The possibility and the implications of the idea, that pulsars are born as
strange stars, are explored. Strange stars are very likely to have atmosphe
res with typical mass of similar to5 x 10(-15)M. but bare polar caps almost
throughout their lifetimes, if they are produced during supernova explosio
ns. A direct consequence of the bare polar cap is that the binding energies
of both positively and negatively charged particles at the bare quark surf
ace are nearly infinity, so that the vacuum polar gap sparking scenario as
proposed by Ruderman and Sutherland should operate above the cap, regardles
s of the sense of the magnetic pole with respect to the rotational pole. He
at cannot accumulate on the polar cap region due to the large thermal condu
ctivity on the bare quark surface. We test this "bare polar cap strange sta
r" (BPCSS) idea with the present broad band emission data of pulsars, and p
ropose several possible criteria to distinguish BPCSSs from neutron stars.
(C) 2001 Elsevier Science B.V. All rights reserved.