The complex circumstellar environment of HD 142527

Abstract

Context. The recent findings of gas giant planets around young A-type stars suggest that disks surrounding Herbig Ae/Be stars will develop planetary systems. An interesting case is HD142527, for which previous observations revealed a complex circumstellar environment and an unusually high ratio of infrared to stellar luminosity. Its properties differ considerably from other Herbig Ae/Be stars. This suggests that the disk surrounding HD142527 is in an uncommon evolutionary stage. Aims. We aim for a better understanding of the geometry and evolutionary status of the circumstellar material around the Herbig Ae/Be star HD142527. Methods. We map the composition and spatial distribution of the dust around HD142527. We analyze SEST and ATCA millimeter data, VISIR N and Q-band imaging and spectroscopy. We gather additional relevant data from the literature. We use the radiative transfer code MCMax to construct a model of the geometry and density structure of the circumstellar matter, which fits all of the observables satisfactorily. Results. We find that the disk of HD142527 has three geometrically distinct components separated by a disk gap running from 30 to 130AU. There is a geometrically flat inner disk running from 0.3AU up to 30AU; an optically thin halo-like component of dust in the inner disk regions; and a massive self-shadowed outer disk running from 130AU up to 200AU. We derived a total dust mass in small grains of 1.0 × 10−3 M and a vertical height of the inner wall of the outer disk of h = 60AU. Owing to the gray extinction of the “halo” we obtained new stellar parameters, including a stellar luminosity of 20 ± 2 L and age of 106.7 ± 0.4 yr. Conclusions. We find that the disk surrounding HD142527 is highly evolved despite the relatively young age of the star. The peculiar disk geometry can explain the extreme IR reprocessing efficiency of the disk. Furthermore, the geometry, the large disk mass, and the highly processed dust composition are indicative of on-going planet formation.