2006A&A...459..955L

We present the results of multi epoch imaging observations of the companion to the planetary host Gliese 86. Associated with radial velocity measurements, this study aimed at dynamically characterizing with the orbital properties and the mass of this companion (hereafter Gliese 86 B), but also at investigating the possible history of this particular system. We used the adaptive optics instrument NACO at the ESO Very Large Telescope to obtain deep coronographic imaging to obtain new photometric and astrometric measurements of Gliese 86 B. Part of the orbit is resolved. The photometry of Gl 86 B indicates colors compatible with a ∼70 Jupiter mass brown dwarf or a white dwarf. Both types of objects fit the available, still limited astrometric data. If we attribute the long term radial velocity residual drift observed for Gl 86 A to B, then the mass of the latter object is ≃0.5M_☉. We analyse both astrometric and radial velocity data to propose first orbital parameters for Gl 86 B. Assuming Gl 86 B is a ≃0.5M_☉ white dwarf, we explore the constraints induced by this hypothesis and refine the parameters of the system.