The complex circumstellar environment of HD 142527^⋆

¹ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
e-mail: dr.verhoeff@gmail.com
² Astronomical Institute, University of Utrecht, PO Box 80000, 3508 TA Utrecht, The Netherlands
³ CEA/DSM/DAPNIA/Service d’Astrophysique, CE Saclay, 91191 Gif-sur-Yvette, France
⁴ SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
⁵ Institute for Astronomy, Catholic University Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁶ Leiden Observatory, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
⁷ Department of Information Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan
⁸ Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
⁹ Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁰ Hertzberg Institute for Astrophysics, DRAO, PO Box 248, Penticton, Canada

Received: 7 May 2010
Accepted: 14 January 2011

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 HD 142527, 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 HD 142527 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 HD 142527.

Methods. We map the composition and spatial distribution of the dust around HD 142527. 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 HD 142527 has three geometrically distinct components separated by a disk gap running from 30 to 130 AU. There is a geometrically flat inner disk running from 0.3 AU up to 30 AU; an optically thin halo-like component of dust in the inner disk regions; and a massive self-shadowed outer disk running from 130 AU up to 200 AU. 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 = 60 AU. Owing to the gray extinction of the “halo” we obtained new stellar parameters, including a stellar luminosity of 20  ±  2 L_⊙ and age of 10^{6.7 ± 0.4} yr.

Conclusions. We find that the disk surrounding HD 142527 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.