Elemental composition guides the formation, evolution, and atmosphere processes of the lowest-mass stars and brown dwarfs, or ultracool dwarfs (UCDs). While the vast majority of known UCDs are solar-metallicity objects in the Milky Way's thin disk, a rare subsample of metal-poor stellar and substellar subdwarfs are known in the Solar Neighborhood

In main-sequence, low-mass (<1.3 Solar mass) stars, rotation and magnetic activity decrease over time, with the spin-down thought to be due to angular momentum lost through magnetized winds. This magnetic activity heats the stellar atmospheres, leading to the production of Hα, ultraviolet (UV), and X-ray radiation, each originating from different

The relation between nuclear star clusters (NSCs) and the growth of the central supermassive black holes (SMBHs), as well as their connection to the properties of the host galaxies, is crucial for understanding the evolution of galaxies. Recent observations have revealed that about 10% of nucleated galaxies host hybrid nuclei, consisting of both