Multi-wavelength study of Mrk 421 TeV flare observed with \emph{TACTIC} telescope in February 2010
We present results from multi-wavelength study of intense flaring activity from a high frequency peaked BL Lac object Mrk 421. The source was observed in its flaring state on February 16, 2010 with the $TACTIC$ at energies above 1.5 TeV. Near simultaneous multi-wavelength data were obtained from high energy (MeV-GeV) $γ$--ray observations with \emph{Fermi}--LAT, X--ray observations by the \emph{Swift} and \emph{MAXI} satellites, optical V-band observation by SPOL at \emph{Steward Observatory} and radio 15 GHz observation at OVRO 40 meter-telescope. We have performed a detailed spectral and temporal analysis of $TACTIC$, \emph{Fermi}--LAT and \emph{Swift}--XRT observations of Mrk 421 during February 10--23, 2010 (MJD 55237-55250). The flaring activity of the source is studied by investigating the properties of daily light curves from radio to $TeV$ energy range and we present the correlation and variability analysis in each energy band. The $TeV$ flare detected by $TACTIC$ on February 16, 2010 is well correlated with the activity in lower energy bands. The differential energy spectrum of the source, in the energy range 1.5-11 TeV, as measured by $TACTIC$ on this night is described by a power law ($dN/dE \propto E^{-Γ}$) with spectral index $Γ= 2.6\pm0.3$. After accounting for absorption of $TeV$ photons by low energy extragalactic background light photons via pair production, the intrinsic $TeV$ spectrum reveals a power law index of $2.3\pm0.3$. Finally the broad band spectral energy distribution of the source in flaring state is reproduced using a simple emission model involving synchrotron and synchrotron self Compton processes. The obtained parameters are then used to understand the energetics of the source during the flaring episode.