Multiband optical–IR variability of the blazar PKS 0537–441
XIAO-PAN LI LI-SHA WANG CHENG YANG HAI-YAN YANG LI ZHOU GUANG-YANG XU YU-QIONG SHAN JIE LIU YU-HUI LUO LI ZHANG
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We have reconsidered the simultaneous and homogeneous optical–IR light curves and the corresponding spectral indices curve of the blazarPKS0537–441 from January 2011 toMay2015. All the curves show significant fluctuations on various timescales, and the flux variations seem to be more pronounced towards the IR bands. The relation between average fluxes and spectral indices reveals the existence of redder-when-brighter (RWB) and bluer-when-brighter (BWB) trends at different flux levels, along with a long-term achromatic trend and a mild RWB trend on short-term timescales. Cross-correlation analyses present an energy-dependent time delay that the lower-frequency variations follow higher-frequency ones by a few weeks and a hysteresis pattern between spectra and fluxes. Our analysis reveals some potential coherence between low-energy-peaked BL Lacs (LBLs) and FSRQs, and indicates that the observed flux variability and spectral changes could be due to the superposition of a dominant jet emission, an underlying thermal contribution from a more slowly varyingdisk and/or other geometric effects under the shock-in-jet scenario.
XIAO-PAN LI1 LI-SHA WANG1 CHENG YANG2 HAI-YAN YANG1 LI ZHOU1 GUANG-YANG XU1 YU-QIONG SHAN1 JIE LIU1 YU-HUI LUO1 LI ZHANG3 4
Volume 44, 2023
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