Unusual pulsed X-ray emission from the young, high magnetic field pulsar PSR J1119-6127

We present XMM-Newton observations of the radio pulsar PSR J1119-6127, which has an inferred age of 1700 yr and surface dipole magnetic field strength of 4: 1; 1013 G. We report the first detection of pulsed X-ray emission from PSR J1119-6127. In the 0.5-2.0 keV range, the pulse profile shows a narrow peak with a very high pulsed fraction of 74% +/- 14%. In the 2.0-10.0 keV range, the upper limit for the pulsed fraction is 28% (99% confidence). The pulsed emission is well described by a thermal blackbody model with a temperature of T-infinity = 2.4(-0.2)(+0.3) x 10(6) K and emitting radius of 3.4(-0.3)(+1.8) km (at a distance of 8.4 kpc). Atmospheric models result in problematic estimates for the distance/emitting area. PSR J1119-6127 is now the radio pulsar with smallest characteristic age from which thermal X- ray emission has been detected. The combined temporal and spectral characteristics of this emission are unlike those of other radio pulsars detected at X- ray energies and challenge current models of thermal emission from neutron stars.