Fontanive, C.C.FontaniveBEDIN, LuigiLuigiBEDINBardalez Gagliuffi, D. C.D. C.Bardalez Gagliuffi2023-01-232023-01-2320210035-8711http://hdl.handle.net/20.500.12386/33004In this paper, we present our project that aims at determining accurate distances and proper motions for the Y brown dwarf population using the Hubble Space Telescope. We validate the program with our first results, using a single new epoch of observations of the Y0pec dwarf WISE J163940.83-684738.6. These new data allowed us to refine its proper motion and improve the accuracy of its parallax by a factor of three compared to previous determinations, now constrained to ϖ = 211.11 ± 0.56 mas. This newly derived absolute parallax corresponds to a distance of 4.737 ± 0.013 pc, an exquisite and unprecedented precision for faint ultracool Y dwarfs.STAMPAenArticle10.1093/mnras/staa37322-s2.0-85100386344https://academic.oup.com/mnras/article/501/1/911/6017306http://arxiv.org/abs/2011.13873v12021MNRAS.501..911FFIS/05 - ASTRONOMIA E ASTROFISICA