article · Publications of the Astronomical Society of the Pacific
An analysis of long-term optical and near-infrared observations of the blazar OJ 287 examines light variations across the B, V, R and J bands. The data show strong correlations between the different wavelength bands, pointing to a single origin for the observed optical and near-infrared radiation. Variations in brightness occur almost simultaneously across all bands with negligible time delays. Colour-magnitude relations show minimal changes relative to brightness, which indicates largely achromatic behaviour. While the overall variations align with random red-noise processes, periodic analysis identifies a recurring timescale of roughly 420 to 450 days. In addition, light fluctuations show higher fractional variability at longer wavelengths, alongside linear root-mean-square to flux relations. Together, these observations indicate that the emissions are produced by synchrotron processes stemming from a shared group of relativistic electrons moving within the relativistic jet.
Blazars are extreme cosmic environments powered by supermassive black holes expelling high-speed plasma jets. Studying the light variations across different wavelengths helps astronomers understand the physical mechanisms regulating these jets. Identifying consistent timescales and shared radiation sources refines models of how particle acceleration and relativistic flows function in distant active galaxies.
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Abstract The variability of blazars provides important clues to the physical processes governing relativistic jets. We present a long-term optical and near-infrared variability study of OJ 287 using archival Small and Moderate Aperture Research Telescope System observations obtained between MJD ∼ 54500 – 57100 in the B , V , R and J bands. Our results reveal strong inter-band correlations ( r = 0.79–0.98) indicating highly coherent variability and supporting a common origin for the optical and near-infrared emission. In contrast, colour–magnitude relations based on the B − V , V − R , R − J and B − J colour indices exhibit only weak correlations with source brightness (∣ r ∣ ≤ 0.32) suggesting limited spectral evolution and nearly achromatic variability. Consistent with this behaviour, flux–flux relations are strongly correlated ( r = 0.91–0.99) while piecewise-linear models generally provide better fits than single linear relations indicating changes in the flux-scaling behaviour between low and high-flux states. The Lomb–Scargle periodograms (LSPs) reveal a recurring characteristic timescale of approximately 420–450 days across the optical and near-infrared bands suggesting the presence of a possible quasi-periodic component. Discrete correlation function analysis indicates near-simultaneous variations across all bands with lags consistent with zero within the uncertainties while structure-function slopes of 0.60–0.80 are consistent with stochastic red-noise variability. The source exhibits significant variability in all bands with fractional variability amplitudes ranging from 0.74 to 0.88 and increasing systematically toward longer wavelengths. Furthermore, the approximately linear rms–flux relations observed in all four bands are consistent with a multiplicative variability mechanism operating within the jet. These results support a scenario in which the optical and near-infrared variability of OJ 287 is dominated by synchrotron emission from a common population of relativistic electrons within the jet.
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DOI: 10.1088/1538-3873/ae9b6f
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