Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f1.eps}\end{figure}$ Figure 1: Wavelets power spectral density (PSD) of a processed series of 418 interferograms obtained on $\alpha$ Cen A, before (thin line) and after (thick line) recentering of the fringe peak and subtraction of the background noise (dashed line).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f2.eps} \end{figure}$ Figure 2: Model PSD of $\alpha$ Cen A fringes for a zero baseline, including the spectrum of the star, atmosphere, fluoride glass fibers, K band filter, detector quantum efficiency and the correction function $F_1(\lambda )$ (see Sect. 3.3). A total precipitable water vapor of 3.0 mm (median for Paranal) is assumed for this plot. The curve for $\alpha$ Cen B is almost identical.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f3.eps} \end{figure}$ Figure 3: Model (black line) and observed (grey line) PSDs of $\alpha$ Cen A fringes on the 66m baseline (61 m projected). The visibility loss for larger wavenumbers is clearly visible. The observed Fourier PSD, smoothed by the differential piston, shows the expected asymmetry. The on-sky and model vertical scales are arbitrary.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f4.eps} \end{figure}$ Figure 4: Model (black line) and observed (grey line) PSDs of $\alpha$ Cen B fringes on the E0-G1 baseline. $\alpha$ Cen B being significantly less resolved than A, the squared visibility is more uniform over the K band than for $\alpha$ Cen A (Fig. 3). The asymmetry of the power spectrum is therefore smaller, though still present. The on-sky and model vertical scales are arbitrary.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{ms3494f5.eps} \end{figure}$ Figure 5: Detail of $\theta$ Cen squared visibilities and uniform disk model. The continuous line is the UD diameter fit (5.305 $\pm$ 0.020 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{figure6.eps} % \end{figure}$ Figure 6: Overview of the $\alpha$ Cen and $\theta$ Cen squared visibilities and UD models. From bottom to top: $\alpha$ Cen A, $\alpha$ Cen B and $\theta$ Cen (primary calibrator). The angular diameter of $\theta$ Cen was measured using 58 Hya as secondary calibrator.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f7.eps} \end{figure}$ Figure 7: Detail of $\alpha$ Cen A squared visibility. The continuous line is the uniform disk diameter fit (8.314 $\pm$ 0.016 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain. The visibility curve never goes to zero due to the bandwidth smearing effect.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f8.eps} \end{figure}$ Figure 8: Detail of $\alpha$ Cen B squared visibility. The continuous line is the uniform disk diameter fit (5.856 $\pm$ 0.027 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{ms3494f9.eps} \end{figure}$ Figure 9: Intensity profile of $\alpha$ Cen A from the four-parameters limb darkening law of Claret (2000) (dashed line) and the corresponding $\alpha = 0.1417$ power law.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{ms3494hr.eps} \end{figure}$ Figure 10: HR diagram of $\alpha$ Cen B. The line on the right corresponds to a mixing length of $\lambda =0.96$ and a mass of 0.909 $M_{\odot }$ , the line on the left corresponds to the values published in Thévenin et al. 2002 ( $\lambda =0.98$ , 0.907 $M_{\odot }$ ).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f1.eps}\end{figure}$	Figure 1: Wavelets power spectral density (PSD) of a processed series of 418 interferograms obtained on $\alpha$ Cen A, before (thin line) and after (thick line) recentering of the fringe peak and subtraction of the background noise (dashed line).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f2.eps} \end{figure}$	Figure 2: Model PSD of $\alpha$ Cen A fringes for a zero baseline, including the spectrum of the star, atmosphere, fluoride glass fibers, K band filter, detector quantum efficiency and the correction function $F_1(\lambda )$ (see Sect. 3.3). A total precipitable water vapor of 3.0 mm (median for Paranal) is assumed for this plot. The curve for $\alpha$ Cen B is almost identical.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f3.eps} \end{figure}$	Figure 3: Model (black line) and observed (grey line) PSDs of $\alpha$ Cen A fringes on the 66m baseline (61 m projected). The visibility loss for larger wavenumbers is clearly visible. The observed Fourier PSD, smoothed by the differential piston, shows the expected asymmetry. The on-sky and model vertical scales are arbitrary.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms3494f4.eps} \end{figure}$	Figure 4: Model (black line) and observed (grey line) PSDs of $\alpha$ Cen B fringes on the E0-G1 baseline. $\alpha$ Cen B being significantly less resolved than A, the squared visibility is more uniform over the K band than for $\alpha$ Cen A (Fig. 3). The asymmetry of the power spectrum is therefore smaller, though still present. The on-sky and model vertical scales are arbitrary.
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$\begin{figure} \par\includegraphics[width=8.2cm,clip]{ms3494f5.eps} \end{figure}$	Figure 5: Detail of $\theta$ Cen squared visibilities and uniform disk model. The continuous line is the UD diameter fit (5.305 $\pm$ 0.020 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{figure6.eps} % \end{figure}$	Figure 6: Overview of the $\alpha$ Cen and $\theta$ Cen squared visibilities and UD models. From bottom to top: $\alpha$ Cen A, $\alpha$ Cen B and $\theta$ Cen (primary calibrator). The angular diameter of $\theta$ Cen was measured using 58 Hya as secondary calibrator.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f7.eps} \end{figure}$	Figure 7: Detail of $\alpha$ Cen A squared visibility. The continuous line is the uniform disk diameter fit (8.314 $\pm$ 0.016 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain. The visibility curve never goes to zero due to the bandwidth smearing effect.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{ms3494f8.eps} \end{figure}$	Figure 8: Detail of $\alpha$ Cen B squared visibility. The continuous line is the uniform disk diameter fit (5.856 $\pm$ 0.027 mas), and the dotted lines represent the limits of the $\pm 1 \sigma$ error domain.
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$\begin{figure} \par\includegraphics[width=8.2cm,clip]{ms3494f9.eps} \end{figure}$	Figure 9: Intensity profile of $\alpha$ Cen A from the four-parameters limb darkening law of Claret (2000) (dashed line) and the corresponding $\alpha = 0.1417$ power law.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{ms3494hr.eps} \end{figure}$	Figure 10: HR diagram of $\alpha$ Cen B. The line on the right corresponds to a mixing length of $\lambda =0.96$ and a mass of 0.909 $M_{\odot }$ , the line on the left corresponds to the values published in Thévenin et al. 2002 ( $\lambda =0.98$ , 0.907 $M_{\odot }$ ).
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