages: 
266-276
Number: 
stx3229
Abstract: 
'Internal plateau' followed by a sharp decay is commonly seen in short gamma-ray burst (GRB) light curves. The plateau component is usually interpreted as the dipole emission from a supra-massive magnetar, and the sharp decay may imply the collapse of the magnetar to a black hole (BH). Fall-back accretion on to the new-born BH could produce long-lasting activities via the Blandford-Znajek (BZ) process. The magnetic flux accumulated near the BH would be confined by the accretion discs for a period of time. As the accretion rate decreases, the magnetic flux is strong enough to obstruct gas infall, leading to a magnetically arrested disc. Within this scenario, we show that the BZ process could produce two types of typical X-ray light curves: type I exhibits a long-lasting plateau, followed by a power-law (PL) decay with slopes ranging from 5/3 to 40/9; type II shows roughly a single PL decay with a slope of 5/3. The former requires low magnetic field strength, while the latter corresponds to relatively high values. We search for such signatures of the new-born BH from a sample of short GRBs with an internal plateau, and find two candidates: GRB 101219A and GRB 160821B, corresponding to type II and type I light curves, respectively. It is shown that our model can explain the data very well. © 2017 The Author(s).
Database: 
SCOPUS
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2018MNRAS.475..266Z/abstract
ADS Bibcode: 
2018MNRAS.475..266Z
Keywords: 
Accretion, accretion discs; Gamma-ray burst: individual: (GRB 101219A, GRB 160821B); Stars: magnetars