  Of all the astronomical sources of gravitational radiation, the ringdown
waveform arising from a small perturbation of a spinning black hole is perhaps
the best understood: for the late stages of such a perturbation, the waveform
is simply an exponentially-damped sinusoid. Searching interferometric
gravitational wave antenna data for these should be relatively easy. In this
paper, I present the results of a single-filter search for ringdown waveforms
arising from a 50 solar mass black hole with 98% of its maximum spin angular
momentum using data from the Caltech 40-meter prototype interferometer. This
search illustrates the techniques that may be used in analyzing data from
future kilometer-scale interferometers and describes some of the difficulties
present in the analysis of interferometer data. Most importantly, it
illustrates the use of coincident events in the output of two independent
interferometers (here simulated by 40-meter data at two different times) to
substantially reduce the spurious event rate. Such coincidences will be
essential tools in future gravitational wave searches in kilometer-scale
interferometers.
