The quadrupole oscillations of strange-quark stars

We study the relativistic quadrupole oscillations (l = 2) of strange-quark stars by calculating their quasi-normal modes, and we thus explore the poss ibility of using these oscillation frequencies and damping times to differe ntiate among relativistic polytropic stars, neutron stars, pure light-quark stars, and hybrid neutron stars with quark cores. We found that, whereas t he general features of the w-mode spectra of quark stars and hybrid neutron stars are very similar to those of relativistic polytropes, they differ in the higher mode frequencies for both axial and polar oscillations. The pro files off-modes for quark stars are different from those of realistic neutr on stars, and from that we conclude that quark and strange-quark stars are more efficient gravitational-waves radiators than pure neutron stars. Also, the damping times of various modes are rather sensitive to the details of the quark model, such as the Bag constant, quark-gluon interactions, and qu ark mass corrections.