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|Title:||SN 2015bh: NGC 2770's 4th supernova or a luminous blue variable on its way to a Wolf-Rayet star?||Authors:||Thöne, C. C.
de Ugarte Postigo, A.
de la Rosa, J.
Bauer, F. E.
|Issue Date:||2017||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||599||First Page:||A129||Abstract:||Very massive stars in the final phases of their lives often show unpredictable outbursts that can mimic supernovae, so-called, "SN impostors", but the distinction is not always straightforward. Here we present observations of a luminous blue variable (LBV) in NGC 2770 in outburst over more than 20 yr that experienced a possible terminal explosion as type IIn SN in 2015, named SN 2015bh. This possible SN (or "main event") had a precursor peaking 40 days before maximum. The total energy release of the main event is 1.8 × 10<SUP>49</SUP> erg, consistent with a <0.5 M<SUB>☉</SUB> shell plunging into a dense CSM. The emission lines show a single narrow P Cygni profile during the LBV phase and a double P Cygni profile post maximum suggesting an association of the second component with the possible SN. Since 1994 the star has been redder than an LBV in an S-Dor-like outburst. SN 2015bh lies within a spiral arm of NGC 2770 next to several small star-forming regions with a metallicity of 0.5 solar and a stellar population age of 7-10 Myr. SN 2015bh shares many similarities with SN 2009ip and may form a new class of objects that exhibit outbursts a few decades prior to a "hyper eruption" or final core-collapse. If the star survives this event it is undoubtedly altered, and we suggest that these "zombie stars" may evolve from an LBV to a Wolf-Rayet star over the timescale of only a few years. The final fate of these stars can only be determined with observations a decade or more after the SN-like event.||URI:||http://hdl.handle.net/20.500.12386/26916||URL:||https://www.aanda.org/articles/aa/abs/2017/03/aa29968-16/aa29968-16.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201629968||Bibcode ADS:||2017A&A...599A.129T||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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