EAS Publications Series

Issue		EAS Publications Series Volume 22, 2006 Astronomy with High Contrast Imaging III: Instrumental Techniques, Modeling and Data Processing
Page(s)		379 - 388
DOI		10.1051/eas:2006143
Published online		13 October 2006

Astronomy with High Contrast Imaging III: Instrumental Techniques, Modeling and Data Processing
M. Carbillet, A. Ferrari and C. Aime (eds)
EAS Publications Series, 22 (2006) 379-388
DOI: 10.1051/eas:2006143

Differential Interferometry with the AMBER/VLTI instrument: Description, performances and illustration

F. Millour^{1, 2}, M. Vannier³, R.G. Petrov¹, O. Chesneau⁴, L. Dessart⁵ and P. Stee⁴

¹ Laboratoire Universitaire d'Astrophysique de Nice, UMR 6525, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 02, France
² Laboratoire d'Astrophysique de Grenoble, UMR 5571 Université Joseph Fourier/CNRS, BP. 53, 38041 Grenoble Cedex 9, France
³ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁴ Laboratoire Gemini, UMR 6203 Observatoire de la Côte d'Azur/CNRS, Avenue Copernic, 06130 Grasse, France
⁵ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA

(Published online 13 October 2006)

Abstract
AMBER is the near I.R. focal instrument of the VLTI. It recombines 3 beams simultaneously and has spectral resolution capability allowing simultaneous spectrum, visibilities, differential visibilities, closure phase and differential phases measurements on the observed sources. We present here the general formalism used on AMBER in order to compute differential phases and differential visibilities, in complement to the article of Tatulli et al. (2006). We show that these differential observables have precisions close to the fundamental noises and we present an illustration of model-fitting using them on the binary star $\gamma^2$ Velorum where we made a precise measurment of the astrometry of the 2 components (3.65 $\pm$ 0.1 mas).

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