Discovery of a dusty yellow supergiant progenitor for the Type IIb SN 2017gkk

TL;DR

This paper reports the discovery of a yellow supergiant progenitor for the Type IIb supernova 2017gkk, supporting the binary interaction model for such supernovae and providing new insights into their progenitor characteristics.

Contribution

The study presents the first direct identification of a yellow supergiant progenitor for a Type IIb supernova, highlighting the role of binary systems in progenitor evolution.

Findings

Progenitor is likely a yellow supergiant with significant circumstellar extinction.

Progenitor has an initial mass of about 16 solar masses.

Supports binary interaction as a key channel for Type IIb supernova progenitors.

Abstract

Type IIb supernovae are important subclass of stripped-envelope supernovae (SNe), which show H lines only at early times. Their progenitors are believed to contain a low-mass H envelope before explosion. This work reports the discovery of a progenitor candidate in pre-explosion Hubble Space Telescope images for the Type IIb SN~2017gkk. With detailed analysis of its spectral energy distribution and local environment, we suggest that the progenitor is most likely a yellow supergiant with significant circumstellar extinction and has an initial mass of about 16 $M_\odot$, effective temperature log($T_{\rm eff}/K)=3.72\pm0.08$ and luminosity log($L/L_{\odot})=5.17\pm0.04$. This progenitor is not massive enough to strip envelope through stellar wind, and it supports an interacting binary progenitor channel and adds to the growing list of direct progenitor detections for Type~IIb SNe. Future late-time observations will confirm whether this progenitor candidate has disappeared and reveal the putative binary companion that has survived the explosion.