The network of resonant bar detectors of gravitational waves resumed coordinated observations within the International Gravitational Event Collaboration (IGEC-2). Four detectors are taking part in this Collaboration: ALLEGRO, AURIGA, EXPLORER and NAUTILUS. We present here the results of the search for gravitational wave bursts over 6 months during 2005, when IGEC-2 was the only gravitational wave observatory in operation. The implemented network data analysis is based on a time coincidence search among AURIGA, EXPLORER and NAUTILUS; ALLEGRO data was reserved for follow-up studies. The network amplitude sensitivity to bursts improved by a factor 3 over the 1997-2000 IGEC observations; the wider sensitive band also allowed the analysis to be tuned over a larger class of waveforms. Given the higher single-detector duty factors, the analysis was based on threefold coincidence, to ensure the identification of any single candidate of gravitational waves with high statistical confidence. The false detection rate was as low as 1 per century. No candidates were found.

We present here the results of a 515 day search for short burst of gravitational waves by the IGEC2 observatory. This network included 4 cryogenic resonant-bar detectors: AURIGA, EXPLORER and NAUTILUS in Europe, and ALLEGRO in America. These results cover the time period from Nov 6 2005 until Apr 15 2007, partly overlapping the first long term observations by the LIGO interferometeric detectors. The observatory operated with high duty cycle, namely 57% for 4-fold coincident observations, and 94% for 3-fold observations. The sensitivity was the best ever obtained by a bar network: we could detect impulsive events with a burst strain amplitude hrss ∼ 1 · 10with an efficiency ¿50%. The network data analysis was based on time coincidence searches over at least three detectors, used a blind search technique and was tuned to achieve a false alarm rate of 1/century. When the blinding was removed, no gravitational wave candidate was found.PACS numbers: 04.80. Nn, 95.30.Sf, 95.85.Sz

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Over the course of a two-week period, starting on Christmas Eve 2003, the recently upgraded AURIGA and the LIGO observatory were simultaneously acquiring data. This first coincidence run between the two projects triggered a new collaborative effort in the search for gravitational wave bursts. This paper introduces the goals of the AURIGA-LIGO joint analysis and the methods that have been formulated to address the challenges of a coincidence between detectors with different spectral sensitivities, bandwidths and antenna patterns. Two approaches are presented, both based on the exchange of event triggers between AURIGA and LIGO: a set of directional coincidence searches, which exploit measured amplitude information, and a cross-correlation search in the LIGO interferometers around the time of the AURIGA events, with minimal assumptions on the signal characteristics.

At the time when the giant flare of SGR1806-20 occurred, the AURIGA "bar" gravitational-wave (GW) detector was on the air with a noise performance close to stationary Gaussian. This allows us to set relevant upper limits, at a number of frequencies in the vicinities of 900 Hz, on the amplitude of the damped GW wave trains, which, according to current models, could have been emitted, due to the excitation of normal modes of the star associated with the peak in x-ray luminosity.