A new line on the wide binary test of gravity

Abstract

The relative velocity distribution of wide binary (WB) stars is sensitive to the law of gravity at the low accelerations typical of galactic outskirts. I consider the feasibility of this wide binary test using the `line velocity' method. This involves considering only the velocity components along the direction within the sky plane orthogonal to the systemic proper motion of each WB. I apply this technique to the WB sample of Hernandez et. al. (2019), carefully accounting for large-angle effects at one order beyond leading. Based on Monte Carlo trials, the uncertainty in the one-dimensional velocity dispersion is $\approx 100$ m/s when using sky-projected relative velocities. Using line velocities reduces this to $\approx 30$ m/s because these are much less affected by distance uncertainties. My analysis does not support the Hernandez et. al. (2019) claim of a clear departure from Newtonian dynamics beyond a radius of $\approx 10$ kAU, partly because I use $2\sigma$ outlier rejection to clean their sample first. Nonetheless, the uncertainties are small enough that existing WB data are nearly sufficient to distinguish Newtonian dynamics from Modified Newtonian Dynamics. I estimate that $\approx 1000$ WB systems will be required for this purpose if using only line velocities. In addition to a larger sample, it will also be important to control for systematics like undetected companions and moving groups. This could be done statistically. The contamination can be minimized by considering a narrow theoretically motivated range of parameters and focusing on how different theories predict different proportions of WBs in this region.

14 pages, 9 figures, 1 table. Accepted for publication in the Monthly Notices of the Royal Astronomical Society in this form

References in corpus (22)

• Primordial Black Holes as Dark Matter
• Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds
• SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
• The Radial Acceleration Relation in Rotationally Supported Galaxies
• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• Proxima's orbit around Alpha Centauri
• Current status of direct dark matter detection experiments
• A Novel Test of the Modified Newtonian Dynamics with Gas Rich Galaxies
• Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation
• New Distant Companions to Known Nearby Stars. II. Faint companions of Hipparcos stars and the frequency of wide binary systems
• A statistical investigation of the mass discrepancy-acceleration relation
• Limits on the Mass and Abundance of Primordial Black Holes from Quasar Gravitational Microlensing
• The scatter, residual correlations and curvature of the SPARC baryonic Tully-Fisher relation
• Close stellar conjunctions of alpha Centauri A and B until 2050 - An mK = 7.8 star may enter the Einstein ring of alpha Cen A in 2028
• Test of Einstein equivalence principle near the Galactic center supermassive black hole
• MOND as a regime of quantum gravity
• Constraints on the dynamical evolution of the galaxy group M81
• Being WISE II: Reducing the Influence of Star Formation History on the Mass-to-Light Ratio of Quiescent Galaxies
• Was Proxima captured by alpha Centauri A and B?
• Evidences for Collisional Dark Matter In Galaxies?
• Directly testing gravity with Proxima Centauri
• The imprint of the MOND external field effect on the Oort cloud comets aphelia distribution

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• Effect of the Solar dark matter wake on planets
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