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Searches for continuous gravitational waves in the advanced detector era

This document discusses ongoing searches for continuous gravitational waves (CW) in the Advanced Detector Era, focusing on the LIGO Scientific Collaboration and the Virgo Collaboration. It provides information on the LIGO/Virgo frequency band, potential sources of CW, expected amplitudes, computational bounds, types of searches, optimization and improvement strategies, and future prospects. Get involved at the provided link.

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Searches for continuous gravitational waves in the advanced detector era

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  1. Searches for continuous gravitational waves in the advanced detector era Ra Inta (Texas Tech University) for the LIGO Scientific Collaboration and the Virgo Collaboration LIGO Document G1601064-v4

  2. No Continuous gravitational Waves (CW) detected… yet! • Most searches begin after an observing run has ended • Still analysing LIGO O1 data

  3. CW Sources • LIGO/Virgo band: O(10) Hz – O(1) kHz • Rotating neutron stars with some non-axisymmetry • Axions?

  4. Animation: Joeri van Leeuwen

  5. Triaxial model

  6. Deviation from axisymmetry: ellipticity Determines maximum height of ‘hills’ supported within NS crust ( O(few) cm )

  7. Expected amplitudes

  8. Expected amplitudes Caltech/MIT/LIGO Lab Abbott, B.P. et al., PRL116:061102 (2016)

  9. Expected amplitudes

  10. Fluid modes r-mode instability B. Owen/C. Hanna

  11. Precession (plus side-bands) M. Kramer

  12. Neutron star population

  13. Neutron star population Where are the other ~108 neutron stars?

  14. aLIGO sensitivity ~17% of (known) pulsars ~23% of (known) pulsars ~36% of (known) pulsars B.P. Abbott et al., PRL116:131103 (2016)

  15. Computational bound Averaging means most CW searches are computationally limited e.g.: typical, modest, search takes ~400,000 CPU hrs on Albert Einstein Institute’s Atlas supercomputer Bounds often explicitly used to determine a figure of merit for CW searches

  16. What if we make a detection? • Follow-up with multiple search pipelines • Compare GW phase to EM pulse timing • Potential for EM follow-up • Potential confirmation of many neutron star properties • Test General Relativity • Constrain neutron star equation of state

  17. D. Page

  18. Adapted from Horowitz, C.J. and Kadau, K., PRL102:191102 (2009)

  19. Types of CW searches

  20. 1) Targeted searches • What we know: α, δ, f0, df/dt • Searches can be narrow-band around parameters • Three pipelines NASA/ESA/J. Hester/A Loll

  21. 1) Targeted searches Crab Vela • Meaningful limits on Vela and Crab • Good prospects for aLIGO! Aasi, J et al., ApJ.785:119(2014)

  22. 1) Targeted searches • Narrow-band around parameters of Crab and Vela • Robust w.r.t to model assumptions • Looked at five partial harmonics per target • Meaningful upper limits set on both: 0.50 and 0.97 expected (spin-down) h0 respectively Aasi, J. et al., PRD91:022004 (2015)

  23. 2) Directed searches • What we know: α, δ • Search over: f0, df/dt, d2f/dt2, … NASA/Chandra/STScI/Spitzer

  24. 2) Directed searches Young supernova remnants Adapted from NASA/JPL-Caltech/ESO/R. Hurt., with permission Aasi, J. et al. ApJ.813(1) 39 (2015)

  25. 2) Directed searches • Beat age-based upper limit on nine supernova remnants • Constraints on r-mode amplitudes • Many more targets in O1 Aasi, J. et al. ApJ.813(1) 39 (2015)

  26. Sco-X1 • J.T. Whelan’s talk • Y. Zhang’s talk • G. Meadors’ poster Sco-X1 Mock Data Challenge Aasi, J. et al., PRD91:062008 (2015) Messenger, C. et al., PRD92:023006 (2015)

  27. 3) All-sky searches • What we know: - • Search over: α, δ,f0, df/dt, …

  28. 3) All-sky searches Low frequency all-sky (frequency Hough) --- Virgo • Virgo VSR2 and VSR4 data • Hierarchical Hough-transform in frequency domain • Best upper limits below 80 Hz Aasi, J. et al., PRD93:042007 (2016)

  29. 3) All-sky searches PowerFlux (S6) • Most comprehensive coverage of parameter space to date • Uses distribution-free ‘universal statistic’ to reduce impact of non-Gaussian noise • ‘Loosely coherent’ follow-up arXiv:1605.03233

  30. 3) All-sky searches: binaries • TwoSpect • Polynomial Aasi, J. et al., PRD90:062010 (2014)

  31. 3) All Some-sky searches Loosely coherent search in Orion's Spur • Deeper search in small patch of sky • Multiple stages of increasing coherence • Identified 70 candidates • Three most significant ruled out by other pipelines Aasi, J. et al., PRD93:042006 (2016)

  32. Pipeline optimisation and improvements • Directed search optimisations -- J. Ming’s talk • Parameter space improvements -- Wette, K., PRD92:082003 (2015); Jones, D.I., MNRAS453:53 (2015); Leaci, P., and Prix, R., PRD91:102003 (2015) • Searches for time-limited CWs -- Keitel, D., arXiv:1509.02398 • Semi-coherent all-sky improvements -- Goetz, E. and Riles, K., CQG33:085007 (2016) • Non-GR alternatives -- Isi, M. et al., PRD91:082002 (2015)-- see M. Isi’s poster • Many more!

  33. Summary and the future • Many improvements made to search pipelines • Increasingly better upper limits and parameter space coverage • No detection… yet • The future looks bright!

  34. How can you get involved? https://einstein.phys.uwm.edu/ A. Singh’s talk

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