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Post Info TOPIC: Supernova 2013ej
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RE: Supernova 2013ej
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Title: SN 2013ej - A type IIL supernova with weak signs of interaction
Author: Subhash Bose, Firoza Sutaria, Brijesh Kumar, Chetna Duggal, Kuntal Misra, Peter J. Brown, Mridweeka Singh, Vikram Dwarkadas, Donald G. York, Sayan Chakraborti, H.C. Chandola, Julie Dahlstrom, Alak Ray, Margarita Safonova

We present optical photometric and spectroscopic observations of supernova 2013ej. It is one of the brightest type II supernovae exploded in a nearby (~10 Mpc) galaxy NGC 628. The light curve characteristics are similar to type II SNe, but with a relatively shorter (~85 day) and steeper (~1.7 mag (100 d)-1 in V) plateau phase. The SN shows a large drop of 2.4 mag in V band brightness during plateau to nebular transition. The absolute ultraviolet (UV) light curves are identical to SN 2012aw, showing a similar UV plateau trend extending up to 85 days. The radioactive 56Ni mass estimated from the tail luminosity is 0.02 solar masses which is significantly lower than typical type IIP SNe. The characteristics of spectral features and evolution of line velocities indicate that SN 2013ej is a type II event. However, light curve characteristics and some spectroscopic features provide strong support in classifying it as a type IIL event. A detailed SYNOW modelling of spectra indicates the presence of some high velocity components in H and H profiles, implying possible ejecta-CSM interaction. The nebular phase spectrum shows an unusual notch in the H emission which may indicate bipolar distribution of 56Ni. Modelling of the bolometric light curve yields a progenitor mass of ~14 solar masses and a radius of ~450 solar radii, with a total explosion energy of ~2.3 x 1051 erg.

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Title: SN 2013ej in M74: A Luminous and Fast-declining Type II-P Supernova
Author: Fang Huang, Xiaofeng Wang, Jujia Zhang, Peter J. Brown, Luca Zampieri, Maria Letizia Pumo, Tianmeng Zhang, Juncheng Chen, Jun Mo, Xulin Zhao

We present extensive ultraviolet, optical, and near-infrared observations of the type IIP supernova (SN IIP) 2013ej in the nearby spiral galaxy M74. The multicolour 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 solar masses 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., vFeII~ 4600 km s-1 at t ~ 50 days) and broader line profiles. In the nebular phase, the emission of H alpha 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 x 1051 erg, the radius of the progenitor as ~600 solar radii, and the ejected mass as ~10.6 solar masses. These results suggest that SN 2013ej likely arose from a red supergiant with a mass of 12--13 solar mass immediately before the explosion.

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