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A. J. Farmer, E. S. Phinney (Caltech)
The dominant gravitational wave background in the LISA (Laser Interferometer Space Antenna) frequency range (0.1 -- 10 mHz) comes from double white dwarf (DWD) binaries. At frequencies above the confusion limit for Galactic systems (~ 3 mHz), the integrated background from extragalactic DWDs limits the sensitivity of LISA and its successors. Since gravitational waves suffer no extinction, signals from DWDs over all of cosmic time contribute to this isotropic background. We use a population synthesis approach to characterize the cosmic DWD population, and calculate its gravitational wave spectrum as received today, identifying the relative contributions from different WD--WD (and WD--helium star) pairings and from interacting binaries. We also calculate redshift-dependent merger rates and chirp mass distributions for the inspiraling sources, and consider carefully the uncertainties in such a calculation. Measurement of this background level by LISA and its successors will provide a useful integral constraint on cosmic star formation history and theories of binary star evolution.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.