NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-04-26 T09:38:50 PDT
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For refcode 2018MNRAS.476.3611G:
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Copyright by Royal Astronomical Society. 2018MNRAS.476.3611G SN 2015as: a low-luminosity Type IIb supernova without an early light-curve peak Gangopadhyay, Anjasha; Misra, Kuntal; Pastorello, A.; Sahu, D. K.; Tomasella, L.; Tartaglia, L.; Singh, Mridweeka; Dastidar, Raya; Srivastav, S.; Ochner, P.; Brown, Peter J.; Anupama, G. C.; Benetti, S.; Cappellaro, E.; Kumar, Brajesh; Kumar, Brijesh; Pandey, S. B. 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 ^56^Ni mass of ~0.08 M_&sun;_ and ejecta mass of 1.1-2.2 M_&sun;_, 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_&sun;_), a nearly compact (~0.05 x 10^13^ cm) H envelope on top of a dense, compact (~2 x 10^11^ cm) and a more massive (~1.2 M_&sun;_) He core. The analysis of the nebular phase spectra indicates that ~0.44 M_&sun;_ 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_&sun;_ or a Wolf-Rayet star of 20 M_&sun;_. Key words: techniques: photometric, techniques: spectroscopic, supernovae: general, supernovae: individual: SN 2015as, galaxies: individual: UGC 5460
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