RESEARCH
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The HARPS search for southern extra-solar planets
XXXIV. A planetary system around the nearby M dwarf GJ 163, with a super-Earth possibly in the habitable zone

X. Bonfils, G. Lo Curto, A. C. M. Correia, J. Laskar, S. Udry, X. Delfosse, T. Forveille, N. Astudillo, W. Benz, F. Bouchy, M. Gillon, G. Hťbrard, C. Lovis, M. Mayor, C. Moutou, D. Naef, V. Neves, F. Pepe, C. Perrier, D. Queloz, N. C. Santos, D. Sťgransan

Abstract
The meter-per-second precision achieved by today’s velocimeters enables us to search for 1-10 M planets in the habitable zone of cool stars. This paper reports on the detection of three planets orbiting GJ 163 (HIP 19394), a M3 dwarf monitored by our ESO/HARPS search for planets. We made use of the HARPS spectrograph to collect 150 radial velocities of GJ 163 over a period of eight years.
We searched the radial-velocity time series for coherent signals and found five distinct periodic variabilities. We investigated the stellar activity and called into question the planetary interpretation for two signals. Before more data can be acquired we concluded that at least three planets are orbiting GJ 163. They have orbital periods of Pb = 8.632 ± 0.002, Pc = 25:63 ± 0:03, and Pd = 604 ± 8 days and minimum masses m sin i = 10.6 ± 0.6, 6.8 ± 0.9, and 29 ± 3 M, respectively. We hold our interpretations for the two additional signals with periods P(e) = 19:4 and P(f) = 108 days.
The inner pair presents an orbital period ratio of 2.97, but a dynamical analysis of the system shows that it lays outside the 3:1 mean motion resonance. The planet GJ 163c, in particular, is a super-Earth with an equilibrium temperature of Teq = (302 ± 10)(1 - A)¼ K and may lie in the so-called habitable zone for albedo values (A = 0.34-0.89) moderately higher than that of Earth (A = 0.2-0.3).

Notes
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).
Table 6 is available in electronic form at http://www.aanda.org
Radial-velocity time series (Table 6) are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A110

Astronomy and Astrophysics
Volume 556, Number of pages A110_1
2013 August

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Instituto de Astrof√≠sica e Ci√™ncias do Espa√ßo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia