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http://hdl.handle.net/20.500.12386/29678
Titolo: | Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs | Autori: | Zhang, Z. H. Pinfield, D. J. Gálvez-Ortiz, M. C. Homeier, D. Burgasser, A. J. Lodieu, N. Martín, E. L. Zapatero Osorio, M. R. Allard, F. Jones, H. R. A. SMART, Richard Laurence López Martí, B. Burningham, B. Rebolo, R. |
Data pubblicazione: | 2018 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 479 | Fascicolo: | 1 | Da pagina:: | 1383 | Abstract: | 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 T<SUB>eff</SUB> around 2050-2250 K, -1.8 ≤ [Fe/H] ≤ -1.5, and mass around 0.0822-0.0833 M<SUB>☉</SUB>, 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<SUB>☉</SUB> at [Fe/H] = -1.6 and ∼ 0.0855 M<SUB>☉</SUB> 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. | URI: | http://hdl.handle.net/20.500.12386/29678 | URL: | https://academic.oup.com/mnras/article-abstract/479/1/1383/5001885 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/sty1352 | Bibcode ADS: | 2018MNRAS.479.1383Z | Fulltext: | open |
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