Carbon and nitrogen abundances in the giant stars of the globular clusters M3 and M13

Abstract

view Abstract Citations (200) References (49) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Carbon and nitrogen abundances in the giant stars of the globular clusters M 3 and M 13. Suntzeff, N. B. Abstract Carbon and nitrogen abundances were measured in about 30 red giants in each of the two clusters M3 and M13, by comparing the low-resolution 10 A fluxed spectra of the NH and CH regions with synthetic spectra. In both clusters, evidence is found of the mixing of CN-processed material into the red giant atmospheres, and that such mixing is a function of the evolutionary state of the red giant. The combination of measured carbon and nitrogen abundances with published abundances of oxygen for the two clusters shows that the difference in Z(CNO) between the two clusters is too small to account for the difference in horizontal branch morphologies. It is instead proposed that M13 stars rotate faster than M3 stars, on the average, and may mix up CN-processed material at lower luminosities either on the subgiant branch or on the main sequence. Increased M13 core rotation would create the bluer HB observed in M13, and account for the extreme carbon depletion in a few of the M13 asymptotic giant branch stars. Publication: The Astrophysical Journal Supplement Series Pub Date: September 1981 DOI: 10.1086/190750 Bibcode: 1981ApJS...47....1S Keywords: Abundance; Carbon; Globular Clusters; Nitrogen; Red Giant Stars; Asymptotic Giant Branch Stars; Cyanogen; Red Shift; Stellar Atmospheres; Stellar Evolution; Stellar Luminosity; Stellar Rotation; Stellar Spectra; Stellar Spectrophotometry; Stellar Structure; Astrophysics full text sources ADS | data products SIMBAD (7)