Chandra Observations of the High-Magnetic-Field Radio Pulsar J1718-3718

Abstract

High-magnetic-field pulsars represent an important class of objects for studying the relationship between magnetars and radio pulsars. Here we report on four Chandra observations of the high-magnetic-field pulsar J1718-3718 ($B=7.4\times10^{13}$\,G) taken in 2009 as well as on a re-analysis of 2002 Chandra observations of the region. We also report an improved radio position for this pulsar based on ATCA observations. We detect X-ray pulsations at the pulsar's period in the 2009 data, with pulsed fraction 52%$\pm$13% in the 0.8--2.0 keV band. We find that the X-ray pulse is aligned with the radio pulse. The data from 2002 and 2009 show consistent spectra and fluxes; a merged overall spectrum is well fit by a blackbody of temperature $186^{+19}_{-18}$\,eV, slightly higher than predicted by standard cooling models, however, the best-fit neutron star atmosphere model is consistent with standard cooling. We find the bolometric luminosity $L^{\infty}_{\rm bb}=4^{+5}_{-2} \times10^{32}$\,erg\,s$^{-1}\sim0.3\dot{E}$, for a distance of 4.5 kpc. We compile measurements of the temperatures of all X-ray detected high-$B$ pulsars as well as those of low-$B$ radio pulsars and find evidence for the former being on average hotter than the latter.