The radio light curve of FK Comae at 3.6 cm

The VLA radio telescope was used to obtain 29 X-band (3.6 cm) observations of the very active, rapidly rotating giant FK Comae over three weeks in October 1989. A brightening from the usual 1-2 mJy to about 12 mJy which lasted about 5 days was observed at the beginning of the run. The brightening seemed to be modulated by the 2.4 day rotation of the star with the maximum of the radio flux at the predicted optical light maximum. The circularly polarized flux (Stokes parameter V) did not exactly follow changes of the flux f (Stokes parameter I), suggesting that separate flares but at the same active longitude were observed. Determinations of the degree of circular polarization V/I had low accuracy except during phases of the brightenings when V/I is not greater than + 0.1 was observed. 20 refs