SN 2023xgo: Helium-rich Type Icn or Carbon-Flash Type Ibn supernova?

ABSTRACT We present observations of SN 2023xgo, a transitional Type Ibn/Icn SN, from $-5.6$ to 63 d relative to r-band peak. Early spectra show C iii $\lambda$5696 emission like Type Icn SNe, shifting to Type Ibn features. The He i velocities (1800–10 000 km s$^{-1}$) and pseudo-equivalent widths are among the highest in the Ibn/Icn class. The light curve declines at 0.14 mag d$^{-1}$ until 30 d, matching SNe Ibn/Icn but slower than fast transients. SN 2023xgo is the faintest in our SN Ibn sample ($M_r = -17.65 \pm 0.04$) but shows typical colour and host properties. Semi-analytical modelling of the light curve suggests a compact CSM shell ($\sim 10^{12}\text {--}10^{13}$ cm), mass-loss rate between 10−4 and 10−3 M$_{\odot }$ yr$^{-1}$ with CSM and ejecta masses of $\sim$0.22 and 0.12 M$_{\odot }$, respectively. Post-maximum light-curve, spectral modelling favours a $\sim$3 M$_{\odot }$ helium star progenitor with extended ($\sim 10^{15}$ cm), stratified CSM (density exponent of 2.9) and mass-loss rate of $0.1-2.7$ M$_{\odot }$ yr$^{-1}$. These two mass-loss regimes imply a radially varying CSM, shaped by asymmetry or changes in the progenitor’s mass-loss over time. This mass-loss behaviour fits both binary and single-star evolution. Early Icn-like features stem from hot carbon ionization, fading to Ibn-like with cooling. SN 2023xgo thus offers rare insight into the connection between SNe Icn, Ibn, and SNe Ibn with ejecta signatures.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-09-10
DOI
https://doi.org/10.1093/mnras/staf1517
Citations
3
Primary Topic
Gamma-ray bursts and supernovae
Type
article
Field-Weighted Citation Impact
3.46

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article

SN 2023xgo: Helium-rich Type Icn or Carbon-Flash Type Ibn supernova?

Yu-Jing Qin, S. Brennan, D. K. Sahu, Rishabh Singh Teja et al.
3 citations
Monthly Notices of the Royal Astronomical Society
Gamma-ray bursts and supernovae
3.46
article

SN 2023xgo: Helium-rich Type Icn or Carbon-Flash Type Ibn supernova?

Yu-Jing Qin, S. Brennan, D. K. Sahu, Rishabh Singh Teja, P. J. Pessi, Jacob Wise, Raya Dastidar, Claes Fransson, Niharika Sravan, Miho Kawabata, Bhavya Ailawadhi, J. Sollerman, Kenta Taguchi, Kaustav K. Das, R. Lunnan, Josiah Purdum, K-Ryan Hinds, C. Fremling, Russ R. Laher, Mridweeka Singh, Naveen Dukiya, D. A. Perley, Keiichi Maeda, Steve Schulze, Kuntal Misra, Anna Y. Q. Ho, Koji S. Kawabata, B. Rusholme, Anjasha Gangopadhyay, Nikhil Sarin, Avinash Singh, M. M. Kasliwal, Monalisa Dubey, Roger Smith, K. Tsalapatas, Tatsuya Nakaoka, Smaranika Banerjee, Aleksandra Bochenek
article en
3 citations

Abstract

ABSTRACT We present observations of SN 2023xgo, a transitional Type Ibn/Icn SN, from $-5.6$ to 63 d relative to r-band peak. Early spectra show C iii $\lambda$5696 emission like Type Icn SNe, shifting to Type Ibn features. The He i velocities (1800–10 000 km s$^{-1}$) and pseudo-equivalent widths are among the highest in the Ibn/Icn class. The light curve declines at 0.14 mag d$^{-1}$ until 30 d, matching SNe Ibn/Icn but slower than fast transients. SN 2023xgo is the faintest in our SN Ibn sample ($M_r = -17.65 \pm 0.04$) but shows typical colour and host properties. Semi-analytical modelling of the light curve suggests a compact CSM shell ($\sim 10^{12}\text {--}10^{13}$ cm), mass-loss rate between 10−4 and 10−3 M$_{\odot }$ yr$^{-1}$ with CSM and ejecta masses of $\sim$0.22 and 0.12 M$_{\odot }$, respectively. Post-maximum light-curve, spectral modelling favours a $\sim$3 M$_{\odot }$ helium star progenitor with extended ($\sim 10^{15}$ cm), stratified CSM (density exponent of 2.9) and mass-loss rate of $0.1-2.7$ M$_{\odot }$ yr$^{-1}$. These two mass-loss regimes imply a radially varying CSM, shaped by asymmetry or changes in the progenitor’s mass-loss over time. This mass-loss behaviour fits both binary and single-star evolution. Early Icn-like features stem from hot carbon ionization, fading to Ibn-like with cooling. SN 2023xgo thus offers rare insight into the connection between SNe Icn, Ibn, and SNe Ibn with ejecta signatures.

Monthly Notices of the Royal Astronomical SocietyVol. 547(3)
Northwestern University (US), Hiroshima University (JP), California Institute of Technology (US), Universidad Andrés Bello (CL), M.J.P. Rohilkhand University (IN), Indian Institute of Astrophysics (IN), Stockholm University (SE), Cornell University (US), Kyoto University (JP), Aryabhatta Research Institute of Observational Sciences (IN), Clínica Las Condes (CL), Millennium Institute of Astrophysics (CL), AlbaNova (SE), Infrared Processing and Analysis Center (US), Liverpool John Moores University (GB), Drexel University (US)
National Science Foundation, Gordon and Betty Moore Foundation, California Institute of Technology, Northwestern University, Drexel University, University of Warwick, Stockholms Universitet, Agencia Nacional de Investigación y Desarrollo, Japan Society for the Promotion of Science
Openalex Percentile: Top 7%
Gamma-ray bursts and supernovae
3.46
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