587 research outputs found
Sensitivity Kernels for Flows in Time-Distance Helioseismology: Extension to Spherical Geometry
We extend an existing Born approximation method for calculating the linear
sensitivity of helioseismic travel times to flows from Cartesian to spherical
geometry. This development is necessary for using the Born approximation for
inferring large-scale flows in the deep solar interior. In a first sanity
check, we compare two mode kernels from our spherical method and from an
existing Cartesian method. The horizontal and total integrals agree to within
0.3 %. As a second consistency test, we consider a uniformly rotating Sun and a
travel distance of 42 degrees. The analytical travel-time difference agrees
with the forward-modelled travel-time difference to within 2 %. In addition, we
evaluate the impact of different choices of filter functions on the kernels for
a meridional travel distance of 42 degrees. For all filters, the sensitivity is
found to be distributed over a large fraction of the convection zone. We show
that the kernels depend on the filter function employed in the data analysis
process. If modes of higher harmonic degree () are
permitted, a noisy pattern of a spatial scale corresponding to
appears near the surface. When mainly low-degree modes are used
(), the sensitivity is concentrated in the deepest regions and it
visually resembles a ray-path-like structure. Among the different low-degree
filters used, we find the kernel for phase-speed filtered measurements to be
best localized in depth.Comment: 17 pages, 5 figures, 2 tables, accepted for publication in ApJ. v2:
typo in arXiv author list correcte
Massive Superparticle with Tensorial Central Charges
We construct the manifestly Lorenz-invariant formulation of the N=1 D=4
massive superparticle with tensorial central charges. The model contains a real
parameter k and at possesses one -symmetry while at k=0 the
number of -symmetry is two. The equivalence of the formulations at all
is obtained. The local transformations of -symmetry are
written out. It is considered the using of index spinor for construction of the
tensorial central charges. It is obtained the equivalence at classical level
between the massive D=4 superparticle with one -symmetry and the
massive D=4 spinning particleComment: 20 pages, Late
New scenarios of joint crises fighting in socio-economic sphere of Russia and Greece
The purpose of the article is to verify this hypothesis and to determine the newest scenarios of joint overcoming of crises in socio-economic sphere of Russia and Greece. The work uses the method of statistical analysis, with the help of which the authors study the dynamics of socio-economic development of Russia and Greece in 2008-2014 and determine common tendencies and regularities. As a result of the research, the authors found out that Russia and Greece are peculiar for common socio-economic problems which cause similar crises, which leads to expedience of unification of efforts of both countries for their joint effective solution.
This research distinguishes three most perspective directions of fighting crises in socio-economic sphere and offers three possible scenarios of joint crisis fighting in socio-economic sphere of Russia and Greece: innovations-oriented, business-oriented, and institution-oriented scenario, with development of the authors’ concept of joint crises fighting in socio-economic sphere of Russia and Greece.peer-reviewe
Weinberg propagator of a free massive particle with an arbitrary spin from the BFV-BRST path integral
The transition amplitude is obtained for a free massive particle of arbitrary
spin by calculating the path integral in the index-spinor formulation within
the BFV-BRST approach. None renormalizations of the path integral measure were
applied. The calculation has given the Weinberg propagator written in the
index-free form with the use of index spinor. The choice of boundary conditions
on the index spinor determines holomorphic or antiholomorphic representation
for the canonical description of particle/antiparticle spin.Comment: 31 pages, Latex, version published in Class. Quantum Gra
A 3D study of the photosphere of HD 99563 - I. Pulsation analysis
We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD 99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d rotation cycle. We identify spectral features related to patches in the surface distribution of chemical elements and study the pulsation amplitudes and phases as the patches move across the stellar disc. The variations are consistent with a distorted non-radial dipole pulsation mode. We measure a 1.6 km s−1 rotational variation in the mean radial velocities of Hα and argue that this is the first observation of Hα abundance spots caused by He settling through suppression of convection by the magnetic field on an oblique rotator, in support of a prime theory for the excitation mechanism of roAp star pulsation. We demonstrate that HD 99563 is the second roAp star to show aspect dependence of blue-to-red running wave line profile variations in Nd iii spots
An asteroseismic study of the beta Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling
We present the results of a spectroscopic multisite campaign for the beta
Cephei star 12 (DD) Lacertae. Our study is based on more than thousand
high-resolution high S/N spectra gathered with 8 different telescopes in a time
span of 11 months. In addition we make use of numerous archival spectroscopic
measurements. We confirm 10 independent frequencies recently discovered from
photometry, as well as harmonics and combination frequencies. In particular,
the SPB-like g-mode with frequency 0.3428 1/d reported before is detected in
our spectroscopy. We identify the four main modes as (l1,m1) = (1, 1), (l2,m2)
= (0, 0), (l3,m3) = (1, 0) and (l4,m4) = (2, 1) for f1 = 5.178964 1/d, f2 =
5.334224 1/d, f3 = 5.066316 1/d and f4 = 5.490133 1/d, respectively. Our
seismic modelling shows that f2 is likely the radial first overtone and that
the core overshooting parameter alpha_ov is lower than 0.4 local pressure scale
heights.Comment: 16 pages, 11 figures, accepted in MNRA
PHOEBE 2.0 – Where no model has gone before
phoebe 2.0 is an open source framework bridging the gap between stellar observations and models. It allows to create and fit models simultaneously and consistently to a wide range of observational data such as photometry, spectroscopy, spectrapolarimetry, interferometry and astrometry. To reach the level of precision required by the newest generation of instruments such as Kepler, GAIA and the arrays of large telescopes, the code is set up to handle a wide range of phenomena such as multiplicity, rotation, pulsations and magnetic fields, and to model the involved physics to a new level
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