Untangling Optical Emissions of the Jet and Accretion Disk in the Flat-spectrum Radio Quasar 3C 273 with Reverberation Mapping Data

Abstract

3C 273 is an intensively monitored flat-spectrum radio quasar with both a beamed jet and blue bump together with broad emission lines. The coexistence of the comparably prominent jet and accretion disk leads to complicated variability properties. Recent reverberation mapping monitoring for 3C 273 revealed that the optical continuum shows a distinct long-term trend that does not have a corresponding echo in the H β fluxes. We compile multiwavelength monitoring data from the Swift archive and other ground-based programs and clearly find two components of emissions at optical wavelength. One component stems from the accretion disk itself, and the other component can be ascribed to the jet contribution, which also naturally accounts for the nonechoed trend in reverberation mapping data. We develop an approach to decouple the optical emissions from the jet and accretion disk in 3C 273 with the aid of multiwavelength monitoring data. By assuming that the disk emission has a negligible polarization in consideration of the low inclination of the jet, the results show that the jet contributes a fraction of ∼10% at the minimum and up to ∼40% at the maximum to the total optical emissions. This is the first time to provide a physical interpretation of the “detrending” manipulation conventionally adopted in reverberation mapping analysis. Our work also illustrates the importance of appropriately analyzing variability properties in cases of coexisting jets and accretion disks.