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
  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 (eMSTO) 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 the 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 an SSP, and only a negligible probability that
indicates a N variation up to 0.4 dex is present. We 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.
