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Issue A&A
Volume 370, Number 1, April IV 2001
Page(s) L1 - L4
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20010298



A&A 370, L1-L4 (2001)
DOI: 10.1051/0004-6361:20010298

A second substellar companion in the Gliese 86 system

A brown dwarf in an extrasolar planetary system
S. G. Els1, 2, M. F. Sterzik3, F. Marchis4, E. Pantin5, M. Endl6 and M. Kürster3

1  Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
2  Universität Heidelberg, Institut für Theoretische Astrophysik, Tiergartenstr. 15, 69121 Heidelberg, Germany
3  European Southern Observatory, Casilla 19001, Santiago 19, Chile
4  University of California Berkeley/Center for Adaptive Optics, 601 Campbell Hall, Berkeley, CA 94720, USA
5  DSM/DANIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette, France
6  Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria

(Received 1 February 2001 / Accepted 22 February 2001 )

Abstract
We report observations using the ESO adaptive optics system ADONIS of the known extrasolar planetary system Gliese 86. This star has a known $4 {M}_{\mathrm{Jup}} \sin i$ planet in a 15.8 day orbit and exhibits an additional, large, long-period, radial velocity drift (2000). The coronographic images reveal a faint ( J=14.7, H=14.4, K=13.7) object at a projected distance of $r=1{.^{\prime\prime}}72 \pm 0{.^{\prime\prime}}02$ and ${\rm PA}=119\pm 1 ^\circ$. Gliese 86 and the discovered object share the same proper motion, as confirmed by independent measurements at three different epochs indicating that this system is gravitationally bound. From the infrared colors and magnitudes we infer an approximate spectral type for Gliese 86B at the transition from L to T dwarfs, also called "early T dwarf"assuming the classification by Leggett et al. (2000). Although present brown dwarf evolutionary models do not cover the mass and age range probed by this objects, an upper limit of the mass of about ${{M}}_{\mathrm{GJ86B}} \le 70 {M}_{\mathrm{Jup}}$ can be inferred from the models by Baraffe et al. (1998). Dusty model atmospheres appear not to be compatible with the IR colors.


Key words: stars: individual: Gliese 86 -- stars: brown dwarfs -- planetary systems

Offprint request: S. G. Els, sels@kso.tls-tautenburg.de

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© ESO 2001


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