The Oscillation in Evolution of Changing-look Blazar OQ 334

TL;DR

This study analyzes the long-term evolution of the changing-look blazar OQ 334, classifying its states based on spectral properties, and finds oscillation patterns that reveal insights into blazar evolution.

Contribution

It introduces a classification scheme for changing-look blazars based on gamma-ray spectral indices and demonstrates the oscillation phenomenon in OQ 334's evolution.

Findings

Gamma-ray spectral index correlates with blazar states.

Evolution shows multiple state transitions over time.

Oscillation patterns suggest episodic blazar evolution.

Abstract

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 $\gamma$-ray photon spectral index $\Gamma_{\gamma}$. The multiwavelength light curves and spectral energy distributions corresponding to different epochs are obtained. The efforts found that $\Gamma_{\gamma}$ satisfy the relationships with $\Gamma_{\gamma} $ $\gtrsim$ 2.2 for the FSRQ state, $2.0 < \Gamma_{\gamma} < 2.2$ for the transition state, and $\Gamma_{\gamma}$ $\lesssim$ 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 that 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.