We discuss the detection of burst events in wide band GW detectors, like the LIGO or Virgo instruments. These events are anticipated as resulting from the collapse of the core in massive stars, but the resulting waveforms suffer from large theoretical uncertainties. We propose an analysis method which is proven to be optimal under the two assumptions of gaussian noise and unknown waveform, and we discuss its statistic properties. The method can be extended to the network case, that is it allows to combine coherently the information from several detectors. The sensitivity of Virgo, LIGO and networks of several detectors are estimated and the prospect for the detection of galactic events are discussed.