When Does the Onset of Multiple Stellar Populations in Star Clusters Occur? III. No Evidence of Significant Chemical Variations in Main-sequence Stars of NGC 419

• Published in: The Astrophysical journal Vol. 893; no. 1; pp. 17 - 24
• Main Authors: Li, Chengyuan, Wang, Yue, Tang, Baitian, Milone, Antonino P., Yang, Yujiao, Ji, Xin
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 10.04.2020; IOP Publishing
• Subjects: Astrophysics; G dwarf stars; Globular star clusters; Hertzsprung Russell diagram; Hubble Space Telescope; K dwarf stars; Main sequence stars; Morphology; Nitrogen; Space telescopes; Star clusters; Stars; Stars & galaxies; Stellar age; Stellar evolution; Stellar populations
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab7b64

Recent studies have revealed that the onset age for the presence of multiple stellar populations (MPs) in star clusters seems to correspond to the disappearance of the extended main-sequence turnoff in young clusters, a pattern associated with stellar rotations. A speculative suggestion is that MPs might be caused by the magnetic brake, a stellar evolutionary effect linked to rotation. In this work, we use the young massive cluster NGC 419 as a testbed. We examined if its magnetically baked MS stars would exhibit MPs. Using the deep ultraviolet and visible images observed through the Hubble Space Telescope, combined with a specific color index that is sensitive to the nitrogen (N) abundance, we examined if its late G- and K-type MS stars are affected by N variation. Our analysis reports that the morphology of its GK-type MS is most likely a simple stellar population, and only a negligible probability, which indicates a N variation up to 0.4 dex is present. We therefore conclude that there is no significant N variation among its GK-type MS stars. The absence of a significant chemical variation among the late-type MS stars indicates that MPs might not be a specific pattern of magnetically braked stars.