Chemical abundances in the globular clusters M3, M13, and NGC 6752

Abstract

view Abstract Citations (69) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Chemical abundances in the globular clusters M 3, M 13, and NGC 6752. Bell, R. A. ; Dickens, R. J. Abstract The abundances of iron, carbon, nitrogen, and oxygen have been investigated in red giant stars in the globular clusters M3, M13, and NGC 6752. The results are based on application of spectrum synthesis and theoretical colors to observed spectra, DDO colors, and infrared CO measurements. Carbon is depleted by a factor of about 3 relative to other metals in most giants studied, with no evidence for the discontinuity along the giant branch at a visual magnitude of approximately -0.7 found for more metal-poor clusters. This contrasts with the greater depletion of about a factor of 6 for the more metal-poor cluster stars, a difference which is expected if meridional mixing is responsible for the carbon depletion. The spectroscopic results for nitrogen are imprecise, but the colors suggest enhancements of a factor of 3. The iron abundances for M3 and M13 stars have been determined from published equivalent widths, yielding Fe/H concentration ratios close to -1.4 for both clusters. The uncertainties in M3 and M13 CO colors and forbidden O I equivalent widths make it impossible to derive accurate oxygen abundances, but the depletion of carbon is real and is not caused by an overabundance of oxygen. Publication: The Astrophysical Journal Pub Date: December 1980 DOI: 10.1086/158502 Bibcode: 1980ApJ...242..657B Keywords: Abundance; Globular Clusters; Red Giant Stars; Stellar Spectrophotometry; Carbon; Carbon Monoxide; Depletion; Graphs (Charts); Iron; Line Spectra; Nitrogen; Oxygen Spectra; Stellar Spectra; Stellar Temperature; Astrophysics full text sources ADS |