Searching for the presence of a circumstellar medium is a direct observational way to discriminate between different types of progenitor systems for Type Ia supernovae. We have modeled whether such gas may give rise to detectable emission, especially in H-alpha, and compare the models with observations of SN 1994D. We obtain a mass loss rate less than about 2.5 10^{-5} solar masses per year for a wind speed of 10 km/s. We find that X-ray observations in the range 5-10 keV, e.g., with AXAF, provide the most useful limits on the mass loss, while high-resolution optical spectroscopy offers the only direct way of identifying circumstellar hydrogen.
@article{arxiv.astro-ph/9610022,
title = {Supernova progenitor constraints from circumstellar interaction: Type Ia},
author = {Peter Lundqvist and Robert J. Cumming},
journal= {arXiv preprint arXiv:astro-ph/9610022},
year = {2007}
}