All Figures

$\begin{figure} \par\resizebox{7cm}{!}{\includegraphics{1788fig2.eps}} \end{figure}$ Figure 2: 2MASS color-magnitude diagram of all the stars brighter than $K_{\rm S} = 12$ found in the search area outlined in Fig. 1. The solid, nearly vertical line is the unreddened main sequence locus at a distance of 1 kpc, with its upper limit corresponding to spectral type O5V. The dashed line is the extinction vector having its origin at the position of an unreddened B0V star at 1 kpc, corresponding to the limit given by Eq. (1). We do not consider as possible ionizing stars any objects falling below this line. The filled circles are the stars fulfilling the criterion Q < 0.30 characterizing (although not exclusively) early-type stars (see Sect. 2), and for which we obtained H and K band spectroscopy.
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In the text

$\begin{figure} \par\resizebox{7cm}{!}{\includegraphics{1788fig3.eps}} \end{figure}$ Figure 3: Infrared spectra of carbon stars included in our sample, characterized by the sharp flux drop at $\lambda = 1.77$ $\mu$ m. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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In the text

$\begin{figure} \par\resizebox{7cm}{!}{\includegraphics{1788fig4.eps}} \end{figure}$ Figure 4: Infrared spectra of mid- or late-type objects included in our sample other than carbon stars, characterized by the appearance of CO bandheads longwards of 2.29 $\mu$ m. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig5.eps}} \end{figure}$ Figure 5: Two stars with early-type spectra ruled out as possible ionizing sources. Star #9 is an unobscured star classified in the visible as F5V, while the prominent Br $\gamma$ lines unambigously classify Star #11 as an early A type. The reddening towards Star #11 indicates that it lies at the distance of L935 or beyond, suggesting that it is a giant or supergiant. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig6.eps}} \end{figure}$ Figure 6: Spectrum of Star #11, showing the Balmer lines H $\beta$ and higher. The strength of the hydrogen lines, and the lack of helium or metallic lines other than the interstellar CaII K line at $\lambda~=~3933$ Å, confirm that this is an early-type A star. The Balmer line wings are much less prominent than in luminosity class V stars, but broader than in the supergiant Deneb (A2Ia), thus suggesting a luminosity class III.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig7.eps}} \end{figure}$ Figure 7: Infrared spectrum of Star #4 = J205551.3+435225, which we propose as the ionizing star for the North America and Pelican nebulae. The lack of absorption lines at the resolution of this spectrum is consistent with a O or early B type, or with a F or later type. The former possibility is favored by the $JHK_{\rm S}$ colors. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig8.eps}} \end{figure}$ Figure 8: Visible spectrum of Star #4 = J205551.3+435225. Note the appearance of a strong HeII line at $\lambda = 4543$ Å and the correspondingly weak neighbouring HeI line at $\lambda = 4471$ Å, which indicate an O5 spectral classification. The broad feature centered near $\lambda = 4428$ Å is due to interstellar absorption.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig9.eps}} \end{figure}$ Figure 9: A detailed visible view of the L935 dark cloud separating the North America and the Pelican nebulae, marking the position of Star #4 = J205551.3+435225. The upper panel shows a $94'2 \times 84'9$ section of the same image as Fig. 1 centered on J205551.3+435225. The lower panel displays the same field as observed at the 1420 MHz radio continuum, in a grey scale where white corresponds to a brightness temperature $T_{\rm b} = 5$ K and black to $T_{\rm b} = 25$ K. The bubble-like structure on the lower right is the background supernova remnant G84.2-0.8 (Matthews et al. 1977). The radio data are from the Canadian Galactic Plane Survey (Taylor et al. 2003).
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In the text

$\begin{figure} \par\resizebox{12cm}{!}{\includegraphics{1788fig1.ps}} % \end{figure}$ Figure 1: The region of the North America (NGC 7000) and the Pelican (IC 5070) nebulae with the $0^\circ 5$ -radius circular area where we have searched for the ionizing star, containing most of the L935 dark cloud. The image, courtesy of the German-Spanish Astronomical Center, is a negative print of an image obtained with the Schmidt telescope on Calar Alto.
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In the text

$\begin{figure} \par\resizebox{7cm}{!}{\includegraphics{1788fig3.eps}} \end{figure}$	Figure 3: Infrared spectra of carbon stars included in our sample, characterized by the sharp flux drop at $\lambda = 1.77$ $\mu$ m. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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$\begin{figure} \par\resizebox{7cm}{!}{\includegraphics{1788fig4.eps}} \end{figure}$	Figure 4: Infrared spectra of mid- or late-type objects included in our sample other than carbon stars, characterized by the appearance of CO bandheads longwards of 2.29 $\mu$ m. The region between 1.85 $\mu$ m and 2.05 $\mu$ m is heavily affected by telluric H₂O and CO₂ absorption and has been removed.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{1788fig8.eps}} \end{figure}$	Figure 8: Visible spectrum of Star #4 = J205551.3+435225. Note the appearance of a strong HeII line at $\lambda = 4543$ Å and the correspondingly weak neighbouring HeI line at $\lambda = 4471$ Å, which indicate an O5 spectral classification. The broad feature centered near $\lambda = 4428$ Å is due to interstellar absorption.
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$\begin{figure} \par\resizebox{12cm}{!}{\includegraphics{1788fig1.ps}} % \end{figure}$	Figure 1: The region of the North America (NGC 7000) and the Pelican (IC 5070) nebulae with the $0^\circ 5$ -radius circular area where we have searched for the ionizing star, containing most of the L935 dark cloud. The image, courtesy of the German-Spanish Astronomical Center, is a negative print of an image obtained with the Schmidt telescope on Calar Alto.
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