WISE J181005.5-101002.3: the nearest metal-poor brown dwarf ?

WISE1810-10 is the brightest metal-poor T-type object reported by Schneider et al. (2020) in a WISE search for ultracool dwarfs with high proper motions and peculiar colours. We conducted an extensive photometric and spectroscopic follow-up with a battery of telescopes and instruments (GTC, Calar Alto, NOT) to characterise the physical properties of the metal-poor brown dwarf population. We detected WISE1810 in the i and z bands for the first time. We also present a low-resolution optical spectrum for the first time. Thanks to a photometric monitoring of several years, we measure a relative trigonometric parallax of 112.2+/-8.2 mas for WISE1810-10, placing it within 10 pc, about three times closer than previously thought. We calculated the luminosity of WISE1810-10 to be log(L/Lsun) = -5.72+/-0.18 dex, making it sub-luminous with respect to the sequence of solar-metallicity L and T dwarfs. We confirm that WISE1810-10 has a very low temperature (<=1000K) and belongs to a new class of objects with no known spectral counterparts among field L- and T-type dwarfs, with a metallicity most likely in the range between -1.5 dex and -1.0 dex by
comparison with predictions from atmospheric models. The revised distance of WISE1810-10 has a strong implication on the density of metal-poor brown dwarfs in our Galaxy.

Reference: Lodieu et al. (2022, A&A, 663, 84)