# Combining Gaia and GRAVITY: Characterising Five New Directly Detected Substellar Companions

**Authors:** T. O. Winterhalder, S. Lacour, A. Mérand, A. -L. Maire, J. Kammerer, T. Stolker, N. Pourré, C. Babusiaux, R. Abuter, A. Amorim, R. Asensio-Torres, W. O. Balmer, M. Benisty, J. -P. Berger, H. Beust, S. Blunt, A. Boccaletti, M. Bonnefoy, H. Bonnet, M. S. Bordoni  
**arXiv:** [2403.13055](https://arxiv.org/abs/2403.13055)  
**Date:** 2024-03-19  
**Summary page:** https://www.summarizepaper.com/en/paper/2403.13055v1/

## Key points

- Importance of precise mass constraints in characterizing brown dwarfs and exoplanets
- Combination of Gaia mission and GRAVITY data expands sample of substellar companions with accurately measured dynamical masses
- Detection of seven previously unknown companions, five of which are substellar
- Discovery of Gaia DR3 2728129004119806464 B, the closest ever imaged substellar companion
- Validation of orbital solutions in the NSS two-body orbit catalogue and potential for future advancements with upcoming releases like Gaia's DR4 and GRAVITY+

## Summary

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The authors emphasize the importance of precise mass constraints in characterizing brown dwarfs and exoplanets. They demonstrate how combining data from the Gaia mission and GRAVITY can significantly expand the sample of substellar companions with accurately measured dynamical masses. By utilizing the Non-Single-Star (NSS) two-body orbit catalogue from Gaia DR3, they guide high angular resolution follow-up observations with GRAVITY to successfully detect eight predicted companions in eight Gaia candidate systems. This reveals seven previously unknown companions, five of which are substellar. Notably, they discover Gaia DR3 2728129004119806464 B, the closest ever imaged substellar companion at an angular separation of (34.01 ± 0.15) milliarcseconds from its host star, corresponding to a physical separation of (1.054 ± 0.002) astronomical units. The GRAVITY data not only resolve mass degeneracy but also aid in constraining orbital parameters and further characterizing these objects using evolutionary models. This work validates orbital solutions found in the NSS two-body orbit catalogue and highlights the potential for combining astrometric survey missions like Gaia with high-angular resolution direct imaging techniques such as GRAVITY to efficiently increase directly-imaged companions in future studies. It sets a promising foundation for future advancements, particularly with upcoming releases like Gaia's DR4 and advancements such as GRAVITY+.