Pan-Pacific survey clarifies the nature of six candidate companions orbiting evolved stars

Star system: HD 126105 | Distance from the Sun: 268 light years

The Pan-Pacific Planet Search was a six-year survey that monitored 164 southern evolved stars to detect potential orbiting companions using radial-velocity measurements, which track the slight wobble of a star caused by the gravitational pull of orbiting objects. In their final data release, researchers aimed to resolve the true nature of six speculative candidates that had been identified during the survey.

By combining new radial-velocity data with observations from the Transiting Exoplanet Survey Satellite (TESS) and precise astrometric measurements from the Hipparcos and Gaia space missions, the team was able to determine the status of these objects. These combined methods allowed researchers to move beyond the limitations of earlier, incomplete radial-velocity datasets.

The study confirmed that HD 126105b is a giant planet, while HD 205577B is a massive, eccentric brown dwarf — an object larger than a planet but smaller than a star. Additionally, HD 115066B and HD 121156B were identified as low-mass stellar companions. Conversely, the analysis revealed that the stars HD 114899 and HD 159743 do not have any detectable companions, showing that some previous candidate signals were not caused by orbiting objects.

Key findings
- HD 126105b is confirmed to be a giant planet.
- HD 205577B is confirmed to be a massive, eccentric brown dwarf.
- HD 115066B and HD 121156B are identified as low-mass stellar companions.
- HD 114899 and HD 159743 are determined to have no detectable companions.
- The study highlights the importance of astrometric data in verifying potential exoplanet and stellar companions.

Scientific study

The Pan-Pacific Planet Search -- IX. A menagerie of companions orbiting evolved stars (external link)