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1.
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
2.
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
3.
If fluctuations in the density are neglected, the large-scale, axisymmetric azimuthal momentum equation for the solar convection zone (SCZ) contains only the velocity correlations
and
where u are the turbulent convective velocities and the brackets denote a large-scale average. The angular velocity, , and meridional motions are expanded in Legendre polynomials and in these expansions only the two leading terms are retained (for example,
where is the polar angle). Per hemisphere, the meridional circulation is, in consequence, the superposition of two flows, characterized by one, and two cells in latitude respectively. Two equations can be derived from the azimuthal momentum equation. The first one expresses the conservation of angular momentum and essentially determines the stream function of the one-cell flow in terms of
: the convective motions feed angular momentum to the inner regions of the SCZ and in the steady state a meridional flow must be present to remove this angular momentum. The second equation contains also the integral
indicative of a transport of angular momentum towards the equator.With the help of a formalism developed earlier we evaluate, for solid body rotation, the velocity correlations
and
for several values of an arbitrary parameter, D, left unspecified by the theory. The most striking result of these calculations is the increase of
with D. Next we calculate the turbulent viscosity coefficients defined by
whereC
ro
0
and C
o
0
are the velocity correlations for solid body rotation. In these calculations it was assumed that 2 was a linear function of r. The arbitrary parameter D was chosen so that the meridional flow vanishes at the surface for the rotation laws specified below. The coefficients v
ro
i
and v
0o
i
that allow for the calculation of C
ro
and C
0o
for any specified rotation law (with the proviso that 2 be linear) are the turbulent viscosity coefficients. These coefficients comply well with intuitive expectations: v
ro
1
and –v
0o
3
are the largest in each group, and v
0o
3
is negative.The equations for the meridional flow were first solved with
0 and
2 two linear functions of r (
0
1
= – 2 × 10 –12 cm –1) and (
2
1
= – 6 × 10 12 cm –1). The corresponding angular velocity increases slightly inwards at the poles and decreases at the equator in broad agreement with heliosismic observations. The computed meridional motions are far too large ( 150m s–1). Reasonable values for the meridional motions can only be obtained if
o (and in consequence ), increase sharply with depth below the surface. The calculated meridional motion at the surface consists of a weak equatorward flow for gq < 29° and of a stronger poleward flow for > 29°.In the Sun, the Taylor-Proudman balance (the Coriolis force is balanced by the pressure gradient), must be altered to include the buoyancy force. The consequences of this modification are far reaching: is not required, now, to be constant along cylinders. Instead, the latitudinal dependence of the superadiabatic gradient is determined by the rotation law. For the above rotation laws, the corresponding latitudinal variations of the convective flux are of the order of 7% in the lower SCZ. 相似文献
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.
Werner Lohmann 《Astrophysics and Space Science》1977,51(1):173-176
The very young open star cluster NGC 2362 was investigated by the strip method on charts of two photographs taken with the 1-m Schmidt telescope of the European Southern Observatory. Up to the limiting magnitudeM
v
*
=5
.
m
8 the cluster contains 100 stars and can be described by the Gaussian density law (6). Further results are: Mass
= 246
, central mass density
0 = 43.1
= 246
pc-3 , radiusR2.6 pc, mean velocity of the stars
= 0.64 km s–1.
Mitteilungen Serie A. 相似文献
Mitteilungen Serie A. 相似文献
6.
The emission spectrum of comet Skoritchenko–George (C/1989 VI), unusual in its information content, was obtained on February 26.7 UT, 1990, with the use of a TV scanner installed on the 6-m BTA reflector of the Special Astronomical Observatory of the Russian Academy of Sciences (SAO RAS) in Nizhni Arkhyz. Detailed identification of the emission lines of this comet was made. The observed spectrum contains 311 emission lines, including those of the
molecules. Among others, the lines of the negative carbon C
2
-
ion and the lines corresponding to the electron transition
in the neutral CO molecule are discovered. The presence of a large number of lines of the neutral CO molecule (the Asundi bands and the triplet bands) in the visible region is one of the uncommon features of the emission spectrum of this comet. The triplet lines
: 15–3, 13–2, 11–2, 9–1, 8–1, 7–1, 7–0, 5–0, 4–0;
: 7–0, 6–0, 5–0; and a"
: 11–1 (K = 3, 4); 16–4 (K= 0, 1, 2, 4); 9-0 (K= 0, 1, 2); 8–0 (K= 0) were identified for the first time. Prior to this work, the lines of CO in the visible range were observed only in the spectrum of comet C/1979 VI (Bradfield) in 1989. 相似文献
7.
I. H. Urch 《Astrophysics and Space Science》1977,49(2):443-472
The diffusion of charged particles through a weak stochastic electro-magnetic field which is superimposed on a constant background magnetic field
is considered. The stochastic electromagnetic fields are assumed to consist of unpolarized Alfvén waves propagating at arbitrary angles to the direction
. When the Alfvén waves are propagating in directions other than
and the particle gyro-radius,r
g, is sufficiently large (but may be smaller than the correlation length of the stochastic fields) it is shown that the particle flux perpendicular to the direction
is
, wherev is the particle speed andf the particle density. The expression forK
differs from those calculated by previous authors. For small particle gyro-radii the flux S has a different functional form and is identical to that found by Urch (1977) to describe particle diffusion when the Alfvén waves only propagate in the direction
. 相似文献
8.
On the basis of a globular cluster study a crude estimate of the total mass of the galactic halo within 20 kpc from the centre is done. It gives a minimal halo mass of the order of
, yielding possibilities for a mass as large as
. The content of the interstellar matter in the halo is estimated too. It is found that the gas content is a few percents the minimal mass, the gas temperature is very high — about 1×106 K, the magnetic field weak — about 0.25 nT. A weak nonthermal radio emission might be expected from such a halo. 相似文献
9.
The differential equations governing relativistic polytropic fluid spheres have been integrated numerically for polytropic indexn = 0.0 (0.1) 4.9 and relativity parameter = 0.0 (0.1) 0.9, and the resulting boundary conditions for
and other related quantities are presented in this paper. 相似文献
10.
We explore self-similar hydrodynamic evolution of central voids embedded in an isothermal gas of spherical symmetry under
the self-gravity. More specifically, we study voids expanding at constant radial speeds in an isothermal gas and construct
all types of possible void solutions without or with shocks in surrounding envelopes. We examine properties of void boundaries
and outer envelopes. Voids without shocks are all bounded by overdense shells and either inflows or outflows in the outer
envelope may occur. These solutions, referred to as type
void solutions, are further divided into subtypes
and
according to their characteristic behaviours across the sonic critical line (SCL). Void solutions with shocks in envelopes
are referred to as type
voids and can have both dense and quasi-smooth edges. Asymptotically, outflows, breezes, inflows, accretions and static outer
envelopes may all surround such type
voids. Both cases of constant and varying temperatures across isothermal shock fronts are analyzed; they are referred to as
types
and
void shock solutions. We apply the ‘phase net matching procedure’ to construct various self-similar void solutions. We also
present analysis on void generation mechanisms and describe several astrophysical applications. By including self-gravity,
gas pressure and shocks, our isothermal self-similar void (ISSV) model is adaptable to various astrophysical systems such
as planetary nebulae, hot bubbles and superbubbles in the interstellar medium as well as supernova remnants.
相似文献
11.
An estimate of the period of the rotation of the line of apsides of the double-star system Phe is obtained by representing the density function as a product of a normal Gaussian distribution and an associated Legendre polynomial
.The asymptotic behaviour of this function coincides with the results obtained by Zeldovichet al. (1981).The period of motion of the line of apsides of Phe (about 63 years) obtained in this way comes close to the period determined by an empirical formula for
of Batten (1973). 相似文献
12.
Das Gupta represented theH-functions of transport problems for the albedo [0, 1] in the formH(z)=R(z)–S(z) (see Das Gupta, 1977) whereR(z) is a rational function ofz andS(z) is regular on [–1, 0]
c
. In this paper we have representedS(z) through a Fredholm integral equation of the second kind with a symmetric real kernelL(y, z) as
. The problem is then solved as an eigenvalue problem. The kernel is converted into a degenerate kernel through finite Taylor's expansion and the integral equation forS(z) takes the form:
(which is solved by the usual procedure) where
r
's are the discrete eigenvalues andF
r
's the corresponding eigenfunctions of the real symmetric kernelL(y, z). 相似文献
13.
Asger G. Gasanalizade 《Astrophysics and Space Science》1992,195(2):463-466
A possible semi-annual variation of the Newtonian constant of gravitationG is established. For the aphelion and perihelion points of the Earth's orbit we find, respectively,
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相似文献
14.
Yasushi Kawai 《Astrophysics and Space Science》1989,151(1):81-101
We have studied the effect of the flow in the accretion disk. The specific angular momentum of the disk is assumed to be constant and the polytropic relation is used. We have solved the structure of the disk and the flow patterns of the irrotational perfect fluid.As far as the obtained results are concerned, the flow does not affect the shape of the configuration in the bulk of the disk, although the flow velocity reaches even a half of the sound velocity at the inner edge of the disk. Therefore, in order to study accretion disk models with the moderate mass accretion rate—i.e.,
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