April
2026
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2026MNRAS.547f1517G
Authors
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Gangopadhyay, Anjasha
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Sollerman, Jesper
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Tsalapatas, Konstantinos
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Maeda, Keiichi
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Dukiya, Naveen
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Schulze, Steve
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Fransson, Claes
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Sarin, Nikhil
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Pessi, Priscila J.
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Singh, Mridweeka
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Wise, Jacob
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Nakaoka, Tatsuya
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Singh, Avinash
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Dastidar, Raya
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Kawabata, Miho
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Qin, Yu-Jing
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Das, Kaustav K.
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Perley, Daniel
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Fremling, Christoffer
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Taguchi, Kenta
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Hinds, K.-Ryan
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Lunnan, Ragnhild
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Teja, Rishabh Singh
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Dubey, Monalisa
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Ailawadhi, Bhavya
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Banerjee, Smaranika
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Kawabata, Koji S.
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Misra, Kuntal
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Sahu, Devendra K.
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Brennan, Sea'n. J.
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Kasliwal, Mansi M.
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Ho, Anna Y. C. Q.
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Bochenek, Aleksandra
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Rusholme, Ben
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Laher, Russ R.
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Smith, Roger
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Purdum, Josiah
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Sravan, Niharika
Abstract
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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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