Radio emission from Type Ia supernovae: A test of symbiotic star progenitor systems. The case of SN1986G.

The progenitors of Type Ia supernovae are not known. Boffi and Branch (1995, hereafter BB95) have proposed that the radio emission from Type Ia supernovae could test the symbiotic star progenitor hypothesis. We have applied the model of the radio emission from supernovae to the Type La SN 1986G (in NGC 5128) and predicted its radio evolution. Various sets of parameters were used. From inspection of the light curves we conclude that a supernova of Type Ia, if its progenitor is a white dwarf in a symbiotic system, may be detectable by an instrument like the VLA, provided that early observations are obtained. The lower the circumstellar medium density, the earlier the light curve peaks. In the case of SN 1986G, the upper Limits at 2 and 6 cm, taken approximately one week before optical maximum (Eck et al. 1995) are in conflict with the range 10(-7) < M over dot (W), < 10(-6) M. yr(-1) which is the interesting range for symbiotic systems. Thus SN 1986G probably was not a white dwarf in a symbiotic system. Nonetheless further and deep observations of Type Ia supernovae are needed to test this progenitor scenario.