Gravitational Wave Sources

The emission of gravitational waves is caused by the quadrupole moment Q of the source, according to this 

The quadrupole moment can be approximated by Q Mfi, where M is the source mass and I the scale of deviation from symmetry. An axisymmetric body does not radiate gravitational waves. The strongest gravitational radiators are nonspherical, with Q 2Mv 4 Jf, where v is the velocity, is the nonspherical component of kinetic energy  

A binary system of two masses M at distance ro rotating with frequency / about their common center of mass exhibits the maximum variation of quadmpole moment since the whole kinetic energy is nonspherical. The emission occurs at twice the rotation frequency with this intensity  

Due to the tiny value of the factor 8 x man-made gravitational waves are by far too weak to be detected. A hypothetical dumbbell made of two masses of 10 kg at the ends of a 10-m rod rotating at 10 Hz about the center of mass produces waves with an amplitude below h 10 ° in the wave zone. The candidate gravitational wave sources are very compact and heavy celestial bodies, like neutron stars and black holes. Bodies with strong 

Since a gravitational source of mass M cannot be smaller than its Schwarzschild radius, the emission frequency cannot exceed the reciprocal of the travel time of light along Ts  

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GRAVITATIONAL WAVES are ripples in space-time caused by the coherent accelerated motion of massive bodies. The potential gravitational wave sources span a wide range of cosmic environments neutron stars, black holes, supernovae, and binary systems. This review focuses on the instruments currently under construction that are expected to perform the first direct detection of gravitational waves. 

A spherical object cannot radiate gravitational waves (quadrupolar source term). 

Proc. of the International summer school on Experimental physics of gravitational waves, (Barone, M. et al. Eds., World Scientihc, London 2000). Contains a valuable chapter on General relativity by P. Tourrenc (contains a precise description of the various coordinates systems and their use, OBLIGATORY), a chapter by S. Bonazzola and E. Gourgoulhon on compact sources, in particular neutron stars, and a chapter by Jean-Yves Vinet on numerical simulations of interferometric gw detectors. 

This is an extremely small quantity, which combined with the also extremely small interaction of gravitational waves (GWs) with matter makes it impossible to generate and detect GW on earth. Fast conversions of solar-size masses are required to produce signals with amplitudes that could be detectable. Astrophysical sources are for instance supernova explosions or a collision of two neutron stars or black holes. 

The modelling of the coalescence of two NSs or of a NS and a BH has recently attracted a flurry of interest (see the review by [24]). These events are indeed considered as being among the strongest known sources of gravitational wave radiation, this emission being in fact responsible for the coalescence after... 

Since their installation the aLIGO PSLs operate stable and provide reliable light sources for the gravitational wave detectors. 

To achieve the required sensitivity, the laser source has to be frequency and amplitude stabilized, and the entire optical path of the interferometer has to be housed in a vacuum of 10 torr. Real gravitational waves can be distinguished from instmmental and environmental noise by correlating the outputs of two interferometers at widely separated sites. More information can be extracted from... 

Ground-based interferometers and resonant-mass detectors operate in this band. The most promising sources of gravitational waves are inspiral and coalescence of compact stellar-mass black holes and... 

The end-over-end tumble of binary star systems is an excellent source of gravitational waves in both the LF and HF bands. The gravitational wave frequency increases with the total mass of the system, and is inversely proportional to the separation of the binary elements. Thus, compact binaries composed of neutron stars and/or stellar-mass black holes radiate at the highest frequencies since the elements can get very close together without merging. 

Current knowledge of the physics of the early universe is highly speculative, as are the sources of the stochastic background described below. However, gravitational wave astronomy may provide the only method of directly observing the conditions in the universe as early as sec after the big bang (in the HF band) since... 

Efforts to directly observe gravitational waves have a history spanning at least 40 years Joseph Weber constructed the first resonant mass detectors in the early 1960s. At the start of the 21st century, a new generation of interferometric detectors will have sufficient sensitivity to detect many anticipated astrophysical sources. The commissioning and scientific operation of these instruments marks the birth of gravitational wave astronomy. 

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