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Experimental gravity with PSR B1534+12 Fonseca, Emmanuel

Abstract

We present an updated analysis of pulse profiles and their arrival-times from PSR B1534+12, a 37.9-ms pulsar that is orbiting a neutron star. Such “double-neutron-star” systems are expected to undergo various relativistic effects, such as orbital decay and precession, due to the strong-field nature of the local gravitational field (Damour & Taylor, 1992). A high-precision timing model is derived that accounts for all astrophysical processes that systematically affect pulse arrival-times. In the process of generating this model, we constrain parameters that characterize the interstellar environment, relative motion of the pulsar, its spin properties, and binary parameters. We measure five “post-Keplerian” parameters that represent relativistic corrections to the standard Keplerian quantities that describe a binary orbit. These relativistic parameters are then used to test general relativity by comparing the measured values with those predicted by Einstein’s grav- itational theory. We conclude that general relativity is confirmed to within ∼ 0.35% of its predictions. The measurement of orbital decay contains a bias due to relative acceleration in the Galactic potential, and cannot be corrected for at this time due to an unreliable measure of distance; however, we can use this bias as a means to constrain the distance the pulsar should be from Earth in order for general relativity to be the correct theory of gravity. We find this distance to be d_GR = 1.037 ± 0.012 kpc. We also present evidence for pulse “jitter” in PSR B1534+12, which indicates short-term magnetospheric activity and has significant implications for the long-term improvement of timing precision. In a separate study, we present an analysis on pulse-profile evolution that has been previously linked to relativistic spin precession (Stairs et al., 2004). The current results of our precession analysis cannot confirm general relativity using this relativistic effect, but future studies and observations are needed to constrain the precession rate of PSR B1534+12.

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