2025/11/06 by Cai, Y. -Z., Pastorello, A., Maeda, K. +63
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2511.04337
We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at (3.5±0.8) × 1042 erg s-1, with a total radiated energy of (5.0±0.4) × 1048 erg. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni \Hei~lines and flash-ionisation emission lines of C \sc iii, N \sc iii, and He \sc ii. The P-Cygni \Hei~features gradually evolve and become emission-dominated in late-time spectra. The \Ha~line is detected throughout the entire spectral evolution, which indicates that the CSM is helium-rich with some residual amount of H. Our multiband light-curve modelling yields estimates of the ejecta mass of Mej = 0.98+0.30-0.20 \msun, with a kinetic energy of Ek = 0.13+0.03-0.02 × 1051 erg, and a 56Ni mass of MNi = 0.017 \msun. The inferred CSM properties are characterised by a mass of M_\rmCSM = 0.39+0.04-0.04 \msun, an inner radius of R0=15.6+1.9-2.0 AU, and a density ρCSM = (1.32±0.22)×10-11 \mathrmg cm-3. The multi-epoch spectra are well reproduced by the CMFGEN/ he4p0 model, corresponding to a He-ZAMS mass of 4~M_\odot. These findings are consistent with a scenario of an SN powered by ejecta-CSM interaction, originating from a low-mass helium star that evolved within an interacting binary system where the CSM with some residual hydrogen may originate from the mass-transfer process. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet star with H, or an Ofpe/WN9 star with fallback accretion, cannot be entirely ruled out.