摘要：We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey. This subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semimajor axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M * >1.5 M e more likely to host planets with masses between 2 and 13M Jup and semimajor axes of 3–100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semimajor axis (a) for planet populations around high-mass stars (M * >1.5M e ) of the form d N dm da m a 2 µ a b ( ) , finding α=−2.4±0.8 and β=−2.0±0.5, and an integrated occurrence rate of 9 4 5 - + % between 5–13M Jup and 10–100au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.8 0.5 0.8 - + % of stars hosting a brown dwarf companion between 13–80M Jup and 10–100au. Brown dwarfs also appear to be distributed differently in mass and semimajor axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semimajor axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the radial velocity method, our results are consistent with a peak in occurrence of giant planets between ∼1 and 10 au. We discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability.
关键词：instrumentation: adaptive optics;planetary systems;planets and satellites: detection
