Coronal versus photospheric abundances of stars with different activity levels ^*

¹ INAF – Osservatorio Astronomico di Palermo G. S. Vaiana, Piazza del Parlamento, 1, Palermo, 90134, Italy
² Astrophysics Division – Research and Science Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands

Corresponding author: J. Sanz-Forcada, jsanz@astropa.unipa.it

Received: 7 October 2003
Accepted: 6 November 2003

Abstract

We report a detailed analysis of the coronal abundance of 4 stars with varying levels of activity and with accurately known photospheric abundances. The coronal abundance is determined here using a line flux analysis and a full determination of the differential emission measure. Photospheric abundance values are taken from the literature. Previous coronal abundance determinations have generally been compared to solar photospheric abundances; from this a number of general properties have been inferred, such as the presence of a coronal metal depletion with an inverse First Ionization Potential correlated with activity level. Here we show that, when coronal abundances are compared with real photospheric values for the individual stars, the resulting pattern can be very different. Also, we present evidence that, in some cases, the coronal metal abundance may not be uniform in the corona; in particular it can vary with the temperature of the emitting plasma.