Psr 0943 + 10 : a Bare Strange Star ?

Recent work by Rankin & Deshpande strongly suggests that there exist strong " micro-storms " rotating around the magnetic axis of the 1.1s pulsar PSR 0943+10. Such a feature hints that most probably the large-voltage vacuum gap proposed by Ruderman & Sutherland (RS) does exist in the pulsar polar cap. However, there are severe arguments against the formation of the RS-type gap in pulsars, since the binding energies of both the 56 Fe ions and the electrons in a neutron star's surface layer is too small to prevent thermionic ejection of the particles from the surface. Here we propose that PSR 0943+10 (probably also most of the other " drifting " pulsars) might be bare strange stars rather than normal neutron stars, in which the " binding energy " at the surface is merely infinity either for the case of " pulsar " or " anti-pulsar ". It is further proposed that identifying a drifting pulsar as an anti-pulsar is the key criterion to distinguish strange stars from neutron stars. A wealth of observations has been collected for pulsars since the discovery of them more than thirty years ago. However, some important discrepancies still remain in our understanding of the particle acceleration mechanisms, the emission processes, and even the nature of pulsars. It is commonly agreed that there exists an inner accelerator near the magnetic polar cap region of a pulsar, but two subclasses of models appear in the literatures. The space-charge-limited flow models assume free ejection of particles of either sign from the star surface. Another type of models, however, assumes that certain particles (usually ions) could be bound in the surface layer of the star, so that a vacuum gap can form and keep breaking down to generate " sparks " continuously (Ruderman & Suther-Both subclasses of models have some observational supports, and it is very likely, different kinds of accelerators may exist in different pulsars. Maybe the strongest observational support to the RS-type vacuum gap model is the regular " drifting " of the subpulses observed from some pulsars. In such a model, the sparks produced by inner gap breakdown provide the source of the subpulses, and E × B drift due to the lack of charges within the gap causes the observed " drifting " phenomena. In their original paper (RS75), Ruderman & Sutherland has treated the " drifting sparking " process carefully in a detailed …