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Astron. Astrophys. 357, 325-329 (2000)


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ISO spectroscopy of circumstellar dust in the Herbig Ae systems AB Aur and HD 163296 *

M.E. van den Ancker 1,2, J. Bouwman 1, P.R. Wesselius 3, L.B.F.M. Waters 1,4, S.M. Dougherty 5,6 and E.F. van Dishoeck 7

1 University of Amsterdam, Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge, MA 02138, USA
3 SRON Laboratory for Space Research Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands
4 Katholieke Universiteit Leuven, Instituut voor Sterrenkunde, Celestijnenlaan 200B, 3001 Heverlee, Belgium
5 University of Calgary, Deptartment of Physics & Astronomy, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
6 Dominion Radio Astrophysical Observatory, P.O. Box 248, White Lake Road, Penticton, British Columbia V2A 6K3, Canada
7 Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands

Received 17 December 1999 / Accepted 28 February 2000

Abstract

Using both the Short- and Long-wavelength Spectrometers on board the Infrared Space Observatory (ISO), we have obtained infrared spectra of the Herbig Ae systems AB Aur and HD 163296. In addition, we obtained ground-based N band images of HD 163296. Our results can be summarized as follows: (1) The main dust components in AB Aur are amorphous silicates, iron oxide and PAHs; (2) The circumstellar dust in HD 163296 consists of amorphous silicates, iron oxide, water ice and a small fraction of crystalline silicates; (3) The infrared fluxes of HD 163296 are dominated by solid state features; (4) The colour temperature of the underlying continuum is much cooler in HD 163296 than in AB Aur, pointing to the existence of a population of very large (mm sized) dust grains in HD 163296; (5) The composition and degree of crystallization of circumstellar dust are poorly correlated with the age of the central star. The processes of crystallization and grain growth are also not necessarily coupled. This means that either the evolution of circumstellar dust in protoplanetary disks happens very rapidly (within a few Myr), or that this evolution is governed by factors other than stellar mass and age.

Key words: stars: circumstellar matter – stars: emission-line, Be – stars: individual: AB Aur – stars: individual: HD 163296 – stars: pre-main sequence – infrared: stars

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA and on observations collected at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: M.E. van den Ancker (mario@astro.uva.nl)

© European Southern Observatory (ESO) 2000

Online publication: May 3, 2000

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