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Title: The awakening of the γ-ray narrow-line Seyfert 1 galaxy PKS 1502+036

After a long low-activity period, we detected a γ-ray flare from the narrow-line Seyfert 1 PKS 1502+036 (z = 0.4089) by the Large Area Telescope (LAT) on board Fermi in 2015. On 2015 December 20, the source reached a daily peak flux, in the 0.1–300 GeV band, of (93 ± 19) × 10 -8 ph cm -2 s -1, attaining a flux of (237 ± 71) × 10 -8 ph cm -2 s -1 on 3-h time-scales, which corresponds to an isotropic luminosity of (7.3 ± 2.1) × 10 47 erg s -1. The γ-ray flare was not accompanied by significant spectral changes. We report on multiwavelength radio-to-γ-ray observations of PKS 1502+036 during 2008 August–2016 March by Fermi-LAT, Swift, XMM–Newton, Catalina Real-Time Transient Survey and the Owens Valley Radio Observatory (OVRO). An increase in activity was observed on 2015 December 22 by Swift in optical, UV and X-rays. The OVRO 15 GHz light curve reached the highest flux density observed from this source on 2016 January 12, indicating a delay of about three weeks between the γ-ray and 15 GHz emission peaks. Furthermore, this suggests that the γ-ray-emitting region is located beyond the broad-line region. We also compared the spectralmore » energy distribution (SED) of an average activity state with that of the flaring state. The two SED, with the high-energy bump modelled as an external Compton component with seed photons from a dust torus, could be fitted by changing the electron distribution parameters as well as the magnetic field. Furthermore, the fit of the disc emission during the average state constrains the black hole mass to values lower than 108 M⊙. The SED, high-energy emission mechanisms and γ-ray properties of the source resemble those of a flat spectrum radio quasar.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [5] ;  [6] ;  [6] ;  [7] ;  [8]
  1. Univ. of Bologna (Italy). Dept. of Physics and Astronomy; National Inst. of Astrophysics (INAF), Bologna (Italy). Inst. of Radio Astronomy
  2. National Inst. of Astrophysics (INAF), Bologna (Italy). Inst. of Radio Astronomy
  3. U.S. Naval Research Lab., Washington, DC (United States)
  4. Aalto Univ. Metsahova Radio Observatory, Kylmalal (Finland)
  5. Max Planck Inst. for Radio Astronmy, Bonn (Germany)
  6. California Inst. of Technology (CalTech), Pasadena, CA (United States). Cahill Center for Astronomy and Astrophysics
  7. Univ. of Concepcion (Chile). Dept. of Astronomy
  8. Purdue Univ., West Lafayette, IN (United States). Dept. of Physics
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 463; Journal Issue: 4; Journal ID: ISSN 0035-8711
Royal Astronomical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; galaxies: individual: PKS 1502+036; galaxies: jets; galaxies: nuclei; galaxies: Seyfert; gamma-rays: general
OSTI Identifier: