Radio emission from a type I supernova : SN 1983.51 in NGC 5236.

For the first time, radio emission has been detected from a Type I supernova. SN 1983.51 (SN 1983n) was discovered optically on July 3, 1983 and reached maximum light on approximately July 17, 1983. Radio observation of the position of the optical supernova detected a source of flux density 2.0 + or - 0.5 mJy at 6 cm wavelength already on July 6, 1983. The radio emission is almost certainly nonthermal in origin with an optically thin spectral index between 20 and 6 cm of alpha = -1.0 + or - 0.1. A detailed radio 'light curve' has been determined at 6 cm with additional data also available at 20 cm and 2 cm wavelengths. From the available radio information models have been constructed to describe the physical processes occurring in the supernova and to estimate the initial parameters of the progenitor stellar system.