SUZAKU WIDE BAND ANALYSIS OF THE X-RAY VARIABILITY OF TeV BLAZAR Mrk 421 IN 2006
- Department of High Energy Astrophysics, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara 229-8510 (Japan)
- Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
- Department of Physics, Tokyo Institute of Technology, Ohokayama, Meguro, Tokyo 52-8551 (Japan)
- Institut de FIsica d'Altes Energies, 08193 Bellaterra (Spain)
- Universitaet Wuerzburg Am Hubland, 97074 Wuerzburg (Germany)
- Max-Planck-Institut fuer Physik, D-80805 Muenchen (Germany)
- Landessternwarte, Universiaet Heidelberg, Koenigstuhl, 69117 Heidelberg (Germany)
- Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570 (Japan)
We present the results of X-ray observations of the well studied TeV blazar Mrk 421 with the Suzaku satellite in 2006 April 28. During the observation, Mrk 421 was undergoing a large flare and the X-ray flux was variable, decreasing by {approx}50%, from 7.8 x 10{sup -10} to 3.7 x 10{sup -10} erg s{sup -1} cm{sup -2} in about 6 hr, followed by an increase by {approx}35%. Thanks to the broad bandpass coupled with high sensitivity of Suzaku, we measured the evolution of the spectrum over the 0.4-60 keV band in data segments as short as {approx}1 ks. The data show deviations from a simple power-law model, but also a clear spectral variability. The time-resolved spectra are fitted by a synchrotron model, where the observed spectrum is due to a exponentially cutoff power-law distribution of electrons radiating in uniform magnetic field; this model is preferred over a broken power law. As another scenario, we separate the spectrum into 'steady' and 'variable' components by subtracting the spectrum in the lowest-flux period from those of other data segments. In this context, the difference ('variable') spectra are all well described by a broken power-law model with photon index {gamma} {approx} 1.6, breaking at energy {epsilon}{sub brk} {approx_equal} 3 keV to another photon index {gamma} {approx} 2.1 above the break energy, differing from each other only by normalization, while the spectrum of the 'steady' component is best described by the synchrotron model. We suggest that the rapidly variable component is due to relatively localized shock (Fermi I) acceleration, while the slowly variable ('steady') component is due to the superposition of shocks located at larger distance along the jet, or due to other acceleration process, such as the stochastic acceleration on magnetic turbulence (Fermi II) in the more extended region.
- OSTI ID:
- 21313935
- Journal Information:
- Astrophysical Journal, Vol. 699, Issue 2; Other Information: DOI: 10.1088/0004-637X/699/2/1964; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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