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- Ion Fractions and the Weak Wind Problem
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Ion Fractions and the Weak Wind Problem
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Abstract
Some late-type O stars are observed to display anomalously weak winds. This issue and the uncertainty about the nature of wind clumping are challenges to line-driven wind theory and need resolving in order to fully understand hot stars. We describe the results from the computation of ion fractions for the various elements in O star winds using the non-LTE code CMFGEN, including parameterisations of microclumping and X-rays. Ion fractions can also be derived from fits to UV wind lines if a mass-loss rate is assumed. We discuss a project to fit unsaturated CIV lines in late O dwarfs, and show that the weak wind scenario could still be a major issue, with some values of M<qCIV> indicated to be more than an order of magnitude lower than theoretical predictions of mass-loss, and measurements from radio and optical diagnostics.
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About: Matthew Austin
Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, United Kingdom
About: Raman Prinja
Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, United Kingdom