Near-infrared interferometric observation of the Herbig Ae star HD 144432 with VLTI/AMBER^⋆

L. Chen¹, A. Kreplin^1⋆⋆, Y. Wang¹, G. Weigelt¹, K.-H. Hofmann¹, S. Kraus², D. Schertl¹, S. Lagarde³, A. Natta⁴, R. Petrov³, S. Robbe-Dubois³ and E. Tatulli^5,6

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: lchen@mpifr-bonn.mpg.de
² Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109-1090, USA
³ Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
⁴ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
⁶ Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, 411007 Pune, India

Received: 13 January 2012
Accepted: 15 March 2012

Abstract

Aims. We study the sub-AU-scale circumstellar environment of the Herbig Ae star HD 144432 with near-infrared VLTI/AMBER observations to investigate the structure of its inner dust disk.

Methods. The interferometric observations were carried out with the AMBER instrument in the H and K band. We interpret the measured H- and K-band visibilities, the near- and mid-infrared visibilities from the literature, and the spectral energy distribution (SED) of HD 144432 by using geometric ring models and ring-shaped temperature-gradient disk models with power-law temperature distributions.

Results. We derive a K-band ring-fit radius of 0.17 ± 0.01   AU and an H-band radius of 0.18 ± 0.01   AU (for a distance of 145   pc). This measured K-band radius of  ~0.17   AU lies in the range between the dust sublimation radius of  ~0.13   AU (predicted for a dust sublimation temperature of 1500   K and gray dust) and the prediction of models including backwarming (~0.27 AU). We find that an additional extended halo component is required in both the geometric and temperature-gradient modeling. In the best-fit temperature-gradient model, the disk consists of two components. The inner part of the disk is a thin ring with an inner radius of  ~0.21   AU, a temperature of  ~1600   K, and a ring thickness  ~0.02   AU. The outer part extends from  ~1   AU to  ~10   AU with an inner temperature of  ~400   K. We find that the disk is nearly face-on with an inclination angle of  <.

Conclusions. Our temperature-gradient modeling suggests that the near-infrared excess is dominated by emission from a narrow, bright rim located at the dust sublimation radius, while an extended halo component contributes  ~6% to the total flux at 2   μm. The mid-infrared model emission has a two-component structure with  ~20% of the flux originating from the inner ring and the rest from the outer parts. This two-component structure is indicative of a disk gap, which is possibly caused by the shadow of a puffed-up inner rim.