The chemical composition of the circumstellar envelopes around yellow hypergiant stars
The chemical composition of the circumstellar envelopes around yellow hypergiant stars
复制标题
黄超巨星周围星周包膜的化学成分
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
J. Alcolea
中科院分区：
文献类型：
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作者：
G. Quintana;V. Bujarrabal;A. Castro;J. Alcolea
语境。黄特超巨星（YHG）是极其明亮的大质量天体，其一般特性却鲜为人知。这种类型的恒星中只有两颗显示出巨大的星周包层：IRC +10420 和 AFGL2343。目标。我们的目标是通过与众所周知的 AGB 恒星和原行星状星云进行比较，研究这两个源周围的星周包膜的化学成分。我们还估计了观察到的分子种类的丰度。方法。我们对十二种分子的不同跃迁进行了单皿观察。我们将 AFGL2343 和 IRC +10420 中的分子跃迁强度和估计丰度的比率与富含 0 和富含 C 的 AGB 恒星和原行星状星云中的比率进行了比较。结果。 YHG、AFGL 2343 和 IRC +10420 都被发现具有与富含 0 的 AGB 恒星类似的富含 0 的化学物质，尽管对于 AFGL 2343，与 13 CO 线相比，大多数分子的发射相对较弱。当我们比较根据距离校正的线强度和剖面宽度时，与其他进化源的明显差异就会出现，YHG 中的线强度和剖面宽度分别非常强和非常宽。 IRC +10420 获得的丰度与 AGB 恒星中发现的丰度一致，但总的来说，除了 13 CO 之外，AFGL2343 中发现的丰度太低。 AFGL2343 中分子丰度明显较低的原因可能是这些分子仅存在于质量相对较低的壳内部区域。
Context. The yellow hypergiant stars (YHGs) are extremely luminous and massive objects whose general properties are poorly known. Only two of this kind of star show massive circumstellar envelopes, IRC +10420 and AFGL2343. Aims. We aim to study the chemistry of the circumstellar envelopes around these two sources, by comparison with well known AGB stars and protoplanetary nebulae. We also estimate the abundances of the observed molecular species. Methods. We have performed single-dish observations of different transitions for twelve molecular species. We have compared the ratio of the intensities of the molecular transitions and of the estimated abundances in AFGL2343 and IRC +10420 with those in 0-rich and C-rich AGB stars and protoplanetary nebulae. Results. Both YHGs, AFGL 2343, and IRC +10420, have been found to have an 0-rich chemistry similar to that in 0-rich AGB stars, though for AFGL 2343 the emission of most molecules compared with 13 CO lines is relatively weak. Clear differences with the other evolved sources appear when we compare the line intensity corrected for distance and the profile widths which are, respectively, very intense and very wide in YHGs. The abundances obtained for IRC +10420 agree with those found in AGB stars, but in general those found in AFGL2343, except for 13 CO, are too low. This apparently low molecular abundance in AFGL2343 could be due to the fact that these molecules are present only in an inner region of the shell where the mass is relatively low.