EDP Sciences
Free access
Volume 435, Number 1, May III 2005
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200500104

A&A 435, L13-L16 (2005)
DOI: 10.1051/0004-6361:200500104


Evidence for a co-moving sub-stellar companion of GQ Lup

R. Neuhäuser1, E. W. Guenther2, G. Wuchterl1, M. Mugrauer1, A. Bedalov1 and P. H. Hauschildt3

1  Astrophysikalisches Institut, Universität Jena, Schillergäßchen 2-3, 07745 Jena, Germany
    e-mail: rne@astro.uni-jena.de
2  Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
3  Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

(Received 6 October 2004 / Accepted 27 March 2005)

We present a companion of the $\le$2 Myr young classical T Tauri star GQ Lup in the Lupus star forming region at $140 \pm 50$ pc from imaging, astrometry, and spectroscopy. With direct K-band imaging using VLT/NACO, we detected an object 6 mag fainter than GQ Lup located $0.7^{\prime \prime}$ west of it. Compared to images obtained 2 to 5 years earlier with Subaru/CIAO and HST/PC, this object shares the proper motion of GQ Lup by 5 and $7\sigma$, respectively, hence it is a co-moving companion. Its K-L' color is consistent with a spectral type early to mid L. Our NACO K-band spectrum yields spectral type M9-L4 with H2O and CO absorption, consistent with the new GAIA-Dusty template spectrum for $\log~g \simeq 2$ to 3 and $T_{\rm eff} \simeq 2000$ K with ~2  $R_{\rm jup}$ radius at $\sim $140 pc, hence few Jupiter masses. Using the theoretical models from Wuchterl & Tscharnuter (2003), Burrows et al. (1997), and Baraffe et al. (2002), the mass lies between 1 and 42 Jupiter masses.

Key words: low-mass stars -- substellar companions -- brown dwarfs -- extra-solar planets -- GQ Lup

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