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We perform a detailed characterization of the planetary system orbiting thebright, nearby M dwarf Gliese 411 using radial velocities gathered by APF,HIRES, SOPHIE, and CARMENES. We confirm the presence of a signal with a periodnear 2900 days that has been disputed as either a planet or a long-periodstellar magnetic cycle. An analysis of activity metrics including the$\mathrm{H_\alpha}$ and $\mathrm{log'R_{HK}}$ indices supports theinterpretation that the signal corresponds to a Neptune-like planet, GJ 411 c.An additional signal near 215 days was previously dismissed as an instrumentalsystematic, but we find that a planetary origin cannot be ruled out. With asemi-major axis of $0.5142\pm0.0042$ au, this candidate's orbit falls betweenthose of its companions and is located beyond the outer edge of the system'shabitable zone (determined using the moist greenhouse and maximum greenhouselimits in Kopparapu et al., 2013). It has a minimum mass of $4.1\pm0.6$$M_\oplus$, giving a radial-velocity amplitude of $0.81\pm0.18$$\mathrm{m\,s^{-1}}$. If confirmed, this would be one of the lowest-amplitudeplanet detections from any of these four instruments. Our analysis of the jointradial-velocity data set also provides tighter constraints on the orbitalparameters for the previously known planets. Photometric data from TESS do notshow any signs of a transit event. However, the outermost planet and candidateare prime targets for future direct imaging missions, and GJ 411 c may bedetectable via astrometry.

Confirmation of the Long-Period Planet Orbiting Gliese 411 and the Detection of a New Planet Candidate