Detection of the linear SiC$_3$ and SiC$_5$ radicals in IRC\,+10216
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| Format: | Preprint |
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2025
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| _version_ | 1866915464078163968 |
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| author | Cernicharo, José Pardo, Juan Ramón Agúndez, Marcelino Fonfría, José Pablo Velilla-Prieto, Luis Cabezas, Carlos Tercero, Belén de Vicente, Pablo Guélin, Michel |
| author_facet | Cernicharo, José Pardo, Juan Ramón Agúndez, Marcelino Fonfría, José Pablo Velilla-Prieto, Luis Cabezas, Carlos Tercero, Belén de Vicente, Pablo Guélin, Michel |
| contents | We detected the linear $^3Σ^-$ radicals SiC$_3$ and SiC$_5$ toward IRC+10216 using an ultrasensitive line survey gathered with the Yebes 40\,m radio telescope. The derived column densities of $l$-SiC$_3$ and $l$-SiC$_5$ are (3.6$\pm$0.4)$\times$10$^{12}$ cm$^{-2}$ and (1.8$\pm$0.2)$\times$10$^{12}$ cm$^{-2}$, respectively. The linear SiC$_3$ radical is $\sim$2 times less abundant that its singlet rhomboidal prolate isomer, for which we provide a new analysis based on recent sensitive observations in the Q band (7\,mm), and at 3 and 2\,mm with the IRAM 30m telescope. The emission detected from these species arises from the cool external layers of the circumstellar envelope. We speculate whether ion-neutral routes involving SiC$_n$H$_m$$^+$ cations or neutral-neutral reactions involving Si and SiC$_2$ could efficiently synthesize these species. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2508_04509 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Detection of the linear SiC$_3$ and SiC$_5$ radicals in IRC\,+10216 Cernicharo, José Pardo, Juan Ramón Agúndez, Marcelino Fonfría, José Pablo Velilla-Prieto, Luis Cabezas, Carlos Tercero, Belén de Vicente, Pablo Guélin, Michel Astrophysics of Galaxies We detected the linear $^3Σ^-$ radicals SiC$_3$ and SiC$_5$ toward IRC+10216 using an ultrasensitive line survey gathered with the Yebes 40\,m radio telescope. The derived column densities of $l$-SiC$_3$ and $l$-SiC$_5$ are (3.6$\pm$0.4)$\times$10$^{12}$ cm$^{-2}$ and (1.8$\pm$0.2)$\times$10$^{12}$ cm$^{-2}$, respectively. The linear SiC$_3$ radical is $\sim$2 times less abundant that its singlet rhomboidal prolate isomer, for which we provide a new analysis based on recent sensitive observations in the Q band (7\,mm), and at 3 and 2\,mm with the IRAM 30m telescope. The emission detected from these species arises from the cool external layers of the circumstellar envelope. We speculate whether ion-neutral routes involving SiC$_n$H$_m$$^+$ cations or neutral-neutral reactions involving Si and SiC$_2$ could efficiently synthesize these species. |
| title | Detection of the linear SiC$_3$ and SiC$_5$ radicals in IRC\,+10216 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.04509 |