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Astron. Astrophys. 344, L9-L12 (1999)

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Letter to the Editor

Shocked molecular hydrogen from RNO 91

M.S. NandaKumar 1, B.G. Anandarao 1 and C.J. Davis 2

1 Physical Research Laboratory, Navrangpura, Ahmedabad, 380009 - India (nanda@prl.ernet.in,anand@prl.ernet.in)
2 Joint Astronomy Center, 660 N. A'ohoku Place, University Park, Hilo, HI 96720, USA (cdavis@jach.hawaii.edu)

Received 18 November 1998 / Accepted 18 February 1999

Abstract

We report the detection of the H2 [FORMULA]=1-0 S(1) line at 2.122 µm, from RNO 91 in the L43 dark cloud, which is known to be a T Tauri star surrounded by a 1700AU disk structure (containing ices) and a weak outflow. The non-detection of the H2 [FORMULA]=2-1 S(1) line at 2.247 µm suggests shock excitation rather than fluorescence. The emission is extended spatially up to 9" in the north-south direction. The line intensity peak (FWHM [FORMULA] 3") corresponds to the star RNO 91 which is embedded in a cocoon of gas and dust. The observed H2 emission from this cocoon may be attributed to embedded Herbig-Haro like knots. The H2 line flux in the central [FORMULA] is estimated to be [FORMULA] ergs sec-1 cm- 2, which indicates a mass flow rate of [FORMULA] [FORMULA] yr-1. Furthermore, narrow band image taken through H2 1-0 S(1) filter is presented, which reveal a tilted disk and bipolar outflow structure that agrees with earlier observations and models. We show that this disk/outflow system is a unique case.

Key words: stars: formation – stars: pre-main sequence – ISM: Herbig-Haro objects – ISM: jets and outflows – infrared: stars – accretion, accretion disks

Send offprint requests to: M.S. Nanda Kumar

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© European Southern Observatory (ESO) 1999

Online publication: March 10, 1999
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