Time lags of the flickering in cataclysmic variables as a function of wavelength
Time lags of the flickering in cataclysmic variables as a function of wavelength
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灾难性变量闪烁的时滞作为波长的函数
DOI：
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发表时间：
2015
期刊：
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通讯作者：
A. Bruch
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文献类型：
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作者：
A. Bruch
上下文。闪烁是灾变变量中普遍存在的现象。虽然底层光源是光辐射的主要贡献者之一，但导致闪烁的机制尚不清楚。目标。本研究旨在促进由观测定义的边界条件集，这些边界条件必须由描述闪烁的物理模型来满足。具体地，检查了在光学范围内的不同波长的闪烁事件发生的时间滞后。方法：研究方法。为此，分析了在不同光度系统的不同波段同时或准同时观察到的一组CV样本的多条光曲线的互相关函数(CCF)。结果。CCF的最大值偏离零时移表明闪烁活动与波长的依赖关系，即闪烁耀斑在蓝色范围内比在红色范围内略早达到最大值。虽然现有的观测材料不允许在所有观测系统中单独检测这一点，但所有数据的集合清楚地表明了这一效应。特别具有启发性的是V603Aq1和TT Ari的情况，在U和R波段之间分别观察到15.S 1和4.3的时间滞后。原则上，如果在闪烁耀斑的发展过程中，负责闪烁的光源的辐射特性发生变化，使得在耀斑的早期阶段发射更多的短波辐射，并且稍后发射的峰值向红色移动，则可以理解这一点。讨论了各自的设想，并表明它们在定性和定量上与观察结果一致。
Context. Flickering is a ubiquitous phenomenon in cataclysmic variables (CVs). Although the underlying light source is one of the main contributors to the optical radiation, the mechanism leading to flickering is not understood as yet. Aims. The present study aims to contribute to the set of boundary conditions, defined by observations, which must be met by physical models that describe the flickering. In particular, time lags in the occurrence of flickering events at different wavelengths over the optical range are examined. Methods. To this end, the cross-correlation functions (CCFs) of numerous light curves of a sample of CVs are analysed that were observed simultaneously or quasi-simultaneously in different bands of various photometric systems. Results. Deviations of the maxima of the CCFs from zero time-shift indicate a dependence of the flickering activity on the wavelength in the sense that flickering flares reach their maxima slightly earlier in the blue range than in the red. While the available observational material does not permit detecting this individually in all observed systems, the ensemble of all data clearly shows this effect. Particularly instructive are the cases of V603 Aql and TT Ari, where time lags of 15. s 1a nd 4. 3, respectively, are observed between the U and R bands. In principle this can be understood if during the development of a flickering flare the radiation characteristics of the light source responsible for flickering change such that in the early phases of a flare more short-wavelength radiation is emitted, and later on, the peak of the emission shifts to the red. Respective scenarios are discussed and shown to be in qualitative and quantitative agreement with observations.