SN 2020cpg: an energetic link between Type IIb and Ib supernovae

K. Medler, P. A. Mazzali, J. Teffs, S. J. Prentice, C. Ashall, M. Amenouche, J. P. Anderson, J. Burke, T. W. Chen, L. Galbany, M. Gromadzki, C. P. Gutiérrez, D. Hiramatsu, D. A. Howell, C. Inserra, E. Kankare, C. McCully, T. E. Müller-Bravo, M. Nicholl, C. PellegrinoJ. Sollerman

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Stripped-envelope supernovae (SE-SNe) show a wide variety of photometric and spectroscopic properties. This is due to the different potential formation channels and the stripping mechanism that allows for a large diversity within the progenitors outer envelope compositions. Here, the photometric and spectroscopic observations of SN 2020cpg covering ~130 d from the explosion date are presented. SN 2020cpg (z = 0.037) is a bright SE-SNe with the B-band peaking at MB = -17.75 ± 0.39 mag and a maximum pseudo-bolometric luminosity of Lmax = 6.03 ± 0.01 × 1042 erg s-1. Spectroscopically, SN 2020cpg displays a weak high- and low-velocity H α feature during the photospheric phase of its evolution, suggesting that it contained a detached hydrogen envelope prior to explosion. From comparisons with spectral models, the mass of hydrogen within the outer envelope was constrained to be ~0.1 M. From the pseudo-bolometric light curve of SN 2020cpg a 56Ni mass of MNi ~ 0.27 ± 0.08 M was determined using an Arnett-like model. The ejecta mass and kinetic energy of SN 2020cpg were determined using an alternative method that compares the light curve of SN 2020cpg and several modelled SE-SNe, resulting in an ejecta mass of Mejc ~ 5.5 ± 2.0 M and a kinetic energy of EK ~ 9.0 ± 3.0 × 1051 erg. The ejected mass indicates a progenitor mass of 18-25 M. The use of the comparative light curve method provides an alternative process to the commonly used Arnett-like model to determine the physical properties of SE-SNe....
Original languageEnglish
Pages (from-to)1832–1849
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date22 Jun 2021
Publication statusPublished - Sept 2021


  • general – supernovae
  • individual (SN 2020cpg)
  • supernovae


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