Effects of QCD phase transition on gravitational radiation from two-dimensional collapse and bounce of massive stars

Abstract

We perform two-dimensional, magneto-hydrodynamical core-collapse simulations of massive stars accompanying the QCD phase transition. We study how the phase-transition affects the gravitational waveforms near the epoch of core-bounce. As for initial models, we change the strength of rotation and magnetic fields. Particularly, the degree of differential rotation in the iron core (Fe-core) is changed parametrically. As for the microphysics, we adopt a phenomenological equation of state above the saturation density, including two parameters to change the hardness before the transition. We assume the first order phase transition, where the conversion of bulk nuclear matter to a chirally symmetric quark-gluon phase is described by the MIT bag model. Based on these computations, we find that the phase transition can make the maximum amplitudes larger up to {approx}10 percents than the ones without the phase transition. On the other hand, when the degree of the differential rotation becomes larger, the maximum amplitudes become smaller up to {approx}10 percents owing to the phase transition. We find that even extremely strong magnetic fields {approx}10{sup 17} G in the protoneutron star do not affect these results.