Giant Outer Transiting Exoplanet Mass (GOT ‘EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Yr, Highly Eccentric Orbit*

Abstract

Radial velocity (RV) surveys have discovered giant exoplanets on au-scale orbits with a broad distribution of eccentricities. Those with the most eccentric orbits are valuable laboratories for testing theories of high-eccentricity migration. However, few such exoplanets transit their host stars, thus removing the ability to apply constraints on formation from their bulk internal compositions. We report the discovery of Kepler-1704 b, a transiting 4.15 M J giant planet on a 988.88 day orbit with an extreme eccentricity of -+ 0.921 0.015 0.010 . Our decade-long RV baseline from the Keck I telescope allows us to measure the orbit and bulk heavy-element composition of Kepler-1704 b and place limits on the existence of undiscovered companions. A failed hot Jupiter, Kepler-1704 b was likely excited to high eccentricity by scattering events that possibly began during its gas accretion phase. Its final periastron distance was too large to allow for tidal circularization, so now it orbits its host from distances spanning 0.16-3.9 au. The maximum difference in planetary equilibrium temperature resulting from this elongated orbit is over 700 K. A simulation of the thermal phase curve of Kepler-1704 b during periastron passage demonstrates that it is a remarkable target for atmospheric characterization from the James Webb Space Telescope, which could potentially also measure the planet's rotational period as the hot spot from periastron rotates in and out of view. Continued characterization of the Kepler-1704 system promises to refine theories explaining the formation of hot Jupiters and cool giant planets like those in the solar system.

Magnitude-squared coherence: A powerful tool for disentangling Doppler planet discoveries from stellar activity

“…Finally, in the GJ 3998 data, we found high coherence between I Hα , S-index, and RV at the frequencies of planet candidates b and c. Since it is now standard practice for planet hunters to analyze and publish activity indicator time series along with RVs (e.g. Dalba et al 2021;González-Álvarez et al 2021;Maldonado et al 2021), and since most stellar signals show up in some, but not all, activity indicators ( §4.3), we recommend that every planet discovery be vetted by analyzing the magnitude-squared coherence between RV and as many activity indicators as can be measured. Doing so is computationally cheap, and our NWelch software package is publicly available from a repository that contains examples of all functionality ( §A).…”

TESS Observations of Kepler Systems with Transit Timing Variations

“…Beyond these planets, though, the application of PLD to extract transits from noisy TESS data has several useful applications. Staying with Kepler, the longest-period transiting systems only exhibit a few transits (e.g., Kipping et al 2016;Dalba et al 2021), precluding robust TTV analyses. If the TESS extended mission continues, transits of these planets will occasionally occur during TESS observations.…”

TESS Observations of Kepler systems with Transit Timing Variations

“…This allows any variation in pixel sensitivity, coupled with random pointing jitter and systematic drift of the spacecraft, to produce time-correlated noise of PLD to extract transits from noisy TESS data has several useful applications. Staying with Kepler, the longestperiod transiting systems only exhibit a few transits (e.g., Kipping et al 2016;Dalba et al 2021), precluding robust TTV analyses. If the TESS extended mission continues, transits of these planets will occasionally occur during TESS observations.…”