Do We Finally Know all Stellar and Substellar Neighbors within 10 pc of the Sun?

Abstract

Our knowledge on the closest solar neighbors gradually improved over a long time with the help of new methods and the recognition of new stellar and substellar species. The latest burst of discoveries since 1997, in which the first author participated, seemingly filled the gap of missing systems within 10 pc from the Sun. However, previous estimates of the population relied on two assumptions: that the sample was complete within 5 pc and that the density was uniform out to 10 pc. The first of these is not true, and the second in question. Otherwise, up to about 90 systems could be still missing within 10 pc. We find no indication for missing brown dwarfs within 10 pc, but strongly increasing deficits from early-M to late-M dwarfs hint at some still hidden late-M dwarf neighbors. They may have already been detected by Gaia but published so far without or with incorrect parallax measurements, because of close companions or their location in the Galactic plane.