Dips in the pulse profiles of accretion powered pulsars

We report detection of sharp dips in the pulse profiles of several persistent and transient accretion powered X-ray pulsars using RXTE observations. The pulse profiles of accretion powered pulsars carry a lot of information regarding the radiative processes near the surface of the star, magnetic fields that channel the accretion flow etc. The dips in the pulse profiles can be due to the interaction of accretion column with the emitting radiation as it passes through the line of sight. We have also investigated the energy and intensity dependence and phase width of these dips to have a better understanding of the nature of the absorbing material. Any intensity dependence of the pulse phase of the dips will also reveal the nature of the absorbing structure in relation to the neutron star.