Presentation description

Omega Centauri (ω Cen) is a large globular cluster in the Milky Way visible in the southern sky. It is likely the remnant nucleus of a dwarf galaxy disrupted by the Milky Way, making ω Cen a valuable target for studying both globular cluster dynamics and the evolution of dwarf galaxies. To understand a globular cluster's dynamics, the fraction and spatial distribution of stars found in binary systems is crucial, as the gravitational energy stored in these binary systems drives the cluster's dynamics and structure. Previous studies have estimated the binary fraction of ω Cen by counting the number of binary systems detected using either photometric measurements or radial velocity time series data. However, photometric measurements cannot detect binary systems where the star's companion is dark or very faint (e.g., a black hole), and radial velocity data shows at most a faint signal for binary systems with a face-on orbit (low inclination) or a long orbital period. Another method to detect binary systems is through a star's 2D astrometry. Astrometry can show a strong signal in binary systems with a dark companion, high inclination, or a long orbital period, making it a valuable complement to the other two methods. However, to date, astrometry has not been used in a systematic search for binary systems in ω Cen. In this study, we present a new periodogram-based process for systematically searching for binary systems using 2D astrometry. We generate synthetic data to test the completeness and precision of this detection process and show that it is robust for the systems we expect to detect. We plan to apply this to astrometry from 20 years of Hubble Space Telescope observations of the center of ω Cen to make an independent measurement of the cluster's binary fraction and distribution, and potentially probe the cluster's black hole retention fraction.