The FSRQ PKS 1510-089: the gamma-ray-synchrotron connection

Abstract

The flat spectrum radio quasar (FSRQ) PKS 1510-089 (z=0.361) is known for its complex multiwavelength behaviour. Since 2015, it has been very active across the entire electromagnetic spectrum. This has lead to joint observation campaigns including Fermi-LAT, Cherenkov telescopes and several instrument covering the synchrotron branch. Observations resulted in a range of remarkable measurements, including rapid flares above 200 GeV with peak-fluxes exceeding the long-term average by up to a factor of 30 and unprecedented optical flares peaking in R-band at 13.6 magnitudes. The comparison of the various multi-wavelength light-curves also show that different events follow different spectral evolution within the gamma-ray band and display different relationships to the synchrotron emission. We discuss different selection effects as well as the effect of pair-absorption on flares originating at different distances from the core and conclude that absorption in the BLR is not the sole reason for the broad-band diversity. This diversity of multi-frequency correlations during different flares also reflects a diversity in physical properties of the emission regions and – possibly – even different dominating radiation mechanisms. This has implications for interpretations of orphan flares and searches for potential correlations to neutrino emission in AGN