# # Program information file # PROGRAM_ID 2021A074 PROGRAM_TITLE Spectroscopy of a Bright M Dwarf Exoplanet Host Star as Prelude to JWST PROGRAM_INV1 Eric Gaidos PROGRAM_INV2 James Lyons PROGRAM_INV3 Ian Crossfield PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT extra-solar planets PROGRAM_ABSTRACT_BEG We propose iSHELL observations of the nearby, bright M dwarf GJ 357 to better understand the nature of its close-in super-Earth-size 'b' planet and the origin of the system. Because of its brightness and proximity, this exoplanet system is one of the best known targets for future exoplanet atmospheric studies with mission such as the James Webb Space Telescope. We will obtain K-band spectrum during transit to search for planet-associated absorption in the overtone rovibrational lines of CO indicative of an extended reducing atmosphere. We will combine measurements of the stellar lines of CO with spectra of the fundamental lines in M-band [4.6 microns] to determine the C and O isotopic of the star, a key test of Galactic chemical evolution models and a possible indicator of the provenance and environment of th star's birthplace. PROGRAM_ABSTRACT_END