Abstract

We determined the full orbital architecture and true mass of the recently Doppler-detected long-period giant planet GJ 463 b using the HIPPARCOS-Gaia proper motion anomaly in combination with the available radial velocities, constraints from the knowledge of the spectroscopic orbital parameters, and supplementary information from a sensitivity analysis of Gaia Data Release 3 astrometry. We determined an orbital inclination i_b = 152_‒3⁺² deg (for a prograde orbit) and a mass ratio q = 0.0070 ± 0.0007, corresponding to a true mass of the companion M_b = 3.6 ± 0.4 M_Jup. True mass determinations for a super-Jupiter companion at intermediate orbital separations beyond the snow line around low-mass stars (M_⋆ ≤ 0.5 M_☉) are a rare occurrence. Its existence is possibly explained in the context of disk-instability models of planet formation.