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Published January 10, 2024 | Published
Journal Article Open

Characterizing the Ordinary Broad-line Type Ic SN 2023pel from the Energetic GRB 230812B


We report observations of the optical counterpart of the long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity (z = 0.36) and high energy (Eγ,iso ∼ 1053 erg) make it an important event to study as a probe of the connection between massive star core collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peak r-band magnitude of Mr = −19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN of MNi = 0.38 ± 0.01 M and a peak bolometric luminosity of Lbol ∼ 1.3 × 1043 erg s−1. We confirm SN 2023pel's classification as a broad-line Type Ic SN with a spectrum taken 15.5 days after its peak in the r band and derive a photospheric expansion velocity of vph = 11,300 ± 1600 km s−1 at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta mass Mej = 1.0 ± 0.6 M and kinetic energy E_(KE) = 1.3−₋₁₂^(+3.3) × 10⁵¹ erg. We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness and Eγ,iso for their associated GRBs across a broad range of 7 orders of magnitude provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems.

Copyright and License

© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.


G.P.S. dedicates this paper to Keagan Jaravata and to the Alvir and Jaravata families. SN 2023pel will always be connected to the memory of Keagan's life.

G.P.S. thanks Isiah Holt for useful discussions on MCMC techniques and Simi Bhullar for her moral support throughout the paper-writing process. The material is based upon work supported by NASA under award No. 80GSFC21M0002. B.O. acknowledges useful discussions with Noel Klingler regarding UVOT data analysis and the impact of the ongoing attitude control issues. B.O. gratefully acknowledges support from the McWilliams Postdoctoral Fellowship at Carnegie Mellon University. M.C.M. was supported in part by NASA ADAP grants 80NSSC21K0649 and 80NSSC20K0288. G.C.A. thanks the Indian National Science Academy for support under the INSA Senior Scientist program. M.W.C. acknowledges support from the National Science Foundation with grant No. PHY-2010970 and OAC-2117997. S.Y. is supported by the National Natural Science Foundation of China under grant No. 12303046.

These results made use of Lowell Observatory's Lowell Discovery Telescope (LDT), formerly the Discovery Channel Telescope. Lowell operates the LDT in partnership with Boston University, Northern Arizona University, the University of Maryland, and the University of Toledo. Partial support of the LDT was provided by Discovery Communications. LMI was built by Lowell Observatory using funds from the National Science Foundation (AST-1005313). The GROWTH-India Telescope (GIT) is a 70 cm telescope with a 07 field of view set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from the Indo-US Science and Technology Forum and the Science and Engineering Research Board, Department of Science and Technology (DST), Government of India. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA, an autonomous institute under DST. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. The 2 m Himalayan Chandra Telescope (HCT) is located at the Indian Optical Observatory (IAO) at Hanle. We thank the staff of IAO, Hanle, and CREST, Hosakote, that made these observations possible. HCT observations were carried out under the ToO program of proposal No. HCT-2023-C2-P15. The facilities at IAO and CREST are operated by the Indian Institute of Astrophysics, Bangalore. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council.

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. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. Based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, the University of Warwick, Ruhr University Bochum, and Northwestern University. Operations are conducted by COO, IPAC, and UW. The ZTF forced-photometry service was funded under Heising–Simons Foundation grant No. 12540303 (PI: Graham). The Gordon and Betty Moore Foundation, through both the Data-Driven Investigator Program and a dedicated grant, provided critical funding for SkyPortal.


PO:1.2m - , PO:1.5m - , Liverpool:2m - , LDT - , HCT - , Keck:II -

Software References

PyMultinestWOMBATSESNSpectraPCASESNSpectraLibPypeitSNCosmoPySpecKitXSPEC v12.12.0emceeSCAMPSwarpZOGYSExtractorAstro-SCRAPPYsolve-fieldHEASoft v6.29cFpipe


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Additional details

February 2, 2024
February 2, 2024