Improving Pulsar Timing Willem van Straten George Hobbs
Improving Pulsar Timing Willem van Straten George Hobbs, Rick Jenet
Why? • Gravitational Wave detection/sensitivity • MSPs binary system dynamics • Astrometry: – Solar System Ephemeris – Earth Wobble • Terrestrial Time • Timing Noise (incl. glitches)
Observatory Number of pulsars Observing span (yr) System Observing frequency Rms Jodrell Bank ~600 0 -35 FB 600 -1600 MHz >10 us Parkes msps 15 ~10 CD 1. 4 GHz, 3 GHz >100 ns Parkes young 114 ~10 FB 1. 4 GHz PPTA 20 2 CD/DFB 600 MHz, 1. 4/3 /CORR GHz >100 ns Arecibo 7 ~20 CD 0. 4/1. 4/2. 4 GHz >200 ns Greenbank 15 EPTA (Effelsberg/ ~30 CD 115 MHz – 8 GHz ~1 us 15 CD ~1. 4 GHz ~500 ns FB 1. 5 GHz >100 us Westerbork/ Jodrell Bank) Nancay Urumqi 284 10 Hartebeesthoek 30 15 GMRT 1 (1937+21) 2 1. 6/2. 3 GHz FB/CD 325/610 MHz ~1 us G. Hobbs
Software/Modeling Numerical Precision (Noise) Interstellar Scintillation RFI Mitigation Earth Wobble Solar System Ephemeris Earth Atmosphere Solar Wind DM Variation Clock Correction Sensitivity Time/Freq Resolution Hardware/Instrumentation Accuracy (Systematics) Arrival Time Estimation Time Standard Polarimetric Calibration
Modelling Software (tempo 2) • Clock Corrections • Physical Delays: • Solar System Ephemeris (incl. Shapiro delay) • Earth Wobble precession & nutation (40 ns) polar motion (60 ns) • Atmospheric Delays troposphere (20 ns) ionosphere (1 ns)
RFI mitigation using an adaptive filter Kesteven et al. (2004)
Interstellar Scintillation Figure 1, Walker & Stinebring (2005)
Arrival Time Estimation • Frequency domain (Taylor 1992) • Multi-component Gaussian (Kramer et al. 1994) • Invariant interval (Britton et al. 2000) • Full polarization (van Straten 2004) • Time vs. frequency domain (Hotan et al. 2005) • Higher order moments (Jenet & Hobbs 2005)
Full Polarization TOA • Stokes Q, U, V often sharper than Stokes I • Useful for timing? (Kramer et al. 1999)
Formalism van Straten (2004)
Simulation Position Angle of Linear Polarization: Gaussian Total Intensity Profile with Width, w Constant Degree of Polarization, p Measurement noise, n
PSR J 0437 -4715 1. 1
PSR J 1713+0747 1. 0
PSR B 1937+21 1. 4
PSR J 1022+1001 1. 6
PSR J 0437 -4715
PSR J 1713+0747
PSR B 1937+21
PSR J 1022+1001
Results Pulsar Benefit Systematic J 0437 -4715 1. 11(1) 300 ns 1713+0747 0. 99(6) 35 ns B 1937+21 1. 4(3) 30 ns 1022+1001 1. 56(8) 400 ns
Conclusion • Full Polarization TOA holds promise • Effectiveness varies by pulsar • To do: • Produce/acquire well-calibrated, high S/N polarimetric pulse profile (standards) • Run simulations • Improve arrival time estimates
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