Hot circumstellar material resolved around β Pic with VLTI/PIONIER^⋆

¹ Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: ddefrere@mpifr-bonn.mpg.de
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

Abstract

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 (θ_LD= 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.