The Kepler Giant Planet Search. I. A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory

Abstract

Despite the importance of Jupiter and Saturn to Earth’s formation and habitability, there has not yet been a comprehensive observational study of how giant exoplanets correlate with the architectural properties of close-in, sub-Neptune-sized exoplanets. This is largely because transit surveys are particularly insensitive to planets at orbital separations ≳1 au, and so their census of Jupiter-like planets is incomplete, inhibiting our study of the relationship between Jupiter-like planets and the small planets that do transit. To investigate the relationship between close-in, small and distant, giant planets, we conducted the Kepler Giant Planet Survey (KGPS). Using the W. M. Keck Observatory High Resolution Echelle Spectrometer, we spent over a decade collecting 2844 radial velocities (RVs; 2167 of which are presented here for the first time) of 63 Sunlike stars that host 157 transiting planets. We had no prior knowledge of which systems would contain giant planets beyond 1 au, making this survey unbiased with respect to previously detected Jovians. We announce RV-detected companions to 20 stars from our sample. These include 13 Jovians ( 0.3 M J < M sin i < 13 M J , 1 au < a < 10 au), eight nontransiting sub-Saturns, and three stellar-mass companions. We also present updated masses and densities of 84 transiting planets. The KGPS project leverages one of the longest-running and most data-rich collections of RVs of the NASA Kepler systems yet, and it will provide a basis for addressing whether giant planets help or hinder the growth of sub-Neptune-sized and terrestrial planets. Future KGPS papers will examine the relationship between small, transiting planets and their long-period companions.

The Metallicity Dimension of the Super Earth-cold Jupiter Correlation

“…The feature that cold Jupiters with inner small planet companions are preferentially (or exclusively) found around metal-rich stars is already seen in the original samples used by and Bryan et al (2019) and also seen in the recent samples of Rosenthal et al (2021), Van Zandt et al (2023), and Weiss et al (2024. In particular, the pure-RV sample used in and tabulated in their table 2 shows that cold Jupiters were not detected in super-Earth systems with [Fe/ H]  0.1.…”

“…In particular, the pure-RV sample used in and tabulated in their table 2 shows that cold Jupiters were not detected in super-Earth systems with [Fe/ H]  0.1. As for the transiting systems, all those with cold Jupiter detections in resolved orbits have stellar [Fe/H] > 0 Bryan et al 2019;Van Zandt et al 2023;Weiss et al 2024). See Figure 8 of Zhu & Dong (2021) for a similar illustration to Figure 1.…”

A Tale of Two Peas in a Pod: The Kepler-323 and Kepler-104 Systems

“…We conducted an analysis of 79 newly gathered RVs, combined with 48 RVs from Bonomo et al (2023), of Kepler-323 and 44 RVs from Weiss et al (2024) of Kepler-104 in order to quantify the masses and densities of their planets. Using these newly calculated masses, we computed the mass diversity and period spacing of these systems and compared those results to other multiplanet transiting systems.…”

“…For an angular separation of 1 8, a distance of 400 pc (Gaia Collaboration 2020) corresponds to a semimajor axis of 720 au and an orbital period of 20,000 yr, and so we do not expect this companion to affect our analysis. We leverage 44 published RVs of Kepler-104 from Weiss et al (2024) to provide a detailed analysis of the mass diversity of the system.…”

“…Based on a decade of RV measurements of Kepler-323, we have no evidence of the presence of a Jupiter out to 10 au and we find a 3σ upper limit of 1 M J . The presence of a Jupiter in Kepler-104 was ruled out in Weiss et al (2024).…”