Measurement of T tauri binaries using the Hubble Space Telescope Fine Guidance Sensors

We report measurements of young star multiples in the Taurus star-forming region using the Fine Guidance Sensors (FGS) of the HST. Of the eight confirmed IR-discovered multiples, the FGS detected six in visible light: DF Tau, ZZ Tau, V928 Tau, Elias 12, HV Tau, and GN Tau. The V-band magnitudes of the components range from 12.1 to 16.4 mag, and the observed separations range from 0 ''.042 to 0 ''.34. Component separations in DF Tau, ZZ Tau, HV Tau, and Elias 12 are sufficiently small that their binary orbital parameters could be determined in a few years. Our targets are quite red, and the FGS observations confirm the predicted sensitivity of the FGS in transfer function mode to extreme color indices.