Exploring the Transitional Parameter Space of Blazars using Gamma-ray and X-ray Population Diagnostics

TL;DR

This study analyzes the gamma-ray and X-ray properties of changing-look blazars, revealing they are transitional objects with characteristics closer to FSRQs, using population diagnostics and machine learning techniques.

Contribution

It provides a comprehensive multi-wavelength population analysis of changing-look blazars, highlighting their transitional nature between BL Lacs and FSRQs.

Findings

CLBs occupy intermediate regions in gamma-ray parameter space.

CLBs are closer to FSRQs in spectral and variability properties.

X-ray analysis confirms CLBs' proximity to FSRQ characteristics.

Abstract

We investigate the $\gamma$-ray and X-ray population properties of changing-look blazars (CLBs) using sources from the Fourth \textit{Fermi} LAT Source Catalog Data Release 4 (4FGL-DR4) together with X-ray information from the Living \textit{Swift} XRT Point Source (LSXPS) catalog. The CLB sample is compared with large populations of confirmed BL Lac objects (BLLs) and flat-spectrum radio quasars (FSRQs) using spectral, variability, and broadband properties. In the $\gamma$-ray parameter space, CLBs mainly occupy intermediate and overlap regions between the BLL and FSRQ populations. However, the centroid locations in different parameter planes, along with the PCA and UMAP projections, show that the CLB population lies closer to the FSRQ region. The X-ray analysis also shows a similar behavior, where the overall distribution of CLBs in the X-ray parameter space is found to be nearer to FSRQs than to BLLs. In addition, the X-ray/$\gamma$-ray coupling relations and random-forest classification probabilities are consistent with this trend. Overall, the results suggest that CLBs form a transitional population between the two main blazar subclasses while retaining characteristics closer to the FSRQ population.