2025ApJ...983...63H

In this paper, we present the linear decomposition method (LDM), which we developed to detect and analyze pulsar profile variations and mode-changing behavior. We developed LDM utilizing the likelihood function approach assuming the Gaussian noise. The LDM projects pulse profiles onto significance-ordered orthonormal vector bases. We show that the method is similar to the principal component analysis, but the LDM can handle more general situations. We use a simulated data set and data from the Kunming 40 m radio telescope to demonstrate the application of the LDM. We found that the LDM successfully identified mode changes for well-known mode-changing PSR B0329+54 and found a continuous pulse profile evolution for PSR B0355+54. We also show that the LDM can be used to improve the timing precision for mode-changing PSR B0329+54.