A STUDY OF THE CHROMOSPHERICALLY ACTIVE, SHORT-PERIOD BINARY VZ PISCIUM

The short-period binary VZ Piscium is unusual in that it has a high sp ace velocity, indicating that it is old, and a high mass ratio, sugges ting that it is presently evolving into contact with little mass excha nge having occurred between the components. In this study, we obtained IUE and visible spectra to investigate Mg II h+k and Ca II H and K em ission strengths. Both features are found to be strong and variable. F rom the visible spectra, radial velocities were measured, and a new ma ss ratio of q = 0.80 was determined. This mass ratio was used in a new light-curve analysis, and the system was found to be in marginal cont act, with the secondary component slightly detached. A model with brig ht (hot) regions on the inner hemisphere of the slightly detached, les s massive component was found to fit well with the variety of spectros copic and photometric observations of the system. The masses determine d for the components are compatible with normal K dwarfs.