The Herbig Ae star HD 139614 is a group-Ib object, which featureless SED indicates disk flaring and a possible pre-transitional evolutionary stage. We present mid- and near-IR interferometric results collected with MIDI, AMBER and PIONIER with the ai
m of constraining the spatial structure of the 0.1-10 AU disk region and assess its possible multi-component structure. A two-component disk model composed of an optically thin 2-AU wide inner disk and an outer temperature-gradient disk starting at 5.6 AU reproduces well the observations. This is an additional argument to the idea that group-I HAeBe inner disks could be already in the disk-clearing transient stage. HD 139614 will become a prime target for mid-IR interferometric imaging with the second-generation instrument MATISSE of the VLTI.
We explore the scientific potential of next-generation high-angular resolution optical imager to study the AGN/Host connection. The availability of a significant number of X-raying AGN with natural guide stars, allowing for adaptive optics at optical
wavelengths, offers an interesting perspective to complement high-resolution work currently done in the near-infrared.
A new class of pre-main sequence objects has been recently identified as pre-transitional disks. They present near-infrared excess coupled to a flux deficit at about 10 microns and a rising mid-infrared and far-infrared spectrum. These features sugge
st a disk structure with inner and outer dust components, separated by a dust-depleted region (or gap). We here report on the first interferometric observations of the disk around the Herbig Ae star HD 139614. Its infrared spectrum suggests a flared disk, and presents pre-transitional features,namely a substantial near-infrared excess accompanied by a dip around 6 microns and a rising mid-infrared part. In this framework, we performed a study of the spectral energy distribution (SED) and the mid-infrared VLTI/MIDI interferometric data to constrain thespatial structure of the inner dust disk region and assess its possibly multi-component structure. We based our work on a temperature-gradient disk model that includes dust opacity. While we could not reproduce the SED and interferometric visibilities with a one-component disk, a better agreement was obtained with a two-component disk model composed of an optically thin inner disk extending from 0.22 to 2.3 au, a gap, and an outer temperature-gradient disk starting at 5.6 au. Therefore, our modeling favors an extended and optically thin inner dust component and in principle rules out the possibility that the near-infrared excess originates only from a spatially confined region. Moreover, the outer disk is characterized by a very steep temperature profile and a temperature higher than 300 K at its inner edge. This suggests the existence of a warm component corresponding to a scenario where the inner edge of the outer disk is directly illuminated by the central star. This is an expected consequence of the presence of a gap, thus indicative of a pre-transitional structure.
Observations at mas-resolution scales and high dynamic range hold a central place in achieving, for instance, the spectroscopic characterization of exo-Earths or the detailed mapping of their protoplanetary disc birthplace. Ground or space-based mult
i-aperture infrared interferometry is a promising technique to tackle these goals. But significant efforts still need to be undertaken to achieve a simplification of these instruments if we want to combine the light from a large number of telescopes. Integrated-optics appears as an alternative to the current conventional designs, especially if its use can be extended to a higher number of astronomical bands. This article reports for the first time the experimental demonstration of the feasibility of an integrated-optics approach to mid-infrared beam combination for single-mode stellar interferometry. We have fabricated a 2-telescope beam combiner prototype integrated on a substrate of chalcogenide glasses, a material transparent from 1 to 14 um. We have developed laboratory tools to characterize the modal properties and the interferometric capabilities of our device. We obtain fringes at 10 um and measure a mean contrast V=0.981 pm 0.001 with high repeatability over one week and high stability over 5h. We show experimentally - as well as on the basis of modeling considerations - that the component has a single-mode behavior at this wavelength, which is essential to achieve high-accuracy interferometry. From previous studies, the propagation losses are estimated to 0.5 dB/cm for such components. We also discuss possible issues that may impact the interferometric contrast. The IO beam combiner performs well at 10. We also anticipate the requirement of a better matching between the numerical apertures of the component and the (de)coupling optics to optimize the total throughput. The next step foreseen is the achievement of wide-band interferograms.
