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Astron. Astrophys. 331, 211-223 (1998)


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An ultraviolet, optical and infrared study of Herbig Ae/Be stars *

K. Malfait ** , 1, E. Bogaert 2 and C. Waelkens 1

1 Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
2 Koetsweg 243, B-3010 Kessel-Lo, Belgium

Received 4 March 1997 / Accepted 8 August 1997

Abstract

We have selected a list of 45 Herbig Ae/Be-type candidates on the base of their IRAS colors and their spectral types. We propose the presence of a broad infrared excess as a defining criterion for these stars, rather than the detection of circumstellar nebulosity. In this way, our selection also includes more evolved young stars, that are no longer embedded in their star-forming region. A few objects in our sample are well-known Herbig Ae/Be stars, others are new. New optical and near-infrared photometric observations, as well as ultraviolet ones, are presented. The position of the objects in several color-color diagrams, as well as their de-reddened energy distributions, permit a reliable classification. Three objects probably are binaries with a cool secondary, 9 appear to be related to the Vega-type stars and 33 objects can be classified as genuine Herbig Ae/Be stars. The majority of the Herbig Ae/Be stars have a dusty environment consisting of a distinct hot and cool component. These isolated Herbig Ae/Be stars suggest an evolution from embedded Herbig Ae/Be stars to [FORMULA] Pictoris-like main-sequence stars, an evolution in which planet formation may play an important role.

Key words: stars: evolution – pre-main sequence – formation – circumstellar matter – planetary systems – infrared: stars

* Based on observations obtained at the European Southern Observatory, La Silla, Chile; and at the Swiss Telescope, La Silla, Chile; and at the Swiss Telescope, Hochalpine Forschungsstation Jungfraujoch, Switzerland, and with the International Ultraviolet Explorer (IUE)
** Research Assistant of the Fund for Scientific Research - Flanders

Send offprint requests to: K. Malfait, Leuven, Koen.Malfait@ster.kuleuven.ac.be

© European Southern Observatory (ESO) 1998

Online publication: February 4, 1998
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