Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=14.7cm,clip]{0178fig1.ps}\end{figure}$ Figure 1: Observed visual to millimeter spectral energy distributions of the programme stars. Dereddened fluxes, taken from the literature, are shown as diamonds, while the curves in grey give SWS and LWS spectra from the infrared satellite ISO. The solid line represents the sum of the stellar photosphere (dotted line) and the best fit DDN model, taken from Dominik et al. (2003) for all stars except KK Oph, where a new model was constructed, and 51 Oph. For 51 Oph no fit of the spectral energy distribution by a DDN-type disk model was possible (see text).
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In the text

$\begin{figure} \par\includegraphics[height=17cm,width=11.8cm,angle=90,clip]{0178fig2.ps}\end{figure}$ Figure 2: Observed 7.5-13.5 $\mu$ m spectra of the programme stars. Note the large range in silicate band shapes, and the presence of crystalline silicates (shoulder at 11.3 $\mu$ m) in some objects. PAH bands at 7.9, 8.6 and 11.3 $\mu$ m are prominent in HD 100546 and HD 179218. The MIDI spectra are indicated in black. TIMMI 2 spectra are drawn in grey. In order to allow a good comparison of the spectral shapes, scaling factors ( from top left to bottom right: $\times$ 1.08, $\times$ 1.15, $\times$ 1.25, $\times$ 0.92, $\times$ 0.75, $\times$ 0.90, $\times$ 1.05) have been applied to the TIMMI 2 spectra. Given the fact that the absolute level of the TIMMI2 data was simply determined by adjusting to IRAS results, the level of agreement in shape and absolute value between these fully independent sets of spectra gives confidence to both.
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{0178fig3.ps}\end{figure}$ Figure 3: Isophotal representation of the deconvolved 8.7 $\mu$ m image of HD 100546. The contour levels are linearly spaced from 100% to 25% for the fourth root of the image brightness I, i.e. they are $\propto$ I^1/4. The last contour therefore is equivalent to 0.4% of the maximum of I. The orientation of the 0.5'' slit during the exposure was at position angle 140 $^{\circ }$ , i.e. along the long axis of the object.
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In the text

$\begin{figure} \par\includegraphics[width=17.8cm,width=12.5cm,angle=90,clip]{0178fig4.ps}\end{figure}$ Figure 4: The observed visibilities of the programme stars with the model predictions overplotted. These models were made with the sole purpose of fitting the spectral energy distribution and do not contain any feedback from the visibility observations. Three model visibility curves are shown: two referring to the inclination used in the SED fitting and calculated for a cut along the long axis (broken line) and along the short axis (solid line) respectively, while the dotted line is the prediction for a pole-on view. The errors give the standard deviation of the visibility results obtained for one source with different calibrators.
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{0178fig5.ps}\end{figure}$ Figure 5: Correlation between the mid-infrared spectral slope (taken from IRAS as -2.5 $\log~$ ( $F_{\nu }$ (12 $\mu$ m)/ $F_{\nu }$ (25 $\mu$ m)) and the half-light radius corresponding to the observed visibilities at 12.5 $\mu$ m. The errors reflect the uncertainty in IRAS fluxes and visibility measurements; the resulting uncertainty in size may be optimistic. The largest sources are those with the reddest mid-infrared spectral distribution, and these were also classified as group I. For HD 142527 the arrow shows the correction for contamination of the IRAS colour by an unrelated very red nearby source (see text).
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In the text