Confirmation of Hot Jupiter Re-Inflation

Hot Jupiters are a type of gas giant exoplanet that have a mass similar to Jupiter and short (<10 days) orbital periods. Some hot Jupiters have a larger radius than is predicted by planetary evolution models. The causes of hot Jupiter inflation have been debated for over 20 years, but in general can be classified into two mechanisms of inflation, class I and class II. Class I inflation states that as a hot Jupiter’s host star evolves, the planet can become re-inflated by the star’s increased irradiation, causing its radius to increase. Class II inflation states that the planet was already inflated during formation and continues to slowly cool as the host star’s irradiation keeps it warm. Using data from Kepler, Spitzer and Keck, we better constrained the mass and radius of one hot Jupiter, K2-97b, and are working towards constraining the mass and radius of another hot Jupiter, K2-132b. These measurements determine if these planets have been re-inflated by class I inflation or were inflated after their formation by class II inflation. We measured the mass and radius of K2-97b to be 0.49 ± 0.03 M_J and 1.63 ± 0.1 R_J, respectively. This indicates that K2-97b is very likely inflated by class I inflation. We are measuring the mass and radius of K2-132b currently and plan to present results for these values as well as determine from this data by which mechanism this planet has been inflated. Determining this mechanism will not only help in our understanding of planetary inflation but will also be an important step forward in understanding planet atmospheres and their evolution.