Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216
A new interstellar molecule, FeC ( X ^3 Δ _i ), has been identified in the circumstellar envelope of the carbon-rich asymptotic giant branch star IRC+10216. FeC is the second iron-bearing species conclusively observed in the interstellar medium, in addition to FeCN, also found in IRC+10216. The J =...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/ad0899 |
| _version_ | 1827762161193058304 |
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| author | L. A. Koelemay L. M. Ziurys |
| author_facet | L. A. Koelemay L. M. Ziurys |
| author_sort | L. A. Koelemay |
| collection | DOAJ |
| description | A new interstellar molecule, FeC ( X ^3 Δ _i ), has been identified in the circumstellar envelope of the carbon-rich asymptotic giant branch star IRC+10216. FeC is the second iron-bearing species conclusively observed in the interstellar medium, in addition to FeCN, also found in IRC+10216. The J = 4 → 3, 5 → 4, and 6 → 5 rotational transitions of this free radical near 160, 201, and 241 GHz, respectively, were detected in the lowest spin–orbit ladder, Ω = 3, using the Submillimeter Telescope of the Arizona Radio Observatory (ARO) for the 1 mm lines and the ARO 12 m at 2 mm. Because the ground state of FeC is inverted, these transitions are the lowest energy lines. The detected features exhibit slight U shapes with LSR velocities near V _LSR ≈ −26 km s ^−1 and linewidths of Δ V _1/2 ≈ 30 km s ^−1 , line parameters characteristic of IRC+10216. Radiative transfer modeling of FeC suggests that the molecule has a shell distribution with peak radius near 300 R _* (∼6″) extending out to ∼500 R _* (∼10″) and a fractional abundance, relative to H _2 , of f ∼ 6 × 10 ^−11 . The previous FeCN spectra were also modeled, yielding an abundance of f ∼ 8 × 10 ^−11 in a larger shell situated near 800 R _* . These distributions suggest that FeC may be the precursor species for FeCN. Unlike cyanides and carbon-chain molecules, diatomic carbides with a metallic element are rare in IRC+10216, with FeC being the first such detection. |
| first_indexed | 2024-03-11T10:25:57Z |
| format | Article |
| id | doaj.art-a6d8904a86bc423ebee375cd18cf3ca5 |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-11T10:25:57Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-a6d8904a86bc423ebee375cd18cf3ca52023-11-15T16:00:31ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019581L610.3847/2041-8213/ad0899Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216L. A. Koelemay0https://orcid.org/0000-0001-9334-3149L. M. Ziurys1https://orcid.org/0000-0002-1805-3886Department of Chemistry and Biochemistry, Steward Observatory, University of Arizona , 1305 E. 4th Street Tucson, AZ 85719, USADepartment of Chemistry and Biochemistry, Steward Observatory, University of Arizona , 1305 E. 4th Street Tucson, AZ 85719, USA; Department of Astronomy, Steward Observatory, University of Arizona , 1305 E. 4th Street Tucson, AZ 85719, USAA new interstellar molecule, FeC ( X ^3 Δ _i ), has been identified in the circumstellar envelope of the carbon-rich asymptotic giant branch star IRC+10216. FeC is the second iron-bearing species conclusively observed in the interstellar medium, in addition to FeCN, also found in IRC+10216. The J = 4 → 3, 5 → 4, and 6 → 5 rotational transitions of this free radical near 160, 201, and 241 GHz, respectively, were detected in the lowest spin–orbit ladder, Ω = 3, using the Submillimeter Telescope of the Arizona Radio Observatory (ARO) for the 1 mm lines and the ARO 12 m at 2 mm. Because the ground state of FeC is inverted, these transitions are the lowest energy lines. The detected features exhibit slight U shapes with LSR velocities near V _LSR ≈ −26 km s ^−1 and linewidths of Δ V _1/2 ≈ 30 km s ^−1 , line parameters characteristic of IRC+10216. Radiative transfer modeling of FeC suggests that the molecule has a shell distribution with peak radius near 300 R _* (∼6″) extending out to ∼500 R _* (∼10″) and a fractional abundance, relative to H _2 , of f ∼ 6 × 10 ^−11 . The previous FeCN spectra were also modeled, yielding an abundance of f ∼ 8 × 10 ^−11 in a larger shell situated near 800 R _* . These distributions suggest that FeC may be the precursor species for FeCN. Unlike cyanides and carbon-chain molecules, diatomic carbides with a metallic element are rare in IRC+10216, with FeC being the first such detection.https://doi.org/10.3847/2041-8213/ad0899AstrochemistryEvolved starsCircumstellar envelopesInterstellar moleculesRadio astronomyAsymptotic giant branch stars |
| spellingShingle | L. A. Koelemay L. M. Ziurys Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 The Astrophysical Journal Letters Astrochemistry Evolved stars Circumstellar envelopes Interstellar molecules Radio astronomy Asymptotic giant branch stars |
| title | Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 |
| title_full | Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 |
| title_fullStr | Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 |
| title_full_unstemmed | Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 |
| title_short | Elusive Iron: Detection of the FeC Radical (X 3Δ i ) in the Envelope of IRC+10216 |
| title_sort | elusive iron detection of the fec radical x 3δ i in the envelope of irc 10216 |
| topic | Astrochemistry Evolved stars Circumstellar envelopes Interstellar molecules Radio astronomy Asymptotic giant branch stars |
| url | https://doi.org/10.3847/2041-8213/ad0899 |
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