Monte-Carlo radiative transfer simulation of the circumstellar disk of the Herbig Ae star HD 144432

Context. Studies of pre-transitional disks, with a gap region between the inner near-infrared-emitting region and the outer disk, are important to improving our understanding of disk evolution and planet formation. Previous infrared interferometric observations have shown hints of a gap region in the protoplanetary disk around the Herbig Ae star HD 144432. Aims. We study the dust distribution around this star with two-dimensional radiative transfer modeling. Methods. We compare the model predictions obtained via the Monte-Carlo radiative transfer code RADMC-3D with infrared interferometric observations and the spectral energy distribution of HD 144432. Results. The best-fit model that we found consists of an inner optically thin component at 0.21–0.32 AU and an optically thick outer disk at 1.4–10 AU. We also found an alternative model in which the inner sub-AU region consists of an optically thin and an optically thick component. Conclusions. Our modeling suggests an optically thin component exists in the inner sub-AU region, although an optically thick component may coexist in the same region. Our modeling also suggests a gap-like discontinuity in the disk of HD 144432.