<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Petropoulou, M.</style></author><author><style face="normal" font="default" size="100%">Arfani, D.</style></author><author><style face="normal" font="default" size="100%">Mastichiadis, A.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Spontaneously quenched γ-ray spectra from compact sources</style></title><short-title><style face="normal" font="default" size="100%">Astronomy and Astrophysics</style></short-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Astrophysics - High Energy Astrophysical Phenomena</style></keyword><keyword><style  face="normal" font="default" size="100%">BL Lacertae objects: general</style></keyword><keyword><style  face="normal" font="default" size="100%">gamma rays: general</style></keyword><keyword><style  face="normal" font="default" size="100%">radiation mechanisms: non-thermal</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2013</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2013/09/1</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://ui.adsabs.harvard.edu/abs/2013A&amp;A...557A..48P</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">557</style></volume><pages><style face="normal" font="default" size="100%">A48</style></pages><isbn><style face="normal" font="default" size="100%">0004-6361</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;BR /&gt; Aims: We have studied a mechanism for producing intrinsic broken power-law γ-ray spectra in compact sources. This is based on the principles of automatic photon quenching, according to which γ-rays are being absorbed on spontaneously produced soft photons whenever the injected luminosity in γ-rays lies above a certain critical value. &lt;BR /&gt; Methods: We derived an analytical expression for the critical γ-ray compactness in the case of power-law injection. For the case where automatic photon quenching is relevant, we calculated analytically the emergent steady-state γ-ray spectra. We also performed numerical calculations in order to back up our analytical results. &lt;BR /&gt; Results: We show that a spontaneously quenched power-law γ-ray spectrum obtains a photon index 3Γ/2, where Γ is the photon index of the power-law at injection. Thus, large spectral breaks of the γ-ray photon spectrum, e.g. ΔΓ ≳ 1, can be obtained by this mechanism. We also discuss additional features of this mechanism that can be tested observationally. Finally, we fit the multiwavelength spectrum of a newly discovered blazar (PKS 0447-439) by using such parameters to explain the break in the γ-ray spectrum by means of spontaneous photon quenching, under the assumption that its redshift lies in the range 0.1 &lt; z &lt; 0.24.</style></abstract></record></records></xml>