论文标题
21和30微米来源中的分子气：2 \，mm和1.3 \，IRAS \，21318+5631和22272+5435
Molecular gas in 21 and 30 micron sources: the 2\,mm and 1.3\,mm spectra of IRAS\,21318+5631 and 22272+5435
论文作者
论文摘要
21和30 \的载体，$μ$ M的发射特征是折线信封的红外光谱，这是一个长期的谜。 In this paper, we present the results of molecular line observations toward two circumstellar envelopes exhibiting the 21 and/or 30\,$μ$m features, IRAS\,21318+5631 and 22272+5435, aiming at investigating whether they have unusual gas-phase chemistry and searching for possible gas-phase precursor of the carriers of the two dust features.光谱涵盖了130--164 \，GHz和216.5---273 \，GHz的几个离散频率范围，导致每个物体中检测到13个分子物种和同位素学。进行旋转二元分析以确定分子丰度，柱密度和激发温度。我们没有发现在正常C富含C的恒星中出乎意料的任何分子物种。然而，它们的分子丰度之间存在细微的差异。 Iras \，22272+5435显示SIC $ _2 $和HC $ _3 $ n线和SIS线比IRAS \，21318+5631更弱，这可能表明这21 \，$μ$ M源是碳富集更多的碳，并且经历了更有效的灰尘形成。我们讨论了结果对21 \，$μ$ m和30 \，$μ$ m功能的潜在影响。
The carriers of the 21 and 30\,$μ$m emission features in infrared spectra of circumstellar envelopes are a long-standing enigma. In this paper, we present the results of molecular line observations toward two circumstellar envelopes exhibiting the 21 and/or 30\,$μ$m features, IRAS\,21318+5631 and 22272+5435, aiming at investigating whether they have unusual gas-phase chemistry and searching for possible gas-phase precursor of the carriers of the two dust features. The spectra cover several discrete frequency ranges of 130--164\,GHz and 216.5--273\,GHz, resulting in a detection of 13 molecular species and isotopologues in each object. Rotation-diagram analysis is carried out to determine the molecular abundances, column densities, and excitation temperatures. We did not discover any molecular species that is unexpected in a normal C-rich star. Nevertheless, there exists subtle difference between their molecular abundances. IRAS\,22272+5435 shows stronger SiC$_2$ and HC$_3$N lines and weaker SiS lines than IRAS\,21318+5631, presumably suggesting that this 21\,$μ$m source is more carbon rich and has experienced a more efficient dust formation. We discuss the potential implications of the results for the carriers of the 21\,$μ$m and 30\,$μ$m features.
