电磁级联伪装：一种模拟$γ$的方法--Blazar光谱中的类轴子粒子混合效应
Electromagnetic cascade masquerade: a way to mimic $γ$--axion-like particle mixing effects in blazar spectra
摘要：
上下文到目前为止，大多数关于河外γ射线传播的研究只考虑了初级γ射线吸收和绝热损失（“仅吸收模型”）。然而，越来越多的证据表明，这种模式过于简单，必须以某种方式加以修改。特别是，人们发现，从一些耀变体光谱的光学薄的能量范围外推的强度是不足以解释这些光谱的光学厚的部分。这种效应被解释为γ-类轴子粒子（ALP）振荡的指示。另一方面，有许多迹象表明，在一些耀变体的光谱中可能观察到由初级γ射线或核引发的电磁级联的次级分量。目的。我们研究了初级γ射线或质子的电磁级联对成像切伦科夫望远镜获得的耀变体光谱的物理解释的影响。方法.我们使用公开可用的代码ELMAG计算初级γ射线电磁级联的可观测光谱。对于原生质子的情况，我们发展了一种简单、快速和相当精确的混合方法来计算可观测谱。我们用不同的物理模型对观测到的谱能量分布进行拟合：仅吸收模型，“电磁级联模型”（对于初级γ射线的情况），以及几个版本的强子级联模型（对于初级质子的情况）。我们区分了以下几种强子级联模型：1）“基本强子模型”，假定质子束不受河外磁场的干扰，所有可观测到的γ射线都是由初级质子通过光强子过程产生的，随后发展成电磁级联
英文摘要：
Context. Most of the studies on extragalactic γ-ray propagation performed up to now only accounted for primary gamma-ray absorption and adiabatic losses ("absorption-only model"). However, there is growing evidence that this model is oversimplified and must be modified in some way. In particular, it was found that the intensity extrapolated from the optically-thin energy range of some blazar spectra is insufficient to explain the optically-thick part of these spectra. This effect was interpreted as an indication for γ-axion-like particle (ALP) oscillation. On the other hand, there are many hints that a secondary component from electromagnetic cascades initiated by primary γ-rays or nuclei may be observed in the spectra of some blazars. Aims. We study the impact of electromagnetic cascades from primary γ-rays or protons on the physical interpretation of blazar spectra obtained with imaging Cherenkov telescopes. Methods. We use the publicly-available code ELMAG to compute observable spectra of electromagnetic cascades from primary γ-rays. For the case of primary proton, we develop a simple, fast and reasonably accurate hybrid method to calculate the observable spectrum. We perform the fitting of the observed spectral energy distributions (SEDs) with various physical models: the absorption-only model, the "electromagnetic cascade model" (for the case of primary γ-rays), and several versions of the hadronic cascade model (for the case of primary proton). We distinguish the following species of hadronic cascade models: 1) "basic hadronic model", where it is assumed that the proton beam travels undisturbed by extragalactic magnetic field and that all observable γ-rays are produced by primary protons through photohadronic processes with subsequent development of electromagnetic cascades /abridged
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