The CN-CH positive correlation in the globular cluster NGC 5286

Abstract

We performed low-resolution spectroscopy for the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK' (7.4σ) and CH (5.1σ) indices, while the CN-intermediate stars show no significant difference in the strength of HK' index with CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN- and HK'-strong stars are also enhanced in the abundances of Fe and s-process elements. It appears, therefore, that these stars are later generation stars affected by some supernovae enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN-CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations such as M22 and NGC 6273.

8 pages, 6 figures, 1 table, accepted for publication in ApJ

References in corpus (19)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• The influence of residual gas expulsion on the evolution of the Galactic globular cluster system and the origin of the Population II halo
• Kinematic Decoupling of Globular Clusters with Extended Horizontal-Branch
• Comparing CN and CH Line Strengths in a Homogeneous Spectroscopic Sample of 8 Galactic Globular Clusters
• Probing the IGM/Galaxy Connection Toward PKS0405-123 III: The Galaxy Survey and Correlations with OVI Absorbers
• Gas expulsion vs gas retention: what process dominates in young massive clusters?
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• CN Bimodality at Low Metallicity: The Globular Cluster M53
• Studying the evolution of AGB stars in the Gaia epoch
• Low-resolution Spectroscopy for the Globular Clusters with Signs of Supernova Enrichment: M22, NGC 1851 and NGC 288
• Multiple Populations in Globular Clusters and the Origin of the Oosterhoff Period Groups
• On the metallicity distribution of the peculiar globular cluster M22
• A broad perspective on multiple abundance populations in the globular cluster NGC 1851
• Reversed radial distribution trend of subpopulations in the globular clusters NGC 362 and NGC 6723