Coordinated optical, ultraviolet, radio and X-ray observations of supernova 1979c in M 100

Coordinated optical, ultraviolet, radio and X-ray observations of supernova 1979c in M 100 made in the first six weeks after its discovery are presented and discussed. On the basis of optical data, which indicate a maximum magnitude of -19.4, a decay rate of 0.046 magnitudes/day, a total radiative energy of 7 x 10 to the 49 erg, and optical lines originating in the upper layers of the main envelope, the supernova is classified as peculiar type II. Analysis of ultraviolet line spectra indicates that the UV absorption lines are of interstellar origin, while the emission lines reveal the presence of a UV-emitting shell in which the gas is highly ionized, expansion velocity is around 4000 km/sec and the radius is greater than twice the photospheric radius, and which may consist of compressed gas of pre-existing circumstellar material. Radio and X-ray observations have resulted only in upper limits which confirm the estimated radius of the UV shell.