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Paper: High-energy Variability of Blazars
Volume: 350, Blazar Variability Workshop II: Entering the GLAST Era
Page: 86
Authors: Sambruna, R.M.
Abstract: High-energy X-ray emission from blazars probes the site(s) in the relativistic jet with the most energetic particles and fields. X-ray variability, and correlated X-ray and gamma-ray TeV variability, is an important tool to investigate the structure of the pc-scale jet and to discriminate among models for the production of the emission at the highest energies. Here, I summarize two recent studies of blazars at X-rays. The first is a study of the broad-band (0.3–100 keV) spectra of a sample of blazars using BeppoSAX (Donato, Sambruna, & Gliozzi 2005). We find a dispersion of X-ray photon index among blazar classes, with FSRQs having flatter indices (Γ ∼ 1.6) than HBLs (Γ ∼ 2.2), while LBLs are intermediate (Γ ∼ 1.9), confirming previous findings. This is in agreement with the blazar spectral luminosity sequence. The second study is an investigation of the long-term X-ray and TeV variability of Mrk 501 using archival and proprietary RXTE, HEGRA, and Whipple observations (Gliozzi et al. 2005). The results are: 1) At X-rays, the harder energies vary with larger amplitudes than at softer energies; 2) Long-term ( day-month-year) correlation between X-ray and TeV variability is confirmed; 3) The TeV-X-ray flux correlation is both linear and quadratic. Interestingly, a possible “childless” X-ray flare, with no TeV counterpart, is observed at one epoch.
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