χ² as function of a and e for orbit models that are not necessarily coplanar with the circumbinary disk (Sect. 3.2). As in Fig. 2, the minimum χ² is marked by the cross, but the contour line around it encircles the 68.3% confidence region (1σ). The areas in shades of gray are within the 5σ confidence region. The jagged shape of the contour line is most likely caused by numerical effects.