Astronomy & Astrophysics

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$\begin{figure} \par\resizebox{7.5cm}{!}{\rotatebox{0}{\includegraphics[clip]{0668fig1.ps}}} \end{figure}$ Figure 1: The model used in the present work. The photosphere is approximated with a blackbody of $T_{\rm eff}$ , with a radius $R_{\star }$ . The column density in the radial direction ( $N_{\rm col}$ ) and the temperature of H₂O gas ( $T_{\rm mol}$ ) as well as the radius of the water vapor envelope ( $R_{\rm mol}$ ) are the input parameters.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig2.ps}}} \end{figure}$ Figure 2: Spectra in the 11 $\mu$ m region. The dots represent the spectra of $\alpha$ Ori presented in WHT03b, while the solid lines represent the calculated spectra from the best-fit model with $T_{\rm mol} = 2050$ K, $R_{\rm mol} = 1.45$ $R_{\star }$ , and $N_{\rm col} = 2 \times 10^{20}$ cm^-2. The synthetic spectra are convolved with a Gaussian with a FWHM of 0.037 cm^-1 to account for the effects of the instrument as well as of the macroturbulent velocity, and redshifted by 39 km s^-1 to match the observations. The positions of the H₂O lines whose intensity at 2000 K is stronger than $3 \times 10^{-23}$ cm molecule^-1 are marked with ticks. These line positions are taken from the HITEMP database, and are also redshifted by 39 km s^-1 with respect to the rest wavenumber.
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In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig3.ps}}} \end{figure}$ Figure 3: Top panel: spectra predicted from the best-fit model for $\alpha$ Ori at the stellar disk center ( $\mu = 1$ , upper spectrum) and near the limb of the warm H₂O envelope ( $\mu = 0.3$ , lower spectrum) in the region around 11.1494 $\mu$ m. The continuum level is shown with the dashed line. The flux contribution of dust emission is not included in the spectra shown. Middle panel: the resulting spectrum (emergent flux) expected for the whole object (stellar disk + warm water vapor envelope), calculated from the intensity spectra such as shown in the upper panel, using Eq. (2). Bottom panel: optical depth in the radial direction due to H₂O lines in the same spectral region. The spectra and the flux shown in the top and middle panels as well as the optical depth shown in the bottom panel are redshifted by 39 km s^-1 with respect to the rest wavenumber to match the observed spectra shown in Fig. 2, but not convolved with the Gaussian representing the instrumental effect and the macroturbulent velocity.
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In the text

$\begin{figure} \par\resizebox{8.7cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig4.ps}}} \end{figure}$ Figure 4: Spectra in the 12 $\mu$ m region. The dots represent the spectra of $\alpha$ Ori observed by Jennings & Sada (1998), while the solid lines represent the calculated spectra of the best-fit model. The synthetic spectra are convolved with a Gaussian with a FWHM of 0.1 cm^-1 to match the resolution of the spectrometer used by Jennings & Sada (1998). The ticks represent the positions of H₂O lines whose intensity at 2000 K is stronger than $3 \times 10^{-23}$ cm molecule^-1. The observed and predicted spectra as well as the H₂O line positions are plotted in the laboratory frame. The H₂O lines identified by Jennings & Sada (1998) are shown with the arrows.
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In the text

$\begin{figure} \par\resizebox{8.7cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig5.ps}}} \end{figure}$ Figure 5: Spectra in the 6 $\mu$ m region. The thin solid line represents the ISO SWS spectrum of $\alpha$ Ori, while the thick solid line represents the synthetic spectrum predicted from the best-fit model. The synthetic spectrum is convolved with a Gaussian with a FWHM of 1.0 cm^-1. The ticks mark the H₂O absorption features identified by Tsuji (2000b).
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In the text

$\begin{figure} \par\resizebox{8.4cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig6.ps}}} \end{figure}$ Figure 6: a) Visibility calculated from the best-fit model for $\alpha$ Ori in the region around 11.1494 $\mu$ m. The visibility shown here is calculated for a projected baseline length of 30 m. b) Uniform disk diameter calculated from the spectrally convolved visibility shown in a) for a projected baseline length of 30 m. In a) and b), two bandpasses used by WHT03b are marked with the dashed lines. The bandpasses used for the other observations of $\alpha$ Ori lie between those shown (see WHT03b). The range of the diameters measured in these bandpasses is shown as the hatched region. The dotted line represents the photospheric angular diameter adopted in the calculation. A flux contribution of 44% from the dust shell is included in the calculations of the model visibility, but not in the computation of the uniform disk diameter. Both plots ( a) and b)) are redshifted by 0.117 cm^-1 with respect to the rest wavenumber, which corresponds to a radial velocity of 39 km s^-1, to match the observed spectra shown in Fig. 2. c) The normalized intensity profile at 896.85 cm^-1, which is spectrally convolved with the same top-hat function as used in the calculation of the spectrally convolved visibility shown in a). d) The spectrally convolved visibility squared at 896.85 cm^-1 (solid line), plotted together with the visibility points observed by WHT03b (filled diamonds). e) The same spectrally convolved visibility squared as in d), but at higher spatial frequencies.
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In the text

$\begin{figure} \par\resizebox{8.5cm}{!}{\rotatebox{0}{\includegraphics[clip]{0668fig7.ps}}} \end{figure}$ Figure 7: Uniform disk diameter around 11.0856 $\mu$ m ( upper panel) and 11.1713 $\mu$ m ( lower panel) calculated from the best-fit model for $\alpha$ Ori. Both plots are redshifted by 0.117 cm^-1 in wavenumber, which corresponds to a radial velocity of 39 km s^-1, to match the observed spectra shown in Fig. 2. The bandpasses used by WHT03b are marked with the dashed lines, and the ranges of the angular diameters measured by WHT03b are represented as the hatched regions. The dotted lines represent the photospheric angular diameter adopted in the calculation.
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In the text

$\begin{figure} \par\resizebox{8.7cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig8.ps}}} \end{figure}$ Figure 8: Spectra in the region around 11.1494 $\mu$ m. The dots represent the observed spectrum of $\alpha$ Her, while the solid line represents the synthetic spectrum from the best-fit model. The synthetic spectrum is convolved with a Gaussian with a FWHM of 0.037 cm^-1, and blueshifted by 0.084 cm^-1 in wavenumber, which corresponds to a radial velocity of -28 km s^-1 (see WHT03b), to match the observation. The positions of the H₂O lines whose intensity at 2000 K is stronger than $3 \times 10^{-23}$ cm molecule^-1 are marked with ticks. These line positions are taken from the HITEMP database, and are also blueshifted by 28 km s^-1 with respect to the rest wavenumber.
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In the text

$\begin{figure} \par\resizebox{8.7cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig9.ps}}} \end{figure}$ Figure 9: Visibility and uniform disk diameter calculated from the best-fit model for $\alpha$ Her in the region around 11.1494 $\mu$ m. The visibility and the uniform disk diameter shown are calculated for a projected baseline length of 30 m. No flux contribution of the dust shell is assumed in the calculation of the model visibility and uniform disk diameter. The dotted line represents the adopted photospheric angular diameter, while the range of the angular diameter measured by WHT03b is shown as the hatched region. Both plots are blueshifted by 0.084 cm^-1 with respect to the rest wavenumber to match the observation.
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In the text

$\begin{figure} \par\resizebox{7.5cm}{!}{\rotatebox{0}{\includegraphics[clip]{0668fig1.ps}}} \end{figure}$	Figure 1: The model used in the present work. The photosphere is approximated with a blackbody of $T_{\rm eff}$ , with a radius $R_{\star }$ . The column density in the radial direction ( $N_{\rm col}$ ) and the temperature of H₂O gas ( $T_{\rm mol}$ ) as well as the radius of the water vapor envelope ( $R_{\rm mol}$ ) are the input parameters.
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$\begin{figure} \par\resizebox{8.7cm}{!}{\rotatebox{-90}{\includegraphics[clip]{0668fig5.ps}}} \end{figure}$	Figure 5: Spectra in the 6 $\mu$ m region. The thin solid line represents the ISO SWS spectrum of $\alpha$ Ori, while the thick solid line represents the synthetic spectrum predicted from the best-fit model. The synthetic spectrum is convolved with a Gaussian with a FWHM of 1.0 cm^-1. The ticks mark the H₂O absorption features identified by Tsuji (2000b).
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