New constrains on Gliese 86 B ⋆

Aims. We present the results of multi epochs imaging observations of the companion to the planetary host Gliese 86. Associated to radial velocity measurements, this study aimed at characterizing dynamically the orbital properties and the mass of this companion (here after Gliese 86 B), but also at investigating the possible history of this particular system. Methods. We used the adaptive optics instrument NACO at the ESO Very Large Telescope to obtain deep coronographic imaging in order to determine new photometric and astrometric measurements of Gliese 86 B. Results. 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 allow to fit the available, still limited astrometric data. Besides, 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 ≃ 0.5 M ⊙. We analyse both astrometric and radial velocity data to propose first orbital parameters for Gl 86 B. Assuming Gl 86 B is a ≃ 0.5 M ⊙ white dwarf, we explore the constraints induced by this hypothesis and refine the parameters of the system.