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

In this paper, we discuss the outcomes of the follow-up campaign of SN 2018ijp, discovered by the Zwicky Transient Facility survey for optical transients. SN 2018ijp shows early spectra similar to broad-lined supernovae of Type Ic around maximum light, followed later by strong signatures of interaction between rapidly expanding supernova ejecta and a dense H-rich circumstellar medium, coinciding with a second peak in the photometric evolution of the transient. Modeling the early luminosity of SN 2018ijp results in 0.7 M_⊙ and 0.3 M_⊙ for the total ejected and radioactive ⁵⁶Ni masses, with an explosion energy of 3.3 × 10⁵¹ erg, while the analysis of the light curve at later phases suggests a total mass of ≃0.5 M_⊙ for the H-rich circumstellar medium. Based on these results, obtained using simple analytical models, we discuss the observables of SN 2018jp in the context of the explosion of a massive star depleted of its outer H and He layers within a dense H-rich medium.