Study of the coincidences between the gravitational wave detectors EXPLORER and NAUTILUS in 2001

Abstract

We report the result from a search for bursts of gravitational waves using data collected by the cryogenic resonant detectors EXPLORER and NAUTILUS during the year 2001, for a total measuring time of 90 days. With these data we repeated the coincidence search performed on the 1998 data (which showed a small coincidence excess) applying data analysis algorithms based on known physical characteristics of the detectors. With the 2001 data a new interesting coincidence excess is found when the detectors are favorably oriented with respect to the Galactic Disk.

Upper limits on gravitational wave bursts in LIGO’s second science run

“…The events seen in coincidence by the two detectors are of an average temperature of approximately 120 mK which according to the authors corresponds to an optimally oriented gravitational wave burst Fourier amplitude of 2:7 10 ÿ21 Hz ÿ1 (equation 4 from Ref. [48]). The rate of such events is of order 200 events/year (or 0.55 events/day) [48,49].…”

“…In their 2002 paper [48] the Rome group that analyzes the data of and operates these two resonant mass detectors reported a slight excess of events seen in sidereal hours between 3 and 5. The events seen in coincidence by the two detectors are of an average temperature of approximately 120 mK which according to the authors corresponds to an optimally oriented gravitational wave burst Fourier amplitude of 2:7 10 ÿ21 Hz ÿ1 (equation 4 from Ref.…”

“…[48]). The rate of such events is of order 200 events/year (or 0.55 events/day) [48,49]. Given the amplitude of the observed events by the resonant mass detectors, the corresponding h rss of the hypothetical events in our LIGO instruments will generally depend on the signal morphology.…”

Considerations on coincidence experiments between two gravitational wave detectors for sources in the Galactic Centre

“…For the Rome experiment the threshold is set at signal-to-noise ratio SNR t = 19.5 (see Astone et al 2001Astone et al , 2002. If the absorbed energy generates a signal exceeding the threshold, then an event is produced, available for the coincidence search with events of another detector.…”

“…In recent coincidence experiments between the two cryogenic resonant detectors EXPLORER and NAUTILUS (Astone et al 2001(Astone et al , 2002 an indication has been given, although not conclusive in terms of discovery of GWs, that a coincidence excess appeared around sidereal hour 4.3, as referred to the average of the detectors locations (EXPLORER: longitude = 6.20…”