Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[width=14.9cm,height=10.1cm,clip]{10376.f1.eps} \end{figure}$ Figure 1: Modal SNR per interferogram as a function of the magnitude of the source in the K band. From left to right, top to bottom, the object size increases: point source, 1/50, 1/20, 1/10 of Airy disk. The considered baseline is $Bx=By=100~{\rm m}$ which mimics an average baseline of the VLTI array. This corresponds to visibility of respectively 1, 0.882, 0.457, 0.04. Results are given for different Strehl ratios: $\mathcal{S}=0.011$ (solid line, no correction), $\mathcal{S}=0.1$ (dashed line), $\mathcal{S}=0.5$ (dash-dotted line) and $\mathcal{S}=0.9$ (dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{10376.f2.ps} \end{figure}$ Figure 2: Instantaneous limiting magnitude of single-mode interferometry technique, defined such that the modal SNR per interferogram is equal to unity. From top to bottom we plot limiting magnitudes for object sizes of respectively: point source, 1/50, 1/20, and 1/10 of Airy disk. Note that Eq. (15) reproduces fairly well the curves for object sizes equal or smaller than 1/20 of Airy disk.
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In the text

$\begin{figure} \par\includegraphics[width=14.9cm,height=10.1cm,clip]{10376.f3.eps} \end{figure}$ Figure 3: Multispeckle SNR per interferogram as a function of the magnitude of the source in the K band. As Fig. 1, which those curves must be compared to, the object size is varying from left to right, top to bottom: point source, 1/50, 1/20, 1/10 of Airy disk, for a baseline $Bx=By=100~{\rm m}$ . Results are given for different Strehl ratios: $\mathcal{S}=0.011$ (solid line, no correction), $\mathcal{S}=0.1$ (dashed line), $\mathcal{S}=0.5$ (dash-dotted line) and $\mathcal{S}=0.9$ (dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=13.9cm,height=15.8cm,clip]{10376.f4.eps} \end{figure}$ Figure 4: Ratio between fibered and multispeckle visibility SNR as a function of the magnitude for different AO correction levels, from left to right, top to bottom: $\mathcal{S}=0.011$ (no correction), $\mathcal{S} = 0.05$ , $\mathcal{S}=0.1$ , $\mathcal{S} = 0.2$ , $\mathcal{S}=0.5$ , $\mathcal{S} = 0.7$ , $\mathcal{S}=0.9$ and $\mathcal{S} =1$ . Ratios are displayed for different source sizes in fraction of Airy disk: point source (solid line), 1/50 (dashed line), 1/20 (dash-dotted line), 1/10 (dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{10376.f5.ps} \end{figure}$ Figure 5: Comparison of fibered and speckle interferometry limiting magnitudes. Limiting magnitude is still defined such that ${\it SNR} = 1$ . Solid lines and dashed lines show fiber and speckle cases respectively. From top to bottom, the object size is: point source, 1/50, 1/20, and 1/10 of Airy disk.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{10376.f6.ps} \end{figure}$ Figure 6: Robustness of single-mode and multimode estimators as a function of the Strehl ratio. Comparison is given in terms of relative error on the visibility $\Delta {V}/V$ . Solid lines deal with fiber estimator for respectively 1/10, 1/20 and 1/100 of Airy disk, top to bottom. Dashed lines gives the robustness of two speckle estimators. Top: so-called estimator I which takes into account the estimator defined in this paper (Eq. (16)). Bottom: estimator II describes the "classical'' speckle estimator (see text). Note that both speckle estimators are object size independent.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{10376.f2.ps} \end{figure}$	Figure 2: Instantaneous limiting magnitude of single-mode interferometry technique, defined such that the modal SNR per interferogram is equal to unity. From top to bottom we plot limiting magnitudes for object sizes of respectively: point source, 1/50, 1/20, and 1/10 of Airy disk. Note that Eq. (15) reproduces fairly well the curves for object sizes equal or smaller than 1/20 of Airy disk.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{10376.f5.ps} \end{figure}$	Figure 5: Comparison of fibered and speckle interferometry limiting magnitudes. Limiting magnitude is still defined such that ${\it SNR} = 1$ . Solid lines and dashed lines show fiber and speckle cases respectively. From top to bottom, the object size is: point source, 1/50, 1/20, and 1/10 of Airy disk.
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