IRAS 13224 $-$ 3809特征X射线光谱变化的起源
Origin of the Characteristic X-ray Spectral Variations of IRAS 13224$-$3809
摘要：
窄线塞弗特1星系（NLS 1）IRAS 13224 $-$ 3809已知表现出显著的X射线光谱变化，在$\sim$ 7 keV处光谱急剧下降，强烈的软过量发射，以及铁L边缘特征的暗示，这与NLS 1 1 H 0707 $-$ 495非常相似。我们提出了“可变双部分覆盖（VDPC）模型”来解释1H 0707 $-$ 495的能谱和光谱可变性（Mizumoto，Ebisawa and Sameshima 2014，PASJ，66，122）。在该模式中，观测到的$\sim$日内10 keV以下的通量/光谱变化主要是由视线内由双吸收层组成的斑片云部分覆盖率的变化引起的。在本文中，我们应用VDPC模型IRAS 13224 $-$ 3809。因此，我们发现VDPC模型可以解释观测到的IRAS 13224 $-$ 3809在0.5 $-$ 10 keV波段的光谱变化。特别是，我们可以解释所观察到的均方根（RMS）光谱（能量依赖的分数通量变化）在整个0.5 $-$ 10千电子伏带。除了众所周知的铁K带的显着下降，我们发现有趣的铁L峰的RMS谱时，铁的L-边缘是特别深。该特征也在1H 0707 $-$ 495中发现，自然地用VDPC模型解释，使得RMS变化在部分吸收体的光学深度大的能量处增加。吸收体在铁L边处的光学深度比相邻能带中的光学深度大，因此出现特征铁L峰。另一方面，就在铁K边缘之下，光学深度最低，RMS光谱具有宽的倾角。
英文摘要：
The Narrow-line Seyfert 1 galaxy (NLS1) IRAS 13224$-$3809 is known to exhibit significant X-ray spectral variation, a sharp spectral drop at $\sim$ 7 keV, strong soft excess emission, and a hint of iron L-edge feature, which is very similar to the NLS1 1H 0707$-$495. We have proposed the "Variable Double Partial Covering (VDPC) model" to explain the energy spectra and spectral variability of 1H 0707$-$495 (Mizumoto, Ebisawa and Sameshima 2014, PASJ, 66, 122). In this model, the observed flux/spectral variations below 10 keV within a $\sim$day are primarily caused by change of the partial covering fraction of patchy clouds composed by double absorption layers in the line of sight. In this paper, we apply the VDPC model to IRAS 13224$-$3809. Consequently, we have found that the VDPC model can explain the observed spectral variations of IRAS 13224$-$3809 in the 0.5$-$10 keV band. In particular, we can explain the observed Root Mean Square (RMS) spectra (energy dependence of the fractional flux variation) in the entire 0.5$-$10 keV band. In addition to the well-known significant drop in the iron K-band, we have found intriguing iron L-peaks in the RMS spectra when the iron L-edge is particularly deep. This feature, which is also found in 1H 0707$-$495, is naturally explained with the VDPC model, such that the RMS variations increase at the energies where optical depths of the partial absorbers are large. The absorbers have a larger optical depth at the iron L-edge than in the adjacent energy bands, thus a characteristic iron L-peak appears. On the other hand, just below the iron K-edge, the optical depth is the lowest and the RMS spectrum has a broad dip.
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。
