Detection of fine-structure line emission from carbon-rich and oxygen-rich AGB stars by the ISO SWS

W. Aoki, T. Tsuji, K. Ohnaka

Research output: Contribution to journalReview articlepeer-review

10 Citations (Scopus)

Abstract

We detected five forbidden lines of iron, silicon and sulfur in red giants by the ISO SWS. [Fe I] 24 μm emission was detected in two carbon stars, TX Psc and WZ Cas, and [S I] 25.2μm emission was also detected in TX Psc, while none of these emission lines were detected in an oxygen-rich giant, 30g Her. On the other hand, the [Fe II] 26μm, [Si II] 34.8μm and [Fe II] 35.3 μm emission lines were detected in the spectrum of 30g Her, while only [Fe II] 26 μm was detected in TX Psc. Namely the emission lines of neutral metals were detected in carbon stars while the lines of ions were detected in an oxygen-rich giant. This result suggests that the ionization states of metals in the outer atmosphere as well as the ultraviolet radiation field of carbon stars are different from those of M giants. We estimate that the mass of the line forming region is several × 10-6M and the temperature is several hundred Kelvin or higher. This implies that there is a rather dense and warm region close to the star in addition to the well known expanding envelope.

Original languageEnglish
Pages (from-to)L19-L22
JournalAstronomy and Astrophysics
Volume333
Issue number2
Publication statusPublished - 1998
Externally publishedYes

Keywords

  • Infrared: stars
  • Stars: AGB and post-AGB
  • Stars: chromospheres
  • Stars: circumstellar matter
  • Stars: late-type
  • Stars: mass-loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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