247.09 - First Exoplanet Mass Measurements from NASA Keck Key Strategic Mission Support Program Challenge the Core Accretion Theory

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Jan 8th at 9:00 AM until 10:00 AM

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Author(s): A. Bhattacharya, Physics, NASA Goddard Space Flight Centre, Adelphi, Maryland, UNITED STATES|D. Suzuki, JAXA, Tokyo, Maryland, JAPAN|A. Bhattacharya, University of Maryland College Park, COLLEGE PARK, Maryland, UNITED STATES|
Institution(s): 1. Physics, NASA Goddard Space Flight Centre, Adelphi, MD, United States. 2. JAXA, Tokyo, Japan. 3. University of Maryland College Park, COLLEGE PARK, MD, United States.
Contributing team(s): Keck KSMS team, MOA, GMRG
The distribution of exoplanets orbiting beyond the snow line found by microlensing indicate a smooth power-law distribution ranging from a super-Jupiter mass ratio of $q = 10^{-2}$ down to close to the mass ratio of Neptune, $q\sim 10^{-4}$, with the $q = 10^{-4}$ planets being 60 times more common than planets with $q = 10^{-2}$. However, the favored core accretion theory predicts a deficit of planets in the 20--80 Earth-mass range, due to the run away gas accretion process that is thought to accrete most of the mass of gas giant planets. This mass range translates into a mass ratio of $q =1$–4$\times 10^{-4}$ at the typical host star mass probed by microlensing, and the microlensing data indicates that there is no gap at this mass ratio range. It is unclear if implies a basic revision of the core accretion theory or if the mass gap exists in the exoplanet mass distribution, but is washed out by the mass distribution of microlens planet host stars. We present the first results of the NASA Keck Key Strategic Mission Support that uses the WFIRST exoplanet mass measurement method to determine the masses of exoplanet host stars and their planets. We use both Keck and HST high angular resolution imaging to determine the masses of microlens host stars and planets from the Suzuki et al. (2016) statistical sample to investigate this predicted planet gap at 20--80 Earth-masses. Our early results reveal several planets with measured mass in this mass range, suggesting that the core accretion may be in need of revision.