  Gravitational waves have been detected from the inspiral of a binary
neutron-star, GW170817, which allowed constraints to be placed on the neutron
star equation of state. The equation of state can be further constrained if
gravitational waves from a post-merger remnant are detected. Post-merger
waveforms are currently generated by numerical-relativity simulations, which
are computationally expensive. Here we introduce a hierarchical model trained
on numerical-relativity simulations, which can generate reliable post-merger
spectra in a fraction of a second. Our spectra have mean fitting factors of
0.95, which compares to fitting factors of 0.76 and 0.85 between different
numerical-relativity codes that simulate the same physical system. This method
is the first step towards generating large template banks of spectra for use in
post-merger detection and parameter estimation.
