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==> In this proposal, more time is being requested for TMONTMER.1103FEAT
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We propose to observe the interaction of X-rays from young stars in
molecular clouds with the surrounding dust.  For T Tauri stars in the
outer regions of molecular clouds, the signature of this interaction is
predicted to be the disappearance of PAH features within 0.01 to 0.1 pc
from the star. For Herbig Ae/Be stars, which are usually surrounded by
dense circumstellar dust, the signature of X-ray interaction may be the
disappearance of PAH emission in the close vicinity of the star. From
recent X-ray data provided by the ROSAT and ASCA satellites, we select
4 T Tauri stars in the Rho Oph cloud, and 6 Herbig Ae/Be stars with a
wide range of X-ray luminosities. We also select 2 X-ray emitting
dense cores associated with the Monoceros and Rosette molecular
clouds. We use the imaging properties of ISOCAM (using 5 to 8 filters
centered on UIB and silicate features and their references) to study
the dependence of the UIB emission as a function of distance to the
X-ray source. The results should constrain both our knowledge of the
composition of the smallest dust grains, and of the heating of dust by
hard radiation.
The present proposal is a follow-up of a previously accepted proposal
(PROPID = 1103FEAT, Priority 1), which has been done using 3 filters
around 6 mum (LW4 to LW6). A preliminary analysis of the data, recently
made available to us, shows that flux ratios obtained with these
filters are indeed tracers of irradiation effects, justifying the
present request for more observations at other wavelengths.