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arXiv 2408.02458astro-ph.HE
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湍流级联中耀变体的最小随机变率模型

A Minimal Stochastic Variability Model of Blazars in Turbulent Cascade

Nan Ding, Yunyong Tang, Qiusheng Gu, Rui Xue, Yongyun Chen

AI总结:

提出基于磁化喷流湍流级联的最小物理模型,解释耀变体长期随机变率、PSD高频陡化及FVA特征。

摘要:

本文提出一种新颖的最小物理模型,用以阐明耀变体的长期随机变率。该模型建立在磁化等离子体喷流通过湍流级联过程耗散能量的现实背景之上,该过程将能量转移至具有高度各向异性辐射的小尺度结构。模型表明,在基础物理参数均匀随机波动的条件下,它能够自发生成与耀变体观测相符的变率特征。这表明该模型在多个时间尺度上具有自相似性,为在不同类型耀变体中观测到的普遍功率谱密度(PSD)结构提供了自然解释。此外,模型显示,当级联过程产生相对平坦的团块能量分布时,模型模拟的高频段PSD谱指数将比阻尼随机游走(DRW)模型预测的更陡,这与近期活动星系核(AGN)变率观测一致,并提供了合理的理论解释。该模型还能够再现观测到的耀变体分数变率振幅(FVA)特征,并表明团块内部具体的粒子加速和辐射冷却过程可能并非塑造长期随机变率的关键因素。这一最小模型为理解耀变体的长期随机变率提供了新的物理视角。

英文摘要:

In this paper, we propose a novel minimal physical model to elucidate the long-term stochastic variability of blazars. The model is built on the realistic background of magnetized plasma jets dissipating energy through a turbulent cascade process that transfers energy to small-scale structures with highly anisotropic radiation. The model demonstrates the ability to spontaneously generate variability features consistent with observations of blazars under uniformly random fluctuations in the underlying physical parameters. This indicates that the model possesses self-similarity across multiple time scales, providing a natural explanation for the universal power spectral density (PSD) structure observed in different types of blazars. Moreover, the model exhibits that when the cascade process produces a relatively flat blob energy distribution, the spectral index of the model-simulated PSD in the high-frequency regime will be steeper than that predicted by the Damped Random Walk (DRW) model, which is in agreement with recent observations of active galactic nucleus (AGN) variability, providing a plausible theoretical explanation. The model is also able to reproduce the observed fractional variability amplitude (FVA) characteristics of blazars, and suggests that the specific particle acceleration and radiative cooling processes within the blob may not be the key factor shaping the long-term stochastic variability. This minimal model provides a new physical perspective for understanding the long-term stochastic variability of blazars.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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