Brown dwarfs are notoriously difficult to characterise due to their age-mass-temperature degeneracy. We overcome this by using T-dwarfs in wide binary systems: the properties of Gaia-detected primaries can be used to anchor the companion’s characteristics. By combining photometric data from the VISTA VHS and Dark Energy Survey, candidates were identified and followed up with new FourStar J-band images and FIRE prism spectra. These new observations established a longer 3-13 year baseline, enabling precise proper motion measurements and statistical confirmation of 10 T-dwarf/Gaia star pairs, five of which are previous unreported. Our sample is diverse, including M-dwarf primaries, a ~11.3 Gyr-old white dwarf primary and a very wide binary system. By assuming binary co-evolution, we estimate the T-dwarfs’ effective temperatures, masses and radii. Our sample yields vital new benchmarks for testing evolutionary models and improving our understanding of ultracool atmospheric physics.
Gemma Cheng (Mon,) studied this question.