15,855 research outputs found
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
Neutron-H potentials and the H-properties
The continuum resonance spectrum of H (H++) is investigated by
use of the complex scaled hyperspherical adiabatic expansion method. The
crucial H-neutron potential is obtained by switching off the Coulomb part
from successful fits to He-proton experimental data. These two-body
potentials must be expressed exclusively by operators conserving the
nucleon-core mean field angular momentum quantum numbers. The energies
and widths of the ground-state resonance and the lowest two
excited and -resonances are found to be MeV,
MeV and MeV, respectively. These results agree with
most of the experimental data. The energy distributions of the fragments after
decay of the resonances are predicted.Comment: 26 pages, 8 tables, 7 figures. Accepted for publication in Nucl.
Phys.
The role of rotation on Petersen Diagrams. The 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 decay in connection with resonances and
density and temperature dependence rates of recombination into light nuclei
from -particles and neutrons.Comment: 9 pages, 8 figures. Proceedings of the 21st European Few Body
Conference held in Salamanca (Spain) in August-September 201
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
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