Document Type

Article

Publication Date

7-1996

Abstract

One of the first x-ray sources optically identified as a chromospherically active star, HD 8357=AR Piscium, is a double-lined binary consisting 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, Hɛ, and Hα emission. The system has an orbital period of 14.3023 days and an eccentricity of 0.185. Such an eccentricity is not particularly unusual for chromospherically active stars with periods between 10 and 20 days. An assumed mass of 0.92Msun for the secondary results in a 1.12Msun for the subgiant primary and an orbital inclination of 30°. Projected rotational velocities for the primary and secondary are 6.5±2 and 3.5±2 km s-1, respectively. Lithium abundances for the two stars are significantly different with log ɛ(Li)=2.0 for the primary and ≤1.35 for the secondary. While the abundance of the subgiant is consistent with standard theory, comparison with a survey of other field subgiants suggests that it may be lithium rich. individual theoretical evolutionary tracks and cluster ages suggest an age of 7-8 Gyr. HD 8357 is a star of the intermediate-disk population having a distance of 39 pc or a parallax of 0.026".

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