Thöne, C.C., de Ugarte Postigo, A., Leloudas, G. et al. (13 more authors) (2017) SN 2015bh: NGC 2770’s 4th supernova or a luminous blue variable on its way to a Wolf-Rayet star? Astronomy & Astrophysics, 599. A129. ISSN 0004-6361
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 × 1049 erg, consistent with a <0.5 M⊙ 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.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | Reproduced with permission from Astronomy & Astrophysics, © ESO , 2017. |
Keywords: | supernovae ; individual ; SN 2015bh, SN 2009ip ; stars: massive |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 01 Jun 2017 09:18 |
Last Modified: | 01 Jun 2017 09:18 |
Published Version: | https://doi.org/10.1051/0004-6361/201629968 |
Status: | Published |
Publisher: | EDP Sciences |
Refereed: | Yes |
Identification Number: | 10.1051/0004-6361/201629968 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:117067 |