HEAD Division Meeting 1999, April 1999
Session 9. Stellar Coronae
Poster, Monday, April 12, 1999, 8:30am-6:10pm, Gold Room

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[9.05] Coronal Element Abundances in the G8 V Star \xi Boo A

J. Martin Laming (NRL), Jeremy J. Drake (SAO)

We present a detailed analysis of a deep EUVE exposure (270 ks) of the G8 V star \xi Boo A. We evaluate electron densities from line ratios in Fe X, Fe XII, Fe XIII, and Fe XIV, and use the intensities of lines from ions Fe IX - XXII to establish the emission measure distribution. We also observe and measure emission in lines from Ne VII, Mg VII - IX, Si VII, VIII, X, XII, S XII - XIV, Ar XV, XVI, Ca XIV - XVII, and Ni XVII, XVIII, from which we derive relative abundances in the corona of \xi Boo A. We find very strong evidence for the FIP (First Ionization Potential) effect, in that the abundances of low FIP elements Mg, Si, Ca, Fe, and Ni appear to be enhanced by a factor of about 4 over those of the high FIP elements S and Ar, relative to their photospheric values. Thus \xi Boo A joins \alpha Cen B (K2 V) and possibly \epsilon Eri (K2 V) in showing similar coronal abundance anomalies to those observed in the Sun, in contrast to Procyon (F5 IV) whose corona appears to have similar composition to its photosphere.

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