Transit Timing in the Kepler Field with PLATO: The case for 24 cameras on the Kepler Field

Since TTV signals increase with observational baseline, PLATO's stare at the
Kepler field will yield transit timing variations with a total baseline that
includes both missions, an important opportunity unique to the PLATO mission.

We discuss the regimes in period and radius where Kepler and TESS provide
good samples for planet characterization, and highlight where PLATO could
maximize its impact; where Kepler planets are expected to have TTV signals
regardless of their prior detection, and where the TTV periodicity is
comparable to or exceeds the Kepler baseline.

We argue that PLATO's impact in characterizing low-mass planets with transit
timing will be significantly enhanced by centering Long-duration Observation
Phases on the Kepler field to ensure that 24 cameras observe Kepler targets,
enabling similar transit timing precision to Kepler. Transit timing
uncertainty scales as ~1/SNR. Hence, having just 6 (or 12) cameras on the
Kepler field instead of 24 would increase transit timing uncertainties by ~2
(or sqrt(2)).

Finally, we provide some examples of anticipated highlights from PLATO in
characterizing planets with transit timing.