After giving a brief overview of the work we are involved at at the Physical Resrach Laboratory – study of inner Milky way and dust grain properties of cometary comae – I will give a brief idea of the work we are doing for the study of energy mechanism of Blazars.

Active Galactic Nuclei (AGNs) are enigmatic objects producing very high luminosities in a very compact region. BL Lac objects and flat spectrum radio quasars (FSRQ) are AGNs commonly unified in the class of Blazars. The members of this subclass are characterized by non-thermal continuum, a high degree of linear polarization, rapid variability in flux and polarization. Their spectral energy distribution is characterized by two humps – the low energy peaked one is understood to be due to non-thermal radiation from relativistic electrons, while the high energy peaked one is not well understood. The mechanism responsible for the very high energy emission is not known. There are several models but simultaneous multiwavelngth observations are required for this purpose. We have been monitoring a sample of blazars and some of the results will be discussed.