TTVs are derived from Q0-Q17 Kepler data. x-axes: “Observed Tc” (Mid-Transit Time): EXOFAST’s best-fits from Normalized PDCSAP_FLUX Kepler light flux vs. time (BJD_tdb - 2454900) data. y-axes: “(O-C)”: difference between Observed Tc and the Calculated Tc from the graphically obtained linear ephemeris.
Kepler KOI-108 (Kepler-103; KIC-4914423) 4-(or more?)-Planet System
Discussion: KOI-108.02 (Kepler-103c), the farthest-out known transiting planet in this system: After a sinusoidal curve-fit of the (O-C) vs. Time data showed (Figure 1.) a periodicity (P_ttv) of 1022.99 ± 140.76 days (1030.21 days was observed in the Lomb-Scargle Periodogram (LSP) of the same data), a plot (Figure 2.) of the Residuals also gave a good sinusoidal curve-fit with a periodicity of 416.37 ± 9.09 days (LSP: 414.46 days). The added combination of these two sinusoidal curves is arrayed in Figure 3. and reasonably reproduces a complex overall curvature consistent with the initial data. While the sinusoidal behaviors observed could be partially due to orbital eccentricities, it is also possible that 2 additional as yet unseen (non-transiting) planets are present in the system. KOI-108.01 (Kepler-103b) showed no significant TTV at all.