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

  • Author(s): Nielsen, EL;
  • De Rosa, RJ;
  • Macintosh, B;
  • Wang, JJ;
  • Ruffio, JB;
  • Chiang, E;
  • Marley, MS;
  • Saumon, D;
  • Savransky, D;
  • Mark Ammons, S;
  • Bailey, VP;
  • Barman, T;
  • Blain, C;
  • Bulger, J;
  • Burrows, A;
  • Chilcote, J;
  • Cotten, T;
  • Czekala, I;
  • Doyon, R;
  • Duchene, G;
  • Esposito, TM;
  • Fabrycky, D;
  • Fitzgerald, MP;
  • Follette, KB;
  • Fortney, JJ;
  • Gerard, BL;
  • Goodsell, SJ;
  • Graham, JR;
  • Greenbaum, AZ;
  • Hibon, P;
  • Hinkley, S;
  • Hirsch, LA;
  • Hom, J;
  • Hung, LW;
  • Ilene Dawson, R;
  • Ingraham, P;
  • Kalas, P;
  • Konopacky, Q;
  • Larkin, JE;
  • Lee, EJ;
  • Lin, JW;
  • Maire, J;
  • Marchis, F;
  • Marois, C;
  • Metchev, S;
  • Millar-Blanchaer, MA;
  • Morzinski, KM;
  • Oppenheimer, R;
  • Palmer, D;
  • Patience, J;
  • Perrin, M;
  • Poyneer, L;
  • Pueyo, L;
  • Rafikov, RR;
  • Rajan, A;
  • Rameau, J;
  • Rantakyrö, FT;
  • Ren, B;
  • Schneider, AC;
  • Sivaramakrishnan, A;
  • Song, I;
  • Soummer, R;
  • Tallis, M;
  • Thomas, S;
  • Ward-Duong, K;
  • Wolff, S
  • et al.
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 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.

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