Coronal abundances from high-resolution X-ray data: The case of Algol

Abstract

We discuss the determination of elemental abundances from high resolution X-ray data. We emphasize the need for an accurate determination of the underlying temperature structure and advocate the use of a line ratio method which allows us to utilize, first, the strongest lines observed in the X-ray spectra, and second, lines that span a rather wide temperature range. We point out the need to use continuous emission measure distributions and show via example that modeling in terms of individual temperature components yields errors of more than 50%. We stress the need to derive differential emission measure distributions based on physical assumptions and considerations. We apply our methods to the Chandra LETGS spectrum of Algol and show that nitrogen is considerably enhanced compared to cosmic abundances by a factor of 2 while carbon is depleted by at least a factor of 25. Iron, silicon, and magnesium, are all depleted compared to cosmic abundances, while the noble gas neon has the relatively highest abundance.

15 pages, 6 figures, A&A accepted

References in corpus (4)

• CHIANTI - an Atomic Database for Emission Lines. Paper VI: Proton Rates and Other Improvements
• Coronal density diagnostics with Helium-like triplets: CHANDRA--LETGS observations of Algol, Capella, Procyon, Eps Eri, Alpha Cen A&B, UX Ari, AD Leo, YY Gem, and HR1099
• Are stellar coronae optically thin in X-rays? - A systematic investigation of opacity effects
• From the Heart of The Ghoul: C and N Abundances in the Corona of Algol B

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