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We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planets surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.
We present the discovery of two planets orbiting the nearby (D=11.9 pc) K7 dwarf Gl 414A. Gl 414A b is a sub-Neptune mass planet with M$_b sin{i_b} = 9.28^{+3.19}_{-2.54}$ M$_oplus$ and a semi-major axis of 0.24 $pm$ 0.01 au. Gl 414A c is a sub-Satur
We investigated the apsidal motion for the multi-planet 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. But the companions of GJ 876 and $ups
We present multi-epoch infrared photometry and spectroscopy obtained with warm Spitzer, Subaru and SOFIA to assess variability for the young ($sim$20 Myr) and dusty debris systems around HD 172555 and HD 113766A. No variations (within 0.5%) were foun
We present two confirmed wide separation L-dwarf common proper motion companions to nearby stars and one candidate identified from the Two Micron All Sky Survey. Spectral types from optical spectroscopy are L0 V, L2.5 V, and L8 V. Near-infrared low r
The presented work investigates the possible formation of terrestrial planets in the habitable zone (HZ) of the exoplanetary system HD 141399. In this system the HZ is located approximately between the planets c (a = 0.7 au) and d (a = 2.1 au). Exten