The Gemini Planet Imager Exoplanet Survey : giant planet and brown dwarf demographics from 10 to 100 au
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 13MJup 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 d2N/(dm da) ∝ mα aβ, finding α = −2.4 ± 0.8 and β = −2.0 ± 0.5, and an integrated occurrence rate of 9+5-4% between 5–13MJup and 10–100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.8+0.8-0.5% of stars hosting a brown dwarf companion between 13–80MJup 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.
Citation
Nielsen , E L , De Rosa , R J , Macintosh , B , Wang , J J , Ruffio , J-B , Chiang , E , Marley , M S , Saumon , D , Savransky , D , Ammons , S M , Bailey , V P , Barman , T , Blain , C , Bulger , J , Burrows , A , Chilcote , J , Cotten , T , Czekala , I , Doyon , R , Duchêne , G , Esposito , T M , Fabrycky , D , Fitzgerald , M P , Follette , K B , Fortney , J J , Gerard , B L , Goodsell , S J , Graham , J R , Greenbaum , A Z , Hibon , P , Hinkley , S , Hirsch , L A , Hom , J , Hung , L-W , Dawson , R I , Ingraham , P , Kalas , P , Konopacky , Q , Larkin , J E , Lee , E J , Lin , J W , Maire , J , Marchis , F , Marois , C , Metchev , S , Millar-Blanchaer , M A , Morzinski , K M , Oppenheimer , R , Palmer , D , Patience , J , Perrin , M , Poyneer , L , Pueyo , L , Rafikov , R R , Rajan , A , Rameau , J , Rantakyrö , F T , Ren , B , Schneider , A C , Sivaramakrishnan , A , Song , I , Soummer , R , Tallis , M , Thomas , S , Ward-Duong , K & Wolff , S 2019 , ' The Gemini Planet Imager Exoplanet Survey : giant planet and brown dwarf demographics from 10 to 100 au ' , Astronomical Journal , vol. 158 , no. 1 , 13 . https://doi.org/10.3847/1538-3881/ab16e9
Publication
Astronomical Journal
Status
Peer reviewed
ISSN
0004-6256Type
Journal article
Collections
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.