EXTREMELY ACTIVE LONG-PERIOD RS CVN BINARY HD-12545

The active-chromosphere giant HD 12545 is noteworthy for its remarkabl e 1990 photometric amplitude of 0.6 mag in V, which implies that nearl y half the visible hemisphere of the star was covered by cool spots. W e report the results of a spectroscopic study of HD 12545, showing it to be an active-chromosphere binary with an orbital period of 23.97 da ys. We establish the spectral type as K0 III, and measure v sin i = 17 +/- 2 km s-1. The various indicators of activity in the optical and u ltraviolet suggest that HD 12545 is one of the most active RS CVn syst ems yet observed. Halpha is a broad, variable emission feature, with a strength comparable to what is observed in very active RS CVn systems such as V711 Tau (HR 1099) or II Peg. The surface fluxes of chromosph eric and transition-region lines in the UV range from 10 to nearly 400 times the solar values. With a moderately strong Li I lambda6707 feat ure and a large space motion, HD 12545 is an unusual but not unique gi ant, since these properties are similar to those of the single active- chromosphere giant HD 33798.