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Related papers: Skewness in the Hellings-Downs curve

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The Hellings-Downs (HD) curve plays a crucial role in search for nano-hertz gravitational waves (GWs) with pulsar timing arrays. We discuss the angular pattern of correlations for pulsar pairs within a celestial hemisphere. The…

General Relativity and Quantum Cosmology · Physics 2024-07-03 Tatsuya Sasaki , Kohei Yamauchi , Shun Yamamoto , Hideki Asada

The Hellings-Downs (HD) correlation serves as the fundamental benchmark for detecting the gravitational-wave background (GWB) in pulsar timing arrays (PTAs) within General Relativity (GR). However, this canonical signature relies on the…

General Relativity and Quantum Cosmology · Physics 2026-02-17 Yan-Chen Bi , Yu-Mei Wu , Qing-Guo Huang

The Hellings-Downs (HD) correlation, which characterizes the signature of a stochastic gravitational wave background measured via Pulsar Timing Arrays (PTA), is derived using a harmonic formalism. This approach closely follows the framework…

General Relativity and Quantum Cosmology · Physics 2025-04-25 Cyril Pitrou , Giulia Cusin

Gravitational waves (GWs) create correlations in the arrival times of pulses from different pulsars. The expected correlation $\mu(\gamma)$ as a function of the angle $\gamma$ between the directions to two pulsars was calculated by Hellings…

General Relativity and Quantum Cosmology · Physics 2023-02-27 Bruce Allen

Pulsar timing-array correlation measurements offer an exciting opportunity to test the nature of gravity in the cosmologically novel nanohertz gravitational wave regime. The stochastic gravitational wave background is assumed Gaussian and…

General Relativity and Quantum Cosmology · Physics 2022-11-23 Reginald Christian Bernardo , Kin-Wang Ng

The pulsar timings are sensitive to both the nanohertz gravitational-wave background and the oscillation of ultralight dark matter. The Hellings-Downs angular correlation curve provides a criterion to search for stochastic…

General Relativity and Quantum Cosmology · Physics 2026-01-14 Rong-Gen Cai , Jing-Rui Zhang , Yun-Long Zhang

Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the correlations they create in the arrival times of pulses from different pulsars. The mean correlation, a function of the angle between the directions to two pulsars, was…

General Relativity and Quantum Cosmology · Physics 2025-01-24 Bruce Allen , Joseph D. Romano

The signals from international pulsar timing arrays have presented a hint of gravitational stochastic background in nHz band frequency. Further confirmation will be based on whether the signals follow the angular correlation curves…

General Relativity and Quantum Cosmology · Physics 2024-02-06 Qing-Hua Zhu

Pulsar timing arrays (PTAs) detect gravitational waves (GWs) via the correlations they induce in the arrival times of pulses from different pulsars. We assume that the GWs are described by a Gaussian ensemble. The mean correlation $h^2…

General Relativity and Quantum Cosmology · Physics 2023-08-25 Bruce Allen , Joseph D. Romano

Pulsar timing array (PTA) experiments have recently provided strong evidence for the signal of the stochastic gravitational wave background (SGWB) in the nHz-frequency band. These experiments have shown a statistical preference for the…

Cosmology and Nongalactic Astrophysics · Physics 2024-12-18 Rubén Arjona , Savvas Nesseris , Sachiko Kuroyanagi

An isotropic stochastic background of nanohertz gravitational waves creates excess residual power in pulsar-timing-array datasets, with characteristic inter-pulsar correlations described by the Hellings-Downs function. These correlations…

General Relativity and Quantum Cosmology · Physics 2023-05-25 Sophie Hourihane , Patrick Meyers , Aaron Johnson , Katerina Chatziioannou , Michele Vallisneri

Recent progress in gravitational wave observations has positioned Pulsar Timing Arrays as a key tool for detecting the stochastic gravitational wave background in the nanohertz band. It is widely believed that this background is primarily…

High Energy Astrophysical Phenomena · Physics 2026-05-20 Hinano Hisamatsu , Koutarou Kyutoku

The fluctuations in the cosmic microwave background radiation may contain deviations from gaussian statistics which would be reflected in a nonzero value of three-point correlation function of $\Delta T$. However, any potential observation…

Astrophysics · Physics 2009-10-22 Mark Srednicki

The Hellings and Downs correlation curve describes the correlation of the timing residuals from pairs of pulsars as a function of their angular separation on the sky and is a smoking-gun signature for the detection of an isotropic…

General Relativity and Quantum Cosmology · Physics 2024-01-22 Alex Kehagias , Antonio Riotto

The stochastic gravitational wave background for pulsar timing arrays is often modeled by a Gaussian ensemble which is isotropic and unpolarized. However, the Universe has a discrete set of polarized gravitational wave sources at specific…

General Relativity and Quantum Cosmology · Physics 2024-05-02 Bruce Allen , Serena Valtolina

Gravitational waves (GWs) induce correlated perturbations to the arrival times of pulses from an array of galactic millisecond pulsars. The expected correlations, obtained by averaging over many pairs of pulsars having the same angular…

General Relativity and Quantum Cosmology · Physics 2024-09-27 Deepali Agarwal , Joseph D. Romano

Several pulsar-timing array (PTA) collaborations are finding tantalising hints for a stochastic gravitational wave background signal in the nano-Hertz regime. So far, though, no convincing evidence for the expected Hellings-Downs…

General Relativity and Quantum Cosmology · Physics 2022-04-20 Gianmassimo Tasinato

We investigate the cross-correlation between astrometric and timing-residual observables for distant sources, such as pulsars and galaxies, and equivalent observables for nearby solar system bodies. Using the unified spin-weighted formalism…

General Relativity and Quantum Cosmology · Physics 2025-10-31 Elias Fink , Carlo Contaldi , Giorgio Mentasti

Recent pulsar timing array results, including the NANOGrav 15-year data set, show evidence for a stochastic gravitational-wave background (GWB) in the nanohertz band. We present a Bayesian framework to compare three possible origins: (i) a…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-28 Mengshen Wang , Zuocheng Zhang , Hua Xu

A gravitational-wave background can be detected in pulsar-timing-array data as Hellings--Downs correlations among the timing residuals measured for different pulsars. The optimal statistic implements this concept as a classical…

High Energy Astrophysical Phenomena · Physics 2024-02-14 Michele Vallisneri , Patrick M. Meyers , Katerina Chatziioannou , Alvin J. K. Chua
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