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Abstract SN 2014C was originally classified as a Type Ib supernova, but at phaseϕ= 127 days, post-explosion strong Hαemission 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 spanningϕ= 947–2494 days post-explosion. We address the evolution of the broadened Hαemission line, as well as broad [Oiii] emission and other lines. We also conduct a parallel analysis of all publicly available multiwavelength data. From our spectra, we find a nearly constant HαFWHM velocity width of ∼2000 km s−1that is significantly lower than that of other broadened atomic transitions (∼3000–7000 km s−1) present in our spectra ([Oi]λ6300; [Oiii]λλ4959, 5007; Heiλ7065; [Caii]λλ7291, 7324). The late radio data demand a fast forward shock (∼10,000 km s−1atϕ= 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 Hαemission arises in the boundary layer between the ejecta and torus. We also consider the possible roles of a pulsar and a binary companion.
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This content will become publicly available on February 5, 2026
Late-time Optical and X-Ray Emission Evolution of the Oxygen-rich SN 1996cr
Abstract When the ejecta of a supernova (SN) interact with the progenitor star's circumstellar environment, a strong shock is driven back into the ejecta, causing the material to become bright optically and in X-rays. Most notably, as the shock traverses the H-rich envelope, it begins to interact with metal-rich material. Thus, continued monitoring of bright and nearby SNe provides valuable clues about both the progenitor structure and its pre-SN evolution. Here we present late-time, multiepoch optical and Chandra X-ray spectra of the core-collapse SN, SN 1996cr. Magellan IMACS optical spectra taken in 2017 July and 2021 August show a very different spectrum from that seen in 2006 with broad, double-peaked optical emission lines of oxygen, argon, and sulfur with expansion velocities of ±4500 km s−1. Redshifted emission components are considerably fainter compared to the blueshifted components, presumably due to internal extinction from dust in the SN ejecta. Broad ±2400 km s−1Hαis also seen, which we infer is shocked progenitor pre-SN, mass-loss, H-rich material. Chandra data indicate a slow but steady decline in the overall X-ray luminosity, suggesting that the forward shock has broken through any circumstellar shell or torus, which is inferred from prior deep Chandra ACIS-S/HETG observations. The X-ray properties are consistent with what is expected from a shock breaking out into a lower-density environment. Though originally identified as a Type IIn SN, based upon late-time optical emission-line spectra, we argue that the SN 1996cr progenitor was partially or highly stripped, suggesting a Type IIb/Ib SN.
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- Award ID(s):
- 2206532
- PAR ID:
- 10631562
- Publisher / Repository:
- IOP Publishing for the American Astronomical Society
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 980
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 82
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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