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High Enerygy Outburst in BL Lac object Mkn 421

ATel #65; R. Remillard (MIT), H. G. Boerst (University of Kiel), N. Goetting (University of Hamburg)
on 23 Jan 2001; 00:16 UT
Credential Certification: Ron Remillard (rr@space.mit.edu)

Subjects: X-ray, >GeV, AGN

Following the detection of enhanced X-ray emission from the BL Lac object Markarian 421 with the RXTE All Sky Monitor on, observations with the Cherenkov telescopes of HEGRA (La Palma, Canary Islands, Spain) show very strong TeV activity. Above a threshold energy of 500 GeV, daily integrated fluxes (20 minute averages) reach up to 1, 4, 2, 1.5, 2.5, and 3 times the TeV flux of the Crab Nebula in consecutive nights during January 16-22. The ASM observations of Mkn 421 in mCrab at 2-12 keV: 44(2) over UT 2001 January 13-18; 30(3) Jan 19-20; 54(3) on Jan 21, and 80(6) on Jan 22. Today's peak is the brightest X-ray flux seen from a BL Lac object during the RXTE Mission (since Jan 1996). Observations at other wavelengths are strongly encouraged.