# Primeval very low-mass stars and brown dwarfs -- II. The most metal-poor substellar object

@article{Zhang2017PrimevalVL,
title={Primeval very low-mass stars and brown dwarfs -- II. The most metal-poor substellar object},
author={Z H Zhang and Derek Homeier and David J. Pinfield and Nicolas Lodieu and Hugh R. A. Jones and France Allard and Ya. V. Pavlenko},
journal={Monthly Notices of the Royal Astronomical Society},
year={2017},
volume={468},
pages={261-271}
}
• Published 7 February 2017
• Physics, Geology
• Monthly Notices of the Royal Astronomical Society
SDSS J010448.46+153501.8 has previously been classified as an sdM9.5 subdwarf. However, its very blue $J-K$ colour ($-0.15 \pm 0.17$) suggests a much lower metallicity compared to normal sdM9.5 subdwarfs. Here, we re-classify this object as a usdL1.5 subdwarf based on a new optical and near-infrared spectrum obtained with X-shooter on the Very Large Telescope. Spectral fitting with BT-Settl models leads to $T_{\rm eff}$ = 2450 $\pm$ 150 K, [Fe/H] = $-$2.4 $\pm$ 0.2 and log $g$ = 5.5 $\pm$ 0.25…

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