Masses, radii, and magnetic fields of pulsating X-ray sources - Is the 'standard' model self-consistent

Abstract

We present prototype calculations for Her X-1 and 4U 0115+63 which are designed to test the ''standard'' model of a pulsating X-ray source for self-consistency. We construct ''semiempirical'' mass-radius (M-R/sub s/) relations for these two X-ray pulsars based on observational data (luminosities pulse periods, spin-up rates, cylotron spectral features) and their theoretical interpretation in terms of the MHD accretion torque theory of Ghosh and Lamb. These semiemperical M-R/sub s/, relations depend only on physical processes occurring exterior to an accreting neutron star. We compare them to theoretical M-R/sub s/ relations derived by integrating the hydrostatic equilibrium (Oppenheimer-Volkoff) equation for representative equations of state which might characterize the condensed matter in a neutron star's interior.