{
  "id": "1911.12378",
  "version": "v1",
  "published": "2019-11-27T19:00:28.000Z",
  "updated": "2019-11-27T19:00:28.000Z",
  "title": "Dynamical Masses of Young Stars II: Young Taurus Binaries Hubble~4, FF~Tau, and HP~Tau/G3",
  "authors": [
    "Aaron C Rizzuto",
    "Trent J. Dupuy",
    "Michael J. Ireland",
    "Adam L. Kraus"
  ],
  "comment": "14 pages, 6 figures, 8 tables, accepted for publication in ApJ",
  "categories": [
    "astro-ph.SR",
    "astro-ph.EP",
    "astro-ph.GA"
  ],
  "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 VLBI parallaxes. We obtained precision astrometry with Keck-II/NIRC2, optical photometry with HST/WFC3, 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 SED determined component temperatures and luminosities agree with the dynamical masses, with a small offset towards larger model masses. We find model ages for the primary components of these systems of $\\sim$3 Myr, but find that the secondaries appear younger by a factor of two. These estimates also disagree with the age of the physically associated G-type star HP~Tau/G2, which is older ($\\sim$5 Myr) according to the same models. This discrepancy is equivalent to a luminosity under-prediction of 0.1-0.2 dex, or a temperature over-prediction 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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-11-27T19:00:28.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "dynamical masses",
      "young taurus binaries",
      "young stars",
      "binary system",
      "test stellar evolutionary models"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}