No abstract

Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching cosmological, where the event rate may be many per year. Because the binary's accumulated orbital phase can be measured to a fractional accuracy <^C 10~3 and relativistic effects are large, the wave forms will be far more complex and carry more information than has been expected. Improved wave form modeling is needed as a foundation for extracting the waves' information, but is not necessary for wave detection.

Searches for gravitational waves with the LIGO-VIRGO-GEO detector network will require families of "search templates" with which to cross correlate the noisy detectors' output. This paper introduces a fitting factor (FF), as a quantitative measure of how well the best template in a family "fits" a hypothetical gravitational waveform, in the presence of a specific detector noise spectrum. An F F < 0.9 corresponds to a 27% reduction in the event rate of the relevant signals; therefore a family of templates that leads to FF's below 0.9 should be considered inadequate. The F F is used to explore the adequateness of several families as search templates for gravitational waves from compact inspiraling binaries. The binaries are taken to move in circular orbits, and the "advanced LIGO noise spectrum" is assumed for the detectors. We first study the acceptability of the simplest three-parameter template family, the so-called "Newtonian family." From previous studies by Finn, Krblak, Kokotas, Schafer, Dhurandar, and Balasubramanian, we infer that post-Newtonian effects in the true waveforms of binaries with vanishing spins cause the Newtonian family to have a n unacceptable low F F (-0.6 to 0.8). We then study the influence of waveform modulations caused by spin-induced orbital precession, and we isolate the modulation effects from other post-Newtonian effects by pretending that the true signals are pure Newtonian with modulation. Many different parameters influence the precession and then the waveform modulation. A wide range of parameter values is explored, and intuition is developed into which parameters most strongly influence the FF. It is shown that the unmodulated Newtonian template family works quite well ( F F > 0.9 for almost all parameter values) in searches for the modulated Newtonian signal from two 1.4Mo neutron stars (NS's) with, one of them maximally spinning. By contrast, for a maximally spinning 10Mo black hole (BH) with a nonrotating 1.4Mo NS, the Newtonian template family produces F F < 0.9 for more than half of all the binaries' orientations, if the spin and orbital angular momenta are misaligned by 30°. We introduce a new four-parameter template family, which has the form of the nonmodulated postl-Newtonian signal from a zero-spin-binary. Although, there is a substantial improvement of the FF's for a spin-modulated Newtonian signal, the FF's for nonmodulated post1.5-Newtonian waveforms are still very poor (-0.5-0.8). Therefore we propose another four-parameter template family that has the same form as a nonmodulated post1.5-Newtonian signal with all the spin-related parameters stripped off. This template family works post1.5-~ewtonian modulated signals quite well. These results suggest that, in a few years, when waveforms have been computed up to post3-Newtonian order, a good template family will be the four-parameter post3-Newtonian waveforms for zero-spin binaries, augmented by some appropriate modulations to deal with misaligned, rapidly spinning BH-NS systems. Finally, we extend our investigation...

We study the problem of detecting, and inferring astrophysical information from, gravitational waves from a pulsating neutron star. We show that the fluid f and p modes, as well as the gravitational‐wave w modes, may be detectable from sources in our own Galaxy, and investigate how accurately the frequencies and damping rates of these modes can be inferred from a noisy gravitational‐wave data stream. Based on the conclusions of this discussion we propose a strategy for revealing the supranuclear equation of state using the neutron star fingerprints: the observed frequencies of an f and a p mode. We also discuss how well the source can be located in the sky using observations with several detectors.