# # Program information file # PROGRAM_ID 2024B045 PROGRAM_TITLE Understanding Ultracool Dwarf Atmospheres Using Color Outliers PROGRAM_INV1 Austin Rothermich PROGRAM_INV2 Jacqueline Faherty PROGRAM_INV3 Genaro Suarez PROGRAM_INV4 Les Hamlet PROGRAM_INV5 Emily Calamari PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG Ultracool dwarfs, objects with temperatures below ~2,700 K, serve as ideal analogs to directly imaged exoplanets, with the added advantage of lacking a bright contaminating host star. There have been significant advancements in the understanding of low temperature atmospheres, however there remain challenges in modeling the effects of clouds, metallicity, and surface gravity on the observed spectral energy distributions of ultracool dwarfs. By studying sources which represent the extremes of these properties [e.g. the youngest/oldest, cloudiest/cloudless] it is possible to better understand the effects these properties have. Younger, cloudier objects have been shown to present redder near-infrared colors than their field age counterparts, whereas the oldest objects typically have bluer colors. These color outliers therefore represent the best objects to study in order to begin understanding and untangling the interplay between these properties in the atmospheres of ultracool dwarfs. In this IRTF proposal, we propose to obtain near infrared spectra of 36 unusually red and blue brown dwarfs which bookmark the extremes of atmosphere, metallicity and gravity properties. With a moderate S/N of 20-30, we will be able to confirm the ultracool dwarf nature of the objects, as well as search for spectral features indicative of age, metallicity, and atmospheric conditions PROGRAM_ABSTRACT_END