A multi-technique approach to identifying and/or constraining radial-velocity substellar companions

Context. Although more than one thousand substellar companions have already been detected with the radial velocity (RV) method, many new companions remain to be detected in the public RV archives.
Aims: We wish to use the archival data obtained with the ESO/HARPS spectrograph to search for substellar companions.
Methods: We used the astronomic acceleration measurements of stars obtained with the HIPPARCOS and Gaia satellites to identify anomalies that could be explained by the presence of a companion. Once hints for a companion were found, we combined the RV data with absolute astrometry data and, when available, relative astrometry data, using a Markov chain Monte Carlo algorithm to determine the orbital parameters and mass of the companion.
Results: We find and characterize three new brown dwarfs (GJ 660.1 C, HD 73256 B, and HD 165131 B) and six new planets (HD 75302 b, HD 108202 b, HD 135625 b, HD 185283 b, HIP 10337 b, and HIP 54597 b) with separations between 1 and 6 au and masses between 0.6 and 100 M_Jup. We also constrain the orbital inclination of ten known substellar companions and determine their true mass. Finally, we identify twelve new stellar companions. This shows that the analysis of proper motion anomalies enables the optimization of the RV search for substellar companions and their characterization.