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Figure 5.:
Linear ephemeris (this work) from Tc# vs Tc of Q0-Q6: Tc = 4.28780392(Tc#) + 195.04300048

Figure 6.:
Linear ephemeris (this work) from Tc# vs Tc of Q0-Q12: Tc = 4.28753403(Tc#) + 195.05057533

Figure 7.:
Linear ephemeris (this work) from Tc# vs Tc of Q0-Q13: Tc = 4.28754894(Tc#) + 195.04973781

Figure 8.:
Linear ephemeris (this work) from Tc# vs Tc of Q0-Q17: Tc = 4.28810103(Tc#) + 195.01237434

Footnote:
(O-C) vs. Time data (Figure 8, yellow circles) was derived from Tc# vs. Tc data of Roberto Sanchis-Ojeda (2013), kindly forwarded to me by Katherine Michele Deck.  [The derived linear ephemeris is: Tc = 4.28810162(Tc#) + 57.79363579; data starts at T_0 whereas NASA Exoplanet Archives data begins at T_(-32).]  The same had similarly been sourced and disclosed (2014) by Carolina von Essen on her "KOINet" website: http://koinet.astro.physik.uni-goettingen.de/Catalog/KOI_data/KOI_0984.01.html


This author gratefully acknowledges Roberto Sanchis-Ojeda, Katherine Deck, and Carolina von Essen for their support and willingness to share.

References:
• For Q1-6 TTV data of 984.01, see Planet Hunters website, http://talk.planethunters.org/discussions.
• For Q1-6 TTV data of 984.01, see: Ford et al., 2012, arXiv-1201.1892.
• For Q2-12 TTV data of 984.01, see: Mazeh et al., 2013, arXiv-1301.5499.
• For Q1-13 TTV data of 984.01, see: Xie's website: http://www.astro.utoronto.ca/~jwxie/TTV/TTV_Home.html, table TTV_2.
• "KOINet", vonEssen et al., http://koinet.astro.physik.uni-goettingen.de/Catalog/KOI_data/KOI_0984.01.html26

Apr 2014; updated 5 May 2014.
Above figures are derived from Long-Cadence data, available for all Kepler quarters Q0-Q17: 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.

Figure 1.: "TTVxy" Plot, avg. error bars = ± 3.76 min. (within the marker size used).
TTV_maximum: 326.37 ± 22.67 days, Amp_ttv_maximum: 92.94 ± 6.69 min.
TTV_minimum: 932.79 ± 31.13 days, Amp_ttv_minimum: -116.41 ± 6.69 min.
P_ttv: 1212.85 ± 29.60 days.
Amp_ttv: 209.35 ± 9.47 minutes.
Lomb-Scargle periodogram, candidate P_ttv: 1203.08 days; Power: 81.71; FAP: 0.
Linear ephemeris (this work): Tc = 4.28810103(Tc#) + 195.01237434

Figure 2.: Residuals of Figure 1., avg. error bars = ± 7.68 min. (within the marker size used).
TTV_maximum: 231.55 ± 7.68 days, Amp_ttv_maximum: 68.51 ± 3.59 min.
TTV_minimum: 529.26 ± 8.73 days, Amp_ttv_minimum: -83.05 ± 3.59 min.
TTV_maximum: 826.96 ± 10.33 days, Amp_ttv_maximum: 68.51 ± 3.59 min.
TTV_minimum: 1124.66 ± 12.28 days, Amp_ttv_minimum: -83.05 ± 3.59 min.
TTV_maximum: 1422.37 ± 14.43 days, Amp_ttv_maximum: 68.51 ± 3.59 min.
P_ttv: 595.41 ± 5.18 days.
Amp_ttv: 151.56 ± 5.08 minutes.
Lomb-Scargle periodogram, candidate P_ttv: 601.34 days; Power: 101.00; FAP: 0.

Figure 3.: Residuals of Figure 2. (Residuals-of-the-Residuals of Figure 1.), avg. error bars = ± 8.48 min. (within the marker size used).
TTV_minimum: 237.09 ± 18.94 days, Amp_ttv_minimum: -30.16 ± 2.74 min.
TTV_maximum: 649.62 ± 23.03 days, Amp_ttv_maximum: 37.29 ± 2.74 min.
TTV_minimum: 1062.15 ± 29.35 days, Amp_ttv_minimum: -30.16 ± 2.74 min.
TTV_maximum: 1474.68 ± 36.77 days, Amp_ttv_maximum: 37.29 ± 2.74 min.
P_ttv: 825.06 ± 17.86 days.
Amp_ttv: 67.45 ± 3.87 minutes.
Lomb-Scargle periodogram, candidate P_ttv: 811.61 days; Power: 64.09; FAP: 0.

Figure 4.: Additive combination of Figures 1., 2., and 3., avg. error bars = ± 12.04 min.
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Agreement between TTVs disclosed here and those reported by four groups: Ford et al.; Mazeh et al.; Xie; and Sanchis-Ojeda, for different portions of Kepler's total lifetime, are shown in Figures 5., 6., 7., and 8., respectively.  The changes seen with successive quarters are also reminiscent of what is discussed on web page "P_ttvV".
Kepler KOI-984 (KIC-1161345) 4(?)-(or more?)-Planet System

Discussion:
A transit timing variation (TTV) for 984.01 has previously been reported by Planet Hunters (Kepler Q1-6), Ford (Q1-6), Mazeh (Q2-12), and Xie (Q1-13) (references below).  Through Q13, they all appeared to be fairly typical of many TTVs uncovered by the Kepler space telescope.  But then, in the next 10 months, i.e.: Q14 through the 1st month of Q17, the TTV became exceptional as it surprisingly underwent a pronounced upward excursion taking it out of the "typical TTV" category.  [Also see C. von Essen's KOINet web pages (reference below) that now also displays the TTV for 984.01 through Kepler Q17; the data for that plot was obtained from Roberto Sanchis-Ojeda and Katherine Michele Deck.]

A Lomb-Scargle Periodogram (LSP) of the Q0-Q17 [(O-C) vs. Time] ("TTVxy") data showed a pronounced and credible periodicity of ~ 1203 days; this same data fit an overall sinusoidal array which showed a corresponding periodicity (P_ttv) of ~ 1213 days (Figure 1.)  The residuals from that TTV plot also displayed a clear periodicity: LSP: ~ 601 days; sinusoidal array: ~ 595 days (Figure 2.).  Finally, the residuals-of-the-residuals of the TTV plot also indicated another periodicity: LSP: ~ 812 days; sinusoidal array: ~ 825 days (Figure 3.).  By adding these three best-fit sinusoidal curves together, a reasonably close representation of the initial TTV behavior (Figure 4.) was generated.  Could these results be implying that there are 3 other unseen (non-transiting) planetary objects in this system each having an effect on the orbit of 984.01?  (Maybe we are positioned to see the one planet (984.01) that happens to be out of the main planetary plane.)