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Seth Timpano Louis Rubbo Neil Cornish

Characterizing the Gravitational Wave Background using LISA. Seth Timpano Louis Rubbo Neil Cornish. Outline. Motivation Galactic Sources of Gravitational Waves Modeling a Source LISA and Detector Simulations The Full Modulated Signal Bright Sources Confusion Background

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Seth Timpano Louis Rubbo Neil Cornish

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  1. Characterizing the Gravitational Wave Background using LISA Seth Timpano Louis Rubbo Neil Cornish

  2. Outline • Motivation • Galactic Sources of Gravitational Waves • Modeling a Source • LISA and Detector Simulations • The Full Modulated Signal • Bright Sources • Confusion Background • Tests of Normality

  3. Galactic Sources of Gravitational Radiation • Binaries have time varying quadrupole moments • Large number of binaries • Galactic Sources • Unevolved Binaries: 71010 • Catacylsmics: 1.8106 • WUMa: 3107 • Neutron Star Binaries: 1106 • Neutron Star/Black Hole: 5105 • Close White Dwarfs: 3106 • 3107 ??? D. Hils, P. Bender, and R.F. Webbink, Astrophys. J. 360, 75, 1990

  4. Modeling an Individual Source • General Gravitational Wave • Polarization Coefficients • Amplitudes

  5. Galactic Model • Galactic Disk • Sun-Centered Ecliptic Coordinates

  6. Barycenter Combine all source types to arrive at a total barycenter background.

  7. Source Number Density Number of sources per Frequency bin versus frequency.

  8. LISA • NASA/ESA mission • 2014 • Orbital Configuration • 1 AU • 60 degree inclination • 3 spacecraft • 5e6 km arm-length • Sensitive to both + & x • Frequency Response • 10-5 to 100 Hz • Sources • Galactic Binaries • SMBH Mergers • EMRIs

  9. Signal Modulation • Frequency Modulation • Doppler Effect • Amplitude Modulation • Time Varying Antenna Patterns • Phase Modulation • +,x sensitivity

  10. Extended Low Frequency Approximation • Arbitrary Observation Time: • Frequency Evolution: • Arm Response Functions: • Total Response:

  11. Correlations Low Frequency Approximation Rigid Adiabatic Approximation Extended Low Frequency Approximation

  12. Extended Low Frequency Approximation Low Frequency Approximation Rigid Adiabatic Approximation The Accelerated LISA Simulator f < 3mHz f < 7mHz f < 100mHz

  13. The Simulated Background

  14. The Barycenter Background

  15. The Simulated Background

  16. Noise Co-added to Signal

  17. Outlier Removal • Exact Removal • Removal Procedure • Determine initial Confusion Background • Remove all sources with SNR > 5 • Update Confusion Background • Remove all sources with SNR > 5 • Repeat 4 more times

  18. Confusion Background • Definition of the Confusion Background • Estimate of the Confusion Background

  19. Outlier Properties • Source Number and Type • Distance versus Frequency • Source Density

  20. Gaussian?...No Are the Fourier coefficients of the power spectrum normally distributed? Fails to be Gaussian due to outliers in the tails of the distribution. Central Limit Theorem?

  21. Gaussian?...Yes What happens when we remove all the bright sources? The Confusion background is Gaussian.

  22. Summary • Galactic Model of Gravitational Radiation • Detector Simulation • Identification of Outliers and Source Removal • Distinguish Background from Noise

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