AAS Meeting #193 - Austin, Texas, January 1999
Session 41. Pulsars
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

[41.01] Radio-quiet X-ray Pulsars in SNRs and the Missing'' Pulsar Problem

E. V. Gotthelf (Columbia University)

The paradigm that young (< 104-5 yrs) neutron stars (NSs) evolve as rapidly rotating Crab-like pulsars requires re-examination. Recent comprehensive radio surveys suggest that most radio pulsars near SNRs can be attributed to chance overlap (e.g. Lorimer et al. 1998, AA, 331, 1002; Gaensler & Johnston 1995, MNRAS, 277, 1243; see Kaspi et al. 1996, AJ, 111, 2028 for a review). With the results of these new surveys, traditional arguments for the lack of observed radio pulsars associated with SNR, such as those invoking beaming and large kick'' velocities, are less compelling. It is now clear that this discrepancy is an important and vexing problem in current astrophysics.

Progress in resolving this mystery is suggested by recent X-ray observations of young SNRs. Evidence is accumulating that many young NSs are slowly rotating (P ~10-s) X-ray pulsars, lacking in detectable radio emission. There are currently about a dozen slow X-ray pulsars apparently associated with young SNRs. These include the four known soft \gamma-ray repeaters (SGR), which have recently been confirmed as slow rotators. In fact, there are now more known slow, radio-quiet X-ray pulsars in the center of identified SNR than confirmed Crab-like radio pulsars! Here, we consider the observational properties of these radio-quiet NS candidates associated with supernova remnants, which suggests that alternative evolutionary-paths exist for young pulsars. We postulate that such objects account for the apparent paucity of radio pulsars in supernova remnants.