Caltech Core-Collapse Project (CCCP) observations of type IIn supernovae: typical properties and implications for their progenitor stars

TL;DR

This study analyzes four Type IIn supernovae observed by CCCP, revealing common spectral features, light curve properties, and progenitor star mass-loss rates, suggesting they originate from LBV-like stars shortly before explosion.

Contribution

First unbiased sample analysis of SNe IIn revealing common spectral and light curve features, and linking progenitors to LBV-like mass loss prior to explosion.

Findings

Narrow P-Cygni hydrogen lines are ubiquitous in SNe IIn.

Typical rise time >20 days and peak magnitude around -18.4 mag.

Progenitor stars exhibit high mass-loss rates (0.026-0.12 M_sun/yr).

Abstract

Type IIn Supernovae (SNe IIn) are rare events, constituting only a few percent of all core-collapse SNe, and the current sample of well observed SNe IIn is small. Here, we study the four SNe IIn observed by the Caltech Core-Collapse Project (CCCP). The CCCP SN sample is unbiased to the extent that object selection was not influenced by target SN properties. Therefore, these events are representative of the observed population of SNe IIn. We find that a narrow P-Cygni profile in the hydrogen Balmer lines appears to be a ubiquitous feature of SNe IIn. Our light curves show a relatively long rise time (>20 days) followed by a slow decline stage (0.01 to 0.15 mag/day), and a typical V-band peak magnitude of M_V=-18.4 +/- 1.0 mag. We measure the progenitor star wind velocities (600 - 1400 km/s) for the SNe in our sample and derive pre-explosion mass loss rates (0.026 - 0.12 solar masses per year). We compile similar data for SNe IIn from the literature, and discuss our results in the context of this larger sample. Our results indicate that typical SNe IIn arise from progenitor stars that undergo LBV-like mass-loss shortly before they explode.