  The gravitational microlensing technique allows the discovery of exoplanets
around stars distributed in the disk of the galaxy towards the bulge. However,
the alignment of two stars that led to the discovery is unique over the
timescale of a human life and cannot be re-observed. Moreover, the target host
is often very faint and located in a crowded region. These difficulties hamper
and often make impossible the follow-up of the target and study of its possible
companions. Gould et al. (2013) predicted the radial-velocity curve of a binary
system, OGLE-2011-BLG-0417, discovered and characterised from a microlensing
event by Shin et al. (2012). We used the UVES spectrograph mounted at the VLT,
ESO to derive precise radial-velocity measurements of OGLE-2011-BLG-0417. To
gather high-precision on faint targets of microlensing events, we proposed to
use the source star as a reference to measure the lens radial velocities. We
obtained ten radial velocities on the putative V=18 lens with a dispersion of
~100 m/s, spread over one year. Our measurements do not confirm the
microlensing prediction for this binary system. The most likely scenario is
that the assumed V=18 mag lens is actually a blend and not the primary lens
that is 2 magnitude fainter. Further observations and analyses are needed to
understand the microlensing observation and infer on the nature and
characteristics of the lens itself.
