Measuring black-hole parameters and testing general relativity using gravitational-wave data from space-based interferometers

TL;DR

This paper presents a simplified model to analyze gravitational-wave signals from stellar captures by black holes, aiming to estimate black-hole parameters and test general relativity with space-based detectors like LISA.

Contribution

It introduces a straightforward model for gravitational waves from stellar captures, enabling parameter estimation and testing of strong-field gravity predictions.

Findings

Estimated black-hole mass and spin with high accuracy

Demonstrated potential to test general relativity in strong gravity regimes

Provided a framework for analyzing space-based gravitational-wave data

Abstract

Among the expected sources of gravitational waves for the Laser Interferometer Space Antenna (LISA) is the capture of solar-mass compact stars by massive black holes residing in galactic centers. We construct a simple model for such a capture, in which the compact star moves freely on a circular orbit in the equatorial plane of the massive black hole. We consider the gravitational waves emitted during the late stages of orbital evolution, shortly before the orbiting mass reaches the innermost stable circular orbit. We construct a simple model for the gravitational-wave signal, in which the phasing of the waves plays the dominant role. The signal's behavior depends on a number of parameters, including $\mu$, the mass of the orbiting star, $M$, the mass of the central black hole, and $J$, the black hole's angular momentum. We calculate, using our simplified model, and in the limit of large signal-to-noise ratio, the accuracy with which these quantities can be estimated during a gravitational-wave measurement. Our simplified model also suggests a method for experimentally testing the strong-field predictions of general relativity.