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Blazar OJ 287 after First VHE Activity: Tracking the Reemergence of the HBL-like Component in 2020

2021; IOP Publishing; Volume: 921; Issue: 1 Linguagem: Inglês

10.3847/1538-4357/ac19b8

1538-4357

Pankaj Kushwaha, Main Pal, Nibedita Kalita, Neeraj Kumari, Sachindra Naik, Alok C. Gupta, E. M. de Gouveia Dal Pino, Minfeng Gu,

Astrophysical Phenomena and Observations

Abstract We report the reemergence of a new broadband emission through a detailed and systematic study of the multiwavelength spectral and temporal behavior of OJ 287 after its first-ever reported very high energy activity in 2017 to date, which includes the second-highest X-ray flux of the source. The source shows high optical to X-ray flux variations, accompanied mainly by strong spectral changes. The optical to X-ray flux variations are correlated and simultaneous except for two durations when they are anticorrelated. The flux variations, however, are anticorrelated with the X-ray spectral state while correlated with optical–UV (ultraviolet). Weekly binned Fermi-LAT data around the duration of the highest X-ray activity show a few detections with a log-parabola model but none with a power law, yet the extracted LAT spectral energy distribution of the high-activity duration for both the models is similar and shows a hardening above 1 GeV. Further, near-infrared data indicate strong spectral change, resembling a thermal component. Overall, the combined optical to gamma-ray broadband spectrum establishes the observed variations to a new high-energy-peaked broadband emission component, similar to the one seen during the highest reported X-ray flux state of the source in 2017. The observed activities indicate some peculiar features that seem to be characteristic of this emission component, while its appearance a few years around the claimed ∼12 yr optical outbursts strongly indicates a connection between the two.