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Title: Comprehensive monitoring of gamma-ray bright blazars. I. Statistical study of optical, X-ray, and gamma-ray spectral slopes

We present γ-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 γ-ray bright blazars over 4 years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the Swift satellite, and augmented by data from the Fermi Gamma-ray Space Telescope and other publicly available data from Swift. The sample consists of 21 flat-spectrum radio quasars (FSRQs) and 12 BL Lac objects (BL Lacs). We identify quiescent and active states of the sources based on their γ-ray behavior. We derive γ-ray, X-ray, and optical spectral indices, α{sub γ}, α{sub X}, and α{sub o}, respectively (F{sub ν}∝ν{sup α}), and construct spectral energy distributions during quiescent and active states. We analyze the relationships between different spectral indices, blazar classes, and activity states. We find (1) significantly steeper γ-ray spectra of FSRQs than for BL Lacs during quiescent states, but a flattening of the spectra for FSRQs during active states while the BL Lacs show no significant change; (2) a small difference of α{sub X} within each class between states, with BL Lac X-ray spectra significantly steeper than in FSRQs; (3) a highly peaked distribution of X-ray spectral slopes of FSRQs at ∼ –0.60, but a very broad distributionmore » of α{sub X} of BL Lacs during active states; (4) flattening of the optical spectra of FSRQs during quiescent states, but no statistically significant change of α{sub o} of BL Lacs between states; and (5) a positive correlation between optical and γ-ray spectral slopes of BL Lacs, with similar values of the slopes. We discuss the findings with respect to the relative prominence of different components of high-energy and optical emission as the flux state changes.« less
Authors:
; ; ; ; ;  [1] ; ; ; ; ; ; ; ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6] more »; « less
  1. Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
  2. Astronomical Institute, St. Petersburg State University, Universitetskij Pr. 28, Petrodvorets, 198504 St. Petersburg (Russian Federation)
  3. Steward Observatory, University of Arizona, Tucson, AZ 85721-0065 (United States)
  4. Main (Pulkovo) Astronomical Observatory of RAS, Pulkovskoye shosse 60, 196140 St. Petersburg (Russian Federation)
  5. Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, E-18080 Granada (Spain)
  6. Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)
Publication Date:
OSTI Identifier:
22365671
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 789; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BL LACERTAE OBJECTS; DISTRIBUTION; EMISSION; ENERGY SPECTRA; GALAXIES; GAMMA RADIATION; SATELLITES; SPACE; ULTRAVIOLET RADIATION; VISIBLE RADIATION; X RADIATION; X-RAY SPECTRA