Adaptive Hough transform for the search of periodic sources

Real data produced by gravitational wave detectors are affected by nonstationarities which must be properly weighted in order to reduce their effect. In the incoherent step of the hierarchical method for the periodic sources search, based on the Hough transform, two kinds of non-stationarities must be taken into account: one connected to non-stationary disturbances and another, with a period of one sidereal day, due to the rotation of the Earth, which changes the orientation of the detector and therefore the signal amplitude. In this paper, we describe the adaptive Hough transform in which these two issues are suitably treated. We discuss its statistical properties and some implementative details.