Progress in spectral line survey research on carbon rich asymptotic giants by Xinjiang Observatory and others_Zhongke Frontier (Xiamen) Science and Technology Research Institute

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Progress in spectral line survey research on carbon rich asymptotic giants by Xinjiang Observatory and others

Time：2024-04-29 08:06:21

IRC+10216 (CW Leo) is the closest carbon rich asymptotic giant (AGB star) to us. Astronomers have detected 106 different types of molecules in the circumstellar envelope of IRC+10216, making AGB stars regarded as "molecular factories" in interstellar space. Previously, scientists have published observations of IRC+10216 circumstellar molecules using various radio telescopes, but there have been no results of full band spectral line surveys in the 3mm band.

Recently, the Astrochemistry Research Group of the Chinese Academy of Sciences Xinjiang Observatory, in conjunction with domestic and international scientific research teams, used the 13.7m Delingha radio telescope to conduct a full band spectral line survey of IRC+10216 at the 3 mm band, identified 75 molecular spectral lines (96 transitions), and determined that they came from 19 molecular species and their isotopes. Among them, the emission spectrum of one molecule was detected for the first time in IRC+10216. This study assumes that these molecular spectral lines are in local thermodynamic equilibrium, calculates the excitation temperature, column density, and relative abundance to H2 of these molecules, and obtains isotopic abundance ratios of [12C]/[13C], [32S]/[34S], [28Si]/[29Si], and [12C34S]/[13C32S]. Research combining published single antenna telescope observation data has found that higher rotational transitions of HC3N, HC5N, HC7N, HC9N, C3S, CH3CN, SiS, and C4H molecules can trace high-temperature gases closer to stars in the IRC+10216 perihelion envelope.

Furthermore, this study compared the observation results of the same molecular spectral line using radio telescopes with different angular resolutions. Research has found that for strong molecular spectral lines, the integrated intensity and spectral line profile obtained when observed with telescopes at different angular resolutions are basically the same; For molecular spectral lines with optically thin bimodal structures, using a telescope with higher spatial resolution can obtain a more pronounced intensity ratio of line wings and line centers.

In addition, this work summarizes the column densities of all molecules detected in the IRC+10216 orbit to date, as well as the latest research results of astrochemical models.

The above work has advanced the research process of spectral line survey of IRC+10216 in the 3mm band. The relevant research results are published in the supplement of the Journal of Astrophysics.

Paper link:论文链接