2006ApJ...649L..95Y

A recent X-ray observation has shown that the radio pulsar PSR B0943+10, with clear drifting subpulses, has a much smaller polar cap area than that of conventional pulsars with mass of ∼1 M_☉and radius of ∼10 km. Zhang and coworkers have addressed the fact that this new result conflicts with the standard vacuum gap model. Nonetheless, the discrepancy could be explained if PSR B0943+10 is actually a low-mass quark star. We find that the potential drop in the open field line region of oblique pulsars (i.e., inclination angle α≠0) might be ∼10² times that of aligned pulsars, and that PSR B0943+10 with α=12°.4 could be well above the death line. We thus conclude that the Ruderman-Sutherland-type vacuum gap model still works well for this pulsar if it is a bare quark star with a mass of ∼0.02 M_☉and a radius of ∼2.6 km.