The HARPS search for southern extra-solar planets
1 Université Grenoble Alpes, IPAG, 38000 Grenoble, France
2 CNRS, IPAG, 38000 Grenoble, France
3 Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
4 Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS, Université de Provence, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
5 Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bat. B5C, 4000 Liège, Belgium
6 Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN, Brazil
7 Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK
8 Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
9 Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
10 Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Portugal
Received: 22 May 2014
Accepted: 25 November 2014
Context. Planetary companions of a fixed mass induce reflex motions with a larger amplitude around lower-mass stars, which adds to making M dwarfs excellent targets for extra-solar planet searches. The most recent velocimeters with a stability of ~1 m s-1 can detect very low-mass planets out to the habitable zone of these stars. Low-mass small planets are abundant around M dwarfs, and most of the known potentially habitable planets orbit one of these cool stars.
Aims. Our M-dwarf radial velocity monitoring with HARPS on the ESO 3.6 m telescope at La Silla observatory makes a major contribution to this sample.
Methods. We present here dense radial velocity (RV) time series for three M dwarfs observed over ~five years: GJ 3293 (0.42 M⊙), GJ 3341 (0.47 M⊙), and GJ 3543 (0.45 M⊙). We extracted these RVs through minimum χ2-matching of each spectrum against a stack of all observed spectra for the same star that has a high signal-to-noise ratio. We then compared potential orbital signals against several stellar activity indicators to distinguish the Keplerian variations induced by planets from the spurious signals that result from rotational modulation of stellar surface inhomogeneities and from activity cycles.
Results. Two Neptune-mass planets – msin(i) = 1.4 ± 0.1 and 1.3 ± 0.1Mnept – orbit GJ 3293 with periods P = 30.60 ± 0.02 d and P = 123.98 ± 0.38 d, possibly together with a super-Earth – msin(i) ~ 7.9 ± 1.4 M⊕ – with period P = 48.14 ± 0.12d. A super-Earth – msin(i) ~ 6.1 M⊕ – orbits GJ 3341 with P = 14.207 ± 0.007d. The RV variations of GJ 3543, on the other hand, reflect its stellar activity rather than planetary signals.
Key words: techniques: radial velocities / stars: late-type / stars: individual: GJ 3293 / stars: individual: GJ 3341 / stars: individual: GJ 3543 / planetary systems
Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the program IDs 072.C-0488, 082.C-0718 and 183.C-0437 at Cerro La Silla (Chile).
Tables A.1–A.3 (radial velocity data) are available in electronic form at http://www.aanda.org and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A119
© ESO, 2015