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International audienceIRC+10216 is located at the tip of the asymptotic giant branch of the Hertzsprung-Russell diagram in a transition phase toward the post-asymptotic giant branch stage. Its study contributes to our knowledge of the late stage of stellar evolution of low- and intermediate-mass stars, when the circumstellar matter begins to adopt the asymmetric or bipolar forms commonly found in planetary nebulae. Using the NAOS-CONICA (NACO) adaptive optics system, we have mapped the circumstellar environment of IRC+1O216 at several wavelengths and three different epochs. The NACO study provides high-resolution and high-dynamic-range information on the different features displayed by the circumstellar envelope: clumpiness and a peanut- or bipolar-like shape at small scales. The link between the inner regions and the spherical-like shells observed at large scales is displayed in these high-dynamic-range data

MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory. The related science case study demonstrates the enormous capability of a new generation mid-infrared beam combiner. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. MIDI is a very successful instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar environments by using a wide mid-infrared band coverage extended to L, M and N spectral bands. The four beam combination of MATISSE provides an efficient UV-coverage : 6 visibility points are measured in one set and 4 closure phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.

Abstract. Models of stationary dust-driven winds of late-type stars are investigated. The flow is described successively using three models which couple, in spherical symmetry, the grain-gas dynamics in a self-consistent way with radiative transfer. Complete radiative transfer including multiple scattering, absorption and thermal emission is taken into account to determine the temperature of dust grains which in turn governs their thermal emission. The medium is not necessarily optically thin. The first model is used to check one classical hypothesis, that where the gas and the grains expand at the same velocity, the flow is described by a one-fluid model. This model is then improved in a second model, to include complete momentum coupling between gas and grains by friction. Finally, a third model includes grains and gas coupled by friction as well as the effects of inertial force on grains. By means of a numerical iteration, dynamics and radiative transfer are coupled in order to achieve a self-consistent solution in all cases. Even for fairly low non-zero optical depths, coupling of radiation with dynamics is found to be important for wind models which are all highly sensitive to input data. In conclusion, approximations (position and momentum coupling) for the dynamics should be relaxed.

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