Unveiling the Emission Mechanisms of Blazar PKS 1510-089. I. Multiwavelength Variability

Abstract

The flat spectrum radio quasar PKS 1510-089 is one of the most active blazars in γ -rays, exhibiting phases of very high activity. This study investigates its variability over a decade across a wide range of wavelengths, from radio to γ -rays. Utilizing the nonthermal dominance parameter, we analyze the H β , H γ , and λ 5100 Å continuum light curves to discern the primary source of continuum emission, either from the accretion disk or the jet, during different activity phases. Our findings underscore the dominance of jet emission in the continuum during flare-like events. We observed an approximately 80 day delay between the H β and continuum emissions, which we attribute to the spatial separation between the optical emission zone and the broad-line region. Near-zero delays between optical and near-infrared emissions suggest that the emitting regions within the jet are cospatial. Synchrotron self-Compton was identified as the primary mechanism for γ -ray emission during flares, supported by the minimal delay observed between optical/near-infrared emissions and γ -rays. Additionally, we found a delay of about 60 days between the leading optical/near-infrared emissions and X-rays, indicating that inverse Compton scattering within the jet predominantly drives X-ray emission. However, distinguishing between synchrotron self-Compton and external inverse Compton mechanism was not feasible. Shifts in the spectral index across the 15–230 GHz range corresponded with ejections from the radio core, suggesting changes in the physical conditions of the jet.

Keywords

• Active galaxies
• Galaxy jets
• Gamma-rays
• Emission line galaxies
• Flat-spectrum radio quasars
• Supermassive black holes