6,598 research outputs found
The role of rotation on Petersen Diagrams. II The influence of near-degeneracy
In the present work, the effect of near-degeneracy on rotational Petersen
diagrams (RPD) is analysed. Seismic models are computed considering rotation
effects on both equilibrium models and adiabatic oscillation frequencies
(including second-order near-degeneracy effects). Contamination of coupled
modes and coupling strength on the first radial modes are studied in detail.
Analysis of relative intrinsic amplitudes of near-degenerate modes reveals that
the identity of the fundamental radial mode and its coupled quadrupole pair are
almost unaltered once near-degeneracy effects are considered. However, for the
first overtone, a mixed radial/quadrupole identity is always predicted. The
effect of near-degeneracy on the oscillation frequencies becomes critical for
rotational velocities larger than 15-20 km/s, for which large wriggles in the
evolution of the period ratios are obtained (up ). Such wriggles imply
uncertainties, in terms of metallicity determinations using RPD, reaching up to
0.50 dex, which can be critical for Pop. I HADS (High Amplitude \dss). In terms
of mass determinations, uncertainties reaching up to 0.5 M_sun are predicted.
The location of such wriggles is found to be independent of metallicity and
rotational velocity, and governed mainly by the avoided-crossing phenomenon.Comment: 8 pages, 7 figures, 1 table. (accepted for publication in A&A
Effective and neutral stresses in soils using boundary element methods
The evaluation of neutral pressures in soil mechanics problems is a fundamental step to evaluate deformations in soils. In this paper, we present some results obtained by using the boundary element method for plane problems, describing the undrained situation as well as the consolidation problem
FILOU oscillation code
The present paper provides a description of the oscillation code FILOU, its
main features, type of applications it can be used for, and some representative
solutions. The code is actively involved in CoRoT/ESTA exercises (this volume)
for the preparation for the proper interpretation of space data from the CoRoT
mission. Although CoRoT/ESTA exercises have been limited to the oscillations
computations for non-rotating models, the main characteristic of FILOU is,
however, the computation of radial and non-radial oscillation frequencies in
presence of rotation. In particular, FILOU calculates (in a perturbative
approach) adiabatic oscillation frequencies corrected for the effects of
rotation (up to the second order in the rotation rate) including near
degeneracy effects. Furthermore, FILOU works with either a uniform rotation or
a radial differential rotation profile (shellular rotation), feature which
makes the code singular in the field.Comment: 6 pages, 5 figures. Astrophysics and Space Science (in press
Spatial deconvolution of spectropolarimetric data: an application to quiet Sun magnetic elements
Observations of the Sun from the Earth are always limited by the presence of
the atmosphere, which strongly disturbs the images. A solution to this problem
is to place the telescopes in space satellites, which produce observations
without any (or limited) atmospheric aberrations. However, even though the
images from space are not affected by atmospheric seeing, the optical
properties of the instruments still limit the observations. In the case of
diffraction limited observations, the PSF establishes the maximum allowed
spatial resolution, defined as the distance between two nearby structures that
can be properly distinguished. In addition, the shape of the PSF induce a
dispersion of the light from different parts of the image, leading to what is
commonly termed as stray light or dispersed light. This effect produces that
light observed in a spatial location at the focal plane is a combination of the
light emitted in the object at relatively distant spatial locations. We aim to
correct the effect produced by the telescope's PSF using a deconvolution
method, and we decided to apply the code on Hinode/SP quiet Sun observations.
We analyze the validity of the deconvolution process with noisy data and we
infer the physical properties of quiet Sun magnetic elements after the
deconvolution process.Comment: 14 pages, 9 figure
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