The short FFT database and the peak map for the hierarchical search of periodic sources

In the hierarchical search for periodic sources the construction of the short FFT database (SFDB) plays a key role for the next steps of the search, in terms of easy and fast access to the needed information and of data quality. The last information is crucial when combining data over long time periods, given the presence of non-stationarities in the noise. We will outline here the procedure we use to construct the SFDB and in particular the peak map, which is the first step of the hierarchical procedure, describing the tools we use to remove disturbances, which would enhance the noise floor. We will also describe the data and information we evaluate and store to characterize each FFT Particular emphasis is given to the procedure used to construct the estimator of the average noise spectral density, which is needed for good detection efficiency in the identification of peaks. We will give some examples, using non-stationary data of the resonant detector Nautilus and simulated signals added to the noise.