EVLA OBSERVATIONS CONSTRAIN THE ENVIRONMENT AND PROGENITOR SYSTEM OF Type Ia SUPERNOVA 2011fe

Abstract

We report unique EVLA observations of SN 2011fe representing the most\nsensitive radio study of a Type Ia supernova to date. Our data place direct\nconstraints on the density of the surrounding medium at radii ~10^15-10^16 cm,\nimplying an upper limit on the mass loss rate from the progenitor system of\nMdot <~ 6 x 10^-10 Msol/yr (assuming a wind speed of 100 km/s), or expansion\ninto a uniform medium with density n_CSM <~ 6 cm^-3. Drawing from the observed\nproperties of non-conservative mass transfer among accreting white dwarfs, we\nuse these limits on the density of the immediate environs to exclude a phase\nspace of possible progenitors systems for SN 2011fe. We rule out a symbiotic\nprogenitor system and also a system characterized by high accretion rate onto\nthe white dwarf that is expected to give rise to optically-thick accretion\nwinds. Assuming that a small fraction, 1%, of the mass accreted is lost from\nthe progenitor system, we also eliminate much of the potential progenitor\nparameter space for white dwarfs hosting recurrent novae or undergoing stable\nnuclear burning. Therefore, we rule out the most popular single degenerate\nprogenitor models for SN 2011fe, leaving a limited phase space inhabited by\nsome double degenerate systems and exotic progenitor scenarios.\n