We present medium-resolution spectroscopy and multicolor photometry for the optical transient PSN J09093496+3307204 ( SN 2015bh ) in the galaxy NGC 2770 , which has transferred into the supernova phase .
The observations were carried out between February 2015 to May 2016 .
Both at the phase of the SN impostor ( 2015a ) and at the supernova phase ( 2015b ) , besides Balmer emissions , the strong Fe II emissions are seen in the spectrum ; so , these spectra resemble those of Williams Fe II type classical novae .
The star is located near the edge of a dark nebula and notably absorbed ( A _ { V } = 1 \fm 14 \pm 0 \fm 15 ) .
Taking into account this absorption , we determined maximum absolute magnitudes of M _ { V } = –15 \fm 0 \pm 0 \fm 3 at the 2015a phase and of M _ { V } = –18 \fm 14 \pm 0 \fm 30 at the 2015b phase .
The light curve at the 2015b phase is similar to those of SN IIL .
The supernova progenitor is a luminous blue variable ( LBV ) star with the powerful H _ { \alpha } emission .
We considered several hypotheses of supernovae explosions following optical transients related with LBV .
The hypothesis of core collapse of an evolved massive star interrupting the process of its merging with massive companion in a binary system ( a failed luminous red nova ) was chosen as the preferable one for this event .