The scattering outcomes of Kepler circumbinary planets: planet mass ratio

Recent studies reveal that the free eccentricities of Kepler-34b and Kepler-413b are much larger than their forced eccentricities, implying that the scattering events may take place in their formation. The observed orbital configuration of Kepler-34b cannot be well reproduced in disk-driven migration models, whereas a two-planet scattering scenario can play a significant role of shaping the planetary configuration. These studies indicate that circumbinary planets discovered by Kepler may have experienced scattering process. In this work, we extensively investigate the scattering outcomes of circumbinary planets focusing on the effects of planet mass ratio. We find that the planetary mass ratio and the the initial relative locations of planets act as two important parameters which affect the eccentricity distribution of the surviving planets. As an application of our model, we discuss the observed orbital configurations of Kepler-34b and Kepler-413b. We first adopt the results from the disk-driven models as the initial conditions, then simulate the scattering process occurred in the late evolution stage of circumbinary planets. We show that the present orbital configurations of Kepler-34b and Kepler-413b can be well reproduced when considering two unequal-mass planet ejection model. Our work further suggests that some of the currently discovered circumbinary single-planet systems may be the survivals of original multiple-planet systems. The disk-driven migration and the scattering events occurring in the late stage both play an irreplaceable role in sculpting the final systems.Comment: 18 pages, 9 figures, accepted for publication in A

The silicate model and carbon rich model of CoRoT-7b, Kepler-9d and Kepler-10b

Possible bulk compositions of the super-Earth exoplanets, CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate and a non-standard carbon model. Their internal structures are deduced using the suitable equation of state of the materials. The degeneracy problems of their compositions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) The iron core of CoRoT-7b is not more than 27% of its total mass within 1 $\sigma$ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be compatible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely with a Mercury-like composition, its old age implies that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only super-Earth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.Comment: 20 pages, 8figures, accepted for publication in RAA. arXiv admin note: text overlap with arXiv:0707.289

Primordial Non-Gaussianity from LAMOST Surveys

The primordial non-Gaussianity (PNG) in matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the large scale structure distribution of galaxies and quasars, which could be used for constraining it. We study the detection limits on PNG from the surveys of the LAMOST telescope. The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and the quasar survey of different magnitude limits are considered. We find that the MAIN1 sample (i.e. the main galaxy survey with one magnitude deeper than the SDSS main galaxy survey, or r<18.8) could only provide very weak constraint on PNG. For the MAIN2 sample (r<19.8) and the LRG survey, the 2\sigma (95.5%) limit on the PNG parameter f_{NL} are |f_{NL}|<145 and |f_{NL}|<114 respectively, comparable to the current limit from cosmic microwave background (CMB) data. The quasar survey could provide much more stringent constraint, and we find that the 2\sigma limit for |f_{NL}| is between 50 and 103, depending on the magnitude limit of the survey. With Planck-like priors on cosmological parameters, the quasar survey with g<21.65 would improve the constraints to |f_{NL}|<43 (2\sigma). We also discuss the possibility of further tightening the constraint by using the relative bias method proposed by Seljak(2008).Comment: 8 pages, 2 figures, RAA accepte