Active Galactic Nuclei (AGNs)areexceptionally luminous compared with normal galaxies in all parts of the electromagnetic spectrum. The radiation from AGN is believed to be a result of accretionof matter by the super-massive black holeat the center of the host galaxy. They are the most luminous persistent sources of electromagnetic radiation in the universe. Being distant objects, AGNs can be used as means of studying distant the universe.
Blazars constitute a subclass of AGNs, with jet axes oriented close to the observer’s line of sight. Relativistic beaming gives rise to distinctive observational features in blazars, such as strongly anisotropic radiation, super-luminal motion, high polarization and rapid variability. Blazars are divided into two subclasses, flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs). FSRQs are observationally characterized by broad spectral lines in the optical band, while such lines are weak or not present in BL Lacs.
Blazars constitute a subclass of AGNs, with jet axes oriented close to the observer’s line of sight. Relativistic beaming gives rise to distinctive observational features in blazars, such as strongly anisotropic radiation, super-luminal motion, high polarization and rapid variability. Blazars are divided into two subclasses, flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs). FSRQs are observationally characterized by broad spectral lines in the optical band, while such lines are weak or not present in BL Lacs.
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