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2010 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 710, no 2, 1271-1285 p.Article in journal (Refereed) Published
Abstract [en]

The gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample LBAS) are investigated using Fermi-LAT data. Spectral properties hardness, curvature, and variability) established using a data set accumulated over 6 months of operation are presented and discussed for different blazar classes and subclasses: flat spectrum radio quasars (FSRQs), low-synchrotron peaked BLLacs (LSP-BLLacs), intermediate-synchrotron peaked BLLacs (ISP-BLLacs), and high-synchrotron peaked BLLacs (HSP-BLLacs). The distribution of photon index G, obtained from a power-law fit above 100 MeV) is found to correlate strongly with blazar subclass. The change in spectral index from that averaged over the 6 months observing period is < 0.2-0.3 when the flux varies by about an order of magnitude, with a tendency toward harder spectra when the flux is brighter for FSRQs and LSP-BLLacs. A strong departure from a single power-law spectrum appears to be a common feature for FSRQs. This feature is also present for some high-luminosity LSP-BLLacs, and a small number of ISP-BLLacs. It is absent in all LBAS HSP-BLLacs. For 3C 454.3 and AO 0235+164, the two brightest FSRQ source and LSP-BLLac source, respectively, a broken power law (BPL) gives the most acceptable of power law, BPL, and curved forms. The consequences of these findings are discussed.

Place, publisher, year, edition, pages
2010. Vol. 710, no 2, 1271-1285 p.
Keyword [en]
BL Lacertae objects: general, galaxies: active, galaxies: jets, gamma rays: general
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-48955DOI: 10.1088/0004-637X/710/2/1271ISI: 000274233300027OAI: diva2:376126
authorCount :177Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2010-12-10Bibliographically approved

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Axelsson, MagnusConrad, Jan
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Department of AstronomyDepartment of Physics
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