2018/02/19 by Anjasha Gangopadhyay, Kuntal Misra, A. Pastorello +16
Physics and Astronomy · #Absolute magnitude #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Ejecta #Envelope (radar) #Galaxy #Gamma-ray bursts and supernovae #Light curve #Luminosity #Pair-instability supernova #Physics #Spectral line #Stars #Supernova #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1093/mnras/sty478
23 pages, 18 figures, 10 tables, Accepted for publication in MNRAS, 16 February, 2018
arxiv created 2018/02/19 · openalex publication_date 2018/02/21 · arxiv updated 2018/03/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract We present results of the photometric (from 3 to 509 d post-explosion) and spectroscopic (up to 230 d post-explosion) monitoring campaign of the He-rich Type IIb supernova (SN) 2015as. The (B − V) colour evolution of SN 2015as closely resemble those of SN 2008ax, suggesting that SN 2015as belongs to the SN IIb subgroup that does not show the early, short-duration photometric peak. The light curve of SN 2015as reaches the B-band maximum about 22 d after the explosion, at an absolute magnitude of −16.82 ± 0.18 mag. At ∼75 d after the explosion, its spectrum transitions from that of a SN II to a SN Ib. P Cygni features due to He i lines appear at around 30 d after explosion, indicating that the progenitor of SN 2015as was partially stripped. For SN 2015as, we estimate a 56Ni mass of ∼0.08 M⊙ and ejecta mass of 1.1–2.2 M⊙, which are similar to the values inferred for SN 2008ax. The quasi-bolometric analytical light-curve modelling suggests that the progenitor of SN 2015as has a modest mass (∼0.1 M⊙), a nearly compact (∼0.05 × 1013 cm) H envelope on top of a dense, compact (∼2 × 1011 cm) and a more massive (∼1.2 M⊙) He core. The analysis of the nebular phase spectra indicates that ∼0.44 M⊙ of O is ejected in the explosion. The intensity ratio of the [Ca ii]/[O i] nebular lines favours either a main-sequence progenitor mass of ∼15 M⊙ or a Wolf–Rayet star of 20 M⊙.