I will discuss the implications of the recent detection of
gravitational waves emitted by a pair of merging neutron stars and their
electromagnetic counterpart, events GW170817 and GRB170817A,
on the viability of the doubly-coupled bimetric models of cosmic
evolution, where the two metrics couple directly to matter through a
composite, effective metric. I will show that the bounds
on the speed of gravitational waves place strong constraints on the
doubly-coupled models, forcing the two metrics to be proportional at the
background level or the models to become singly-coupled.
Proportional backgrounds are particularly interesting as they provide
stable cosmological solutions with phenomenologies equivalent to that of
LCDM at the background level as well as for linear perturbations, while
nonlinearities are expected to show deviations from the standard model.