The impact of Type Ia supernova explosions on helium companions in the Chandrasekhar-mass explosion scenario

In the version of the single-degenerate scenario of Type Ia supernovae (SNe Ia) studied here, a carbon–oxygen white dwarf explodes close to the Chandrasekhar limit after accreting material from a non-degenerate helium (He) companion star. In the present study, we employ the Stellar GADGET code to perform threedimensional hydrodynamical simulations of the interaction of the SN Ia ejecta with the He companion star taking into account its orbital motion and spin. It is found that only 2% − 5% of the initial companion mass are stripped off from the outer layers of He companion stars due to the SN impact. The dependence of the unbound mass (or the kick velocity) on the orbital separation can be fitted in good approximation by a power law for a given companion model. After the SN impact, the outer layers of a He donor star are significantly enriched with heavy elements from the low-expansion-velocity tail of SN Ia ejecta. The total mass of accumulated SN-ejecta material on the companion surface reaches about & 10M⊙ for different companion models. This enrichment with heavy elements provides a potential way to observationally identify the surviving companion star in SN remnants. Finally, by artificially adjusting the explosion energy of the W7 explosion model, we find that the total accumulation of SN ejecta on the companion surface is also dependent on the explosion energy with a power law relation in good approximation. Subject headings: stars: supernovae: general methods: numerical binaries: close