Very low density planets around Kepler-51 revealed with transit timing variations and an anomaly similar to a planet-planet eclipse event
- Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan)
We present an analysis of the transit timing variations (TTVs) in the multi-transiting planetary system around Kepler-51 (KOI-620). This system consists of two confirmed transiting planets, Kepler-51b (P {sub b} = 45.2 days) and Kepler-51c (P {sub c} = 85.3 days), and one transiting planet candidate KOI-620.02 (P {sub 02} = 130.2 days), which lie close to a 1: 2: 3 resonance chain. Our analysis shows that their TTVs are consistently explained by the three-planet model, and constrains their masses as M{sub b}=2.1{sub −0.8}{sup +1.5} M{sub ⊕} (Kepler-51b), M {sub c} = 4.0 ± 0.4 M {sub ⊕} (Kepler-51c), and M {sub 02} = 7.6 ± 1.1 M {sub ⊕} (KOI-620.02), thus confirming KOI-620.02 as a planet in this system. The masses inferred from the TTVs are rather small compared to the planetary radii based on the stellar density and planet-to-star radius ratios determined from the transit light curves. Combining these estimates, we find that all three planets in this system have densities among the lowest determined, ρ {sub p} ≲ 0.05 g cm{sup –3}. With this feature, the Kepler-51 system serves as another example of low-density compact multi-transiting planetary systems. We also identify a curious feature in the archived Kepler light curve during the double transit of Kepler-51b and KOI-620.02, which could be explained by their overlapping on the stellar disk (a planet-planet eclipse). If this is really the case, the sky-plane inclination of KOI-620.02's orbit relative to that of Kepler-51b is given by ΔΩ=−25.3{sub −6.8}{sup +6.2} deg, implying significant misalignment of their orbital planes. This interpretation, however, seems unlikely because such an event that is consistent with all of the observations is found to be exceedingly rare.
- OSTI ID:
- 22351609
- Journal Information:
- Astrophysical Journal, Vol. 783, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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