Paper detail

The rotation of surviving companion stars after type Ia supernova explosions in the WD+MS scenario

In the SD scenario of SNe Ia the companion survives the SN explosion and thus should be visible near the center of the SN remnant and may show some unusual features. A promising approach to test progenitor models of SNe Ia is to search for the companion in SNRs. Here we present the results of 3D hydrodynamics simulations of the interaction between the SN Ia blast wave and a MS companion taking into consideration its orbital motion and spin. The primary goal of this work is to investigate the rotation of surviving companions after SN Ia explosions in the WD+MS scenario. We use Eggleton's code including the optically thick accretion wind model to obtain realistic models of companions. The impact of the SN blast wave on these companions is followed in 3D hydrodynamic simulations employing the SPH code GADGET3. We find that the rotation of the companion does not significantly affect the amount of stripped mass and the kick velocity caused by the SN impact. However, in our simulations, the rotational velocity of the companion is significantly reduced to about 14% to 32% of its pre-explosion value due to the expansion of the companion and the fact that 55%-89% of the initial angular momentum is carried away by the stripped matter. Compared with the observed rotational velocity of the presumed companion star of Tycho's SN, Tycho G, of 6 km/s the final rotational velocity we obtain is still higher by at least a factor of two. Whether this difference is significant, and may cast doubts on the suggestion that Tycho G is the companion of SN 1572, has to be investigated in future studies. Based on binary population synthesis results we present, for the first time, the expected distribution of rotational velocities of companions after the explosion which may provide useful information for the identification of the surviving companion in observational searches in other historical SNRs.