Doppler imaging of stellar surface structure VI. HD 129333 = EK Draconis: a stellar analog of the active young Sun

We present the rst Doppler images of the single G1.5V-star EK Draconis from high-resolution CFHT spectra obtained in 1995. EK Dra is an important target for investi- gating the evolution of stellar magnetism because it resembles the rapidly-rotating young Sun. From the inversion of a total of 12 spectral lines we reconstruct several cool spots at low and medium latitudes but the dominating feature is located con- sistently at a latitude of 70{80, thus, at far higher latitudes than where our Sun shows spots. In fact, our data indicate that this feature could be an appendage of a larger polar cap-like spot as seen on other rapidly-rotating stars, however, due to the small v sini of just 17.30.4 kms 1 the cap's existence re- mains inconclusive. Spot temperatures between T 1200 K and 400 K are recovered. We have used the non-parametrized convective-fluxdescriptionofCanuto&Mazzitelliforourinput model atmospheres and found good agreement with local line proles computed from standard mixing-length atmospheres. New phase-resolved UBV RI data spanning the 1996/97 observing season indicate a surprisingly short photometric pe- riod of 2.5990.001 days, which is different by 7% from the longest seasonal period found so far but in good agreement with the long-term photometric period of 2.605 days. We interpret these differences as being due to differential surface rotation and adopt the long-term photometric period to be the rotation period of EK Dra. Our data also conrms the continuing de- cline of the mean brightness seen since 1994 and we suspect the high-latitude feature to be the cause.