In this work, we investigate the eclipse timing of the polar binary HU Aquarii that has been observed for almost two decades. Recently, Qian et al. attributed large (O-C) deviations between the eclipse ephemeris and observations to a compact system of two massive jovian companions. We improve the Keplerian, kinematic model of the Light Travel Time (LTT) effect and re-analyse the whole currently available data set. We add almost 60 new, yet unpublished, mostly precision light curves obtained using the time high-resolution photo-polarimeter OPTIMA, as well as photometric observations performed at the MONET/N, PIRATE and TCS telescopes. We determine new mid--egress times with a mean uncertainty at the level of 1 second or better. We claim that because the observations that currently exist in the literature are non-homogeneous with respect to spectral windows (ultraviolet, X-ray, visual, polarimetric mode) and the reported mid--egress measurements errors, they may introduce systematics that affect orbital fits. Indeed, we find that the published data, when taken literally, cannot be explained by any unique solution. Many qualitatively different and best-fit 2-planet configurations, including self-consistent, Newtonian N-body solutions may be able to explain the data. However, using high resolution, precision OPTIMA light curves, we find that the (O-C) deviations are best explained by the presence of a single circumbinary companion orbiting at a distance of ~4.5 AU with a small eccentricity and having ~7 Jupiter-masses. This object could be the next circumbinary planet detected from the ground, similar to the announced companions around close binaries HW Vir, NN Ser, UZ For, DP Leo or SZ Her, and planets of this type around Kepler-16, Kepler-34 and Kepler-35.Comment: 20 pages, 18 figures, accepted to Monthly Notices of the Royal Astronomical Society (MNRAS

The Kepler-11 star hosts at least six transiting super-Earth planets detected through the precise photometric observations of the Kepler mission (Lissauer et al.). In this paper, we re-analyze the available Kepler data, using the direct N-body approach rather than an indirect TTV method in the discovery paper. The orbital modeling in the realm of the direct approach relies on the whole data set, not only on the mid-transits times. Most of the results in the original paper are confirmed and extended. We constrained the mass of the outermost planet g to less than 30 Earth masses. The mutual inclinations between orbits b and c as well as between orbits d and e are determined with a good precision, in the range of [1,5] degrees. Having several solutions to four qualitative orbital models of the Kepler-11 system, we analyze its global dynamics with the help of dynamical maps. They reveal a sophisticated structure of the phase space, with narrow regions of regular motion. The dynamics are governed by a dense net of three- and four-body mean motion resonances, forming the Arnold web. Overlapping of these resonances is a main source of instability. We found that the Kepler-11 system may be long-term stable only in particular multiple resonant configurations with small relative inclinations. The mass-radius data derived for all companions reveal a clear anti-correlation between the mean density of the planets with their distance from the star. This may reflect the formation and early evolution history of the system.Comment: 21 pages, 19 figures, 9 tables, accepted to MNRA

We investigate the orbital stability of a putative Jovian planet in a compact binary ν Octantis reported by Ramm et al. We re-analyzed published radial velocity data in terms of self-consistent Newtonian model and we found stable best-fit solutions that obey observational constraints. They correspond to retrograde orbits, in accord with an earlier hypothesis of Eberle & Cuntz, with apsidal lines anti-aligned with the apses of the binary. The best-fit solutions are confined to tiny stable regions of the phase space. These regions have a structure of the Arnold web formed by overlapping low-order mean motion resonances and their subresonances. The presence of a real planet is still questionable, because its formation would be hindered by strong dynamical perturbations. Our numerical study makes use of a new computational Message Passing Interface (MPI) framework Mechanic developed to run massive numerical experiments on CPU clusters.

We introduce the Mechanic, a new open-source code framework. It is designed to reduce the development effort of scientific applications by providing unified API (Application Programming Interface) for configuration, data storage and task management. The communication layer is based on the well-established Message Passing Interface (MPI) standard, which is widely used on variety of parallel computers and CPU-clusters. The data storage is performed within the Hierarchical Data Format (HDF5). The design of the code follows core-module approach which allows to reduce the user's codebase and makes it portable for single-and multi-CPU environments. The framework may be used in a local user's environment, without administrative access to the cluster, under the PBS or Slurm job schedulers. It may become a helper tool for a wide range of astronomical applications, particularly focused on processing large data sets, such as dynamical studies of long-term orbital evolution of planetary systems with Monte Carlo methods, dynamical maps or evolutionary algorithms. It has been already applied in numerical experiments conducted for Kepler-11 (Migaszewski et al., 2012) and νOctantis planetary systems (Goździewski et al., 2013). In this paper we describe the basics of the framework, including code listings for the implementation of a sample user's module. The code is illustrated on a model Hamiltonian introduced by (Froeschlé et al., 2000) presenting the Arnold diffusion. The Arnold Web is shown with the help of the MEGNO (Mean Exponential Growth of Nearby Orbits) fast indicator (Goździewski et al., 2008a) applied onto symplectic SABA n integrators family .

We report a linear ordering of orbits in a sample of multiple extrasolar planetary systems with super-Earth planets. We selected 20 cases, mostly discovered by the Kepler mission, hosting at least four planets within ∼ 0.5 au. The semi-major axis a n of an n-th planet in each system of this sample obeys a(n) = a 1 + (n − 1) ∆ a, where a 1 is the semi-major axis of the innermost orbit and ∆ a is a spacing between subsequent planets, which are specific for a particular system. For instance, the Kepler-33 system hosting five super-Earth planets exhibits the relative deviations between the observed and linearly predicted semi-major axes of only a few percent. At least half of systems in the sample fulfill the linear law with a similar accuracy. We explain the linear distribution of semi-major axes as a natural implication of multiple chains of mean motion resonances between subsequent planets, which emerge due to planet-disk interactions and convergent migration at early stages of their evolution.