Internal kinematics of GAIA eDR3 wide binaries

Using the recent GAIA eDR3 catalogue we construct a sample of solar neighbourhood isolated wide binaries satisfying a series of strict signal-to-noise data cuts, exclusion of random association criteria and detailed colour-magnitude diagram selections, to minimise the presence of any kinematic contaminating effects having been discussed in the literature to date. Our final high-purity sample consists of 421 binary pairs within 130 pc of the sun and in all cases high-quality GAIA single-stellar fits for both components of each binary (final average RUWE values of 0.99), both also restricted to the cleanest region of the main sequence. We find kinematics fully consistent with Newtonian expectations for separations, $s$, below 0.009 pc, with relative velocities scaling with $\Delta V \propto s^{-1/2}$ and a total binary mass, $M_{b}$, velocity scaling of $\Delta V \propto M_{b}^{1/2}$. For the separation region of $s> 0.009$ pc we obtain significantly different results, with a separation independent $\Delta V \approx 0.5$ km/s and a $\Delta V \propto M_{b}^{0.22 \pm 0.18}$. This situation is highly reminiscent of the low acceleration galactic baryonic Tully-Fisher phenomenology, and indeed, the change from the two regimes we find closely corresponds to the $a \lesssim a_{0}$ transition.