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-year 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 Jupiter mass 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.

Highlights

  • Brown dwarfs (BD) are substellar objects in the mass range of approximately 13–80 Jupiter masses; they have enough mass to burn deuterium, but are too light to permit hydrogen burning in their inner cores (Burrows et al 1997; Chabrier & Baraffe 2000; Spiegel et al 2011)

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

  • Following the approach described by Díaz et al (2012), we examined the bisector span of the SOPHIE cross-correlation function (CCF) of our BD candidates to check whether significant variation and a correlation with radial velocity (RV) measurements can reveal a relatively luminous

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Summary

VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

F. Bouchy1,2, D. Ségransan2, R. F. Díaz1,2, T. Forveille3, I. Boisse1,4, L. Arnold5, N. Astudillo-Defru3, J.-L. Beuzit3, X. Bonfils3, S. Borgniet3, V. Bourrier2,6, B. Courcol1, X. Delfosse3, O. Demangeon1, P. Delorme3, D. Ehrenreich2, G. Hébrard5,6, A.-M. Lagrange3, M. Mayor2, G. Montagnier5,6, C. Moutou1,7, D. Naef2, F. Pepe2, C. Perrier3, D. Queloz2, J. Rey2, J. Sahlmann8, A. Santerne4, N. C. Santos4,9, J.-P. Sivan1, S. Udry2, and P. A. Wilson6

Introduction
Spectroscopic observations
Stellar characteristics
Radial velocity analysis and orbital solutions
Diagnostic for resolving the nature of the companions
HIPPARCOS astrometry
Bisector span analysis
Search for a second component in the CCF
High-resolution imaging with PUEO
HD 10844
HD 14348
HD 18757
HD 72946
HD 209262
Findings
Discussion and conclusion
Full Text
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