We present new ( 3+1 ) D numerical relativity simulations of the binary neutron star ( BNS ) merger and postmerger phase .
We focus on a previously inaccessible region of the binary parameter space spanning the binary ’ s mass-ratio q \sim 1.00 - 1.75 for different total masses and equations of state , and up to q \sim 2 for a stiff BNS system .
We study the mass-ratio effect on the gravitational waves ( GWs ) and on the possible electromagnetic emission associated to dynamical mass ejecta .
We compute waveforms , spectra , and spectrograms of the GW strain including all the multipoles up to l = 4 .
The mass-ratio has a specific imprint on the GW multipoles in the late-inspiral-merger signal , and it affects qualitatively the spectra of the merger remnant .
The multipole effect is also studied by considering the dependency of the GW spectrograms on the source ’ s sky location .
Unequal mass BNSs produce more ejecta than equal mass systems with ejecta masses and kinetic energies depending almost linearly on q .
We estimate luminosity peaks and light curves of macronovae events associated to the mergers using a simple approach .
For q \sim 2 the luminosity peak is delayed for several days and can be up to four times larger than for the q = 1 cases .
The macronova emission associated with the q \sim 2 BNS is more persistent in time and could be observed for weeks instead of few days ( q = 1 ) in the near infrared .
Finally , we estimate the flux of possible radio flares produced by the interaction of relativistic outflows with the surrounding medium .
Also in this case a large q can significantly enhance the emission and delay the peak luminosity .
Overall , our results indicate that BNS merger with large mass ratio have EM signatures distinct from the equal mass case and more similar to black hole - neutron star binaries .