GWDAW-8 Abstract: Spectral filtering for hierarchical search of periodic sources

Sergio Frasca · U. La Sapienza · Virgo

The Rome hierarchical search for periodic sources starts with an incoherent step (an Hough transform) based on a time-frequency peak map, that is built starting from a short FFT data base containing FFTs of the data with duration between about 1000 s to 16000 s. The frequency resolution is, in this case, low enough to neglect the sidereal time frequency and amplitude modulation. At the second step of the hierarchical procedure, the time base of the FFTs is increased and so the frequency resolution; in this case the above simplification cannot be done and the sidereal modulation spreads the signal on different bins. In order to not loose the signal to noise ratio, we have to collect the spread power in the spectrum with matched filtering. We studied the set of filters to apply, depending on the source location and polarization. This increases the computational burdeen of the second step, so we studied a different policy of applying the hierarchical search. With this policy only the coincident candidates of different observation periods are followed up with the second step.