Gravitation, Cosmology, and Cosmic-Ray Physics (1986) / Chapter Skim
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6. Search for Gravitational Waves: Opportunities
6. Search for Gravitational Waves: Opportunities
Pages 49-58
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From page 49... ...
LASER INTERFEROMETER DETECTOR WITH 5-KILOMETER BASELINE In the limit where random forces on the end masses dominate the antenna noise budget, the gravitational-wave amplitude sensitivity of a laser interferometer improves with arm length as h x LO (assuming that L is less than half the wavelength)
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From page 50... ...
Laser FIGURE 6.1 One half of a proposed long-baseline interferometric gravity-wave detector. A passing gravitational wave changes the light travel times differently in the two interferometer arms, causing a tiny shift in the light intensities at the detectors.
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From page 51... ...
This figure indicates projected sensitivities of the various gravitational-wave detection schemes for impulsive or burst sources. The sensitivities are given in terms of the rms strain noise of the detectors in a frequency band equal to the reciprocal pulse length.
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From page 52... ...
~ PSR 1913+46 ~ \ hems I \Puls~ _ Untuned ~ Crab Tuned Bar Vel a ~ O ~ Detector ~ Neutron Star Sources `` Spinup ~- Binary Confusion Limit Tuned _ · Individual Binary Systems o Eccentric Rotators (c = 10~5 ) is ims _4 -2 O LOG FREQU E NCY FIGURE 6.3 Prospects for detecting periodic gravitational waves.
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From page 53... ...
The straight lines in the figure are the strain spectral densities of a universe filled with the indicated fraction of the closure density in gravitational waves on the assumption that all the gravitational radiation power is concentrated in a bandwidth equal to the frequency. This figure also indicates those sources of noise that are expected to limit the sensitivity of the interferometric detectors.
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From page 54... ...
Within a decade, further improvement of strain sensitivity by 2 to 3 orders of magnitude should be achievable, through further cryogenic cooling and use of advanced transducers and amplifiers. Techniques are also under study to increase the bandwidth of bar detectors; the use of cascaded, strongly coupled mechanical resonators can in principle give both high sensitivity and wide bandwidth in a single bar.
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From page 55... ...
Further searches for millisecond periods among x-ray pulsars should also be carried out, because accreting neutron stars with rotational periods in the millisecond range could be significant periodic sources of gravitational waves. SPACECRAFT TRACKING Accurate tracking of interplanetary spacecraft offers, at present, our only opportunity to search for gravitational radiation in the frequency range 10-' to 10-4 Hz.
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From page 56... ...
This is also the frequency range for detecting broad spectral features due to the superimposed radiation from many white-dwarf binary systems and from classical binary systems. The expected energy density in gravitational waves from such sources is about 10-8 Pc (see Figure 6.41.
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From page 57... ...
EVENT RATES AND SOURCE CALCULATIONS Theoretical activity in modeling possible sources, and in attempting to determine their frequency of occurrence in the universe, is key to an effective search for gravitational waves. The main uncertainties in theoretical estimates of gravitational-wave source properties are not due to physical understanding, which we think is good, or computational ability, which is already considerable and steadily improving, but to our uncertainties about the astrophysical boundary conditions.
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From page 58... ...
Deep radio pulsar searches at millisecond periods, and searches for millisecond periodicities in known x-ray sources, also require substantial computational power. Computational needs for gravitational-wave source calculations are discussed in Chapter 9 in the section on Computation.
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