The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age

Travis A. Berger; Daniel Huber; Eric Gaidos; Jennifer L. van Saders; Lauren M. Weiss

doi:10.3847/1538-3881/aba18a

paper

The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age

arXiv:2005.14671 · doi:10.3847/1538-3881/aba18a

Abstract

Studies of exoplanet demographics require large samples and precise constraints on exoplanet host stars. Using the homogeneous Kepler stellar properties derived using Gaia Data Release 2 by Berger et al. (2020), we re-compute Kepler planet radii and incident fluxes and investigate their distributions with stellar mass and age. We measure the stellar mass dependence of the planet radius valley to be $d lo g R_{p}$ / $d lo g M_{⋆} = 0.2 6_{- 0.16}^{+ 0.21}$ , consistent with the slope predicted by a planet mass dependence on stellar mass ( $0.24 - 0.35$ ) and core-powered mass-loss (0.33). We also find first evidence of a stellar age dependence of the planet populations straddling the radius valley. Specifically, we determine that the fraction of super-Earths ( $1 - 1.8 R_{\oplus}$ ) to sub-Neptunes ( $1.8 - 3.5 R_{\oplus}$ ) increases from $0.61 \pm 0.09$ at young ages (< 1 Gyr) to $1.00 \pm 0.10$ at old ages (> 1 Gyr), consistent with the prediction by core-powered mass-loss that the mechanism shaping the radius valley operates over Gyr timescales. Additionally, we find a tentative decrease in the radii of relatively cool ( $F_{p} < 150 F_{\oplus}$ ) sub-Neptunes over Gyr timescales, which suggests that these planets may possess H/He envelopes instead of higher mean molecular weight atmospheres. We confirm the existence of planets within the hot sub-Neptunian "desert" ( $2.2 < R_{p} < 3.8 R_{\oplus}$ , $F_{p} > 650 F_{\oplus}$ ) and show that these planets are preferentially orbiting more evolved stars compared to other planets at similar incident fluxes. In addition, we identify candidates for cool ( $F_{p} < 20 F_{\oplus}$ ) inflated Jupiters, present a revised list of habitable zone candidates, and find that the ages of single- and multiple-transiting planet systems are statistically indistinguishable.

22 pages, 13 figures, 1 table. Accepted by AJ. The electronic version of Table 1 is available as an ancillary file (sidebar on the right). For a brief video explaining this paper, see https://youtu.be/d42ffDq1D94

The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age

Abstract

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