Letter to the Editor

JWST reveals a supernova following a gamma-ray burst at z ≃ 7.3

¹ Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010 Nijmegen 6500 GL, The Netherlands
² Department of Physics, University of Warwick, Coventry CV4 7AL, UK
³ Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
⁴ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁵ Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen N, Denmark
⁶ The Cosmic Dawn Centre (DAWN), Denmark
⁷ School of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁸ School of Physics and Centre for Space Research, University College Dublin, Belfield Dublin 4, Ireland
⁹ Osservatorio di Astrofisica e Scienza dello Spazio, INAF, Via Piero Gobetti 93/3, Bologna 40129, Italy
¹⁰ LUX, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Meudon 92190, France
¹¹ Institut d’Astrophysique de Paris, CNRS, UMR 7095, 98 bis bd Arago, F-75014 Paris, France
¹² INAF–Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, (LC), Italy
¹³ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
¹⁴ IRAP, Université de Toulouse, CNRS, CNES, Toulouse, France
¹⁵ Instituto de Alta Investigacion, Universidad de Tarapaca, Casilla 7D, Arica, Chile
¹⁶ European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁷ CEA Paris-Saclay, Irfu/Département d’Astrophysique, 91190 Gif sur Yvette, France
¹⁸ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, F-75014 Paris, France
¹⁹ Space Science Data Center (SSDC) – Agenzia Spaziale Italiana (ASI), Via del Politecnico snc, I-00133 Roma, Italy
²⁰ MIFT Department, University of Messina, Via F. S. D’Alcontres 31, Messina, Italy
²¹ Department of Physics and Astronomy, Baylor University, One Bear Place #97316, Waco, TX 76798, USA
²² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD21218, USA
²³ School of Physics and Astronomy and Institute for Gravitational Wave Astronomy, University of Birmingham, Birmingham B15 2TT, UK
²⁴ Clemson University, Department of Physics & Astronony, Clemson, SC 29634, USA
²⁵ INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80121 Naples, Italy
²⁶ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, 2200 Copenhagen, Denmark
²⁷ Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavik, Iceland
²⁸ Department of Physics & Astronomy, University of Utah, Salt Lake City UT 84112, USA
²⁹ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, (RM), Italy
³⁰ INAF – Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, I-00133 Rome, Italy
³¹ Anton Pannekoek Institute of Astronomy, University of Amsterdam, P.O. Box 94249 1090 GE Amsterdam, The Netherlands
³² INAF–Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
³³ E. Kharadze Georgian National Astrophysical Observatory, Mt. Kanobili, Abastumani, 0301 Adigeni, Georgia
³⁴ Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
³⁵ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China

^⋆ Corresponding author: a.levan@astro.ru.nl

Received: 24 July 2025
Accepted: 3 October 2025

Abstract

The majority of long-duration gamma-ray bursts (GRBs) are thought to arise from the collapse of massive stars, making them powerful tracers of star formation across cosmic time. Evidence for this origin comes from the presence of supernovae (SNe) in the aftermath of the GRB event, whose properties in turn link back to those of the collapsing star. In principle, thanks to GRBs, we can study the properties of individual stars in the distant Universe. Here, we present JWST/NIRCAM observations that have been able to detect both the host galaxy and a likely SN in the Space-based multi-band astronomical Variable Objects Monitor (SVOM) detected GRB 250314A. GRB 250314A has a spectroscopically measured redshift of z ≃ 7.3, placing it deep in the era of reionisation. The data are well described by a combination of faint blue host, similar to many z ∼ 7 galaxies, with a SN of similar luminosity to the prototype GRB SN, namely, SN 1998bw. The SN may be somewhat fainter if a larger contribution from the underlying galaxy is present, but SNe brighter than SN 1998bw can be excluded, given the evidence of low dust extinction, based on the blue afterglow colours. These observations suggest that despite disparate physical conditions, the star that created GRB 250314A was not much more massive and it might even resemble the GRB progenitors of the Local Universe.