75,782 research outputs found
On the use of rotational splitting asymmetries to probe the internal rotation profile of stars. Application to Cephei stars
Rotationally-split modes can provide valuable information about the internal
rotation profile of stars. This has been used for years to infer the internal
rotation behavior of the Sun. The present work discusses the potential
additional information that rotationally splitting asymmetries may provide when
studying the internal rotation profile of stars. We present here some
preliminary results of a method, currently under development, which intends: 1)
to understand the variation of the rotational splitting asymmetries in terms of
physical processes acting on the angular momentum distribution in the stellar
interior, and 2) how this information can be used to better constrain the
internal rotation profile of the stars. The accomplishment of these two
objectives should allow us to better use asteroseismology as a test-bench of
the different theories describing the angular momentum distribution and
evolution in the stellar interiors.Comment: 4 pages, 2 figures; IV International Helas conference proceedings
(refereed). To be published in Astronomical Note
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
The eigenvalues of limits of radial Toeplitz operators
Let be the Bergman space on the unit disk. A bounded operator on
is called radial if for all , where
is a bounded sequence of complex numbers. We characterize the
eigenvalues of radial operators that can be approximated by Toeplitz operators
with bounded symbols.Comment: 14 page
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
Surface-induced magnetism in C-doped SnO
The magnetism of C-doped SnO (001) surfaces is studied using
first-principles calculations. It is found that carbon does not induce
magnetism in bulk SnO when located at the oxygen site, but shows a large
magnetic moment at the SnO (001) surface. The magnetic moment is mainly
contributed by the carbon atoms due to empty minority spins of orbitals and
is localized at the surface and subsurface atoms. No magnetism is observed when
the carbon atom is located at the subsurface oxygen sites. The origin of
magnetism is discussed in the context of surface bonding.Comment: 3 pages, 3 figure
Cyclic extensions are radical
We show that finite Galois extensions with cyclic Galois group are radical.Comment: 1 page. This has been published as filler in the American
Mathematical Monthl
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