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Seven Years of SN 2014C: A Multiwavelength Synthesis of an Extraordinary Supernova
Abstract 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 more »
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Award ID(s):
Publication Date:
NSF-PAR ID:
10347651
Journal Name:
The Astrophysical Journal
Volume:
930
Issue:
1
Page Range or eLocation-ID:
57
ISSN:
0004-637X
3. ABSTRACT We present X-ray and radio observations of what may be the closest Type Iax supernova (SN) to date, SN 2014dt (d = 12.3–19.3 Mpc), and provide tight constraints on the radio and X-ray emission. We infer a specific radio luminosity $L_R\lt (1.0\!-\!2.4)\times 10^{25}\, \rm {erg\, s^{-1}\, Hz^{-1}}$ at a frequency of 7.5 GHz and a X-ray luminosity $L_X\lt 1.4\times 10^{38}\, \rm {erg\, s^{-1}}$ (0.3–10 keV) at ∼38–48 d post-explosion. We interpret these limits in the context of Inverse Compton (IC) emission and synchrotron emission from a population of electrons accelerated at the forward shock of the explosion in a power-law distribution $N_e(\gamma _e)\propto \gamma _e^{-p}$ with p = 3. Our analysis constrains the progenitor system mass-loss rate to be $\dot{M}\lt 5.0 \times 10^{-6} \rm {M_{\odot }\, yr^{-1}}$ at distances $r\lesssim 10^{16}\, \rm {cm}$ for an assumed wind velocity $v_w=100\, \rm {km\, s^{-1}}$, and a fraction of post-shock energy into magnetic fields and relativistic electrons of ϵB = 0.01 and ϵe = 0.1, respectively. This result rules out some of the parameter space of symbiotic giant star companions, and it is consistent with the low mass-loss rates expected from He-star companions. Our calculations also show that the improved sensitivity of the next-generation Very Largemore »