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J. H. Lacy, M. J. Richter, T. K. Greathouse, D. T. Jaffe (Astronomy, University of Texas, Austin)
TEXES is a versatile and sensitive astronomical spectrograph for the 5-25\mum wavelength region. It is the ground-based predecessor of EXES, a PI-class instrument for SOFIA. TEXES can be used in four modes: high-resolution cross-dispersed, with R=100,000, 0.5% spectral coverage, and an 8'' slit length (varying with wavelength); medium-resolution long-slit, with R=15,000, 0.5% coverage, and an 60'' slit; low-resolution long-slit, with R=4,000, 0.2\mum coverage, and an 60'' slit; and source acquisition imaging with 0.4'' pixels and 25 \times 25'' field of view. The high resolution disperser is an echelon, a very coarsely and steeply ruled 36''-long grating. The cross disperser and medium resolution grating is an R2 echelle. The low resolution disperser is an R0.5 first-order grating, which is turned face-on for low efficiency imaging. The detector is a low-background Raytheon 256\times256 pixel Si:As IBC. TEXES has been used successfully at the McDonald Observatory 2.7m telescope and is scheduled on the IRTF in fall 2000. It has achieved its design resolution and background photon noise limited. It is available to outside collaborators on the IRTF. Results from observations at McDonald and the IRTF, including H2O and Mg I in K and M giants, SiO and hydrocarbons in circumstellar outflows, interstellar molecules, and hydrocarbons in planetary atmosphere, will be presented. This work was supported by the NSF, USRA, and Texas Advanced Research Program.