Test and application of gravitational theories in astronomical systems
Abstract
The motivation of our analysis is to put constraints, beyond making them unlikely, on a variety of Newtonian perturbations that could conspire to imitate the timing effects of the relativistic two-body model. This will provide an assessment on the quality of the evidence that the decay of the pulsar's orbital period is caused by the energy loss of the binary pulsar system in the form of gravitational radiation. A timing model for the binary pulsar system PSR 1913+16 which includes both relativistic timing effects and the effects of conceivable rotational and tidal distortions of the pulsar's companion star was developed. The deformation of the companion star would modify its Newtonian gravitational field which affects the orbit of the pulsar. In addition to secular perturbations discussed in previous work our analysis calculated the periodic perturbations that occur at harmonics of the pulsar's orbital period. These characteristic periodic effects can generally indicate distinctively the presence of rotational and tidal distortions of the pulsar's companion star. Our analysis shows that the timing effect of the gravitational red shift and second order Doppler shift and the effect of the Shapiro propagation delay of the pulse can be isolated from all these effects. They can be used to obtain a reliable estimate of the masses of the pulsar and its companion star whatever the nature of the companion. This new constraint can rule out any possibility that the pulsar's companion is a helium star and it sharply constrains the rotational distortion of a conceivable white dwarf companion. Another subject of this thesis concerns with the deflection of star light by the gravitational field of the sun. The gravitational field generated by currents of matter within a body influences the deflection of light by the body. We show that in metric theories of gravity the Einstein equivalence principle implies a deeper connection than had been realized between this deflection and the Lense-Thirring dragging of inertial frames. (Abstract shortened with permission of author.)
Degree
Ph.D.
Advisors
Haugan, Purdue University.
Subject Area
Astronomy|Astrophysics
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