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Ultradeep Cover: An Exotic and Jetted Tidal Disruption Event Candidate Disguised as a Gamma-Ray Burst

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posted on 2024-04-26, 14:56 authored by RAJ Eyles-Ferris, CJ Nixon, ER Coughlin, PT O’Brien

Gamma-ray bursts (GRBs) are traditionally classified as either short GRBs with durations ≲2 s that are powered by compact object mergers or long GRBs with durations ≳2 s that are powered by the deaths of massive stars. Recent results, however, have challenged this dichotomy and suggest that there exists a population of merger-driven long bursts. One such example, GRB 191019A, has a t 90 ≈ 64 s, but many of its other properties—including its host galaxy, afterglow luminosity and lack of associated supernova—are more consistent with a short GRB. Here we propose an alternative interpretation: that GRB 191019A (which is located in the nucleus of its host) is an atypical jetted tidal disruption event (TDE). In particular, we suggest the short timescale and rapid decline, not expected for standard TDEs, are the result of an “ultradeep” encounter, in which the star came well within the tidal radius of the black hole and promptly self-intersected, circularized, accreted, and launched a relativistic outflow. This model reproduces the timescale and luminosity through a prompt super-Eddington accretion phase and accounts for the lack of late optical emission. This would make GRB 191019A only the fifth jetted TDE and the first discovered ultradeep TDE. The ultradeep TDE model can be distinguished from merger-driven long GRBs via the soft X-ray flash that results from prompt self-intersection of the debris stream; the detection of this flash will be possible with wide-field and soft-X-ray satellites such as Einstein Probe or SVOM.

Funding

We thank EREF for valuable discussion and AJREF for insight at only six months old. We also thank the anonymous reviewer for helpful comments. R.A.J.E.F. acknowledges support from the UK Space Agency and the European Union's Horizon 2020 Programme under the AHEAD2020 project (grant agreement number 871158). C.J.N. acknowledges support from the Science and Technology Facilities Council (grant No. ST/Y000544/1) and from the Leverhulme Trust (grant No. RPG-2021-380). E.R.C. acknowledges support from the National Science Foundation through grant AST-2006684.

History

Author affiliation

College of Science & Engineering/Physics & Astronomy

Version

  • VoR (Version of Record)

Published in

The Astrophysical Journal Letters

Volume

965

Issue

2

Pagination

L20 - L20

Publisher

American Astronomical Society

issn

2041-8205

eissn

2041-8213

Copyright date

2024

Available date

2024-04-26

Language

en

Deposited by

Professor Paul O'Brien

Deposit date

2024-04-25

Rights Retention Statement

  • No

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