All Figures

$\begin{figure} \par\rotatebox{0}{\resizebox{17.2cm}{!}{\includegraphics{0400fig01.ps}}}\end{figure}$ Figure 1: The reduced 2.4-15 $\mu$ m SWS spectra of the sample stars.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{17cm}{!}{\includegraphics{0400fig02.ps}}}\end{figure}$ Figure 2: The reduced 2-5-11.6 $\mu$ m PHT-S spectra of the sample stars.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{17cm}{!}{\includegraphics{0400fig03.ps}}}\end{figure}$ Figure 3: The reduced 5-15 $\mu$ m CAM spectra of the sample stars.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig04.ps}}}\end{figure}$ Figure 4: The PAH feature at 6.2 micron of HD 100546 in the SWS spectrum (dashed line) and in the PHT-S spectrum (full line).
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.2cm}{!}{\includegraphics{0400fig05.ps}}}\end{figure}$ Figure 5: Diagram based on van Boekel et al. (2003). The ratio $L_{{\rm NIR}}/L_{{\rm IR}}$ is plotted versus the non-color-corrected IRAS [12]-[60] color. The dashed line represents $L_{{\rm NIR}}/L_{{\rm IR}} = ([12]{-}[60]) + 0.9$ . Objects on the left-hand side of this empirical line are defined to be group II members (open diamonds), sources on the right side are either group I (filled diamonds) or group III (squares) members.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{17.2cm}{!}{\includegraphics{0400fig06.ps}}}\end{figure}$ Figure 6: The spectral energy distributions of the sample stars. The squares are the observed photometric data from the literature with error bars. The solid line is the reddened Kurucz model for the stellar photosphere, fitted to the measured UV-optical photometry. The ISO spectra are plotted in the SEDs as well (noisy solid line).
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.4cm}{!}{\includegraphics{0400fig07.ps}}}\end{figure}$ Figure 7: The LF/CF ratio of PAH 7.7 micron versus PAH 6.2 micron. The filled diamonds with error bars indicate detected features, arrows represent upper limits.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.4cm}{!}{\includegraphics{0400fig08.ps}}}\end{figure}$ Figure 8: Similar plot as Fig. 7. The LF/CFratio of PAH 6.2 micron versus PAH 3.3 micron.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.4cm}{!}{\includegraphics{0400fig09.ps}}}\end{figure}$ Figure 9: The logarithm of the ratio of the line fluxes of the PAH features at 8.6 and 6.2 micron $\log~(LF_{8.6}/LF_{6.2})$ versus the logarithm of the ratio of the line fluxes of the PAH features at 3.3 and 6.2 micron $\log~(LF_{3.3}/LF_{6.2})$ for all program stars. The filled diamonds with error bars indicate detected features, arrows indicate upper limits. The full line represents the line fluxes of MWC 1080 for variable extinction.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig10.ps}}}\end{figure}$ Figure 10: The LF/CF ratios of the amorphous 10 micron silicate feature (Si 9.7) versus the PAH 6.2 micron feature. Diamonds with error bars indicate detected features, arrows represent upper limits. Sources with the 10 micron feature in absorption have a negative LF/CF ratio.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig11.ps}}}\end{figure}$ Figure 11: The cumulative histogram of the PF/CF for the amorphous 10 micron silicate feature. The 24 sample stars in which this feature is in emission are included in this plot. The lower filled part of the bars represents group I sources, the upper part group II sources.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig12.ps}}}\end{figure}$ Figure 12: Same type of plot as Fig. 9. The logarithm of the ratio of the line fluxes of the PAH features at 3.3 and 6.2 micron $\log~(LF_{3.3}/LF_{6.2})$ versus the logarithm of the ratio of the line fluxes of the features at 11 and 6.2 micron $\log~(LF_{11}/LF_{6.2})$ . Again, the full line represents the line fluxes of MWC 1080 for variable interstellar extinction.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig13.ps}}}\end{figure}$ Figure 13: The FWHM of the 11 micron feature versus the logarithm of the ratio of the line fluxes of the features at 11 and 6.2 micron $\log~(LF_{3.3}/LF_{6.2})$ . The dashed line represents the average FWHM (0.214 micron) when excluding the 4 outliers.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig14.ps}}}\end{figure}$ Figure 14: The peak position of the detected 11 micron features versus the ratio of the line fluxes of the 11 micron feature over the 6.2 PAH feature $\log~(LF_{11}/LF_{6.2})$ . The dashed line at 11.233 micron indicates the mean peak position of the 11 micron feature.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig15.ps}}}\end{figure}$ Figure 15: The LF/CF ratios of the amorphous 10 micron silicate feature (Si 9.7) versus the 11 micron feature. Diamonds with error bars indicate detected features, arrows represent upper limits. Sources with the 10 micron feature in absorption have a negative LF/CF ratio.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig16.ps}}}\end{figure}$ Figure 16: The inverted spectrum of Z CMa, and the emission band spectra of HD 144432 and HD 163296. For Z CMa, the figure shows the inverted continuum-divided, continuum-subtracted flux $[\mathcal{F}_{\rm cont}(\lambda) - \mathcal{F}(\lambda)]/ \mathcal{F}_{\rm cont}(\lambda)$ . The other two spectra display the continuum-subtracted flux. All three spectra are normalized to a peak flux of 1. An additional offset was applied for the sake of clarity. The dashed line represents $\lambda = 11.3~\mu$ m.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig17.ps}}}\end{figure}$ Figure 17: The Hertzsprung-Russel diagram for the sample stars. The plotting symbols are proportional to the PAH luminosity. Filled diamonds indicate detected emission, open symbols represent upper limits. The full lines indicate the PMS evolutionary tracks of stars with masses M = 1.5, 2, 3 and 5 $M_{\odot }$ from bottom to top; the dashed and dotted lines represent respectively the ZAMS and the MS (Bernasconi 1996).
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig18.ps}}}\end{figure}$ Figure 18: Similar plot as Fig. 17. The plotting symbols are proportional to the peak-over-continuum flux of the amorphous 10 micron silicate emission feature.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig19.ps}}}\end{figure}$ Figure 19: The logarithm of the IR-excess luminosity $\log~(L_{{\rm exc}})$ versus the logarithm of the absorbed luminosity $\log~(L_{{\rm abs}})$ . Filled diamonds represent group I, open diamonds group II and squares group III sources. The dashed line is the first bisector. In the left upper corner, the typical error bars are represented by a cross.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig20.ps}}}\end{figure}$ Figure 20: The PAH-over-UV luminosity $\log~(L_{{\rm PAH}}/L_{{\rm uv}})$ versus the intensity of the UV radiation field $\log~(L_{{\rm uv}})$ . The PAH luminosity is the sum of the luminosities of the PAH features at 3.3, 6.2, 7.7 and 8.6 micron. In the left upper corner, the cross indicates the typical errors. Filled diamonds refer to group I, open diamonds to group II and squares to group III objects. Arrows represent upper limits. The dashed line represents the best linear fit to the data: $\log~(L_{{\rm PAH}}/L_{{\rm uv}}) = -0.395 \log~(L_{{\rm uv}}) - 1.99$ .
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig21.ps}}}\end{figure}$ Figure 21: The PAH 7.7 micron luminosity $\log~(L_{{\rm PAH 7.7}})$ versus the excess at 60 micron (in magnitudes). Filled diamonds represent group I, open diamonds group II and squares group III sources. Small symbols indicate undetected features, arrows stand for upper limits. In the left upper corner the typical error bars are displayed.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig22.ps}}}\end{figure}$ Figure 22: Similar plot as Fig. 5. The plotting symbols are scaled proportional to the strength ( $\sum LF/CF$ ) of the PAH features at 3.3, 6.2, 7.7 and 8.6 micron. The outer limit of the partially filled plotting symbol represents the upper limit for the strength; the filled inner part refers to the part that was actually detected. Diamonds represent group I and group II sources, squares group III objects.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig23.ps}}}\end{figure}$ Figure 23: Similar plot as Fig. 22 for the amorphous 10 micron silicate feature. The plotting symbols are scaled proportional to the LF/CF ratio of the feature. The filled diamonds indicate stars with a detected 10 micron emission feature, the open diamonds indicate upper limits.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig24.ps}}}\end{figure}$ Figure 24: Similar plot as Fig. 5. The filled symbols indicate UXORs, the open symbols are the other HAEBEs in this sample. The 3 UXOR stars that display clear PAH emission are VX Cas, HD 34282 and RR Tau.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{7cm}{!}{\includegraphics{0400fig25.ps}}}\end{figure}$ Figure 25: The amorphous 10 micron silicate band for 14 of the sample stars. The figure shows the continuum-subtracted flux $\mathcal{F}(\lambda) - \mathcal{F}_{{\rm cont}}(\lambda)$ , which was divided by the average value of the underlying continuum $\langle\mathcal{F}_{{\rm cont}}(\lambda)\rangle$ . The spectra of the stars are sorted by increasing peak-over-continuum flux from a to n: a- R CrA; b- HR 5999; c- V376 Cas; d- HD 200775; e- T CrA; f- VX Cas; g- HD 104237; h- BF Ori; i- HD 31648; j- HD 163296; k- SV Cep; l- HD 144432; m- UX Ori; n- AB Aur. For clarity, the zero levels of the 14 spectra are shifted.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{7cm}{!}{\includegraphics{0400fig26.ps}}}\end{figure}$ Figure 26: The FWHM of the amorphous 10 micron silicate feature versus the peak-over-continuum flux ratio PF/CF. Filled and open diamonds refer to group I and group II sources respectively. The dashed line represents the best fit to the data; ${\it FWHM} = -0.38 \times {\rm PF/CF} + 3.67$ . The typical error bar is indicated in the upper left corner.
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In the text

$\begin{figure} \par\rotatebox{0}{\resizebox{17.2cm}{!}{\includegraphics{0400fig01.ps}}}\end{figure}$	Figure 1: The reduced 2.4-15 $\mu$ m SWS spectra of the sample stars.
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$\begin{figure} \par\rotatebox{0}{\resizebox{17cm}{!}{\includegraphics{0400fig02.ps}}}\end{figure}$	Figure 2: The reduced 2-5-11.6 $\mu$ m PHT-S spectra of the sample stars.
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$\begin{figure} \par\rotatebox{0}{\resizebox{17cm}{!}{\includegraphics{0400fig03.ps}}}\end{figure}$	Figure 3: The reduced 5-15 $\mu$ m CAM spectra of the sample stars.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig04.ps}}}\end{figure}$	Figure 4: The PAH feature at 6.2 micron of HD 100546 in the SWS spectrum (dashed line) and in the PHT-S spectrum (full line).
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$\begin{figure} \par\rotatebox{0}{\resizebox{17.2cm}{!}{\includegraphics{0400fig06.ps}}}\end{figure}$	Figure 6: The spectral energy distributions of the sample stars. The squares are the observed photometric data from the literature with error bars. The solid line is the reddened Kurucz model for the stellar photosphere, fitted to the measured UV-optical photometry. The ISO spectra are plotted in the SEDs as well (noisy solid line).
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.4cm}{!}{\includegraphics{0400fig07.ps}}}\end{figure}$	Figure 7: The LF/CF ratio of PAH 7.7 micron versus PAH 6.2 micron. The filled diamonds with error bars indicate detected features, arrows represent upper limits.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.4cm}{!}{\includegraphics{0400fig08.ps}}}\end{figure}$	Figure 8: Similar plot as Fig. 7. The LF/CFratio of PAH 6.2 micron versus PAH 3.3 micron.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig10.ps}}}\end{figure}$	Figure 10: The LF/CF ratios of the amorphous 10 micron silicate feature (Si 9.7) versus the PAH 6.2 micron feature. Diamonds with error bars indicate detected features, arrows represent upper limits. Sources with the 10 micron feature in absorption have a negative LF/CF ratio.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig11.ps}}}\end{figure}$	Figure 11: The cumulative histogram of the PF/CF for the amorphous 10 micron silicate feature. The 24 sample stars in which this feature is in emission are included in this plot. The lower filled part of the bars represents group I sources, the upper part group II sources.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig12.ps}}}\end{figure}$	Figure 12: Same type of plot as Fig. 9. The logarithm of the ratio of the line fluxes of the PAH features at 3.3 and 6.2 micron $\log~(LF_{3.3}/LF_{6.2})$ versus the logarithm of the ratio of the line fluxes of the features at 11 and 6.2 micron $\log~(LF_{11}/LF_{6.2})$ . Again, the full line represents the line fluxes of MWC 1080 for variable interstellar extinction.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig13.ps}}}\end{figure}$	Figure 13: The FWHM of the 11 micron feature versus the logarithm of the ratio of the line fluxes of the features at 11 and 6.2 micron $\log~(LF_{3.3}/LF_{6.2})$ . The dashed line represents the average FWHM (0.214 micron) when excluding the 4 outliers.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig14.ps}}}\end{figure}$	Figure 14: The peak position of the detected 11 micron features versus the ratio of the line fluxes of the 11 micron feature over the 6.2 PAH feature $\log~(LF_{11}/LF_{6.2})$ . The dashed line at 11.233 micron indicates the mean peak position of the 11 micron feature.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig15.ps}}}\end{figure}$	Figure 15: The LF/CF ratios of the amorphous 10 micron silicate feature (Si 9.7) versus the 11 micron feature. Diamonds with error bars indicate detected features, arrows represent upper limits. Sources with the 10 micron feature in absorption have a negative LF/CF ratio.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig18.ps}}}\end{figure}$	Figure 18: Similar plot as Fig. 17. The plotting symbols are proportional to the peak-over-continuum flux of the amorphous 10 micron silicate emission feature.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig19.ps}}}\end{figure}$	Figure 19: The logarithm of the IR-excess luminosity $\log~(L_{{\rm exc}})$ versus the logarithm of the absorbed luminosity $\log~(L_{{\rm abs}})$ . Filled diamonds represent group I, open diamonds group II and squares group III sources. The dashed line is the first bisector. In the left upper corner, the typical error bars are represented by a cross.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig21.ps}}}\end{figure}$	Figure 21: The PAH 7.7 micron luminosity $\log~(L_{{\rm PAH 7.7}})$ versus the excess at 60 micron (in magnitudes). Filled diamonds represent group I, open diamonds group II and squares group III sources. Small symbols indicate undetected features, arrows stand for upper limits. In the left upper corner the typical error bars are displayed.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig23.ps}}}\end{figure}$	Figure 23: Similar plot as Fig. 22 for the amorphous 10 micron silicate feature. The plotting symbols are scaled proportional to the LF/CF ratio of the feature. The filled diamonds indicate stars with a detected 10 micron emission feature, the open diamonds indicate upper limits.
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$\begin{figure} \par\rotatebox{0}{\resizebox{8.3cm}{!}{\includegraphics{0400fig24.ps}}}\end{figure}$	Figure 24: Similar plot as Fig. 5. The filled symbols indicate UXORs, the open symbols are the other HAEBEs in this sample. The 3 UXOR stars that display clear PAH emission are VX Cas, HD 34282 and RR Tau.
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$\begin{figure} \par\rotatebox{0}{\resizebox{7cm}{!}{\includegraphics{0400fig26.ps}}}\end{figure}$	Figure 26: The FWHM of the amorphous 10 micron silicate feature versus the peak-over-continuum flux ratio PF/CF. Filled and open diamonds refer to group I and group II sources respectively. The dashed line represents the best fit to the data; ${\it FWHM} = -0.38 \times {\rm PF/CF} + 3.67$ . The typical error bar is indicated in the upper left corner.
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