Pawel Szewczyk (PhD candidate, OAUW)
Are hypermassive neutron stars dynamically stable?
Neutron stars (NS) formed by collapse of a massive stellar core or in binary NS mergers are known to begin their lives with a strongly differential rotation. Even though the rotation becomes uniform on long timescales, the differential rotation may play an important role in the initial phase of the NS life. In particular, differentially rotating NS can be much more massive than rigidly rotating NS. NS with such large masses are called hypermassive. However, these objects are not always dynamically stable. Some of them may undergo a prompt collapse to a black hole. By performing a series of numerical simulations, we inspect the limit of stability against quasi-radial perturbations for a wide range of parameters of differentially rotating NS. We also study the stability against non-axisymmetrical perturbations for selected models. I will present the results of our study of NS stability and discuss their impact on observational prospects of core-collapse supernovae and binary NS mergers.