New observations of the Ca II H and K and H-epsilon region and/or the Balmer H-alpha line are presented for 100 mostly very active stars but also for weak or inactive stars with suspected activity. Correlations between chromospheric activity at Ca II H and K and H-alpha and effective surface temperature and rotation are identified, and several new stars with chromospheric Ca II H and K emission are discovered. No single activity-rotation relation can be derived for all luminosity classes, and there is clear evidence that evolved stars are generally more active than main-sequence stars of the same rotation period. Binary within the evolved stars appears to play no role, while main-sequence binary stars show generally higher levels of activity than their single counterparts. Chromospheric emission in the Ca II H and K lines depends on surface temperature in that flux declines with cooler temperature.
Strassmeier, K.G.; Fekel, F.C.; Bopp, B.W.; Dempsey, R.C.; Henry, G.W. "Chromospheric CA II H and K and H alpha Emission in Single and Binary Stars of Spectra Types F6--M2" Astrophysical Journal Supplement v.72, p.191 (1990)