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Title: Dead or Alive? Long-term evolution of SN 2015bh (SNhunt275)
Authors: Elias-Rosa, N
Pastorello, A
Benetti, S
Cappellaro, E
Taubenberger, S
Terreran, G
Fraser, M
Brown, P. J
Tartaglia, L
Morales-Garoffolo, A
Harmanen, J
Richardson, N. D
Artigau, E
Tomasella, L
Margutti, R
Smartt, S. J
Dennefeld, M
Turatto, M
Anupama, G. C
Arbour, R
Berton, M
Bjorkman, K. S
Boles, T
Briganti, F
Chornock, R
Ciabattari, F
Cortini, G
Dimai, A
Gerhartz, C. J
Itagaki, K
Kotak, R
Mancini, R
Martinelli, F
Milisavljevic, D
Misra, K
Ochner, P
Patnaude, D
Polshaw, J
Sahu, D. K
Zaggia, S
Keywords: Stars: evolution;Supernovae: general;Supernovae: individual: SN 2015bh;Supernovae: individual: SN 2009ip;Galaxies: individual: NGC 2770
Issue Date: 21-Dec-2016
Publisher: Oxford University Press on behalf of the Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, Vol.463, No. 4, pp. 3894-3920
Abstract: Supernova (SN) 2015bh (or SNhunt275) was discovered in NGC 2770 on 2015 February with an absolute magnitude of Mr ∼ −13.4 mag, and was initially classified as an SN impostor. Here, we present the photometric and spectroscopic evolution of SN 2015bh from discovery to late phases (∼1 yr after). In addition, we inspect archival images of the host galaxy up to ∼21 yr before discovery, finding a burst ∼1 yr before discovery, and further signatures of stellar instability until late 2014. Later on, the luminosity of the transient slowly increases, and a broad light-curve peak is reached after about three months. We propose that the transient discovered in early 2015 could be a core-collapse SN explosion. The pre-SN luminosity variability history, the long-lasting rise and faintness first light-curve peak suggests that the progenitor was a very massive, unstable and blue star, which exploded as a faint SN because of severe fallback of material. Later on, the object experiences a sudden brightening of 3 mag, which results from the interaction of the SN ejecta with circumstellar material formed through repeated past mass-loss events. Spectroscopic signatures of interaction are however visible at all epochs. A similar chain of events was previously proposed for the similar interacting SN 2009ip.
Description: Restricted Access
ISSN: 1365-2966
???metadata.dc.rights???: © Royal Astronomical Society
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