More Wide Binary Data

A paper looking at new data sees a MOND effect in wide binary stars. The discussion engages with possible sources of noise or bias in the results that have been proposed in connection with earlier wide binary data, and finds those hypotheses to be implausible at best.

The Gaia eDR3 catalogue has recently been used to construct samples of nearby wide binaries to study the internal kinematics of these objects using relative velocities of the two component stars, ΔV, total binary masses, mB, and separations, s. For s≳0.035 pc, these binaries probe the low acceleration a<a(0) regime over which the gravitational anomalies usually attributed to dark matter are observed in the flat rotation curves of spiral galaxies, where a(0)≈1.2×10^10 is the acceleration scale of MOND. 

Such experiments test the degree of generality of these anomalies, by exploring the same acceleration regime using independent astronomical systems of vastly smaller mass and size. A signal above Newtonian expectations has been observed when a<a(0), alternatively interpreted as evidence of a modification in the relevant fundamental physics, or as being due to kinematic contaminants affecting the experiment; the presence of undetected stellar components, unbound encounters and spurious projection effects. 

Here I take advantage of the enhanced DR3 Gaia catalogue to perform a more rigorous and detailed study of the internal kinematics of wide binaries than what has previously been possible. Having internally determined accurate Gaia stellar masses and estimates of binary probabilities for each star using spectroscopic information, together with a larger sample of radial velocities, allows for a significant improvement in the analysis of wide binaries and careful exclusion of possible kinematic contaminants. Resulting ΔV vs. s and ΔV vs. mB scalings accurately tracing Newtonian expectations for the high acceleration regime, but consistent with the distance and mass velocity scalings observed in spiral galaxies in the low acceleration one, are obtained.

X. Hernandez, "Internal kinematics of GAIA DR3 wide binaries: anomalous behaviour in the low acceleration regime" arXiv:2304.07322 (April 14, 2023).