How much H and He is "hidden" in SNe Ib/c? -- II. Intermediate-mass objects: a 22 M$_{\odot}$ progenitor case study

TL;DR

This study investigates the amount of hidden hydrogen and helium in Type Ib/c supernovae by modeling a 22 solar mass progenitor with varying degrees of envelope stripping and explosion energies, to better understand spectral features.

Contribution

It introduces detailed progenitor stripping models and explores how different explosion energies affect spectral signatures, clarifying the hidden H/He content in supernovae.

Findings

He mass is tightly constrained by spectral lines.

Higher He above CO core delays O I line appearance.

SN Ib-like models match observed spectral evolution.

Abstract

Stripped envelope supernovae are a sub-class of core collapse supernovae showing several stages of H/He shell stripping that determines the class: H-free/He-poor SNe are classified as Type Ic, H-poor/He-rich are Type Ib, and H/He-rich are Type IIb. Stripping H/He with only stellar wind requires significantly higher mass loss rates than observed while binary-involved mass transfer may usually not strip enough to produce H/He free SNe. Type Ib/c SNe are sometimes found to include weak H/He transient lines as a product of a trace amount of H/He left over from stripping processes. The extent and mass of the H/He required to produce these lines is not well known. In this work, a 22 M$_{\odot}$ progenitor model is stripped of the H/He shells in five steps prior to collapse and then exploded at four explosion energies. Requiring both optical and NIR He I lines for helium identification does not allow much He mass to be hidden in SE--SNE. Increasing the mass of He above the CO core delays the visibility of O I 7774 in early spectra. Our SN Ib-like models are capable of reproducing the spectral evolution of a set of observed SNe with reasonable estimated $E_\mathrm{k}$ accuracy. Our SN\,IIb-like models can partially reproduce low energy observed SN IIb, but we find no observed comparison for the SN IIb-like models with high $E_\mathrm{k}$.