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A Neptune-Mass Planet Orbiting The Nearby M Dwarf Gj 436, R. Paul Butler, Steve S. Vogt, Geoffrey W. Marcy, Debra A. Fischer, Jason T. Wright, Gregory W. Henry, Gregory Laughlin, Jack J. Lissauer

Information Systems and Engineering Management Research Publications

We report precise Doppler measurements of GJ 436 (M2.5 V) obtained at Keck Observatory. The velocities reveal a planetary companion with orbital period of 2.644 days, eccentricity of 0.12 (consistent with zero), and velocity semiamplitude of K = 18.1 m s-1. The minimum mass (M sin i) for the planet is 0.067MJup = 1.2MNep = 21MEarth, making it the lowest mass exoplanet yet found around a main-sequence star and the first candidate in the Neptune-mass domain. GJ 436 (mass = 0.41 M☉) is only the second M dwarf found to harbor a planet, joining the two-planet system around GJ 876. …