School of Physics CRA Seminar:  Dr. Manel Errando, Barnard College, Columbia University

The VERITAS array of atmospheric Cherenkov telescopes in southern Arizona is one of the world’s most sensitive detectors of TeV gamma rays. Photons at these energies trace the most extreme cosmic particle accelerators (pulsars, supernova remnants, active galactic nuclei) linking together the highest-energy astrophysical messengers: gamma rays, cosmic rays, and neutrinos. Active galactic nuclei (AGN) are the most numerous class of TeV sources. Recent results from the VERITAS observatory include the detection of sub-hour TeV flux variability from BL Lacertae, and first results from an observing campaign on the quasar 3C 279 in April 2014 during the brightest gamma-ray outburst ever recorded for this object, with flux exceeding the historic 1991 flare seen by EGRET. These observations present strong challenges to current models of energy dissipation in relativistic jets, especially concerning the role of ambient photon fields in the radiation mechanisms, and the size and location of the gamma-ray emission region.