2012A&A...541A.104C

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. 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. We derive a K-band ring-fit radius of 0.17±0.01AU and an H-band radius of 0.18±0.01AU (for a distance of 145pc). This measured K-band radius of ∼0.17AU lies in the range between the dust sublimation radius of ∼0.13AU (predicted for a dust sublimation temperature of 1500K and gray dust) and the prediction of models including backwarming (∼0.27AU). 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 ∼0.21AU, a temperature of ∼1600K, and a ring thickness ∼0.02AU. The outer part extends from ∼1AU to ∼10AU with an inner temperature of ∼400K. We find that the disk is nearly face-on with an inclination angle of <28°. 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 2µm. 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.