AMBER (LR-HK) squared visibilities as a function of the spatial frequency. The legend denotes the epoch and the position angle (PA) of the baseline of the observation. All 2007 and 2008 data have a similar PA because the same co-linear baseline configuration was used. Per baseline, the H and K band are separated by the HK-discontinuity, but still show a smooth transition between the two.

Same as Fig. 3 but for K band (for which there are no IOTA data). The red model is not relevant in K and is not shown.

All NPOI visibilities, except the 673 nm channel which is shown in Fig. 5. A different wavelength is shown in each panel, as indicated. The symbols correspond to different physical baselines, plusses for AC0-AE0 and crosses for AE0-AW0. The blue, green and red lines are the same star+ring models as in Fig. 5, and have ring diameters and widths of (5.5, 1.0), (3.0, 3.0) and (1.0, 4.5) respectively. The red filled circles correspond to the best binary model deduced in Sect. 3.2 and online Fig. 7.

map of the relative position of the secondary component with respect to the primary at the center, if a binary model is applied to fit the optical NPOI visibilities.

map of the position x versus y of the post-AGB star with respect to the phase reference defined by the ring (inner diameter 3 mas and width 4.6 mas, see Sect. 3.4).

Left: CI of T_eff versus E(B − V), right: CI of T_eff versus angular diameter θ_⋆ (mas), for the stellar SED fit.