Speaker
Description
The radio-loud active galactic nuclei having the radio emission arising from a core region rather than from lobes are often referred to as "blazars" and include Flat Spectrum Radio Quasars and BL Lacertae objects. The powerful extragalactic source of radio emission 4C+51.37 is a distant flat-spectrum radio quasar at redshift z = 1.375. It has shown high activity since 2000. 4c+51.37 is a bright source of MeVGeV gamma rays and is intensively studied by the Fermi-LAT and AGILE. Spectral characteristics of 4C+51.37 at MeV-GeV energies were found to exhibit a complex shape. 4C+51.37 shows the significant flux variability in the different energy ranges, including high and very high energies. At the end of 2009, 4C+51.37 demonstrated extraordinary activity at high energy, which was detected by Fermi-LAT. The long-term observations of 4C+51.37 at 800 GeV–100 TeV energies with the SHALON telescope were started in 1998. A number of activity periods were found. The most significant flaring state of 4C+51.37 at TeV energies was detected in the SHALON observational period at the start of 2009. This increase is correlated with the flares at a lower energy range in observations of Fermi-LAT. The direct association of the significant gamma-ray flux changes with strong core radio-flares is not absolutely clear, but observed correlations and lags in multiwavelength activity point to the complexity of the emission processes in blazars connected with disturbance propagating in the jet.