Padova-Asiago Supernova Group
Highlights

Dead or Alive? Long-time evolution of SN 2015bh (SNhunt275)
Elias-Rosa, N., et al. 2016 MNRAS submitted (arXiv:1606.09024
  (link to pdf)

Supernova (SN) 2015bh (or SNhunt275) was discovered in NGC 2770 on 2015 February with an absolute magnitude of Mr ~ -13 mag, and was initially classified as a 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 ~ 16 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.



sn galaxy RA DEC discoverer type redshift ref class fits
Anonymous 21:12:23.35 +14:46:45.47 PS1 Ia 0.029 ATEL
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Anonymous 19:08:42.21 +49:44:17.2 PS1 CV 0 ATEL
 
galex 21:12:23.35 +14:46:45.1 MASTER Ia 0.029 ATEL
fits
anonymous 18:38:37.55 +41:31:40.37 PTSS Ia 0.069 ATEL
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UGC 11635 20:43:22.40 +80:09:14.6 V. Tinella Ia 0.016 ATEL
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