Supernova remnants with compact X-ray sources

Observational data indicate that the supernova remnants (SNR) MSH 15 - 52 and RCW 89 and the optical knot within RCW 89 are part of a single system.Two compact X-ray sources, thought to be 4.2 kpc from earth, have been detected inside MSH 15 - 52. The knot displays forbidden Fe II lines as intense as Balmer lines. Filaments extend from RCW 89 to MSH 15 - 52. It is suggested that the supernova ejecta interact with the interstellar medium to produce the observed X-ray, optical, and radio features, implying that the two SNR are closer in age than previously thought. A pulsar may power the knot and RCW 89. Radial velocity observations of the Crab Nebula are also reported. The thick shell contains bright inner and dim outer components surrounded by a higher velocity halo. Synchrotron emissions arise from within the shell and are accompanied by a sharp brightness discontinuity at the bright inner shell.