A Search for TeV Gamma‐Ray Emission from High‐peaked Flat‐Spectrum Radio Quasars Using the Whipple Air Cerenkov Telescope

Blazars have traditionally been separated into two broad categories basedupon their optical emission characteristics; BL Lacs, with faint or no emissionlines, and flat spectrum radio quasars (FSRQs) with prominent, broad emissionlines. The spectral energy distribution of FSRQs has generally been thought ofas being more akin to the low-peaked BL Lacs, which exhibit a peak in theinfrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs),which exhibit a peak in UV/X-ray region of the spectrum. All blazars currentlyconfirmed as sources of TeV emission are HBLs. Recent surveys have foundseveral FSRQs exhibiting spectral properties similar to HBLs, particularly thesynchrotron peak frequency. These objects are potential sources of TeV emissionaccording to several models of blazar jet emission and blazar evolution.Measurements of TeV flux or upper limits could impact existing theoriesexplaining the links between different blazar types and could have asignificant impact on our understanding of the nature of objects that arecapable of TeV emission. In particular, the presence (or absence) of TeVemission from FSRQs could confirm (or cast doubt upon) recent evolutionarymodels that expect intermediate objects in a transitionary state between FSRQand BL Lac. The Whipple 10 meter imaging air-Cherenkov gamma-ray telescope iswell suited for TeV gamma-ray observations. Using the Whipple telescope, wehave taken data on a small selection of nearby(z<0.1 in most cases),high-peaked FSRQs. Although one of the objects, B2 0321+33, showed marginalevidence of flaring, no significant emission was detected. The implications ofthis paucity of emission and the derived upper limits are discussed.Comment: accepted for publication in Astrophysical Journa