Searching for new very high energy emitting AGN among the unclassifed and unassociated Fermi-LAT sources

English: Jet dominated Active Galactic Nuclei (AGN) are the most energetic persistent sources of emission in the universe, emitting radiation across the entire electromagnetic spectrum. When these jets are pointed towards the observer, they become known as blazars. Blazar emission is dominated by the beamed non-thermal emission from the relativistic jet and are the brightest sources in the extragalactic sky. Blazars, sub-categorized into BL Lacertae objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs) exhibit variability at all wavelengths on diverse timescales, high polarization and weak or featureless optical spectra. These extreme sources provide a laboratory to test some of the most energetic physical processes in the known universe. In order to study the processes responsible for the highest energy emission originating from blazar jets, more Very High Energy (VHE) emitting blazars must be found and studied with Imaging Air Cherenkov Telescopes (IACTs). The small sample of currently known VHE emitting blazars, studied for many years, has not yet provided a complete understanding of blazar physics. A study to monitor 17 VHE blazars detected by the High Energy Stereoscopic System (H.E.S.S.) with the Watcher Robotic Telescope has been underway since May 2015. A fast reduction and analysis pipeline, written in python and using PyRAF to interface with IRAF, was developed to perform aperture photometry on 14 of these sources and search for long-term variability (LTV). In addition, to search for new VHE emitting blazars observable with IACTs, a sample of 11 Blazar Candidates of Uncertain Type (BCUs) listed in the Third Fermi Large Area Telescope Source Catalog (3FGL), 11 BCUs and an unassociated source listed in the Third Catalogue of Hard Large Area Telescope sources (3FHL), selected based on hard -ray spectra and lack of redshift measurements were identi ed for spectroscopic follow-up with the aim of classifying them. The selected sources were observed with the SpUpNIC grating spectrograph mounted on the SAAO 1.9-m telescope. A selection of 6 3FHL sources identi ed for spectroscopic study were also observed with the Sutherland Highspeed Optical Camera (SHOC) mounted on the SAAO 1.0-m telescope to search for intra-day variability (IDV). All 22 of the BCUs were classi ed as BL Lac objects based on the absence of strong emission lines and a diluted Ca break (less than 40%). Further, redshifts were calculated for 11 BCUs and potential redshifts for 4 BCUs. Further searches for photometry variability were undertaken for all sources. Spectral Energy Distributions (SEDs) were constructed to determine which of the observed BCUs were good candidates to be observed with IACTs. The 50h H.E.S.S. and Cherenkov Telescope Array (CTA) South sensitivity curves were overlayed on the SEDs. Of the BCUs observed, 8 of the sources have -ray emission above the CTA detection threshold and are good candidates for VHE observation.