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Description
We present high-resolution (R=75000-100000) mid-infrared spectra of the high-mass embedded young star IRS 1 in the NGC 7538 star-forming region. Absorption lines from many rotational states of C_2_H_2_, ^13^C^12^CH_2_, CH_3_, CH_4_, NH_3_, HCN, HNCO, and CS are seen. The gas temperature, column density, covering factor, line width, and Doppler shift for each molecule are derived. All molecules were fit with two velocity components between -54 and -63km/s. We find high column densities (~10^16^cm^-2^) for all the observed molecules compared to values previously reported and present new results for CH_3_ and HNCO. Several physical and chemical models are considered. The favored model involves a nearly edge-on disk around a massive star. Radiation from dust in the inner disk passes through the disk atmosphere, where large molecular column densities can produce the observed absorption line spectrum.
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