INCLUDING THE EFFECT OF GRAVITATIONAL LIGHT BENDING IN X-RAY PROFILE MODELING

The purpose of this work is to generalize pulse shape modelling to inc lude the effect of light bending due to general relativity. A simple a nalytical formula is found to describe the light-bending effect accura tely, and is incorporated into the emission model for calculation of t he pulse shapes from rotating accreting neutron stars. Least-squares f ittings are performed to a subset of pulsars studied by Leahy. The fit tings with light bending show significant improvement over the fitting s without light bending, and the resulting derived emission region geo metry gives narrower rings, as expected on theoretical grounds. The mo del is also applied to the transient pulsar EXO 2030 + 375. The relati on between the luminosity and the properties of the emission rings is studied. For this pulsar we conclude that some effect other than chang ing emission ring size is responsible for the change in pulse shape.