Long-Term Near-Infrared Compound Variability of Three Recently Discovered Brown Dwarfs in IC 348 and NGC 1333

While much is known about stars, less is known about brown dwarfs: cool, low-mass, substellar byproducts of star formation. Studying the photometric behavior of brown dwarfs is an important strategy to better understand their dynamics as well as their atmospheric and intrinsic features. We positionally matched two United Kingdom Infrared Telescope (UKIRT) observing campaigns in the Perseus region to previously published brown dwarf catalogs and established the presence of 10 and 6 sources with reported spectral types of M6 or later in IC 348 and NGC 1333, respectively. We assessed the long-term (≳8 month) near-infrared (J, H, and K band) variability of these 16 sources by analyzing their individual reduced chi-squared values, their Stetson indices, and their periodicity, and found two variable brown dwarfs in IC 348—one of which is a periodic variable—and one in NGC 1333. We propose three different explanations for the observed periodicity and variability by drawing upon current literature. This paper is a companion paper to Rice et al. (2025, in prep).