Date of Award

Summer 8-27-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Advisor(s)

Brown, Duncan A.

Subject Categories

Astrophysics and Astronomy | Physical Sciences and Mathematics

Abstract

Since making the first direct detection of gravitational waves in 2015, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) together with the Virgo observatory has detected an additional 51 confirmed signals from binary mergers. Two of these signals, GW170817 and GW190425, were identified as binary neutron star mergers. As detector sensitivity improves we expect to see many more binary neutron star merger events, both from future observing runs of the LIGO-Virgo network and from planned third-generation detectors. These new detections will provide an exquisite look at the nature of these systems and of neutron stars themselves. This thesis describes how gravitational-wave observations of neutron star mergers can be used to measure the properties of the binary systems and the fundamental physics of neutron stars. We use multimessenger observations of GW170817 to measure its viewing angle, which is important to understand the engine driving the electromagnetic counterpart to the gravitational-wave signal. We describe a new implementation of a fast likelihood model for gravitational-wave parameter estimation. We demonstrate that this likelihood allows analysis of binary neutron star signals to be performed quickly enough to inform strategies for electromagnetic follow-up observations. We measure the tidal deformabilities and radii of the neutron stars in GW170817, imposing a physical constraint to require that both neutron stars obey a common nuclear equation of state. We assess the future prospects for measuring the nuclear equation of state with the LIGO-Virgo network and with the planned third-generation detector, Cosmic Explorer.

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Open Access

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