Searching for faint companions with VLTI/PIONIER. I. Method and first results
Résumé
Context. A new four-telescope interferometric instrument called PIONIER has recently been installed at VLTI. It provides improved imaging capabilities together with high precision.
Aims: We search for low-mass companions around a few bright stars using different strategies, and determine the dynamic range currently reachable with PIONIER.
Methods: Our method is based on the closure phase, which is the most robust interferometric quantity when searching for faint companions. We computed the χ2 goodness of fit for a series of binary star models at different positions and with various flux ratios. The resulting χ2 cube was used to identify the best-fit binary model and evaluate its significance, or to determine upper limits on the companion flux in case of non-detections.
Results: No companion is found around
Conclusions: After only a few months of operation, PIONIER has already achieved one of the best dynamic ranges world-wide for multi-aperture interferometers. A dynamic range up to about 1:500 is demonstrated on unresolved targets, but significant improvements are still required to reach the ultimate goal of directly detecting hot giant extrasolar planets.
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