California Legacy Survey. II. Occurrence of Giant Planets beyond the Ice Line

July 2021 • 2021ApJS..255...14F

Authors • Fulton, Benjamin J. • Rosenthal, Lee J. • Hirsch, Lea A. • Isaacson, Howard • Howard, Andrew W. • Dedrick, Cayla M. • Sherstyuk, Ilya A. • Blunt, Sarah C. • Petigura, Erik A. • Knutson, Heather A. • Behmard, Aida • Chontos, Ashley • Crepp, Justin R. • Crossfield, Ian J. M. • Dalba, Paul A. • Fischer, Debra A. • Henry, Gregory W. • Kane, Stephen R. • Kosiarek, Molly • Marcy, Geoffrey W. • Rubenzahl, Ryan A. • Weiss, Lauren M. • Wright, Jason T.

Abstract • We used high-precision radial velocity measurements of FGKM stars to determine the occurrence of giant planets as a function of orbital separation spanning 0.03-30 au. Giant planets are more prevalent at orbital distances of 1-10 au compared to orbits interior or exterior of this range. The increase in planet occurrence at ~1 au by a factor of ~4 is highly statistically significant. A fall-off in giant planet occurrence at larger orbital distances is favored over models with flat or increasing occurrence. We measure ${14.1}_{-1.8}^{+2.0}$ giant planets per 100 stars with semimajor axes of 2-8 au and ${8.9}_{-2.4}^{+3.0}$ giant planets per 100 stars in the range 8-32 au, a decrease in occurrence with increasing orbital separation that is significant at the ~2σ level. We find that the occurrence rate of sub-Jovian planets (0.1-1 Jupiter masses) is also enhanced for 1-10 au orbits. This suggests that lower-mass planets may share the formation or migration mechanisms that drive the increased prevalence near the water-ice line for their Jovian counterparts. Our measurements of cold gas giant occurrence are consistent with the latest results from direct imaging surveys and gravitational lensing surveys despite different stellar samples. We corroborate previous findings that giant planet occurrence increases with stellar mass and metallicity.

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Benjamin Fulton

Assistant Scientist