Projects per year
Abstract
Searches for continuous gravitational waves from rapidly spinning neutron stars normally assume that the star rotates about one of its principal axes of moment of inertia, and hence the gravitational radiation emits only at twice the spin frequency of the star, 2f. The superfluid interior of a star pinned to the crust along an axis nonaligned with any of its principal axes allows the star to emit gravitational waves at both f and 2f, even without free precession, a phenomenon not clearly observed in known pulsars. The dualharmonic emission mechanism motivates searches combining the two frequency components of a signal to improve signaltonoise ratio. We describe an economical, semicoherent, dualharmonic search method, combined with a maximum likelihood coherent matched filter, Fstatistic, and improved from an existing hidden Markov model (HMM) tracking scheme to track two frequency components simultaneously. We validate the method and demonstrate its performance through Monte Carlo simulations. We find that for sources emitting gravitational waves at both f and 2f, the rate of correctly recovering synthetic signals (i.e., detection efficiency), at a given false alarm probability, can be improved by ∼10%70% by tracking two frequencies simultaneously compared to tracking a single component only. For sources emitting at 2f only, dualharmonic tracking only leads to minor sensitivity loss, producing 10% lower detection efficiency than tracking a single component. In directed continuouswave searches where f is unknown and hence the full frequency band is searched, the computationally efficient HMM tracking algorithm provides an option of conducting both the dualharmonic search and the conventional single frequency tracking to obtain optimal sensitivity, with a typical run time of ∼103 corehr for one year's observation.
Original language  English 

Article number  123010 
Number of pages  13 
Journal  Physical Review D 
Volume  99 
Issue number  12 
DOIs  
Publication status  Published  13 Jun 2019 

ARC Centre of Excellence for Gravitational Wave Discovery
Bailes, M., McClelland, D. E., Levin, Y., Blair, D. G., Scott, S. M., Ottaway, D. J., Melatos, A., Veitch, P. J., Wen, L., Shaddock, D. A., Slagmolen, B. J. J., Zhao, C., Evans, R. J., Ju, L., Galloway, D., Thrane, E., Hurley, J., Coward, D. M., Cooke, J., Couch, W., Hobbs, G. B., Reitze, D., Rowan, S., Cai, R., Adhikari, R. X., Danzmann, K., Mavalvala, N., Kulkarni, S. R., Kramer, M., Branchesi, M., Gehrels, N., Weinstein, A. J. R., Steeghs, D., Bock, D. & Lasky, P.
Monash University – Internal University Contribution, Monash University – Internal Department Contribution
1/01/17 → 31/03/24
Project: Research

Putting Einstein to the Test: Probing Gravity with Gravitational Waves
1/05/18 → 31/12/20
Project: Research

Extreme astrophysics in the age of gravitational waves
Australian Research Council (ARC), Monash University
30/06/17 → 29/06/21
Project: Research