Structure of Herbig AeBe disks at the milliarcsecond scale

A statistical survey in the H band using PIONIER-VLTI^⋆

¹ Univ. Grenoble Alpes, IPAG; CNRS, IPAG, 38000 Grenoble, France
e-mail: Bernard.Lazareff@univ-grenoble-alpes.fr
² ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
³ University of Exeter, Department of Physics and Astronomy, Stocker Road, Exeter, Devon EX4 4QL, UK
⁴ Department of Statistics, University of the Western Cape, Private Bag X17, 7535 Bellville, South Africa
⁵ STAR, Université de Liège, 19c allée du Six Août, 4000 Liège, Belgium
⁶ UMI-FCA, CNRS/INSU, France
⁷ Max-Planck-Institut für Extraterrestrische Physik, 85748 Garching, Germany
⁸ Center for High Angular Resolution Astronomy, Georgia State University, PO Box 3969, Atlanta, GA 30302, USA
⁹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
¹⁰ Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA
¹¹ Centro de Astroingeniería, Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
¹² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹³ Department of Astronomy, University of Michigan, 1085 S. University Ave, 311 West Hall, Ann Arbor, MI 48109, USA
¹⁴ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
¹⁵ NASA Exoplanet Science Institute, California Institute of Technology, 770 S. Wilson Ave., Pasadena, CA 91125, USA
¹⁶ CRAL, Observatoire de Lyon, CNRS, Univ. Lyon 1, École Normale Supérieure de Lyon, 69364 Lyon, France
¹⁷ Biomedical Imaging Group, École polytechnique fédérale de Lausanne, Switzerland
¹⁸ Jet Propulsion Laboratory, M/S 321-100, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
¹⁹ ESO Vitacura, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
²⁰ Departamento de Astronomía, Universidad de Chile, Casilla 36- D Santiago, Chile

Received: 13 July 2016
Accepted: 4 November 2016

Abstract

Context. It is now generally accepted that the near-infrared excess of Herbig AeBe stars originates in the dust of a circumstellar disk.

Aims. The aims of this article are to infer the radial and vertical structure of these disks at scales of order 1 au, and the properties of the dust grains.

Methods. The program objects (51 in total) were observed with the H-band (1.6 μm) PIONIER/VLTI interferometer. The largest baselines allowed us to resolve (at least partially) structures of a few tenths of an au at typical distances of a few hundred parsecs. Dedicated UBVRIJHK photometric measurements were also obtained. Spectral and 2D geometrical parameters are extracted via fits of a few simple models: ellipsoids and broadened rings with azimuthal modulation. Model bias is mitigated by parallel fits of physical disk models. Sample statistics were evaluated against similar statistics for the physical disk models to infer properties of the sample objects as a group.

Results. We find that dust at the inner rim of the disk has a sublimation temperature T_sub ≈ 1800 K. A ring morphology is confirmed for approximately half the resolved objects; these rings are wide δr/r ≥ 0.5. A wide ring favors a rim that, on the star-facing side, looks more like a knife edge than a doughnut. The data are also compatible with the combination of a narrow ring and an inner disk of unspecified nature inside the dust sublimation radius. The disk inner part has a thickness z/r ≈ 0.2, flaring to z/r ≈ 0.5 in the outer part. We confirm the known luminosity-radius relation; a simple physical model is consistent with both the mean luminosity-radius relation and the ring relative width; however, a significant spread around the mean relation is present. In some of the objects we find a halo component, fully resolved at the shortest interferometer spacing, that is related to the HAeBe class.