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TACTIC detection of a strong TeV flare from Mrk 421

ATel #11199; R C Rannot for TACTIC collaboration
on 18 Jan 2018; 18:06 UT
Credential Certification: Ramesh Chand Rannot (rcrannot@barc.gov.in)

Subjects: Gamma Ray, TeV, AGN, Blazar

TACTIC telescope has detected an enhanced gamma-ray flux from Mrk 421 on the night of January 17, 2018. Preliminary analysis of the data collected for ~5.6 hours indicates that the average flux during the night ; MJD 58135.7822 - 58136.0273 was around 5 times the flux of Crab nebula above 850 GeV. The telescope has also detected the source on hourly basis at a significance level of ~5 sigma with a peak flux of ~7.7 times the Crab nebula flux during MJD 58135.9375 -58135.9792. We have been regularly monitoring this source since December 21, 2017 and plan to continue. So far this is the highest gamma-ray flux recorded using TACTIC from Mrk 421. Multi- wavelength observations of this enhanced activity of the source have also been reported by FACT ( ATels: #11184), HAWC ( ATel: #11194), MAXI/GSC ( ATel: #11186) & Swift/BAT ( ATel: #11195). The TACTIC ( TeV Atmospheric Cherenkov Telescope with Imaging Camera) is an Imaging Atmospheric Cherenkov Telescope located at Mount Abu, India monitoring the gamma- ray sky at TeV energies.