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Swift/BAT reports new flaring activity from Mrk 421

ATEL # 2292; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), D. Palmer (LANL), T. Sakamoto (CRESTT/GSFC/UMBC), G. Skinner (CRESST/GSFC/UMD), M. Stamatikos (OSU/GSFC), J. Tueller (GSFC), T. Ukwatta (GSFC/GWU)
on 11 Nov 2009; 18:20 UT
Password Certification: Hans A. Krimm (

Subjects: X-ray, AGN

As part of its hard X-ray transient monitor program, the Burst Alert Telescope on Swift has detected a brightening of the blazar Markarian 421. The source began brightening around 11-Oct-2009 (MJD 55115) when it had an average daily rate of 0.0036 0.0007 counts/s/cm^2, corresponding to ~15 mCrab in the 15-50 keV band. Over the past two days, it has brightened more rapidly, and is up to 0.019 0.005 counts/s/cm^2 (~85 mCrab) on 10-Nov-2009 (MJD 55145). This activity suggests that Mrk 421 is in a flaring state, with intensities similar to recent outbursts in March 2008 (Krimm et al, ATel #1449) and June 2006 (Lichti et al, ATel #840 #848). Normally Mrk 421 is barely detectable in the BAT one-day averages at 6 mcrab.

Examination of the RXTE All-Sky Monitor light curves also show an increase in the 2-10 keV band beginning around the same time. The count rate was up to 3.4 0.4 counts/sec on MJD 55140.

Swift/BAT Hard X-ray Transient light curve for Mrk 421

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R. E. Rutledge , Editor
ATEL Mirror v1.0 Updates