Pulsar Timing Phenomenology … an overview…. George Hobbs Australia Telescope National Facility.
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Transcript of Pulsar Timing Phenomenology … an overview…. George Hobbs Australia Telescope National Facility.
Pulsar Timing Phenomenology
… an overview….
George HobbsAustralia Telescope National Facility
Sorry for being late!
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
Pulsar timing: The basics
Obtain pulse arrival times at observatory
Model for pulsar spin down
Form timing residuals – how good is the timing model at predicting the arrival times
Improve timing model
Pulsar post-fit timing residuals
Fit for rotational period and its derivative (quadratic term)
PSR B1900+06
PSR B1828-11
Timing noise explained as free-precession due to periodicities and correlated pulse shape changes
Characterising the residuals (mag. dipole rad.)
‘n’ ranges between –2.6 x 108 and 2.5 x 108
46% of F2 measurements are negative
23v
vvn
•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
Evolution of the characterisation
1 year 5 year
6 year11 year
35 year
Red noise simulations
AfP
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)
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
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
Timing noise in the millisecond pulsars
PSRs B1855+09 and B1937+21
Jodrell versus Arecibo residuals for B1937+21
Microglitch in B1821-24 (M24)
• Cognard, Backer (2004)
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
J0437-4715 and 35ns resultvan Straten (2001), Nature: arrival times averaged in 40 phase bins – rms residual of 35 ns
Current result: 450ns with 5 minute integrations
thesis, Splaver (2004) - areciboHotan: Parkes observations
Some systematic effect at ~100ns
Pulsar instabilities?Instrumental effects?
0437-4715
1909-3715
PSR J1909-3715• 5 minute integrations, rms = 200 ns, 5 minute integrations
Predicted amplitudes for the recycled pulsars
Backer (2005) – Aspen meeting
only Jodrell data
3yr spans
8 yr spans
3
108 ||6
1log t
where the spin frequency and its second derivative are measured over a 108 s interval.
0374.0056.010 94.2~ PPyrz
sigmaz at 10yrThanks to K.J. Lee
72 10hg
82 10hg
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?