An XMM-Newton observation of the drifting pulsar B0943+10

Radio pulsar subpulse drifting has been interpreted as rotation of subbeams ( sparks) of pair plasma produced by intermittent breakdowns of an inner vacuum gap above the pulsar polar cap. This model also predicts strong thermal X-ray emission from the polar cap caused by inflowing particles created in spark discharges. We have observed the best-studied drifting pulsar B0943 + 10 with XMM-Newton and detected a point source coincident with the radio pulsar position. Its spectrum could be fitted with a thermal blackbody model, although a powerlaw model is also acceptable. The thermal fit gives a bolometric luminosity L-bol approximate to 5 x 10(28) ergs s(-1) and a surface area A approximate to 10(3) (T/3 MK)(-4) m(2), much smaller than the conventional polar cap area, 6 x 10(4) m(2). Such thermal radiation can be interpreted as emitted from footprints of sparks drifting in an inner gap of a height h similar to (0.1-0.2)r(pc), where is the polar cap radius. However, the original vacuum gap model by Ruderman & Sutherland requires some modification to reconcile the X-ray and radio data.