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

Z. H. Zhang, D. Homeier, D. J. Pinfield +4

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…