Probing the Stellar Surface of HD 209458 from Multicolor Transit Observations

Multicolor photometric observations of a planetary transit in the system HD 209458 are analyzed. The observations, made in the Stromgren photometric system, allowed a recalculation of the basic physical properties of the star-planet system. This includes derivation of linear limb-darkening values of HD 209458, which is the first time that a limb-darkening sequence has observationally been determined for a star other than the Sun. As the derived physical properties depend on assumptions that are currently known with limited precision only, scaling relations between derived parameters and assumptions are given. The observed limb-darkening is in good agreement with theoretical predictions from evolutionary stellar models combined with ATLAS model atmospheres, verifying these models for the temperature (Teff ~ 6000K), surface gravity (log g ~ 4.3) and mass (~ 1.2 Msol) of HD 209458.Comment: 16 pages, 8 figures, uses elsart.cls, accepted for New Astronom

Temporal video transcoding from H.264/AVC-to-SVC for digital TV broadcasting

Mobile digital TV environments demand flexible video compression like scalable video coding (SVC) because of varying bandwidths and devices. Since existing infrastructures highly rely on H.264/AVC video compression, network providers could adapt the current H.264/AVC encoded video to SVC. This adaptation needs to be done efficiently to reduce processing power and operational cost. This paper proposes two techniques to convert an H.264/AVC bitstream in Baseline (P-pictures based) and Main Profile (B-pictures based) without scalability to a scalable bitstream with temporal scalability as part of a framework for low-complexity video adaptation for digital TV broadcasting. Our approaches are based on accelerating the interprediction, focusing on reducing the coding complexity of mode decision and motion estimation tasks of the encoder stage by using information available after the H. 264/AVC decoding stage. The results show that when our techniques are applied, the complexity is reduced by 98 % while maintaining coding efficiency

Inconsistencies in the application of harmonic analysis to pulsating stars

Using ultra-precise data from space instrumentation we found that the underlying functions of stellar light curves from some AF pul- sating stars are non-analytic, and consequently their Fourier expansion is not guaranteed. This result demonstrates that periodograms do not provide a mathematically consistent estimator of the frequency content for this kind of variable stars. More importantly, this constitutes the first counterexample against the current paradigm which considers that any physical process is described by a contin- uous (band-limited) function that is infinitely differentiable.Comment: 9 pages, 8 figure

The role of rotation on Petersen Diagrams. The Pi1/0(Omega) Pi_{1/0}(Omega) period ratios

The present work explores the theoretical effects of rotation in calculating the period ratios of double-mode radial pulsating stars with special emphasis on high-amplitude delta Scuti stars (HADS). Diagrams showing these period ratios vs. periods of the fundamental radial mode have been employed as a good tracer of non-solar metallicities and are known as Petersen diagrams (PD).In this paper we consider the effect of moderate rotation on both evolutionary models and oscillation frequencies and we show that such effects cannot be completely neglected as it has been done until now. In particular it is found that even for low-to-moderate rotational velocities (15-50 km/s), differences in period ratios of some hundredths can be found. The main consequence is therefore the confusion scenario generated when trying to fit the metallicity of a given star using this diagram without a previous knowledge of its rotational velocity.Comment: A&A in pres

Few-body decay and recombination in nuclear astrophysics

Three-body continuum problems are investigated for light nuclei of astrophysical relevance. We focus on three-body decays of resonances or recombination via resonances or the continuum background. The concepts of widths, decay mechanisms and dynamic evolution are discussed. We also discuss results for the triple $\alpha$ decay in connection with $2^+$ resonances and density and temperature dependence rates of recombination into light nuclei from $\alpha$-particles and neutrons.Comment: 9 pages, 8 figures. Proceedings of the 21st European Few Body Conference held in Salamanca (Spain) in August-September 201

Test of the Additivity Principle for Current Fluctuations in a Model of Heat Conduction

The additivity principle allows to compute the current distribution in many one-dimensional (1D) nonequilibrium systems. Using simulations, we confirm this conjecture in the 1D Kipnis-Marchioro-Presutti model of heat conduction for a wide current interval. The current distribution shows both Gaussian and non-Gaussian regimes, and obeys the Gallavotti-Cohen fluctuation theorem. We verify the existence of a well-defined temperature profile associated to a given current fluctuation. This profile is independent of the sign of the current, and this symmetry extends to higher-order profiles and spatial correlations. We also show that finite-time joint fluctuations of the current and the profile are described by the additivity functional. These results suggest the additivity hypothesis as a general and powerful tool to compute current distributions in many nonequilibrium systems.Comment: 4 pages, 4 figure