A1 Refereed original research article in a scientific journal
SN 2023taz: Implications for the UV Diversity of Superluminous Supernovae
Authors: Aamer, Aysha; Nicholl, Matt; Angus, Charlotte; Srivastav, Shubham; Cooke, Jeff; Van Bemmel, Natasha; Suhr, Mark; Poidevin, Frédérick; Geier, Stefan; Anderson, Joseph P.; de Boer, Thomas; Chambers, Kenneth C.; Chen, Ting-Wan; Gromadzki, Mariusz; Gutiérrez, Claudia P.; Kankare, Erkki; Könyves-Tóth, Réka; Lin, Chien-Cheng; Lowe, Thomas B.; Magnier, Eugene; Mazzali, Paolo; Medler, Kyle; Minguez, Paloma; Müller-Bravo, Tomás E.; Ben Warwick
Publication year: 2026
Journal: Astrophysical Journal
Article number: 181
Volume: 1001
Issue: 2
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ae5243
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ae5243
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523311223
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
Superluminous supernovae (SLSNe) are some of the brightest explosions in the Universe, representing the extremes of stellar deaths. At the upper end of their distribution is SN 2023taz, in a dwarf galaxy at z = 0.407. This is one of the most luminous SLSNe discovered to date with a peak absolute magnitude of Mg,peak = –22.75 ± 0.03 and a lower limit for energy radiated of E = 2.9 × 1051 erg. Magnetar model fits reveal individual parameter values typical of the SLSN population, but the combination of a low B-field and ejecta mass with a short spin period places SN 2023taz in a unusual region of parameter space, accounting for its extreme luminosity. The optical data around peak are consistent with a temperature of ∼17,000 K but SN 2023taz shows a surprising deficit in the UV compared to other events in this temperature range. We find no indication of dust extinction that could plausibly explain the UV deficit. The lower level of UV flux is reminiscent of the absorption seen in lower-luminosity events like SN 2017dwh, where Fe-group elements are responsible for the effect. However, in the case of SN 2023taz, there is no evidence for a larger amount of Fe-group elements which could contribute to line blanketing. Comparing to SLSNe with well-observed UV spectra, an underlying temperature of 8000–9000 K would match the UV spectral slope, but is not consistent with the optical color temperatures of these events. The most likely explanation is enhanced absorption by intermediate-mass elements, challenging previous findings that SLSNe exhibit similar UV absorption line equivalent widths. This highlights the need for expanded UV spectroscopic coverage of SLSNe, especially at early times, to build a framework for interpreting their diversity and to enable classification at higher redshifts where optical observations will exclusively probe rest-frame UV emission.
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Funding information in the publication:
A.A., M.N., and C.A. are supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 948381) and by UKSA/STFC grant No. ST/Y000692/1.
J.C. and N.V.B. acknowledge funding from the Australian Research Council Discovery Project DP200102102 and the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), CE170100004 and CE230100016.
F.P. acknowledges support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN) under grant No. PID2022-141915NB-C21.
T.-W.C. acknowledges the financial support from the Yushan Fellow Program by the Ministry of Education, Taiwan (MOE-111-YSFMS-0008-001-P1) and the National Science and Technology Council, Taiwan (NSTC grant 114-2112-M-008-021-MY3).
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 Skłodowska-Curie and the Beatriu de Pinós 2021 BP 00168 program, from the Spanish Ministerio de Ciencia e Innovación (MCIN), the Agencia Estatal de Investigación (AEI) 10.13039/501100011033 under the PID2023-151307NB-I00 SNNEXT project, from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016, the program Unidad de Excelencia María de Maeztu CEX2020-001058-M, and from the Departament de Recerca i Universitats de la Generalitat de Catalunya through the 2021-SGR-01270 grant.
R.K.T. acknowledges support by the NKFIH/OTKA FK-134432 grant of the National Research, Development and Innovation (NRDI) Office of Hungary.
T.E.M.B. is funded by Horizon Europe ERC grant No. 101125877.
B.W. is supported by UKRI’s STFC studentship grant funding, project reference ST/X508871/1.
