Ultraviolet Detection of the Binary Companion to the Type IIb SN 2001ig

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(L-bol/L-circle dot) = 3.92 +/- 0.14. A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M-circle dot and 9 M-circle dot. 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 lambda 4686 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.NASA [NAS 5-26555]; NASA through STScI [GO-14075, AR-14295]; Christopher R. Redlich Fund; TABASGO Foundation; NSF [AST-1211916]; Miller Institute for Basic Research in Science (U.C. Berkeley); Netherlands Research School for Astronomy (NOVA); Marie Sklodowska-Curie Action (H2020 MSCA-IF-2014, project BinCosmos) [661502]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu