We present a photometric and spectroscopic analyses of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of M_ o = -17. 58 ± 0. 15, mag in 10. 6 days, and displays a rapid linear post-peak light-curve decline in all bands (e. g. γ_ 0-60 (V) = 0. 097 ± 0. 002 mathrm mag, -1), similar to most SNe Ibn. The optical pseudobolometric light curve peaks at (3. 5 erg s 10^ 42 -1, with a total radiated energy of (5. 0 erg. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni ̋ei lines and flash-ionisation emission lines of C 10^ 48 iii, N iii, and He ii. The P-Cygni ̋ei features gradually evolve and become emission-dominated in late-time spectra. The ̋a line is detected throughout the entire spectral evolution, which indicates that the circumstellar material (CSM) is helium-rich with some residual amount of hydrogen. Our multi-band light-curve modelling yields estimates of the ejecta mass of M_ ej = 0. 49^ +0. 11 _ -0. 09, with a kinetic energy of E_ k = 0. 06^ +0. 01 _ -0. 01 10^ 51, , and a erg 56 Ni mass of M_ Ni = 0. 018, The inferred CSM properties are characterised by a mass of M_ CSM = 0. 51^ +0. 05 _ -0. 04 an inner radius of R₀=17. 8^ +3. 6 _ -3. 0 AU, and a density of ρ_ CSM = (8. 3_ -1. 2 ^ +2. 7), -12 -3. The multi-epoch spectra are well reproduced by the CMFGEN/ model, corresponding to a He-ZAMS mass of 4 M_⊙ (H-ZAMS mass 18. 11 M_⊙, pre-SN mass 3. 16 M_⊙). 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. We also discuss an extreme scenario involving the possible merger of a helium white dwarf. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet (WR) star with hydrogen, or a transitional star between an Of and a WR type (e. g. an Ofpe/WN9 star) with fallback accretion cannot be entirely ruled out. he4p0
Cai et al. (Tue,) studied this question.