2018MNRAS.476..261B -
Mon. Not. R. Astron. Soc., 476, 261-270 (2018/May-1)
ASASSN-15no: the Supernova that plays hide-and-seek.
BENETTI S., ZAMPIERI L., PASTORELLO A., CAPPELLARO E., PUMO M.L., ELIAS-ROSA N., OCHNER P., TERRERAN G., TOMASELLA L., TAUBENBERGER S., TURATTO M., MORALES-GAROFFOLO A., HARUTYUNYAN A. and TARTAGLIA L.
Abstract (from CDS):
We report the results of our follow-up campaign of the peculiar supernova ASASSN-15no, based on optical data covering ∼300 d of its evolution. Initially the spectra show a pure blackbody continuum. After few days, the HeI λλ 5876 transition appears with a P-Cygni profile and an expansion velocity of about 8700 km s–1. Fifty days after maximum, the spectrum shows signs typically seen in interacting supernovae. A broad (FWHM ∼ 8000 km s–1) Hα becomes more prominent with time until ∼150 d after maximum and quickly declines later on. At these phases Hαstarts to show an intermediate component, which together with the blue pseudo-continuum are clues that the ejecta begin to interact with the circumstellar medium (CSM). The spectra at the latest phases look very similar to the nebular spectra of stripped-envelope SNe. The early part (the first 40 d after maximum) of the bolometric curve, which peaks at a luminosity intermediate between normal and superluminous supernovae, is well reproduced by a model in which the energy budget is essentially coming from ejecta recombination and 56Ni decay. From the model, we infer a mass of the ejecta Mej = 2.6 M☉; an initial radius of the photosphere R0 = 2.1 x 1014 cm; and an explosion energy Eexpl = 0.8 x 1051 erg. A possible scenario involves a massive and extended H-poor shell lost by the progenitor star a few years before explosion. The shell is hit, heated, and accelerated by the supernova ejecta. The accelerated shell+ejecta rapidly dilutes, unveiling the unperturbed supernova spectrum below. The outer ejecta start to interact with a H-poor external CSM lost by the progenitor system about 9-90 yr before the explosion.
Abstract Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
supernovae: general - supernovae: individual: ASASSN-15no
Simbad objects:
14
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