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Paper: Crazy Coronal Abundances
Volume: 262, The High Energy Universe at Sharp Focus: Chandra Science
Page: 45
Authors: Linsky, J. L.
Abstract: Chandra high resolution X-ray spectra of active late-type stars and binary systems show a pattern of strange coronal abundances. Elements with low first ionization potential (FIP < 10 eV) like Fe are underabundant, whereas elements with FIP > 10 eV (in particular Ne and Ar) are overabundance compared to solar photospheric values. Preliminary evidence for this pattern was already seen in the ROSAT and ASCA data, but the the Chandra and XMM-Newton data greatly strengthen the case. The coronal abundances in active stars are especially interesting because the solar corona shows the opposite effect (FIP deficiency). I will summarize the new results, compare with the solar abundance results, and comment on the reliability of the stellar abundance anomalies. The solar FIP and stellar anti-FIP effects can be understood (at least in part) in terms of fractionation effects in the chromosphere and perhaps diffusion in the corona. I will compare theoretical predictions with the observed crazy coronal abundances.
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