SN 2023gpw: Exploring the diversity and power sources of hydrogen-rich superluminous supernovae
: Kangas, T.; Charalampopoulos, P.; Nagao, T.; Yan, L.; Stritzinger, M.; Schulze, S.; Das, K.; Elias-Rosa, N.; Fremling, C.; Perley, D.; Sollerman, J.; Muller-Bravo, T. E.; Galbany, L.; Groom, S. L.; Gutierrez, C. P.; Kasliwal, M. M.; Kotak, R.; Laher, R. R.; Lundqvist, P.; Mattila, S.; Smith, R.
Publisher: EDP Sciences
: 2026
Astronomy and Astrophysics
: A52
: 705
: 0004-6361
: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202555588
: https://doi.org/10.1051/0004-6361/202555588
: https://research.utu.fi/converis/portal/detail/Publication/509017747
We present our observations and analysis of SN 2023gpw, a hydrogen-rich superluminous supernova (SLSN II) with broad emission lines in its post-peak spectra. Unlike previously observed SLSNe II, its light curve suggests an abrupt drop during a solar conjunction between similar to 80 and similar to 180 d after the light curve peak, which is possibly analogous to a normal hydrogen-rich supernova (SN). Spectra taken at and before the peak show hydrogen and helium "flash" emission lines attributed to early interaction with a dense confined circumstellar medium (CSM). A well-observed ultraviolet excess appears as these lines disappear, also as a result of CSM interaction. The blackbody photosphere expands roughly at the same velocity throughout the observations, indicating little or no bulk deceleration. This velocity is much higher than what is seen in spectral lines, suggesting asymmetry in the ejecta. The high total radiated energy (greater than or similar to 9 x 10(50) erg) and aforementioned lack of bulk deceleration in SN 2023gpw are difficult to reconcile with a neutrino-driven SN simply combined with efficient conversion from kinetic energy to emission through interaction. This suggests an additional energy source, such as a central engine. While magnetar-powered models qualitatively similar to SN 2023gpw exist, more modeling work is required to determine if they can reproduce the observed properties in combination with early interaction. The required energy might alternatively be provided by accretion onto a black hole created in the collapse of a massive progenitor star.
:
We thank the anonymous referee for useful comments, and Georgios Dimitriadis for re-reducing the INT spectrum. T.K. acknowledges support from the Research Council of Finland project 360274. R.K. and T.L.K. acknowledge support from the Research Council of Finland (340613). M.S. is funded by the Independent Research Fund Denmark (IRFD) via Project 2 grant 10.46540/2032-00022B and by the Aarhus University Nova grant# AUFF-E-2023-9-28. N.E.R. acknowledges support from the PRIN-INAF 2022, 'Shedding light on the nature of gap transients: from the observations to the models' and from the Spanish Ministerio de Ciencia e Innovacion (MCIN) and the Agencia Estatal de Investigacion (AEI) 10.13039/501100011033 under the program Unidad de Excelencia Maria de Maeztu CEX2020-001058-M. C.P.G. acknowledges financial support from the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 Research and Innovation Programme of the European Union under the Marie Sk & lstrok;odowska-Curie and the Beatriu de Pinos 2021 BP 00168 programme, from the Spanish Ministerio de Ciencia e Innovacion (MCIN) and the Agencia Estatal de Investigacion (AEI) 10.13039/501100011033 under the PID2023-151307NB-I00 SNNEXT project, from Centro Superior de Investigaciones Cientificas (CSIC) under the PIE project 20215AT016 and the program Unidad de Excelencia Maria de Maeztu CEX2020-001058-M, and from the Departament de Recerca i Universitats de la Generalitat de Catalunya through the 2021-SGR-01270 grant. T.L.K. acknowledges a Warwick Astrophysics prize post-doctoral fellowship made possible thanks to a generous philanthropic donation. T.E.M.B. is funded by Horizon Europe ERC grant no. 101125877. The Starlink software (Currie et al. 2014) is currently supported by the East Asian Observatory. This study is based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. Access to the Las Cumbres Observatory was made possible via an allocation by OPTICON (program 22A/012, PI Stritzinger). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 101004719. 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, University of Warwick, Ruhr University Bochum, Cornell University, and Northwestern University. Operations are conducted by COO, IPAC, and UW.
