The possibility of gravitational waves has been known for a long time, but they have never been observed.
The possible sources (or detectors) of gravitational radiation (GR) are only of quadrupole character and have, therefore, very small effectiveness (this is also due, of course, to the very small value of the specific gravitational charge; see, e.g., Braginskij 1965). Over the last three decades theoreticians and experimentators have often considered stellar binary systems with short orbital periods P and large masses amongst the most favourable sources of extraterrestrial GR. For a binary, the radiation is emitted at a fundamental frequency equal to twice the orbital frequency , and also at higher harmonics - from the third (for eccentricity ) to the tenth (for ) (Press & Thorne 1973). The GR background from binaries in the Galaxy might exceed that of cosmological origin at frequencies Hz (Sazhin 1978; Lipunov & Postnov 1987).
The inverse situation must also be considered: if GR, or, perhaps, quasi-GR (QGR), is present at some discrete frequency(ies) it could produce an observable effect on close binaries. This hypothetical monochromatic GR or QGR, might be of a relic of early stages of the Universe, or due to a mutual quasi-gravitational resonance between short-period binaries themselves; see also below. We propose to use the statistics of periods of the entire sample of close binary systems (CBS's) is proposed to be of interest as a test for the existence of monochromatic gravitational waves (GWs) (or quasi GW's) in the Universe.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998