Chandra X-Ray Point Sources, including Supernova 1979C, in the Spiral Galaxy M100

Abstract

Six x-ray point sources, with luminosities of $4 \times 10^{38} - 2 \times 10^{39} \rm ergs s^{-1}$ in the 0.4--7 keV band, were detected in Chandra observations of the spiral galaxy M100. One source is identified with supernova SN 1979C and appears to have roughly constant x-ray flux for the period 16--20 years after the outburst. The x-ray spectrum is soft, as would be expected if the x-ray emission is due to the interaction of supernova ejecta with circumstellar matter. Most of the other sources are variable either within the Chandra observation or when compared to archival data. None are coincident with the peak of the radio emission at the nucleus. These sources have harder spectra than the supernova and are likely x-ray binaries. M100 has more bright x-ray sources than typical for spiral galaxies of its size. This is likely related to active star formation occurring in the galaxy.