JWST Imaging of the Closest Globular Clusters -- III. Multiple Populations along the low-mass Main Sequence stars of NGC 6397

Abstract: Thanks to its exceptional near-infrared photometry, JWST can effectively contribute to the discovery, characterization, and understanding of multiple stellar populations in globular clusters, especially at low masses where the Hubble Space Telescope (HST) faces limitations. This paper continues the efforts of the JWST GO-1979 program in exploring the faintest members of the globular cluster NGC 6397. Here we show that the combination of HST and JWST data allows us to identify two groups of MS stars (MSa, the first-generation, and MSb, the second-generation group). We measured the ratio between the two groups and combined it with measurements from the literature focused on more central fields and more massive stars compared to our study. We find that the MSa and MSb stars are present in a $\approx$30-70 ratio regardless of the distance from the centre of the cluster and the mass of the stars used so far.