A high magnetic field radio pulsar survey with Swift/XRT

We present the X-ray survey results of high magnetic field radio pulsars (high-B PSRs) with Swift/XRT. X-ray observations of the rotation-powered pulsars with the dipole magnetic field B_d near the quantum critical field B_q = 4.4 × 10¹³ G is of great importance for understanding the transition between the rotation-powered pulsars and the magnetars, because there are a few objects that have magnetar-like properties. Out of the 27 high-B PSRs that are in the ATNF pulsar catalogue but have not been reported or have no effective upper limits in the X-ray bands, we analyse the Swift/XRT data for 21 objects, where 6 objects are newly observed and 15 objects are taken from the archival data. As a result, we have new 3σ upper limits for all the 21 objects. Since the upper limits are tight, we conclude that we do not find any magnetar-like high-B PSRs such as PSR J1819-1458. The probability of the high X-ray efficiency in the high-B PSRs is obtained to be 11-29 per cent. Combining the previous observations, we discuss which parameter causes magnetar-like properties. It may be suggested that the magnetar-like properties appear only when B_d ≳ 10^13.5 G for the radio pulsar population. This is true even if the radio-quiet high-B RPPs are included.