Radio emission from supernovae. I - One to twelve year old supernovae

Abstract

As part of a continuing study of the radio emission from supernovae (SNs), we have used the VLA at 6 cm in 1982 May to observe all recorded optical supernovae brighter than 14.0 mag from SN 1970A to SN 1981A, i.e., all SNs with ages between 1 and 12 yr at the time of observation. Apart from the known radio supernovae (RSNs) in this age group (SN 1970G, SN 1979C, and SN 1980K), we obtained no new detections of radio emission from any of the objects to a limit of ~0.5 mJy. Consideration of these new results and other radio observations of SNs reported in the literature, combined with theoretical models, allows us to establish (limits on) mass-loss rates from the presupernova systems. The conclusions are that (1) Type Ia SNs originate in systems which contain very little circumstellar material at the time of explosion and which are very different from the systems which originate Type Ib SNs and (2) Type Il SNs, with a few obvious exceptions, originate in systems with the high presupernova mass-loss rates expected from red supergiant progenitors with original main-sequence masses greater than ~8 M_sun_. Most Type II SNs brighter than 12 mag should be detectable with the VLA if observed early enough.