  The multi-messenger detection of the gravitational-wave signal GW170817, the
corresponding kilonova AT2017gfo and the short gamma-ray burst GRB170817A, as
well as the observed afterglow has delivered a scientific breakthrough. For an
accurate interpretation of all these different messengers, one requires robust
theoretical models that describe the emitted gravitational-wave, the
electromagnetic emission, and dense matter reliably. In addition, one needs
efficient and accurate computational tools to ensure a correct
cross-correlation between the models and the observational data. For this
purpose, we have developed the Nuclear-physics and Multi-Messenger Astrophysics
framework NMMA. The code allows incorporation of nuclear-physics constraints at
low densities as well as X-ray and radio observations of isolated neutron
stars. In previous works, the NMMA code has allowed us to constrain the
equation of state of supranuclear dense matter, to measure the Hubble constant,
and to compare dense-matter physics probed in neutron-star mergers and in
heavy-ion collisions, and to classify electromagnetic observations and perform
model selection. Here, we show an extension of the NMMA code as a first attempt
of analyzing the gravitational-wave signal, the kilonova, and the gamma-ray
burst afterglow simultaneously. Incorporating all available information, we
estimate the radius of a $1.4M_\odot$ neutron star to be
$R=11.98^{+0.35}_{-0.40}$km.
