论文标题
在空间解决的中红外观察结果对重生对象的折叠环境FG SGE的环境环境
Spatially resolved mid-infrared observations of the circumstellar environment of the born-again object FG Sge
论文作者
论文摘要
储层计算是预测湍流的有力工具，其简单的架构具有处理大型系统的计算效率。然而，其实现通常需要完整的状态向量测量和系统非线性知识。我们使用非线性投影函数将系统测量扩展到高维空间，然后将其输入到储层中以获得预测。我们展示了这种储层计算网络在时空混沌系统上的应用，该系统模拟了湍流的若干特征。我们表明，使用径向基函数作为非线性投影器，即使只有部分观测并且不知道控制方程，也能稳健地捕捉复杂的系统非线性。最后，我们表明，当测量稀疏、不完整且带有噪声，甚至控制方程变得不准确时，我们的网络仍然可以产生相当准确的预测，从而为实际湍流系统的无模型预测铺平了道路。
FG Sge has evolved from the hot central star of the young planetary nebula Hen 1-5 to a G-K supergiant in the last 100 years. It is one of the three born-again objects that has been identified as of yet, and they are considered to have undergone a thermal pulse in the post-asymptotic giant branch evolution. FG Sge was observed with MIDI at the Very Large Telescope Interferometer at baselines of 43 and 46 m between 8 and 13 micron. The circumstellar dust environment of FG Sge was spatially resolved, and the Gaussian fit to the observed visibilities results in a full width at half maximum of ~10.5 mas. The observed mid-infrared visibilities and the spectral energy distribution can be fairly reproduced by optically thick (tauV ~ 8) spherical dust shell models consisting of amorphous carbon with an inner radius Rin of ~30 Rstar (corresponding to a dust temperature of 1100 +/- 100 K). The dust shell is characterized with a steep density profile proportional to r^{-3.5+/-0.5} from the inner radius Rin to (5-10) x Rin, beyond which it changes to r^{-2}. The dust mass is estimated to be ~ 7 x 10^{-7} solar mass, which translates into an average total mass-loss rate of ~9 x 10^{-6} solar mass/yr as of 2008 with a gas-to-dust ratio of 200 being adopted. In addition, the 8--13 micron spectrum obtained with MIDI with a field of view of 200 mas does not show a signatureof the polycyclic aromatic hydrocarbon (PAH) emission, which is in marked contrast to the spectra taken with the Spitzer Space Telescope six and 20 months before the MIDI observations with wide slit widths of 3.6--10 arcsec. This implies that the PAH emission originates from an extended region of the optically thick dust envelope, i.e., from the material ejected before the central star became H-deficient.
