The pulsar supernova remnant connection

Despite over 25 yr of debate, it is still unclear what fraction of supernovae form pulsars. The question of associations between pulsars and shell-type supernova remnants is re-examined in the light of the many associations claimed in the last few years. We develop a simple model for the luminosity evolution of shell supernova remnants, and quantify the selection effects associated with their detection. In combination with existing models for pulsar evolution and detection, we perform Monte Carlo simulations and compare our results with the known sample of supernova remnants. We find that even if every supernova forms a fast-spinning pulsar, the number of shell type remnants that are expected to have an associated pulsar is even less than observed. As a consequence, we conclude that some claimed associations are merely geometric projection.