Locating the γ-ray emission region of the flat spectrum radio quasar PKS 1510−089

Brown, A.M.

Abstract

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.

Citation

Brown, A. (2013). Locating the γ-ray emission region of the flat spectrum radio quasar PKS 1510−089. Monthly Notices of the Royal Astronomical Society, 431(1), 824-835. https://doi.org/10.1093/mnras/stt218

• Journal Article Type: Article
• Publication Date: May 1, 2013
• Deposit Date: Sep 9, 2013
• Publicly Available Date: Jun 19, 2014
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 431
• Issue: 1
• Pages: 824-835
• DOI: https://doi.org/10.1093/mnras/stt218
• Keywords: Galaxies: active, Galaxies: fundamental parameters, Parameters quasars: individual: PKS 1510−089, Galaxies: jets, Galaxies: nuclei, Gamma-rays: galaxies
• Public URL: https://durham-repository.worktribe.com/output/1478453