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Abstract: We investigate the nature of the innermost regions of seven circumstellardisks around pre-main-sequence stars. Our object sample contains disksapparently at various stages of their evolution. Both single stars andspatially resolved binaries are considered. In particular, we search for innerdisk gaps as proposed for several young stellar objects. When analyzing theunderlying dust population in the atmosphere of circumstellar disks, the shapeof the 10um feature is investigated. We performed interferometric observationsin N band 8-13um with MIDI using baseline lengths of between 54m and 127m. Thedata analysis is based on radiative-transfer simulations using the Monte Carlocode MC3D by modeling simultaneously the SED, N band spectra, andinterferometric visibilities. Correlated and uncorrelated N band spectra arecompared to investigate the radial distribution of the dust composition of thedisk atmosphere. Spatially resolved mid-infrared emission was detected in allobjects. For four objects, the observed N band visibilities and correspondingSEDs could be simultaneously simulated using a parameterized active disk-model.For the more evolved objects of our sample, a purely passive disk-modelprovides the closest fit. The visibilities inferred for one source allow thepresence of an inner disk gap. For another object, one of two visibilitymeasurements could not be simulated by our modeling approach. All uncorrelatedspectra reveal the 10um silicate emission feature. In contrast to this, somecorrelated spectra of the observations of the more evolved objects do not showthis feature, indicating a lack of small silicates in the inner versus theouter regions of these disks. We conclude from this observational result thatmore evolved dust grains can be found in the more central disk regions.



Author: A. A. Schegerer, S. Wolf, C. A. Hummel, S. P. Quanz, A. Richichi

Source: https://arxiv.org/



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