Astrometry of brown dwarfs with Gaia

TL;DR

Gaia's precise astrometry will significantly advance brown dwarf science by providing absolute parallaxes for thousands of objects, enabling new spectral classifications and expanding the nearby brown dwarf sample.

Contribution

This paper highlights Gaia's potential to improve brown dwarf measurements and proposes extending its faint limit to enhance scientific outcomes.

Findings

Gaia will measure parallaxes for thousands of brown dwarfs with sub-milliarcsecond accuracy.

Lowering Gaia's faint limit from 20 to 21 mag could add two spectral subclasses.

Expanding the sample increases the volume of the solar neighborhood studied.

Abstract

Europe's Gaia spacecraft will soon embark on its five-year mission to measure the absolute parallaxes of the complete sample of 1,000 million objects down to 20 mag. It is expected that thousands of nearby brown dwarfs will have their astrometry determined with sub-milli-arcsecond standard errors. Although this level of accuracy is comparable to the standard errors of the relative parallaxes that are now routinely obtained from the ground for selected, individual objects, the absolute nature of Gaia's astrometry, combined with the sample increase from one hundred to several thousand sub-stellar objects with known distances, ensures the uniqueness of Gaia's legacy in brown-dwarf science for the coming decade(s). We shortly explore the gain in brown-dwarf science that could be achieved by lowering Gaia's faint-end limit from 20 to 21 mag and conclude that two spectral-type sub-classes could be gained in combination with a fourfold increase in the solar-neighbourhood-volume sampled by Gaia and hence in the number of brown dwarfs in the Gaia Catalogue.