All Figures

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi01.ps} \end{figure}$ Figure 1: Lower six panels: photometric evolution of Nova Cyg 2006 in the $\it UBVR_{\rm C}I_{\rm C}$ bands. Upper six panels: temporal evolution of [OI] 8446/H $\alpha$ and [OI] 6300/[OI] 6364 flux ratios, of [OI] 6300, [OII] 7325, [OIII] 5007, and H $\alpha$ integrated line flux (expressed in magnitudes relative their peak values $9.364\times 10^{-12}$ , $7.151\times 10^{-12}$ , $1.249 \times 10 ^{-11}$ , and $3.351\times 10^{-10}$ erg cm^-2 s^-1, respectively), of H $\alpha$ equivalent width, and of FWHM (in km s^-1) of H $\beta$ , [OI] 6300, and [NII] 5750 Å emission line profiles. After day +250, a growing fraction of [NII] 6548, 6584 emission contributed to the H $\alpha$ flux and equivalent width.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9502fi02.ps} \end{figure}$ Figure 2: Left panel: a small portion of the combined Echelle spectra for April 13 and 14, 2006 of Nova Cyg 2006, centered on the interstellar NaI D_1,2 absorption lines. Right panel: blowup of the interstellar NaI D₂ line (thicker line) showing the fit with two components at -39.1 ( $\pm$ 0.4) and -11.1 ( $\pm$ 0.3) km s^-1 (thinner line).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9502fi03.ps} \end{figure}$ Figure 3: Comparison between the equivalent width of three diffuse interstellar bands and interstellar reddening for field stars measured by Megier et al. (2005). The crosses represent the position of Nova Cyg 2006.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{9502fi04.ps} \end{figure}$ Figure 4: The early photometric decline of Nova Cyg 2006. For instrument identification see Sect. 2.1. The solid curve over-plotted to the V data in panel d) is Eq. (1), while the dotted curve is drawn by hand only for eye guidance. The a panel shows the evolution in equivalent width of an un-blended emission line for each of the FeII multiplets 27, 42, 49, 55 and 74 (4233, 4924, 5317, 5535 and 6239 Å, respectively). Panel b) presents the change in radial velocity of absorption systems (the ``de'' diffuse-enhanced and the ``p₁'' and ``p₂'' principal systems seen in H $\alpha$ , and the ``Or'' Orion system seen in HeI 6678 Å).
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{9502fi05.ps} \end{figure}$ Figure 5: Early spectroscopic evolution of Nova Cyg 2006. The spectra are continuum-normalized and shifted to avoid overlap. The ordinates are in logarithm of the flux to emphasize the visibility of weaker features. $\Delta t$ and $\Delta V$ are days and magnitudes from maximum. Emission lines are identified (FeII multiplets by their numbers and comb-like markings).
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{9502fi06.ps} \end{figure}$ Figure 6: Evolution of the H $\alpha$ profile at three epochs during the first three weeks past maximum (see Sect. 5.3.1 for details).
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In the text

$\begin{figure} \par\includegraphics[width=17cm,clip]{9502fi09.ps} \end{figure}$ Figure 9: Spectroscopic evolution of Nova Cyg 2006 during the plateau phase in June-September 2006 (see Fig. 5 for plotting details). The asterisks mark the positions of the principal Orion absorption lines on the September 26 spectrum (see Sect. 6 for the line list).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9502fi10.ps} \end{figure}$ Figure 10: Middle panel: photometric evolution of Nova Cyg 2006 around second maximum. B-band lightcurve is at the top, $R_{\rm C}$ center, $I_{\rm C}$ bottom. For telescope identification letters see Sect. 2.1. Bottom panel: color evolution as recorded with telescope a. Upper panels: evolution of integrated flux and equivalent width of selected emission lines, expressed in magnitudes with respect to highest value. The 4660 blend is initially dominated by NIII, than HeII become a relevant contributor. The 4990 blend is initially due to NII, then [OIII] becomes the dominant contributor.
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In the text

$\begin{figure} \par\includegraphics[width=17cm,clip]{9502fi11.ps} \end{figure}$ Figure 11: Spectroscopic evolution of Nova Cyg 2006 during second maximum in autumn 2006 (see Fig. 5 for plotting details).
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi12.ps} \end{figure}$ Figure 12: Evolution of H $\alpha$ profile during the plateau phase, the second maximum and the advanced decline. $\Delta t$ and $\Delta V$ are days and magnitudes from maximum.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi13.ps} \end{figure}$ Figure 13: The optical and infrared spectral energy distribution of Nova Cyg 2006 showing the presence of optically thin dust emission on December 2006. Optical data are from Table 1, and infrared data from Russell et al. (2006), Mazuk et al. (2006), and Lynch et al. (2006). The curves are fits with black bodies at the indicated temperatures and reddened by E_B-V=0.56 following a R_V=3.1 standard law.
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In the text

$\begin{figure} \par\includegraphics[width=16.5cm,clip]{9502fi14.ps} \end{figure}$ Figure 14: Spectroscopic evolution of Nova Cyg 2006 during the advanced decline from December 2006 to September 2007 (see Fig. 5, for plotting details).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{9502fi15.ps} \end{figure}$ Figure 15: Comparison of Nova Cyg 2006 V-band lightcurve with the $m_{\rm vis}$ lightcurve of Nova Aql 1999 N.1 (AAVSO visual estimates). The ordinate scale is the same in both panels. The time scale of Nova Aql 1999 N.1 abscissas is 5.0 $\times$ faster that that of Nova Cyg 2006.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi07.ps} \end{figure}$ Figure 7: Electron temperature as a function of (reddening corrected) [OI] 6300/[OI] 5577 flux ratio for different values of optical depth in the 6300 line.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi08.ps} \end{figure}$ Figure 8: Ratio between mass of neutral oxygen in the ejecta and [OI] 6300 line flux as a function of [OI] 6300 emission line optical depth, at 7.2 kpc distance and E_B-V=0.56 estimated for Nova Cyg 2006.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi16.ps} \end{figure}$ Figure 16: U-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi17.ps} \end{figure}$ Figure 17: B-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi18.ps} \end{figure}$ Figure 18: V-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi19.ps} \end{figure}$ Figure 19: $R_{\rm C}$ -band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi20.ps} \end{figure}$ Figure 20: $I_{\rm C}$ -band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9502fi02.ps} \end{figure}$	Figure 2: Left panel: a small portion of the combined Echelle spectra for April 13 and 14, 2006 of Nova Cyg 2006, centered on the interstellar NaI D_1,2 absorption lines. Right panel: blowup of the interstellar NaI D₂ line (thicker line) showing the fit with two components at -39.1 ( $\pm$ 0.4) and -11.1 ( $\pm$ 0.3) km s^-1 (thinner line).
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9502fi03.ps} \end{figure}$	Figure 3: Comparison between the equivalent width of three diffuse interstellar bands and interstellar reddening for field stars measured by Megier et al. (2005). The crosses represent the position of Nova Cyg 2006.
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$\begin{figure} \par\includegraphics[width=16cm,clip]{9502fi05.ps} \end{figure}$	Figure 5: Early spectroscopic evolution of Nova Cyg 2006. The spectra are continuum-normalized and shifted to avoid overlap. The ordinates are in logarithm of the flux to emphasize the visibility of weaker features. $\Delta t$ and $\Delta V$ are days and magnitudes from maximum. Emission lines are identified (FeII multiplets by their numbers and comb-like markings).
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$\begin{figure} \par\includegraphics[width=6.5cm,clip]{9502fi06.ps} \end{figure}$	Figure 6: Evolution of the H $\alpha$ profile at three epochs during the first three weeks past maximum (see Sect. 5.3.1 for details).
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$\begin{figure} \par\includegraphics[width=17cm,clip]{9502fi09.ps} \end{figure}$	Figure 9: Spectroscopic evolution of Nova Cyg 2006 during the plateau phase in June-September 2006 (see Fig. 5 for plotting details). The asterisks mark the positions of the principal Orion absorption lines on the September 26 spectrum (see Sect. 6 for the line list).
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$\begin{figure} \par\includegraphics[width=17cm,clip]{9502fi11.ps} \end{figure}$	Figure 11: Spectroscopic evolution of Nova Cyg 2006 during second maximum in autumn 2006 (see Fig. 5 for plotting details).
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi12.ps} \end{figure}$	Figure 12: Evolution of H $\alpha$ profile during the plateau phase, the second maximum and the advanced decline. $\Delta t$ and $\Delta V$ are days and magnitudes from maximum.
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$\begin{figure} \par\includegraphics[width=16.5cm,clip]{9502fi14.ps} \end{figure}$	Figure 14: Spectroscopic evolution of Nova Cyg 2006 during the advanced decline from December 2006 to September 2007 (see Fig. 5, for plotting details).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{9502fi15.ps} \end{figure}$	Figure 15: Comparison of Nova Cyg 2006 V-band lightcurve with the $m_{\rm vis}$ lightcurve of Nova Aql 1999 N.1 (AAVSO visual estimates). The ordinate scale is the same in both panels. The time scale of Nova Aql 1999 N.1 abscissas is 5.0 $\times$ faster that that of Nova Cyg 2006.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi07.ps} \end{figure}$	Figure 7: Electron temperature as a function of (reddening corrected) [OI] 6300/[OI] 5577 flux ratio for different values of optical depth in the 6300 line.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{9502fi08.ps} \end{figure}$	Figure 8: Ratio between mass of neutral oxygen in the ejecta and [OI] 6300 line flux as a function of [OI] 6300 emission line optical depth, at 7.2 kpc distance and E_B-V=0.56 estimated for Nova Cyg 2006.
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$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi16.ps} \end{figure}$	Figure 16: U-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi17.ps} \end{figure}$	Figure 17: B-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi18.ps} \end{figure}$	Figure 18: V-band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi19.ps} \end{figure}$	Figure 19: $R_{\rm C}$ -band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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$\begin{figure} \par\includegraphics[angle=-90,width=17cm,clip]{9502fi20.ps} \end{figure}$	Figure 20: $I_{\rm C}$ -band lightcurve of Nova Cyg 2006 formed with all data available in Table 1, color- and symbol-coded according to the different instruments that collected the data (see Sect. 2.1 for a-g instrument identification letters).
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