Multiwavelength study of TeV Blazar Mrk421 during giant flare and   observations of TeV AGNs with HAGAR
  The radiation mechanism of very high energy $\gamma$-ray emission from blazars and crucial parameters like magnetic field, and size of the emitting region are not well understood yet. To understand the above mentioned properties of blazars, we observed five nearby TeV $\gamma$-ray emitting blazars (Mrk421, Mrk501, 1ES2344+514, 1ES1218+304 and 3C454.3) and one radio galaxy (M87) using the High Altitude GAmma Ray (HAGAR) telescope. HAGAR is an array of seven telescopes located at Hanle, India to detect Cherenkov light caused by extensive air showers initiated by $\gamma$-rays. Mrk421 was observed to undergo one of its brightest flaring episodes on 2010 February 17, and detected by various experiments in X-rays and $\gamma$- rays. HAGAR observations of this source during 2010 February 13 - 19, in the energies above 250 GeV show an enhancement in the flux level, with a flux of 6-7 Crab units being detected on 2010 February 17. We present the spectral energy distribution of the source during this flaring episode. In addition to this, the analysis procedure to extract $\gamma$-ray signal from HAGAR data is discussed and preliminary results on all the AGNs are presented. 
A. Shukla, P. R. Vishwanath, G. C. Anupama, T. P. Prabhu, V. R.   Chitnis, B. S. Acharya, R. J. Britto, B. B. Singh, P. Bhat...
astro-ph.HE