Abstract
A hidden Markov model (HMM) scheme for tracking continuous-wave gravitational radiation from neutron stars in low-mass x-ray binaries (LMXBs) with wandering spin is extended by introducing a frequency-domain matched filter, called the -statistic, which sums the signal power in orbital sidebands coherently. The -statistic is similar but not identical to the binary-modulated -statistic computed by demodulation or resampling. By injecting synthetic LMXB signals into Gaussian noise characteristic of the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO), it is shown that the -statistic HMM tracker detects signals with characteristic wave strain in 370 d of data from two interferometers, divided into 37 coherent blocks of equal length. When applied to data from Stage I of the Scorpius X-1 Mock Data Challenge organized by the LIGO Scientific Collaboration, the tracker detects all 50 closed injections (), recovering the frequency with a root-mean-square accuracy of . Of the 50 injections, 43 (with ) are detected in a single, coherent 10 d block of data. The tracker employs an efficient, recursive HMM solver based on the Viterbi algorithm, which requires CPU-hours for a typical broadband (0.5 kHz) LMXB search.
6 More- Received 12 May 2017
DOI:https://doi.org/10.1103/PhysRevD.96.102006
© 2017 American Physical Society