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Title: Spectral properties of bright Fermi-detected blazars in the gamma-ray band

Abstract

We investigated the gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample (LBAS) 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). Furthermore, the distribution of photon index (Γ, 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. Finally, we present this feature 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 consequencesmore » of these findings are discussed.« less

Authors:
 [1]
  1. Naval Research Lab. (NRL), Washington, DC (United States); National Academy of Sciences, Washington, DC (United States); et al.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
Fermi LAT Collaboration
OSTI Identifier:
1357578
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal
Additional Journal Information:
Journal Volume: 710; Journal Issue: 2; Journal ID: ISSN 0004-637X
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; BL Lacertae objects: general; galaxies: active; galaxies: jets; gamma rays: general

Citation Formats

Abdo, A. A. Spectral properties of bright Fermi-detected blazars in the gamma-ray band. United States: N. p., 2010. Web. doi:10.1088/0004-637X/710/2/1271.
Abdo, A. A. Spectral properties of bright Fermi-detected blazars in the gamma-ray band. United States. https://doi.org/10.1088/0004-637X/710/2/1271
Abdo, A. A. Thu . "Spectral properties of bright Fermi-detected blazars in the gamma-ray band". United States. https://doi.org/10.1088/0004-637X/710/2/1271. https://www.osti.gov/servlets/purl/1357578.
@article{osti_1357578,
title = {Spectral properties of bright Fermi-detected blazars in the gamma-ray band},
author = {Abdo, A. A.},
abstractNote = {We investigated the gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample (LBAS) 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). Furthermore, the distribution of photon index (Γ, 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. Finally, we present this feature 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.},
doi = {10.1088/0004-637X/710/2/1271},
journal = {The Astrophysical Journal},
number = 2,
volume = 710,
place = {United States},
year = {2010},
month = {1}
}

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