2015MNRAS.454.4293P

We present spectroscopic and photometric observations for the Type Ibn supernova (SN) dubbed PSN J07285387+3349106. Using data provided by amateur astronomers, we monitored the photometric rise of the SN to maximum light, occurred on 2015 February 18.8 ut (JDmax(V) = 245 7072.0±0.8). PSN J07285387+3349106 exploded in the inner region of an infrared luminous galaxy, and is the most reddened SN Ibn discovered so far. We apply multiple methods to derive the total reddening to the SN, and determine a total colour excess E(B - V)tot = 0.99±0.48 mag. Accounting for the reddening correction, which is affected by a large uncertainty, we estimate a peak absolute magnitude of MV = -20.30±1.50. The spectra are dominated by continuum emission at early phases, and Hei lines with narrow P-Cygni profiles are detected. We also identify weak FeIII and NII features. All these lines show an absorption component which is blueshifted by about 900-1000 km/s. The spectra also show relatively broad Hei line wings with low contrast, which extend to above 3000 km/s. From about two weeks past maximum, broad lines of Oi, MgII and the CaII near-infrared triplet are identified. The composition and the expansion velocity of the circumstellar material, and the presence of Hei and α-elements in the SN ejecta indicate that PSN J07285387+3349106 was produced by the core collapse of a stripped-envelope star. We suggest that the precursor was WNE-type Wolf-Rayet star in its dense, He-rich circumstellar cocoon.