Dynamical Masses of Young Stars. II. Young Taurus Binaries Hubble 4, FF Tau, and HP Tau/G3
Abstract
One of the most effective ways to test stellar evolutionary models is to measure dynamical masses for binary systems at a range of temperatures. In this paper, we present orbits of three young K+M binary systems in Taurus (Hubble 4, FF Tau, and HP Tau/G3) with very long baseline interferometry parallaxes. We obtained precision astrometry with Keck II/NIRC2, optical photometry with Hubble Space Telescope/Wide Field Camera 3, and low-resolution optical spectra with WIFeS on the ANU 2.3 m telescope. We fit orbital solutions and dynamical masses with uncertainties of 1%-5% for the three binary systems. The spectrum, photometry, and mass for Hubble 4 are inconsistent with a binary system, suggesting that it may be a triple system where the primary component consists of two stars. For HP Tau/G3 and FF Tau, model masses derived from spectral energy distribution-determined component temperatures and luminosities agree with the dynamical masses, with a small offset toward larger model masses. We find model ages for the primary components of these systems of ∼3 Myr, but find that the secondaries appear younger by a factor of two. These estimates also disagree with the age of the physically associated G-type star HP Tau/G2, which is older (∼5 Myr) according to the same models. This discrepancy is equivalent to a luminosity underprediction of 0.1-0.2 dex, or a temperature overprediction of 100-300 K, for K/M-type stars at a given model age. We interpret this as further evidence for a systematic error in pre-main-sequence evolutionary tracks for convective stars. Our results reinforce that the ages of young populations determined from the locus of M-type members on the HR diagram may require upward revision.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2020
- DOI:
- 10.3847/1538-4357/ab5aed
- arXiv:
- arXiv:1911.12378
- Bibcode:
- 2020ApJ...889..175R
- Keywords:
-
- Binary stars;
- Fundamental parameters of stars;
- Interferometry;
- Pre-main sequence stars;
- Star forming regions;
- 154;
- 555;
- 808;
- 1290;
- 1565;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 14 pages, 6 figures, 8 tables, accepted for publication in ApJ