The NANOGrav Nine-Year Data Set: Noise Budget for Pulsar Arrival Times on Intraday Timescales

Lam, M. T. and Cordes, J. M. and Chatterjee, S. and Arzoumanian, Z. and Crowter, K. and Demorest, P. B. and Dolch, T. and Ellis, J. A. and Ferdman, R. D. and Fonseca, E. F. and Gonzalez, M. E. and Jones, G. and Jones, M. L. and Levin, L. and Madison, D. R. and McLaughlin, M. A. and Nice, D. J. and Pennucci, Timothy Thomas and Ransom, S. M. and Siemens, X. and Stairs, I. H. and Stovall, K. and Swiggum, J. K. and Zhu, W. W. (2016) The NANOGrav Nine-Year Data Set: Noise Budget for Pulsar Arrival Times on Intraday Timescales. ASTROPHYSICAL JOURNAL, 819 (2). ISSN 1538-4357

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Abstract

The use of pulsars as astrophysical clocks for gravitational wave (GW) experiments demands the highest possible timing precision. Pulse times of arrival (TOAs) are limited by stochastic processes that occur in the pulsar itself, along the line of sight through the interstellar medium, and in the measurement process. On timescales of seconds to hours, the TOA variance exceeds that from template-fitting errors due to additive noise. We assess contributions to the total variance from two additional effects: amplitude and phase jitter intrinsic to single pulses and changes in the interstellar impulse response from scattering. The three effects have different dependencies on time, frequency, and pulse signal-to-noise ratio. We use data on 37 pulsars from the North American Nanohertz Observatory for GWs to assess the individual contributions to the overall intraday noise budget for each pulsar. We detect jitter in 22 pulsars and estimate the average value of rms jitter in our pulsars to be similar to 1% of pulse phase. We examine how jitter evolves as a function of frequency and find evidence for evolution. Finally, we compare our measurements with previous noise parameter estimates and discuss methods to improve GW detection pipelines.

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