Binary neutron star merger lead to the formation of a
massive, rapidly and differentially rotating neutron star (or a
strange star) or to the prompt collapse to a black hole. The maximum
mass of a differentially rotating remnant is crucial for distinguishing
between these two final objects. We study the effect of differential
rotation on the maximum mass of neutron stars (strange stars). We
numerically construct stellar models using a highly accurate
relativistic code based on a multi-domain spectral method. We find
much larger mass increases for strange stars than for neutron stars
for the same degree of differential rotation.