Asymmetry of $^{56}$Ni ejecta and polarization in type IIP supernova 2004dj

Abstract

I study a problem, whether the asymmetry of a $^{56}$Ni ejecta that results in the asymmetry of the H$α$ emission line at the nebular epoch of the type IIP supernova SN 2004dj is able also to account for the recently detected polarization of the supernova radiation. I developed a model of the H$α$ profile and luminosity with a nonthermal ionization and excitation taken into account adopting an asymmetric bipolar $^{56}$Ni distribution. On the background of the recovered distribution of the electron density I calculated the polarized radiation transfer. It is demonstrated that the observed polarization is reproduced at the nebular epoch around day 140 for the same parameters of the envelope and $^{56}$Ni distribution for which the luminosity and profile of H$α$ are explained.