CHROMOSPHERIC CA-II-H AND CA-II-K AND H-ALPHA EMISSION IN SINGLE AND BINARY STARS OF SPECTRAL TYPES-F6-M2

We have obtained high- and medium-resolution Ca II H and K and/or Hα line profiles for 100 single and binary stars of spectral type F6 to M2 and luminosity class III, IV, and V. The sample includes inactive single and binary stars as well as moderately to extremely active single stars including the FK Com stars and active binary stars of the RS CVn and BY Dra class with a total range of rotation periods from 0.5 to 310 days. A total of 444 spectra have been acquired and are used to measure absolute Ca II H and K emission-line surface fluxes and Balmer Ha core emission equivalent widths. Some of the stars also have been observed at 6430 Å to determine their rotational velocities. These data, supplemented by published observations, have been used to identify correlations between chromospheric activity at Ca II H and K and Ha and effective surface temperature and rotation. Several new stars with chromospheric Ca II H and K emission have been discovered. We have also used ultraviolet C IV emission-line fluxes taken from the literature and compared them with the present data. 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. Binarity per se within the evolved stars plays apparently no role, while the 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 also upon surface temperature in the sense that the flux declines with cooler temperature. The trend in the Hα equivalent width-log ℱ′(Ca II K) plane is that with increasing K line flux the Hα absorption core first deepens until log ℱ′(K) ∼ 5.8 ergs cm-2 s-1 is reached and then fills in quite rapidly.