Abstract
To investigate a possible reason of the difference between the radio-quiet neutron stars and radio pulsars, we determined the possible ranges of magnetic inclination angle α and the observer's viewing angleζfor several radio-quiet neutron stars with X-ray thermal emission. With a given surface temperature distribution of a neutron star and assuming the surface emission is described by Plank function, we modeled light curves and spectra. Asαandζare parameters in our model, the possible range of these two angles for radio-quiet neutron stars can be inferred by comparing the computed flux and pulsed fraction with the observed ones. Our calculation included photon path bending and gravitational redshift. Our result shows no significant sign of the different distribution in the α-ζplane for radio-quiet neutron stars and radio pulsars. Besides, we discussed spectra and light curve behaviors due to the effect of gravity, temperature distribution and beaming effects (limb-darkening and magnetic beaming).