2025/12/22 by Serat Mahmud Saad, Yuan-Sen Ting, Saad, Serat Mahmud +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Pulsars and Gravitational Waves Research #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · doi:10.48550/arxiv.2512.19652
openalex publication_date 2025/12/22 · openalex created_date 2025/12/24 · openalex updated_date 2026/07/28
Wide-binary stars, separated by thousands of AU, reside in low-acceleration regimes where Modified Newtonian Dynamics (MOND) predicts deviation from Newtonian gravity. However, Gaia radial velocities (RVs) lack the precision to resolve the small velocity differences expected in these systems, limiting previous MOND analyses to two-dimensional kinematics. In this paper, we introduce a technique to measure differential RVs of wide binary stars using high resolution, high signal-to-noise spectra. We apply this method to measure differential RVs of 100 wide-binaries from the C3PO survey and achieved precisions of 8-15 m/s per binary pair, a ∼ 10-100 × improvement (median ∼ 24 ×) over Gaia DR3. Combining these measurements with Gaia astrometry, we construct a hierarchical Bayesian model to infer the orbital elements of all wide-binary pairs and the global MOND acceleration scale (a0). We test two commonly used interpolating functions in MOND formulation: the simple form (b=1, μ= x/(1+x)) and the standard form (b=2, μ= x/√(1+x2)). Our results indicate tension with MOND at the presently accepted a0 value: for b=1, the canonical value is excluded at 3.1σ, while for b=2, the exclusion is at 1.9σ.