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Astron. Astrophys. 321, 523-530 (1997)


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Origin of the mid-infrared emission and supersonic jet toward LkH 234 *

Sylvie Cabrit 1, Pierre-Olivier Lagage 2, Mark McCaughrean 3 and Göran Olofsson 4

1 Observatoire de Paris, DEMIRM, URA 336 du CNRS, 61 Avenue de l'Observatoire, F-75014 Paris, France
2 CEA/DSM/DAPNIA, Service d'Astrophysique (URA 2052 du CNRS), C.E. Saclay, F-91191 Gif-sur-Yvette, France
3 Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
4 Stockholm Observatorium, S-13336 Saltsjöbaden, Sweden

Received 14 June 1996 / Accepted 18 September 1996

Abstract

We present high-resolution imaging of the region around the Herbig Ae/Be star LkH [FORMULA] 234 in the 10µm and 17µm atmospheric windows and in the H2 v=1-0 S(1) line and adjacent continuum. LkH [FORMULA] 234 is unresolved at mid-infrared wavelengths (FWHM [FORMULA] 1 [FORMULA]) and has a decreasing spectrum compatible with an accretion disk. A cold mid-infrared companion is revealed [FORMULA] to the north-west of the optical star, corresponding well to the polarization centre identified in the K-band by Weintraub et al. (1994). The companion illuminates an arc-shaped reflection nebula with very red colours, and is associated with a radio continuum source, H2 O masers, and a bright extended H2 emission knot, indicating that it is deeply embedded and has strong outflow activity. However, its role in driving the optical jet near LkH [FORMULA] 234 is not clear. Our high-resolution H2 image reveals that the jet has a complex structure, with an inner part at PA [FORMULA] emitting brightly in H2, and an outer part at PA [FORMULA] seen only in [SII ]. The inner H2 jet does not point back exactly toward the infrared companion, indicating either that it is deflected after leaving that object, or that it is driven by a yet unidentified source. Available long-slit spectra favor the idea that the outer jet emitting in [SII ] could be powered by the 10µm companion rather than by LkH [FORMULA] 234. High-resolution [SII ] imaging is required to test this hypothesis.

Key words: stars: circumstellar matter – stars: Be – stars: individual: LkHff 234 – stars: pre-main sequence – ISM: jets and outflows – infrared: stars

* Based on data obtained at the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique, and University of Hawaii; at the German-Spanish national observatory at Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg; and at the Nordic Optical Telescope

Send offprint requests to: Sylvie.Cabrit@obspm.fr

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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