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Orbit and Stellar Properties of the Young Triple V807 Tau

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We present new orbital measurements of the pre-main-sequence triple system, V807 Tau, using adaptive optics imaging at the Keck Observatory. We computed an orbit for the close pair, V807 Tau Ba--Bb, with a period of 12.312 or - 0.058 years and a semi-major axis of 38.59 or - 0.16 mas. By modeling the center of mass motion of the components in the close pair relative to the wide component, V807 Tau A, we measured a mass ratio of 0.843 or - 0.050 for BbBa. Combined with the total mass from the relative orbit, we derived individual masses of MBa 0.564 or - 0.018 d140 pc cubed solar mass and MBb 0.476 or - 0.017 d140 pc cubed solar mass at an average distance of 140 pc to the Taurus star-forming region. We computed spectral energy distributions to determine the luminosities of the three components. We also measured their spectral types, effective temperatures, and rotational velocities based on spatially resolved spectra obtained at the Keck Observatory. If the rotational axes are aligned, then the projected rotational velocities imply that V807 Tau Ba and Bb are rotating much faster than V807 Tau A. The uncertainty in the stellar effective temperatures and distance to the system currently limit the comparison of our dynamical mass measurements with predictions based on evolutionary tracks for pre-main-sequence stars. We also report preliminary results from a program to map the 3.6 cm radio emission from V807 Tau using the Very Long Baseline Array. With continued monitoring, these observations will provide a precise parallax for placing the dynamical masses on an absolute scale.

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  • Astrophysics

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