A1 Refereed original research article in a scientific journal
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 é., 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.
Publisher: Oxford University Press
Publication year: 2016
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 463
Issue: 4
First page : 3894
Last page: 3920
Number of pages: 27
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stw2253
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.
