The photospheric abundances of active binaries^*,**

II. Atmospheric parameters and abundance patterns for 6 single-lined RS CVn systems

¹ Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Palermo G. S. Vaiana, Piazza del Parlamento 1, 90134 Palermo, Italy
² Astrophysics Division, Research and Science Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
³ Observatoire de Paris, GEPI, place Jules Janssen, 92195 Meudon, France
⁴ Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

Corresponding author: T. Morel, morel@astropa.unipa.it

Received: 12 May 2003
Accepted: 3 September 2003

Abstract

Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca. Two methods have been used. The effective temperatures, surface gravities and microturbulent velocities were first derived from a fully self-consistent analysis of the spectra, whereby the temperature is determined from the excitation equilibrium of the lines. The second approach relies on temperatures derived from the () colour index. These two methods give broadly consistent results for the stars in our sample, suggesting that the neutral iron lines are formed under conditions close to LTE. We discuss the reliability in the context of chromospherically active stars of various colour indices used as temperature indicators, and conclude that the () and () colours are likely to be significantly affected by activity processes. Irrespective of the method used, our results indicate that the X-ray active binaries studied are not as metal poor as previously claimed, but are at most mildly iron-depleted relative to the Sun (). A significant overabundance of several chemical species is observed (e.g., the α-synthezised elements). These abundance patterns are discussed in relation to stellar activity.