Studies of evolved stars. IV. Band strength ratios as indicators of mixing in M, MS and S stars.

Abstract

view Abstract Citations (40) References (71) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Studies of evolved stars. IV. Band strength ratios as indicators of mixing in M, MS, and S stars. Scalo, J. M. Abstract Evidence is presented which indicates that many apparently normal cool giants have undergone mixing between the stellar interior and the surface. The results are based on a comparison of chemical equilibrium calculations with published band strengths of YO, ScO, TiO, CO, and CN, and are supported by observations of anomalous isotopic ratios and the presence of technetium in several such stars. Methods for distinguishing between two general mixing mechanisms are discussed. The available evidence suggests that 3e carbon has been added to the envelopes of at least some M and S stars. It is also concluded that the ClO ratio in S stars is greater than 0.96, if the oxygen abundance is solar, and that the strong CN bands observed in S stars can be understood as a result of an increase in ClO, without large nitrogen enhancements. A number of molecular bandstrength ratios which could be measured in the blue and visual regions of the spectrum are suggested for detection of ClO variations in M giants. Subject headings: abundances, stellar - late type stars - long-period variables - molecules - S-type stars Publication: The Astrophysical Journal Pub Date: December 1974 DOI: 10.1086/153253 Bibcode: 1974ApJ...194..361S full text sources ADS | data products SIMBAD (12) Related Materials (4) Part 1: 1973ApJ...183..151S Part 2: 1973ApJ...184..801S Part 3: 1974ApJ...192..507U Part 5: 1975ApJ...196..805S