Torres, Rosa M. and Loinard, Laurent and Mioduszewski, Amy J. and Boden, Andrew F. and Franco-Hernández, Ramiro and Vlemmings, Wouter H. T. and Rodríguez, Luis F. (2012) VLBA Determination of the Distance to Nearby Star-Forming Regions. V. Dynamical Mass, Distance and Radio Structure of V773 Tau A. Astrophysical Journal, 747 (1). Art. No. 18. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120328-134947502
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We present multi-epoch Very Long Baseline Array (VLBA) observations of V773 Tau A, the 51 day binary subsystem in the multiple young stellar system V773 Tau. Combined with previous interferometric and radial velocity measurements, these new data enable us to improve the characterization of the physical orbit of the A subsystem. In particular, we infer updated dynamical masses for the primary and the secondary components of 1.55 ± 0.11 M_☉ and 1.293 ± 0.068 M_☉, respectively, and an updated orbital parallax distance to the system of 135.7 ± 3.2 pc, all consistent with previous estimates. Using the improved orbit, we can calculate the absolute coordinates of the barycenter of V773 Tau A at each epoch of our VLBA observations, and fit for its trigonometric parallax and proper motion. This provides a direct measurement of the distance to the system almost entirely independent of the orbit modeling. The best fit yields a distance of 129.9 ± 3.2 pc, in good agreement (i.e., within 1σ) with the distance estimate based on the orbital fit. Taking the mean value of the orbital and trigonometric parallaxes, we conclude that V773 Tau is located at d = 132.8 ± 2.3 pc. The accuracy of this determination is nearly one order of magnitude better than that of previous estimates. In projection, V773 Tau and two other young stars (Hubble 4 and HDE 283572) recently observed with the VLBA are located toward the dark cloud Lynds 1495, in the central region of Taurus. These three stars appear to have similar trigonometric parallaxes, radial velocities, and proper motions, and we argue that the weighted mean and dispersion of their distances (d = 131.4 pc and σ_d = 2.4 pc) provide a good estimate of the distance to and depth of Lynds 1495 and its associated stellar population. The radio emission from the two sources in V773 Tau A is largely of gyrosynchrotron origin. Interestingly, both sources are observed to become typically five times brighter near periastron than near apastron (presumably because of increased flaring activity), and the separation between the radio sources near periastron appears to be systematically smaller than the separation between the stars. While this clearly indicates some interaction between the individual magnetospheres, the exact mechanisms at play are unclear because even at periastron the separation between the stars (~30 R_*) remain much larger than the radius of the magnetospheres around these low-mass young stars (~6 R_*).
|Additional Information:||© 2012 American Astronomical Society. Received 2011 March 18; accepted 2011 November 30; published 2012 February 10. R.M.T. and W.H.T.V. acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) through the Emmy Noether Research grant VL 61/3-1. L.L. and L.F.R. acknowledge the financial support of DGAPA, UNAM, and CONACyT, México. L.L. acknowledges financial support from the Guggenheim Foundation and the von Humboldt Stiftung. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.|
|Subject Keywords:||astrometry; binaries: spectroscopic; radio continuum: stars; stars: formation; stars: individual (V773 Tau); stars: pre-main sequence|
|Official Citation:||VLBA Determination of the Distance to nearby Star-forming Regions. V. Dynamical Mass, Distance, and Radio Structure of V773 Tau A Rosa M. Torres et al. 2012 ApJ 747 18|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||28 Mar 2012 22:55|
|Last Modified:||26 Dec 2012 15:00|
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