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R. Ignace, K. G. Gayley (University of Iowa)
Resolved X-ray emission lines have now been observed in numerous expanding astrophysical flows, including hot star winds. The profile shapes expected from both thin and thick X-ray lines with continuum re-absorptive opacity are presented for spherically symmetric flows. Asymmetric line profiles result with peak emission occuring at blueshifted frequencies, owing to the higher absorptive column depth to the farther hemisphere. Fully analytic profile shapes can be derived in the limit of a constant expansion wind, which is the relevant case for many hot star winds. When applied to Chandra observations of zeta Pup, the thick-line morphology appears to represent the line width and location of peak emission, in the absence of any additional physical inputs.