SIMBAD references

We present recent measurements of the orbital motion in the young binaries DF Tau and ZZ Tau and the hierarchical triple Elias 12 that were obtained with the Fine Guidance Sensors on the Hubble Space Telescope and at the Keck Observatory using adaptive optics. Combining these observations with previous measurements from the literature, we compute preliminary orbital parameters for DF Tau and ZZ Tau. We find that the orbital elements cannot yet be determined precisely because the orbital coverage spans only ∼90° in position angle. Nonetheless, the range of possible values for the period and semimajor axis already defines a useful estimate for the total mass in DF Tau and ZZ Tau, with values of 0.90^+0.85_–0.35and 0.81^+0.44_–0.25M_☉, respectively, at a fiducial distance of 140 pc.