A. Viceré

The Virgo interferometer

The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa to be commissioned in the year 2000. Virgo has been designed to achieve a strain sensitivity of a few times at 200 Hz. A large effort has gone into the conception of the mirror suspension system, which is expected to reduce noise to the level of at 10 Hz. The expected signals and main sources of noise are briefly discussed; the choices made are illustrated together with the present status of the experiment.

Coherent Bayesian analysis of inspiral signals

In this paper we present a Bayesian parameter estimation method for the analysis of interferometric gravitational wave observations of an inspiral of binary compact objects using data recorded simultaneously by a network of several interferometers at different sites. We consider neutron star or black hole inspirals that are modeled to 3.5 post-Newtonian (PN) order in phase and 2.5 PN in amplitude. Inference is facilitated using Markov chain Monte Carlo (MCMC) methods that are adapted in order to efficiently explore the particular parameter space. Examples are shown to illustrate how and what information about the different parameters can be derived from the data. This study uses simulated signals and data with noise characteristics that are assumed to be defined by the LIGO and Virgo detectors operating at their design sensitivities. Nine parameters are estimated, including those associated with the binary system plus its location on the sky. We explain how this technique will be part of a detection pipeline for binary systems of compact objects with masses up to , including cases where the ratio of the individual masses can be extreme.

The VIRGO experiment

The status of the VIRGO experiment, as of summer 2000 is presented: we report on the progress in the construction and the next steps are briefly illustrated.

Optical detector topology for third-generation gravitational wave observatories

The third generation of gravitational wave observatories, with the aim of providing 100 times better sensitivity than currently operating interferometers, is expected to establish the evolving field of gravitational wave astronomy. A key element, required to achieve this ambitious sensitivity goal, is the exploration of new interferometer geometries, topologies and configurations. In this article we review the current status of the ongoing design work for third-generation gravitational wave observatories. The main focus is the evaluation of the detector geometry and detector topology. In addition we discuss some promising detector configurations and potential noise reduction schemes.

An autocorrelation method to detect periodic gravitational waves from neutron stars in binary systems

Rotating, non-axisymmetric neutron stars are expected to emit continuous gravitational waves at a nearly stable frequency. Nowadays about 2500 pulsars have been detected, thanks to their beamed electromagnetic emission, and many more of these objects should exist, whose electromagnetic beam does not include Earth and cannot be detected. The gravitational emission is not beamed, and could be accessible to gravitational observatories, even though no detection as been claimed yet. About half of the pulsars predicted to possibly emit gravitational waves in the frequency range accessible to ground-based interferometers belongs to binary systems; this is an additional complication, because the frequencies of these pulsars are Doppler-shifted due to their orbital motion, and an optimal detection strategy would require a computing power far beyond the present capabilities. We present here an approach which allows searching all-sky for such sources, over a broad range of frequencies, orbital periods and binary system eccentricities, reaching sensitivities potentially good enough to provide candidates for more sophisticated hierarchical detection methods. We test this new technique using real data taken during the first science run of Virgo, and estimating the sensitivity to a set of simulated pulsar signals.

Benefits of joint LIGO-Virgo coincidence searches for burst and inspiral signals

We examine the benefits of performing a joint LIGO-Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal.We examine the benefits of performing a joint LIGO--Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal.