Princeton University Extrasolar Planet Discussion Group

Stellar and substellar companions are thought to play a crucial role in shaping the formation and migration of the inner planets. However, the 3D orbital architecture of these systems, including the mutual inclination between inner planets and outer companions, are largely unexplored. In this talk, I will describe our survey of planetary and stellar companions to transiting planet hosts with significant Hipparcos-Gaia astrometric acceleration. Specifically, I will highlight the discovery of a long-period giant planet HD 118203 c exterior to a close-in eccentric hot Jupiter. Our results are consistent with a system-wide alignment, with the outer giant planet displaying low mutual inclination relative to both the inner hot Jupiter and the host star’s spin axis. This alignment, along with the moderate eccentricity of HD 118203 c, implies that the system may have historically undergone coplanar high-eccentricity tidal migration. 

Habitable Worlds Observatory (HWO) aims to observe at least 25 habitable planets, with the goal of searching for chemical “biosignatures” in their atmospheres. While integral field spectrographs (IFS) are commonly used for exoplanet spectroscopy, detector noise poses challenges when observing faint targets like Earth-like planets. In the second half of this talk, I will explore an alternative instrument concept of imaging Fourier transform spectrographs (iFTS), which is less sensitive to detector noise in principle. Our study shows encouraging results for HWO in the near-IR wavelengths that an iFTS would be more efficient with the state-of-art detectors. Our results also highlight the need for developments to reduce detector noise to achieve the goal of spectrally characterizing habitable planets.