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|Title:||ASASSN-15no: the Supernova that plays hide-and-seek||Authors:||BENETTI, Stefano
Pumo, M. L.
ELIAS DE LA ROSA, NANCY DEL CARMEN
|Issue Date:||2018||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||476||Issue:||1||First Page:||261||Abstract:||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<SUP>-1</SUP>. Fifty days after maximum, the spectrum shows signs typically seen in interacting supernovae. A broad (FWHM ∼ 8000 km s<SUP>-1</SUP>) 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 <SUP>56</SUP>Ni decay. From the model, we infer a mass of the ejecta M<SUB>ej</SUB> = 2.6 M<SUB>☉</SUB>; an initial radius of the photosphere R<SUB>0</SUB> = 2.1 × 10<SUP>14</SUP> cm; and an explosion energy E<SUB>expl</SUB> = 0.8 × 10<SUP>51</SUP> 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.||URI:||http://hdl.handle.net/20.500.12386/27863||URL:||https://academic.oup.com/mnras/article/476/1/261/4919569||ISSN:||0035-8711||DOI:||10.1093/mnras/sty166||Bibcode ADS:||2018MNRAS.476..261B||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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