1. Measurements of the Low-acceleration Gravitational Anomaly from the Normalized Velocity Profile of Gaia Wide Binary Stars and Statistical Testing of Newtonian and Milgromian Theories
- Author
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Kyu-Hyun Chae
- Subjects
Gravitation ,Wide binary stars ,Modified Newtonian dynamics ,Non-standard theories of gravity ,Binary stars ,Astrophysics ,QB460-466 - Abstract
Low-acceleration gravitational anomaly is investigated with a new method of exploiting the normalized velocity profile $\tilde{v}\equiv {v}_{p}/{v}_{c}$ of wide binary stars as a function of the normalized sky-projected radius s / r _M , where v _p is the sky-projected relative velocity between the pair, v _c is the Newtonian circular velocity at the sky-projected separation s , and r _M is the MOND radius. With a Monte Carlo method, Gaia observed binaries and their virtual Newtonian counterparts are probabilistically distributed on the s / r _M versus $\tilde{v}$ plane, and a logarithmic velocity ratio parameter Γ is measured in the bins of s / r _M . With three samples of binaries covering a broad range in size, data quality, and implied fraction of hierarchical systems including a new sample of 6389 binaries selected with accurate distances and radial velocities, I find a unanimous systematic variation from the Newtonian flat line. With Γ = 0 at s / r _M ≲ 0.15 or s ≲ 1 kau, I get Γ = 0.068 ± 0.015 (stat) ${}_{-0.015}^{+0.024}$ (syst) for s / r _M ≳ 0.7 or s ≳ 5 kau. The gravitational anomaly (i.e., acceleration boost) factor given by γ _g = 10 ^2Γ is measured to be ${\gamma }_{g}={1.37}_{-0.09}^{+0.10}$ (stat) ${}_{-0.09}^{+0.16}$ (syst). With a reduced χ ^2 test of Newtonian and Milgromian nonrelativistic theories, I find that Newtonian gravity is ruled out at 5.8 σ ( ${\chi }_{\nu }^{2}=9.4$ ) by the new sample (and 9.2 σ by the largest sample used). The Milgromian AQUAL theory is acceptable with $0.7\lesssim {\chi }_{\nu }^{2}\lesssim 3.1$ . These results agree well with earlier results with the “acceleration-plane analysis” for a variety of samples and the “stacked velocity profile analysis” for a pure binary sample.
- Published
- 2024
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