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Extreme X-ray Behaviour of Mrk 421

ATel #4918; Bidzina Kapanadze (Ilia State Iniversity)
on 26 Mar 2013; 21:41 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, Blazar

Referred to by ATel #: 4982, 5021

In ATel #4864 (B. Kapanadze, M4k 421 Still Active through X-rays), we reported the flaring activity in the high-energy peaked BL Lacertae source Mrk 421 (z=0.031) detected via the observations performed during March 1-5, 2013, by the X-ray Telescope (XRT) onboard the Swift satellite. The recent observations, performed by this telescope, show increasing X-ray activity of this source. The data, allocated at the webpage http://www.swift.psu.edu/monitoring/ , show that the source was extremely active on hours timescale during the March 17 pointing: the 0.3-10 keV flux dropped from 16.83+\-0.17 cts/s (Orbit 1) to 12.46+\-0.24 cts/s (Orbit 5) in about 4.2 hr; it increased then to 24.60+\-0.14 cts/s for next orbit (in 1.45 hr) and afterwards drooped again to 16.01+\-0.15 cts/s in the case of next orbit (in 1.7 hr). As for the March 19 observation, the source was not active on intraday timescales with the average flux of 30.32+\-0.18 cts/s which increased to 56.26+\-0.32 cts/s during the latest observation performed by the Swift/XRT on March 23 (again without fast flux variability at 99.9% confidence level during 2.4 hr). Note that similar high level in the 0.3-10 keV flux was has not been recorded since March 12, 2010, and, therefore, we strongly encourage the intensive multiwavelength observations of Mrk 421 as with the ground-based telescopes as by means of the different space missions.