* Astronomy

Title: Near-infrared interferometric observation of the Herbig Ae star HD144432 with VLTI/AMBER
Authors: Lei Chen, Alexander Kreplin, Yang Wang, Gerd Weigelt, Karl-Heinz Hofmann, Stefan Kraus, Dieter Schertl, Stephane Lagarde, Antonella Natta, Roman Petrov, Sylvie Robbe-Dubois, Eric Tatulli

We study the sub-AU-scale circumstellar environment of the Herbig Ae star HD144432 with near-infrared (NIR) VLTI/AMBER observations to investigate the structure of its inner dust disk. 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 SED of HD144432 by using geometric ring models and ring-shaped temperature-gradient disk models with power-law temperature distributions. We derived 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 grey dust) and the prediction of models including backwarming (~0.27 AU). We found that an additional extended halo component is required in both the geometric and temperature-gradient modelling. In the best 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 < 28 degree. Our temperature-gradient modelling suggests that the NIR 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 MIR model emission has a two-component structure with ~20% flux from the inner ring and the rest from the outer part. This two-component structure suggests a disk gap, which is possibly caused by the shadow of a puffed-up inner rim.

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