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M.A. Bitner (University of Texas at Austin), M.J. Richter (University of California, Davis), J.H. Lacy, D.T. Jaffe (University of Texas at Austin), T.K. Greathouse (Lunar and Planetary Institute), J.E. Kessler-Silacci (University of Texas at Austin), G.A. Blake (California Institute of Technology)
We have observed the Herbig Ae star, AB Aur, with TEXES, the Texas Echelon-cross-Echelle Spectrograph (Lacy et al. 2002), on the NASA IRTF to search for molecular hydrogen emission in the mid-infrared. From the ground, three pure rotational transitions of molecular hydrogen are accessible: J=6-4 (\lambda = 8.025 \mum), J=4-2 (\lambda = 12.279 \mum), and J=3-1 (\lambda = 17.035 \mum). To this point, studies of gas in protoplanetary disks have focused on either small radii using near-infrared CO emission as a probe or on large radii with observations in the millimeter wavelength range. Observations of molecular emission in the mid-infrared offer the potential to study gas in disks at intermediate radii (1-10AU). Molecular hydrogen can be a useful probe since it is the dominant constituent in disks and therefore allows for mass determinations which avoid CO/H2 conversion factors. When coupled with knowledge of the stellar mass and inclination, high resolution observations (R\approx60,000 for J=3-1 and R\approx80,000 for J=4-2 and J=6-4) may allow us to study line profiles and determine the radial location of the emission. In the case of AB Aur, we have detected J=4-2 emission with FWHM 7 km s-1. Assuming an inclination of 20\circ and a stellar mass of 2.5 M\sun centers the emission near 16 AU in the disk.
Observations with TEXES are supported by NSF grant AST-0205518.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.