SN 2014C was originally classified as a Type Ib supernova, but at phase ϕ = 127 days, post-explosion strong Hα emission was observed. SN 2014C has since been observed in radio, infrared, optical and X-ray bands. Here we present new optical spectroscopic and photometric data spanning ϕ = 947–2494 days post-explosion. We address the evolution of the broadened Hα emission line, as well as broad [O iii] emission and other lines. We also conduct a parallel analysis of all publicly available multiwavelength data. From our spectra, we find a nearly constant Hα FWHM velocity width of ∼2000 km s−1 that is significantly lower than that of other broadened atomic transitions (∼3000–7000 km s−1) present in our spectra ([O i] λ6300; [O iii] λλ4959, 5007; He i λ7065; [Ca ii] λλ7291, 7324). The late radio data demand a fast forward shock (∼10,000 km s−1 at ϕ = 1700 days) in rarified matter that contrasts with the modest velocity of the Hα. We propose that the infrared flux originates from a toroidal-like structure of hydrogen surrounding the progenitor system, while later emission at other wavelengths (radio, X-ray) likely originates predominantly from the reverse shock in the ejecta and the forward shock in the quasi-spherical progenitor He-wind. We propose that the Hα emission arises in the boundary layer between the ejecta and torus. We also consider the possible roles of a pulsar and a binary companion.
American Astronomical Society
Thomas, B. P., Wheeler, J. C., Dwarkadas, V. V., Stockdale, C., Vinkó, J., Pooley, D. J., Xu, Y., ... & MacQueen, P. (2022). Seven years of SN 2014C: A multiwavelength sythesis of an extraordinary supernova. The Astrophysical Journal, 930(1), 1-25, Article 57. http://doi.org/10.3847/1538-4357/ac5fa6
The Astrophysical Journal
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