Supernova Siblings and their Parent Galaxies in the Zwicky Transient Facility Bright Transient Surve

TL;DR

This paper reports the discovery and analysis of 10 supernova sibling groups in 5 galaxies from the Zwicky Transient Facility Bright Transient Survey, providing insights into progenitor populations and host galaxy properties.

Contribution

It presents the first sizable sample of SN siblings from an unbiased survey, analyzing their locations and progenitor types to improve understanding of supernova origins.

Findings

SN siblings are more often found near galaxy centers and active star-forming regions.

The ratio of core-collapse to thermonuclear SN siblings is lower than previous samples.

The unbiased ZTF survey enables more accurate SN sibling rate estimates.

Abstract

Supernova (SN) siblings -- two or more SNe in the same parent galaxy -- are useful tools for exploring progenitor stellar populations as well as properties of the host galaxies such as distance, star formation rate, dust extinction, and metallicity. Since the average SN rate for a Milky Way-type galaxy is just one per century, a large imaging survey is required to discover an appreciable sample of SN siblings. From the wide-field Zwicky Transient Facility (ZTF) Bright Transient Survey (BTS; which aims for spectroscopic completeness for all transients which peak brighter than $r{<}$18.5 mag) we present 10 SN siblings in 5 parent galaxies. For each of these families we analyze the SN's location within the host and its underlying stellar population, finding agreement with expectations that SNe from more massive progenitors are found nearer to their host core and in regions of more active star formation. We also present an analysis of the relative rates of core collapse and thermonuclear SN siblings, finding a significantly lower ratio than past SN sibling samples due to the unbiased nature of the ZTF.