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Observations of TTauri stars are part of the Guaranteed Time Observations (GTO) of the MID-infrared Interferometric instrument (MIDI) operated by ESO at the VLTI. Here we give a brief overview of the preliminary results obtained for some of the brighter TTauri stars that are in the reach of MIDI in the present state of the VLTI without external fringe tracking [ABSTRACT FROM AUTHOR]

We report on interferometry of the high-mass young stellar object M8E-IR performed with MIDI at the ESO-VLTI. The observations were carried out using the UT1-UT3 and UT2-UT3 baselines. The visibilities in the 8...13 micron range derived from the spectrally dispersed fringes indicate the presence of circumstellar emission presumably originating from warm dust. We resolve the MIR emission of M8E-IR and derive an extension between 15 and 30mas which correspond to linear sizes of 30-50AU at the distance of the source. These are the scales at which circumstellar disks around massive stars are expected. We discuss the properties of the dust envelope based on the results of our preliminary model and in the context of supplementary NACO observations. [ABSTRACT FROM AUTHOR]

We present interferometric observations of the Be star 51 Ophiuchi. These observations were obtained during the science demonstration phase of the MIDI instrument at the VLTI in June 2003. The baseline UT1-UT3 was used, corresponding to 102 m. It is currently known that this object presents a circumstellar dust and gas disk that shows a very different composition from other Herbig Ae disks. The nature of the 51 Oph system is still a mystery to be solved. Observations with MIDI at the VLTI allowed us to reach high-angular resolution (20 mas). We have several uv points that allowed us to constrain the disk model. We have modeled 51 Oph visibilities and were able to constrain the size and geometry of the 51 Oph circumstellar disk. [ABSTRACT FROM AUTHOR]

The composition and spatial distribution of circumstellar dust in young and old stars can be used as a probe of the physical and chemical processes that take place. Such studies require a modest spectral resolution in combination with high spatial resolution and large collecting area, now for the first time provided by the new generation of optical interferometers. This review discusses some early results from the VLT Interferometer in the area of circumstellar dust. [ABSTRACT FROM AUTHOR]

The core of the nebula surrounding Eta Carinae has recently been observed with VLT/NACO, VLTI/VINCI, VLTI/MIDI and VLTI/AMBER in order to spatially and spectrally constrain the warm dusty environment and the central object. Narrow-band images at 3.74 μm and 4.05 μm reveal the structured butterfly-shaped dusty environment close to the central star with an unprecedented spatial resolution of about 60 mas. VINCI has resolved the present-day stellar wind of Eta Carinae on a scale of several stellar radii owing to the spatial resolution of the order of 5 mas (~ 11 AU). The VINCI observations show that the object is elongated with a de-projected axis ratio of approximately 1.5. Moreover the major axis is aligned with that of the large bipolar nebula that was ejected in the 19th century. Fringes have also been obtained in the Mid-IR with MIDI using baselines of 75m. A peak of correlated flux of 100 Jy is detected 0.3" south-east from the photocenter of the nebula at 8.7 μm is detected. This correlated flux is partly attributed to the central object but it is worth noting that at these wavelengths, virtually all the 0.5" x 0.5" central area can generate detectable fringes witnessing the large clumping of the dusty ejecta. These observations provide an upper limit for the SED of the central source from 3.8 μm to 13.5 μm and constrain some parameters of the stellar wind which can be compared to Hillier's model. Lastly, we present the great potential of the AMBER instrument to study the numerous near-IR emissive lines from the star and its close vicinity. In particular, we discuss its ability to detect and follow the faint companion. [ABSTRACT FROM AUTHOR]

We present the results of the first mid-infrared interferometric observations of the Mira variable RRSco with the VLTI/MIDI, together with K-band observations using VLTI/VINCI.The uniform-disk diameter was found to be 18mas between 8 and 10μm, while it gradually increases at wavelengths longer than 10μm to reach 24mas at 13μm.These uniform-disk diameters in the mid-infrared are significantly larger than the K-band uniform-disk diameter of 10.2±0.5 mas measured using VLTI/VINCI, three weeks after the MIDI observations. Our model calculations show that optically thick emission from a warm molecular envelope consisting of H2O and SiO can cause the apparent mid-infrared diameter to be much larger than the continuum diameter, and this can explain the mid-infrared angular sizes roughly twice as large as that measured in the K band. The observed increase of the uniform-disk diameter longward of 10μm can be explained by an optically thin dust shell consisting of corundum and silicate grains. [ABSTRACT FROM AUTHOR]

VV CrA VV CrA is one of the rare binary systems harbouring a so-called infrared companion (see contribution by Th. Ratzka & Ch. Leinert). While in 1987 this companion dominated at all infrared wavelengths, it is now fainter than the primary even in the N-band. This ‘fading' may provide the chance to reveal the underlying properties causing the existence of infrared companions. In the following we will present a preliminary interpretation of the interferometric observations obtained with MIDI that provide insights into the geometry of the dusty environment. They seem to favour a geometrical explanation for the different apppearances of the two components of VV CrA. [ABSTRACT FROM AUTHOR]