We report unique EVLA observations of SN 2011fe representing the most sensitive radio study of a Type Ia supernova to date .
Our data place direct constraints on the density of the surrounding medium at radii \sim 10 ^ { 15 } -10 ^ { 16 } cm , implying an upper limit on the mass loss rate from the progenitor system of \dot { M } \lesssim 6 \times 10 ^ { -10 } ~ { } { { M } _ { \odot } { yr } ^ { -1 } } ( assuming a wind speed of 100 km s ^ { -1 } ) , or expansion into a uniform medium with density n _ { CSM } \lesssim 6 cm ^ { -3 } .
Drawing from the observed properties of non-conservative mass transfer among accreting white dwarfs , we use these limits on the density of the immediate environs to exclude a phase space of possible progenitors systems for SN 2011fe .
We rule out a symbiotic progenitor system and also a system characterized by high accretion rate onto the white dwarf that is expected to give rise to optically-thick accretion winds .
Assuming that a small fraction , 1 % , of the mass accreted is lost from the progenitor system , we also eliminate much of the potential progenitor parameter space for white dwarfs hosting recurrent novae or undergoing stable nuclear burning .
Therefore , we rule out much of the parameter space associated with popular single degenerate progenitor models for SN 2011fe , leaving a limited phase space largely inhabited by some double degenerate systems , as well as exotic single degenerates with a sufficient time delay between mass accretion and SN explosion .