2013MNRAS.431..308K

We present the low-resolution spectroscopic and UBVRI broad-band photometric investigations of the Type IIb supernova (SN) 2011fu, discovered in UGC 01626. The photometric follow-up of this event was initiated a few days after the explosion and covers a period of about 175d. The early-phase light curve shows a rise, followed by steep decay in all bands, and shares properties very similar to that seen for SN 1993J, with a possible detection of the adiabatic cooling phase. Modelling of the quasi-bolometric light curve suggests that the progenitor had an extended ( ∼ 1x1013 cm), low-mass ( ∼ 0.1M☉) H-rich envelope on top of a dense, compact ( ∼ 2x1011 cm), more massive ( ∼ 1.1M☉) He-rich core. The nickel mass synthesized during the explosion was found to be ∼ 0.21M☉, slightly larger than that seen for other Type IIb SNe. The spectral modelling performed with synow suggests that the early-phase line velocities for H and Feii features were ∼ 16 000 and ∼ 14 000 km s-1, respectively. Then, the velocities declined up to day +40 and became nearly constant at later epochs.