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D.A. Weintraub (Vanderbilt University), J.S. Bary (University of Virginia), J.H. Kastner (Rochester Institute of Technology), S.J. Shukla, K. Chynoweth (Vanderbilt University)
We present results from our search for v = 1 --> 0 S(1) ro-vibrational line emission at 2.1218 \mum from quiescent molecular hydrogen -- that is, H2 centered at stellar rest velocities and not in outflows -- toward classical and weak-lined T Tauri stars and Herbig Ae/Be stars in nearby, star-forming regions. We report positive detections for four weak-lined T Tauri stars (DoAr 21, Sz 33, Sz 41, V773 Tau), eight classical T Tauri stars (TW Hya, GG Tau A, LkCa 15, AA Tau, CW Tau, UY Aur, GM Aur, CS Cha), and one Herbig Ae/Be star (HD 97048) and non-detections for about 30 sources. The H2 emission observed towards these sources is located in disks orbiting the young stars, most likely at distances of 5-30 AU from the stars in regions of moderate density above and below the disk mid-planes. Our results show that a significant fraction of the stars surveyed show detectable levels of S(1) line emission and thus that the presence of near-infrared emission from quiescent H2 in circumstellar disks of pre-main sequence stars is not rare. Strong UV and/or X-ray emission is required to stimulate the observed H2 line emission; thus, the detection of emission from quiescent H2 gas at 2.1218 \mum may also be an indirect signature of accretion-generated UV excess or X-ray emission, although strong UV (or X-ray) emission from highly active chromospheres (or coronae) may also excite the H2.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.