A Detection of Red Noise in PSR J1824-2452A and Projections for PSR B1937+21 Using NICER X-Ray Timing Data

• Main Authors: Arzoumanian, Z. (Author), Berry, S.J.H (Author), Bogdanov, S. (Author), Crump, J. (Author), Deneva, J. (Author), Enoto, T. (Author), Gendreau, K.C (Author), Hazboun, J.S (Author), Howe, D.A (Author), Kerr, M. (Author), Lewandowska, N. (Author), Lommen, A.N (Author), Markwardt, C.B (Author), Montano, S. (Author), Parthasarathy, A. (Author), Ransom, S. (Author), Ray, P.S (Author), Teng, E. (Author), Wood, K.S (Author), Zeldes, J. (Author)
• Format: Article
• Language: English
• Published: IOP Publishing Ltd 2022
• Online Access: View Fulltext in Publisher

 We have used X-ray data from the Neutron Star Interior Composition Explorer (NICER) to search for long-timescale temporal correlations ("red noise") in the pulse times of arrival (TOAs) from the millisecond pulsars PSR J1824-2452A and PSR B1937+21. These data more closely track intrinsic noise because X-rays are unaffected by the radio-frequency-dependent propagation effects of the interstellar medium. Our search yields strong evidence (natural log Bayes factor of 9.634 ± 0.016) for red noise in PSR J1824-2452A, but the search is inconclusive for PSR B1937+21. In the interest of future X-ray missions, we devise and implement a method to simulate longer and higher-precision X-ray data sets to determine the timing baseline necessary to detect red noise. We find that the red noise in PSR B1937+21 can be reliably detected in a 5 yr mission with a TOA error of 2 μs and an observing cadence of 20 observations per month compared to the 5 μs TOA error and 11 observations per month that NICER currently achieves in PSR B1937+21. We investigate detecting red noise in PSR B1937+21 with other combinations of observing cadences and TOA errors. We also find that time-correlated red noise commensurate with an injected stochastic gravitational-wave background having an amplitude of A GWB = 2 × 10-15 and spectral index of timing residuals of γ GWB = 13/3 can be detected in a pulsar with similar TOA precision to PSR B1937+21. This is with no additional red noise in a 10 yr mission that observes the pulsar 15 times per month and has an average TOA error of 1 μs. © 2022. The Author(s). Published by the American Astronomical Society.