TTVs are derived from Q1-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.
Numerous literature and major Tc#, Tc, and TTV tabulation references can be found on my "Summary" webpage following the table.
15 April 2015
Kepler KOI-3398 (KIC-3561464) 4-(or more?)-Planet System
Discussion: In the example of KOI-3398.02, a sinusoidal curve-fit of the (O-C) vs. Time data showed (Figure below) a periodicity (P_ttv) of 184.37 ± 2.39 days; 184.00 days was observed in the Lomb-Scargle Periodogram (LSP) of the same data. Neither of the other two known transiting exoplanets in this system (3398.01 and 3398.03) showed any significant TTVs.