X-RAY OBSERVATIONS OF DISRUPTED RECYCLED PULSARS: NO REFUGE FOR ORPHANED CENTRAL COMPACT OBJECTS

Abstract

We present a Chandra X-ray survey of the disrupted recycled pulsars (DRPs), isolated radio pulsars with P > 20 ms and B_s < 3E10 G. These observations were motivated as a search for the immediate descendants of the approx. 10 central compact objects (CCOs) in supernova remnants, three of which have similar timing and magnetic properties as the DRPs, but are bright, thermal X-ray sources consistent with minimal neutron star cooling curves. Since none of the DPRs were detected, there is no evidence that they are "orphaned" CCOs, neutron stars whose supernova remnants has dissipated. Upper limits on their thermal X-ray luminosities are in the range log Lx[erg/s] = 31.8-32.8, which implies cooling ages > 1E4 - 1E5 yr, roughly 10 times the ages of the approximately 10 known CCOs in a similar volume of the Galaxy. The order of a hundred CCO descendants that could be detected by this method are thus either intrinsically radio quiet, or occupy a different region of (P,B_s) parameter space from the DRPs. This motivates a new X-ray search for orphaned CCOs among radio pulsars with larger B-fields, which could verify the theory that their fields are buried by fall-back of supernova ejecta, but quickly regrow to join the normal pulsar population.