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A massive, energetic model for the luminous transitional Type Ib/IIb SN 2020cpg

Teffs, J, Mazzali, PA, Medler, K and Hachinger, S (2022) A massive, energetic model for the luminous transitional Type Ib/IIb SN 2020cpg. Monthly Notices of the Royal Astronomical Society, 517 (4). pp. 5678-5686. ISSN 0035-8711

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Abstract

Using a combined spectral and light-curve modelling approach, we fit a massive and energetic explosion model to the luminous Type Ib/IIb SN 2020cpg. This model has an ejected mass of ∼(7 ± 2) M⊙ with a final explosion energy of ∼(6 ± 1) × 1051 erg with MNi = 0.27 ± 0.05 M⊙. The early spectra are hot and blue with weak He I lines, and a complicated Hα region suggested to be a multicomponent feature. Modelling the spectra required ∼0.08 M⊙ of H at velocities >11 000 km s−1 and a total He mass of ∼1.0 M⊙ at velocities >9500 km s−1 above CO-rich ejecta. This model has a ratio of kinetic energy and ejected mass of 0.85+0.5−0.3 foe M⊙−1. The high luminosity and explosion energy results in a broadened Hα line that is blended with Si II, C II, and He I, which led to the initial classification of SN 2020cpg as a Type Ib. We instead classify SN 2020cpg as a bright transitional event between the Type Ib and Type IIb classes. Comparing our model parameters to stellar evolution models, a progenitor mass of 25–30 M⊙, i.e. stripped of most of the hydrogen shell and of some of the helium shell prior to collapse produces a He core of comparable mass. The excess 56Ni production in SN 2020cpg as compared to objects of similar ejected mass may suggest evidence of additional energy sources such as a failed GRB or weak magnetar energy injection, or a smaller remnant mass.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Royal Astronomical Society
SWORD Depositor: A Symplectic
Date Deposited: 15 Nov 2022 08:57
Last Modified: 15 Nov 2022 09:00
DOI or Identification number: 10.1093/mnras/stac3077
URI: https://researchonline.ljmu.ac.uk/id/eprint/18120

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