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Gravitational Wave and Pulsar Timing

Gravitational Wave and Pulsar Timing. Xiaopeng You , Jinlin Han, Dick Manchester National Astronomical Observatories, Chinese Academy of Sciences. Outline. Gravitational Wave Physics of gravitational waves Gravitational wave detection Gravitational wave sources

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Gravitational Wave and Pulsar Timing

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  1. Gravitational Wave and Pulsar Timing Xiaopeng You, JinlinHan, Dick Manchester National Astronomical Observatories, Chinese Academy of Sciences

  2. Outline • Gravitational Wave • Physics of gravitational waves • Gravitational wave detection • Gravitational wave sources • Detecting G-wave by Pulsar Timing • Introduction to pulsar timing • PPTA project • Directly detecting gravitational wave • Effect of ISM on Pulsar Timing • Dispersion measure change • Scintillation

  3. Gravitational Wave: Ripples in Spacetime! • Einstein field equation • Weak field approximation • Gravitational wave equation

  4. Properties of G-wave • Quadrupole moment • Two polarization states “+” “×” • Generation of G-waves

  5. G-wave Detection • Interferometer detector • Basic formula: • LIGO: h~10-22, L=4 km, L~10-17cm • LISA: h~10-21, L=5×106 km, L~10-10cm • Pulsar timing as G-wave detector • See pulsar timing part

  6. G-wave Sources • High frequency (10 ~ 104 Hz, LIGO Band) • Inspiraling compact binaries (NS and BH, MBH103M ) • Spinning neutron star • Supernovae • Gamma ray bursts • Stochastic background • Low frequency (10-4 ~ 1 Hz, LISA Band) • Galactic binaries • Massive BH binary merger (104M  MBH109M ) • MBH capture of compact object • Collapse of super massive star • Stochastic background

  7. G-wave Sources • Very low frequency (10-9 ~ 10-7 Hz, pulsar timing) • Processes in the very early universe • Big bang • Topological defects, cosmic strings • First-order phase transitions • Inspiral of super-massive BH (MBH>1010M ) • Extremely low frequency (10-18 ~ 10-15 Hz) • Primordial gravitational fluctuations amplified by the inflation of the universe • Method: imprint on the polarization of CMB radiation

  8. Pulsar Timing • Pulsars are excellent celestial clocks, especially MSP • Basic pulsar timing observation • The timing model, inertial observer • Correct observed TOA to SSB • Series TOAs corrected to SSB: ti • Least squares fit time residual

  9. Modeling Timing Residual and Timing “Noise” From Hobbs et al. (2005)

  10. Source of Timing Noise • Receiver noise • Clock noise • Intrinsic noise • Perturbations of pulsar motion • G-wave background • Globular cluster accelerations • Orbital perturbations • Propagation effects • Wind from binary companion • Variants in interstellar dispersion • Scintillation effects • Perturbations of Earth’s motion • G-wave background • Errors in the Solar-system ephemeris

  11. Indirect evidence of G-wave PSR B1913+16 • First observational evidence of G-wave Nobel Prize for Taylor & Hulse in 1993 ! From Weisberg & Taylor (2003)

  12. Pulsar Earth Detect G-wave by pulsar timing Photon Path • Observation one pulsar, only put limit on strength of G-wave background • New limits on G-wave radiation (Lommen, 2002) G-wave

  13. Direct detection of G-wave • Observation of many pulsars • Effect of G-wave background • Uncorrelated on individual pulsars • But correlated on the Earth • Method: two point correlation • Sensitive wave frequency 10-8 Hz

  14. PPTA project • Goal: detect G-wave & establish PSR timescale • Timing, 20 MSPs, 2-3 week interval, 5 years • 3 frequencies: 700 MHz, 1400 MHz and 3100 MHz • TOA precision: 100 ns > 10 pulsars, 1 s for others

  15. Detect G-wave background Simulation using PPTA pulsars with G-wave background from SMBH (Jenet et al.)

  16. Detect G-wave background G-wave from SMBH A) Simple correlation, B) Pre-whiten 20 psrs, 100 ns, 250 obs, 5 years Low-pass filtering 20 psrs, 100 ns, 500 obs, 10 years 20 psrs, 100 ns, 250 obs, 5 years 10 psrs, 100ns, 10 psrs, 500 ns, 250 obs, 5 years 10 psrs, 100 ns, 250 obs, 5 years From Jenet et al. (2005)

  17. ISM Effect on Pulsar Timing1. Dispersion measure variation What we will do: Calculate DM change for PPTA pulsars, improve the accuracy of pulsar timing PSR B0458+46 Method: Obtain DM from simultaneous multi-frequency observation From Hobbs et al. (2004)

  18. ISM Effect on Pulsar Timing2. Scintillation effect • Scintillation affects precision of pulsar timing • Second dynamic spectrum can deduce the time delay PSR B1737+13 What we will do: Study scintillation effect on PPTA pulsars, improve the accuracy of pulsar timing From Stinebring & Hemberger (2005)

  19. Summary • Gravitational wave detection is a major goal for current astronomy • PPTA project has a chance for directly detecting gravitational wave • Lots of works still need to be done to improve the accuracy of pulsar timing

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