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Massive Pulsar Surveys: finding the best for gravity science Complete Galactic census

 20. 50. The SKA as a Pulsar Search, Timing and Parallax Machine Jim Cordes, Cornell University. Massive Pulsar Surveys: finding the best for gravity science Complete Galactic census Galactic center (Sgr A* star cluster) Nearby galaxies with periodicity surveys Giant pulses to Virgo

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Massive Pulsar Surveys: finding the best for gravity science Complete Galactic census

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  1. 20 50 The SKA as a Pulsar Search, Timing and Parallax Machine Jim Cordes, Cornell University • Massive Pulsar Surveys: finding the best for gravity science • Complete Galactic census • Galactic center (Sgr A* star cluster) • Nearby galaxies with periodicity surveys • Giant pulses to Virgo • Expected yields • SKA requirements • Timing precision issues • Pulsars as clocks • TOA estimation, optimization • SKA (VLBI) astrometry: parallaxes to >10 kpc • Areas of commonality with LISA & GAIA Jim Cordes Joint LISA/SKA/GAIA Meeting

  2. The SKA as a Pulsar/Gravity Machine • Relativistic binaries (NS-NS, NS-BH) for probing strong-field gravity • Orbit evolution of pulsars around Sgr A* • Millisecond pulsars < 1.5 ms (EOS) • MSPs suitable for gravitational wave detection • 100s of NS masses (vs. evolutionary path, EOS, etc) • Galactic tomography of electron density and magnetic field; definition of Milky Way’s spiral structure • Target classes for multiwavelength and non-EM studies (future gamma-ray missions, gravitational wave detectors) Millisecond Pulsars Relativistic Binaries Today Future Today Future SKA SKA Blue points: SKA simulation Black points: known pulsars only 6! ~104 pulsar detections Jim Cordes Joint LISA/SKA/GAIA Meeting

  3. Magnetars+high-field pulsars • P ~ 5-12 s • B ~ 1014 – 1015 G • Canonical pulsars • P~ 20ms – 5s • B ~ 1012±1 G • Recycled/Millisecond pulsars (MSPs) • P ~ 1.5 – 20ms • B ~ 108 – 109 ms • Braking index n: • Pdot  P2-n, n=3 magnetic dipole radiation • Death line • Strong selection effects log Period derivative (s s-1) Period (sec) Jim Cordes Joint LISA/SKA/GAIA Meeting

  4. Pulsar Search Domains Jim Cordes Joint LISA/SKA/GAIA Meeting

  5. Dmax vs P Dmax = maximum detectable distance for period P given luminosity Lp Detection curves take into account interstellar scattering (NE2001 model) instrumental effects, additive noise Jim Cordes Joint LISA/SKA/GAIA Meeting

  6. Galactic Center Region Sgr A* = 3106 black hole with a surrounding star cluster with ~ 108 stars. Many of these are neutron stars. Detecting pulsars in Sgr A* is difficult because of the intense scattering screen in front of Sgr A*. Multipath differential arrival times d ~ 2000 ν-4 sec Solution: high frequency and large collecting area (SKA) 327 MHz VLA image Jim Cordes Joint LISA/SKA/GAIA Meeting

  7. Jim Cordes Joint LISA/SKA/GAIA Meeting

  8. The brightest pulses in the Universe Cordes et al 2004 Giant pulse from the Crab pulsar S ~ 160 x Crab Nebula ~ 200 kJy Detectable to ~ 1.5 Mpc with Arecibo 6 Mpc with SKA (full) Reach Virgo on strongest pulses? Hankins et al 2003: 2 ns substructure in GPs Jim Cordes Joint LISA/SKA/GAIA Meeting

  9. Birth Rates and Population Numbers The SKA has high detection probabilities for most of these objects  “full Galactic census” of these NS sub- populations Jim Cordes Joint LISA/SKA/GAIA Meeting

  10. Pulsar Timing Precision: Pushing the Limits • Pulsars as clocks • Spin stability: departure from smooth spindown • Phase jitter of pulsar beam w.r.t. spin phase • Intrinsic and extrinsic torques • Pulsar motion and acceleration • Perturbations of the pulses • plasma perturbations (ISM, IPM, ionosphere) • telescope effects: • Additive noise • Instrumental polarization • Time tagging • Matched filter estimation of time of arrival • Barycentric correction • Observatory time and time transfer • What can we do differently and better? • Pre-SKA with Arecibo, EVLA, Parkes, Jodrell, etc. • SKA Jim Cordes Joint LISA/SKA/GAIA Meeting

  11. Differential rotation, superfluid vortices Uncertainties in planetary ephemerides and propagation in interplanetary medium Interstellar dispersion and scattering Glitches Spin noise Emission region: beaming and motion GPS time transfer Additive noise Instrumental polarization Jim Cordes Joint LISA/SKA/GAIA Meeting

  12. Worst timing: • Long periods • Large fields • Fast spindown • Issues: • Differential rotation between crust and superfluid • Torque variations • Accretion events? • injected asteroids log Period derivative (s s-1) • Best timing: • Short periods • Small fields • Slow spindown Period (sec) Jim Cordes Joint LISA/SKA/GAIA Meeting

  13. How Good are Pulsars as Clocks? Jim Cordes Joint LISA/SKA/GAIA Meeting

  14. Phase residuals from isolated pulsars after subtracting a quadratic polynomial: If these pulsars were simply spinning down in a smooth way, we would expect residuals that look like white noise: For these pulsars, the residuals are mostly caused by spin noise in the pulsar Jim Cordes Joint LISA/SKA/GAIA Meeting

  15. MSP J1909-3744 P=3 ms + WD Jacoby et al. (2005) Weighted TOA = 74 ns Shapiro delay Jim Cordes Joint LISA/SKA/GAIA Meeting

  16. ,  + ISS effects (Foster & Cordes 1990) Jim Cordes Joint LISA/SKA/GAIA Meeting

  17. TOA Optimization vs. frequency (modeled): MSP+ SKA Small DM For this case, TOAs are best at ν > 1 GHz but are dominated by pulse phase jitter TOA  T-1/2 so longer integration times can push the error down to 10 ns Jim Cordes Joint LISA/SKA/GAIA Meeting

  18. TOA Optimization vs. frequency (modeled): MSP+ SKA Large DM For this case, TOAs are best at ν > 2 GHz because of scattering but are dominated by pulse phase jitter TOA  T-1/2 so longer integration times can push the error down to 10 ns Jim Cordes Joint LISA/SKA/GAIA Meeting

  19. Mitigation of TOA Estimation Errors • Polarization purity • need -40dB accuracy after hardware and post processing across the entire FOV used for timing • Pulse amplitude/phase jitter •  limitations on optimality of matched filtering • Error-correction algorithms: use correlations of pulse shape perturbation with TOA perturbation (unpublished) • Electron density fluctuations in the ISM • 103 km to > pc (~Kolmogorov) • DM(t) … correctable • Time-variable pulse-broadening function … partly correctable • Secular (months, years): refractive modulation • N effects from finite number of scintles in the f-t plane • Time-variable angle of arrival • Refraction from large-scale structures in the ISM • Use high frequencies Jim Cordes Joint LISA/SKA/GAIA Meeting

  20. Pulse Timing Efficiency with the SKA • Follow up timing required to varying degrees on the >104 pulsars discoverable with SKA • Spin parameters, DM and initial astrometry • Orbital evolution for relativistic binaries • Gravitational wave detection using MSPs • Each deg2 will contain only a few pulsars  efficient timing requires large solid-angle coverage (lower frequencies, subarrays, wide intrinsic FOV, or multiple FOVs) Jim Cordes Joint LISA/SKA/GAIA Meeting

  21. Pulsar Astrometry with the SKA(interferometry on long baselines) • Pulse timing models and reference frame definition • Proper motions and parallaxes for objects across the Galaxy  monitoring programs over ~ 2 yr/pulsar • Optimize steep pulsar spectra against -dependence of ionospheric and tropospheric and interstellar phase perturbations ( 2 to 8 GHz) • Current state of the art: 4 kpc using VLBA ~ 1%  SKA • In-beam calibrators (available for all fields with SKA) • 10% of A/T on transcontinental baselines implies 20 times greater sensitivity over existing dedicated VLB arrays Jim Cordes Joint LISA/SKA/GAIA Meeting

  22. Chatterjee et al. 2005 B1508+55 l,b = 91.3o, 52.3o D = 2.450.25 kpc V = 1114-94+132 km s-1 P = 0.74 s B = 2x1012 G  = P/2Pdot = 2.36 Myr The highest measured velocity using direct distance measurement 2.5x further than electron density model based distance estimate (NE2001) Possibly born in Cyg OB 7 Jim Cordes Joint LISA/SKA/GAIA Meeting

  23. SKA Specifications Summary for Fundamental Physics from Pulsars Jim Cordes Joint LISA/SKA/GAIA Meeting

  24. Summary & Discussion • SKA will discovery many binaries and MSPs suitable for • Testing gravity in the strong field limit • nHz gravitational wave detection • Objects can be “cherry picked” to be the best clocks • Methods exist or are under development for correcting TOAs for intrinsic self noise (jitter) and instrumental polarization • Commonality between LISA, GAIA and SKA/pulsar communities: • Overall goals (gravitational waves as target and tool) • Astrophysical populations • Methodologies (matched filtering, sparse signal detection amid noise) • Promotion of gravity science in a competitive funding world Jim Cordes Joint LISA/SKA/GAIA Meeting

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