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The nature of dust around the post-asymptotic giant branch objects HD 161796 and HD 179821

JUSTTANONT, K; BARLOW, MJ; SKINNER, CJ; TIELENS, A; (1992) The nature of dust around the post-asymptotic giant branch objects HD 161796 and HD 179821. Astrophysical Journal , 392 (2) L75-L78. 10.1086/186429. Green open access

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Abstract

Ground-based 7.4-24-micron spectra of two post-AGB objects, HD 161796 and HD 179821, are reported, and they are compared to those of other preplanetary nebulae. HD 161796 and HD 17982 show emission features at 10-12 microns and at 10 microns, and they exhibit a very rapid increase in flux between 13 and 15.5 microns. In view of the O-rich photosphere of HD 161796 and the presence of OH maser emission around all three objects, these features are ascribed to various oxides. The observed spectral features are quite different from the canonical silicate features observed in most O-rich giants. It is argued that HD 161796 and the bipolar nebulae Roberts 22 and NGC 6302 have all undergone the third dredge-up, with most of the dredged-up carbon having been converted to nitrogen by envelope-burning. It is concluded that carbon-rich grain material, produced during the interval between the end of the third dredge-up and the moment when envelope burning finally reduced the C/O ratio below unity again, could be responsible for the UIR bands now being excited in Roberts 22 and NGC 6302.

Type: Article
Title: The nature of dust around the post-asymptotic giant branch objects HD 161796 and HD 179821
Open access status: An open access version is available from UCL Discovery
DOI: 10.1086/186429
Publisher version: https://doi.org/10.1086/186429
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Asymptotic Giant Branch Stars; Cosmic Dust; Infrared Stars; Interstellar Matter; Supergiant Stars; Infrared Astronomy Satellite; Interstellar Masers; Iron Oxides; Olivine; Silicates; Stellar Composition; Astrophysics; STARS: CIRCUMSTELLAR MATTER; ISM: DUST; EXTINCTION; INFRARED: STARS; STARS: SUPERGIANTS
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10096202
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