X-Ray Line Emission from the Hot Stellar Wind of θ[TSUP]1[/TSUP] Orionis C

Abstract

We present a first emission-line analysis of a high-resolution X-ray spectrum of the stellar wind of v 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 K. The He triplets are very sensitive to density as well. At these temperatures the relative strengths 7 6.1 # 10 of the intercombination and forbidden lines indicate electron densities well above 10 12 cm 23 . The lines appear significantly broadened, from which we deduce a mean velocity of 770 km s 21 with a spread between 400 and 2000 km s 21 . 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 cm. 10 4 # 10 Subject headings: binaries: general — stars: early-type — stars: winds, outflows — techniques: spectroscopic — X-rays: stars