Astrophysics and Space Science

, Volume 94, Issue 2, pp 295–305 | Cite as

Pi Gruis: Molecular identifications and spectral classification

  • P. S. Murty


Identifications of the molecular absorption features in the visible spectrum of the S star Pi Gruis are presented. Moderate dispersion spectrum of π1 Gru covering the region 5800–7300 Å, demonstrates the presence of a multitude of molecular bands. Wavelength measures of well over 150 red-degraded band heads are listed. Nearly 80% of the observed features are identified with the ZrO, LaO, YO, and CeO molecules. Many molecular bands due to ZrO, YO, and CeO are reported identified for the first time. Neither TiO molecular features nor any Ba compounds are detectable.

As a consequence of the presence of bands due tos-process oxides and the absence of TiO bands, π1 Gru may be classified as a pure S star. Observed predominance of the ZrO molecule suggests that both the phenomenon of Zr abundance enhancements and chemical equilibrium conditions with a carbon/oxygen ratio between 0.95 and 1.0 may be at play in the atmospheres of cooler pure S stars.


Chemical Equilibrium Condition Absorption Feature Molecular Feature Chemical Equilibrium Visible Spectrum 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© D. Reidel Publishing Co 1983

Authors and Affiliations

  • P. S. Murty
    • 1
  1. 1.Indian Institute of AstrophysicsKodaikanalIndia

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