CHROMOSPHERICALLY ACTIVE STARS .16. THE DOUBLE-LINED BINARY 42-CAPRICORNI

New spectroscopic observations of the chromospherically active binary, 42 Capricorni, have resulted in the detection of lines of the seconda ry, improved orbital elements, and the determination of fundamental pr operties of the components. 42 Cap has an orbital period of 13.174004 d, an eccentricity of 0.176, and a mass ratio A/B of 1.375. No evidenc e for a variation of the center-of-mass velocity, suggested by earlier investigators, has been found. Spectral types of the primary and seco ndary are G1 IV and G2 V, respectively. The V mag difference of 1.94 a nd HIPPARCOS parallax result in M-v = 2.79 mag for A and M-v = 4.73 fo r B. The spectral type of the secondary implies a mass of 1.37 M. for the primary and an orbital inclination of 30 degrees. The primary has begun its evolution through the Hertzsprung Gap and has a radius of 2. 6 R. Comparison with evolutionary tracks results in an age of about 3. 7 Gyr for the system. The subgiant has a log lithium abundance of 2.36 , indicating that it is not a lithium-dip star. (C) 1997 The American Astronomical Society. [S0004-6256(97)04812-7].