The Type Icn SN 2021csp: Implications for the Origins of the Fastest Supernovae and the Fates of Wolf–Rayet Stars

• Published in: The Astrophysical journal Vol. 927; no. 2; pp. 180 - 202
• Main Authors: Perley, Daniel A., Sollerman, Jesper, Schulze, Steve, Yao, Yuhan, Fremling, Christoffer, Gal-Yam, Avishay, Ho, Anna Y. Q., Yang, Yi, Kool, Erik C., Irani, Ido, Yan, Lin, Andreoni, Igor, Baade, Dietrich, Bellm, Eric C., Brink, Thomas G., Chen, Ting-Wan, Cikota, Aleksandar, Coughlin, Michael W., Dahiwale, Aishwarya, Dekany, Richard, Duev, Dmitry A., Filippenko, Alexei V., Hoeflich, Peter, Kasliwal, Mansi M., Kulkarni, S. R., Lunnan, Ragnhild, Masci, Frank J., Maund, Justyn R., Medford, Michael S., Riddle, Reed, Rosnet, Philippe, Shupe, David L., Strotjohann, Nora Linn, Tzanidakis, Anastasios, Zheng, WeiKang
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.03.2022; IOP Publishing
• Subjects: Astrophysics; Black holes; Core-collapse supernovae; Ejecta; Explosions; Nuclear fusion; Stars; Stellar evolution; Stellar mass black holes; Strong interactions (field theory); Supernova; Supernovae; Transient sources; Transients (astronomy); Wolf–Rayet stars
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/ac478e

We present observations of SN 2021csp, the second example of a newly identified type of supernova (SN) hallmarked by strong, narrow, P Cygni carbon features at early times (Type Icn). The SN appears as a fast and luminous blue transient at early times, reaching a peak absolute magnitude of −20 within 3 days due to strong interaction between fast SN ejecta ( v ≈ 30,000 km s −1 ) and a massive, dense, fast-moving C/O wind shed by the WC-like progenitor months before explosion. The narrow-line features disappear from the spectrum 10–20 days after explosion and are replaced by a blue continuum dominated by broad Fe features, reminiscent of Type Ibn and IIn supernovae and indicative of weaker interaction with more extended H/He-poor material. The transient then abruptly fades ∼60 days post-explosion when interaction ceases. Deep limits at later phases suggest minimal heavy-element nucleosynthesis, a low ejecta mass, or both, and imply an origin distinct from that of classical Type Ic SNe. We place SN 2021csp in context with other fast-evolving interacting transients, and discuss various progenitor scenarios: an ultrastripped progenitor star, a pulsational pair-instability eruption, or a jet-driven fallback SN from a Wolf–Rayet (W-R) star. The fallback scenario would naturally explain the similarity between these events and radio-loud fast transients, and suggests a picture in which most stars massive enough to undergo a W-R phase collapse directly to black holes at the end of their lives.