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Date and Time of the Query: 2019-06-25 T06:43:11 PDT
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For refcode 2009A&A...494..527H:
Retrieve 87 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2009A&A...494..527H Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies Hovatta, T.; Valtaoja, E.; Tornikoski, M.; Lahteenmaki, A. Abstract. Aims. We have calculated variability Doppler boosting factors, Lorentz factors, and viewing angles for a large sample of sources by using total flux density observations at 22 and 37 GHz and VLBI data. Methods: We decomposed the flux curves into exponential flares and determined the variability brightness temperatures of the fastest flares. By assuming the same intrinsic brightness temperature for each source, we calculated the Doppler boosting factors for 87 sources. In addition we used new apparent jet speed data to calculate the Lorentz factors and viewing angles for 67 sources. Results: We find that all quasars in our sample are Doppler-boosted and that the Doppler boosting factors of BL Lacertae objects are lower than of quasars. The new Lorentz factors are about twice as high as in earlier studies, which is mainly due to higher apparent speeds in our analyses. The jets of BL Lacertae objects are slower than of quasars. There are some extreme sources with very high derived Lorentz factors of the order of a hundred. These high Lorentz factors could be real. It is also possible that the sources exhibit such rapid flares that the fast variations have remained undetected in monitoring programmes, or else the sources have a complicated jet structure that is not amenable to our simple analysis. Almost all the sources are seen in a small viewing angle of less than 20 degrees. Our results follow the predictions of basic unification schemes for AGN. Key words: galaxies: active, galaxies: jets, radio continuum: galaxies, radiation mechanisms: non-thermal, galaxies: quasars: general =========================================================================== 2009A&A...498..723H Doppler factors, Lorentz factors, and viewing angles for quasars, BL Lacertae objects and radio galaxies [A&A, 494, 527-537 (2009)] Hovatta, T.; Valtaoja, E.; Tornikoski, M.; Lahteenmaki, A. Erratum. Abstract. We report an error in the apparent speed, Lorentz factor and viewing angle of the source 0923+392 (4C 39.25) in the paper Hovatta et al. 2009 (A&A, 494, 527). Due to the error in the original MOJAVE database, the apparent speed value of 0923+392 changes from 42.9c to 4.29c. This affects the Lorentz factor and viewing angle of the source, and the new values are {gamma}_var_ = 4.4 and {theta}_var_ = 13.4deg. The error does not affect any of our major conclusions, and as the source was excluded from most of the figures and statistics due to the extreme Lorentz factor, most of the figures remain the same. In Fig. 10 the source is shown in the top of the plot as an LPQ source, and it now shifts to coordinates log(T_b_) = 12.6 and {beta}_app_= 4.3. The corrected figure is shown in this erratum. Subsequently, parts in the discussion concerning the extremity of this source are obsolete. {see text} Key words: galaxies: active, galaxies: jets, radio continuum: galaxies, radiation mechanisms: non-thermal, quasars: general, errata, addenda ===========================================================================
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