Are TiC grains a carrier of the 21 micron emission band observed around post-asymptotic giant branch objects?

Takeshi Chigai, Tetsuo Yamamoto, Chihiro Kaito, Yuki Kimura

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The carrier of the 21 μm band observed in post-asymptotic giant branch (post-AGB) stars is examined. We analyze the infrared spectra of the TiC clusters measured by von Helden et al. in 2000 and determine the absorption efficiency Q in the 21 μm band. Using Q, we estimate the Ti/Si abundance ratios needed to realize the flux ratios of the 21 and 11 μm emission observed in the infrared spectra of the post-AGB stars exhibiting both 21 and 11 μm emission. In view of the nature of the TiC condensation by which TiC grains are quickly mantled by graphite, we calculate the emission spectra of the graphite-coated TiC grains and other possible types of core-mantle grains and compare with the observed spectra. Both the abundance and condensation considerations strongly suggest that TiC is an implausible carrier of the observed infrared 21 μm feature around carbon-rich post-AGB stars.

Original languageEnglish
Pages (from-to)771-776
Number of pages6
JournalAstrophysical Journal
Volume587
Issue number2 I
DOIs
Publication statusPublished - 2003 Apr 20

Keywords

  • Circumstellar matter
  • Dust, extinction
  • Stars: mass loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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