The transition layer of eleven late-type stars.

Abstract

Far UV-spectra of eleven F, G, and K stars of different luminosity class have been studied. Si IV, C IV, and N V emission line fluxes have been used to obtain parameters for the transition region. The stars of the sample have been classified according to the activity level. Using two abundance criteria the gaseous pressure upper limits have been computed and they show a correlation with the line surface fluxes. From a beta(1)-beta(2) diagram the mass column density ratio has been derived. For all the stars selected the optical depth in the line center presents the following trend: tau(Si IV) greater than tau(C IV) greater than tau(N V).