#### Date of Award:

5-1-2014

#### Document Type:

Dissertation

#### Degree Name:

Doctor of Philosophy (PhD)

#### Department:

Physics

#### Advisor/Chair:

Shane L. Larson

#### Abstract

In this dissertation, I present two studies in the field of gravitational wave astrophysics applied to compact binary systems. In the first project, I investigate simulated encounters between a binary system comprised of two stellar mass black holes with a galactic supermassive black hole. It is found that binaries disrupted by the supermassive black hole form extreme mass ratio inspirals (EMRIs), which would begin with very high eccentricity, e ≈ 1 − O(10−2), but circularize dramatically by the emission of gravitational wave radiation. At the time when the stable orbit turns over to a plunge orbit, the EMRIs still have some small residual eccentricity, e ≈ 0.05 on average, which is slightly larger than previous estimates. The surviving binaries are classified based on their final relation with the supermassive black hole. When inspecting the merger lifetime of the surviving binaries, a mean new merger lifetime of ˜ T = 0.8T0 is found. Factoring in this new lifetime with other relevant data, I calculate the merger rate of these systems in the range of the advanced Laser Interferometer Gravitational Wave Observatory to be about 0.25 yr−1, which represents a small percentage of the current predicted CBC rates. In the second project I propose and explore a new method of estimating the radius of the accretion disc in cataclysmic variable binary systems though the use of coupled electromagnetic and gravitational wave observations. By identifying the angle of the hot spot formed by the impact of the accretion stream with the disc, φHS, the radius of the disc can be recovered. I test the proposed method against fully simulated lightcurve output, as well as the true observed AM CVn lightcurve. In both cases, I find our method capable of estimating the disc radius to high precision. I calculate a disc radius of ˆRD/a ≈ 0.476°”0.025 for the fully simulated data and ˆRD/a ≈ 0.481 °” 0.05 for the true lightcurve data. These estimates agree with the accepted value of RD = 0.478a within the uncertainties, and differ from the accepted value by 0.4% and 0.6%, respectively. Because this method does not rely on eclipses, it will be applicable to a much broader population of binaries.

#### Recommended Citation

Addison, Eric, "Gravitational Wave Astrophysics with Compact Binary Systems" (2014). *All Graduate Theses and Dissertations.* Paper 2166.

http://digitalcommons.usu.edu/etd/2166

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