# # Program information file # PROGRAM_ID 2021B085 PROGRAM_TITLE Transit Spectroscopy of a Planet around a Nearby Bright Young Star PROGRAM_INV1 Eric Gaidos PROGRAM_INV2 Rena Lee PROGRAM_INV3 Teruyuki Hirano PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT extra-solar planets PROGRAM_ABSTRACT_BEG We propose iSHELL observations of a bright [V=6.9] solar-type member of the 400-Myr Ursa Majoris stellar association. This star hosts two transiting planets that were recently discovered in data from the TESS mission. The inner planet has a radius of 2.1 Earth radii and lies immediately above a gap or 'valley' in the exoplanet radius distribution that separates rocky 'super-Earth' planets with Neptune-like planets possessing H/He-rich envelopes that greatly enlarge their radii. The 'valley' is thought to be the product of escape of those envelopes and the reduction in the planet radius. Because of the young age of the system, atmospheric escape from this planet could be ongoing, and because of the brightness of the host star, it is an ideal candidate to search for evidence of such escape by transit spectroscopy. We propose to search for transit-associated absorption at 1.083 microns by neutral He in the metastable triplet state, as we have recently done for planets orbiting other stars in young stellar groups. We will also better constrain the obliquity of the star relative to the planet's orbital plane by searching for the Doppler 'shadow' of the planet in spectral line shape as it transits the disk of the rapidly rotating star. Our observations will test current scenarios for the early evolution of the thousands of exoplanets detected by the Kepler mission. PROGRAM_ABSTRACT_END