Near-infrared integral-field spectroscopy of the companion to GQ Lupi*
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany e-mail: firstname.lastname@example.org
2 Astrophysikalisches Institut, Universität Jena, Schillergässchen 2-3, 07745 Jena, Germany
3 Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
Accepted: 7 December 2006
Context.The first substellar companion of possibly planetary mass around a normal star, GQ Lup, has been directly imaged (Neuhäuser et al. 2005, A&A, 435, L13). Besides the unknown formation history, the mass of such an object is a criterion to decide about its true nature.
Aims.We aim to determine the physical properties of the GQ Lup companion – effective temperate (Teff) and surface gravity (), and thus its mass independently from evolutionary models.
Methods.We use the adaptive optics integral-field spectrograph SINFONI at the VLT for near-infrared spectroscopy from 1.1 to 2.5 m with a resolution of –4000. We compare these spectra with synthetic atmospheric models (GAIA v2.0 cond).
Results.From the complete set of spectra we find a consistent effective temperature and surface gravity of and . Combined with a slightly revised luminosity of dex for the companion, we determine a radius of and thus a mass of ~. The uncertainty of this value is rather high. Due to the large uncertainty of the surface gravity, the mass could range from 4 to 155 . By comparing the paramaters of the companion of GQ Lup to the ones of 2MASS J05352184-0546085, published by Stassun et al. (2006, Nature, 440, 311), we conclude that the companion to GQ Lup A has a mass lower than .
Key words: stars: low-mass, brown dwarfs / planetary systems / techniques: spectroscopic
© ESO, 2007