Exploring the Nature of the Gamma-Ray Dimming in the Blazar PMN J1326-5256 since 2022 August

Abstract This study focuses on the blazar PMN J1326-5256, which experienced a drop in gamma-ray flux in 2022 August and has stayed low ever since. Based on multiwavelength observations, we analyzed the broadband spectral energy distributions (SEDs) before and after this transition. As a first step, we reproduced the broadband SEDs by the traditional one-zone leptonic model. While this model is capable of reproducing the observed data, it requires an approximately tenfold reduction in the external photon field after 2022 August compared to before, which may not be physically plausible. By contrast, the two-zone model offers a more plausible explanation: the decline in gamma-ray flux may result from the disappearance or suppression of the emission region near the central engine, allowing the far emission region to dominate the observed emission. The dynamical variation in PMN J1326-5256 is similar to that seen in PKS 1510-089, indicating a comparable jet restructuring. These findings offer valuable insights into the complex emission mechanisms and jet morphology of blazars.