New Orbital Constraints for YSES 1 b and HR 2562 B from High-Precision Astrometry and Planetary Radial Velocities
Jonathan Roberts, William Thompson, Jason J. Wang, Sarah Blunt, William O. Balmer, Guillaume Bourdarot, Brendan P. Bowler, Gael Chauvin, Frank Eisenhauer, Thomas K. Henning, Jens Kammerer, Flavien Kiefer, Matthew A. Kenworthy, Pierre Kervella, Sylvestre Lacour, A. -M. Lagrange, Eric L. Nielsen, Laurent Pueyo, Emily Rickman, Olli Sipilä, Silvia Spezzano, Tomas Stolker, Alice Zurlo
Published: 2025/9/17
Abstract
We present new VLTI/GRAVITY astrometry and updated orbit fits for the directly imaged companions YSES 1 b and HR 2562 B, substellar objects straddling the planet-brown dwarf boundary. Using high-precision astrometry, radial velocity (RV) data, and proper motions, we derive revised orbital parameters with orbitize! arXiv:1910.01756. For YSES 1 b, the inclusion of GRAVITY astrometry and a relative radial velocity measurement from arXiv:2409.16660 overcomes the traditional challenge of constraining eccentricities for distant companions, enabling the first orbit fit and yielding a constrained eccentricity of 0.44 (0.20). This represents the first full orbit fit for the system. Additionally, we calculate a median line-of-sight stellar obliquity of 12 (+11, -8) degrees, providing further insight into the system's dynamical architecture. For HR 2562 B, our analysis agrees with arXiv:2302.04893, confirming a low-eccentricity orbit (0.34 (0.20)) and an inclination of 87 (1) degrees. We find HR 2562 B's orbit to be nearly coplanar with the debris disk, with a mutual inclination of 3.7 (0.3) degrees. For both YSES 1 b and HR 2562 B the lower eccentricities favor an in situ formation scenario over extreme scattering or cloud fragmentation.