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We present densely-sampled U BV RI/griz photometric and low-resolution (6-10Å) optical spectroscopic observations from 4 to 270 days after explosion of a newly discovered type II SN 2012aw in a nearby (∼9.9 Mpc) galaxy M95. The light-curve characteristics of apparent magnitudes, colors, bolometric luminosity and the presence and evolution of prominent spectral features are found to have striking similarity with the archetypal IIP SNe 1999em, 1999gi and 2004et. The early time observations of SN 2012aw clearly detect minima in the light-curve of V , R and I bands near 37 days after explosion and this we suggest to be an observational evidence for emergence of recombination phase. The mid-plateau M V magnitude (−16.67 ± 0.04) lies in between the bright (∼ −18) and subluminous (∼ −15) IIP SNe. The mass of nickel is 0.06 ± 0.01 M ⊙ . The SYNOW modelling of spectra indicate that the value and evolution of photospheric velocity is similar to SN 2004et, but about ∼600 km s −1 higher than that of SNe 1999em and 1999gi at comparable epochs. This trend is more apparent in the line velocities of Hα and Hβ. A comparison of ejecta velocity properties with that of existing radiation-hydrodynamical simulations indicate that the energy of explosion lies in the range 1-2×10 51 ergs; a further comparison of nebular phase [O i] doublet luminosity with SNe 2004et and 1987A indicate that the mass of progenitor star is about 14-15 M ⊙ . The presence of high-velocity absorption features in the mid-to-late plateau and possibly in early phase spectra show signs of interaction between ejecta and the circumstellar matter; being consistent with its early-time detection at X-ray and radio wavebands.

We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M 61. Photometric data in the X-rays, ultraviolet and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ∼ 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. (2010) indicates that it is a less energetic event (∼ 5 × 10 50 erg). However, the light curve indicates that the production of radioactive 56 Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of A V ∼ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized 56 Ni mass of ∼ 0.015M ⊙ . Employing semi-analytical formulae (Litvinova & Nadezhin 1985), we derived a pre-SN radius of ∼ 126R ⊙ , an explosion energy of ∼ 5.4 × 10 50 erg and a total ejected mass of ∼ 16.7M ⊙ . The latter indicates that the zero age main-sequence mass of the progenitor did not exceed 20M ⊙ . Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] ∼ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.