Detection of pulsed X-ray emission from XMM-Newton observations of PSR J0538+2817

We report on the XMM-Newton observations of the 143 ms pulsar PSR J0538+2817. We present evidence for the first detections of pulsed X-rays from the source at a frequency that is consistent with the predicted radio frequency. The pulse profile is broad and asymmetric, with a pulse fraction of 18% ± 3%. We find that the spectrum of the source is well-fitted with a blackbody with T^∞ = (2.12_-0.03^+0.04) × 10⁶ K and N_H = 2.5 × 10²¹ cm ^-2. The radius determined from the model fit of 1.68 × 0.05 km suggests that the emission is from a heated polar cap. A fit to the spectra with an atmospheric model reduces the inferred temperature and, hence, increases the radius of the emitting region; however, the pulsar distance determined from the fit is then smaller than the dispersion distance.