TIME-DEPENDENT ELECTRON ACCELERATION IN BLAZAR TRANSIENTS: X-RAY TIME LAGS AND SPECTRAL FORMATION
- Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030-4444 (United States)
Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ -ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using Beppo SAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution for the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.
- OSTI ID:
- 22666158
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 824; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BL LACERTAE OBJECTS
COSMIC GAMMA SOURCES
COSMIC X-RAY SOURCES
DIFFUSION
DISTRIBUTION
ELECTRONS
FOURIER TRANSFORMATION
RADIANT HEAT TRANSFER
SHOCK WAVES
SIMULATION
SMALL ANGLE SCATTERING
SPACE
STEADY-STATE CONDITIONS
SYNCHROTRON RADIATION
TIME DEPENDENCE
TRANSPORT THEORY
X-RAY DIFFRACTION
X-RAY GALAXIES
X-RAY SPECTRA