All Figures

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg1a.eps}\par\vspace*{2m... ...eps}\par\vspace*{2mm} \includegraphics[width=8cm,clip]{8590fg1c.eps}\end{figure}$ Figure 1: Comparison between spectra of Deneb from 2001 (dotted) and 2005 (solid). Spectral regions around H $\alpha$ (upper), H $\delta$ (middle), and the Mg I triplet (lower panel) are displayed. Note the numerous sharp telluric H₂O features in the H $\alpha$ region. The wind-dominated H $\alpha$ line shows a pronounced P-Cygni profile in 2001 and reduced emission in 2005. Only the cores of the higher Balmer lines and few of the strongest metal lines (like Fe II $\lambda 5169$ ) are affected by the variable stellar wind.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{8590fg2a.eps}\hspace*{4mm} \includegraphics[width=7.9cm,clip]{8590fg2b.eps} \end{figure}$ Figure 2: Temperature determination for Deneb using the Mg I/II non-LTE ionisation equilibrium. Displayed are the observed line profiles for some strategic lines, Mg I $\lambda$ 5183 (left panel) and Mg II $\lambda$ 4390 and He I $\lambda$ 4387 (right panel), and the best fit for stellar parameters as given in Table 2 (thick red line); theoretical profiles for varied parameters are also shown (thin red lines, as indicated). A vertical shift by 0.3 units has been applied to the upper set of profiles. Note the strong sensitivity of the minor ionic species, Mg I, to parameter changes, while Mg II is virtually unaffected.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{8590fg3a.eps}\hspace*{4mm} \includegraphics[width=8.2cm,clip]{8590fg3b.eps} \end{figure}$ Figure 3: Impact of stellar parameter variations on non-LTE line profile fits (left panel). Synthetic spectra for the adopted parameters (see Table 2, thick red line) and varied parameters as indicated (thin red lines) are compared to observations. A vertical shift by 0.5 units has been applied to the upper profiles. Right panel: observation and spectrum synthesis with FASTWIND for $\log g$ = 1.12 dex (central line) and two variations as indicated. Note that, although the hydrodynamical FASTWIND model produces a better agreement with the observation, the resulting parameters of both methods are practically identical.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8590fg4a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8590fg4b.eps} \end{figure}$ Figure 4: Impact of variations in mass-loss rate and turbulent velocity on H $\alpha$ model spectra (computed with FASTWIND). The final model was calculated with the wind parameters in Table 2.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg5.eps} \end{figure}$ Figure 5: Comparison of the ATLAS9 model flux (dotted line) with UV-spectra from IUE (full line) and with measurements in various magnitude systems (Johnson, Strömgren, 2MASS). The theoretical flux is calculated for our final parameters (Table 2). The SEDs are normalised in V.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{8590fg6.eps} \par\end{figure}$ Figure 6: An overview of non-LTE and LTE abundances for individual lines of all metals treated in non-LTE. The abundance derived from a single line is presented versus its equivalent width, if measurable. Filled red symbols indicate non-LTE abundances, empty green ones LTE abundances. Moreover, squares mean neutral species, circles single-ionized species. For each element, the non-LTE mean value with statistical uncertainties of all lines (including those analysed only by spectrum synthesis) is represented by grey bands.
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In the text

$\begin{figure} \par\includegraphics[width=16.7cm,clip]{8590fg7.eps} \end{figure}$ Figure 7: Comparison of our spectrum synthesis (thin red line) with the high-resolution spectrum of Deneb (full black line). The spectral features used for our abundance determination are identified, short vertical marks designate Fe II lines.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg8.eps} \end{figure}$ Figure 8: Results from the elemental abundance analysis (relative to the solar composition, Grevesse & Sauval 1998) for Deneb. Filled symbols denote non-LTE, open symbols LTE results. Boxes: neutral; circles: single-ionized; diamonds: double-ionized species. The symbol size codes the number of spectral lines analysed - small: 1 to 5; medium: 6 to 10; large: more than 10. Error bars represent 1 $\sigma$ -uncertainties from the line-to-line scatter. The grey-shaded area marks the deduced metallicity of Deneb within 1 $\sigma$ -errors. The non-LTE abundance analysis reveals abundances of -0.20 $\pm$ 0.04 dex (relative to solar composition) for all heavier elements in close agreement.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg9.eps} \end{figure}$ Figure 9: Same as Fig. 8, for the LTE analysis of Albayrak (2000). Larger statistical uncertainties become apparent than in our non-LTE, and even our LTE analysis and systematic effects occur. Striking features are the He-deficiency and discrepancies in some ionisation equilibria (e.g. C I/II and Fe I/II vs. Fe III).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg10.eps} \end{figure}$ Figure 10: Same as Fig. 8, for the results of Takeda et al. (1996). Non-LTE calculations were made only for neutral species. Note that He tends to be depleted, while the heavier elements indicate super-solar abundances, unlike our results.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{8590fg11.eps} \end{figure}$ Figure 11: Modelling (red) of the hydrogen lines in the visual and the near-IR (black curve). The synthetic spectra are calculated with our hybrid non-LTE technique using DETAIL/SURFACE (photospheric lines) or FASTWIND (FW, wind-affected lines), as indicated. Except for the Pfund series, all panels show the same range in relative flux. Some lines, such as P $\beta$ and H $\beta$ , are noticeably affected by the stellar wind.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg12.eps} \end{figure}$ Figure 12: Stellar evolution tracks (Meynet & Maeder 2003) in the HRD for different ZAMS masses of stars with an initial rotational velocity of 300 km s^-1 (full lines) or 0 km s^-1 (dotted lines) and solar metallicity until the end of central helium burning. Observed N/C ratios (large numbers) are displayed for a few objects: Deneb (dot) and three stars from Przybilla et al. (2006, open circles). Small numbers along the curves indicate the progression of N/C-ratios (mass fractions) in the course of evolution, assuming an initial value of 0.31 (solar). The N/C ratios at the red supergiant stage mark the situation at the end of central helium burning, with the exception of the 25 $M_\odot$ model with rotation which enters the Wolf-Rayet phase near the end of central helium burning.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8590fg4a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8590fg4b.eps} \end{figure}$	Figure 4: Impact of variations in mass-loss rate and turbulent velocity on H $\alpha$ model spectra (computed with FASTWIND). The final model was calculated with the wind parameters in Table 2.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg5.eps} \end{figure}$	Figure 5: Comparison of the ATLAS9 model flux (dotted line) with UV-spectra from IUE (full line) and with measurements in various magnitude systems (Johnson, Strömgren, 2MASS). The theoretical flux is calculated for our final parameters (Table 2). The SEDs are normalised in V.
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$\begin{figure} \par\includegraphics[width=16.7cm,clip]{8590fg7.eps} \end{figure}$	Figure 7: Comparison of our spectrum synthesis (thin red line) with the high-resolution spectrum of Deneb (full black line). The spectral features used for our abundance determination are identified, short vertical marks designate Fe II lines.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg9.eps} \end{figure}$	Figure 9: Same as Fig. 8, for the LTE analysis of Albayrak (2000). Larger statistical uncertainties become apparent than in our non-LTE, and even our LTE analysis and systematic effects occur. Striking features are the He-deficiency and discrepancies in some ionisation equilibria (e.g. C I/II and Fe I/II vs. Fe III).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8590fg10.eps} \end{figure}$	Figure 10: Same as Fig. 8, for the results of Takeda et al. (1996). Non-LTE calculations were made only for neutral species. Note that He tends to be depleted, while the heavier elements indicate super-solar abundances, unlike our results.
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