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Paper: Ultra High Frequency Peaked BL Lac Objects
Volume: 299, High Energy Blazar Astronomy
Page: 47
Authors: Beckmann, V.
Abstract: The unification of the BL Lac sequence is based on the observation that the differences between radio and X-ray selected BL Lacs are due to different peak frequencies of their synchrotron and inverse Compton emission. Based on the large and complete HRX-BL Lac sample, dependencies of several physical parameters (such as luminosity, spectral shape, and spectral energy distribution) on the synchrotron emission peak are shown. It is also possible to explain the different evolutionary behaviour in a unified scheme. Finally, implications on the existence of ultra high frequency peaked BL Lac objects (UHBL) can be made. These objects have their synchrotron peak at frequencies higher than 100 keV and make them possible targets for observations in Gamma-rays. First encouraging results from studying UHBL candidates of the HRX-BL Lac sample and from follow-up observations in the optical domain and with BeppoSAX will be presented. One recently discovered UHBL is likely to be the counterpart of an unidentified EGRET source.
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