An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems

Abstract

Rapidly spinning neutron stars with non-axisymmetric mass distributions are expected to generate quasi-monochromatic continuous gravitational waves. While many searches for unknown, isolated spinning neutron stars have been carried out, there have been no previous searches for unknown sources in binary systems. Since current search methods for unknown, isolated neutron stars are already computationally limited, expanding the parameter space searched to include binary systems is a formidable challenge. We present a new hierarchical binary search method called TwoSpect, which exploits the periodic orbital modulations of the continuous waves by searching for patterns in doubly Fourier-transformed data. We will describe the TwoSpect search pipeline, including its mitigation of detector noise variations and corrections for Doppler frequency modulation caused by changing detector velocity. Tests on Gaussian noise and on a set of simulated signals will be presented.PACS numbers: 95.30. Sf, 95.75.Pq, 95.85.Sz, 04.30.Tv, 04.40.Dg ‡ The Australian National Telescope Facility maintains a database of all known radio pulsars at

First all-sky search for continuous gravitational waves from unknown sources in binary systems

“…Assuming a circular, nonrelativistic orbit, the maximum observable Doppler shift will occur for an edgeon observed system with the modulation depth given by [16] Δf max ≃ 1.82 f 0 1 kHz…”

“…The details of the TwoSpect method have been described previously [16]. We briefly summarize the algorithm here.…”

“…Additionally, if such a source is located in a binary system, then the observed waves will have a frequency modulation imposed by the motion of the source in the binary system [15,16]. Together, these frequency modulations make searches for unknown, spinning binary neutron stars emitting continuous gravitational waves computationally demanding.…”

“…Thus, new methods are required to perform such a search with limited computational resources [16,17]. These new techniques require some sacrifice of strain sensitivity to gravitational waves in order to significantly reduce the computational demands of such a search.…”

“…One such algorithm, called TwoSpect [16], has been developed and implemented, and a search has been carried out with it using recently collected LIGO and Virgo data. The TwoSpect algorithm relies on the periodic nature of the frequency modulation caused by the binary orbit.…”