Exotic Carbon Chemistry in a Planetary Nebula: The Unusual Case of K4-47
AffiliationUniv Arizona, Dept Chem & Biochem
Univ Arizona, Dept Astron & Steward Observ
nuclear reactions, nucleosynthesis, abundances
planetary nebulae: individual (K4-47)
radio lines: ISM
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PublisherIOP PUBLISHING LTD
CitationD. R. Schmidt and L. M. Ziurys 2019 ApJL 881 L38
JournalASTROPHYSICAL JOURNAL LETTERS
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractMillimeter molecular line observations have been conducted toward the young (similar to 900 yr) bipolar planetary nebula (PN) K4-47, using the 12 m antenna and the Submillimeter Telescope of the Arizona Radio Observatory, and the Institut de Radioastronomie Millimetrique 30 m Telescope. Measurements at 1, 2, and 3 mm of multiple transitions were carried out to ensure the accuracy of all molecular identifications. K4-47 was found to be unusually chemically rich, containing three complex species, CH3CN, H2CNH, and CH3CCH, which have never before been observed in a planetary nebula. In addition, HC3N, N2H+, H2CO, c-C3H2, and SiO have been identified in this object, as well as a variety of C-13-substituted isotopologues ((H2CO)-C-13, c-(CCCH2)-C-13, c-(CCCH2)-C-13, (CH3CN)-C-13, (CH3CN)-C-13, (CH3CCH)-C-13, and (CH3CCH)-C-13), including all three doubly C-13-substituted varieties of HC3N-the first known object in which all three species have been detected. After CO and H-2, the most abundant molecules in K4-47 are CCH and CN, which have abundances of f similar to 8 x 10(-7), relative to molecular hydrogen. Surprisingly, the next most abundant molecule is CH 3 CCH, which has f similar to 6 x 10(-7), followed by HCN with an abundance of similar to 5 x 10(-7). The results suggest that K4-47 is the most chemically complex planetary nebula currently known. The molecular content of K4-47 closely resembles that of the C-star IRC+10216, but with lower abundances, except for HCO+, H2CO, and CH3CCH. The PN also chemically and morphologically resembles the bipolar protoplanetary nebula CRL 618, with similar enrichments of C-13, N-15, and O-17, suggestive of an explosive process at the end of the asymptotic giant branch.
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