The Berkeley Sample of Stripped-Envelope Supernovae

TL;DR

This paper provides a comprehensive spectral dataset of 302 stripped-envelope supernovae, analyzes subtype differences, and confirms key spectral line distinctions among supernova types over three decades.

Contribution

It presents the largest spectral sample of stripped-envelope supernovae, reevaluates classifications, and compares spectral features across subtypes with new observations of rare subclasses.

Findings

O I 7774 absorption is stronger and at higher velocity in Type Ic SNe within 30 days post-peak.

Nebular emission line widths are consistent across supernova subtypes.

The dataset includes 888 spectra of 302 SNe, with 652 spectra published for the first time.

Abstract

We present the complete sample of stripped-envelope supernova (SN) spectra observed by the Lick Observatory Supernova Search (LOSS) collaboration over the last three decades: 888 spectra of 302 SNe, 652 published here for the first time, with 384 spectra (of 92 SNe) having photometrically-determined phases. After correcting for redshift and Milky Way dust reddening and reevaluating the spectroscopic classifications for each SN, we construct mean spectra of the three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We compare measures of line strengths and widths made from this sample to the results of previous efforts, confirming that O I {\lambda}7774 absorption is stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb SNe in the first 30 days after peak brightness, though the widths of nebular emission lines are consistent across subtypes. We also highlight newly available observations for a few rare subpopulations of interest.