Supernova 2012aw - a high-energy clone of archetypal type IIP SN 1999em

TL;DR

This paper presents detailed photometric and spectroscopic observations of supernova 2012aw, revealing its similarities to archetypal type IIP supernovae, and estimates key explosion parameters and progenitor characteristics.

Contribution

It provides the first densely-sampled multi-band data of SN 2012aw, compares its properties with other IIP supernovae, and estimates explosion energy and progenitor mass.

Findings

SN 2012aw's light curve and spectral features closely resemble those of SN 1999em, 1999gi, and 2004et.

The explosion energy is estimated to be 1-2x10^51 ergs.

Progenitor star mass is approximately 14-15 solar masses.

Abstract

We present densely-sampled UBVRI/griz photometric and low-resolution (6-10A) 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 MV magnitude (-16.67 $\pm$ 0.04) lies in between the bright (~ -18) and subluminous (~ -15) IIP SNe. The mass of nickel is 0.06$\pm$0.01 M_sun. The SYNOW modelling of spectra indicate that the value and evolution of photospheric velocity is similar to SN 2004et, but about ~600 km/s higher than that of SNe 1999em and 1999gi at comparable epochs. This trend is more apparent in the line velocities of H alpha and H beta. A comparison of ejecta velocity properties with that of existing radiation-hydrodynamical simulations indicate that the energy of explosion lies in the range 1-2x10^51 ergs; a further comparison of nebular phase [Oi] doublet luminosity with SNe 2004et and 1987A indicate that the mass of progenitor star is about 14-15 M_sun. 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.