2024ApJ...976..124R

We investigate the evolution of a changing-look blazar (CLB) on long timescales and expect to trace the state change of a CLB. Three morphological types, including a flat spectrum radio quasar (FSRQ) state, transition state, and BL Lacertae (BL Lac) state, are classified according to the criteria proposed by analyzing the relationship between the equivalent width of the emission line and the γ-ray photon spectral index Γ_γ. The multiwavelength light curves and spectral energy distributions corresponding to different epochs are obtained. The efforts found that Γ_γ satisfy the relationships with Γ_γ ≳ 2.2 for the FSRQ state, 2.0 < Γ_γ < 2.2 for the transition state, and Γ_γ ≲ 2.0 for the BL Lac state. We apply the criteria to the photon spectrum evolution of CLB OQ 334 during MJD 58678-60387. The evolution is subdivided into five FSRQ states, nine transition states, and four BL Lac states. Moreover, we use the model spectra parameters of each state epoch to test the reliability of subdivided morphological types. The result shows that: (1) the accretion rate parameter is consistent with our earlier research; and (2) there is an increasing trend in the epochs of the BL Lac states, even if there is not an obvious decreasing trend in epochs of the FSRQ states. We issue strong evidence that a CLB is an especial epoch in the evolution of blazars that could be obtained from the oscillation phenomenon in the CLB evolution.