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AR 17034 (Archival Research)

Wed Jul 17 17:20:28 GMT 2024

Principal Investigator: Abhimat Gautam
PI Institution: University of California - Los Angeles
Investigators (xml)

Title: Photometric search for Black Hole-Star Binaries in the Milky Way Galactic center
Cycle: 30

Abstract
Galactic nuclei have been proposed to produce the types of binary black hole mergers that have recently been detected by gravitational wave observatories. Tight black hole-star binary systems are likely precursors to these mergers. However, the number of tight black hole-star binaries in galactic nuclei is not yet well constrained. The Milky Way Galactic center, being the only Galactic nucleus with individually resolvable stars, allows constraining the presence of black hole-star binary systems in galactic nuclei and evaluating if they indeed are likely factories of binary black hole mergers observed with gravitational waves. We propose to use 9.7 years of archival HST-WFC3IR observations of the central 5 parsecs of the Galactic center to photometrically search for and characterize stellar-mass black holes in close binary systems. We will use the multi-epoch observations to search for variability consistent with ellipsoidal effects and Doppler beaming expected in close binary systems with compact components. Using preliminary simulations based on the binary fraction and stellar-mass black hole production rates for the young and old stellar populations of the Galactic center, we predict that our experiment should detect 1 to 6 close binary systems possesing stellar-mass black holes. In detected systems, we will model the flux variability to constrain compact object masses. Our proposed experiment can detect stellar-mass black holes in detached binary systems at the Galactic center, and constrain the viability of galactic nuclei to produce the recent binary black hole mergers observed by gravitational wave observatories.