2025AJ....169..182D

Gl 229 is a well-known system hosting the first confirmed brown dwarf (BD), Gl 229 B, discovered in 1995. Subsequent radial velocity (RV) follow-up of the star unveiled, in 2014, an exoplanet on a 471 days orbit with a minimum mass of ∼32 M_⊕. In 2020, a second exoplanet with a 122 days orbital period and a minimum mass of approximately 7 M_⊕ was reported. With its BD, now a known binary, and two exoplanets, Gl 229 has been deemed one of the most diverse systems and has sparked discussions regarding the different formation mechanisms that could have taken place around this star. This work presents a new analysis of the publicly available Gl 229 High Accuracy Radial Velocity Planet Searcher data reduced with the line-by-line precision RV algorithm resistant to spectral outliers. We find strong evidence for stellar activity impacting RV measurements. Stellar activity-induced RVs were modelled with a Gaussian process trained on the activity indicator provided by the algorithm, revealing the star's rotation period at 28.9 ± 1.6 days. We show that systematic errors and stellar activity are the most likely cause of the previously reported exoplanet signals. Our analysis provides a 3σ upper limit of 9.1 M_⊕ for a planet in the system's habitable zone except for the periods close to the star's rotation period, where stellar activity worsens the limit to around 15 M_⊕.