title: Exoplanet detection. Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581.
abstract: The M dwarf star Gliese 581 is believed to host four planets, including one (GJ 581d) near the habitable zone that could possibly support liquid water on its surface if it is a rocky planet. The detection of another habitable-zone planet--GJ 581g--is disputed, as its significance depends on the eccentricity assumed for d. Analyzing stellar activity using the Hα line, we measure a stellar rotation period of 130 ± 2 days and a correlation for Hα modulation with radial velocity. Correcting for activity greatly diminishes the signal of GJ 581d (to 1.5 standard deviations) while significantly boosting the signals of the other known super-Earth planets. GJ 581d does not exist, but is an artifact of stellar activity which, when incompletely corrected, causes the false detection of planet g.
authors.affiliation: Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA. Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802, USA. pmr19@psu.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Robertson
authors.affiliation: Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA. Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802, USA. The Penn State Astrobiology Research Center, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Suvrath
authors.initials: S
authors.lastname: Mahadevan
authors.affiliation: McDonald Observatory, The University of Texas at Austin, Austin, TX 78712-1206, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Endl
authors.affiliation: Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA. Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802, USA. The Penn State Astrobiology Research Center, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Arpita
authors.initials: A
authors.lastname: Roy