Neutron Star Models.

Previous models of neutron stars were constructed with the assumption that the equation of state of a neutron gas is that of non4nteracting Fermi gas. Such models have a maximum observable mass of about 0.7 solar mass. In fact, the potential energy of a neutron gas depends on the density; this introduces additional terms into the equation of state. A revised equation of state has been derived which makes use of a mean nuclear potential recently given by T. H. R. Skyrme. Twenty neutron star models have been constructed by integrating the general relativistic equations of hydrostatic equilihrium of the neutron gas. The results show that there is an upper limit to the observahle mass of about 2 solar masses; the corresponding upper limit to the proper mass is about 3 solar masses. There is a lower limit to each of these masses of about 0.05 solar mass, below which the neutron star is unstable against transformation into an iron star. The radii of these neutron stars lie in the range 7-9 km. A qualitative discussion of the effects of transformation of neutrons into hyperons at very high densities is given.