Type Ia Supernova Explosions in Binary Systems: The Impact on the Secondary Star and its Consequences

One method of discriminating between the many Type Ia progenitor scenarios is by searching for contaminating hydrogen and helium stripped from the companion star. However, this requires understanding the effect of the impact of the supernova shell on different companion stars to predict the amount of mass stripped and its distribution in velocity and solid angle for the types of binary scenarios that have been proposed as Type Ia progenitor models. We present several high-resolution 2-D numerical simulations of the impact of a Type Ia supernova explosion with hydrogen-rich main sequence, subgiant, and red giant companions. The binary parameters were chosen to represent several classes of single-degenerate Type Ia progenitor models that have been suggested in the literature. We use realistic stellar models and supernova debris profiles to represent each binary system. For each scenario, we explore the hydrodynamics of the supernova-secondary interaction, calculate the amount of stellar material stripped from the secondary and the kick delivered by the impact, and construct the velocity and solid angle distributions of the stripped material. We find that the main sequence and subgiant companions lose 0.15 − 0.17 M as a result of the impact of the supernova shell, 15% of their mass. The red giant companions lose 0.53 − 0.54 M , 96% − 98% of their envelopes. The characteristic velocity of the stripped hydrogen is less than 103 km s−1 for all the scenarios: 420−590 km s−1 for the red giant companions, 820 km s−1 for the main sequence companion, and 890 km s−1 for the subgiant companion. The stripped hydrogen and helium contaminate a wide solid angle behind the companion: 115◦ from the downstream axis for the red giant, 66◦ for the main sequence star, and 72◦ for the subgiant. With such low velocities, the bulk of the stripped hydrogen and helium is embedded within the low-velocity iron of the supernova ejecta. The hydrogen and helium may be visible in the late-time spectra as narrow emission lines. Although most of the stripped material is ejected at low velocities, all the numerical simulations yield a small high-velocity tail. The main sequence, subgiant, and the Department of Astronomy and Steward Observatory, The University of Arizona, Tucson, AZ 85721 Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637