Radial oscillations and gravitational wave echoes of strange stars for various equations of state

We study the radial oscillations of non-rotating strange stars (SSs) and their characteristic echo frequencies for three equations of state (EoS), viz., MIT Bag model EoS, linear EoS, and polytropic EoS. The frequencies of radial oscillations of these compact stars are computed for these EoSs. In total, 22 lowest radial frequencies for each of these three EoSs have been computed. First, for each EoS, we have integrated Tolman-Oppenheimer-Volkoff equations numerically to calculate the radial and pressure perturbations of SSs. Next, the mass-radius relationships for these stars are obtained using these three EoSs. Then the radial frequencies of oscillations for these EoSs are calculated. Further, the characteristic gravitational wave echo frequencies and the repetition of echo frequencies of SSs are computed for these EoSs. Our numerical results show that the radial frequencies and also echo frequencies vastly depend on the model and on the value of the model parameter. Our results also show that the radial frequencies of strange stars are maximum for polytropic EoS in comparison to MIT Bag model EoS and linear EoS. Moreover, SSs with MIT Bag model EoS and linear EoS are found to emit gravitational wave echoes. Whereas, SSs with polytropic EoS are not emitting gravitational wave echoes.

Automated summary

The study investigated the radial oscillations and echo frequencies of strange stars under different equations of state, showing that the radial frequencies and echo frequencies of strange stars significantly depend on the model and parameter values. Additionally, it was found that strange stars with polytropic equation of state exhibit the highest radial frequencies compared to MIT Bag model equation of state and linear equation of state, and strange stars with MIT Bag model equation of state and linear equation of state emit gravitational wave echoes while those with polytropic equation of state do not.