A supernova explosion of a massive star at the end of its life leaves behind a compact object, either a black hole or a neutron star. We study a particular aspect of neutron stars in this project. A neutron star is a fast spinning, extremely dense object with a strong magnetic field. Neutron stars can emit lightbeams from their magnetic poles. For an observer on earth these beams appear as pulses of light. These pulses of light are practically the only way to gather information about neutron stars. We use a model of a neutron star showing how the pulses of radiation would appear from Earth based on a set of chosen parameter values. These parameters contain information regarding the geometry of the neutron star, its mass and radius, as well as some properties related to the way the radiation is emitted. We also use a particle swarm optimization method to fit the simulated pulse to the observed light pulse of the x-ray emitting Centaurus X-3 (Cen X-3) binary system. This is done In order to retrieve information about Cen X-3. Our resulting fits do not converge to a single solution, rather it shows that there are many possible configurations leading to the observed light pulses. This shows that while our model can be used to simulate the behavior of neutron stars it requires further development if one wishes to obtain reliable parameter estimates.

This thesis concerns with the study of X-ray binaries which are gravitationally bound systems consisting of a compact object (either a neutron star or a black hole) and usually a non degenerate companion star, both rotating around the common centre of mass. The compact star shines brightly in the X-ray regime. Emission from these systems are powered by accretion which is the most radioactively efficient mechanism known in the universe by the release of gravitational potential energy when matter from the companion star falls on the compact object. Accretion onto high magnetic field neutron stars are special as the magnetic field plays a crucial role in governing the dynamics of gas flow and the flow of the matter close to the compact object. The radiation emitted from these systems are anisotropic and for a distant observer, the intensity is modulated at the spin period of the neutron star, hence these objects are called accretion powered pulsars. The angular pattern of the emitted radiation is also highly anisotropic and depends on the mass accreted and hence the luminosity. The beaming pattern commonly known as the pulse profiles exhibit a wide variety in the pulse shape and pulse fraction and vary with energy as well as intensity. They also exhibit cyclotron absorption features in their energy spectrum which are a direct probe to the magnetic field geometry of these systems. This thesis is dedicated to the study of the magnetic field and emission geometry of accretion powered pulsars through the pulse phase resolved studies of the cyclotron absorption features which are a direct probe of the magnetized plasma. In order to study these features in detail broadband continuum modeling of the energy spectrum is done, taking care of all other factors which may smear the pulse phase dependence. Another prerequisite for detailed continuum modeling is accounting for the low absorption dips in the pulse profiles of many these sources. The dips are presumably formed by phase locked accretion stream causing partial covering absorption when the stream is along our line of sight towards the emission region. Studying the pulse phase dependence of this partial covering absorber also provides us with important clues on the local environment of the neutron star and the structure of the accretion stream. All of these studies are performed with data from the broadband and most sensitive instruments onboard the Japanese satellite Suzuki. Lastly we provide estimates of the polarization expected to be detected from these sources by a Thomson scattering polarimeter being developed to observe the polarization of X-rays in the energy range of 5--30 keV. Along with the X-ray pulsars, we also make an estimate of the likelihood of detection of X-ray polarization from black hole X-ray binaries in different spectral states. This is a particularly interesting topic as it will play a crucial role in providing additional handles on the magnetic field geometry in accretion powered pulsars as well as constrain the fundamental parameters of a black hole like its spin.