Primeval very low-mass stars and brown dwarfs – III. The halo transitional brown dwarfs - Archive ouverte HAL
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2018

Primeval very low-mass stars and brown dwarfs – III. The halo transitional brown dwarfs

M. C. Gálvez-Ortiz
  • Fonction : Auteur
A. J. Burgasser
  • Fonction : Auteur
N. Lodieu
  • Fonction : Auteur
E. L. Martín
  • Fonction : Auteur
M. R. Zapatero Osorio
  • Fonction : Auteur
B. López Martí
  • Fonction : Auteur
B. Burningham
  • Fonction : Auteur
R. Rebolo
  • Fonction : Auteur
Z Zhang (张曾华)
  • Fonction : Auteur
M Zapatero osorio
  • Fonction : Auteur
B López martí
  • Fonction : Auteur

Résumé

We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0, and a usdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfs by optical spectra obtained with the Gran Telescopio Canarias, and followed up by optical-to-near-infrared spectroscopy with the Very Large Telescope. We also obtained an optical-to-near-infrared spectrum of a previously known L subdwarf, ULAS J135058.85+081506.8, and reclassified it as a usdL3 subdwarf. These three objects all have typical halo kinematics. They have Teff around 2050-2250 K, -1.8 ≤ [Fe/H] ≤ -1.5, and mass around 0.0822-0.0833 M⊙, according to model spectral fitting and evolutionary models. These sources are likely halo transitional brown dwarfs with unsteady hydrogen fusion, as their masses are just below the hydrogen-burning minimum mass, which is ˜ 0.0845 M⊙ at [Fe/H] = -1.6 and ˜ 0.0855 M⊙ at [Fe/H] = -1.8. Including these, there are now nine objects in the `halo brown dwarf transition zone', which is a `substellar subdwarf gap' that spans a wide temperature range within a narrow mass range of the substellar population.

Dates et versions

hal-02280897 , version 1 (06-09-2019)

Identifiants

Citer

Z. H. Zhang, D. J. Pinfield, M. C. Gálvez-Ortiz, D. Homeier, A. J. Burgasser, et al.. Primeval very low-mass stars and brown dwarfs – III. The halo transitional brown dwarfs. Monthly Notices of the Royal Astronomical Society, 2018, 479 (1), pp.1383-1391. ⟨10.1093/mnras/sty1352⟩. ⟨hal-02280897⟩
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