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

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-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±0.17ergs−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
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Pages (from-to)5540-5558
Publication statusPublished - 2022


  • Supernovae: general
  • Supernovae: individual: SN 2020acat


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