The SPIRou Legacy Survey

Context. Advancements in the field of exoplanetary research have extended radial velocity (RV) observations from the optical to the near-infrared (nIR) domain. M dwarf stars, characterized by their lower masses and higher prevalence of rocky planets, have become a focal point of investigation. This study uses data from the nIR spectropolarimeter SPIRou and data available in the literature from the HARPS and CARMENES spectrographs operating in the optical to analyze RVs of two nearby M dwarfs, Gl 480 and Gl 382. Aims. In this work our aims is to detect and characterize exoplanetary companions around Gl 480 and Gl 382 by mitigating stellar activity effects through advanced data analysis techniques. The study seeks to improve the reliability of RV signals by integrating multi-wavelength observations and stellar activity diagnostics. Methods. The study employs a comprehensive approach that combines the line-by-line (LBL) framework with the Weighted principAl comPonent analysIs reconsTructIon (Wapiti) method to correct for systematics in SPIRou data. Through an extensive analysis of available stellar activity indicators and by combining optical data from the HARPS and CARMENES instruments, we perform a joint analysis of RV measurements in the nIR and the optical domains. Results. Our analysis confirms the detection of a planet orbiting Gl 480 with a period of 9.5537 ± 0.0005 d and a minimum mass of 8.8 ± 0.7 M ⊕ . Additionally, we detect a tentative signal at 6.4 d, whose significance strongly depends on the choice of Gaussian process priors constrained by stellar activity indicators and would require further observations for confirmation. In contrast, no planetary signals are detected for Gl 382, where RV variations are dominated by stellar activity.