  We study the radial oscillations of non-rotating strange stars and their
characteristic echo frequencies for three Equations of state (EoSs), viz., MIT
Bag model EoS, linear EoS and polytropic EoS. The frequencies of radial
oscillations of these compact stars are computed for these EoSs. 22 lowest
radial frequencies for each of these three EoSs have been computed. First, for
each EoS, we have integrated Tolman-Oppenheimer-Volkoff (TOV) equations
numerically to calculate the radial and pressure perturbations of strange
stars. 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 strange stars 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,
strange stars with MIT Bag model EoS and linear EoS are found to emit
gravitational wave echoes. Whereas, strange stars with polytropic EoS are not
emitting gravitational wave echoes.
