Correcting for Interstellar Scattering Delay in High-precision Pulsar Timing: Simulation Results

Abstract

Light travel time changes due to gravitational waves may be detected within the next decade through precision timing of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a frequency-dependent phase change in the signal that results in pulse broadening and arrival time delays. Any method to correct the TOA for interstellar propagation effects must be based on multi-frequency measurements that can effectively separate dispersion and scattering delay terms from frequency-independent perturbations such as those due to a gravitational wave. Cyclic spectroscopy, first described in an astronomical context by Demorest (2011), is a potentially powerful tool to assist in this multi-frequency decomposition. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover impulse response functions (IRFs), such as those that would be introduced by multi-path scattering, with a realistic signal-to-noise ratio. We demonstrate that timing precision is improved when scatter-corrected TOAs are used, under the assumptions of a high signal-to-noise and highly scattered signal. We also show that the effect of pulse-to-pulse "jitter" is not a serious problem for IRF reconstruction, at least for jitter levels comparable to those observed in several bright pulsars.

11 pages, 10 figures. Accepted for publication in ApJ

References in corpus (2)

• The North American Nanohertz Observatory for Gravitational Waves
• Interstellar Holography

Cited by in corpus (13)

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• Spatial dispersion of light rays propagating through a plasma in Kerr spacetime
• The NANOGrav 12.5-Year Data Set: Monitoring Interstellar Scattering Delays
• Deconvolving Pulsar Signals with Cyclic Spectroscopy: A Systematic Evaluation
• Gravitational lensing in the presence of plasma scattering with application to Fast Radio Bursts
• A Cyclic Spectroscopy Scintillation Study of PSR B1937+21 I. Demonstration of Improved Scintillometry
• Scattering Delay Mitigation in High Accuracy Pulsar Timing: Cyclic Spectroscopy Techniques
• Noise Budget and Interstellar Medium Mitigation Advances in the NANOGrav Pulsar Timing Array