Absil, O. and Le Bouquin, J.-B. and Berger, J.-P. and Lagrange, A.-M. and Chauvin, G. and Lazareff, B. and Zins, G. and Haguenauer, P. and Jocou, L. and Kern, P. and Millan-Gabet, R. and Rochat, S. and Traub, W. (2011) Searching for faint companions with VLTI/PIONIER. I. Method and first results. Astronomy and Astrophysics, 535 . Art. No. A68. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20120215-095804318
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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 χ^2 goodness of fit for a series of binary star models at different positions and with various flux ratios. The resulting χ^2 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 Fomalhaut, tau Cet and Regulus. The median upper limits at 3σ on the companion flux ratio are respectively of 2.3 × 10^(-3) (in 4 h), 3.5 × 10^(-3) (in 3 h) and 5.4 × 10^(-3) (in 1.5 h) on the search region extending from 5 to 100 mas. Our observations confirm that the previously detected near-infrared excess emissions around Fomalhaut and tau Cet are not related to a low-mass companion, and instead come from an extended source such as an exozodiacal disk. In the case of del Aqr, in 30 min of observation, we obtain the first direct detection of a previously known companion, at an angular distance of about 40 mas and with a flux ratio of 2.05 × 10^(-2) ± 0.16 × 10^(-2). Due to the limited u,v plane coverage, its position can, however, not be unambiguously determined. 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.
|Additional Information:||© 2011 ESO. Received 16 July 2011. Accepted 21 September 2011. Published online 09 November 2011. Based on observations obtained at the European Southern Observatory (ESO) Very Large Telescope Interferometer (VLTI), Paranal, Chile. PIONIER is funded by Université Joseph Fourier (UJF, Grenoble-1) with the programme TUNES-SMING, the Institut de Planétologie et d’Astrophysique de Grenoble (IPAG, ex-LAOG), and the Institut National des Science de l’Univers (INSU) with the programmes “Programme National de Physique Stellaire” and “Programme National de Planétologie”. PIONIER was developed by the CRISTAL instrumental team of IPAG in collaboration with R. Millan-Gabet (NExScI) and W. Traub (JPL). The authors want to warmly thank the VLTI team. We acknowledge support from the French National Research Agency (ANR) through project grant ANR10-BLANC0504-01. This work made use of the Smithsonian/NASA Astrophysics Data System (ADS) and of the Centre de Données astronomiques de Strasbourg (CDS).|
|Subject Keywords:||techniques: interferometric; binaries: close; stars: low mass; brown dwarfs; planetary systems|
|Official Citation:||Searching for faint companions with VLTI/PIONIER - I. Method and first results A68 O. Absil et al. Published online: 9 November 2011 DOI: http://dx.doi.org/10.1051/0004-6361/201117719|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||15 Feb 2012 18:50|
|Last Modified:||26 Dec 2012 14:50|
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