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        Primeval very low-mass stars and brown dwarfs - IV. New L subdwarfs, Gaia astrometry, population properties, and a blue brown dwarf binary

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        1807.10560v4_aam_cs.pdf (PDF, 7Mb)
        Author
        Zhang, Z. H.
        Galvez-Ortiz, M. C.
        Pinfield, D. J.
        Burgasser, A. J.
        Lodieu, N.
        Jones, H. R. A.
        Martin, E. L.
        Burningham, B.
        Homeier, D.
        Allard, F.
        Osorio, M. R. Zapatero
        Smith, L. C.
        Smart, R. L.
        Marti, B. Lopez
        Marocco, F.
        Rebolo, R.
        Attention
        2299/20913
        Abstract
        We present 27 new L subdwarfs and classify five of them as esdL and 22 as sdL. Our L subdwarf candidates were selected with the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Spectroscopic follow-up was carried out primarily with the OSIRIS spectrograph on the Gran Telescopio Canarias. Some of these new objects were followed up with the X-shooter instrument on the Very Large Telescope. We studied the photometric properties of the population of known L subdwarfs using colour-spectral type diagrams and colour-colour diagrams, by comparison with L dwarfs and main-sequence stars, and identified new colour spaces for L subdwarf selection/study in current and future surveys. We further discussed the brown dwarf transition-zone and the observational stellar/substellar boundary. We found that about one-third of 66 known L subdwarfs are substellar objects, with two-thirds being very low-mass stars. We also present the Hertzsprung-Russell diagrams, spectral type-absolute magnitude corrections, and tangential velocities of 20 known L subdwarfs observed by the Gaia astrometry satellite. One of our L subdwarf candidates, ULAS J233227.03+123452.0, is a mildly metal-poor spectroscopic binary brown dwarf: a ~L6p dwarf and a ~T4p dwarf. This binary is likely a thick disc member according to its kinematics.
        Publication date
        2018-11-11
        Published in
        Monthly Notices of the Royal Astronomical Society
        Published version
        https://doi.org/10.1093/mnras/sty2054
        Other links
        http://hdl.handle.net/2299/20913
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