Max Planck Institut für Radioastronomie,
Auf dem Hügel 69,
2 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR, 5274, France
3 Université de Liège, 17 Allée du Six Août, 4000 Liège, Belgium
4 European Southern Observatory, Alonso de Cordova, 3107 Vitacura, Chile
5 Université de Bordeaux, Observatoire Aquitain des Sciences de l’Univers, UMR 5804, Floirac, France
6 NASA Exoplanet Science Institute (Caltech), MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125, USA
7 Jet Propulsion Laboratory (NASA/JPL), MS 301-355, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Received: 25 August 2012
Accepted: 1 October 2012
Aims. We aim at resolving the circumstellar environment around β Pic in the near-infrared in order to study the inner planetary system (<200 mas, i.e., ~4 AU).
Methods. Precise interferometric fringe visibility measurements were obtained over seven spectral channels dispersed across the H band with the four-telescope VLTI/PIONIER interferometer. Thorough analysis of interferometric data was performed to measure the stellar angular diameter and to search for circumstellar material.
Results. We detected near-infrared circumstellar emission around β Pic that accounts for 1.37% ± 0.16% of the near-infrared stellar flux and that is located within the field-of-view of PIONIER (i.e., ~200 mas in radius). The flux ratio between this excess and the photosphere emission is shown to be stable over a period of 1 year and to vary only weakly across the H band, suggesting that the source is either very hot (≳1500 K) or dominated by the scattering of the stellar flux. In addition, we derive the limb-darkened angular diameter of β Pic with an unprecedented accuracy (θLD= 0.736 ± 0.019 mas).
Conclusions. The presence of a small H-band excess originating in the vicinity of β Pic is revealed for the first time thanks to the high-precision visibilities enabled by VLTI/PIONIER. This excess emission is likely due to the scattering of stellar light by circumstellar dust and/or the thermal emission from a yet unknown population of hot dust, although hot gas emitting in the continuum cannot be firmly excluded.
Key words: instrumentation: high angular resolution / techniques: interferometric / infrared: planetary systems
© ESO, 2012