T. Accadia

Predictions for the Rates of Compact Binary Coalescences Observable by Ground-based Gravitational-wave Detectors

We present an up-to-date, comprehensive summary of the rates for all types of compact binary coalescence sources detectable by the initial and advanced versions of the ground-based gravitational-wave detectors LIGO and Virgo. Astrophysical estimates for compact-binary coalescence rates depend on a number of assumptions and unknown model parameters and are still uncertain. The most confident among these estimates are the rate predictions for coalescing binary neutron stars which are based on extrapolations from observed binary pulsars in our galaxy. These yield a likely coalescence rate of 100 Myr−1 per Milky Way Equivalent Galaxy (MWEG), although the rate could plausibly range from 1 Myr−1 MWEG−1 to 1000 Myr−1 MWEG−1 (Kalogera et al 2004 Astrophys. J. 601 L179; Kalogera et al 2004 Astrophys. J. 614 L137 (erratum)). We convert coalescence rates into detection rates based on data from the LIGO S5 and Virgo VSR2 science runs and projected sensitivities for our advanced detectors. Using the detector sensitivities derived from these data, we find a likely detection rate of 0.02 per year for Initial LIGO–Virgo interferometers, with a plausible range between 2 × 10−4 and 0.2 per year. The likely binary neutron–star detection rate for the Advanced LIGO–Virgo network increases to 40 events per year, with a range between 0.4 and 400 per year.

Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts

Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipelines ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with similar to 50% or better probability with a few pointings of wide-field telescopes.Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to Oct 20 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipelines ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with ~50% or better probability with a few pointings of wide-field telescopes.

In-vacuum Faraday isolation remote tuning

In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment (Virgo), has a 20 mm clear aperture and is illuminated by an almost 20 W incoming beam, having a diameter of about 5 mm. When going in vacuum at 10(-6) mbar, a degradation of the isolation exceeding 10 dB was observed. A remotely controlled system using a motorized lambda=2 waveplate inserted between the first polarizer and the Faraday rotator has proven its capability to restore the optical isolation to a value close to the one set up in air.

NOISE ANALYSIS IN VIRGO: ON-LINE AND OFFLINE TOOLS FOR NOISE CHARACTERIZATION

T. ACCADIA12, F. ACERNESE6ac, F. ANTONUCCI9a, K. G. ARUN11, P. ASTONE9a, G. BALLARDIN2, F. BARONE6ac, M. BARSUGLIA1, TH. S. BAUER14a, M.G. BEKER14a, A. BELLETOILE12, S. BIGOTTA8ab, S. BIRINDELLI15a, M. BITOSSI8a, M. A. BIZOUARD11, M. BLOM14a, C. BOCCARA3, F. BONDU15b, L. BONELLI8ab, R. BONNAND13, V. BOSCHI8a, L. BOSI7a, B. BOUHOU1, S. BRACCINI8a, C. BRADASCHIA8a, A. BRILLET15a, V. BRISSON11, R. BUDZYŃSKI17b, T. BULIK17cd, H. J. BULTEN14ab, D. BUSKULIC12, C. BUY1, G. CAGNOLI4a, E. CALLONI6ab, E. CAMPAGNA4ab, B. CANUEL2, F. CARBOGNANI2, F. CAVALIER11, R. CAVALIERI2, G. CELLA8a, E. CESARINI4b, E. CHASSANDE-MOTTIN1, A. CHINCARINI5, F. CLEVA15a, E. COCCIA10ab, C. N. COLACINO8a, J. COLAS2, A. COLLA9ab, M. COLOMBINI9b, A. CORSI9a, J.-P. COULON15a, E. CUOCO2, S. D’ANTONIO10a, V. DATTILO2, M. DAVIER11, R. DAY2, R. DE ROSA6ab, M. DEL PRETE8ac, L. DI FIORE6a, A. DI LIETO8ab, M. DI PAOLO EMILIO10ac, A. DI VIRGILIO8a, A. DIETZ12, M. DRAGO16cd, V. FAFONE10ab, I. FERRANTE8ab, F. FIDECARO8ab, I. FIORI2, R. FLAMINIO13, J.-D. FOURNIER15a, J. FRANC13, S. FRASCA9ab, F. FRASCONI8a,