RADIO OBSERVATIONS OF THE TYPE IA SUPERNOVA 1986G AS A TEST OF A SYMBIOTIC-STAR PROGENITOR

Searches for prompt radio emission from Type Ia supernovae (SNe Ia) have been proposed as a test of the symbiotic-star progenitor scenario, in which a white dwarf accretes mass from the wind of a companion red giant (Boffi & Branch 1995a). We report the results of a VLA search for radio emission from the Type Ia supernova 1986G in NGC 5128 (Centaurus A), 1 week before its optical maximum. These observations allow us to establish earlier and lower limits on SN Ia radio emission than previously available. Our 3 sigma upper limits of 1.0 mJy at 6 cm and 0.7 mJy at 2 cm indicate that the progenitor of SN 1986G probably was not a symbiotic star. SN 1986G was a peculiar Type Ia supernova, and further searches for prompt radio emission from other SNe Ia are needed to more thoroughly test the symbiotic-star progenitor scenario.