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 o 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 ∗ >1.5 M o) of the form , finding α = -2.4 +0.8 and β = -2.0 +0.5, and an integrated occurrence rate of % between 5-13M Jup and 10-100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with % of stars hosting a brown dwarf companion between 13-80M Jup and 10-100 au. 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.
instrumentation: adaptive optics, planetary systems, planets and satellites: detection
© 2019. The American Astronomical Society.
Nielsen, Eric L.; De Rosa, Robert J.; Macintosh, Bruce; Wang, Jason J.; Ruffio, Jean Baptiste; Chiang, Eugene; Marley, Mark S.; Saumon, Didier; Savransky, Dmitry; Mark Ammons, S.; Bailey, Vanessa P.; Barman, Travis; Blain, Célia; Bulger, Joanna; Burrows, Adam; Chilcote, Jeffrey; Cotten, Tara; Czekala, Ian; Doyon, Rene; Duchene, Gaspard; Esposito, Thomas M.; Fabrycky, Daniel; Fitzgerald, Michael P.; Follette, Katherine B.; Fortney, Jonathan J.; Gerard, Benjamin L.; Goodsell, Stephen J.; Graham, James R.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hinkley, Sasha; Hirsch, Lea A.; Ward-Duong, Kimberly; and al, et, "The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 To 100 Au" (2019). Astronomy: Faculty Publications, Smith College, Northampton, MA.