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Astron. Astrophys. 348, 877-887 (1999)


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ISO spectroscopy of shocked gas in the vicinity of T Tauri *

M.E. van den Ancker 1, P.R. Wesselius 2, A.G.G.M. Tielens 2,3,4, E.F. van Dishoeck 5 and L. Spinoglio 6

1 Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
3 Kapteyn Astronomical Institute, Groningen University, P.O. Box 800, 9700 AV Groningen, The Netherlands
4 NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
5 Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
6 CNR-Istituto di Fisica dello Spazio Interplanetario, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere, I-00133 Roma, Italy

Received 26 May 1999 / Accepted 28 June 1999

Abstract

We present the results of ISO SWS and LWS spectroscopy of the young binary system T Tau. The spectrum shows absorption features due to H2O ice, CO2 ice, gas-phase CO and amorphous silicate dust, which we attribute to the envelope of T Tau S. We derive an extinction of [FORMULA] = [FORMULA] [FORMULA] [FORMULA] towards this source. Detected emission lines from H I arise in the same region which is also responsible for the optical H I lines of T Tau N. These lines most likely arise in a partially ionized wind. Emission from the infrared fine-structure transitions of [S I ], [Ar II ], [Ne II ], [Fe II ], [Si II ], [O I ] and [C II ] was also detected, which we explain as arising in a [FORMULA] 100 km s-1 dissociative shock in a fairly dense ([FORMULA] cm-3) medium. Pure rotational and ro-vibrational emission from molecular hydrogen was detected as well. We show the H2 emission lines to be due to two thermal components, of 440 and 1500 K respectively, which we attribute to emission from the dissociative shock also responsible for the atomic fine-structure lines and a much slower ([FORMULA] 35 km s-1) non-dissociative shock. The 1500 K component shows clear evidence for fluorescent UV excitation. Additionally, we found indications for the presence of a deeply embedded ([FORMULA] [FORMULA] [FORMULA]) source of warm H2 emission. We suggest that this component might be due to a shock, caused by either the outflow from T Tau S or by the infall of matter on the circumstellar disk of T Tau S.

Key words: stars: circumstellar matter – stars: individual: T Tau – stars: pre-main sequence – ISM: jets and outflows – 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.

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

© European Southern Observatory (ESO) 1999

Online publication: August 13, 199

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