Dynamical excitation of space-time modes of compact objects

We discuss, in the perturbative regime, the scattering of Gaussian pulses of odd-parity gravitational radiation off a nonrotating relativistic star and a Schwarzschild black hole. We focus on the excitation of the w-modes of the star as a function of the width b of the pulse and we contrast it with the outcome of a Schwarzschild black hole of the same mass. For sufficiently narrow values of b, the waveforms are dominated by characteristic space-time modes. On the other hand, for sufficiently large values of b the backscattered signal is dominated by the tail of the Regge-Wheeler potential, the quasinormal modes are not excited and the nature of the central object cannot be established. We view this work as a useful contribution to the comparison between perturbative results and forthcoming w-mode 3D-nonlinear numerical simulation.