Date of Award:

5-2014

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Physics

Committee Chair(s)

Shane L. Larson

Committee

Shane L. Larson

Committee

Charles Torre

Committee

Todd Moon

Committee

Eric Held

Committee

Michael Taylor

Abstract

Gravitational waves are ripples in the fabric of spacetime that convey information about changing gravitational fields. Large-scale detection projects are currently in operation, and more advanced detectors are being designed and built. Though we have yet to make a direct detection of a gravitational wave signal, upgrades to current detectors are expected to bring the first detections within the next year or two.

Gravitational waves will bring us information about astrophysical phenomena that is complementary to the information gained from photon-based observations (e.g., telescopes and radio receivers). One of the primary sources of gravitational waves are binary systems: two massive objects that orbit around each other due to their mutual gravitational attraction. These systems can have very predictable gravitational wave signatures due to their repetitive motions, making them ideal gravitational wave sources.

In this dissertation, I present two research projects pertaining to gravitational wave astrophysics and compact binary systems. In the first, I explore interactions between compact binary systems near the center of our galaxy with the supermassive black hole that resides there. I am interested in the final state of the binary as a result of the interaction, ranging from small perturbations to the orbit up to total disruption. In the case of disruption, I characterize the new orbits formed between the binary components and the central black hole, known as extreme mass ratio inspirals. For binaries that survive the encounter, I examine the changes they experience, and find on average, they will merge together as a result of gravitational wave emission faster than before the encounter.

In the second project, I propose a new method of measuring the radius of the swirling disc of gas and dust that encircles some stars in compact binary systems, known as the accretion disc. This method relies on the use of coupled electromagnetic and gravitational wave observations, a synthesis of information known as multi-messenger astronomy. This new method proves very accurate when used on both simulated and observed data from a candidate system known as AM CVn.

The simulation codes written for this research are freely available at

  • https://github.com/ericaddison/Binary-SMBH-Encounter-Simulation
  • https://github.com/ericaddison/LightCurveSim

I also plan to post the codes to the Astrophysics code database Starship Asterisk (http://asterisk.apod.com/) once the corresponding papers are published.

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