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decAbstract:
{We present a first emission-line analysis of a high-resolution X-ray spectrum of the stellar wind of þetas}$^{1}$ Ori C obtained with the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory. The spectra are resolved into a large number of emission lines from H- and He-like O, Ne, Mg, Si, S, Ar, and Fe ions. The He-like Fe XXV and Li-like Fe XXIV appear quite strong, indicating very hot emitting regions. From H/He flux ratios as well as from Fe He/Li emission measure ratios, we deduce temperatures ranging from 0.5 to 6.1{\times}10⁷ K. The He triplets are very sensitive to density as well. At these temperatures the relative strengths of the intercombination and forbidden lines indicate electron densities well above 10$^{12}$ cm$^{-3}$. The lines appear significantly broadened, from which we deduce a mean velocity of 770 km s$^{-1}$ with a spread between 400 and 2000 km s$^{-1}$. Along with results of the deduced emission measure, we conclude that the X-ray emission could originate in dense and hot regions with a characteristic size of less then 4{\times}10$^{10}$ cm. }