Gravitational wave emission during the transition to strange stars

We present a series of axisymmetric, magneto-hydrodynamical simulations for the rotational core collapse of a massive star accompanying the QCD phase transition. To elucidate the implications of a phase transition against a supernova, we investigate the waveforms of gravitational wave derived from the quadrupole formula that includes the contributions from the electromagnetic fields. We adopt a phenomenological equation of state above the nuclear matter density ρ₀ that includes two parameters to change the hardness of the matter before the transition. We assume that the first order phase transition is the conversion of bulk nuclear matter to a chirally symmetric quark-gluon phase described by the MIT bag model. In most models with the phase transition, the first peak amplitudes are higher by a few percents to nearly ten percents than those without the transition. However, it is found that under the condition of the very strong differential rotation, the height of the peak becomes lower by several percents if the phase transition is included. In the paper, we show the typical models of our calculations.