Astronomy and Astrophysics – Astronomy
Scientific paper
May 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987aj.....93.1137w&link_type=abstract
Astronomical Journal (ISSN 0004-6256), vol. 93, May 1987, p. 1137-1143.
Astronomy and Astrophysics
Astronomy
44
Charge Coupled Devices, Globular Clusters, Spectrum Analysis, Stellar Spectra, Cn Emission, Metallicity, Red Giant Stars, Stellar Composition, Wolf-Rayet Stars
Scientific paper
The authors have used spectra of 0.3 and 0.6 Å resolution of stars in M4, M13, and M22 to derive abundances of various atomic species and the CN molecule. For M13, they find the usual Fe/H ratio and a surprisingly high aluminum abundance. The CN lines indicate a larger column density in the oxygen-rich star III-63 than in the oxygen-poor star II-67 by a factor of 10. For M4, they find [Fe/H] = -1.2 using solar f values derived via the BEGN model. This Fe abundance lies between earlier echelle values and photometric values. Na, Al, Si, Ca, and, possibly, Ti are all in excess relative to iron. V, Ni, and Zr show similar or possibly slightly greater deficiencies than iron. For two stars, the authors have CN data that can be understood if there was a slight excess of C/Fe and N/Fe prior to CN cycling and mixing. For M22, they find a large difference in CN between stars III-3 and IV-102. The authors discuss the origin of the CNO elements in terms of mass loss from an early generation of red giants and possibly Wolf-Rayet stars.
Leep Myckky E.
Oke Bev J.
Wallerstein George
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