All Figures

$\begin{figure} \par\includegraphics[width=8cm,clip]{7834_f01.eps}\end{figure}$ Figure 1: Synthetic spectra calculated with different treatment of the overlapping hydrogen-line opacity. Usual calculation ( HLINOP routine, dashed line) is compared with spectrum synthesis based on the occupation probability formalism ( HBOP routine, solid line). In both cases, ATLAS9 model atmosphere with $T_{\rm eff}$ = 8500 K, and $\log g$ = 4.0 was adopted. The vertical bars show position of the Ca II IR triplet lines.
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{7834_f02new2.eps}\end{figure}$ Figure 2: Comparison between the observed line profiles (symbols) of HD 176232 (10 Aql) and theoretical spectra calculated with the best-fitting stratified Ca abundance distribution (solid line) and with the homogeneous Ca abundance (dashed line). The plotted spectral windows show segments of the HD 176232 spectra used for determination of Ca stratification; symbols show actual observed points.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7834_f03.eps}\end{figure}$ Figure 3: Comparison between the observed profiles (symbols) of the Ca II 3933 Å line and calculations with the stratified (solid line) and homogeneous (dashed line) Ca distributions for 3 program stars. The spectra of HD 24712 and HD 176232 are shifted downwards for display purpose.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7834_f04.eps}\end{figure}$ Figure 4: Vertical stratification and isotopic separation of Ca derived for HD 176232. The overall Ca abundance profile, inferred from the stratification analysis of optical lines, is shown with the solid line. The hatched areas demonstrate vertical separation of the light and heavy Ca isotopes required to fit the Ca II 8498 Å line. The dashed line shows the Ca distribution derived the with VIP code using the same set of lines.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7834_f05.ps}\end{figure}$ Figure 5: Comparison between the observed line profiles (symbols) of the Ca II 8498 Å line and calculations for the normal Ca isotopic mixture (solid line) in the spectra of Procyon, Am star HD 27411, and A1 V star HD 73666. The observed spectrum of the cool (HD 217522) and tepid (HD 133792) Ap stars, presented in the middle and bottom, clearly shows a displaced Ca II line core. The spectra are shifted downwards for display purpose.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7834_f06.eps}\end{figure}$ Figure 6: Derivation of the isotopic composition and its height dependence for the Ca II 8498 Å line in HD 176232 (10 Aql). The three panels show the UVES observations (full circles) compared to various modelling attempts, as follows. a) Dashed line: theoretical spectrum obtained with a homogeneous Ca distribution. Solid line: theoretical spectrum calculated for a stratified Ca abundance. A terrestrial mixture of Ca isotopes is adopted for these computations. b) Solid line: theoretical spectrum obtained for a terrestrial Ca isotopic composition (same as panel a); Dashed line: theoretical spectrum obtained for a 50:50 ratio of ⁴⁰Ca to ⁴⁶Ca+⁴⁸Ca. c) Solid line: the Ca II line profile computed for the best-fitting model of vertical isotopic separation (see Fig. 4). Dashed and dash-dotted lines show contributions of ⁴⁰Ca and ⁴⁶Ca+⁴⁸Ca, respectively. The wavelength position of ⁴⁰Ca and ⁴⁸Ca is indicated in each panel. These plots show that an acceptable fit to the observations can only be achieved with a depth-dependent Ca isotopic mixture.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7834_f07.eps}\end{figure}$ Figure 7: Comparison of the observed IR triplet lines (symbols) in the ESPaDOnS spectrum of HD 24712 and theoretical spectrum synthesis for the best-fitting stratified Ca abundance distribution (solid line) with Ca isotopic separation and with the stratified distribution of ⁴⁸Ca only (dashed line).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7834_f08.eps}\end{figure}$ Figure 8: Ca stratification in the atmospheres of selected program stars. Upper panel: distribution of Ca in HD 66318, HD 75445, HD 134214, HD 166473 and HD 111133. For stars enriched in heavy Ca the filled circle indicates the bottom of the heavy Ca isotope layer. Lower panel: same for stars with complex distribution of Ca abundance with height (HD 965, HD 116114, HD 137909, HD 137949, HD 217522).
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7834_f09a.ps}\hspace*{1.5mm} \includegraphics[width=7cm,clip]{7834_f09b.ps}\end{figure}$ Figure 9: Comparison of the observed (full circles) and calculated (lines) profiles of the Ca II 8498 Å line in a subset of program stars. Solid line shows theoretical calculations for the terrestrial Ca isotopic mixture and the Ca stratification derived from optical lines. The dashed line presents spectrum synthesis for the models with vertical separation of the Ca isotopes. The stars are arranged in order of increasing magnetic field strength.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7834_f10.ps}\end{figure}$ Figure 10: Same as in Fig. 9 but for the stars with $T_{\rm eff}$ > 9000 K.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{7834_f11.eps}\end{figure}$ Figure 11: Results of the analysis of Ca isotopic composition in Ap stars. a) Ratio of calculated equivalent width of the heavy and light Ca components of the 8498 Å line vs. magnetic field strength. b) Position of the boundary between the light and heavy Ca layers vs. magnetic field strength. c) The equivalent width ratio vs. the total equivalent width of the Ca II 8498 Å line. d) The equivalent width ratio vs. the optical depth of the boundary between the light and heavy Ca layers. In all plots different symbols correspond to Ap stars with detected presence of heavy Ca ( filled symbols) and those showing no heavy Ca isotopes ( open symbols), as well as to roAp ( circles) and non-pulsating Ap ( triangles) stars.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7834_f03.eps}\end{figure}$	Figure 3: Comparison between the observed profiles (symbols) of the Ca II 3933 Å line and calculations with the stratified (solid line) and homogeneous (dashed line) Ca distributions for 3 program stars. The spectra of HD 24712 and HD 176232 are shifted downwards for display purpose.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7834_f07.eps}\end{figure}$	Figure 7: Comparison of the observed IR triplet lines (symbols) in the ESPaDOnS spectrum of HD 24712 and theoretical spectrum synthesis for the best-fitting stratified Ca abundance distribution (solid line) with Ca isotopic separation and with the stratified distribution of ⁴⁸Ca only (dashed line).
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$\begin{figure} \par\includegraphics[width=7cm,clip]{7834_f10.ps}\end{figure}$	Figure 10: Same as in Fig. 9 but for the stars with $T_{\rm eff}$ > 9000 K.
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