ar X iv : a st ro - p h / 01 02 03 0 v 1 2 F eb 2 00 1 Computer simulations of interferometric imaging with the VLT interferometer and its AMBER instrument

We present computer simulations of interferometric imaging with the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) and the Astronomical MultiBEam Recombiner (AMBER) phase-closure instrument. These simulations include both the astrophysical modelling of a stellar object by radiative transfer calculations and the simulation of light propagation from the object to the detector (through atmosphere, telescopes, and the AMBER instrument), simulation of photon noise and detector read-out noise, and finally data processing of the interferograms. The results show the dependence of the visibility error bars on the following observational parameters: different seeing during the observation of object and reference star (Fried parameters r 0,object and r 0,ref. ranging between 0.9 m and 1.2 m), different residual tip-tilt error (δ tt,object and δ tt,ref. ranging between 0.1% and 20% of the Airy disk diameter), and object brightness (K object =0.7 mag to 10.2 mag, K ref. =0.7 mag). Exemplarily, we focus on stars in late stages of stellar evolution and study one of its key objects, the dusty supergiant IRC +10 420 that is rapidly evolving on human timescales. We show computer simulations of VLT interferometry (visibility and phase closure measurements) of IRC +10 420 with two and three Auxiliary Telescopes (ATs; AMBER wide-field mode, i.e. without fiber optics spatial filters) and discuss whether the visibility accuracy is sufficient to distinguish between different theoretical model predictions.