  We present a self-consistent modelling of the available light curve and
radial velocity data of WASP-47 that takes into account the gravitational
interactions between all known bodies in the system. The joint analysis of
light curve and radial velocity data in a multi-planetary system allows
deriving absolute densities, radii, and masses without the use of theoretical
stellar models. For WASP-47 the precision is limited by the reduced dynamical
information that is due to the short time span of the K2 light curve. We
achieve a precision of around 22% for the radii of the star and the transiting
planets, between 40% and 60% for their masses, and between 1.5% and 38% for
their densities. All values agree with previously reported measurements. When
theoretical stellar models are included, the system parameters are determined
with a precision that exceeds that achieved by previous studies, thanks to the
self-consistent modelling of light curve and radial velocity data.
