X-Ray Pulsar Period Dynamic Estimation: A Model Based on the Interlayer Phase Difference of the Fast Folding Algorithm

To further improve the accuracy and speed of real-time dynamic estimation of X-ray pulsar periods, this paper proposes a pulsar period estimation model based on the interlayer phase difference (IPD) of the fast folding algorithm (FFA) and the weighted Z² (WZ) test. This paper adopts a staged estimation strategy and divides the pulsar period estimation into a fast initial estimation stage and a local refinement search stage. First, in the fast initial estimation stage, an FFA IPD model based on the relationship among phase, time, and period is established. The interlayer phase is used to directly perform a single initial estimation of a large range of periods, thereby improving the period estimation speed. Second, in the local refinement search stage, the response coverage index is proposed for the Z² test function. The WZ test function is constructed to perform a refinement test on the local candidate period to improve the period estimation accuracy. Meanwhile, for the PSR B0531+21 source, we conducted ablation tests, analyzed influencing factors and simulation performance of the proposed method, and validated its practical application performance using Neutron Star Interior Composition Explorer observation data. We also performed generalization performance tests on other sources such as PSR B0540-69 and SMC X-1. The results show that our method has significant advantages compared to several existing estimation methods. Specifically, for the PSR B0531+21 source, compared to the integrated χ² test method, our method improves estimation accuracy by 50.21% and reduces computational time by 73.47%.