Dynamical Masses of Low-mass Stars in the Taurus and Ophiuchus Star-forming Regions

We report new dynamical masses for five pre-main sequence (PMS) stars in the L1495 region of the Taurus starforming region (SFR) and six in the L1688 region of the Ophiuchus SFR. Since these regions have VLBA parallaxes, these are absolute measurements of the stars' masses and are independent of their effective temperatures and luminosities. Seven of the stars have masses < 0.6 M-circle dot,thus providing data in a mass range with little data, and of these, six are measured to precision < 5%. We find eight stars with masses in the range 0.09-1.1 M-circle dot that agree well with the current generation of PMS evolutionary models. The ages of the stars we measured in the Taurus SFR are in the range 1-3 Myr, and < 1 Myr for those in L1688. We also measured the dynamical masses of 14 stars in the ALMA archival data for Akeson & Jensen's Cycle 0 project on binaries in the Taurus SFR. We find that the masses of seven of the targets are so large that they cannot be reconciled with reported values of their luminosity and effective temperature. We suggest that these targets are themselves binaries or triples.