THE BEHAVIOR OF THE EXCESS CA-II-H AND K AND H-EPSILON EMISSIONS IN CHROMOSPHERICALLY ACTIVE BINARIES

In this work we analyze the behaviour of the excess Ca II H and K and H epsilon emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of different activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fern andez-Figueroa et al. (1994) and the observations of 28 systems descri bed by Montes et al. (1995c). By using the spectral subtraction techni que (subtraction of a synthesized stellar spectrum constructed from re ference stars of spectral type and luminosity class similar to those o f the binary star components) we obtain the active-chromosphere contri bution to the Ca II H and K lines in these 73 systems. We have determi ned the excess Ca II H and K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component we re obtained when it was possible to deblend both contributions. We hav e found that the components of active binaries are generally stronger emitters than single active stars for a given effective temperature an d rotation rate. A slight decline of the excess Ca II H and K emission s towards longer rotation periods, P-rot, and larger Rossby numbers, R (0), is found. When we use R(0) instead of P-rot, the scatter is reduc ed and a saturation at R(0) approximate to 0.3 is observed. A good cor relation between the excess Ca II K and H epsilon chromospheric emissi on fluxes has been found. The correlations obtained between the excess Ca II K emission and other activity indicators, (C IV in the transiti on region, and X-rays in the corona) indicate that the exponents of th e power-law relations increase with the formation temperature of the s pectral features.