Studies of Strong-Gravity Binaries and Their Gravitational Waves

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

This award will support and extend this group's ongoing research on the dynamics of binary systems in general relativity, and research on astronomy with gravitational wave observations. This work will further our understanding of how black holes in binary systems interact with one another, and will develop tools for understanding the signals that are now being measured using the LIGO gravitational-wave detectors, and using sister instruments coming on line on the Earth's surface and planned space-based detectors. In particular, this group will continue work on an approximation to General Relativity known as "effective one body" (EOB) that simplifies the modeling of binary systems and other perturbative frameworks used to describe the black hole event horizon. These techniques complement those used when looking for full numerical solutions of the Einstein equations. They will continue to produce sonifications of gravitational wave signals, a tool which has proven to powerfully illustrate how gravitational waves encode source information. Additionally, the PI will make online tools to explore black hole orbits, with accompanying videos illustrating the strong-field nature of orbits which produce interesting gravitational-wave signals. The specific projects that will be pursued in this time frame will be a mix of studies using black hole perturbation theory, and studies in support of astronomy with the LIGO gravitational wave detectors. The PI's group will use black hole perturbation theory in collaboration with colleagues at the Albert Einstein Institute to revise and extend the very successful EOB approach to compact binary dynamics. Work in this program so far has done much to clarify how interactions with a black hole's event horizon affect the evolution of compact binaries. Ongoing work is now probing orbits with substantial spin-orbit misalignment, laying the groundwork for using the EOB framework on a larger family of astrophysically relevant orbits. The group will also use black hole perturbation theory as the foundation for understanding self forces, computing how a body deforms the spacetime in which it moves and how that deformation acts back upon the body's motion. In the domain of gravitational wave astronomy, they have begun a systematic investigation into how black hole modes are excited in the final merger of two black holes. This analysis will allow us to understand how the mixture of modes excited by black holes mergers depends upon the collision geometry and characteristics of the merging black holes. The analysis will also make it possible to learn more about the characteristics of the merging black holes from the gravitational waves that we measure.