On the minimum period of uniformly rotating meutron stars

Abstract

We show that the neutron star minimum period of rotation is determined, for causal equations of state, by the maximum value of the relativistic (compactness) parameter 2GM/Rc^2, allowed by causality for static neutron stars, 0.7081, and by the largest measured mass of a neutron star. The relation between these three quantities, resulting from the extrapolation of the empirical formulae of Lasota et al. (1996), yields the minimum period of 0.288 ms, only 2% higher than an absolute lower bound obtained in extensive exact numerical calculations of Koranda et al. (1997).