A Deep Search for Radio Emission from the Type II Supernovae SN 1984E and SN 1986E

Abstract

We have used the VLA to place deep upper limits on the radio emission from the Type II-L supernovae SN 1984E in NGC 3169 and SN 1986E in NGC 4302. The optical spectra of SN 1984E near maximum light showed evidence of strong circumstellar interaction. The lack of detectable radio emission from SN 1984E at an age of 11 years is consistent with the idea that near its optical maximum SN 1984E was interacting with a circumstellar shell that resulted from a preexplosion mass-loss episode that was of limited duration. However, optical spectra of SN 1986E have shown that it was undergoing strong circumstellar interaction as recently as 1994. Therefore, the lack of detectable radio emission from SN 1986E in 1995 is surprising. SN 1986E is the first old supernova to have been detected in the optical but not in the radio. This calls for further detailed modeling of the optical and radio emission from circumstellar interaction.