Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[width=7.7cm,clip]{2476fig1.eps} % \end{figure}$ Figure 1: Reduced $\chi ^2$ ( $\chi ^2/{\rm d.o.f.}$ ) as a function of the stellar inclination i computed from all interferometric observations described in Sect. 2 for the two test models (radiative and convective limits for the gravity-darkening). These values correspond to the best equatorial angular diameter $\oslash _{\rm eq}$ and major axis orientation $\eta$ for a given i. Models with $\beta =0.25$ (solid curve) are preferred compared to models with $\beta =0.08$ (dashed curve). The minimum $\chi ^2/{\rm d.o.f.}$ ( $\chi ^2_{\rm min}/{\rm d.o.f.}=7.3$ ) is obtained for $\beta =0.25$ and $i=55\hbox {$^\circ $ }$ . Further physical parameters for this best model from all data (BMAD) and the corresponding error bars are given in Table 3, together with the results of other $\chi ^2$ analyses.
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In the text

$\begin{figure} \par\mbox{\hspace*{1.5cm}\small {$V^2$\space at 30 m}\hspace*{4.1... ...2b.eps}} \resizebox{5.21cm}{!}{\includegraphics*{2476fig2c.eps}} } \end{figure}$ Figure 2: Squared visibilities V² and corresponding errors versus the wavelength for the seven NPOI scans (see Sect. 2). Solid curves correspond to theoretical values obtained from our best model from the $\chi ^2$ analysis of all interferometric data (BMAD; see also Fig. 1). Plots for scans 2 to 7 were progressively shifted for better visualization.
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In the text

$\begin{figure} \resizebox{16cm}{!}{\includegraphics*{2476fig3.eps}} \end{figure}$ Figure 3: Triple amplitudes $\left \vert V_1\right \vert\left \vert V_2\right \vert\left \vert V_3\right \vert$ , closure phases $\phi _1+\phi _2+\phi _3$ , and corresponding errors versus the wavelength for the seven NPOI scans (Sect. 2). Solid curves correspond to theoretical values obtained from our best model from the $\chi ^2$ analysis of all interferometric data (BMAD; see also Fig. 1). The closure phase is very sensitive to the stellar intensity distribution. Therefore, a comparison between a strong ( $\beta =0.25$ ; solid curves) and a weak ( $\beta =0.08$ ; dashed curves) gravity-darkened model shows that a highly non-uniform surface brightness distribution is mandatory to reproduce the observed closure phases. Note that the closure phases have small error bars ( $\protect\la$ 0.03 rad). Plots for scans 2 to 7 were progressively shifted for better visualization. The picture in the right is the effective temperature map for the BMAD (Table 3).
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In the text

$\begin{figure} \par\includegraphics*[width=12.5cm,clip]{2476fig4.eps} % \end{figure}$ Figure 4: Squared visibilities V² (triangles) and corresponding error bars from VLTI-VINCI (H and K bands) and PTI (K band; baselines 85 m and 110 m) as described in Sect. 2. The abscissa is an index (integer number) to label each group of V² data. The crosses correspond to theoretical V² obtained from the model with minimum $\chi ^2$ (best model; cf. Fig. 1). The abscissas of the V² data are slightly shifted to the right compared to those of the theoretical V² for better visualization.
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In the text

$\begin{figure} \resizebox{17cm}{!}{\includegraphics{2476fig5.eps}}\end{figure}$ Figure 5: The left panel shows the closure phases $\phi _1+\phi _2+\phi _3$ and corresponding errors versus the wavelength for the seven NPOI scans (Sect. 2). Solid curves correspond to theoretical values obtained from our best model from the $\chi ^2$ analysis of closure phases alone (BMCP; see Table 3). Dashed curves correspond to the theoretical closure phases obtained by fixing $i=50\hbox {$^\circ $ }$ , $\oslash _{\rm eq}=3.44$ mas, and $\eta =113\hbox {$^\circ $ }$ . These parameters were derived from the $\chi ^2$ analysis of near-IR V² alone (BMIR). The solid curves provide a much better fit to the observed closure phases because they correspond to an angular equatorial diameter larger ( $\oslash _{\rm eq}=3.88$ mas) than the value for the dashed curves ( $\oslash _{\rm eq}=3.44$ mas). On the other hand, a model (BMIR) with $\oslash _{\rm eq}=3.44$ mas nicely fits the near-IR V² as shown in the right panel (see also Fig. 4).
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In the text

$\begin{figure} \par\mbox{\hspace{1.5cm}\small {$V^2$\space at 30 m}\hspace{4.1... ...2b.eps}} \resizebox{5.21cm}{!}{\includegraphics*{2476fig2c.eps}} } \end{figure}$	Figure 2: Squared visibilities V² and corresponding errors versus the wavelength for the seven NPOI scans (see Sect. 2). Solid curves correspond to theoretical values obtained from our best model from the $\chi ^2$ analysis of all interferometric data (BMAD; see also Fig. 1). Plots for scans 2 to 7 were progressively shifted for better visualization.
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