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Title: Unveiling the nature of the  $$\gamma$$-ray emitting active galactic nucleus PKS 0521-36

Journal Article · · Monthly Notices of the Royal Astronomical Society
DOI:https://doi.org/10.1093/mnras/stv909· OSTI ID:1354934
 [1];  [2];  [3];  [3];  [4];  [2];  [5];  [4];  [6];  [6];  [7];  [4];  [8];  [9]
  1. Univ. degli Studi di Bologna (Italy). Dip. Di Fisica e Astronomia; Istituto Nazionale di Astrofisica (INAF), Bologna (Italy). Istituto di Radioastronomia
  2. Istituto Nazionale di Astrofisica (INAF), Bologna (Italy). Istituto di Radioastronomia
  3. Istituto Nazionale di Astrofisica (INAF), Merate (Italy). Osservatorio Astronomico di Brera
  4. Istituto Nazionale di Astrofisica (INAF), Bologna (Italy). Istituto di Astrofisica Spaziale e Fisica Cosmica
  5. Istituto Nazionale di Astrofisica (INAF), Pino Torinese (Italy). Osservatorio Astrofisico di Torino
  6. Univ. of Michigan, Ann Arbor, MI (United States)
  7. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  8. Scuola Normale Superiore Pisa, Pisa (Italy)
  9. Univ. degli Studi di Perugia (Italy)
+ Show Author Affiliations

PKS 0521-36 is an active galactic nucleus (AGN) with uncertain classification. Here, we investigate the properties of this source from radio to γ-rays. The broad emission lines in the optical and ultraviolet bands and steep radio spectrum indicate a possible classification as an intermediate object between broad-line radio galaxies (BLRG) and steep spectrum radio quasars (SSRQ). On pc-scales PKS 0521-36 shows a knotty structure similar to misaligned AGN. The core dominance and the γ-ray properties are similar to those estimated for other SSRQ and BLRG detected in γ-rays, suggesting an intermediate viewing angle with respect to the observer. In this context the flaring activity detected from this source by Fermi-Large Area Telescope between 2010 June and 2012 February is very intriguing. We discuss the γ-ray emission of this source in the framework of the structured jet scenario, comparing the spectral energy distribution (SED) of the flaring state in 2010 June with that of a low state. We present three alternative models corresponding to three different choices of the viewing angles θv = 6°, 15°, and 20°. We obtain a good fit for the first two cases, but the SED obtained with θv = 15° if observed at a small angle does not resemble that of a typical blazar since the synchrotron emission should dominate by a large factor (~100) the inverse Compton component. This suggests that a viewing angle between 6° and 15° is preferred, with the rapid variability observed during γ-ray flares favouring a smaller angle. However, we cannot rule out that PKS 0521-36 is the misaligned counterpart of a synchrotron-dominated blazar.

Research Organization:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1354934
Journal Information:
Monthly Notices of the Royal Astronomical Society, Vol. 450, Issue 4; ISSN 0035-8711
Publisher:
Royal Astronomical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 17 works
Citation information provided by
Web of Science

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Cited By (6)

The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars journal June 2016
Gamma-ray emission in radio galaxies under the VLBI scope: I. Parsec-scale jet kinematics and high-energy properties of journal July 2019
Faint γ-ray sources at low redshift: the radio galaxy IC 1531 journal September 2018
Relativistic Jets from AGN Viewed at Highest Angular Resolution journal December 2019
Examining the High-energy Radiation Mechanisms of Knots and Hotspots in Active Galactic Nucleus Jets journal April 2018
Examining High Energy Radiation Mechanisms of Knots and Hotspots in Active Galactic Nucleus Jets text January 2018

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
gamma-rays
galaxies
galaxies nuclei
quasars
PKS 0521−36