Kavli Affiliate: Avi Shporer
| First 5 Authors: David E. Shaw, David E. Shaw, , ,
| Summary:
The eight-planet Kepler-90 system exhibits the greatest multiplicity of
planets found to date. All eight planets are transiting and were discovered in
photometry from the NASA Kepler primary mission. The two outermost planets, g
($P_g$ = 211 d) and h ($P_h$ = 332 d) exhibit significant transit-timing
variations (TTVs), but were only observed 6 and 3 times respectively by Kepler.
These TTVs allow for the determination of planetary masses through dynamical
modeling of the pair’s gravitational interactions, but the paucity of transits
allows a broad range of solutions for the masses and orbital ephemerides. To
determine accurate masses and orbital parameters for planets g and h, we
combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with
the Kepler transit data. We jointly modeled the transit times of the outer two
planets and the RV time series, then used our two-planet model to predict their
future times of transit. These predictions led us to recover a transit of
Kepler-90 g with ground-based observatories in May 2024. We then combined the
2024 transit and several previously unpublished transit times of planets g and
h with the Kepler photometry and RV data to update the masses and linear
ephemerides of the planets, finding masses for g and h of $15.0 pm 1.3,
M_oplus$, and $203 pm 16, M_oplus$ respectively from a Markov Chain Monte
Carlo analysis. These results enable further insights into the architecturally
rich Kepler-90 system and pave the way for atmospheric characterization with
space-based facilities.
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