anghui Ji

PLANETARY POPULATION SYNTHESIS COUPLED WITH ATMOSPHERIC ESCAPE: A STATISTICAL VIEW OF EVAPORATION

We apply hydrodynamic evaporation models to different synthetic planet populations that were obtained from a planet formation code based on the core-accretion paradigm. We investigated the evolution of the planet populations using several evaporation models, which are distinguished by the driving force of the escape flow (X-ray or EUV), the heating efficiency in energy-limited evaporation regimes, or both. Although the mass distribution of the planet populations is barely affected by evaporation, the radius distribution clearly shows a break at approximately 2R(circle plus). We find that evaporation can lead to a bimodal distribution of planetary sizes and to an evaporation valley running diagonally downward in the orbital distance-planetary radius plane, separating bare cores from low-mass planets that have kept some primordial H/He. Furthermore, this bimodal distribution is related to the initial characteristics of the planetary populations because low-mass planetary cores can only accrete small primordial H/He envelopes and their envelope masses are proportional to their core masses. We also find that the population-wide effect of evaporation is not sensitive to the heating efficiency of energy-limited description. However, in two extreme cases, namely without evaporation or with a 100% heating efficiency in an evaporation model, the final size distributions show significant differences; these two scenarios can be ruled out from the size distribution of Kepler candidates.

Modeling Dust Emission of HL Tau Disk Based on Planet-Disk Interactions

We use extensive global two-dimensional hydrodynamic disk gas+dust simulations with embedded planets, coupled with three dimensional radiative transfer calculations, to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We include the self-gravity of disk gas and dust components and make reasonable choices of disk parameters, assuming an already settled dust distribution and no planet migration. We can obtain quite adequate fits to the observed dust emission using three planets with masses 0.35, 0.17, and 0.26

The Librating Companions in HD 37124, HD 12661, HD 82943, 47 Ursa Majoris, and GJ 876: Alignment or Antialignment?

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Could the 47 Ursae Majoris Planetary System be a Second Solar System? Predicting the Earth-like Planets

at 13.1, 33.0, and 68.6 AU, respectively. Implications for the planet formation as well as the limitations of this scenario are discussed.

Could the 55 Cancri Planetary System Really Be in the 3:1 Mean Motion Resonance?

We investigated the apsidal motion for the multiplanet systems. In the simulations, we found that the two planets of HD 37124, HD 12661, 47 UMa, and HD 82943 separately undergo apsidal alignment or antialignment. However, the companions of GJ 876 and v And are in apsidal lock only about 0degrees. Moreover, we obtained the criteria with Laplace-Lagrange secular theory to discern whether a pair of planets for a certain system are in libration or circulation.

Predicting the Configuration of a Planetary System: KOI-152 Observed by Kepler

We numerically investigated the dynamical architecture of 47 UMa with the planetary configuration of the best-fit orbital solutions by Fischer and coworkers. We systematically studied the existence of Earth-like planets in the region 0.05 AU <= a <= 2.0 AU for 47 UMa with numerical simulations and also explored the packed planetary geometry and Trojan planets in the system. In the simulations, we found that hot Earths at 0.05 AU <= a < 0.4 AU can dynamically survive for at least 1 Myr. The Earth-like planets can eventually remain in the system for 10 Myr in areas involved in mean motion resonances (MMRs; e. g., 3:2 MMR) with the inner companion. Moreover, we showed that the 2:1 and 3:1 resonances are on the fringe of stability, while the 5:2 MMR is unstable. In addition, the 2:1 MMR marks out a remarkable boundary between chaotic and regular motions: inside, most of the orbits can survive, but outside, they are mostly lost in the orbital evolution. In a dynamical sense, the most likely candidates for habitable environments are Earth-like planets with orbits in the ranges 0.8 AU <= a < 1.0 AU and 1.0 AU < a < 1.30 AU (except the 5:2 MMR and several unstable cases) with relatively low eccentricities. The Trojan planets with low eccentricities and inclinations can secularly last at the triangular equilibrium points of the two massive planets. Hence, the 47 UMa planetary system may be a close analog to our solar system, bearing a similar dynamical structure.

The Secular Evolution and Dynamical Architecture of the Neptunian Triplet Planetary System HD 69830

We integrate the orbital solutions of the planets orbiting 55 Cancri. In the simulations, we find that not only do the three resonant arguments θ1 = λ1 - 3λ2 + 21, θ2 = λ1 - 3λ2 + 22, and θ3 = λ1 - 3λ2 + (1 + 2) librate, respectively, but the relative apsidal longitude Δω also librates about 250° for millions of years. The results imply the existence of the 3 : 1 resonance and the apsidal resonance for the studied system. We emphasize that the mean motion resonance and apsidal locking can act as two important mechanisms for stabilizing the system. In addition, we further investigate the secular dynamics of this system by comparing the numerical results with those given by Laplace-Lagrange secular theory.

The Apsidal Antialignment of the HD 82943 System

The recent Kepler discovery of KOI-152 reveals a system of three hot super-Earth candidates that are in or near a 4:2:1 mean motion resonance. It is unlikely that they formed in situ; the planets probably underwent orbital migration during the formation and evolution process. The small semimajor axes of the three planets suggest that migration stopped at the inner edge of the primordial gas disk. In this paper, we focus on the influence of migration halting mechanisms, including migration dead zones, and inner truncation by the stellar magnetic field. We show that the stellar accretion rate, stellar magnetic field, and the speed of migration in the protoplanetary disk are the main factors affecting the final configuration of KOI-152. Our simulations suggest that three planets may be around a star with low star accretion rate or with high magnetic field. On the other hand, slow type I migration, which decreases to one-tenth of the linear analysis results, favors forming the configuration of KOI-152. Under such a formation scenario, the planets in the system are not massive enough to open gaps in the gas disk. The upper limits of the planetary masses are estimated to be about 15, 19, and 24M(circle plus), respectively. Our results are also indicative of the near Laplacian configurations that are quite common in planetary systems.

DISK-PLANET INTERACTION SIMULATIONS. I. BAROCLINIC GENERATION OF VORTENSITY AND NONAXISYMMETRIC ROSSBY WAVE INSTABILITY

We perform numerical simulations to study the secular orbital evolution and dynamical structure in the HD 69830 planetary system, using the best-fit orbital solutions by Lovis and coworkers. In the simulations, we show that a triplet Neptunian system is stable for at least 2 Gyr and that the stability would not be greatly influenced even if we varied the planetary masses. In addition, we employ Laplace-Lagrange secular theory to investigate the long-term behavior of the system, and the outcomes demonstrate that this theory can well describe and predict the secular orbital evolution for three Neptune-mass planets, where the secular periods and amplitudes of the eccentricities are in good agreement with those from direct numerical integrations. We first reveal that the secular periods of the eccentricity, e(1) and e(2), are identical. Moreover, we extensively explore the planetary configuration of three Neptune-mass companions with one massive terrestrial planet in 0.07 AU <= a <= 1.20 AU, to examine the potential asteroid architecture. We underline that there are stable zones lasting for at least 10(5) yr for low-mass terrestrial planets located between 0.3 and 0.5 AU and between 0.8 and 1.2 AU. We also find that the secular resonances can excite the eccentricities of the terrestrial bodies and that the accumulation or depletion of the asteroid belt is also shaped by orbital resonances of the outer planets; for example, the asteroidal gaps at the 2 : 1 and 3 : 2 mean motion resonances with planet c. In a dynamical sense, the proper candidate regions for the existence of potential terrestrial planets or habitable zones are 0.35 AU < a < 0.50 AU and 0.80 AU < a < 1.00 AU for relatively low eccentricities, implying the possible asteroidal structure in the system.

The stabilising mechanism of the HD 82943 planetary system

We perform numerical simulations to explore the dynamical evolution of the HD 82943 planetary system. By simulating diverse planetary configurations, we find two mechanisms of stabilizing the system: the 2:1 mean motion resonance (MMR) between the two planets can act as the first mechanism for all stable orbits. The second mechanism is a dynamical antialignment of the apsidal lines of the orbiting planets, which implies that the difference of the periastron longitudes Θ3 librates about 180° in the simulations. We also use a semi-analytical model to explain the numerical results for the system under study.