We report the first detection of a credible progenitor system for a Type Ic supernova (SN Ic), SN 2017ein. We present spectra and photometry of the SN, finding it to be similar to carbon-rich, low-luminosity SNe Ic. Using a post-explosion Keck adaptive optics image, we precisely determine the position of SN 2017ein in pre-explosion HST images, finding a single source coincident with the SN position. This source is marginally extended, and is consistent with being a stellar cluster. However, under the assumption that the emission of this source is dominated by a single point source, we perform point-spread function photometry, and correcting for line-of-sight reddening, we find it to have MF555W = -7.5 ± 0.2 mag and mF555W - mF814W = -0.67 ± 0.14 mag. This source is bluer than the main sequence and brighter than almost all Wolf-Rayet stars, however, it is similar to some WC+O- and B-star binary systems. Under the assumption that the source is dominated by a single star, we find that it had an initial mass of 55-15+20M⊙. We also examined binary star models to look for systems that match the overall photometry of the pre-explosion source and found that the best-fitting model is an 80+48M⊙ close binary system in which the 80M⊙ star is stripped and explodes as a lower mass star. Late-time photometry after the SN has faded will be necessary to cleanly separate the progenitor star emission from the additional coincident emission.
- Stars: evolution
- Supernovae: general
- Supernovae: individual (SN 2017ein)