Discovery of a high confidence soft lag from an X-ray flare of Markarian 421
Tóm tắt
We present the X-ray variability properties of the X-ray and TeV bright blazar Mrk 421 with a ∼60 ks long XMM-Newton observation performed on November 9–10, 2005. The source experienced a pronounced flare, of which the inter-band time lags were determined with a very high confidence level. The soft (0.6–0.8 keV) X-ray variations lagged the hard (4–10 keV) ones by 1.09
−0.12
+0.11
ks, and the soft lag increases with increasing difference in the photon energy. The energy-dependent soft lags can be well fitted with the difference of the energy-dependent cooling timescales of the relativistic electron distribution responsible for the observed X-ray emission, which constrains the magnetic field strength and Doppler factor of the emitting region to be Bδ
1/3∼1.78 Gauss.
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