Searching for Gravitational Waves from Compact Binary Coalescences in Advanced LIGO Data

Abstract

Advanced LIGO's first observing run marked the birth of gravitational-wave astronomy through the first detection of gravitational waves from coalescing black holes-GW150914. Advanced LIGO's second and Advanced Virgo's first observing run marked the birth of multimessenger astronomy with first joint observations of gravitational and electromagnetic radiation associated with coalescing neutron stars-GW170817. The electromagnetic observations included detection of a burst of gamma rays produced by the merger, and a kilonova powered by the radioactive decay of r-process nuclei synthesized in the neutron star coalescence ejecta. Gravitational waves from compact binary coalescences carry fingerprints of the sources that generated them. Studying them allows us to test Einstein’s general relativity in the strongest regimes, where it has never been tested before, and study matter at densities beyond reach of the most powerful laboratories on our planet. Moreover, we can gain insight about the evolution of stars, galaxies and even the Universe as a whole by studying the merger rate of compact objects. Joint electromagnetic and gravitational-wave observations help develop our understanding of the physical processes that occur in such systems, and provide a new method of probing cosmological parameters. GW170817 was detected by the GstLAL pipeline in low-latency making the extensive electromagnetic followup possible. The GstLAL pipeline is a matched filtering pipeline that uses compact binary coalescence waveform models to filter the data from gravitational-wave detectors in the time-domain. It can detect gravitational waves from coalescing compact binaries in near real time and provide point estimates for binary parameters. This thesis describes the methods, developments, and the results from the GstLAL pipeline over the course of the first two observing runs of Advanced LIGO, focusing on the contributions made by the author. We also present a study about the prospects of observing a cosmological stochastic background which is expected to be buried under the astrophysical background from the population of coalesceing compact binaries with third-generation gravitational-wave detectors.