Polycyclic Aromatic Hydrocarbons and Crystalline Silicates in the Bipolar Post-Asymptotic Giant Branch Star IRAS 16279–4757
Polycyclic Aromatic Hydrocarbons and Crystalline Silicates in the Bipolar Post-Asymptotic Giant Branch Star IRAS 16279–4757
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双极后渐近巨星分支星 IRAS 16279–4757 中的多环芳烃和结晶硅酸盐
DOI：
10.1086/382064
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
L. Keller
中科院分区：
文献类型：
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作者：
M. Matsuura;A. Zijlstra;F. Molster;S. Hony;Laurentius Waters;F. Kemper;J. Bowey;H. Chihara;C. Koike;L. Keller
IRAS 16279-4757 属于一组渐近后巨分支（后 AGB）恒星，显示出多环芳烃（PAH）带和结晶硅酸盐。我们展示了首次解析该物体的中红外图像。其形态与“红色矩形”(HD 44179) 的形态相似，“红色矩形”是含有多环芳烃和结晶硅酸盐的原型物体。双组分模型和图像表明有一个致密的富氧环面、一个内部低密度富碳区域和一个富碳双极流出区。 PAH 谱带在流出处增强，而连续谱发射向中心集中。我们的研究结果支持混合化学和形态学密切相关的建议。我们讨论 IRAS 16279-4757 的红外空间天文台短波长光谱仪 (ISO SWS) 光谱。 ISO SWS 光谱中的几个波段显示与钙长石相匹配：这将是在太阳系之外首次检测到这种矿物。与 HD 44179 相比，PAH 带的形状更接近行星状星云的形状，可能与 HD 44179 中存在但在 IRAS 16279-4757 周围不存在的小 PAH 群有关。对光谱的详细检查显示了这两个物体的独特特征。比较表明，在 IRAS 16279-4757 中发现的环面可能比在 HD 44179 中发现的环面形成得更晚。
IRAS 16279-4757 belongs to a group of post-asymptotic giant branch (post-AGB) stars showing both polycyclic aromatic hydrocarbon (PAH) bands and crystalline silicates. We present mid-infrared images that resolve the object for the first time. The morphology is similar to that of the "Red Rectangle" (HD 44179), the prototype object with PAHs and crystalline silicates. A two-component model and images suggest a dense oxygen-rich torus, an inner, low-density, carbon-rich region, and a carbon-rich bipolar outflow. The PAH bands are enhanced at the outflow, while the continuum emission is concentrated toward the center. Our findings support the suggestion that mixed chemistry and morphology are closely related. We discuss the Infrared Space Observatory Short-Wavelength Spectrometer (ISO SWS) spectra of IRAS 16279-4757. Several bands in the ISO SWS spectrum show a match with anorthite: this would be the first detection of this mineral outside the solar system. Compared to HD 44179, the shapes of PAH bands are closer to those of planetary nebulae, possibly related to a population of small PAHs present in HD 44179 but absent around IRAS 16279-4757. Detailed examination of the spectra shows the individual character of these two objects. The comparison suggests that the torus found in IRAS 16279-4757 may have formed more recently than that in HD 44179.