P. Astone

First cooling below 0.1-K of the new gravitational wave antenna 'Nautilus' of the Rome group

We report on the first cryogenic test at ultralow temperature of the new gravitational-wave antenna Nautilus of the Rome group. The 2390 kg Al 5056 cylindrical-bar antenna has been cooled to a temperature of 95 mK.

Data analysis of gravitational-wave signals from spinning neutron stars. IV. An all-sky search

We develop a set of data analysis tools for a realistic all-sky search for continuous gravitational-wave signals and we test our tools against simulated data. The aim of the paper is to prepare for an analysis of the real data from the EXPLORER bar detector; however, the methods that we present apply both to data from the resonant bar detectors that are currently in operation and the laser interferometric detectors that are in the final stages of construction and commissioning. With our techniques we shall be able to perform an all-sky coherent search of 2 days of data from the EXPLORER detector for a frequency bandwidth of 0.76 Hz in one month with 250 Mflops computing power. This search will detect all the continuous gravitational-wave signals with the dimensionless amplitude larger than

Increasing the Bandwidth of Resonant Gravitational Antennas: The Case of Explorer

2.8ifmmodetimeselsetexttimesfi{}{10}^{ensuremath{-}23}

Coincidence experiments between interferometric and resonant bar detectors of gravitational waves

with 99% confidence, assuming that the noise in the detector is Gaussian.

Energetic cosmic rays observed by the resonant gravitational wave detector NAUTILUS

Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG Collaboration, has been upgraded with a new readout. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its center operating frequency of 919 Hz the spectral sensitivity is better than 10(-20) Hz(-1/2). We describe the detector and its sensitivity and discuss the foreseeable upgrades to even larger bandwidths.

Search for Periodic Gravitational Wave Sources with the EXPLORER detector

Gravitational wave coincidence experiments between bars and interferometers may be an attractive option once the new generation of full scale interferometers begins taking data. We discuss various ways in which these disparate types of data can be compared in searches for bursts (from supernovae, for example), for pulsar signals, and for a stochastic background. Comparison of broadband interferometer data with narrowband bar data is appropriate in most searches for bursts, but in many cases the results---especially null results (upper limits)---are difficult to interpret. By narrowbanding the interferometer data to the bandwidth of the bar detector, one produces data sets that may give much clearer information in certain burst searches and that are appropriate for searches for a stochastic background of gravitational waves. We suggest, in fact, that there are circumstances where searches for a stochastic background could be more efficiently performed between a bar and an interferometer than between two interferometers. We examine, in some detail, the effect of narrowbanding the interferometer data. We apply this method to a real interferometer and bar data and assess its signal-to-noise performance for different classes of gravitational wave signals.

Status report on the EXPLORER and NAUTILUS detectors and the present science run

The passage of cosmic rays has been observed to excite mechanical vibrations in the resonant gravitational wave detector NAUTILUS operating at temperature of 100 mK. A very significant correlation (more than 10 standard deviations) is found.

Detection of high energy cosmic rays with the resonant gravitational wave detectors NAUTILUS and EXPLORER

We have developed a procedure for the search of signals from periodic sources in the data of gravitational wave detectors. We report here the analysis of one year of data from the resonant detector Explorer, searching for sources located in the Galactic Center ~GC!. No signals with amplitude greater than h 52.9310 224 ,i n the range 921.32‐921.38 Hz, were observed using data collected over a time period of 95.7 days, for a source located at a517.7060.01 h and d5229.0060.05 deg. Our procedure can be extended for any assumed position in the sky and for a more general all-sky search, with the proper frequency correction to account for the spin-down and Doppler effects.

Method for all-sky searches of continuous gravitational wave signals using the frequency-Hough transform

We report on the present scientific run (04–05) of the two detectors EXPLORER and NAUTILUS. The 04–05 run of the two detectors started in March 2004. The strain sensitivity is about 7 × 10−22 Hz−1/2 and the bandwidth is about 5 Hertz. The sensitivity for 1 ms bursts is h = 3 × 10−19.

Resonant gravitational wave antennas for stochastic background measurements

Abstract The cryogenic resonant gravitational wave detectors NAUTILUS and EXPLORER, made of an aluminum alloy bar, can detect cosmic ray showers. At temperatures above 1xa0K, when the material is in the normal-conducting state, the measured signals are in good agreement with the expected values based on the cosmic rays data and on the thermo-acoustic model. When NAUTILUS was operated at the temperature of 0.14xa0K, in superconductive state, large signals produced by cosmic ray interactions, more energetic than expected, were recorded. The NAUTILUS data in this case are in agreement with the measurements done by a dedicated experiment on a particle beam. The biggest recorded event was in EXPLORER and excited the first longitudinal mode to a vibrational energy of ∼670 K, corresponding to ∼360 TeV absorbed in the bar. Cosmic rays can be an important background in future acoustic detectors of improved sensitivity. At present, they represent a useful tool to verify the gravitational wave antenna performance.