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nu Octantis
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Title: Testing a hypothesis of the nu Octantis planetary system 
Authors: Mariusz Slonina, Krzysztof Gozdziewski, Cezary Migaszewski, Anna Rozenkiewicz

We investigate the orbital stability of a putative Jovian planet reported by Ramm et. al in a compact binary nu Octantis. Our numerical study makes use of a new computational Message Passing Interface (MPI) framework Mechanic which we developed to run massive numerical experiments on CPU clusters. The code is illustrated on a model Hamiltonian introduced by Froeschlé et al. We confirm that the nu Octantis planet could reside in a retrograde orbit, according with a hypothesis of Eberle & Cúntz. It may be present in a zone of stable motions which has a structure of the Arnold web formed due to overlapping of low-order mean motion resonances and their sub-resonances. We also re-analysed the available radial velocity data in terms of self-consistent Newtonian N-body model. We found stable best-fit solutions that obey the observational constraints. They correspond to retrograde, strictly anti-aligned orbits of the binary and the planet. However, these solutions are confined in very small stable regions of the phase space. The presence of a real planet in the system is still questionable, because its formation would be hindered by strong dynamical perturbations.

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Title: The Stability of the Suggested Planet in the nu Octantis System: A Numerical and Statistical Study
Authors: Billy Quarles, Manfred  Cùntz, Zdzislaw E. Musielak

We provide a detailed theoretical study aimed at the observational finding about the nu Octantis binary system that indicates the possible existence of a Jupiter-type planet in this system. If a prograde planetary orbit is assumed, it has earlier been argued that the planet, if existing, should be located outside the zone of orbital stability. However, a previous study by Eberle &  Cùntz (2010) [ApJ 721, L168] concludes that the planet is most likely stable if assumed to be in a retrograde orbit with respect to the secondary system component. In the present work, we significantly augment this study by taking into account the observationally deduced uncertainty ranges of the orbital parameters for the stellar components and the suggested planet. Furthermore, our study employs additional mathematical methods, which include monitoring the Jacobi constant, the zero velocity function, and the maximum Lyapunov exponent. We again find that the suggested planet is indeed possible if assumed to be in a retrograde orbit, but it is virtually impossible if assumed in a prograde orbit. Its existence is found to be consistent with the deduced system parameters of the binary components and of the suggested planet, including the associated uncertainty bars given by observations.

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