How many terrestrial planets orbit Barnard's star?

Barnard's star is a nearby M-dwarf with a long history of challenged planet detections. Following the recent reports of a four-planet system, we perform a complementary analysis to confirm the proposed orbital configuration. We utilize a combined dataset of 900 RV and 789 FWHM measurements from five spectrographs. Our frequency-domain analysis reveals high coherence between the RV and FWHM data at the frequency of Barnard d, suggesting a potential origin related to stellar activity. Furthermore, we find evidence that the signals of planets d and e may be related as aliases. Using the Bayesian Information Criterion (BIC) and the Likelihood Ratio Test (LRT) for model selection, our analysis consistently favors a three-planet model (Barnard b, c, and d), which shows a significant BIC improvement over a four-planet system. Finally, analysis of the RV residuals reveals a previously unreported signal at a 2.78-day period above the 5% false alarm threshold, which we designate as planet candidate f. Our results suggest that the architecture of Barnard's star planetary system requires further study. Our current hypothesis is that the system is best modeled by three short-period terrestrial planets (b, c, and d), with a new potential candidate, Barnard f.