Searching for the nano-Hertz stochastic gravitational wave background with the Chinese Pulsar Timing Array Data Release I

Kavli Affiliate: Kejia Lee

| First 5 Authors: Heng Xu, Siyuan Chen, Yanjun Guo, Jinchen Jiang, Bojun Wang

| Summary:

Observing and timing a group of millisecond pulsars (MSPs) with high
rotational stability enables the direct detection of gravitational waves (GWs).
The GW signals can be identified from the spatial correlations encoded in the
times-of-arrival of widely spaced pulsar-pairs. The Chinese Pulsar Timing Array
(CPTA) is a collaboration aiming at the direct GW detection with observations
carried out using Chinese radio telescopes. This short article serves as a
`table of contents’ for a forthcoming series of papers related to the CPTA Data
Release 1 (CPTA DR1) which uses observations from the Five-hundred-meter
Aperture Spherical radio Telescope (FAST). Here, after summarizing the time
span and accuracy of CPTA DR1, we report the key results of our statistical
inference finding a correlated signal with amplitude $log A_{rm c}= -14.4
,^{+1.0}_{-2.8}$ for spectral index in the range of $alphain [-1.8, 1.5]$
assuming a GW background (GWB) induced quadrupolar correlation. The search for
the Hellings-Downs (HD) correlation curve is also presented, where some
evidence for the HD correlation has been found that a 4.6-$sigma$ statistical
significance is achieved using the discrete frequency method around the
frequency of 14 nHz. We expect that the future International Pulsar Timing
Array data analysis and the next CPTA data release will be more sensitive to
the nHz GWB, which could verify the current results.

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