Gravitational-Wave Inference from Binary Compact Objects

Northwestern University, Evanston IL

Investigators

Abstract

This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. Gravitational waves offer a new tool for astronomy. First predicted by Einstein in 1916, their direct observation was only made possible a century later with the development of Advanced LIGO. Gravitational waves allow us to study some of the Universe's most extreme systems, such as the mergers of two black holes or neutron stars, which would otherwise remain hidden from us. In its first two observing runs, the Advanced LIGO detector network discovered gravitational waves from 10 binary black hole mergers and one binary neutron star merger. In future runs, the rate of detections will accelerate, with binaries being found every few days. These unique observations will enable us to answer long-standing questions in astrophysics like: What are masses of black holes? How are binaries of black holes and neutron stars made? How do massive stars explode and leave black hole or neutron star remains? Does the population of black holes change as the Universe evolves? What role do neutron star mergers play in forging heavy elements like gold? To answer these questions requires reliable and efficient techniques to analyse the rapidly growing collection of gravitational-wave data. The research supported by this grant supports the development of cutting edge statistical techniques to extract the information encoded in gravitational-wave data, and use this the unravel the central mysteries of black hole and neutron star binaries. Specifically, two main research objectives are targeted: (i) Inferring the physical parameters of merging binaries from gravitational-wave signals more efficiently (through improvements to sampling algorithms and through automation) and more accurately (accounting for realistic, non-stationary and non-Gaussian noise, and accounting for missing physics, such as eccentricity, in our current gravitational-wave models); (ii) Performing population inferences from the ensemble of the detections, using parametric and non-parametric models to reconstruct distributions of merging binaries (in terms of masses, spins and redshifts), and comparing results to astrophysical models to constrain the currently uncertain physics of binary evolution (such as common-envelope efficiency and supernova kicks). The inference tools developed will be made publicly available to enable the rapid advancement of gravitational-wave astronomy in the era of frequent detections. Furthermore, the latest results of gravitational-wave astronomy, and the excitement of multimessenger astronomy, will be communicated to diverse audiences through a range of outreach activities ranging from planetarium events to popular science writing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.