Chandra X-Ray Detection of the High Magnetic Field Radio Pulsar PSR J1718-3718

Abstract

We report on the serendipitous X-ray detection, using the Chandra X-Ray Observatory, of the radio pulsar PSR J1718-3718. This pulsar has one of the highest inferred surface dipole magnetic fields in the radio pulsar population (B = 7.4 × 1013 G), higher than that inferred for one well-known anomalous X-ray pulsar (AXP). The X-ray emission for PSR J1718-3718 appears pointlike and has a purely thermal spectrum, with kT = 0.145 keV and absorbed 0.5-2 keV flux of (6.3-6.9) × 10-15 ergs s-1 cm-2. We show that the pulsar's 2-10 keV luminosity is several orders of magnitude smaller than those of the nontransient AXPs and consistent with the predictions of standard models for initial cooling. The number of high magnetic field radio pulsars observed at X-ray energies now stands at five. All are X-ray faint, suggesting either that there is a significant physical distinction between high magnetic field radio pulsars and AXPs or that high magnetic field radio pulsars are, in fact, quiescent AXPs.