Constraining the Masses of Two Mini-Neptunes orbiting M Dwarfs using HPF

We present the validation of two exoplanets orbiting M dwarfs identified by TESS. Both planets are mini-Neptunes orbiting nearby M dwarfs, making them promising prospects for atmospheric characterization with the James Webb Space Telescope (JWST). We validated the planetary nature of both using Adaptive Optics (AO) imaging, ground based photometry, and radial velocities. Radii and orbital ephemerides were refined using a combination of TESS, the 3.5 m Apache Point Telescope’s optical CCD camera ARCTIC, and the 0.6 m telescope at the Red Buttes Observatory (RBO). Radial velocities were obtained using the near-infrared Habitable Zone Planet Finder (HPF) spectrometer on the 10 m Hobby-Eberly Telescope, which enabled us to place upper limits on the masses of both transiting planets. The first planet has a radius between that of Earth and Neptune, placing it in a sparsely-populated region of parameter space considering its host star’s temperature, as planets of its size are quite rare around late M dwarfs. The second planet is an excellent candidate for the possible detection of a unique type of biosignature made by combining Hydrogen and Nitrogen to make Ammonia.