R.A. and decl. residuals for the GRAVITY observations of β Pictoris b and c with respect to our best-fit “two-planet” model. Purple points and associated error bars mark the GRAVITY astrometric measurements, with uncertainties inflated by the best-fit error-scaling parameter. The top row presents the residuals for β Pictoris b, while the bottom row displays the corresponding residuals for β Pictoris c. The gray lines represent 1000 randomly selected posterior draws from our “two-planet and moon” fit. We see no correlated residuals to the “two-planet” model, indicative of an unmodeled signal, and we see no coherent pattern to the posterior draws for planet b, which includes hypothetical lunar perturbations. We note that the posterior samples of β Pic c show some evidence for bimodality due to the relatively sparse sampling of the planet’s orbit with GRAVITY.