Constraints on fall-back discs in radio pulsars and anomalous X-ray pulsars

Calculations have been made of fall-back disc heating by the pulsar wind as distinct from the soft X-rays emitted by the neutron-star surface. The relation between these heating rates and measured near-infrared fluxes in the K and K-s bands places severe constraints on the inner radii of any fall-back discs that may be present in radio pulsars and in some anomalous X-ray pulsars. The lower limits found are so large that the discs concerned can have no significant effect on pulsar spin-down.