Astronomy & Astrophysics

All Figures

$\begin{figure} \par\begin{tabular}{cc} \includegraphics[width=7cm]{5408-01.ps} & \includegraphics[width=8.5cm]{5408-02.ps}\\ \end{tabular} \end{figure}$ Figure 1: Left: projected baselines showing the range of position angles and base lengths on the sky during the observations. Right: absolute calibrated visibility of $\gamma ^2$ Velorum in function of base length. The strong variations correspond mainly to the partial resolution of the binary star.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{5408-03.ps}\par\vspace*{1.... ...ar\vspace*{1.5mm} \includegraphics[width=6.5cm,clip]{5408-06.ps} \end{figure}$ Figure 2: Top: result of the complete spectral calibration, showing the principal lines present in the observed spectrum. The dotted boxes show the selected continuum zones used to redress the observed spectrum. The other plots from top to bottom: observed data from AMBER. We show the differential visibilities, the differential phases and the closure phase versus wavelength. The differential visibility and differential phase curves from each baseline are arbitrarily shifted for clarity.
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{5408-07.ps} \end{figure}$ Figure 3: Projection of the true orbit as defined by the spectroscopic parameters (Schmutz et al. 1997) onto the plane of the sky. Note that there is an ambiguity of 180 $^\circ$ in the true direction of the WR versus the O star.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{5408-08.ps} \end{figure}$ Figure 4: Near-IR synthetic spectra computed by accounting for bound-bound transition of selected ions (He I: dashed line; He II: dotted line; C III: solid lines; C IV: dash-dotted line), illustrating the different line contributions and overlap in the AMBER spectral windows.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5408-09.ps}\hspace*{2mm} ... ...ps}\hspace*{2mm} \includegraphics[width=8.4cm,clip]{5408-12.ps} \end{figure}$ Figure 5: Observed data obtained with AMBER and the best fit, using a geometrical model of a double star and a O- and WR-star synthetic spectra of Sect. 4.2. Top-left: points with error bars: observed absolute visibilities versus base length. Crosses: our model. See text for comments. Top-right: gray line with error bars: observed differential visibilities versus wavelength. Dashed line: our model. The different baselines are offseted for clarity. Bottom-left: gray line with error bars: observed closure phase versus wavelength. Dashed line: the model. See text for comments. Bottom-right: gray line with error bars: observed differential phases versus wavelength. Dashed line: our model. The different baselines are offset for clarity.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5408-13.ps}\hspace*{2mm} ... ....ps}\hspace*{2mm} \includegraphics[width=8.4cm,clip]{5408-16.ps} \end{figure}$ Figure 6: Observed data obtained with AMBER and the best fit, using a geometrical model of a double star, an O-star synthetic spectrum and a reconstructed WR-star spectrum of Sect. 4.3. Top-left: points with error bars: observed absolute visibilities versus base length. Crosses: our model. See text for comments. Top-right: gray line with error bars: observed differential visibilities versus wavelength. Dashed line: our model. The different baselines are offset for clarity. Bottom-left: gray line with error bars: observed closure phase versus wavelength. Dashed line: the model. See text for comments. Bottom-right: gray line with error bars: observed differential phases versus wavelength. Dashed line: our model. The different baselines are offset for clarity.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5408-17.ps} \end{figure}$ Figure 7: The two final WR spectra. Dashed line: WR model of Sect. 4.2. Dash-dotted line: WR spectrum of Sect. 4.3. They show similarities in the lines at 2.059 $\mu$ m and 2.165 $\mu$ m but our modeled spectrum is less accurate in the carbon lines at 2.071 $\mu$ m, 2.079 $\mu$ m, 2.108 $\mu$ m and 2.114 $\mu$ m.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{5408-18.ps} \end{figure}$ Figure 8: Errors derived from the different techniques used to retrieve the geometrical parameters of the binary star at the time of the AMBER observations. The large gray box represents the estimation and error bars from the radial velocity method and the small gray box is the resulting parameters from our interferometric fit. The direct measured separation by interferometric means is smaller than the expected one, leading to a possible reevaluation of the distance of the system.
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In the text

$\begin{figure} \par\renewcommand{\thefigure}{A.1} \par\mbox{\includegraphics[wid... ...9.ps}\hspace{2mm} \includegraphics[width=7.8cm,clip]{5408-20.ps} }\end{figure}$ Figure A.1: Left: calibration of the spectral drift, using the reference star spectrum (flat A1 III star spectrum). From top to bottom are the uncalibrated observed $\gamma ^2$ Velorum spectrum, the calibrator star spectrum after removal of a Voigt profile in the Br $\gamma$ line, and the reference Gemini spectrum. All of them show a clear CO₂ rovibrationnal feature at 2.01 $\mu$ m and 2.06 $\mu$ m, and some other water vapor absorption lines, used for the absolute wavelength calibration. The graphs have been offset for clarity. Right: estimate of the absolute visibilities by applying different frame selection thresholds keeping the percentage of the observed frames (solid line with error bars, left axis). The internal dispersion of the visibilities increases as the amount of data rejected decreases but there is no obvious bias coming from data selection as the absolute visibilities stay constant within the error bars. The optimal selection threshold is chosen at the position of minimum of the statistical dispersion of the squared visibilities (dashed line, right axis): in this data set, this level keeps 20% of the observed frames (i.e. 80% rejected).

In the text

$\begin{figure} \par\begin{tabular}{cc} \includegraphics[width=7cm]{5408-01.ps} & \includegraphics[width=8.5cm]{5408-02.ps}\\ \end{tabular} \end{figure}$	Figure 1: Left: projected baselines showing the range of position angles and base lengths on the sky during the observations. Right: absolute calibrated visibility of $\gamma ^2$ Velorum in function of base length. The strong variations correspond mainly to the partial resolution of the binary star.
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$\begin{figure} \par\includegraphics[width=7.3cm,clip]{5408-07.ps} \end{figure}$	Figure 3: Projection of the true orbit as defined by the spectroscopic parameters (Schmutz et al. 1997) onto the plane of the sky. Note that there is an ambiguity of 180 $^\circ$ in the true direction of the WR versus the O star.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{5408-08.ps} \end{figure}$	Figure 4: Near-IR synthetic spectra computed by accounting for bound-bound transition of selected ions (He I: dashed line; He II: dotted line; C III: solid lines; C IV: dash-dotted line), illustrating the different line contributions and overlap in the AMBER spectral windows.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5408-17.ps} \end{figure}$	Figure 7: The two final WR spectra. Dashed line: WR model of Sect. 4.2. Dash-dotted line: WR spectrum of Sect. 4.3. They show similarities in the lines at 2.059 $\mu$ m and 2.165 $\mu$ m but our modeled spectrum is less accurate in the carbon lines at 2.071 $\mu$ m, 2.079 $\mu$ m, 2.108 $\mu$ m and 2.114 $\mu$ m.
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