RADIO-EMISSION FROM TYPE IA SUPERNOVAE AS A TEST OF SYMBIOTIC-STAR PROGENITOR SYSTEMS

The nature of the binary systems that are the immediate progenitors of Type Ia supernovae (SNe Ia) remains an open question. We propose that deep, early searches for radio emission from relatively nearby SNe Ia could test the possibility that the progenitor system consists of a white dwarf accreting from the wind of a red-giant companion, i.e., the symbiotic-star scenario. To illustrate the nature of the radio emission that might be expected, we predict the radio light curve of SN; 1986G in NGC 5128 (Centaurus A) by scaling it against the observed radio light curve of the Type Ib SN 1983N in NGC 5236, a member of the same group of galaxies as NGC 5128. Although the density of the circumstellar medium surrounding a symbiotic system is expected to be lower than that surrounding the Type II and Ib/c supernovae from which radio emission has been detected, we find that relatively nearby SNe Ia such as SN 1986G, if they are coming from symbiotic systems, should be detectable by deep early radio observations. The lower density of the circumstellar medium leads to a weaker radio emission at a given time after explosion, but because the lower density reduces the free-free absorption in the circumstellar medium, the ratio light curve peaks at an earlier time. Consequently the peak luminosity does not depend strongly an the density of the circumstellar medium.