A&A 388, L13-L16 (2002)
Carbon and nitrogen abundances in the coronae of Algol B and other evolved stars: Evidence for CNO-cycle processed materialJ. H. M. M. Schmitt and J.-U. Ness
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
(Received 21 March 2002 / Accepted 10 April 2002 )
Using the Ly -lines of carbon and nitrogen measured in Chandra Low Energy Transmission Grating Spectrometer (LETGS) spectra we study the coronal abundances of these elements in a sample of late-type stars including dwarf stars, the prototypical eclipsing binary Algol, the single giant Cet, and three RS CVn binaries. In the main sequence stars of our sample the flux ratio between the Ly -lines of nitrogen and carbon is below unity, while is found to be 8.5 for Cet and >23.3 for Algol. These values are more than an order of magnitude larger than expected from a solar abundance plasma in collisional equilibrium regardless of the chosen temperature structure. We therefore interpret the anomalously large -ratios as being due to the exposure of processed material at the surfaces and in the coronae of Algol and Cet.
Key words: stars: abundances -- stars: activity -- stars: coronae -- stars: late type X-rays: stars -- stars: individual: Algol
Offprint request: J. H. M. M. Schmitt, firstname.lastname@example.org
© ESO 2002