2005/11/21 by Gilles Henri, Ludovic Sauge · 6 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Energy (signal processing) #Energy density #Energy spectrum #Gamma-ray bursts and supernovae #Lorentz factor #Lorentz transformation #Particle physics theoretical and experimental studies #astro-ph
paper · pdf · doi:10.1086/500039
published as Astrophys.J.640:185-195,2006 · 31 pages, 5 figures. Accepted for publication in ApJ
arxiv created 2005/11/21 · openalex publication_date 2006/03/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
There is growing evidence that the estimations of the beaming Doppler factor in TeV BL Lac objects based on the synchrotron self-Compton (SSC) models are in strong disagreement with those deduced from the unification models between blazars and radio galaxies. When corrected from extragalactic absorption by the diffuse infrared background (DIrB), the SSC one-zone models require a very high Lorentz factor (around 50) to avoid strong γ-γ absorption. However, the statistics on beamed versus unbeamed objects, as well as the luminosity contrast, favors a much lower Lorentz factor, on the order of 3. In this paper, we show that for the special case of Markarian 501, the need for a very high Lorentz factor is unavoidable for all one-zone models in which all photons are assumed to be produced at the same location at the same time. Models assuming a double structure with two different beaming patterns can partially solve the problem of luminosity contrast, but we point out that they are inconsistent with the statistics on the number of detected TeV sources. The only way to solve the issue is to consider inhomogeneous models, in which low-energy and high-energy photons are not produced at the same place, allowing for much smaller Lorentz factors. This approach implies that the jet is stratified, but also that the particle energy distribution is close to a monoenergetic one and that pair production is likely to be significant. The implications for relativistic jet physics and the particle acceleration mechanism are discussed.