SN~2018erx: A fast-evolving, dust-reddened Type Icn supernova with broad C II emission lines
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| Format: | Preprint |
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2026
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| author | Das, Kaustav K. Gangopadhyay, Anjasha Kasliwal, Mansi M. Sollerman, Jesper Perley, Daniel A. Schulze, Steve Fremling, Christoffer Coughlin, Michael W. De, Kishalay Gal-Yam, Avishay Goobar, Ariel Graham, Matthew Masci, Frank J. Moriya, Takashi J. Purdum, Josiah Rose, Sam Rusholme, Ben Sarin, Nikhil Smith, Roger Tsuna, Daichi |
| author_facet | Das, Kaustav K. Gangopadhyay, Anjasha Kasliwal, Mansi M. Sollerman, Jesper Perley, Daniel A. Schulze, Steve Fremling, Christoffer Coughlin, Michael W. De, Kishalay Gal-Yam, Avishay Goobar, Ariel Graham, Matthew Masci, Frank J. Moriya, Takashi J. Purdum, Josiah Rose, Sam Rusholme, Ben Sarin, Nikhil Smith, Roger Tsuna, Daichi |
| contents | We present the discovery and characterization of SN~2018erx (ZTF18abkmbpy), a fast-evolving, unusually red, interacting stripped-envelope supernova. Spectroscopically, SN~2018erx shows broad \ion{C}{2} emission with characteristic widths of $\sim\!3800$~km~s$^{-1}$, consistent with interaction with carbon-rich circumstellar material and a Type~Icn core-collapse SN classification. Photometrically, it evolves rapidly, rising from half-maximum to peak in 2.1~d and declining back in 3.1~d. Semi-analytical CSM-interaction modeling favors a compact, shell-like CSM with $M_{\rm CSM}\approx0.3\,M_\odot$, $R_0\approx0.7$~AU, and a low ejecta mass of $M_{\rm ej}\approx0.11\,M_\odot$. The radioactive yield is also small, with $M_{\rm Ni}\lesssim(3$--$5)\times10^{-3}\,M_\odot$, placing SN~2018erx at the low end of the H-poor distribution. At +29~d after peak, we detect a near-infrared excess consistent with pre-existing local circumstellar dust, with $M_{\rm d}\sim10^{-6}$--$10^{-5}\,M_\odot$. Together, the rapid evolution, strong local reddening, carbon-rich emission, and dust point to a multi-component circumstellar environment: a dense inner interaction region from enhanced pre-SN mass loss and an outer dusty layer from an earlier mass-loss episode roughly $10$--$200$~yr before core collapse. These properties favor an ultra-stripped core-collapse explosion of a low-mass He star in a binary system, with fallback-modified Wolf--Rayet collapse or merger-driven mass loss remaining possible alternatives. SN~2018erx provides rare insight into the mass-loss history of stripped-envelope SNe and suggests that dust-enshrouded explosions of this kind may be underrepresented in optical surveys. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_24811 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | SN~2018erx: A fast-evolving, dust-reddened Type Icn supernova with broad C II emission lines Das, Kaustav K. Gangopadhyay, Anjasha Kasliwal, Mansi M. Sollerman, Jesper Perley, Daniel A. Schulze, Steve Fremling, Christoffer Coughlin, Michael W. De, Kishalay Gal-Yam, Avishay Goobar, Ariel Graham, Matthew Masci, Frank J. Moriya, Takashi J. Purdum, Josiah Rose, Sam Rusholme, Ben Sarin, Nikhil Smith, Roger Tsuna, Daichi High Energy Astrophysical Phenomena Solar and Stellar Astrophysics We present the discovery and characterization of SN~2018erx (ZTF18abkmbpy), a fast-evolving, unusually red, interacting stripped-envelope supernova. Spectroscopically, SN~2018erx shows broad \ion{C}{2} emission with characteristic widths of $\sim\!3800$~km~s$^{-1}$, consistent with interaction with carbon-rich circumstellar material and a Type~Icn core-collapse SN classification. Photometrically, it evolves rapidly, rising from half-maximum to peak in 2.1~d and declining back in 3.1~d. Semi-analytical CSM-interaction modeling favors a compact, shell-like CSM with $M_{\rm CSM}\approx0.3\,M_\odot$, $R_0\approx0.7$~AU, and a low ejecta mass of $M_{\rm ej}\approx0.11\,M_\odot$. The radioactive yield is also small, with $M_{\rm Ni}\lesssim(3$--$5)\times10^{-3}\,M_\odot$, placing SN~2018erx at the low end of the H-poor distribution. At +29~d after peak, we detect a near-infrared excess consistent with pre-existing local circumstellar dust, with $M_{\rm d}\sim10^{-6}$--$10^{-5}\,M_\odot$. Together, the rapid evolution, strong local reddening, carbon-rich emission, and dust point to a multi-component circumstellar environment: a dense inner interaction region from enhanced pre-SN mass loss and an outer dusty layer from an earlier mass-loss episode roughly $10$--$200$~yr before core collapse. These properties favor an ultra-stripped core-collapse explosion of a low-mass He star in a binary system, with fallback-modified Wolf--Rayet collapse or merger-driven mass loss remaining possible alternatives. SN~2018erx provides rare insight into the mass-loss history of stripped-envelope SNe and suggests that dust-enshrouded explosions of this kind may be underrepresented in optical surveys. |
| title | SN~2018erx: A fast-evolving, dust-reddened Type Icn supernova with broad C II emission lines |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2605.24811 |