Neutron stars and strange stars

Abstract

If strange quark plasma is the real ground state of baryonic matter (Witten 1984), then some of neutron stars (NS) could actually be strange stars (SS). It is difficult to distinguish SS from NS observationally. They have similar radii and masses and their crusts are built of the same matter. It seems that a good method for testing the existence of SS would be the studies of phenomena related to the stellar pulsations. In 1976 Boriakoff proposed that radial oscillations of NS could be observed within radio subpulses of pulsars. While various modes of pulsations of NS were studied by a number of authors, little attention was paid to seismological signatures of SS. The radial oscilations of bare SS were studied by Väth & Chanmugam (1992). Recently Weber (this volume) studied properties of stars made of matter described by BPS equation of state (EOS) (Baym et al. 1971) with a ball of strange matter inside, but they mainly concentrated on stability of white-dwarf-like SS. In this work I present fully relativistic calculations of the radial oscillation frequencies of SS. I determined the fundamental frequency for bare SS and SS with two different types of crusts depending on origin (Alcock et al. 1986) of SS and showed differences between them.