The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au
Burrows, Adam; Fortney, Jonathan J.; Duchêne, Gaspard; Esposito, Thomas M.; Hom, Justin; Oppenheimer, Rebecca; Kalas, Paul; De Rosa, Robert J.; Fitzgerald, Michael P.; Hinkley, Sasha; Lee, Eve J.; Macintosh, Bruce; Metchev, Stanimir; Millar-Blanchaer, Maxwell A.; Nielsen, Eric L.; Pueyo, Laurent; Rantakyrö, Fredrik T.; Soummer, Remi; Barman, Travis; Graham, James R.; Hirsch, Lea A.; Marley, Mark S.; Song, Inseok; Czekala, Ian; Marchis, Franck; Schneider, Adam C.; Wolff, Schuyler; Sivaramakrishnan, Anand; Marois, Christian; Saumon, Didier; Chilcote, Jeffrey; Ward-Duong, Kimberly; Wang, Jason J.; Bailey, Vanessa P.; Morzinski, Katie M.; Ammons, S. Mark; Ren, Bin; Chiang, Eugene; Follette, Katherine B.; Bulger, Joanna; Cotten, Tara; Doyon, Rene; Goodsell, Stephen J.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hung, Li-Wei; Ingraham, Patrick; Konopacky, Quinn; Larkin, James E.; Maire, Jérôme; Palmer, David; Patience, Jennifer; Poyneer, Lisa; Rajan, Abhijith; Rameau, Julien; Savransky, Dmitry; Thomas, Sandrine; Gerard, Benjamin L.; Perrin, Marshall; Ruffio, Jean-Baptiste; Tallis, Melisa; Fabrycky, Daniel; Blain, Célia; Dawson, Rebekah Ilene; Lin, Jonathan W.; Rafikov, Roman R.
United States, Canada, France, Chile, United Kingdom, Netherlands
Abstract
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 ⊙ 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 ⊙) of the form {d}2N/({dm} {da})\propto {m}α {a}β , 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 10-100 au. 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 10-100 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.