Observational signatures of the surviving donor star in the double-detonation model of Type Ia supernovae

The sub-Chandrasekhar-mass double-detonation (DDet) scenario is a contemporary model for Type Ia supernovae (SNe Ia). donor star in the DDet expected to survive explosion and be ejected at high orbital velocity of compact binary system. For first time, we consistently perform 3D hydrodynamical simulations interaction supernova ejecta with helium (He) companion within scenario. We map outcomes impact into 1D stellar evolution codes follow long-term surviving He-star companions. Our main goal provide post-impact observable signatures companions SNe Ia, which will support search such future observations. Such are velocities up about 930 km s −1 . find that our become significantly overluminous 10 6 yr during thermal re-equilibration phase. After re-establishes equilibrium, its observational properties not sensitive details ejecta-donor interaction. apply results hypervelocity US 708, one fastest unbound stars Galaxy; it travels 1200 , making natural candidate an remnant SN Ia. initial mass ≳0.5 M ⊙ needed explain observed 708. Based on detailed calculations, however, progenitor system massive cannot get close enough moment Instead, if 708 indeed would require entire pre-supernova travel 400 It could, example, have been from globular cluster direction current motion star.