| Authors Affiliation: | 1 ST. JOSEPH'S UNIVERSITY, BANGALORE - 560027, INDIA
2 INDIAN INSTITUTE OF ASTROPHYSICS, BANGALORE - 560034, INDIA
3 HOMI BHABHA CENTRE FOR SCIENCE EDUCATION, TIFR, MUMBAI - 500004, INDIA |
| Abstract: | Type-II supernovae in progenitors with an extended H-envelope follow a light curve with three
distinctive phases: (a) an initial cooling peak (b) a recombination plateau, as the ionized hydrogen
recombines, and finally, as the event enters the nebular phase, (c) a long tail fueled by radioactive
decay of 56Ni → 56Co → 56Fe. We present here a spectroscopic study of three type II events–
the radiobright SN2018ivc, SN2024exw and SN2024ggi– observed at similar epochs. The early
spectra reveal prominent emission lines, including Hα, Hβ, Hγ, Hδ, Hϵ, He I, C IV, and Fe I, II,
and III, and absorption features of Na I, all with varying intensities as the SNe evolves. In the late
nebular stage, the Ca II and [Ca II] NIR lines and other metal lines also emerge. We present a
detailed analysis of the Balmer line profiles, notably Hα, which retain their characteristic P-Cygni
structure well into the nebular phase. We use our spectral studies to characterize the progenitor’s
and its environment’s properties (e.g. mass, local metallicity, etc.), and to quantify the dynamics
of shock-ejecta interactions as a function of the progenitor characteristics.
Key words: Type-II SNe, H-envelope, SN2018ivc, SN2024exw, SN2024ggi, P-Cygni , mass,
metallicity |
