Excitation of Schwarzschild quasinormal modes by collapse

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Abstract
The quasinormal ringing of a black hole is of considerable interest in connection with laser interferometric gravitational-wave detectors. Although considerable work has been directed towards computing quasinormal frequencies, little attention has been paid to what features of an astrophysical process excite ringing. We investigate this question here, first with model collapse problems which give closed-form expressions for ringing strength, and second with computer studies of a range of collapse-type processes. We arrive at a simple semiempirical rule for excitation, which should produce adequate estimates of ringing strength when used in connection with Newtonian modelin of the early stages of collapse.