Volume 507, Number 1, November III 2009
|Page(s)||487 - 494|
|Section||Planets and planetary systems|
|Published online||24 September 2009|
The HARPS search for southern extra-solar planets*
XVIII. An Earth-mass planet in the GJ 581 planetary system
Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland e-mail: email@example.com
2 Laboratoire d'Astrophysique, Observatoire de Grenoble, Université J. Fourier, CNRS (UMR5571), BP 53, 38041 Grenoble, Cedex 9, France
3 Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
4 Service d'Aéronomie du CNRS, BP 3, 91371 Verrières-le-Buisson, France
5 Institut d'Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France
6 Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, P4150-762 Porto, Portugal
Accepted: 14 June 2009
The GJ 581 planetary system is already known to harbour three planets, including two super-Earth planets that straddle its habitable zone. We report the detection of an additional planet – GJ 581e – with a minimum mass of 1.9 . With a period of 3.15 days, it is the innermost planet of the system and has a ~5% transit probability. We also correct our previous confusion about the orbital period of GJ 581d (the outermost planet) with a one-year alias, benefitting from an extended time span and many more measurements. The revised period is 66.8 days, and positions the semi-major axis inside the habitable zone of the low mass star. The dynamical stability of the 4-planet system imposes an upper bound on the orbital plane inclination. The planets cannot be more massive than approximately 1.6 times their minimum mass.
Key words: planetary systems / stars: late-type / techniques: radial velocities / stars: individual: GJ 581
Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the GTO and LP programs 072.C-0488 and 183.C-0437 at Cerro La Silla (Chile). Our radial-velocity, photometric and Ca II H+K index time series (Table 1) are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/507/487
© ESO, 2009
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