SN 2018ijp: the explosion of a stripped-envelope star within a dense H-rich shell?^⋆,⋆⋆

¹ Department of Astronomy and the Oskar Klein Centre, Stockholm University, AlbaNova, 106 91 Stockholm, Sweden
e-mail: leonardo.tartaglia@astro.su.se
² INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo, 11, 34143 Trieste, Italy
⁴ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vesilinnantie 5, 20014 Turku, Finland
⁵ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
⁶ Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
⁷ DIRAC Institute, Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, WA 98195, USA
⁸ Cahill Center for Astrophysics, California Institute of Technology, MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USA
⁹ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁰ Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
¹¹ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 234 Herzl St., Rehovot 76100, Israel
¹² The eScience Institute, University of Washington, Seattle, WA 98195, USA
¹³ Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA
¹⁴ Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USA
¹⁵ Université de Lyon, Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, 69622 Villeurbanne, France
¹⁶ IPAC, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
¹⁷ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA

Received: 30 July 2020
Accepted: 14 April 2021

Abstract

In this paper, we discuss the outcomes of the follow-up campaign of SN 2018ijp, discovered as part of the Zwicky Transient Facility survey for optical transients. Its first spectrum shows similarities to broad-lined Type Ic supernovae around maximum light, whereas later spectra display strong signatures of interaction between rapidly expanding ejecta and a dense H-rich circumstellar medium, coinciding with a second peak in the photometric evolution of the transient. This evolution, along with the results of modeling of the first light-curve peak, suggests a scenario where a stripped star exploded within a dense circumstellar medium. The two main phases in the evolution of the transient could be interpreted as a first phase dominated by radioactive decays, and a later interaction-dominated phase where the ejecta collide with a pre-existing shell. We therefore discuss SN 2018jp within the context of a massive star depleted of its outer layers exploding within a dense H-rich circumstellar medium.