2025AJ....170..327D

We present our photometric method, which combines Subaru/Hyper Suprime-Cam NB515, g-band, andi-band filters to distinguish giant stars in Local Group galaxies from Milky Way dwarf contamination. The NB515 filter is a narrowband filter that covers the MgI+MgH features at 5150 Å and is sensitive to stellar surface gravity. Using synthetic photometry derived from large empirical stellar spectral libraries, we model the NB515 filter's sensitivity to stellar atmospheric parameters and chemical abundances. Our results demonstrate that the NB515 filter effectively separates dwarfs from giants, even for the reddest and coolest M-type stars. To further enhance this separation, we develop machine learning models that improve the classification on the two-color (g - i, NB515 - g) diagram. We apply these models to photometric data from the Fornax dwarf spheroidal galaxy and two fields of M31, successfully identifying red giant branch stars in these galaxies.