Radio-quiet X-ray pulsars in Supernova Remnants and the ``Missing''   Pulsar Problem
  The paradigm that young neutron stars (NSs) evolve as rapidly rotating Crab-like pulsars requires re-examination. Evidence is accumulating that, in fact, many young NS are slowly rotating (P ~ 10-s) X-ray pulsars, lacking in detectable radio emission. We present new results on three radio-quiet NS candidates associated with supernova remnants, which suggests that alternative evolutionary-paths exist for young pulsars. These include the 12-s pulsator in Kes 73, the 7-s pulsar near Kes 75, and the enigmatic X-ray source in RCW 103. We postulate that such objects account for the apparent paucity of radio pulsars in supernova remnants. 
E. V. Gotthelf (GSFC/NASA)