Lessons learned from the detection of wide companions by radial velocity and astrometry

The detection and constraint of the orbits of long-period giant planets is essential for enabling their further study through direct imaging. Recently, Venner et al. (2024) highlighted discrepancies between the solutions presented by Feng et al. (2022) and those from other studies, which primarily use orvara. We address these concerns by reanalyzing the data for HD 28185, GJ 229, HD 211847, GJ 680, HD 111031, and eps Ind A, offering explanations for these discrepancies. Based on a comparison between the methods used by Feng et al. (2022) and orvara, we find the discrepancies are primarily data-related rather than methodology-related. Our re-analysis of HD 28185 highlights many of the data-related issues and particularly the importance of parallax modeling for year-long companions. The case of eps Ind A b is instructive to emphasize the value of an extended RV baseline for accurately determining orbits of long period companions. Our orbital solutions highlight other causes for discrepancies between solutions including the combination of absolute and relative astrometry, clear definitions of conventions, and efficient posterior sampling for the detection of wide-orbit giant planets.