2018/05/22 by Z. H. Zhang, D. J. Pinfield, M. C. Galvez-Ortiz +17 · 1 citation
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Galactic halo #Galaxy #Halo #Low Mass #Massive compact halo object #Physics #Population #Stars #Stellar, planetary, and galactic studies #Subdwarf #White dwarf #astro-ph.SR
paper · pdf · doi:10.1093/mnras/sty1352
9 pages, 5 figures
openalex publication_date 2018/05/22 · arxiv created 2018/06/21 · arxiv updated 2018/06/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.