A short-period super-Earth orbiting the M2.5 dwarf GJ 3634^⋆,⋆⋆

Detection with HARPS velocimetry and transit search with Spitzer photometry

¹ UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
e-mail: Xavier.Bonfils@obs.ujf-grenoble.fr
² Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
³ Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bât. B5C, 4000 Liège, Belgium
⁴ Planetary Systems Branch, Code 693, NASA/Goddard Space Flight Center Greenbelt, MD 20771, USA
⁵ Department of Earth, Atmospheric and Planetary Sciences, Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
⁶ Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁷ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Portugal

Received: 22 October 2010
Accepted: 19 January 2011

Abstract

We report on the detection of GJ 3634b, a super-Earth of mass $\mathit{m}\sin \mathit{i}\mathrm{=}\mathrm{7.}{\mathrm{0}}_{-0.8}^{\mathrm{+}\mathrm{0.9}} {\mathit{M}}_{\mathrm{\oplus }}$ and period P = 2.64561 ± 0.00066 day. Its host star is a M2.5 dwarf, has a mass of 0.45 ± 0.05   M_⊙, a radius of 0.43 ± 0.03   R_⊙ and lies 19.8 ± 0.6 pc away from our Sun. The planet is detected after a radial-velocity campaign using the ESO/Harps spectrograph. GJ 3634b had an a priori geometric probability to undergo transit of  ~7% and, if telluric in composition, a non-grazing transit would produce a photometric dip of  ≲0.1%. We therefore followed-up upon the RV detection with photometric observations using the 4.5-μm band of the IRAC imager onboard Spitzer. Our six-hour long light curve excludes that a transit occurs for 2σ of the probable transit window, decreasing the probability that GJ 3634b undergoes transit to  ~0.5%.