Three-dimensional Simulation of Double Detonations in the Double-degenerate Model for Type Ia Supernovae and Interaction of Ejecta with a Surviving White Dwarf Companion

We study the hydrodynamics and nucleosynthesis in the double-detonation model of Type Ia supernovae (SNe Ia) and the interaction between the ejecta and a surviving white dwarf (WD) companion in the double-degenerate scenario. We set up a binary star system with 1.0 and 0.6M(circle dot) carbon-oxygen (CO) WDs, where the primary WD consists of a CO core and helium (He) shell with 0.95 and 0.05M(circle dot), respectively. We follow the evolution of the binary star system from the initiation of an He detonation, ignition and propagation of a CO detonation, and the interaction of SN ejecta with the companion WD. The companion (or surviving) WD gets a flung-away velocity of similar to 1700 km s(-1) and captures Ni-56 of similar to 0.03M(circle dot) and He of 3 x 10(-4) M-circle dot. Such He can be detected on the surface of surviving WDs. The SN ejecta contains a "companion-origin stream" and unburned materials stripped from the companion WD (similar to 3 x 10(-3) M.), although the stream compositions would depend on the He shell mass of the companion WD. The ejecta has also a velocity shift of similar to 1000 km s(-1) due to the binary motion of the exploding primary WD. These features would be prominent in nebular-phase spectra of oxygen emission lines from the unburned materials like SN. 2010lp and iPTF14atg and of blue-or redshifted Fe-group emission lines from the velocity shift like a part of subluminous SNe. Ia. We expect that SN. Ia counterparts to the D-6 model would leave these fingerprints for SN Ia observations.