On the maximum mass of differentially rotating compact stars

Hot compact stars (neutron stars or strange stars), born in a supernova explosion or being the remnant of neutron star mergers in the binary systems are expected to rotate differentially. Differential rotation may temporally stabilise a massive rotating star against prompt collapse to a black hole. The maximum mass is a crucial parameter being a boundary between stable compact stars and black holes. We summarise our results on the maximum mass of the differentially rotating Strange Quark Stars (SQS) and Neutron Stars (NS) described by a polytropic Equation of State (EOS). Using highly accurate, relativistic multidomain pseudo-spectral code we performed calculations of differentially rotating compact stars for broad ranges of the degree of differential rotation and maximum density. We show that the resulted maximum mass depends on both the degree of differential rotation and the type of solution for all considered EOS. When the differential rotation is taken into account, the maximum allowed mass of NS or SQS can be even 3-4 times higher than the maximum mass of nonrotating configurations. Such result is obtained for moderate or low degree of differential rotation for NS and SQS respectively. We find the universal relation between the maximum mass of a compact star and the degree of differential rotation. These results could have important consequences for gravitational wave astronomy.