We compute the tidal deformabilities for neutron star merger for equations of state with a strong first order phase transition producing a new separate branch in the mass-radius diagram .
A case is found where all three possible pairs of combinations between these two neutron star branches are present for the total mass of M = 2.7 M _ { \odot } of the observed merger event GW170817 .
It is demonstrated that the plot of the two tidal deformabilities \Lambda _ { 1 } and \Lambda _ { 2 } of the binary neutron star can show up to three separate branches .
We propose that the future detections of neutron star merger events with the same value for \Lambda _ { 1 } but different values of \Lambda _ { 2 } serve as a signal for the existence of a strong first order phase transition in neutron star matter .