All Figures

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9697fig1.eps}\end{figure}$ Figure 1: Wavelength dependence of the normalised absorption efficiency factor [ $Q_{\rm abs}(\lambda)/Q_{\rm abs}(8.2~\mu{\rm m})-1$ ] for compact spheres consisting of astrosil. The effect of variation of the silicate emission shape with the particle size is illustrated. The observational profile of the T Tauri star Tr 37 13-157 (Sicilia-Aguilar et al. 2007) is shown for comparison. Note that this profile is not continuum subtracted.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9697fig2.eps}\end{figure}$ Figure 2: Wavelength dependence of the normalised absorption efficiency factor ( upper panel) and mass absorption coefficient ( lower panel) for layered spheres with $r_{\rm s,~compact}=0.1~\mu{\rm m}$ . The particles consist of amorphous carbon (Be1), amorphous silicate with olivine composition (MgFeSiO₄), and vacuum. The volume fraction of components $V_i /V_{\rm total}$ is indicated. The particles are of the same mass ( $V_{\rm Be1}/V_{\rm solid}=V_{\rm Be1}/(V_{\rm Be1}+V_{\rm MgFeSiO_4})=0.2$ ), but of different porosity. The effect of variation of the silicate emission shape with the particle porosity is illustrated.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9697fig3.eps}\end{figure}$ Figure 3: The same as in Fig. 2 ( upper panel) but now for particles of porosity ${\cal P}=0.9$ . The particles are of the same porosity but of slightly different mass. The value of $V_{\rm Be1}/V_{\rm solid}$ varies from 0.1 to 0.3. The effect of variation of the silicate emission shape with the volume fraction of carbon is illustrated. The observational profile of the T Tauri star Tr 37 13-157 is shown for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9697fig4.eps}\end{figure}$ Figure 4: The observational normalised profile of the 10 $\mu {\rm m}$ feature for the Herbig Ae/Be star AB Aur (van Boekel et al. 2005; continuum is subtracted). The best fit profiles are shown for particles containing amorphous carbon in the form Be1 (dashed line) and AC1 (circles). The values of particle porosity ${\cal P}$ and fractional amount of carbon $V_{\rm Be1}/V_{\rm solid}$ are indicated.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{9697fig5.eps}\end{figure}$ Figure 5: Wavelength dependence of the mass absorption coefficient for compact and layered spheres with $r_{\rm s,~compact}=0.1~\mu{\rm m}$ . The particles consist of crystalline olivine and vacuum ( upper panel), amorphous silicate, crystalline olivine, and vacuum ( middle panel) and amorphous carbon, amorphous silicate, crystalline olivine, and vacuum ( lower panel). The volume fraction of crystalline olivine and Be1 is indicated. The position of peaks is marked. The thick solid line at the lower panel shows the mass absorption coefficient for the mixture of compact grains (external mixing) with volume fractions of constituents corresponding to solid curve (internal mixing). The effect of variation of crystalline resonances with particle porosity and composition is illustrated.
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In the text