A Search for Gravitational Waves from Coalescing Binary Stars Using the Caltech 40 Meter Gravity Wave Detector

Citation

Smith, Sheryl Leigh (1988) A Search for Gravitational Waves from Coalescing Binary Stars Using the Caltech 40 Meter Gravity Wave Detector. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/qnyb-hd62. https://resolver.caltech.edu/CaltechTHESIS:02222013-093632973

Abstract

A search for gravitational radiation from coalescing compact binary stars was conducted. This is the first time that the Caltech gravity wave detector has been used to search for burst sources. This detector is made of two 40 meter Fabry-Perot interferometers. The mirrors of the Fabry-Perot cavities are suspended, so that they are free to move in response to a gravity wave. The Caltech detector is a prototype for a set of larger detectors (4 km long cavities). The purpose of this search was to develop techniques applicable to the larger detectors.

An algorithm was developed which searches for the distinctive waveform of a coalescing binary, regardless of the masses of the stars in that binary. Thirty-six minutes of data were analyzed. These data spanned one hour and were collected when the Glasgow detector was also operating, (the Glasgow and Caltech detectors had comparable sensitivity at the time of this experiment). The limit this search sets varies with the mass parameter, η, which is a function of the stars' masses. For two 1.4M_ʘ stars no coalescences were observed with h > 5 x 10⁻¹⁷; this corresponds to a binary approximately 25 parsecs away.

At the time of this experiment the Caltech detector had a displacement sensitivity of 10⁻¹⁷ m/√(HZ) at frequencies near 1kHz. Since then the detector has improved so that at frequencies near 1kHz the displacement sensitivity is 4 x 10⁻¹⁸m/√(HZ). At this level of sensitivity there are many conceivable sources of noise which must be considered and, if necessary, eliminated. How fluctuations in the spatial geometry of the input beam and the cavities can cause displacement noise is discussed in Chapter 4. Work which has been done to reduce these fluctuations is also described.

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