Degree

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

Document Type

Dissertation

Abstract

The existence of gravitational waves is predicted by Albert Einstein's Theory of General Relativity. Commonly referred to as "ripples in spacetime", these waves are generated by some of the most violent and energetic processes in the universe. Despite their theoretical prediction over a century ago, it wasn't until 2015 that the Advanced LIGO (aLIGO) interferometers in Hanford, WA and Livingston, LA directly detected gravitational waves for the first time, confirming Einstein's theory and ushering in a new era of astrophysics.

Detecting gravitational waves requires incredible precision. Because of the extreme sensitivity required, it is possible for the gravitational wave data to be contaminated by environmental and instrumental noise. For this reason, characterizing noise that can reduce the sensitivity, and therefore the astrophysical reach, of the detectors is very important. The focus of this dissertation is on characterizing and mitigating transient noise during the aLIGO third and fourth observing runs (O3 and O4, respectively).

First, I discuss monitoring the physical environment around the Livingston detector, and how intentionally injecting noise into various parts of the detector tells us about the detector's response to external disturbances, and how noise couples to it. Next, I studied the output of the tool Gravity Spy, which classifies transient noise based on its morphology in the main gravitational wave data channel. Finally, I discuss another study that dives into characterizing and mitigating noise due to a type of light scattering, called Fast Scatter, by studying seismic motion due to trains. In O3, Fast Scatter was the most common transient noise source at Livingston, which is correlated with increases in ground motion in the 1-6 Hz frequency band. Fast Scatter impacted the gravitational wave sensitivity from 10-100 Hz, which is where we are the most sensitive to the mergers of high mass binary black holes. This work identified a location at LLO and which narrow-band seismic frequencies due to trains contributed to increased Fast Scatter noise.

Date

3-27-2024

Committee Chair

Gonzalez, Gabriela

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