论文标题
部分可观测时空混沌系统的无模型预测
Limits on X-ray Polarization at the Core of Centaurus A as Observed with the Imaging X-ray Polarimetry Explorer
论文作者
论文摘要
我们使用Imaging X射线极性Explorer（IXPE）中的100K观察结果，介绍了$ 2-8 \ thinspace \ mathrm {kev} $ band x射线极化的测量值。几乎同时观察了CEN A，也与迅速，nustar和整体观测值一起进行。 IXPE未检测到统计学上显着的极化程度。这些观察值的最低可检测到极化为$ 99 \％$百分比的信心（MDP $ _ {99} $），$ 6.5 \％$，使用加权频谱模型的计算在$ 2-8 \ thinspace \ thinspace \ mathrm {kev} $ band中。因此，极化角度$ψ$不受限制。 X射线能量的三个数量级的光谱拟合（$ 0.3-400 \ thinspace \ mathrm {kev} $）表明，CEN A的SED由简单的功率定律很好地描述，具有中等内在的吸收排放线，尽管需要第二次未吸收的功率定律来说明低于$ 2 \ thinspace \ mathrm {kev} $的能量的观察到的光谱。该频谱表明，负责该发射线的后处理材料在光学上很薄且与中央黑洞相距遥远。我们对X射线极化的上限与康普顿散射的预测一致，尽管无法识别负责X射线产生的特定种子光子种群。低极化程度，核心发射的变异性以及Fe K $α$发射线的相对缺乏可变性支持一张图片，其中电子在最内向飞机周围的高度无序磁场区域加速。
We present measurements of the polarization of X-rays in the $2-8 \thinspace \mathrm{keV}$ band from the nucleus of the radio galaxy Centaurus A (Cen A), using a 100ks observation from the Imaging X-ray Polarimetry Explorer (IXPE). Nearly simultaneous observations of Cen A were also taken with the Swift, NuSTAR, and INTEGRAL observatories. No statistically significant degree of polarization is detected with IXPE. These observations have a minimum detectable polarization at $99 \%$ percent confidence (MDP$_{99}$) of $6.5 \%$ using a weighted, spectral model-independent calculation in the $2-8 \thinspace \mathrm{keV}$ band. The polarization angle $ψ$ is consequently unconstrained. Spectral fitting across three orders of magnitude in X-ray energy ($0.3-400 \thinspace \mathrm{keV}$) demonstrates that the SED of Cen A is well described by a simple power law with moderate intrinsic absorption ($N_H \sim 10^{23} \thinspace \mathrm{cm}^{-2}$) and a Fe K$α$ emission line, although a second unabsorbed power law is required to account for the observed spectrum at energies below $2 \thinspace \mathrm{keV}$. This spectrum suggests that the reprocessing material responsible for this emission line is optically thin and distant from the central black hole. Our upper limits on the X-ray polarization are consistent with the predictions of Compton scattering, although the specific seed photon population responsible for production of the X-rays cannot be identified. The low polarization degree, variability in the core emission, and the relative lack of variability in the Fe K$α$ emission line support a picture where electrons are accelerated in a region of highly disordered magnetic fields surrounding the innermost jet.
