SN 2013ej in M74: A Luminous and Fast-declining Type II-P Supernova

We present extensive ultraviolet, optical, and near-infrared observations of the Type IIP supernova (SN IIP) 2013ej in the nearby spiral galaxy M74. The multicolor light curves, spanning from similar to 8-185 days after explosion, show that it has a higher peak luminosity (i.e., M-V similar to -17.83 mag at maximum light), a faster post-peak decline, and a shorter plateau phase (i.e., similar to 50 days) compared to the normal Type IIP SN 1999em. The mass of Ni-56 is estimated as 0.02 +/- 0.01 M-circle dot from the radioactive tail of the bolometric light curve. The spectral evolution of SN 2013ej is similar to that of SN 2004et and SN 2007od, but shows a larger expansion velocity (i.e., v(Fe II) similar to 4600 km s(-1) at t similar to 50 days) and broader line profiles. In the nebular phase, the emission of the H alpha line displays a double-peak structure, perhaps due to the asymmetric distribution of Ni-56 produced in the explosion. With the constraints from the main observables such as bolometric light curve, expansion velocity, and photospheric temperature of SN 2013ej, we performed hydrodynamical simulations of the explosion parameters, yielding the. total explosion energy as similar to 0.7x 10(51) erg, the. radius of the progenitor as similar to 600 R-circle dot, and the ejected mass as similar to 10.6M(circle dot). These results suggest that SN 2013ej likely arose from a red supergiant with a mass of 12-13M(circle dot) immediately before the explosion.