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SELECTED PAPERS FROM THE 6TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES, OKINAWA, JAPAN, 20-24 JUNE 2005, International audience, The C5 Virgo commissioning run, completed in December 2004, provided data suitable both in quantity and quality for extended analysis. We report here on-going work by the Virgo collaboration on data description, using tools developed either for gravitational wave burst event detection or data characterization. This snapshot illustrates the variety of approaches explored by the Virgo collaboration and indicates some avenues for future investigations.

GWDAW-9 proceedings - LIGO/VIRGO Working group Présenté par F. Beauville, This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.

GWDAW9 proceedings - LIGO/VIRGO Working group, We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.

International audience

International audience

12 pages - 04 VIRGO, International audience, 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 system's performance during the recent commissioning runs. After a sequence of intermediate stages, the interferometer is now being used in the so-called recombined configuration. The input laser beam is spatially filtered by a 144 m long input mode-cleaner before being injected to the main interferometer. The main optics are suspended from so-called \sa s, which provide an excellent seismic isolation. The two 3 km long Fabry-Perot arm cavities are kept in resonance with the laser light, and the Michelson interferometer is held on the dark fringe. An automatic mirror alignment system based on the Anderson technique has been implemented for the arm cavities. The light leaving the dark port contains the gravitational wave signal; this light is filtered by an output mode-cleaner before being detected by a photo detector. This setup is the last step on the way to the final configuration, which will include power recycling.

International audience, Virgo is a French–Italian collaboration for the construction and operation of a 3 km long interferometric gravitational wave antenna. The construction of the detector is already completed and the commissioning is quite advanced, while the data taking is expected to start in 2005. In this paper, we report on the present status of Virgo and on the results of commissioning activity. In particular, we analyse the first four engineering runs (C1–C4) and discuss the sensitivity obtained in C4.

International audience, We propose a new method for the detection of spectral lines in random noise. It mimics the processing scheme of matching filtering, i.e., a whitening procedure combined with the measurement of the correlation between the data and a template. Thanks to the original noise spectrum estimate used in the whitening procedure, the algorithm can easily be tuned to various types of noise. It can thus be applied to the data taken from a wide class of sensors. This versatility and its small computational cost make this method particularly well suited for real-time monitoring in gravitational wave experiments. We show the results of its application to Virgo C4 commissioning data.

International audience, We present the noise analysis package library (NAP), a new tool to perform noise studies and data conditioning on the data produced by gravitational wave detectors. We describe its design and report the results of the application of parametric spectral estimation, whitening, line removal with adaptive notch filters and noise removal using a multicoherence procedure on the data taken by the Virgo interferometer during the C5 engineering run.

International audience, During the commissioning of the Virgo interferometer, a search for environmental noise contributions to the dark fringe signal was undertaken. Dedicated tests have been performed to identify major sources of disturbances and to understand the coupling mechanism with the interferometer. The major effect is due to seismic/acoustic noise coupling to the laser beam before the input mode cleaner, then propagating as beam power noise to the ITF dark fringe output signal. In this paper we illustrate the tests performed and preliminary results of our investigation.

We report on an investigation of Virgo Commissioning run 4 data, dedicated to searching signals of the kind supposed to be emitted by inspiral neutron star binary systems. Given the still relatively limited sensitivity, the goal was to test some of the elements of the analysis chain, using simulated events, hardware and software injected in the data; the test allowed us to also characterize the detector stability during the run, for the purposes of the inspiral event search.

GWDAW-9 proceedings - LIGO/VIRGO Working group Présenté par F. Beauville, This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.

GWDAW9 proceedings - LIGO/VIRGO Working group, We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.

International audience, During the commissioning of the Virgo interferometer, a search for environmental noise contributions to the dark fringe signal was undertaken. Dedicated tests have been performed to identify major sources of disturbances and to understand the coupling mechanism with the interferometer. The major effect is due to seismic/acoustic noise coupling to the laser beam before the input mode cleaner, then propagating as beam power noise to the ITF dark fringe output signal. In this paper we illustrate the tests performed and preliminary results of our investigation.

SELECTED PAPERS FROM THE 6TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES, OKINAWA, JAPAN, 20-24 JUNE 2005, International audience, We present the status of the Virgo analysis pipeline dedicated to the search for coalescing binary signals, focusing on methods based on prior knowledge of the signal waveform. The pipeline includes two partially independent search methods: the multi-band template analysis (MBTA), which is original of Virgo and exploits the chirping behaviour of the signal, and a distributed implementation of the classical matched filter procedure (Merlino), based on robust MPI code. We discuss the application of the search methods to the analysis of data acquired during the Virgo commissioning run C5, which allowed us to perform tests and partially validate the methods and code.

International audience, We report on the status of the Virgo detector, under commissioning. We will focus on the last year's activity. The two commissioning runs performed during 2005 allowed us to reach a sensitivity of h ~ 6 × 10-22. The data obtained during the runs were used to test a few data analysis algorithms, namely coalescing binaries and burst searches. The main improvements made on the detector during this year will be described, as well as the plans and activities foreseen in the coming years

SELECTED PAPERS FROM THE 6TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES, OKINAWA, JAPAN, 20-24 JUNE 2005, Virgo is a power recycled Michelson interferometer, with 3 km long Fabry–Perot cavities in the arms. The locking of the interferometer has been obtained with an original lock acquisition technique. The main idea is to lock the instrument away from its working point. Lock is obtained by misaligning the power recycling mirror and detuning the Michelson from the dark fringe. In this way, a good fraction of light escapes through the antisymmetric port and the power build-up inside the recycling cavity is extremely low. The benefit is that all the degrees of freedom are controlled when they are almost decoupled, and the linewidth of the recycling cavity is large. The interferometer is then adiabatically brought on to the dark fringe. This technique is referred to as variable finesse, since the recycling cavity is considered as a variable finesse Fabry–Perot. This technique has been widely tested and allows us to reach the dark fringe in few minutes, in an essentially deterministic way.

International audience, Virgo is a French–Italian collaboration for the construction and operation of a 3 km long interferometric gravitational wave antenna. The construction of the detector is already completed and the commissioning is quite advanced, while the data taking is expected to start in 2005. In this paper, we report on the present status of Virgo and on the results of commissioning activity. In particular, we analyse the first four engineering runs (C1–C4) and discuss the sensitivity obtained in C4.

International audience, The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved. Commissioning breaks were organized during the run which permitted improvement of the sensitivity and the robustness of the interferometer against environmental perturbations like bad weather and earthquakes. The post-run commissioning phase has now started, with the goal of preparing the next upgrade step of the detector, Virgo+.

SELECTED PAPERS FROM THE 6TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES, OKINAWA, JAPAN, 20-24 JUNE 2005, International audience, VIRGO interferometer commissioning started in September 2003. The complete lock of the interferometer was achieved in October 2004 via several steps. The main commissioning activity deals with improvements in the interferometer stability and sensitivity. The status of the advancement of VIRGO and the short-term plans are discussed here

International audience

SELECTED PAPERS FROM THE 6TH EDOARDO AMALDI CONFERENCE ON GRAVITATIONAL WAVES, OKINAWA, JAPAN, 20-24 JUNE 2005, International audience, The automatic alignment system of the Virgo interferometer differs substantially from those used in similar experiments, since it uses a variant of the Anderson technique. This implies a completely different control topology with respect to other detectors, and the main feature is a strong coupling of different degrees of freedom in the optical signals. It also provides two extra output ports in which differential wave-front sensors can be placed, namely the light transmitted by the Fabry–Perot arm cavities. We report on the first experimental demonstration of this technique on a large scale recycled interferometer, and on the present status of the automatic alignment system.

International audience, We propose a new method for the detection of spectral lines in random noise. It mimics the processing scheme of matching filtering, i.e., a whitening procedure combined with the measurement of the correlation between the data and a template. Thanks to the original noise spectrum estimate used in the whitening procedure, the algorithm can easily be tuned to various types of noise. It can thus be applied to the data taken from a wide class of sensors. This versatility and its small computational cost make this method particularly well suited for real-time monitoring in gravitational wave experiments. We show the results of its application to Virgo C4 commissioning data.