Journal ArticleSeven Years of SN 2014C: A Multiwavelength Synthesis of an Extraordinary SupernovaThomas, Benjamin P.; Wheeler, J. Craig; Dwarkadas, Vikram V.; Stockdale, Christopher; Vinkó, Jozsef; Pooley, David; Xu, Yerong; Zeimann, Greg; MacQueen, PhillipAbstract SN 2014C was originally classified as a Type Ib supernova, but at phase ϕ = 127 days, post-explosion strong H α 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 H α 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 H α 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 ] λ 6300; [O iii ] λ λ 4959, 5007; He i λ 7065; [Ca ii ] λ λ 7291, 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 H α . 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 H α emission arises in the boundary layer between the ejecta and torus. We also consider the possible roles of a pulsar and a binary companion.2022-05-0110347651The Astrophysical Journal9301570004-637Xhttps://doi.org/10.3847/1538-4357/ac5fa61911061; 1813825; 1814178National Science Foundation