CHROMOSPHERICALLY ACTIVE STARS .15. HD 8357=AR PISCIUM, AN EXTREMELY ACTIVE RS CVN SYSTEM

One of the first x-ray sources optically identified as a chromospheric ally active star, HD 8357=AR Piscium, is a double-lined binary consist ing of a K1 IV primary and G7 V secondary. Careful examination of the Ca II H and K lines indicates that only the primary is active, having strong Ca II H and K, H epsilon, and Ha emission. The system has an or bital period of 14.3023 days and an eccentricity of 0.185. Such an ecc entricity is not particularly unusual for chromospherically active sta rs with periods between 10 and 20 days. An assumed mass of 0.92 M. for the secondary results in a 1.12 M. for the subgiant primary and an or bital inclination of 30 degrees. Projected rotational velocities for t he primary and secondary are 6.5+/-2 and 3.5+/-2 km s(-1), respectivel y. Lithium abundances for the two stars are significantly different wi th log epsilon(Li)=2.0 for the primary and less than or equal to 1.35 for the secondary. While the abundance of the subgiant is consistent w ith standard theory, comparison with a survey of other field subgiants suggests that it may be lithium rich. Individual theoretical evolutio nary tracks and cluster ages suggest an age of 7-8 Gyr. HD 8357 is a s tar of the intermediate-disk population having a distance of 39 pc or a parallax of 0.026 ''. (C) 1996 American Astronomical Society.