Dynamical Monte Carlo Simulations of 3-D Galactic Systems in Axisymmetric and Triaxial Potentials

We describe the dynamical behavior of isolated old (> 1 G yr) objects-like Neutron Stars (NSs). These isolated NSs are evolved under smooth, time-independent, 3-D gravitational potentials, axisymmetric and with a triaxial dark halo. We analysed the geometry of the dynamics and applied the Poincare section method for comparing the influence of different birth velocity distributions. The inspection of the maximal asymptotic Lyapunov (Lambda) exponent shows that the dynamical behaviors of the selected orbits are nearly the same as the regular orbits with two degrees of freedom, both in axisymmetric and triaxial when (phi, q_z)= (0,0). Conversely, a few chaotic trajectories are found with a rotated triaxial halo when (phi, q_z)= (90, 1.5). The tube orbits preserve the direction of their circulation around either the long or short axis as appeared in the triaxial potential, even when every initial condition leads to different orientations. The Poincare section method shows that there are 2-D invariant tori and invariant curves (islands) around stable periodic orbits that bound to the surface of 3-D tori. The regularity of the several prototypical orbits offer the means to identify the phase space regions with localized motions and to determine their environment in different models, because they can occupy significant parts of phase-space depending on the potential. This is of particular importance in Galactic Dynamics.Comment: 18 pages, 7 figures, Published in Publications of the Astronomical Society of Australia (PASA

Quiescent photometric modulations of two low-inclination cataclysmic variables KZGem and TWVir

The quiescent periodic photometric modulations of two low-inclination cataclysmic variables observed in Kepler K2 Campaigns 0 and 1, KZ Gem and TW Vir, are investigated. A phase-correcting method was successfully used to detect the orbital modulations of KZ Gem and TW Vir and improve their orbital periods. The light curve morphologies of both CVs were further analyzed by defining flux ratios and creating colormaps. KZ Gem shows ellipsoidal modulations with an orbital period of 0.22242(1) day, twice the period listed in the updated RK catalogue (Edition 7.24). With this newly determined period, KZ Gem is no longer a CV in the period gap, but a long-period CV. A part of the quiescent light curve of TW Vir that had the highest stability was used to deduce its improved orbital period of 0.182682(3) day. The flat patterns shown in the colormaps of the flux ratios for KZ Gem demonstrate the stability of their orbital modulations, while TW Vir show variable orbital modulations during the K2 datasets. In TW Vir, the single versus double-peaked nature of the quiescent orbital variations before and after superoutburst may be related to the effect of the superoutburst on the accretion disk.Comment: 10 pages, 12 figures, accepted by A&

Sea state monitoring using coastal GNSS-R

We report on a coastal experiment to study GPS L1 reflections. The campaign was carried out at the Barcelona Port breaker and dedicated to the development of sea-state retrieval algorithms. An experimental system built for this purpose collected and processed GPS data to automatically generate a times series of the interferometric complex field (ICF). The ICF was analyzed off line and compared to a simple developed model that relates ICF coherence time to the ratio of significant wave height (SWH) and mean wave period (MWP). The analysis using this model showed good consistency between the ICF coherence time and nearby oceanographic buoy data. Based on this result, preliminary conclusions are drawn on the potential of coastal GNSS-R for sea state monitoring using semi-empirical modeling to relate GNSS-R ICF coherence time to SWH.Comment: All Starlab authors have contributed significantly; the Starlab author list has been ordered randomly. Submitted to GR

The Nucleosynthesis and Reaction Rates of Fluorine 19 (19F^{19}F) in the Sun

We investigate the abundance of $^{19}F$ in the Sun through the nucleosynthesis scenario. In addition, we calculate the rate equations and reaction rates of the nucleosynthesis of $^{19}F$ at different temperature scale. Other important functions of this nucleosynthesis (nuclear partition function and statistical equilibrium conditions) are also obtained. The resulting stability of $^{19}F$ occurs at nucleus with A = 19 and Mass Excess= -1.4874 MeV. As a result, this will tend to a series of neutron captures and beta-decay until $^{19}F$ is produced. The reaction rate of $^{15}N$ ($\alpha$, $\gamma$) $^{19}F$ was dominated by the contribution of three low-energy resonances, which enhanced the final $^{19}F$ abundance in the envelope.Comment: arXiv admin note: substantial text overlap with arXiv:astro-ph/0407551 by other author