Spectral signatures of H-rich material stripped from a non-degenerate companion by a Type Ia supernova

The single-degenerate scenario for Type Ia supernovae should yield metal-rich ejecta that enclose some stripped material from the non-degenerate H-rich companion star. We present a large grid of non-local thermodynamic equilibrium steady-state radiative transfer calculations for such hybrid ejecta and provide analytical fits for the H α luminosity and equivalent width. Our set of models covers a range of masses for 56 Ni and the ejecta, for the stripped material ( M st ), and post-explosion epochs from 100 to 300 d. The brightness contrast between stripped material and metal-rich ejecta challenges the detection of H I and He I lines prior to ~100 d. Intrinsic and extrinsic optical depth effects also influence the radiation emanating from the stripped material. This inner denser region is marginally thick in the continuum and optically thick in all Balmer lines. The overlying metal-rich ejecta blanket the inner regions, completely below about 5000 Å, and more sparsely at longer wavelengths. As a consequence, H β should not be observed for all values of M st up to at least 300 days, while H α should be observed after ~100 d for all M st ≥ 0.01 M ⊙ . Observational non-detections capable of limiting the H α equivalent width to