Companion stars of type Ia supernovae with different metallicities

Abstract

The single-degenerate model is the most widely accepted progenitor model of Type Ia supernovae (SNe Ia), where a carbon-oxygen white dwarf (CO WD) accretes hydrogen-rich material from its companion to increase its mass. The companion may be a main-sequence (MS) star or a subgiant star (WD + MS). When the CO WD approaches the Chandrasekhar mass limit, it explodes as a SN Ia and part of the supernova ejecta collides into the companion envelope. After the impact of the ejecta, the companion survives and may show some special properties. A good way to verify the single-degenerate model is to study the interaction between the supernova ejecta and the companion, and/or search for the companion in the remnant of a SN Ia. Following previous studies, we have carried out a series of binary population synthesis studies exploring the properties of the companions of SNe Ia for different metallicities Z. We present the distributions of the masses MSN2, radii RSN2 of the companions, periods PSN and ratios of separations to radii A/R SN2 of WD + MS systems for various Z at the moment of supernova explosion. These parameters can be applied to constrain the numerical simulation of the interaction between the ejecta of a supernova and its companion. We also show the distributions of some integral properties of the companions, i.e. the mass, the space velocity and the surface gravity, for various Z after the interaction. The distributions may help us to search for the companion in a supernova remnant. All the parameters above change significantly with Z. Incorporating the simulation results of the interaction between supernova ejecta and companions from other works into our binary population synthesis study, we found that more than 75 per cent of all supernovae have a strong enough polarization signal to be detected by spectropolarimetric observations. We also found that 13-14 per cent of SNe Ia belong to the class of supernovae like 1991T, which is consistent with observations within the errors. This may indicate that 1991T-like SNe do not have any special physical properties except for the viewing angle of the observer. © 2009 RAS.