Abstract
We propose to determine the mass and radius of a neutron star (NS) using three measurable mass-radius relationships, namely the 'apparent' radius inferred from the NS thermal emission, the gravitational redshift inferred from the absorption lines, as well as the averaged stellar mass density inferred from the orbital Keplerian frequency derived from the kilohertz quasi-periodic oscillation data. We apply the method to constrain the NS mass and radius of the X-ray sources, 1E 1207.4-5209, Aql X-1 and EXO 0748-676. © 2006 The Authors.