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Astron. Astrophys. 315, L197-L200 (1996)

SWS H2 observations in the BD+40o4124 group*

P.R. Wesselius1, M.E. van den Ancker2, E.T. Young3, F.O. Clark4, T. Prusti5, P.R. Roelfsema1, C. Waelkens6, D.H. Wooden7, D.R. Boxhoorn1,5, A.M. Heras5, E. Huygen6, D.J.M. Kester1, and F. Lahuis1,5

1 SRON, P.O Box 800, NL-9700 AV Groningen, The Netherlands
2 Astron. Inst. ``Anton Pannekoek'', Univ. of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
3 University of Arizona, Steward Observatory, Tucson, AZ 85721, USA
4 Phillips Laboratory, OL-AA, PL/GOB, Hanscom AFB, MA 01731, USA
5 ESA Villafranca, P.O. Box 50727, E-28080 Madrid, Spain
6 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
7 NASA Ames Research Center, MS N-245-6, Moffet Field, CA 94035-1000, USA

Received 16 July 1996 / Accepted 13 August 1996

Abstract. We report the detection of pure rotational lines of H2O observed in the direction of three young stellar objects in the BD+40o4124 group, with the short-wavelength spectrometer (SWS) on board ISO. The rotational population distributions of all three stars are consistent with a thermal distribution. The derived kinetic temperatures are img3.gif 500 K for BD+404124 and LkHimg4.gif 224 and img3.gif 800 K for LkHimg4.gif 225. The amounts of molecular hydrogen detected are 0.01 to 0.04 Mimg5.gif. The relative abundances of ortho- and para-hydrogen are consistent with a high temperature equilibrium distribution. We conclude that the molecular hydrogen emission in all three regions appears to lie behind approximately 10-25m of visual extinction and is probably not directly associated with any of the optical sources.

Key words: sircumstellar matter - stars: formation - 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

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