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Astron. Astrophys. 352, 228-238 (1999)


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Transitional YSOs: candidates from flat-spectrum IRAS sources *

E.A. Magnier 1,2, A.W. Volp 2, K. Laan 2, M.E. van den Ancker 2 and L.B.F.M. Waters 2,3

1 Astronomy Department 351580, University of Washington, Seattle, WA 98195, USA
2 Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
3 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium

Received 17 August 1999 / Accepted 5 October 1999

Abstract

We are searching for Young Stellar Objects (YSOs) near the boundary between protostars and pre-main-sequence objects, what we term Transitional YSOs. We have identified a sample of 125 objects as candidate transitional YSOs on the basis of IRAS colors and the optical appearance on POSS plates. We have obtained optical and near-IR imaging of 82 objects accessible from the Northern Hemisphere and optical images of 62 sources accessible from the South. We also created deconvolved 60 µm IRAS images of all sources. We have classified the objects on the basis of their morphology in the optical and near-IR images. We find that the majority of our objects are associated with star-forming regions, confirming our expectation that the bulk of these objects are YSOs. Of the 125 objects, 28 have a variety of characteristics very similar to other transitional YSOs, while another 22 show some of these characteristics. Furthermore we have found seven objects to be good candidates for members of the Herbig Ae/Be stellar group, of which three are newly identified as such. We have placed a set of images for each of the objects in the archives of the Centre de Données astronomique de Strasbourg (CDS).

Key words: stars: circumstellar matter – stars: evolution – stars: formation – stars: mass-loss – stars: pre-main sequence

* Based on observations collected at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: Eugene A. Magnier

Correspondence to: gene@pikake.astro.washington.edu

© European Southern Observatory (ESO) 1999

Online publication: November 23, 1999

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