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

TL;DR

SN 2018ijp is a supernova from a stripped-envelope star that exploded within a dense hydrogen-rich shell, showing an initial radioactive decay phase followed by strong ejecta-CSM interaction.

Contribution

This study presents detailed observations and modeling of SN 2018ijp, revealing its unique explosion within a dense H-rich circumstellar medium, which is a rare event among supernovae.

Findings

Initial spectra resemble broad-lined Type Ic supernovae.

Later spectra show strong ejecta-CSM interaction signatures.

Light curve modeling supports a dense circumstellar environment.

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 an 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.