We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion, with m F275W = 25.39 ±0.10 and m F336W = 25.88 ±0.13 mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main-sequence star with 19,000 < T eff < 22,000 K and log(Lbol L⊙). A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M⊙ and 9 M⊙, respectively, is found to simultaneously resemble, in the Hertzsprung-Russell diagram, both the observed location of this surviving companion, and the primary star evolutionary endpoints for other Type IIb supernovae. This same model exhibits highly variable late-stage mass loss, as expected from the behavior of the radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals a narrow He ii λ4686 emission line, indicative of continuing interaction with a dense circumstellar medium at large radii from the progenitor. We review our findings on SN 2001ig in the context of binary evolution channels for stripped-envelope supernovae. Owing to the uncrowded nature of its environment in the ultraviolet, this study of SN 2001ig represents one of the cleanest detections to date of a surviving binary companion to a Type IIb supernova.
Bibliographical noteCopyright 2018 The American Astronomical Society. First published in the Astrophysical journal, 856(1), 83, 2018, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/aaaf1e. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
- binaries: close
- binaries: general
- stars: evolution
- stars: massive
- supernovae: general
- supernovae: individual (SN 2001ig)