Caltech/IPAC Lunch Seminar

Mapping young exoplanet demographics is crucial for explaining the diversity seen in mature planetary systems. However, high levels of stellar magnetic activity in youth can severely impede characterizing young exoplanets, particularly when using radial velocities to measure planet masses. I will present an intensive observing campaign to measure the mass of the Jupiter-sized IRAS 04125+2902 b, which is the youngest known transiting planet (3 Myr). Observations include high cadence photometry and NIR spectroscopy (Habitable-zone Planet Finder) which can be combined to separate the stellar activity signal from the planet's Doppler signal in radial velocities. I will showcase the long-term stability of the stellar activity signal, indicating long-lived surface active regions that are easy to model using Gaussian processes to capture the temporally coherent noise. The 90% mass limit is 35 Earth masses (0.11 Jupiter masses), a ~30% reduction from the current literature estimate. While IRAS 04125+2902 b is Jupiter-sized, it is very low density and likely a progenitor of a sub-Saturn or even a sub-Neptune.