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Exoplanet-Science.com

Discussion:
Outstandingly well anti-correlated...characterizes the strong, highly credible TTVs of 886.01 and 886.02 (their periods are in a mean motion resonance ratio of 2:3).  The following values define these TTVs through 17 Kepler Quarters:
P_ttv_886.01: 859.94 ± 8.26 days, Amp_ttv_886.01: 116.54 ± 3.62 min.; and
P_ttv_886.02: 856.96 ± 8.12 days, Amp_ttv_886.02: 229.61 ± 7.21 min.
[For 886.01, also thru Q17, von Essen (2014, KOINet) reported:  P_ttv: ~ 881 days, Amp_ttv: ~ 131 Min.]*
From the factor of ~ 2 in the TTV amplitudes of the above planet pair, 886.01 should have significantly greater mass.  But given the known (NEA) ratio of planetary radii, the volume ratio of the 886.01:886.02 is ~ 5, suggesting that 886.01 should have the lower density.

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.

1st Figure: KOI-886.01, P = 8.01 days [Plot avg. error bars = ± 6.20 min., smaller than symbols]
TTV_maximum: 378.88 ± 9.46 days, Amp_ttv_maximum: 47.06 ± 2.56 min.
TTV_minimum: 808.85 ± 11.69 days, Amp_ttv_minimum: -69.47 ± 2.56 min.
TTV_maximum: 1238.82 ± 14.76 days, Amp_ttv_maximum: 47.06 ± 2.56 min.
P_ttv: 859.94 ± 8.26 days.
Amp_ttv: 116.54 ± 3.62 minutes.
Lomb-Scargle periodogram, periodicity (P_ttv): 849.66 days; Power: 58.65; FAP: 0.
Linear ephemeris (this work): Tc = 8.01082513(Tc#) + 103.20402785

2nd Figure: KOI-886.02, P = 12.07 days [Plot avg. error bars = ± 6.87 min., smaller than symbols]
TTV_minimum: 384.61 ± 9.30 days, Amp_ttv_minimum: -93.69 ± 5.10 min.
TTV_maximum: 813.08 ± 11.52 days, Amp_ttv_maximum: 135.92 ± 5.10 min.
TTV_minimum: 1241.56 ± 14.55 days, Amp_ttv_minimum: -93.69 ± 5.10 min.
P_ttv: 856.96 ± 8.12 days.
Amp_ttv: 229.61 ± 7.21 minutes.
Lomb-Scargle periodogram, periodicity (P_ttv): 840.92 days; Power: 38.03; FAP: 0.
Linear ephemeris (this work): Tc = 12.07151619(Tc#) + 76.45035305

3rd Figure: KOI-886.03, P = 21.00 days [Plot avg. error bars = ± 9.31 min.]
A Lomb-Scargle periodogram showed no credible periodicities.
Linear ephemeris (this work): Tc = 20.99562763(Tc#) + 85.32350068

Literature:

• von Essen, 2014, "KOINet", http://koinet.astro.physik.uni-goettingen.de/Catalog/KOI_data/KOI_0886.01.html
• For numerous additional TTV references, including Tc#, Tc, and major TTV tabulations, see "Summary" webpage.


* The values reported in Mazeh, et al. [arXiv:1301.5499v1, 23 Jan 2013] result from data of many fewer numbers of Kepler Quarters; see also my webpage: "P_ttvV".

1 Oct 2014
Kepler KOI-886 (Kepler-54, KIC-5735762) 3-(or more?)-Planets