A LONG-TERM STUDY OF H-ALPHA-LINE VARIATIONS IN FK COMAE BERENICES

We present observations of Halpha V/R ratio variations in FK Comae Ber enices obtained during several observing seasons from 1981 to 1992. Th e raw Ha emission profile is always observed to be double peaked due t o the stellar-absorption component. During most years the V/R ratio va ries regularly with the period of the photometric light curve. The V/R periodicity is most obvious when time spans no longer than several st ellar rotations are considered. We propose that the bulk of the emissi on component of the Halpha line arises in corotating circumstellar mat erial that may be similar to that of a quiescent solar prominence. The lifetime of these structures appears to be on the order of weeks. A w eak contribution from a circumstellar disk is evident and chromospheri c emission may also be present. The appearance or disappearance of cir cumstellar structures over periods longer than a few weeks, or the tot al absence of such structures, blurs the more regular variations in Ha lpha seen over short time scales. Other more stochastic activity, such as flares, also clearly occurs. Phase shifts of the V/R ratio from ye ar to year rule out the hypothesis that mass transfer in a close binar y system is responsible for the V/R variations.