Radio observations have shown that some supernovae are powerful radio emitters which increase rapidly in brightness to radio luminosities which are hundreds to thousands of times greater than even the brightest known supernova remnant, Cas A. They then fade over a period of weeks, months, or years. This radio emission has been found to provide important information about the nature of the progenitor stars, their mass loss rates, and the circumstellar material surrounding them. RSN observations may also offer the possibility of extragalactic distance measurements and the presence of radio emission appears to be indicator of strong x-ray emission and late time optical emission.

Introduction

Detailed studies of radio emission from supernovae have now been carried out for over a decade with SN1979C providing the first example of a radio supernova (RSN) which could be detected and monitored in detail over a lengthy time span. The monitoring of the radio emission from SN1979C is still continuing. Additionally, in the intervening 13 years a number of other SNe have been detected at radio wavelengths and these are listed in Table 1. This list is complete at the present time. However, it is limited to objects which show most or all of the RSN properties which are listed in Section 5, and in practice includes only “young” SNe occurring since the first radio detection of an SN, SN1970G, by Gottesman et al. (1972).