Observations of Supernova Remnants with the Einstein Observatory

Results obtained by the X-ray imaging experiments on board the Einstein Observatory concerning galactic supernova remnants are discussed. The observations show the Crab nebula to be a filled-in structure, and reveal the presence of X-ray pulsations, while those obtained for the other known SNR containing a pulsar, the Vela SNR, show a spectral difference between the nebula and the pulsar but have not detected X-ray pulsations. Of the SNRs for which no evidence of a compact remnant has yet been found, the Tycho SNR and SN 1006 appear very similar, exhibiting a very close relationship between their radio and X-ray features, having only thin optical filaments and having optical spectra with only hydrogen Balmer emission lines. Cas A, on the other hand, has a complex, roughly circular structure with various correlated and uncorrelated optical, radio, and X-ray features, some with different spectral distributions. Determinations of neutron star temperatures or upper limits to them for the remnants observed exclude the possibility of neutron star cooling by the standard neutrino process, however are compatible with a pion core stellar remnant.