The “Not-so-MAD” Coronal Abundances of Active Stars

Abstract

Coronal abundances have been a subject of debate in the last years due to the availability of high-quality X-ray spectra of many cool stars. 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 dependence, with a functional form dependent on the activity level. We report a detailed analysis of the coronal abundance of 4 stars with various levels of activity and with accurately known photospheric abundances. The coronal abundance is determined using a line flux analysis and a full determination of the differential emission measure. We show that, when coronal abundances are compared with real photospheric values for the individual stars, the resulting pattern can be very different; some active stars with apparent Metal Abundance Deficiency in the corona have coronal abundances that are actually consistent with their photospheric counterparts.