Abstract
We present the discovery of the radio afterglow of the short gamma-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of z ∼ 2.4. While radio observations commenced ≲1 day after the burst, no radio emission was detected until ∼11 days. The radio afterglow subsequently brightened by a factor of ∼3 in the span of a week, followed by a rapid decay (a “radio flare”). We find that a forward shock afterglow model cannot self-consistently describe the multiwavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of ≈5. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of ≈4, or a reverse shock from a shell collision are viable solutions to match the broadband behavior. At z ∼ 2.4, GRB 210726A is among the highest-redshift short GRBs discovered to date, as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by ≲10 days after the burst, potentially missing these late-rising, luminous radio afterglows.
Original language | English (US) |
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Article number | 139 |
Journal | Astrophysical Journal |
Volume | 970 |
Issue number | 2 |
DOIs | |
State | Published - Aug 1 2024 |
Funding
This research was supported in part through the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. W. M. Keck Observatory and MMT Observatory access was supported by Northwestern University and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Based on observations obtained at the international Gemini Observatory (Program IDs GS-2021A-Q-112, GS-2023A-FT-101), a program of NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigaci\u00F3n y Desarrollo (Chile), Ministerio de Ciencia, Tecnolog\u00EDa e Innovaci\u00F3n (Argentina), Minist\u00E9rio da Ci\u00EAncia, Tecnologia, Inova\u00E7\u00F5es e Comunica\u00E7\u00F5es (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). G.S. acknowledges support for this work was provided by the NSF through a Student Observing Support award from the NRAO. The Fong Group at Northwestern acknowledges the support of the National Science Foundation under grant No. AST-1909358 and CAREER grant No. AST2047919. Support for this work was in part provided by the National Aeronautics and Space Administration through Chandra Award Numbers #DD1-22131X and #GO1-22043X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. W.F. gratefully acknowledges the support of the David and Lucile Packard Foundation, the Alfred P. Sloan Foundation, and the Research Corporation for Science Advancement through Cottrell Scholar Award #28284. C.D.K. acknowledges partial support from a CIERA postdoctoral fellowship. A.R.E. is supported by the European Space Agency (ESA) Research Fellowship. E.B. acknowledges support from NSF and NASA grants. This study was enabled by a Radboud Excellence fellowship from Radboud University in Nijmegen, Netherlands. D.B.M. is supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 725246). The Cosmic Dawn Center is supported by the Danish National Research Foundation. N.R.T. acknowledges support from STFC grant ST/W000857/1. I.H. acknowledges support of the Science and Technology Facilities Council (STFC) grants [ST/S000488/1] and [ST/W000903/1]. I.H. acknowledges support from a UKRI Frontiers Research Grant [EP/X026639/1], which was selected by the European Research Council. I.H. acknowledges support from the South African Radio Astronomy Observatory which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Innovation. I.H. acknowledges support from Breakthrough Listen. Breakthrough Listen is managed by the Breakthrough Initiatives, sponsored by the Breakthrough Prize Foundation. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. VLA observations for this study were obtained via projects VLA/20B-057 and VLA/21B-198. This work is partly based on observations collected at the European Southern Observatory under ESO programme 110.24CF.003. We also acknowledge the staff who operate and run the AMI-LA telescope at Lord's Bridge, Cambridge, for the AMI-LA radio data. AMI is supported by the Universities of Cambridge and Oxford, and acknowledges support from the European Research Council under grant No. ERC-2012-StG-307215 LODESTONE. e-MERLIN, and formerly MERLIN, is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of the STFC. We acknowledge the Jodrell Bank Centre for Astrophysics, which is funded by the STFC. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science