Volume 591, July 2016
|Number of page(s)||26|
|Published online||28 June 2016|
The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars⋆
1 Dr. Remeis Sternwarte & ECAP, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany
2 Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, 97074 Würzburg, Germany
3 NASA, Goddard Space Flight Center, Greenbelt, MD 20771, USA
4 University of Maryland, Baltimore County, Baltimore, MD 21250, USA
5 Catholic University of America, Washington, DC 20064, USA
6 ASTRON, the Netherlands Institute for Radio Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
7 CSIRO Astronomy and Space Science, ATNF, PO Box 76, Epping, NSW 1710, Australia
8 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
9 Departament d’Astronomia i Astrofísica, Universitat de València, C/ Dr. Moliner 50, 46100 Burjassot, València, Spain
10 Observatori Astronòmic, Universitat de València, C/ Catedrático José Beltrán no. 2, 46980 Paterna, València, Spain
11 Departamento de Astronomía, Universidad de Concepción, Casilla 160, Chile
12 Institute for Radio Astronomy and Space Research, Auckland University of Technology, Auckland 1010, New Zealand
13 Bundesamt für Kartographie und Geodäsie, 93444 Bad Kötzting, Germany
14 CSIRO Astronomy and Space Science, Canberra Deep Space Communications Complex, PO Box 1035, Tuggeranong, ACT 2901, Australia
15 School of Mathematics & Physics, University of Tasmania, Private Bag 37, Hobart, 7001 Tasmania , Australia
16 Department ofAstrophysics/IMAPP, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
17 INAF–IAPS, via Fosso del Cavaliere 100, 00033 Rome, Italy
18 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
19 Hartebeesthoek Radio Astronomy Observatory, Krugersdorp, South Africa
Received: 25 March 2016
Accepted: 3 May 2016
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.
Key words: galaxies: active / BL Lacertae objects: general / quasars: general / relativistic processes
Tables of the fluxes are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A130
© ESO, 2016
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