Orbital Period Variation in the Chromospherically Active Binary FF UMa (2RE J0933+624)

We present here a detailed study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary system with strong H 5 x 10- 4, which is larger than the variations found in other similar chromospherically active binaries like AR Lac and HR 1099. This orbital period variation can be related (Applegate 1992; Lanza 1998, 2006) with the modulation of the gravitational quadrupole-moment of its magnetically active secondary star produced by angular momentum exchanges within its convective envelope. In addition, using these observations, we have determined the stellar parameters of the components and we have carried out a study of the chromospheric activity using all the optical indicators from Ca ii H& K to Ca ii IRT lines.