Spectral Study and Search for Periodicity in flaring activity of GeV Blazars

Blazars are special kind of active galactic nuclei (AGNs) with jets oriented at small angles to our line of sight. The relativistic motion of plasma along the jet axis increases luminosity of the jet radiation which makes blazars one of the most rapidly varying class of objects over a broad energy band (radio to gamma-ray). PKS B1222+216 (4C +21.35; z = 0.432) is one of the brightest blazars observed in GeV energies. The temporal and spectral study of two distinct flares of PKS B1222+216 in 2014 provided detailed insight into acceleration and emission mechanisms inside the jet. The multi-wavelength data were taken from different publicly available telescopes like SPOL-CCD of Steward observatory, Swift-XRT, Swift-UVOT and Fermi-LAT. The flux-index correlation in MeV-GeV regime indicates a ‘softer when brighter’ feature. The modeling of gamma-ray light curves suggests that low energy particles initiate both the flares followed by the injection of high energy particles. The SED modeling also shows a shift in break-energy in the soft X-ray regime during the flaring activity which is the consequence of a rapid change in injection spectra.
 

The periodicity search in flaring activity was carried out using gamma-ray light curve of the GeV blazar S5 1044+71 (z = 1.15) from Fermi-LAT. The detection of a long term quasi-periodic oscillation with a period of 1090 days was confirmed by different mathematical tools like the Lomb-Scargle periodogram, Weighted Wavelet Z-transform, REDFIT, and the Monte Carlo light curve simulation. The 1090 day QPO is detected with 5 sigma significance and lasted for at least three cycles. We have also performed temporal analysis of all three cycles to explore the flaring mechanism. Also the study of performance parameters of SiPM based 4m telescope using CORSIKA simulation for inclined showers and the frequency response of camera electronics will be reported.