DETECTING PLANET PAIRS IN MEAN MOTION RESONANCES VIA THE ASTROMETRY METHOD

DETECTING PLANET PAIRS IN MEAN MOTION RESONANCES VIA THE ASTROMETRY METHOD

Authors:

Wu et al

Abstract:

Gaia is leading us into a new era with a high astrometry precision of ~10 μas. Under such precision, astrometry can play an important role in detecting and characterizing exoplanets. In particular, we can identify planet pairs in mean motion resonances (MMRs), which constrain the formation and evolution of planetary systems. In accordance with observations, we consider two-Jupiter or two-super-Earth systems in 1:2, 2:3, and 3:4 MMRs. Our simulations show that the false alarm probabilities (FAPs) of a third planet are extremely small, while the two real planets can be fitted well with a signal-to-noise ratio (S/N)$\;\gt \;3$. The probability of reconstructing a resonant system is related to the eccentricities and the resonance intensity. Generally, when the S/N $\geqslant \;10$, if the eccentricities of both planets are larger than 0.01 and the resonance is quite strong, the probability of reconstructing the planet pair in MMRs is $\geqslant \;80 \% $. Jupiter pairs in MMRs are reconstructed more easily than super-Earth pairs with similar S/N when we consider dynamical stability. FAPs are also calculated when we detect planet pairs in or near MMRs. The FAPs for 1:2 MMRs are the largest, i.e., FAP $\gt 15 \% $ when S/N $\leqslant \;10$. Extrapolating from the Kepler planet pairs near MMRs and assuming a S/N ~ 3, we discover and reconstruct a few tens of Jupiter pairs and hundreds of super-Earth pairs in 2:3 and 1:2 MMRs within 30 pc. We also compare the differences between even and uneven data cadence and find that planets are better measured with more uniform phase coverage.