The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU

10 Apr 2019  ·  Nielsen Eric L., De Rosa Robert J., Macintosh Bruce, Wang Jason J., Ruffio Jean-Baptiste, Chiang Eugene, Marley Mark S., Saumon Didier, Savransky Dmitry, Ammons S. Mark, Bailey Vanessa P., Barman Travis, Blain Celia, Bulger Joanna, 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., Hom Justin, Hung Li-Wei, Dawson Rebekah Ilene, Ingraham Patrick, Kalas Paul, Konopacky Quinn, Larkin James E., Lee Eve J., Lin Jonathan W., Maire Jerome, Marchis Franck, Marois Christian, Metchev Stanimir, Millar-Blanchaer Maxwell A., Morzinski Katie M., Oppenheimer Rebecca, Palmer David, Patience Jennifer, Perrin Marshall, Poyneer Lisa, Pueyo Laurent, Rafikov Roman R., Rajan Abhijith, Rameau Julien, Rantakyro Fredrik T., Ren Bin, Schneider Adam C., Sivaramakrishnan Anand, Song Inseok, Soummer Remi, Tallis Melisa, Thomas Sandrine, Ward-Duong Kimberly, Wolff Schuyler ·

We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey (GPIES). 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, semi-major axis, and host stellar mass... We uncover a strong correlation between planet occurrence rate and host star mass, with stars M $>$ 1.5 $M_\odot$ more likely to host planets with masses between 2-13 M$_{\rm Jup}$ and semi-major axes of 3-100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semi-major axis (a) for planet populations around high-mass stars (M $>$ 1.5M$_\odot$) of the form $\frac{d^2 N}{dm da} \propto m^\alpha a^\beta$, finding $\alpha$ = -2.4 $\pm$ 0.8 and $\beta$ = -2.0 $\pm$ 0.5, and an integrated occurrence rate of $9^{+5}_{-4}$% between 5-13 M$_{\rm Jup}$ 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 13-80 M$_{\rm Jup}$ and 10-100 au. Brown dwarfs also appear to be distributed differently in mass and semi-major axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semi-major axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the RV method, our results are consistent with a peak in occurrence of giant planets between ~1-10 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. read more

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Earth and Planetary Astrophysics