Molecules of non-photospheric origin in red giants and supergiants revealed by the ISO SWS

T. Tsuji, K. Ohnaka, W. Aoki, I. Yamamura

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Overall SEDs based on ISO SWS observations show fair agreement with photospheric model predictions for red (super)giant stars. However, some details of molecular spectra cannot be explained by a photospheric origin. In particular, fine structure in the H2O 2.μm band can be clearly resolved by the SWS and is identified in an early M giant, whose photosphere will never produce H2O. This is definite evidence for H2O of non-photospheric origin in an early M giant. Also, the observed H2O and CO2 bands in a late M giant are too strong to be explained by a photospheric origin alone. Further, the H2O 2.7μm band is found in four early M supergiants in the h + χ Persei clusters (three of which show UIRs) and is especially strong in the M4 supergiant S Per (which also shows a highly peculiar SED). Thus, against a belief that H2O is found only in the latest M giants such as Miras, the SWS has revealed the presence of H2O in a wider region of the HR diagram. The origin of this H2O is unknown but is probably in a non-photospheric extra envelope. Such a H2O envelope appears to be a general feature through early M (super)giants to cool supergiants such as S Per, where the envelope has finally developed to be optically thick.

Original languageEnglish
Pages (from-to)293-298
Number of pages6
JournalAstrophysics and Space Science
Issue number1-2
Publication statusPublished - 1997
Externally publishedYes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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