Impact of Type Ia Supernova Ejecta on a Helium-star Binary Companion

TL;DR

This study uses high-resolution hydrodynamic simulations to explore how Type Ia supernova ejecta impact helium-star companions, revealing relationships between unbound mass, kick velocity, and binary separation, with implications for supernova remnant observations.

Contribution

It provides the first detailed analysis of supernova ejecta impact on helium-star companions, establishing power-law relations and comparing results with hydrogen-rich cases.

Findings

Unbound mass scales with binary separation as a power law, index varies from -3.1 to -4.0.

Kick velocity also follows a power law, with index from -2.7 to -3.3.

Upper limit on nickel contamination in the companion is approximately 5×10^{-4} solar masses.

Abstract

The impact of Type Ia supernova ejecta on a helium-star companion is investigated via high-resolution, two-dimensional hydrodynamic simulations. For a range of helium-star models and initial binary separations it is found that the mass unbound in the interaction, $\delta M_{\rm ub}$, is related to the initial binary separation, $a$, by a power law of the form $\delta M_{\rm ub} \propto a^{m}$. This power-law index is found to vary from -3.1 to -4.0, depending on the mass of the helium star. The small range of this index brackets values found previously for hydrogen-rich companions, suggesting that the dependence of the unbound mass on orbital separation is not strongly sensitive to the nature of the binary companion. The kick velocity is also related to the initial binary separation by a power law with an index in a range from -2.7 to -3.3, but the power-law index differs from those found in previous studies for hydrogen-rich companions. The space motion of the companion after the supernova is dominated by its orbital velocity in the pre-supernova binary system. The level of Ni/Fe contamination of the companion resulting from the passage of the supernova ejecta is difficult to estimate, but an upper limit on the mass of bound nickel is found to be $\sim 5\times 10^{-4}\ M_\odot$.