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1.
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
2.
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
3.
4.
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
5.
6.
In this paper two sets of improved approximate expressions of emissivity
, absorptivity
, effective temperature Teff, and frequency of peak brightness _p of gyrosynchrotron radiation are presented respectively for the ranges from 5 to 10 and 10 to 100 of harmonic numbers s(= /_B). The expressions are designed for the range from 20° to 80° of viewing angle , and the range 2 to 7 of electron energy spectral index . They are expressed by a power-law function in which the indexes are fitted by polynomial expressions of . Their statistical errors are, respectively, 24% and 32% for
and
for
and 28% for
. Their accuracies are much better than those of linear fitting of the power-law index. 相似文献
7.
8.
9.
R. Louise 《Astrophysics and Space Science》1982,86(2):505-508
The model is based on the assumption that logarithmic spiral arms of most spiral galaxies are due to the totating density wave
obeying the steady wave equation
. It is shown that this equation accounts also for the so-called Titius-Bode's law in the solar system. 相似文献
10.
Range of values of the Sun's mass quadrupole moment of coefficient J2 arising both from experimental and theoretical determinations enlarge across literature on two orders of magnitude, from
around 10-7 until to 10-5. The accurate knowledge of the Moon's physical librations, for which the Lunar Laser Ranging data reach an outstanding precision
level, prove to be appropriate to reduce the interval of J2 values by giving an upper bound of J2. A solar quadrupole moment as high as 1.1 10-5 given either from the upper bounds of the error bars of the observations, or from the Roche's theory, is not compatible with
the knowledge of the lunar librations accurately modeled and observed with the LLR experiment. The suitable values of J2 have to be smaller than 3.0 10-6.
As a consequence, this upper bound of 3.0 10-6 is accepted to study the impact of the Sun's quadrupole moment of mass on the dynamics of the Earth-Moon system. Such as
effect (with J2 = 5.5±1.3 × 10-6) has been already tested in 1983 by Campbell & Moffat using analytical approximate equations, and thus for the orbits of
Mercury, Venus, the Earth and Icarus. The approximate equations are no longer sufficient compared with present observational
data and exact equations are required. As if to compute the effect on the lunar librations, we have used our BJV relativistic
model of solar system integration including the spin-orbit coupled motion of the Moon. The model is solved by numerical integration.
The BJV model stems from general relativity by using the DSX formalism for purposes of celestial mechanics when it is about
to deal with a system of n extended, weakly self-gravitating, rotating and deformable bodies in mutual interactions.
The resulting effects on the orbital elements of the Earth have been computed and plotted over 160 and 1600 years. The impact
of the quadrupole moment of the Sun on the Earth's orbital motion is mainly characterized by variations of
,
, and
. As a consequence, the Sun's quadrupole moment of mass could play a sensible role over long time periods of integration of
solar system models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
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
12.
For the theory described by the action
and taking the FRW flat space metric we find an exact non-singular de Sitter model universe exp(t
2), with
. It is also proved that the standard general relativity de Sitter cosmology
, >0 is also a model of this higher derivative theory of gravity. If the metric is conformally flatS could describe a consistent quantum theory and its classical solutions would correspond to cosmological models in this theory.This work was supported in part by CONACYT grand P228CCOX891723, and DGICSA SEP grant C90-03-0347. 相似文献
13.
N.A. Silant'ev 《Astrophysics and Space Science》1997,249(1):95-109
Different techniques of calculation and estimation of turbulentdiffusivities D
of passive fields in infinite incompressiblemedia showing isotropic, homogeneous and stationary turbulence areconsidered. The numerical comparison of the methods is made mostlyfor two representative limiting models of turbulence – withpeak-like spectrum and for vast Kolmogorov's type spectrum. The timedependence of two-point velocity correlators is assumed to beexponential. The backbone of the comparison is steady-state turbulentdiffusivities calculated in nonlinear DIA-approach with thecorrections due to contribution of four-order velocity correlators.As a result of this comparison the most satisfactory approximatemethods are proposed both for steady-state and time-dependentturbulent diffusivities. The results may be used for the most correctchoice of
-dependence in various astrophysical problems. 相似文献
14.
Contribution of Vacuum Field to Angular Deviation of Light Path and Radar Echo Delay 总被引：3，自引：0，他引：3
The discovery of ‘twin quasistellar objects’ arose interests among astronomers and astrophysicists to study gravitational
lensing problems. The deviation of light from its straight line path is caused by two sources according to the general theory
of relativity: (i) the presence of massive objects, i.e. the presence of gravitational field and (ii) the presence of a ‘vacuum
field’ which arises because there is a non-zero cosmological vacuum energy. Recently, the research on the relationship between
cosmological constant and gravitational lensing process is rather active (see reference [1, 2, 3]. According to the Kottler
space time metric, we have deduced an explicit representation of the angular deviation of light path. The deviation term is
found to be simply
, where M is the mass of the ‘astronomical lens’, rmin is the distance between the point of nearest approach and the centre of M, other symbols have their usual meaning. The presence
of this term may be meaningful to the study of cosmological constant using the concept of gravitational lensing; however more
sophisticated analysis awaits. Consider a signal radar to be sent from one planet to another. We have found that the radar
echo delay contributed by the existence of the cosmological constant Λ is expressible as
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
In this paper we obtain the Boltzmann equation for massless particles(i.e. photons or neutrinos) when a star is rotating and
slowly collapsing and derive its moments from it. Applying the typical metric for a rotating and slowly collapsing neutron
star and the diffusion approximation we have solved the moments of the Boltzmann equation to get a useful equation, i.e.
which may be used directly to study the properties of temperature for a central region of neutron star.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
The motion of spin particles in the Schwarzschild field is examined in this paper. It is shown that Mathisson-Papapetrou equations under additional conditions
, where
is the Lie derivative of the Killing vector
j
, permit only radial motion, motion in the equatorial plane and in the equilibrium points. All these types of motion are considered more in detail. 相似文献
17.
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
18.
G. A. Krasinsky 《Celestial Mechanics and Dynamical Astronomy》2008,101(4):325-336
The long-term systematic errors of the analytical theories IAU 2000 and IAU 2006 of the Earth’s precession–nutational motion
are studied making use of the VLBI data of 1984–2007. Several independent methods give indubitable evidence of the significant
quadratic error in the IAU 2000 residuals of the precessional angle while the adopted value of the secular decrease /cy of the Earth’s ellipticity e (derived from Satellite Laser Ranging data) should manifest itself in the residuals of as the negative quadratic trend . The problem with the precession of the IAU 2006 theory adopted as a new international standard and based on the precession
model P03 (Capitaine et al., Astron Astrophys 432:355–367, 2005) appears to be even more serious because the above mentioned quadratic term has already been incorporated into the P03 precession. Our analysis of the VLBI data demonstrates that the quadratic trend
of the IAU 2006 residuals does amount to the expected value (30.0 ± 3) mas/cy2. It means, first, that the theoretical precession rate of IAU 2006 should be augmented by the large secular correction and, second, that the available VLBI data have potentiality of estimating the rate . And indeed, processing these data by the numerical theory ERA of the Earth’s rotation (Krasinsky, Celest Mech Dyn Astron
96:169–217, 2006, Krasinsky and Vasilyev, Celest Mech Dyn Astron 96:219–237, 2006) yields the estimate /cy statistically in accordance with the satellite-based . On the other hand, applying IAU 2000/2006 models, the positive value /cy is found which is incompatible with the SLR estimate and, evidently, has no physical meaning. The large and steadily increasing
error of the precession motion of the IAU 2006 theory makes the task of replacing IAU 2006 by a more accurate model be most
pressing. 相似文献
19.
A theoretical model for3He enrichments in solar energetic particles is developed. First, current-driven, electrostatic instabilities that have frequencies
(
is the cyclotron frequency of3He) are investigated for a plasma consisting of H,4He,3He, and electrons with the density of3He much lower than those of H and4He. It is found that in many cases the oblique ion-acoustic waves can have positive growth rates at frequencies
and, at the same time, negative growth rates at
and at H. This can occur near the marginal state of the instability. The wave damping at these frequencies is caused by the cyclotron resonances of4He and H. The cyclotron damping at
is negligible, however, because the abundance of3He is very small. The H cyclotron waves can be unstable at
for a wide region of plasma parameters; the electron-to-ion temperature ratio must beT
e
/T
H
1.5. To destabilize the4He cyclotron waves with
, high4He density and high electron temperature are both required. Then,3He enrichments are studied on the basis of the theory of nonlinear magnetosonic waves, which can promptly accelerate ions. The current-driven electrostatic waves with
can enhance fluctuation velocities of3He. Thus, in the presence of these waves, magnetosonic waves can selectively accelerate3He particles to high energies. Finally, cyclotron resonances of heavy ions with the waves
or
are briefly discussed. 相似文献
20.
E. R. Lancaster 《Celestial Mechanics and Dynamical Astronomy》1970,2(1):60-63
Approximation formulas are found for
and
, wherex(t) satisfies
,x(0)=x
0,x(1)=x
1. The results are applied to an example of two-body motion. 相似文献