ORBITAL MOTION OF DF TAURI FROM SPECKLE INTERFEROMETRY

We report the evidence of the orbital motion of the binary star DF Tau . This result is obtained from visible speckle interferometry and uses lunar occultations of Chen et al. (1990). It is the first step toward s a direct determination of the dynamical mass of this young system. T he portion of the orbit covered between tile epochs of observation is still too small (similar to 10%) to allow precise derivation of the or bital elements. We however provide a first estimate of the mass of the system as being 2.8 +/- 1.5 M(.). We investigate the incidence of the binarity of DF Tau on the modeling of its spectral energy distributio n and discuss the nature of the components.