Neutron star mass-radius relation and their stability region

Abstract

We present a detailed analysis of the mass radius relations in the neutron stars which outline some interesting features about the morphology of such astrophysical objects. In particular we numerically integrate the Tolman-Oppenheimer-Volkoff equations in correspondence to different choices for the core equation of state and using the standard Harrison-Wheeler scheme for modelling the external envelope; in this procedure the central density of the star is to be regarded as a free parameter of the theory. The results of our integration show a crucial morphology in the mass-central density diagram which consists of the appearance of an existence domain; this achievement allows to characterize the astrophysical nature of an observed stellar object simply by its mass, i. e. when its values lies outside such domain we can exclude that the object under study is a neutron star. Furthermore we candidate (in alternative to the strange star proposal) neutron stars cores as the astrophysical object responsible for the mass radius profiles observed by Beppo Sax.