Directionality and spectrum of the x-ray emission from a neutron star uniformly heated over its surface and with a strong magnetic field

Abstract

The spectral flux is calculated for x-ray emission from a rotating neutron star uniformly heated over its surface (T = 10 /sup 80/K) and having a strong dipolar magnetic field (B = 5 x 10/sup 12/ G at the pole). It is shown that because of the strong anisotropy of the local intensity and its dependence on the magnetic field, the flux in the photon energy interval E approx. 2-70 keV varies over time with the period of rotation, that is, a star such as this manifests itself as an x-ray pulsar. The amplitude of the variations and the shape of the brightness curves are strongly dependent on the energy. The spectrum of the flux contains two emission cyclotron features. Their position, like the shape of the continuum, depends on the phase of the rotation. The results obtained demonstrate the possibility of models or x-ray pulsars in which the radiating (hot) regions are not localized around the magnetic poles, but occupy a large part of the surface of a neutron star.