# # Program information file # PROGRAM_ID 2021A054 PROGRAM_TITLE Measuring the carbon-to-oxygen ratio of the exo-Neptune HAT-P-26b PROGRAM_INV1 Megan Mansfield PROGRAM_INV2 Jacob Bean PROGRAM_INV3 Michael Line PROGRAM_INV4 Joe Zalesky PROGRAM_INV5 Matteo Brogi PROGRAM_SCICAT extra-solar planets PROGRAM_ABSTRACT_BEG A primary goal of exoplanet observations has been to constrain their formation and migration histories through the measurement of the carbon-to-oxygen [C/O] ratio. However, precisely measuring this ratio has been difficult with space-based observations because it requires resolved observations of both carbon- and oxygen-bearing species. We propose here to use the iSHELL instrument on IRTF to observe CO, CH4, and H2O in the atmosphere of the exo-Neptune HAT-P-26b. Combined with previous Hubble Space Telescope [HST] observations of H2O on HAT-P-26b, this will provide a tight constraint on the planet's C/O ratio. We have previous or planned iSHELL observations of two other exoplanets, WASP-107b and GJ 3470b, and we will compare observations of HAT-P-26b to these two planets to look for trends in their molecular abundances that may indicate similar or divergent formation pathways. PROGRAM_ABSTRACT_END