2002ApJ...573..306E

We report Very Large Array radio observations of 29 supernovae (SNe) with ages ranging from 10 days to about 90 yr past explosion. These observations significantly contribute to the existing data pool on such objects. Included are detections of known radio SNe 1950B, 1957D, 1970G, and 1983N, the suspected radio SN 1923A, and the possible radio SN 1961V. None of the remaining 23 observations resulted in detections, providing further evidence to support the observed trend that most SNe are not detectable radio emitters. To investigate the apparent lack of radio emission from the SNe reported here, we have followed standard practice and used Chevalier's ``standard model'' to derive (upper limits to) the mass-loss rates for the supernova progenitors. These upper limits to the fluxes are consistent with a lack of circumstellar material needed to provide detectable radio emission for SNe at these ages and distances. Comparison of the radio luminosities of these supernovae as a function of age past explosion to other well-observed radio SNe indicates that the Type II SNe upper limits are more consistent with the extrapolated light curves of SN 1980K than of SN 1979C, suggesting that SN 1980K may be a more typical radio emitter than SN 1979C. For completeness, we have included an appendix where the results of analyses of the non-SN radio sources are presented. Where possible, we make (tentative) identifications of these sources using various methods.