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Beyond diagonal approximations: improved covariance modeling for pulsar timing array data analysis

arxiv.org · 14,498 words · saved by 1 readers

This is experimental HTML to improve accessibility. We invite you to report rendering errors. Use Alt+Y to toggle on accessible reporting links and Alt+Shift+Y to toggle off. Learn more about this project and help improve conversions. Pulsar Timing Array (PTA) searches for nHz gravitational-wave backgrounds (GWBs) typically model time-correlated noise by assuming a diagonal covariance in Fourier space, neglecting inter-frequency correlations introduced by the finite observation window. We show that this diagonal approximation can lead to biased estimates of spectral parameters, especially for the common red process that represents the GWB. To address these limitations, we present a method that (i) computes the time-domain autocorrelation on a coarse grid using a fast Fourier transform (FFT), (ii) interpolates it accurately to the unevenly sampled observation times, and (iii) incorporates it into a low-rank likelihood via the Sherman–Morrison–Woodbury identity. Using both analytic cova

Beyond diagonal approximations: improved covariance modeling for pulsar timing array data analysis Marco Crisostomi 1,2 mcrisost@caltech.edu Rutger van Haasteren 3 rutger@vhaasteren.com Patrick M. Meyers 1 pmeyers@caltech.edu Michele Vallisneri 4,1 mvallisneri@ethz.ch 1 TAPIR, California Institute of Technology, Pasadena, CA 91125, USA 2 Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy 3 Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Callinstraße 38, D-30167, Hannover, Germany Leibniz Universität Hannover, D-30167, Hannover, Germany 4

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