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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 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.
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Submitted on : Friday, June 24, 2022 - 1:19:48 PM
Last modification on : Saturday, June 25, 2022 - 9:30:03 AM

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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⟩

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