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While the search for exoplanets around main sequence stars more massive than the Sun have found relatively few such objects, surveys performed around giant stars have led to the discovery of more than 30 new exoplanets. The interest in studying planet hosting giant stars resides in the possibility of investigating planet formation around stars more massive than the Sun. Masses of isolated giant stars up to now were only estimated from evolutionary tracks, which led to different results depending on the physics considered. To calibrate the theory, it is therefore important to measure a large number of giant star diameters and masses as much as possible independent of physical models. We aim in the determination of diameters and effective temperatures of 5 giant stars, one of which is known to host a planet. AMBER/VLTI observations with the ATs were executed in low resolution mode on 5 giant stars. In order to measure high accurate calibrated squared visibilities, a calibrator-star-calibrator observational sequence was performed. We measured the uniform disk and limb-darkened angular diameters of 4 giant stars. The effective temperatures were also derived by combining the bolometric luminosities and the interferometric diameters. Lower effective temperatures were found when compared to spectroscopic measurements. The giant star HD12438 was found to have an unknown companion star at an angular separation of ~ 12 mas. Radial velocity measurements present in the literature confirm the presence of a companion with a very long orbital period (P ~ 11.4 years).}
AMBER is the first near infrared focal instrument of the VLTI. It combines three telescopes and produces spectrally resolved interferometric measures. This paper discusses some preliminary results of the first scientific observations of AMBER with th
Aims. We study the enigmatic B[e] star MWC 300 to investigate its disk and binary with milli-arcsecond-scale angular resolution. Methods. We observed MWC 300 with the VLTI/AMBER instrument in the H and K bands and compared these observations with tem
The rapidly rotating primary component of Regulus A system has been observed, for the first time, using the technique of differential interferometry at high spectral resolution. The observations have been performed across the Br$_gamma$ spectral line
Massive stars deeply influence their surroundings by their luminosity and the injection of kinetic energy. So far, they have mostly been studied with spatially unresolved observations, although evidence of geometrical complexity of their wind are num
The pre-main sequence (PMS) star ABDorA is the main component of the quadruple system ABDoradus. The precise determination of the mass and photometry of the close companion to ABDorA, ABDorC, has provided an important benchmark for calibration of the