Supernova 2020wnt: An Atypical Superluminous Supernova with a Hidden Central Engine

Tinyanont, S ORCID: 0000-0002-1481-4676, Woosley, SE ORCID: 0000-0002-3352-7437, Taggart, K ORCID: 0000-0002-5748-4558, Foley, RJ ORCID: 0000-0002-2445-5275, Yan, L ORCID: 0000-0003-1710-9339, Lunnan, R ORCID: 0000-0001-9454-4639, Davis, KW ORCID: 0000-0002-5680-4660, Kilpatrick, CD ORCID: 0000-0002-5740-7747, Siebert, MR ORCID: 0000-0003-2445-3891, Schulze, S ORCID: 0000-0001-6797-1889, Ashall, C ORCID: 0000-0002-5221-7557, Chen, TW ORCID: 0000-0002-1066-6098, De, K ORCID: 0000-0002-8989-0542, Dimitriadis, G ORCID: 0000-0001-9494-179X, Dong, DZ ORCID: 0000-0001-9584-2531, Fremling, C ORCID: 0000-0002-4223-103X, Gagliano, A ORCID: 0000-0003-4906-8447, Jha, SW ORCID: 0000-0001-8738-6011, Jones, DO ORCID: 0000-0002-6230-0151, Kasliwal, MM ORCID: 0000-0002-5619-4938 et al (2023) Supernova 2020wnt: An Atypical Superluminous Supernova with a Hidden Central Engine. The Astrophysical Journal, 951 (1). pp. 1-26. ISSN 1538-4357

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Abstract

We present observations of a peculiar hydrogen- and helium-poor stripped-envelope (SE) supernova (SN) 2020wnt, primarily in the optical and near-infrared (near-IR). Its peak absolute bolometric magnitude of −20.9 mag (L bol, peak = (6.8 ± 0.3) × 1043 erg s−1) and a rise time of 69 days are reminiscent of hydrogen-poor superluminous SNe (SLSNe I), luminous transients potentially powered by spinning-down magnetars. Before the main peak, there is a brief peak lasting <10 days post explosion, likely caused by interaction with circumstellar medium (CSM) ejected ∼years before the SN explosion. The optical spectra near peak lack a hot continuum and O ii absorptions, which are signs of heating from a central engine; they quantitatively resemble those of radioactivity-powered hydrogen/helium-poor Type Ic SESNe. At ∼1 yr after peak, nebular spectra reveal a blue pseudo-continuum and narrow O i recombination lines associated with magnetar heating. Radio observations rule out strong CSM interactions as the dominant energy source at +266 days post peak. Near-IR observations at +200-300 days reveal carbon monoxide and dust formation, which causes a dramatic optical light-curve dip. Pair-instability explosion models predict slow light curve and spectral features incompatible with observations. SN 2020wnt is best explained as a magnetar-powered core-collapse explosion of a 28 M ⊙ pre-SN star. The explosion kinetic energy is significantly larger than the magnetar energy at peak, effectively concealing the magnetar-heated inner ejecta until well after peak. SN 2020wnt falls into a continuum between normal SNe Ic and SLSNe I, and demonstrates that optical spectra at peak alone cannot rule out the presence of a central engine.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date of acceptance:	17 March 2023
Date of first compliant Open Access:	4 January 2024
Date Deposited:	04 Jan 2024 12:26
Last Modified:	04 Jul 2025 15:00
DOI or ID number:	10.3847/1538-4357/acc6c3
URI:	https://researchonline.ljmu.ac.uk/id/eprint/22173

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