An All-Sky Search for Continuous Gravitational Waves.

Abstract

Gravitational radiation is a direct consequence of general relativity, yet to this day only indirect confirmation of its existence has been obtained.

LIGO is an experiment that aims to detect gravitational waves by comparing the lengths of the two arms of Michelson interferometers. It has recently reached design sensitivity, and a number of searches for intermittent and continuous signals are underway. In particular, isolated rotating neutron stars are expected to emit gravitational radiation of nearly constant frequency and amplitude.

Because the gravitational wave signal amplitudes are thought to be extremely weak, long time integrations must be carried out to detect a signal. The search is complicated by the motion of the Earth (daily rotation and orbital motion) which induces substantial modulations of detected frequency and amplitude that are highly dependent on source location. Large amounts of acquired data make this search computationally difficult.

We describe our search for such signals using an algorithm called PowerFlux and provide upper limits. In particular, at 153 Hz we obtain a sensitivity of 4.25E-25 for circularly polarized sources in the polar sky region. At a signal frequency of 1100 Hz we are sensitive to neutron stars of ellipticity of ~1E-6 at distances up to 500 pc.

We also describe a prototype for a high-sampling-rate wavefront camera that can be used to monitor laser beam characteristics at radio frequencies.