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Abstract: We have calculated variability Doppler boosting factors, Lorentz factors, andviewing angles for a large sample of sources by using total flux densityobservations at 22 and 37 GHz and VLBI data. We decomposed the flux curves intoexponential flares and determined the variability brightness temperatures ofthe fastest flares. By assuming the same intrinsic brightness temperature foreach source, we calculated the Doppler boosting factors for 87 sources. Inaddition we used new apparent jet speed data to calculate the Lorentz factorsand viewing angles for 67 sources. We find that all quasars in our sample areDoppler-boosted and that the Doppler boosting factors of BL Lacertae objectsare lower than of quasars. The new Lorentz factors are about twice as high asin earlier studies, which is mainly due to higher apparent speeds in ouranalyses. The jets of BL Lacertae objects are slower than of quasars. There aresome extreme sources with very high derived Lorentz factors of the order of ahundred. These high Lorentz factors could be real. It is also possible that thesources exhibit such rapid flares that the fast variations have remainedundetected in monitoring programmes, or else the sources have a complicated jetstructure that is not amenable to our simple analysis. Almost all the sourcesare seen in a small viewing angle of less than 20 degrees. Our results followthe predictions of basic unification schemes for AGN.



Author: T. Hovatta, E. Valtaoja, M. Tornikoski, A. Lähteenmäki

Source: https://arxiv.org/



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