2007A&A...462...29G -
Astronomy and Astrophysics, volume 462, 29-41 (2007/1-4)
Unveiling the X-ray/TeV engine in Mkn 421.
GIEBELS B., DUBUS G. and KHELIFI B.
Abstract (from CDS):
Our goal was to find important clues concerning particle acceleration in relativistic jets through the analysis of multi-wavelength observations of TeV blazars. Simultaneous observations of Mkn 421 were taken in very high energy γ-rays (>200GeV, CAT experiment), X-rays (RXTE), and optical (KVA). Multi-day RXTE observations are also presented, allowing for detailed modelling of the spectral variability. Short timescale (≃30mn) variations in VHE γ-rays are found, correlated with X-rays, but not with the optical. The X-ray spectrum hardens with flux until the photon indices saturate above a threshold flux ≃10–9erg/s/cm2. The fractional variability decreases from X-rays to optical as a power law with Fvar∝E0.24±0.01. The full spectral energy distribution is well-fitted by synchrotron self-Compton emission from cooling electrons injected with a Maxwellian distribution of characteristic energy γb. Fluctuations in the injected power with Pinj∝γb4 explain the observed variability. The spectral saturation and the power-law dependence of the fractional variability are novel results that may extend to other TeV blazars. The ability of Maxwellian injections to reproduce the observed features suggest second-order Fermi acceleration or magnetic reconnection may play the dominant role in particle acceleration.
Abstract Copyright:
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Journal keyword(s):
acceleration of particles - radiation mechanisms: non-thermal - galaxies: active - BL Lacertae objects: individual: Mkn 421 - gamma rays: observations - X-rays: galaxies
Simbad objects:
6
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