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Paper: Synchrotron Cooling Model of X-ray Variability in BL Lac Objects
Volume: 159, BL Lac Phenomenon
Page: 190
Authors: Makino, Fumiyoshi
Abstract: X-ray spectra of BL Lac objects are classified into two categories, flat spectrum with index of about 1.7 and steep spectrum with index of about 2.5. The steep spectrum can be connected smoothly from radio to X-ray, while the flat spectrum is discontinuous to the spectrum in UV and optical. Typical sources of steep spectrum are PKS 2155-304 and Mkn 421. X-ray variation of these sources characterized by correlation between flux and spectral index and soft lag. The spectrum becomes steeper with decreasing flux and variation of flux in lower energy delays from that in higher energy. It will be shown that these properties are quantitatively reproduced by synchrotron cooling model by solving time dependent diffusion equation of electrons for various injection function. The magnetic field strength can be derived from the lag. The solution could be useful for observational study of acceleration of the elcrons in BL Lac objects.
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