共查询到20条相似文献，搜索用时 765 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Stanisław P. Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》2000,76(4):215-227
In a recent paper Ballersteros and Ragnisco (1998) have proposed a new method of constructing integrable Hamiltonian systems.
A new class of integrable systems may be devised using the following sequence:
, where A is a Lie algebra
is a Lie–Poisson structure on R
3, C is a Casimir for
is a reduced Poisson bracket and (A, ▵) is a bialgebra. We study the relation between a Lie-Poisson stucture Λ and a reduced Poisson bracket
, which is a key element in using the Lie algebra A to constructing this sequence. New examples of Lie algebras and their
related integrable Hamiltonian systems are given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
13.
A linear correlation between the ratio of the[CII( $^{\text{2}}$ P A linear correlation between the ratio of the[CII(
P
→
P
)] line intensity to the [
CO(J:1 →0)] line emission, I
/I
and the
equivalent width (EW) is found, over the range 2–71 ? in
EW, for a sample of 21late-Type= galaxies. The latter is comprised of an optically selected sample of 12 normal Virgo Cluster
spiral galaxies with [CII] detections obtained by us with ISOLWS, plus nine late-Type= galaxies with higher star formation
rates (SFRs), for which [CII] data and, especially,
EW data are available in the literature. As a result we infer I
/I
to be a reliable tracer of the current mass-normalized global SFR for non-starburst spiral galaxies. Moreover, the ratio
of the [CII] line to the total far-infrared (FIR) continuum intensity, I
/I
, is found to decrease from ∼0.5% to ∼0.1% with decreasing SFR which we propose is due to a `[CII]-quiet' component of I
from dust heated by the general interstellar radiation field (ISRF). The more `quiescent' galaxies in the sample have values
of I
/I
different from those observed in `compact' Galactic interstellar regions. Their [CII]-emission is interpreted to be dominated
by diffuse regions of the interstellar medium (ISM). For normal `star-forming' galaxies the diffuse component of the [CII]
emission is estimated to account for at least 50% of the total.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
15.
V. P. Arkhipova N. P. Ikonnikova G. V. Komissarova V. F. Esipov 《Astronomy Letters》2006,32(9):594-603
We present the results of our photoelectric observations of HD 51585 (OY Gem), a B[e] star with an infrared excess and a candidate for protoplanetary nebulae, obtained with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in 1992–2005. The star exhibited rapid irregular brightness variations with amplitudes from We present the results of our photoelectric observations of HD 51585 (OY Gem), a B[e] star with an infrared excess and a candidate
for protoplanetary nebulae, obtained with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute
in 1992–2005. The star exhibited rapid irregular brightness variations with amplitudes from
in the V band to
in U band within the observing season as well as slow systematic variations with amplitudes from
in the V band to
in the U band and with a quasi-period of ∼2800 days. The B-V color index varied within
and did not follow the slow systematic brightness variations, while U-B correlated with the U brightness and varied between
at maximum light and
at minimum light. Our low-resolution spectroscopy performed in 1994–2005 has revealed significant variability of the Balmer
and Paschen hydrogen emission lines as well as the He I and O I lines. Equivalent widths are given for the H I, He I, O I,
and Fe II lines; a correlation has been found between the star’s photometric variability and the hydrogen line intensities.
Our joint analysis of the photometric and spectroscopic data suggests that variations in a strong stellar wind are responsible
for the variability of the star.
Original Russian Text ? V.P. Arkhipova, N.P. Ikonnikova, G. V. Komissarova, V. F. Esipo, 2006, published in Pis’ma v Astronomicheskiĭ
Zhurnal, 2006, Vol. 32, No. 9, pp. 662–671. 相似文献
16.
A recent report that energetic particles measured in the solar wind may be influenced by solar gravity-mode (
-mode) oscillations motivated the search for
-mode signatures in the Ulysses solar wind plasma data. Ulysses solar wind plasma data from 1 March 1992 through the 12 April 1996 were examined in this study for signs of possible solar oscillations. The multi-taper method for spectral analysis was used to look for significant spectral peaks in the entire four-year data set, as well as in the smaller, more heliographically homogenous data set over the solar poles. Several frequencies satisfying certain significance requirements were found in the
-mode frequency range in both data sets that also agree with the previously published findings. However, these identifications are shown to be false detections, and hence the frequencies found cannot be identified as solar
modes. 相似文献
17.
I. Stellmacher 《Celestial Mechanics and Dynamical Astronomy》1999,75(3):185-200
The motion of Hyperion is an almost perfect application of second kind and second genius orbit, according to Poincaré’s classification.
In order to construct such an orbit, we suppose that Titan’s motion is an elliptical one and that the observed frequencies
are such that 4n
H−3n
T+3n
ω=0, where n
H, n
T are the mean motions of Hyperion and Titan, n
ω is the rate of rotation of Hyperion’s pericenter. We admit that the observed motion of Hyperion is a
periodic motion
such as
. Then,
.N
H, N
T, k∈ N
+. With that hypothesis we show that Hyperion’s orbit tends to a particular periodic solution among the periodic solutions
of the Keplerian problem, when Titan’s mass tends to zero. The condition of periodicity allows us to construct this orbit
which represents the real motion with a very good approximation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
G. A. krasinsky 《Celestial Mechanics and Dynamical Astronomy》1999,75(1):39-66
Analytical expressions for tidal torques induced by a tide‐arising planet which perturbs rotation of a nonrigid body are derived.
Corresponding expressions both for secular and periodic perturbations of the Euler's angles are given for the case of the
earth's rotation. Centennial secular rates of the nutation angle θ and of the earth's angular velocity ω, as well as the centennial
logarithmic decrement ν of the Chandler wobble are evaluated:
mas,
.
In the Universal Time (UT) a large out‐of‐phase (sine) dissipative term with the period 18.6 years and the amplitude 2.3 ms
is found. Corrections to nutation coefficients, which presumably have not been taken into account in IAU theory, are given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
J. Faulkner 《Astrophysics and Space Science》2003,285(2):339-339
The impact of Fred Hoyle's work on the structure and evolution of red giants, particularly his breakthrough contribution with
Martin Schwartzschild (1955), is described and assessed. Working with his students in the early 1960s, Hoyle presented new
physical ways of understanding some of the approximations used, and results obtained, in that seminal paper. His initial viewpoint
on the critical role of the outer surface boundary condition was replaced by a more subtle, if related one, which emphasized
the peculiar difficulty of storing much mass outside a dense stellar core. That viewpoint that – low-mass red giants are essentially
white dwarfs with a serious mass-storage problem – is still extremely fruitful. Recently, I have extended Hoyle's approach
to explain not only many of the structural properties of red giants themselves, but also to link and unify the structures
of low-mass stars from the main sequence through both the red giant and horizontal branch phases of evolution. Many aspects
of these stars that had remained mysterious for decades have now fallen into place, and some questions have been answered
that were not even posed before. With red giants as the simplest example, this recent work emphasizes that stars, in general,
may have at least two distinct but very important centres: (i) a geometrical centre, and (ii) a separate nuclear centre, residing in a shell outside a zero-luminosity dense core for example. This two-centre perspective leads to an explicit,
analytic, asymptotic theory of low-mass red giant structure. In this theory, there arises a naturally important in situ measure of central compactness: the parameter
. That parameter, like others, is derived self-consistently and explicitly, and can be used to show how close a given model's
properties are to ultimate asymptotic relationships. The results obtained also imply that the problem of understanding why
such stars become red giants is one of anticipating a remarkable yet natural structural bifurcation which occurs in them.
In the resulting theory, both the ratio
and products like
prove to be important, self-consistently derived quantities. Two striking theorems involving such quantities express between
them the very essence of red giant behaviour, proving analytically for the first time that stars with dense cores are necessarily
(i) extremely luminous, and (ii) very large. Perhaps the most astonishingly unexpected single result is that for the very
value Nature provides for the relevant nuclear energy-generating temperature exponent (CNO's η=15), ρsh and
behave in a well-defined, precisely inverse manner. This emphasizes that the internal behaviour of such stars is definitely anti-homologous rather than homologous, thus showing how very unfortunate the term `shell homology' is. Finally, I sketch a viewpoint which (i) links the structural
and evolutionary behaviour of stars from the main-sequence through horizontal branch phases of evolution, and also (ii) has
implications for post-main-sequence developments in more massive stars.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献