Program: GS-2021B-Q-316

The radius gap is a dearth of planets with radii between 1.5 and 2 Earth radii in the large, diverse sample of exoplanets discovered by the TESS and Kepler missions, delineating the boundary between super-Earths and sub-Neptunes. The location of the radius gap may be dependent on host star properties such as stellar mass and metallicity, but the effect of multiplicity on the radius gap is unknown. Planetary radii might be incorecctly measured if the binary's effects on stellar characterization are not robustly accounted for. There are few planets in or near the radius gap, meaning that changes to the radii of those planets can have profound implications for the sample of radius-gap planets. We propose to use GMOS at Gemini for 3.5 hours to observe 5 TESS near-radius-gap close-binary planets to supplement a larger sample of Kepler near-radius-gap binary planets to be observed at the Hobby-Eberly Telescope this trimester. We will use a novel MCMC technique to accurately revise the star (and thus planet) properties, altering the planet radii and possibly moving them in or out of the radius gap.