Primeval very low-mass stars and brown dwarfs - I. Six new L subdwarfs, classification and atmospheric properties
Abstract
We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or near-infrared wavelengths. We also present new optical spectra of three previously known L subdwarfs (WISEA J001450.17-083823.4, 2MASS J00412179+3547133, and ULAS J124425.75+102439.3). We examined the spectral type and metallicity classification of subclasses of known L subdwarfs. We summarized the spectroscopic properties of L subdwarfs with different spectral types and subclasses. We classify these new L subdwarfs by comparing their spectra to known L subdwarfs and L dwarf standards. We estimate temperatures and metallicities of 22 late-type M and L subdwarfs by comparing their spectra to BT-Settl models. We find that L subdwarfs have temperatures between 1500 and 2700 K, which are higher than similar-typed L dwarfs by around 100-400 K depending on different subclasses and subtypes. We constrained the metallicity ranges of subclasses of M, L, and T subdwarfs. We also discussed the spectral-type and absolute magnitude relationships for L and T subdwarfs.
Keywords
brown dwarfs
stars: chemically peculiar
stars: individual: ULAS J021642.97+004005.6
ULAS J124947.04+095019.8
SDSS J133348.24+273508.8
ULAS J133836.97-022910.7
SDSS J134749.74+333601.7
ULAS J151913.03-000030.0
stars: low-mass
stars: Population II
subdwarfs
Astrophysics - Solar and Stellar Astrophysics
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