Corner plot displaying the joint and marginal posterior distributions for the parameters of the astrometric solution for the CCO in G15.9+0.2. The astrometric calibration parameters {Δx_i, Δy_i, r_i, θ_i} have been marginalized over, and are not shown here in order to keep the figure uncluttered (see Table B.1 for constraints on all parameters). In the two-dimensional correlation plots, we indicate the 1σ, 2σ, and 3σ contours, meaning the smallest regions containing 39.3%, 86.5%, and 98.9% of the total probability mass, with solid lines. In the marginalized one-dimensional histograms, we indicate the median and 68% central interval of the posterior probability distribution, with dashed lines. The units of proper motion and the astrometric zero-point are mas yr⁻¹ and arcsec, respectively. This plot and analogous figures have been created using the corner.py package (Foreman-Mackey 2016).