Optical Spectra of 73 Stripped-Envelope Core-Collapse Supernovae

TL;DR

This paper presents the most extensive optical spectral library of 73 stripped-envelope core-collapse supernovae, covering early to late phases, enabling detailed study of their spectral diversity and comparison with gamma-ray burst SNe.

Contribution

It provides a homogeneous, extensive spectral dataset of 73 supernovae types IIb, Ib, Ic, and broad-lined Ic, including first-time spectra for 53 SNe, spanning from early to late phases.

Findings

Most extensive spectral library of stripped-envelope SNe to date

Includes early and late-time spectra, some as early as 30 days before maximum light

Data enables future studies of spectral diversity and SN-GRB connections

Abstract

We present 645 optical spectra of 73 supernovae (SNe) of Types IIb, Ib, Ic, and broad-lined Ic. All of these types are attributed to the core collapse of massive stars, with varying degrees of intact H and He envelopes before explosion. The SNe in our sample have a mean redshift <cz> = 4200 km/s. Most of these spectra were gathered at the Harvard-Smithsonian Center for Astrophysics (CfA) between 2004 and 2009. For 53 SNe, these are the first published spectra. The data coverage range from mere identification (1-3 spectra) for a few SNe to extensive series of observations (10-30 spectra) that trace the spectral evolution for others, with an average of 9 spectra per SN. For 44 SNe of the 73 SNe presented here, we have well-determined dates of maximum light to determine the phase of each spectrum. Our sample constitutes the most extensive spectral library of stripped-envelope SNe to date. We provide very early coverage (as early as 30 days before V-band max) for photospheric spectra, as well as late-time nebular coverage when the innermost regions of the SNe are visible (as late as 2 years after explosion, while for SN1993J, we have data as late as 11.6 years). This data set has homogeneous observations and reductions that allow us to study the spectroscopic diversity of these classes of stripped SNe and to compare these to SNe associated with gamma-ray bursts. We undertake these matters in follow-up papers.