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|Title:||The spectacular evolution of Supernova 1996al over 15 yr: a low-energy explosion of a stripped massive star in a highly structured environment||Authors:||BENETTI, Stefano
Chugai, N. N.
Utrobin, V. P.
|Issue Date:||2016||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||456||Issue:||3||First Page:||3296||Abstract:||Spectrophotometry of SN 1996al carried out throughout 15 yr is presented. The early photometry suggests that SN 1996al is a linear Type II supernova, with an absolute peak of M<SUB>V</SUB> ∼ -18.2 mag. Early spectra present broad asymmetric Balmer emissions, with superimposed narrow lines with P-Cygni profile, and He I features with asymmetric broad emission components. The analysis of the line profiles shows that the H and He broad components form in the same region of the ejecta. By day +142, the Hα profile dramatically changes: the narrow P-Cygni profile disappears, and the Hα is fitted by three emission components that will be detected over the remaining 15 yr of the supernova (SN) monitoring campaign. Instead, the He I emissions become progressively narrower and symmetric. A sudden increase in flux of all He I lines is observed between 300 and 600 d. Models show that the SN luminosity is sustained by the interaction of low-mass (∼1.15 M<SUB>☉</SUB>) ejecta, expelled in a low kinetic energy (∼1.6 × 10<SUP>50</SUP> erg) explosion, with highly asymmetric circumstellar medium. The detection of Hα emission in pre-explosion archive images suggests that the progenitor was most likely a massive star (∼25 M<SUB>☉</SUB> ZAMS) that had lost a large fraction of its hydrogen envelope before explosion, and was hence embedded in a H-rich cocoon. The low-mass ejecta and modest kinetic energy of the explosion are explained with massive fallback of material into the compact remnant, a 7-8-M<SUB>☉</SUB> black hole.||URI:||http://hdl.handle.net/20.500.12386/25079||URL:||https://academic.oup.com/mnras/article/456/3/3296/1094385||ISSN:||0035-8711||DOI:||10.1093/mnras/stv2811||Bibcode ADS:||2016MNRAS.456.3296B||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Sep 23, 2020
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