Shocking and Mass Loss of Compact Donor Stars in Type Ia Supernovae
In this paper Wong, White & Bildsten 2024, we model the interaction between type Ia supernova ejecta and a low-mass helium white dwarf/ helium star companion. We find that about 0.01 - 0.02 solar-masses of helium is swept up along with the ejecta. As a result of entropy deposition, the donor expands to ~0.1 - 0.2 solar-radii and remains luminous for about 10,000 years. The post-explosion properties of our helium white dwarf donor agrees reasonably with one of the hypervelocity stars, D6-2.
Below are movies from our 3D hydrodynamical simulations of a low-mass helium white dwarf donor. The left panel shows fraction of material belonging to the donor (yellow) and to the ejecta (blue). The right panel shows density.
As the ejecta sweeps around the donor white dwarf, a low-density cavity is created behind the donor. Some helium is swept up into the ejecta.
Here is a zoom-in version. A strong shock propagates through the center of the donor white dwarf, and deposits entropy there.
Due to the entropy deposition, the donor white dwarf expands to ~0.1 solar radii.
The donor white dwarf undergoes a series of oscillations as it comes back to hydrostatic equilibrium.
You can find more movies from our repository on Zenodo.