Hydrogen as a test of type Ia supernova progenitor models

If type Ia supernovae are produced by the explosion of a white dwarf accreting matter from a hydrogen-rich companion, the material stripped and ablated from the companion during the explosion will contaminate the supernova spectrum with hydrogen. The amount of material stripped and ablated from the companion is calculated, showing that a hydrogen mass fraction of at least X(H) greater than 0.01 should exist in type Ia supernovae if their progenitors are cataclysmic variable-like systems. This amount of hydrogen is barely consistent with current upper limits, but the inhomogeneous distribution of the hydrogenin the ejecta must be taken into account before detailed comparisons can be made. White dwarfs accreting from Roche lobe-filling red giants can probably be ruled out as SN Ia progenitors because they contaminate the spectrum with too much hydrogen. 11 refs.