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dc.contributor.authorSpeck, Angela K.eng
dc.contributor.authorHofmeister, Anne M.eng
dc.date.issued2004eng
dc.descriptiondoi: 10.1086/379973eng
dc.description.abstractSome proto-planetary nebulae (PPNs) exhibit an enigmatic feature in their infrared spectra at ~21 μm. This feature is not seen in the spectra of either the precursors to PPNs, the asymptotic giant branch (AGB) stars, or the successors of PPNs, "normal" planetary nebulae (PNs). However, the 21 μm feature has been seen in the spectra of PNs with Wolf-Rayet central stars. Therefore, the carrier of this feature is unlikely to be a transient species that only exists in the PPN phase. This feature has been attributed to various molecular and solid-state species, none of which satisfy all constraints, although titanium carbide (TiC) and polycyclic aromatic hydrocarbons (PAHs) have seemed the most viable. We present new laboratory data for silicon carbide (SiC) and show that it has a spectral feature that is a good candidate for the carrier of the 21 μm feature. The SiC spectral feature appears at approximately the same wavelength (depending on the polytype/grain size) and has the same asymmetric profile as the observed astronomical feature. We suggest that processing and cooling of the SiC grains known to exist around carbon-rich AGB stars are responsible for the emergence of the enigmatic 21 μm feature. The emergence of this feature in the spectra of post-AGB stars demonstrates the processing of dust due to the changing physical environments around evolving stars.eng
dc.description.sponsorshipA. M. H. was supported by NSF AST 98-05924.eng
dc.identifier.citationAngela K. Speck and Anne M. Hofmeister 2004 ApJ 600 986eng
dc.identifier.issn0004-637Xeng
dc.identifier.urihttp://hdl.handle.net/10355/9937eng
dc.languageEnglisheng
dc.publisherInstitute of Physicseng
dc.relation.ispartofcollectionUniversity of Missouri--Columbia. College of Arts and Sciences. Department of Physics and Astronomy. Physics and Astronomy publicationseng
dc.subject.lcshCosmochemistryeng
dc.subject.lcshCircumstellar mattereng
dc.subject.lcshAsymptotic giant branch starseng
dc.subject.lcshMass loss (Astrophysics)eng
dc.titleProcessing of Presolar Grains around Post-Asymptotic Giant Branch Stars: Silicon Carbide as the Carrier of the 21 Micron Featureeng
dc.typeArticleeng


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