A&A 496, 521-526 (2009)
DOI: 10.1051/0004-6361:200810774

The HARPS search for southern extra-solar planets

XVI. HD 45364, a pair of planets in a 3:2 mean motion resonance

A. C. M. Correia¹, S. Udry², M. Mayor², W. Benz³, J.-L. Bertaux⁴, F. Bouchy⁵, J. Laskar⁶, C. Lovis², C. Mordasini³, F. Pepe², and D. Queloz<sup>2

1</sup>  Departamento de Física, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
    e-mail: correia@ua.pt
²  Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
    e-mail: michel.mayor@obs.unige.ch
³  Physikalisches Institut, Universität Bern, Silderstrasse 5, 3012 Bern, Switzerland
⁴  Service d'Aéronomie du CNRS/IPSL, Université de Versailles Saint-Quentin, BP3, 91371 Verrières-le-Buisson, France
⁵  Institut d'Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France
⁶  IMCCE, CNRS-UMR8028, Observatoire de Paris, UPMC, 77 avenue Denfert-Rochereau, 75014 Paris, France

Received 8 August 2008 / Accepted 6 November 2008

Abstract
Precise radial-velocity measurements with the HARPS spectrograph reveal the presence of two planets orbiting the solar-type star HD 45364. The companion masses are M sin i = 0.187 and 0.658 , with semi-major axes of a = 0.681 AU and 0.897 AU, and eccentricities of e = 0.168 and 0.097, respectively. A dynamical analysis of the system further shows a 3:2 mean motion resonance between the two planets, which prevents close encounters and ensures the stability of the system over 5 Gyr. This is the first time that such a resonant configuration has been observed for extra-solar planets, although there is an analogue in our Solar System formed by Neptune and Pluto. This singular planetary system may provide important constraints on planetary formation and migration scenarios.

Key words: stars: individual: HD 45364 -- stars: planetary systems -- techniques: radial velocities -- methods: observational

© ESO 2009

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