SN 2020acat: an energetic fast rising Type IIb supernova

K. Medler, P. A. Mazzali, J. Teffs, C. Ashall, J. P. Anderson, I. Arcavi, S. Benetti, K. A. Bostroem, J. Burke, Y. Z. Cai, P. Charalampopoulos, N. Elias-Rosa, M. Ergon, L. Galbany, M. Gromadzki, D. Hiramatsu, D. A. Howell, C. Inserra, P. Lundqvist, C. McCullyT. Müller -Bravo, M. Newsome, M. Nicholl, E. Padilla Gonzalez, E. Paraskeva, A. Pastorello, C. Pellegrino, P. J. Pessi, A. Reguitti, T. M. Reynolds, R. Roy, G. Terreran, L. Tomasella, D. R. Young

Research output: Contribution to journalArticlepeer-review


The ultraviolet (UV) and near-infrared (NIR) photometric and optical spectroscopic observations of SN 2020acat covering ∼250 d after explosion are presented here. Using the fast rising photometric observations, spanning from the UV to NIR wavelengths, a pseudo-bolometric light curve was constructed and compared to several other well-observed Type IIb supernovae (SNe IIb). SN 2020acat displayed a very short rise time reaching a peak luminosity of Log10(L) = 42.49 ± 0.17 erg s-1 in only ∼14.6 ± 0.3 d. From modelling of the pseudo-bolometric light curve, we estimated a total mass of 56Ni synthesized by SN 2020acat of MNi = 0.13 ± 0.03 M⊙, with an ejecta mass of Mej = 2.3 ± 0.4 M⊙ and a kinetic energy of Ek = 1.2 ± 0.3 × 1051 erg. The optical spectra of SN 2020acat display hydrogen signatures well into the transitional period (≳ 100 d), between the photospheric and the nebular phases. The spectra also display a strong feature around 4900 Å that cannot be solely accounted for by the presence of the Fe ii 5018 line. We suggest that the Fe ii feature was augmented by He i 5016 and possibly by the presence of N ii 5005. From both photometric and spectroscopic analysis, we inferred that the progenitor of SN 2020acat was an intermediate-mass compact star with an MZAMS of 15-20 M⊙.

Original languageEnglish
Pages (from-to)5540-5558
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 1 Jul 2022


  • supernovae: general
  • supernovae: individual: SN 2020acat


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