THE CHROMOSPHERES OF LATE-TYPE STARS .2. AN ATLAS OF CHROMOSPHERIC LINES FOR SELECTED EARLY-K STARS

For 22 early-K stars, we present high-resolution spectra (lambda/DELTAlambda), = 55 000) of the chromospheric Na I D lines, Ca I lambda4227, Mg I lambdalambda4571, 5167 and 5172, the Ca II H and K resonance and IR lambdalambda8542.144 and 8662.170 lines, Halpha and Hbeta, all observed simultaneously at the AAT, and thus add to a growing data base of spectra of late-type stars. Our data are presented as the observational basis for the self-consistent, semi-empirical modelling of the outer photospheres and chromospheres of the target stars. From trends in our data, we find that stellar activity shows in the low-chromosphere lines as core-filling and, in some stars, as line-broadening. We derive integrated fluxes from the difference spectra, formed by subtracting quiet from active spectra, in the Ca II H and K resonance and IR lambdalambda8542 and 8662 lines and in Halpha, which are presented as chromospheric activity indicators. To these we add the equivalent widths, and the core depths of Halpha and Hbeta, as further indicators. All the activity indices show strong correlations, with the exception of the equivalent widths of Halpha and Hbeta, which we find to be relatively poor activity discriminators. We also find the Balmer decrement to be a useful (and apparently neglected) activity indicator.