SIMBAD references

I present a study of the high-energy γ-ray properties of the flat spectrum radio quasar, PKS 1510-089, based on 3.75 yr of observations with the Large Area Telescope detector on-board the Fermi γ-ray Space Telescope. Throughout the observing period, the 0.1 < Eγ < 300 GeV γ-ray flux was highly variable, undergoing several flaring events where the daily flux exceeded 10-5 photons cm-2 s-1 on three separate occasions. The increased photon statistics of these large flares allowed the observations to be re-analysed in 6 and 3 h intervals, revealing flux doubling time-scales as small as 1.3±0.12 h during the flare rise time, and flux halving time-scales of 1.21±0.15 h during the flare decay. These are the smallest variability time-scales measured to date at MeV-GeV energies for the flat spectrum quasar class of active galactic nuclei.

The >10-5 photons cm-2 s-1 flare events were also studied in more detail in an attempt to uncover evidence for the location of PKS 1510-089's γ-ray emission region. In particular, two approaches were used: (i) searching for an energy dependence to the cooling time-scales, and (ii) searching for evidence of a spectral cut-off. The combined results of these two approaches, along with the confirmation of ≥ 20 GeV photon flux from PKS 1510-089, suggest the presence of multiple γ-ray emission regions being located in both the broad line region and molecular torus region of PKS 1510-089.

An analysis of the highest photon events within the 3.75 yr data set finds PKS 1510-089 to be a source of ≥ 20 GeV γ-rays at the 13.5σ confidence level; a observational property which is difficult to explain in the traditional view that γ-ray emission from active galactic nuclei originates from the base of the relativistic jet. This gives further weight to the argument that there are multiple, simultaneously active γ-ray emission regions located along the relativistic jet of active galactic nuclei.