SN 2017ein and the Possible First Identification of a Type Ic Supernova Progenitor

TL;DR

This study reports the first potential identification of a stellar progenitor for a Type Ic supernova, SN 2017ein, using archival HST images, and analyzes its properties and environment to infer its nature.

Contribution

It presents the first candidate stellar progenitor for a Type Ic supernova, combining archival imaging with early supernova observations to explore progenitor characteristics.

Findings

Progenitor candidate identified in HST images.

SN 2017ein resembles Type Ic SN 2007gr.

Progenitor likely very massive, 47-80 M_sun, or part of a young stellar cluster.

Abstract

We have identified a progenitor candidate in archival Hubble Space Telescope (HST) images for the Type Ic SN 2017ein in NGC 3938, pinpointing the candidate's location via HST Target-of-Opportunity imaging of the SN itself. This would be the first identification of a stellar-like object as a progenitor candidate for any Type Ic supernova to date. We also present observations of SN 2017ein during the first ~49 days since explosion. We find that SN 2017ein most resembles the well-studied Type Ic SN 2007gr. We infer that SN 2017ein experienced a total visual extinction of A_V~1.0--1.9 mag, predominantly because of dust within the host galaxy. Although the distance is not well known, if this object is the progenitor, it was likely of high initial mass, ~47--48 M_sun if a single star, or ~60--80 M_sun if in a binary system. However, we also find that the progenitor candidate could be a very blue and young compact cluster, further implying a very massive (>65 M_sun) progenitor. Furthermore, the actual progenitor might not be associated with the candidate at all and could be far less massive. From the immediate stellar environment, we find possible evidence for three different populations; if the SN progenitor was a member of the youngest population, this would be consistent with an initial mass of ~57 M_sun. After it has faded, the SN should be reobserved at high spatial resolution and sensitivity, to determine whether the candidate is indeed the progenitor.