GRB 250702B: Discovery of a Gamma-Ray Burst from a Black Hole Falling into a Star

Neights, E ORCID: 0009-0005-0762-4507, Burns, E, Fryer, CL, Svinkin, D, Bala, S, Hamburg, R, Gill, R, Negro, M, Masterson, M, DeLaunay, J, Lawrence, DJ, Abrahams, SED, Kawakubo, Y, Beniamini, P ORCID: 0000-0001-7833-1043, Diget, CA, Frederiks, D, Goldsten, J, Goldstein, A ORCID: 0000-0002-0587-7042, Hall-Smith, AD, Kara, E ORCID: 0000-0003-0172-0854 et al GRB 250702B: Discovery of a Gamma-Ray Burst from a Black Hole Falling into a Star. Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711

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Abstract

Gamma-ray bursts are the most luminous electromagnetic events in the universe. Their prompt gamma-ray emission has typical durations between a fraction of a second and several minutes. A rare subset of these events have durations in excess of a thousand seconds, referred to as ultra-long gamma-ray bursts. Here, we report the discovery of the longest gamma-ray burst ever seen with a ∼25,000 s gamma-ray duration, GRB 250702B, and characterize this event using data from four instruments in the InterPlanetary Network and the Monitor of All-sky X-ray Image. We find a hard spectrum, subsecond variability, and high total energy, which are only known to arise from ultrarelativistic jets powered by a rapidly-spinning stellar-mass central engine. These properties and the extreme duration are together incompatible with all confirmed gamma-ray burst progenitors and nearly all models in the literature. This burst is naturally explained with the helium merger model, where a field binary ends when a black hole falls into a stripped star and proceeds to consume and explode it from within. Under this paradigm, GRB 250702B adds to the growing evidence that helium stars expand and that some ultra-long GRBs have similar evolutionary pathways as collapsars, stellar-mass gravitational wave sources, and potentially rare types of supernovae.

Item Type:	Article
Additional Information:	This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Published by Oxford University Press.
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Date of acceptance:	14 November 2025
Date of first compliant Open Access:	17 November 2025
Date Deposited:	17 Nov 2025 14:44
Last Modified:	17 Nov 2025 15:00
DOI or ID number:	10.1093/mnras/staf2019
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27579

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