Pulsar Timing Phenomenology

1. Pulsar Timing Phenomenology … an overview…. George Hobbs Australia Telescope National Facility

2. Sorry for being late!

3. Introduction • Timing residuals for ‘normal’ pulsars (based on Jodrell Bank Observatory data) • Timing residuals for millisecond pulsars (based on Parkes/Arecibo/GB/Nancay data) • Summary: • Timing noise is wide-spread in pulsars • Timing noise in millisecond pulsars is similar in structure to that seen in young pulsars • The predicted amplitude of timing noise in some millisecond pulsars is low and provides hope for the detection of GWs

4. Pulsar timing: The basics Model for pulsar spin down Improve timing model Obtain pulse arrival times at observatory Form timing residuals – how good is the timing model at predicting the arrival times

5. Pulsar post-fit timing residuals Fit for rotational period and its derivative (quadratic term)

6. PSR B1900+06

7. PSR B1828-11 Timing noise explained as free-precession due to periodicities and correlated pulse shape changes

8. Characterising the residuals (mag. dipole rad.) ‘n’ ranges between –2.6 x 108 and 2.5 x 108 46% of F2 measurements are negative • Strong correlation between amplitude of “timing noise” and first and second derivative of rotational frequency (also age) • No correlation found so far with timescale of timing noise and any pulsar parameter. • On average the timing residuals show sharper local maxima than local minima 30yr

9. Evolution of the characterisation 1 year 5 year 6 year 11 year 35 year

10. Red noise simulations

11. Disproven theories of timing noise • Off-line software • Observatories/receiver systems … • Frequency-dependent noise • Timing noise is not correlated with “height above the Galactic plane, luminosity or pulse shape changes” – Cordes & Helfand (1980)

12. The cause of these structures in the timing residuals • Unmodelled binary companions • Clouds of particles • Post-Newtonian orbital effects • Free-precession of the neutron star • Vortex creep • Accretion onto surface • Magnetospheric effects • Irregularities in terrestrial time standards • Inaccuracies in planetary ephemeris • Effects of gravitational waves

13. How do you tell? • Expect (pseudo)-sinusoidal features for orbital/precessional effects • Expect glitch-like phenomena in vortex creep models • Expect particular power-spectrum for magnetospheric/phase noise/slowing-down noise • Expect particular correlations between pulsars for GWs/time or solar system inaccuracies • Theory provides expected amplitudes and time-scales

14. Timing noise in the millisecond pulsars

15. PSRs B1855+09 and B1937+21 Jodrell versus Arecibo residuals for B1937+21

16. Microglitch in B1821-24 (M24) • Cognard, Backer (2004)

17. PSR B1744-24A (Nice, Arzoumanian, Thorsett), Terzan 5 Discussed possibilities: Timing noise intrinsic to the pulsar (but many times larger than other millisecond pulsars) Changes in the viewing geometry of the emission region (precession) A “lumpy” disk around the binary system (precursor to planet formation) Torques on the pulsar due to infalling matter

18. J0437-4715 and 35ns result van Straten (2001), Nature: arrival times averaged in 40 phase bins – rms residual of 35 ns Current result: 450ns with 5 minute integrations

19. Some systematic effect at ~100ns Instrumental effects? Pulsar instabilities? 0437-4715 1909-3715 thesis, Splaver (2004) - arecibo Hotan: Parkes observations

20. PSR J1909-3715 • 5 minute integrations, rms = 200 ns, 5 minute integrations

21. Predicted amplitudes for the recycled pulsars only Jodrell data 3yr spans Backer (2005) – Aspen meeting 8 yr spans where the spin frequency and its second derivative are measured over a 108 s interval.

22. Thanks to K.J. Lee sigmaz at 10yr

23. Conclusion • Timing irregularities seen in both normal and millisecond pulsars • “Amount” of timing noise correlated with Pdot (and age) • Jodrell Bank observatory contains an archive of ~400 pulsars with data spanning up to 35 years • Many theories of timing noise … how can we disprove some of these models?