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Peer-reviewedCC BY 4.0Monthly Notices of the Royal Astronomical Society

The formation of silicon-carbon chain molecules in IRC+10216

  • T J Millar1
  1. 1Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast , University Road, Belfast BT7 1NN ,
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Abstract

Linear silicon-carbon chain molecules, SiCn (n = 3–6), have been detected in the circumstellar envelope of the carbon-rich AGB star IRC+10216. Here, we discuss the mechanisms likely to be at work in the synthesis of chains up to SiC8 and present for the first time a detailed comparison between observations and model calculations. Using a combination of measured and postulated rate coefficients, we show that the column densities of the silicon carbide molecules observed in IRC+10216 can be reproduced to with a factor of four. Furthermore, our model calculations suggest that the column densities of SiC7 and SiC8 are a factor of 2–4 less than that of SiC6. We discuss the influence of neutral-neutral reactions involving parent SiC2 on chain growth and show that their neglect leads to a reduction in column densities of carbides up to a maximum of about six for SiC6 and SiC7. Our results suggest that the detection of SiC7 and SiC8 in IRC+10216 will be challenging but that astronomical searches should be undertaken.

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Cite

BibTeXRIS
BibTeX
@article{millar2026formation,
  title = {{The formation of silicon-carbon chain molecules in IRC+10216}},
  author = {T J Millar},
  journal = {Monthly Notices of the Royal Astronomical Society},
  year = {2026},
  month = oct,
  doi = {10.1093/mnras/stag2050},
  url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2050/9003260},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - The formation of silicon-carbon chain molecules in IRC+10216
AU  - T J Millar
PY  - 2026
DA  - 2026/10/27
JO  - Monthly Notices of the Royal Astronomical Society
DO  - 10.1093/mnras/stag2050
UR  - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2050/9003260
AB  - Linear silicon-carbon chain molecules, SiCn (n = 3–6), have been detected in the circumstellar envelope of the carbon-rich AGB star IRC+10216. Here, we discuss the mechanisms likely to be at work in the synthesis of chains up to SiC8 and present for the first time a detailed comparison between observations and model calculations. Using a combination of measured and postulated rate coefficients, we show that the column densities of the silicon carbide molecules observed in IRC+10216 can be reproduced to with a factor of four. Furthermore, our model calculations suggest that the column densities of SiC7 and SiC8 are a factor of 2–4 less than that of SiC6. We discuss the influence of neutral-neutral reactions involving parent SiC2 on chain growth and show that their neglect leads to a reduction in column densities of carbides up to a maximum of about six for SiC6 and SiC7. Our results suggest that the detection of SiC7 and SiC8 in IRC+10216 will be challenging but that astronomical searches should be undertaken.
SN  - 0035-8711
SN  - 1365-2966
ER  -