RESEARCH
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The SOPHIE search for northern extrasolar planets. VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

F. Bouchy, D. SÚgransan, R. F. DÝaz, T. Forveille, I. Boisse, L. Arnold, N. Astudillo-Defru, J.-L. Beuzit, X. Bonfils, S. Borgniet, V. Bourrier, B. Courcol, X. Delfosse, O. Demangeon, P. Delorme, D. Ehrenreich, G. HÚbrard, A.-M. Lagrange, M. Mayor, G. Montagnier, C. Moutou, D. Naef, F. Pepe, C. Perrier, D. Queloz, J. Rey, J. Sahlmann, A. Santerne, N. C. Santos, J.-P. Sivan, S. Udry, P. A. Wilson

Abstract
Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-yr radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 MJup orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging.

Keywords
techniques: radial velocities, binaries: spectroscopic, stars: low-mass, brown dwarfs, stars: general

Notes
Based on observations made with ELODIE and SOPHIE spectrographs on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/AMU), France.

Tables 5-9 (RV data) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A46

Astronomy and Astrophysics
Volume 585, Article Number A46, Number of pages 8
2016 January

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Instituto de Astrof├şsica e Ci├¬ncias do Espa├žo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Funda├ž├úo para a Ci├¬ncia e a Tecnologia
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