A Radio and X-Ray Study of Historical Supernovae in M83

We report the results of 15 years of radio observations of the six historicalsupernovae (SNe) in M83 using the Very Large Array. We note the near lineardecline in radio emission from SN 1957D, a type II SN, which remains anon-thermal radio emitter. The measured flux densities from SNe 1923A and 1950Bhave flattened as they begin to fade below detectable limits, also type II SNe.The luminosities for these three SNe are comparable with the radio luminositiesof other decades-old SNe at similar epochs. SNe 1945B, 1968L, and 1983N werenot detected in the most recent observations and these non-detections areconsistent with previous studies. We report the X-ray non-detections of all sixhistorical SNe using the Chandra X-ray Observatory, consistent with previousX-ray searches of other decades-old SNe, and low inferred mass loss rates ofthe progenitors.Comment: 3 color ps figure