AMBER, Astronomical Multi BEam combineR, is the near-infrared focal instrument dedicated to the VLTI. It is designed to combine three of the VLTI Telescopes and to work simultaneously in the J, H and K spectral bands (1.0 to 2.4 μm).
The project successfully passed the Preliminary Acceptance in Europe in November 2003, resulting in the validation of the instrument laboratory performance1, of the compliance with the initial scientific specifications, and of the acceptance of ESO for AMBER to be part of the VLTI. After the transportation of the instrument to Paranal, Chile in January 2004, the Assembly Integration and Verification phase occurred mid-March to succeed with the first fringes observing bright stars with the VLTI siderostats.
This paper describes the different steps of the AIV and the first results in terms of instrumental stability, estimated visibility and differential phase.
AMBER is a 3 beam combiner for the Very Large Telescope Interferometer (VLTI). It will soon add to VLTI tremendous angular resolution, sensitivity and spectral resolution (λ/Δλ) up to 10,000. This combination opens important new opportunities for the study of the close environment of pre-main-sequence stars.
In order to understand star formation and its evolution, one needs to solve the problem of ejection and collimation mechanisms in jets from young stars. The importance of jets in pre-main-sequence stars relies on the fact that they regulate its angular momentum. By measuring the jet opening angle at the ejection region we can test models for jet origin. In particular, AMBER will provide crucial information on the mechanisms of mass loss and collimation observed in the most active objects. It will allow, for the first time, the differentiation of competing models for jet origin and collimation, namely the X-wind model of Shu and the disk-wind model of Blandford & Payne. In this paper we compare different jet models presented in the literature.
The near-infrared instrument AMBER at the VLTI allows, among other interferometric observables, the simultaneous measurement of the phase between various spectral channels. Color-differential phase thus yields spatial and spectral information on unresolved sources, and could lead to such ambitious goals as the spectroscopy of nearby hot, giant exoplanets. This will require, though, an extreme stability on the measurement, which is likely to be affected by chromatic effects at the various stages of the light path. We present how AMBER has been designed to minimize and to calibrate such effects. We give estimates of their contributions from different origins, and present recent measurements of the instrumental stability. We discuss the possibility to supress the residual chromatic effects in post-data treatment in order to reach a precision limited by the photon noise on the differential phase.
AMBER is the focal near-infrared instrument of the VLTI combining
2 or 3 telescopes in the J, H and K bands with 3 spectral resolution modes. It uses single-mode fibers to ensure modal filtering and high measurement accuracies. AMBER has been integrated and tested in Grenoble during 2003. We report in this paper the lab performances of the instrument in terms of instrumental contrast, measurement accuracy and stability, and throughput.