Year: 2026
Type: preprint
Abstract: While the progenitors of many long gamma-ray bursts (GRBs) are well established as the core collapse of very massive, envelope-stripped, rapidly-rotating stars, it has been suggested that bursts at the extremely long end of the duration distribution may be a separate population of `ultra-long' GRBs. With durations of thousands of seconds or more, these bursts are difficult to reconcile with the engine timescales expected from the compact Wolf-Rayet stars that are typically assumed to produce more `standard' long GRBs. Here, we present observations of GRB~220706A, where X-ray follow-up reveals flaring episodes that last until $\approx 51$ days after trigger. At the measured redshift of $z = 0.8577$, this corresponds to 27 days in the GRB rest frame, and represents the latest central engine activity ever observed in a GRB by a margin of $\approx 21$ rest-frame days. We also identify a likely supernova (SN) which, when accounting for the inferred optical extinction of $0.9 \leq A_V \leq 3.6$ mag (constrained by indirect arguments), has a peak absolute magnitude of $M_r \leq -20.25$, resembling the energetic SN\,2011kl found accompanying ultra-long GRB\,111209A, and consistent with super-luminous SNe. We discuss the implications GRB~220706A has for ultra-long GRB progenitor models and possible powering mechanisms for the extremely late central engine activity.
Source: arXiv (Cornell University)
Authors: Gompertz, Benjamin P., Habeeb, Nusrin, Pasham, Dheeraj R., Postigo, Antonio de Ugarte, Malesani, Daniele B., Evans, Phil A., Page, Kim L., Rayson, Ben, Fernandez, J. Feliciano Agui, Bremer, Michael, Levan, Andrew J., Schroeder, Genevieve, Tanvir, Nial R., Thone, Christina C., Burns, Eric, D'Elia, Valerio, De Pasquale, Massimiliano, Dimple, Hartmann, Dieter, Jakobsson, Pall, Klose, Sylvio, Martin-Carrillo, Antonio, Nicholl, Matt, Guelbenzu, Ana M. Nicuesa, O'Neill, David, Pugliese, Giovanna, Rau, Arne, Rossi, Andrea, Sollerman, Jesper, Starling, Rhaana, Watson, Darach, Worssam, Isabelle, Wortley, Makenzie E.
Institutions: University of Birmingham, University of Leicester, Eureka Scientific, University of Copenhagen, Institut de Radioastronomie Millimétrique, Radboud University Nijmegen, University of Warwick, University of Toronto, Evgeni Kharadze Georgian National Astrophysical Observatory, Louisiana State University, Agenzia Spaziale Italiana, University of Messina, Clemson University, University of Iceland, Thüringer Landessternwarte Tautenburg, University College Dublin, Queen's University Belfast, University of Amsterdam, Max Planck Institute for Extraterrestrial Physics, Osservatorio di Astrofisica e Scienza dello Spazio, National Institute for Astrophysics, Stockholm University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Aarhus Universitet, Leverhulme Trust, University of Leicester, European Commission, National Research Foundation, Danmarks Grundforskningsfond, Centre National d’Etudes Spatiales, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Universitetet i Oslo, Háskóli Íslands, Turun Yliopisto, Stockholms Universitet, Instituto de Astrofísica de Canarias, Science and Technology Facilities Council, Institut National de Physique Nucléaire et de Physique des Particules
OpenAlex ID: W7214033243