MSH 15-52 - A supernova remnant containing two compact X-ray sources

Abstract

Einstein observations show two small-diameter, bright X-ray sources within the shell of the Galactic radio supernova remnant (SNR) MSH 15-52. X-ray spectra and optical extinction indicate that both compact sources are at least as distant, 4.2 kpc, as the diffuse emission from the shell. The source closest to the middle of the remnant shows strong regular X-ray pulsations with a period of 0.150 s. The second source is associated with an optical knot within the Hα nebula RCW 89 close to the northwestern rim of the SNR. UK Schmidt telescope photographs of RCW 89 support the hypothesis that the Hα nebula is part of the whole SNR. The authors discuss various possibilities of incorporating the apparently young pulsar (characteristic age ≡1600 years), the apparently old SNR (>10,000 yr), and the bright knot into a single consistent system.