The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au

Eric L. Nielsen , Robert J. de Rosa , Bruce Macintosh , Jason J. Wang , Jean-Baptiste Ruffio , Eugene Chiang , Mark S. Marley , Didier Saumon , Dmitry Savransky , S. Mark Ammons , Vanessa P. Bailey , Travis Barman , Célia Blain , Joanna Bulger , Adam Burrows , Jeffrey Chilcote , Tara Cotten , Ian Czekala , Rene Doyon , Gaspard Duchêne (1) , Thomas M. Esposito , Daniel Fabrycky , Michael P. Fitzgerald , Katherine B. Follette , Jonathan J. Fortney , Benjamin L. Gerard , Stephen J. Goodsell , James R. Graham , Alexandra Z. Greenbaum , Pascale Hibon , Sasha Hinkley , Lea A. Hirsch , Justin Hom , Li-Wei Hung , Rebekah Ilene Dawson , Patrick Ingraham , Paul Kalas , Quinn Konopacky , James E. Larkin , Eve J. Lee , Jonathan W. Lin , Jérôme Maire , Franck Marchis , Christian Marois , Stanimir Metchev , Maxwell A. Millar-Blanchaer , Katie M. Morzinski , Rebecca Oppenheimer , David Palmer , Jennifer Patience , Marshall Perrin , Lisa Poyneer , Laurent Pueyo , Roman R. Rafikov , Abhijith Rajan , Julien Rameau , Fredrik T. Rantakyrö , Bin Ren , Adam C. Schneider , Anand Sivaramakrishnan , Inseok Song , Remi Soummer , Melisa Tallis , Sandrine Thomas , Kimberly Ward-Duong , Schuyler Wolff

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

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.

Keywords: instrumentation: adaptive optics; planetary systems; planets and satellites: detection; Astrophysics - Earth and Planetary Astrophysics

Domains: Sciences of the Universe [physics]

Eric L. Nielsen, Robert J. de Rosa, Bruce Macintosh, Jason J. Wang, Jean-Baptiste Ruffio, et al.. The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au. The Astronomical Journal, 2019, 158, ⟨10.3847/1538-3881/ab16e9⟩. ⟨insu-03703851⟩