Group O3 - transition spectra

  
Figure 8.5: Flux-calibrated spectra of Group O3 sources with a transition feature. Fluxes are in Wm^-2µm^-1

  
Figure 8.6: Continuum-subtracted spectra of Group O3 sources with a transition feature.

Following the broad feature phase, the dust develops the ``silicate'' feature at 9.7µm, whilst also strengthening the broad underlying feature, so that the spectra appear to have a fairly weak peak at 9.7µm, with a wing out to about 11.5-12.0µm. This group comprises only three sources: Y Aqr, RS Cnc and W Eri, the flux-calibrated spectra of which can be seen in Fig. 8.5 and the continuum-subtracted spectra in Fig. 8.6. In the case of RS Cnc, the broad feature is quite smooth with just the 9.8µm bump showing. This bump is too broad to be incomplete ozone cancellation, and is therefore judged to be real and probably due to the onset of magnesium silicate formation. From this we deduce that the dust evolution has progressed at least as far as forsterite formation, and possibly further to ferromagnesian olivines.

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