COMBINED BOSON FERMION STARS - CONFIGURATIONS AND STABILITY

We examine possible equilibrium configurations of cold stellar objects comprised of both fermions and bosons. The configurations are parametrized by the central densities of the bosons and fermions, and generalise the equilibrium configurations of both fermion stars and boson stars. For bosons and fermions to provide terms in the equations of structure of comparable size, the bosons must be extremely light, around 10-10 eV when the fermions are neutrons (the case we examine in detail, though this is purely illustrative). For boson masses some factors of ten larger, there are generically only two types of stellar configuration as the central densities are varied - those dominated by neutrons which have the magnitude of pure neutron star masses and those dominated by bosons which are several factors of ten lighter. The transition between these two types of behaviour is sudden. We find necessary (though not sufficient) conditions for stability by examining the binding energies of the configurations. © 1990.