|Abstract : ||Blazars are a class of active galactic nuclei (AGN) that have relativistic jets, oriented close to the observer's line of sight. They dominate the extragalactic γ-ray sky. Blazars show a two-hump structure in their broad band spectral energy distribution (SED), one peaking at low energies and the other one peaking at high energies. In the leptonic model of emission from blazar jets, the low energy hump is due to synchrotron emission process of the relativistic electrons and the high energy hump is due to inverse Compton scattering off jet relativistic electrons that produce the synchrotron emission. Whereas in the hadronic model of emission from blazar jets, relativistic protons also contribute to the high energy emission through the proton synchrotron emission or photo-pion production processes.
An efficient way to constrain the leptonic v/s hadronic emission from blazar jets is through modelling of the broad band SED of blazars. However, the difficulty in accumulating near simultaneous data over a range of wavelengths and complexity of the available models in explaining the observed SED, make it a difficult approach. An alternative method to constrain the emission models in blazars is through multiband flux-monitoring observations. In my thesis, I mainly concentrated on the question ”Is leptonic model able to explain the low energy optical and high energy γ-ray flux variations and optical polarization behaviour in blazars?” I have followed the following approaches (i) correlation analysis between optical and γ-ray flux variations in blazars to constrain the leptonic scenario (ii) characterize the γ-ray variability characteristics of different categories of blazars on month like time scales and (iii) characterize the correlation between optical flux and polarization variations in blazars to constrain the connection between different emission regions in the jets of blazars. In this presentation I will discuss the findings of my thesis works.|