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The French-Italian interferometric gravitational wave detector VIRGO is currently being commissioned. Its principal instrument is a Michelson interferometer with 3 km long optical cavities in the arms and a power-recycling mirror. This paper gives an overview of the present status of the system. We report on the presently attained sensitivity and the(More)
A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of(More)
The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence(More)
In the hierarchical search for periodic sources of gravitational waves, the candidate selection, in the incoherent step, can be performed with Hough transform procedures. In this paper we analyze the problem of sensitivity loss due to discretization of the parameters space vs computing cost, comparing the properties of the sky Hough procedure with those of(More)
We derive new upper limits on the ellipticity of pul-sars whose braking index has been measured, more tightening than those usually given, assuming that both a gravitational torque and an electromagnetic one act on them. We show that the measured braking indexes of pulsars are recovered in this model. We consider the electromagnetic torque both constant and(More)
Real data produced by gravitational wave detectors are affected by non-stationarities 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(More)
We study, via a Monte Carlo simulation, a population of isolated asymmetric neutron stars where the magnitude of the magnetic field is low enough so that the dynamical evolution is dominated by the emission of gravitational waves. A starting population, with age uniformly distributed back to 100 Myr (or 500 Myr) and endowed with a birth kick velocity, is(More)
The Amaldi 10 Parallel Session C2 on gravitational wave(GW) search results, data analysis and parameter estimation included three lively sessions of lectures by 13 presenters, and 34 posters. The talks and posters covered a huge range 123 11 Page 2 of 26 P. Astone et al. of material, including results and analysis techniques for ground-based GW detectors ,(More)