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The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars


Krauss, F and Wilms, J and Kadler, M and Ojha, R and Schulz, R and Truestedt, J and Edwards, PG and Stevens, J and Ros, E and Baumgartner, W and Beuchert, T and Blanchard, J and Buson, S and Carpenter, B and Dauser, T and Falkner, S and Gehrels, N and Graefe, C and Gulyaev, S and Hase, H and Horiuchi, S and Kreikenbohm, A and Kreykenbohm, I and Langejahn, M and Leiter, K and Lovell, JEJ and Mueller, C and Natusch, T and Nesci, R and Pursimo, T and Phillips, C and Ploetz, C and Quick, J and Tzioumis, AK and Weston, S, The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars, Astronomy & Astrophysics, 591 Article A130. ISSN 1432-0746 (2016) [Refereed Article]


Copyright Statement

Copyright ESO 2016

DOI: doi:10.1051/0004-6361/201628595


Context: Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics.

Aims: We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multiepoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies.

Methods: We use a Bayesian block analysis of Fermi/LAT light curves to determine time ranges of constant flux for constructing quasi-simultaneous spectral energy distributions (SEDs). The shapes of the resulting 81 SEDs are described by two logarithmic parabolas and a blackbody spectrum where needed.

Results: The peak frequencies and luminosities agree well with the blazar sequence for low states with higher luminosity implying lower peak frequencies. This is not true for sources in high states. The γ-ray photon index in Fermi/LAT correlates with the synchrotron peak frequency in low and intermediate states. No correlation is present in high states. The black hole mass cannot be determined from the SEDs. Surprisingly, the thermal excess often found in FSRQs at optical/UV wavelengths can be described by blackbody emission and not an accretion disk spectrum.

Conclusions: The so-called harder-when-brighter trend, typically seen in X-ray spectra of flaring blazars, is visible in the blazar sequence. Our results for low and intermediate states, as well as the Compton dominance, are in agreement with previous results. Black hole mass estimates using recently published parameters are in agreement with some of the more direct measurements. For two sources, estimates disagree by more than four orders of magnitude, possibly owing to boosting effects. The shapes of the thermal excess seen predominantly in flat spectrum radio quasars are inconsistent with a direct accretion disk origin.

Item Details

Item Type:Refereed Article
Keywords:galaxies: active; BL Lacertae objects: general; quasars: general; relativistic processes
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:High energy astrophysics and galactic cosmic rays
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Lovell, JEJ (Dr Jim Lovell)
ID Code:115228
Year Published:2016
Web of Science® Times Cited:15
Deposited By:Mathematics and Physics
Deposited On:2017-03-10
Last Modified:2017-11-03
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