SN 2013ej IN M74: A LUMINOUS AND FAST-DECLINING TYPE II-P SUPERNOVA
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2015. The American Astronomical Society. All rights reserved. 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 8-185 days after explosion, show that it has a higher peak luminosity (i.e., MV -17.83 mag at maximum light), a faster post-peak decline, and a shorter plateau phase (i.e., 50 days) compared to the normal Type IIP SN 1999em. The mass of 56Ni is estimated as 0.02 0.01 M 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., vFe II 4600 km s-1 at t 50 days) and broader line profiles. In the nebular phase, the emission of the H line displays a double-peak structure, perhaps due to the asymmetric distribution of 56Ni 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 0.7 1051 erg, the radius of the progenitor as 600 R, and the ejected mass as 10.6 M. These results suggest that SN 2013ej likely arose from a red supergiant with a mass of 12-13 M immediately before the explosion.