HIPPARCOS-Gaia PMA and Gaia DR3 sensitivity to companions of a given mass (in M_Jup) as a function of the orbital semi-major axis (in au) orbiting HD 75898. Dashed, dashed-dotted, and long-dashed lines correspond to iso-probability curves for 50, 90, and 99% probability of a companion of given properties to produce RUWE > 0.93. The solid black line identifies the combinations of mass and separation explaining the observed astrometric acceleration at the mean epoch of Gaia DR3 (based on the analytical formulation of Kervella et al. 2019). The shaded light-blue region corresponds to the 1σ uncertainty domain. The black star and red hexagon indicate the m sin i value (from RVs only) and the true mass value (combining RVs with astrometry, prograde orbit case) for HD 75898 c obtained in this work, respectively. The black cross identifies the location of HD 75898 b.