CaII H and K and Hα emissions in chromospherically active binary systems (RS Canum Venaticorum and BY Draconis)

Abstract

We report high-resolution observations of the Ca II H and K and Balmer Hα lines in 53 chromospherically active binary systems including the RS Canum Venaticorum binaries (RS CVn) and BY Draconis (BY Dra) classes. The rotational periods of the sample cover a range from 0.8 to 83.2 days. H and K emission-line surface fluxes have been calculated for all the stars in the sample. In spectra where the H∊ line appears in emission, absolute surface fluxes were also determined. The Ca II line profiles corresponding to different seasons and orbital phases are analyzed in order to determine the contribution of each component and to study the chromospheric activity variations. We have measured the Hα equivalent width of the program stars and the Hα core emission was determined by subtraction of the equivalent width of a presumably inactive star of the same spectral type and luminosity class. Three different types of Hα line profiles have been found: strong emission line, weak emission line with strong superposed absorption profile, and filled-in absorption line profile.