The Day-long, Repeating GRB 250702B: A Unique Extragalactic Transient

Abstract γ -ray bursts (GRBs) are singular outbursts of high-energy radiation with durations typically lasting from milliseconds to minutes and, in extreme cases, a few hours. They are attributed to the catastrophic outcomes of stellar-scale events and, as such, are not expected to recur. Here, we present observations of the exceptional GRB 250702B (formerly GRB 250702BDE) which triggered the Fermi GRB monitor on three occasions over several hours, and which was detected in soft X-rays by the Einstein Probe several hours before the γ -ray triggers (EP 250702a). We present the discovery of an extremely red infrared counterpart of the event with the Very Large Telescope, as well as radio observations from MeerKAT. Hubble Space Telescope observations pinpoint the source to a nonnuclear location in a host galaxy with complex morphology, implying GRB 250702B is an extragalactic event. The multiwavelength counterpart is well described with standard afterglow models at a relatively low redshift z ∼ 0.3, but the prompt emission does not readily fit within the expectations for either collapsar or merger-driven GRBs. Indeed, a striking feature of the multiple prompt outbursts is that the third occurs at an integer multiple of the interval between the first two. Although not conclusive, this could be indicative of periodicity in the progenitor system. We discuss several possible scenarios to explain the exceptional properties of the burst, which suggest that either a very unusual collapsar or the tidal disruption of a white dwarf by an intermediate-mass black hole are plausible explanations for this unprecedented GRB.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-08-29
DOI
https://doi.org/10.3847/2041-8213/adf8e1
Citations
11
Primary Topic
Gamma-ray bursts and supernovae
Type
article
Field-Weighted Citation Impact
12.70

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article

The Day-long, Repeating GRB 250702B: A Unique Extragalactic Transient

Francesco Carotenuto, J. Hjorth, A. Melandri, P. Jakobsson et al.
11 citations
The Astrophysical Journal Letters
Gamma-ray bursts and supernovae
12.70
article

The Day-long, Repeating GRB 250702B: A Unique Extragalactic Transient

Francesco Carotenuto, J. Hjorth, A. Melandri, P. Jakobsson, Rob A. J. Eyles-Ferris, Albert Sneppen, Benjamin Schneider, G. Pugliese, P. G. Jonker, A. de Ugarte Postigo, D. Watson, F. E. Bauer, A. J. Levan, A. Martín-Carrillo, P. T. O’Brien, G. Tagliaferri, M. de Pasquale, T. Laskar, Benjamin P. Gompertz, D. Malesani, V. D’Elia, N. R. Tanvir, Laura Cotter, J. Sánchez-Sierras, Joe Bright, S. Piranomonte, Gavin P. Lamb, Jie An, D. H. Hartmann, Amit Kumar, J. Quirola-Vásquez, A A Chrimes, D. Xu, Luca Izzo, Steve Schulze, S. D. Vergani, A. Saccardi, Jillian Rastinejad, S. Campana, R. L. C. Starling, M. E. Ravasio, Joyce N. D. van Dalen, Dimple Dimple, G Corcoran, Makenzie E. Wortley
article en
11 citations

Abstract

Abstract γ -ray bursts (GRBs) are singular outbursts of high-energy radiation with durations typically lasting from milliseconds to minutes and, in extreme cases, a few hours. They are attributed to the catastrophic outcomes of stellar-scale events and, as such, are not expected to recur. Here, we present observations of the exceptional GRB 250702B (formerly GRB 250702BDE) which triggered the Fermi GRB monitor on three occasions over several hours, and which was detected in soft X-rays by the Einstein Probe several hours before the γ -ray triggers (EP 250702a). We present the discovery of an extremely red infrared counterpart of the event with the Very Large Telescope, as well as radio observations from MeerKAT. Hubble Space Telescope observations pinpoint the source to a nonnuclear location in a host galaxy with complex morphology, implying GRB 250702B is an extragalactic event. The multiwavelength counterpart is well described with standard afterglow models at a relatively low redshift z ∼ 0.3, but the prompt emission does not readily fit within the expectations for either collapsar or merger-driven GRBs. Indeed, a striking feature of the multiple prompt outbursts is that the third occurs at an integer multiple of the interval between the first two. Although not conclusive, this could be indicative of periodicity in the progenitor system. We discuss several possible scenarios to explain the exceptional properties of the burst, which suggest that either a very unusual collapsar or the tidal disruption of a white dwarf by an intermediate-mass black hole are plausible explanations for this unprecedented GRB.

The Astrophysical Journal LettersVol. 990(1)
National Aeronautics and Space Administration, Northwestern University, Aarhus Universitet, Villum Fonden, Space Telescope Science Institute, UK Research and Innovation, Leverhulme Trust, European Commission, National Research Foundation, Agence Nationale de la Recherche, Danmarks Grundforskningsfond, Irish Research Council, Centre National d’Etudes Spatiales, Max-Planck-Gesellschaft, European Southern Observatory, Universitetet i Oslo, Háskóli Íslands, Turun Yliopisto, Stockholms Universitet, Instituto de Astrofísica de Canarias, Science and Technology Facilities Council
Openalex Percentile: Top 1%
Gamma-ray bursts and supernovae
12.70
DOIOpen Access PDFOpenAlex
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