Fermi Gamma-ray Space Telescope

VERITAS Observations of Flat-Spectrum Radio Quasars during Gamma-ray Flares

Aryeh Brill
(The VERITAS Collaboration)


Blazars are a type of active galactic nuclei that emit relativistic jets at small inclination angles towards Earth. Flat spectrum radio quasars (FSRQs) are a class of blazars whose gamma-ray emission peaks in the MeV-GeV band. As a result, over 400 FSRQs have been detected by Fermi-LAT, but only seven in the TeV band by ground-based instruments, including three that have been detected by VERITAS. We analyze selected observations conducted by VERITAS of three FSRQs during flaring states in the GeV band reported by Fermi-LAT between December 2013 and December 2017. These observations resulted in the detection of two of these objects, PKS 1222+216 and Ton 599, and placement of upper limits on the TeV emission of the third, 3C 279. We also present analysis of multiwavelength observations conducted during these periods. Both the detection and non-detection of TeV emission from FSRQs during lower-energy gamma-ray flares provides evidence about the source regions and emission mechanisms of gamma rays from these objects.