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Issue A&A
Volume 430, Number 3, February II 2005
Page(s) 1027 - 1033
Section Stellar structure and evolution
DOI 10.1051/0004-6361:20041353



A&A 430, 1027-1033 (2005)
DOI: 10.1051/0004-6361:20041353

Astrometric and spectroscopic confirmation of a brown dwarf companion to GSC 08047-00232

VLT/NACO deep imaging and spectroscopic observations
G. Chauvin1, A.-M. Lagrange2, F. Lacombe3, C. Dumas1, D. Mouillet4, B. Zuckerman5, E. Gendron2, I. Song5, J.-L. Beuzit1, P. Lowrance6 and T. Fusco7

1  European Southern Observatory, Casilla 19001, Santiago 19, Chile
    e-mail: gchauvin@eso.org
2  Laboratoire d'Astrophysique, Observatoire de Grenoble, 414 rue de la piscine, 38400 Saint-Martin d'Hères, France
3  Laboratoire D'Études Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, Bât. 16, 5 Place J. Jansen, 92195 Meudon, France
4  Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 57 avenue d'Azereix, BP 826, 65008 Tarbes, France
5  Department of Physics & Astronomy and Center for Astrobiology, Physics & Astronomy Building, UCLA, Los Angeles, CA 90095-1562, USA
6  SIRTF Science Center Infrared Processing and Analysis Center, MS 220-6, Pasadena, CA 91125, USA
7  ONERA, BP 52, 29 avenue de la Division Leclerc, 92320 Châtillon Cedex, France

(Received 25 May 2004 / Accepted 16 September 2004 )

Abstract
We report VLT/NACO imaging observations of the stars GSC 08047-00232 and HIP 6856, probable members of the large Tucana-Horologium association. During our previous ADONIS/SHARPII deep imaging survey, a substellar candidate companion was discovered around each star. Based on VLT/NACO astrometric measurements, we find that GSC 08047-00232 and the faint candidate companion near to it share the same proper motion with a significance of 3.1 $\sigma$. On the contrary, the candidate companion to HIP 6856 is probably a background object with a significance of 4.3 $\sigma$. We also detect a new fainter and closer candidate companion to HIP 6856, but which is likely a background object too with a significance of 4 $\sigma$. Recent VLT/NACO spectroscopic measurements of GSC 08047-00232 finally confirm the substellar nature of this young brown dwarf with a derived spectral type M $9.5\pm1$. GSC 08047-00232 B, with an estimated mass of $25\pm10~M_{\rm {Jup}}$ and an effective temperature of $2100\pm200$ K, is presently the third substellar companion identified among young, nearby associations.


Key words: instrumentation: adaptive optics -- stars: low-mass, brown dwarfs

SIMBAD Objects



© ESO 2005


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