English: Astrometric orbit of HD81040 (left panel) as determined by Gaia. North is up and East is left. The sky-projected orbit model about the system barycentre marked with an "x" is shown in grey and astrometric normal-points after subtraction of parallax and proper motion are shown in black. Only one-dimensional ("along-scan") astrometry was used, therefore the shown offsets are projected along Gaia's instantaneous scan angle, whose orientation is also indicated by the error-bars. The star's modelled parallax and proper motion is shown in the top-right panel by the solid curve, where open circles indicate the times when the star crossed the Gaia field-of-view. The arrow indicates the direction of motion. The bottom right panel shows the post-fit residual normal-points, whose small root-mean-square disperson of 65 micro-arcsecond indicates that the chosen astrometric model reproduces the data well. Normal-points are computed at every field-of-view transit of the star from the ~9 individual CCD transits and are only used for visualisation, whereas the data processing uses individual CCD-transit data. The solution parameters and their uncertainties are shown by insets on the very left and in the top right panel.