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1.
V. Yu. Terebizh 《Astrophysics》1998,41(2):198-201
A continuation of [V. Yu. Terebizh, Astrofizika,40, 139, 273, 413 (1997);41, 113 (1998)]. When following recommendations based on a similarity law, a least-squares estimate is justified. Ockham’s approach
is free of assumptions, but more complicated; it leads to results close to those for the least-squares method in conjunction
with a similarity law and the condition of nonnegativity of the solution. The theoretical conclusions are illustrated by calculations
for an AR-1 process.
Translated from Astrofizika, Vol. 41, No. 2, pp. 303–309, April-June. 1998. 相似文献
2.
V. Yu. Terebizh 《Astrophysics》1997,40(3):267-274
A continuation of [V. Yu. Terebizh, Astrofizika, 40, 139 (1997); 40, 273 (1997)]. An exact representation is found for the
main quantity characterizing the inverse problem: the Fisher matrix for the covariation coefficients. Application of the (Rao-Cramer)
information inequality enabled us to find the lower limit of the dispersion of an arbitrary unbiased estimate of the covariation
coefficients. The conclusions are illustrated by an example of a first-order autoregression process.
Translated from Astrofizika, Vol. 40, No. 3, pp. 413–423, August, 1997. 相似文献
3.
The results of a spectroscopic investigation of galaxies Nos. 22, 35, 133, 317, and 321 from the lists of [M. A. Kazarian,
Astrofizika,15, 5 (1979); M. A. Kazarian and é. S. Kazarian, Astrofizika,16, 17 (1980)] are given. The equivalent widths of lines, the relative intensities of emission lines, and their half-widths
are determined.
Translated from Astrofizika, Vol. 40, No. 4, pp. 619–626, October-December, 1997. 相似文献
4.
V. Yu Terebizh 《Astrophysics》1998,41(1):73-79
A continuation of V. Yu. Terebizh, Astrofizika,40, 139, 273, 413 (1997). An explicit representation is found for the Fisher matrix for spectral density, enabling one to calculate
the lower limit of the variance of an arbitrary unbiased density estimate. Basic equations describing smoothed density estimates
are given for comparison with exact results. By numerical modeling based on the example of an AR-1 process, it is shown that
the relative accuracy q of estimation of density is some universal function of the parameter w = (F -1)/N, where F is the
number of parameters underlying the estimate and N is the length of the time series. The relationship q = θ(w), a similarity
law, explains why a number of density estimates proposed earlier (Schuster’s periodogram, in particular) proved to be statistically
inconsistent. It is just these estimates that presume an extremely detailed model of spectral density. The need for the complexity
of the model to be consistent with the observational data follows from the limitation of information about the spectrum of
the random process included in a sample of readings from a series of fixed volume.
Translated from Astrofizika, Vol. 41, No. 1. pp. 113–122, January-March, 1998. 相似文献
5.
V. Yu. Terebizh 《Astrophysics》1997,40(1):94-100
The inverse problem of finding a consistent natural estimate of spectral density is studied using the example of a stationary
Gaussian process. The initial equations are given and the main results are briefly described in the first part of the paper.
Translated from Astrofizika, Vol. 40, No. 1, pp. 139–148, January–March, 1997. 相似文献
6.
M. A. Kazarian 《Astrophysics》1997,40(2):119-124
The results of a spectroscopic and morphological investigation of galaxies with a UV excess, Nos. 205,206, 208, and 209 from the list of [M. A. Kazarian, Astrofizìka,15, 5 (1979);15, 193 (1979)], are presented. The equivalent widths, relative intensities, and half-widths of lines were determined. The mass of galaxy
No. 205 was also determined.
Translated from Astrofizika, Vol. 40, No. 2, pp. 179–185, April–June, 1997. 相似文献
7.
G. S. Sahakian 《Astrophysics》1997,40(1):77-82
The problem of the equation of state of cosmic matter is discussed and the constants of integration in the Friedmann solutions
are determined.
Translated from Astrofizika, Vol. 40, No. 1, pp. 117–124, January–March, 1997. 相似文献
8.
R. Kh Hovhannessian 《Astrophysics》1997,40(4):373-378
The distribution of B stars in the vicinity of nine southern, long-period (P > 11 days) Cepheids is studied on the basis of
U, B, V data. The parameters Q, the normal color indices (B — V)0 and (U — B)0, the color excesses E(B — V), the spectral types, and the distance moduli of these stars are determined.
Translated from Astrofizika, Vol. 40. No. 4, pp. 573–580, October-December, 1997. 相似文献
9.
Michael Nauenberg 《Celestial Mechanics and Dynamical Astronomy》2007,97(1):1-15
Numerical solutions are presented for a family of three dimensional periodic orbits with three equal masses which connects
the classical circular orbit of Lagrange with the figure eight orbit discovered by C. Moore [Moore, C.: Phys. Rev. Lett. 70, 3675–3679 (1993); Chenciner, A., Montgomery, R.: Ann. Math. 152, 881–901 (2000)]. Each member of this family is an orbit with finite angular momentum that is periodic in a frame which rotates
with frequency Ω around the horizontal symmetry axis of the figure eight orbit. Numerical solutions for figure eight shaped
orbits with finite angular momentum were first reported in [Nauenberg, M.: Phys. Lett. 292, 93–99 (2001)], and mathematical proofs for the existence of such orbits were given in [Marchal, C.: Celest. Mech. Dyn. Astron.
78, 279–298 (2001)], and more recently in [Chenciner, A. et al.: Nonlinearity 18, 1407–1424 (2005)] where also some numerical solutions have been presented. Numerical evidence is given here that the family
of such orbits is a continuous function of the rotation frequency Ω which varies between Ω = 0, for the planar figure eight
orbit with intrinsic frequency ω, and Ω = ω for the circular Lagrange orbit. Similar numerical solutions are also found for
n > 3 equal masses, where n is an odd integer, and an illustration is given for n = 21. Finite angular momentum orbits were also obtained numerically for rotations along the two other symmetry axis of the
figure eight orbit [Nauenberg, M.: Phys. Lett. 292, 93–99 (2001)], and some new results are given here. A preliminary non-linear stability analysis of these orbits is given
numerically, and some examples are given of nearby stable orbits which bifurcate from these families. 相似文献
10.
D. M. Sedrakian 《Astrophysics》1997,40(3):260-266
Equations are obtained for the dynamics of the rotation of a two-component model neutron star within the framework of the
generai theory of relativity. It is shown that for steady rotation of the star’s normal component, Ωc = const, the angular velocity Ωs of the superfluid component depends on the coordinates and is Ωc + ω, where ω is the nondiagonal component of the metric tensor.
Translated from Astrofizika, Vol. 40, No. 3, pp. 403–412, August, 1997. 相似文献
11.
Stochastic data in astronomy. II. Search for harmonic components of time series with very large gaps
This is an analysis of certain aspects of using the CLEAN algorithm for Fourier analysis of short segments of time series
and of time series consisting of short segments of length ΔT separated by very long irregular gaps. It is assumed that the
time series contain a harmonic component of amplitude A with a period longer than the length of the longest of the segments
of the time series plus white noise with dispersion N2. Reliability plots are constructed for determining the ranges of the parameters (ν, ϕ) for which the CLEAN procedure can be used to determine the values of ν, the frequency, and ϕ, the phase of the harmonic
component, with a given accuracy. The results of this analysis are used to search for harmonic components in the variation
of the Hβ line profile in spectra of the triple star δ Ori A obtained in 2004 with the BTA telescope at the Special Astrophysical
Observatory of the Russian Academy of Sciences.
__________
Translated from Astrofizika, Vol. 50, No. 2, pp. 281–297 (May 2007). 相似文献
12.
Michael Efroimsky 《Celestial Mechanics and Dynamical Astronomy》2006,96(3-4):259-288
We continue the study undertaken in Efroimsky [Celest. Mech. Dyn. Astron. 91, 75–108 (2005a)] where we explored the influence of spin-axis variations of an oblate planet on satellite orbits. Near-equatorial satellites had long been believed to keep up with the oblate primary’s equator in the cause of its spin-axis variations. As demonstrated by Efroimsky and Goldreich [Astron. Astrophys. 415, 1187–1199 (2004)], this opinion had stemmed from an inexact interpretation of a correct result by Goldreich [Astron. J. 70, 5–9 (1965)]. Although Goldreich [Astron. J. 70, 5–9 (1965)] mentioned that his result (preservation of the initial inclination, up to small oscillations about the moving equatorial plane) was obtained for non-osculating inclination, his admonition had been persistently ignored for forty years. It was explained in Efroimsky and Goldreich [Astron. Astrophys. 415, 1187–1199 (2004)] that the equator precession influences the osculating inclination of a satellite orbit already in the first order over the perturbation caused by a transition from an inertial to an equatorial coordinate system. It was later shown in Efroimsky [Celest. Mech. Dyn. Astron. 91, 75–108 (2005a)] that the secular part of the inclination is affected only in the second order. This fact, anticipated by Goldreich [Astron. J. 70, 5–9 (1965)], remains valid for a constant rate of the precession. It turns out that non-uniform variations of the planetary spin state generate changes in the osculating elements, that are linear in , where is the planetary equator’s total precession rate that includes the equinoctial precession, nutation, the Chandler wobble, and the polar wander. We work out a formalism which will help us to determine if these factors cause a drift of a satellite orbit away from the evolving planetary equator.By “precession,” in its most general sense, we mean any change of the direction of the spin axis of the planet—from its long-term variations down to nutations down to the Chandler wobble and polar wander. 相似文献
13.
Alexei V. Tsygvintsev 《Celestial Mechanics and Dynamical Astronomy》2007,99(1):23-29
We consider the Newtonian planar three-body problem with positive masses m
1, m
2, m
3. We prove that it does not have an additional first integral meromorphic in the complex neighborhood of the parabolic Lagrangian
orbit besides three exceptional cases ∑m
i
m
j
/(∑m
k
)2 = 1/3, 23/33, 2/32 where the linearized equations are shown to be partially integrable. This result completes the non-integrability analysis
of the three-body problem started in papers [Tsygvintsev, A.: Journal für die reine und angewandte Mathematik N 537, 127–149
(2001a); Celest. Mech. Dyn. Astron. 86(3), 237–247 (2003)] and based on the Morales–Ramis–Ziglin approach. 相似文献
14.
A. V. Getling 《Solar physics》2006,239(1-2):93-111
Two series of solar-granulation images – the La Palma series of 5 June 1993 and the SOHO MDI series of 17 – 18 January 1997
– are analysed both qualitatively and quantitatively. New evidence is presented for the existence of long-lived, quasi-regular
structures (first reported by Getling and Brandt, Astron. Astrophys. 382, L5 (paper I), 2002), which no longer appear unusual in images averaged over 1 – 2-hour time intervals. Such structures appear
as families of light and dark concentric rings or families of light and dark parallel strips (“ridges” and “trenches” in the
brightness distributions). In some cases, rings are combined with radial “spokes” and can thus form “web” patterns. The characteristic
width of a ridge or trench is somewhat larger than the typical size of granules. Running-average movies constructed from the
series of images are used to seek such structures. An algorithm is developed to obtain, for automatically selected centres,
the radial distributions of the azimuthally averaged intensity, which highlight the concentric-ring patterns. We also present
a time-averaged granulation image processed with a software package intended for the detection of geological structures in
aerospace images. A technique of running-average-based correlations between the brightness variations at various points of
the granular field is developed and indications are found for a dynamical link between the emergence and sinking of hot and
cool parcels of the solar plasma. In particular, such a correlation analysis confirms our suggestion that granules – overheated
blobs – may repeatedly emerge on the solar surface. Based on our study, the critical remarks by Rast (Astron. Astrophys. 392, L13, 2002) on the original paper by Getling and Brandt (paper I) can be dismissed. 相似文献
15.
The results of morphological and spectral study of the galaxies Kaz 5, Kaz 92, and Kaz 390 are presented. The observations
were made on the 2.6-m telescope at the Byurakan Observatory with the VAGR microlenses spectrograph. Isophotes of the images
of the galaxies are constructed in the Hα, [NII] λλ6584 , 6548, and [SII] λλ6731, 6717 emission lines and in the continuum. The masses of Kaz 5 and Kaz 92 are determined to be 8.6 × 108 M⊙ and 6.1 × 109 M⊙ , respectively. The mass of the gaseous component in the centers of regions I and IV of Kaz 390, which encompass a 1 pixel
area, are also determined. The morphological structure of the central region of Kaz 5 in the observed spectral range, λλ6400–6800?, differs completely from the structure of the same part of the galaxy observed with the 6-m and 2.5-m telescopes. It is shown
that these differences in the structure in images of Kaz 5 are mostly explained by the comparatively low resolution of the
telescope in combination with the VAGR spectrograph. Absorbing matter also contributes to this effect. It is also shown that
a “deficit” of nitrogen has been observed in the region of Kaz 390 studied here (a circle of diameter 40″).
Translated from Astrofizika, Vol. 52, No. 1, pp. 63–74 (February 2009). 相似文献
16.
R. P. Kane 《Solar physics》2008,249(2):369-380
The sunspot number series at the peak of sunspot activity often has two or three peaks (Gnevyshev peaks; Gnevyshev, Solar Phys.
1, 107, 1967; Solar Phys.
51, 175, 1977). The sunspot group number (SGN) data were examined for 1997 – 2003 (part of cycle 23) and compared with data for coronal
mass ejection (CME) events. It was noticed that they exhibited mostly two Gnevyshev peaks in each of the four latitude belts
0° – 10°, 10° – 20°, 20 ° – 30°, and > 30°, in both N (northern) and S (southern) solar hemispheres. The SGN were confined
to within latitudes ± 50° around the Equator, mostly around ± 35°, and seemed to occur later in lower latitudes, indicating
possible latitudinal migration as in the Maunder butterfly diagrams. In CMEs, less energetic CMEs (of widths < 71°) showed
prominent Gnevyshev peaks during sunspot maximum years in almost all latitude belts, including near the poles. The CME activity
lasted longer than the SGN activity. However, the CME peaks did not match the SGN peaks and were almost simultaneous at different
latitudes, indicating no latitudinal migration. In energetic CMEs including halo CMEs, the Gnevyshev peaks were obscure and
ill-defined. The solar polar magnetic fields show polarity reversal during sunspot maximum years, first at the North Pole
and, a few months later, at the South Pole. However, the CME peaks and gaps did not match with the magnetic field reversal
times, preceding them by several months, rendering any cause – effect relationship doubtful. 相似文献
17.
Green’s function for the linear Kompaneets equation is calculated; it is expressed in terms of a Whittaker function W2,iμ(Z) or a MacDonald function Kiμ(z) with a purely imaginary index. A method is proposed for calculating these functions. Langer’s asymptotic solution for
large μ is refined in Cherry’s second approximation. With a series expansion for small values of the argument and the asymptotic
form for large values, this approximation enables one to calculate Green’s function to five significant figures. Solutions
of the Kompaneets equation will be used to estimate the accuracy of numerical methods and to calculate the evolution of the
spectrum of a photon gas during Compton scattering, as well as the average frequencies and the dispersion of photon frequencies
for different initial spectra.
Translated from Astrofizika, Vol. 40, No. 1, pp. 97–116, January–March, 1997. 相似文献
18.
A relativistic, first-order differential equation is derived for the accumulated moment of inertia of a spherically symmetric
celestial body. An approximate equation is proposed to describe the contribution of relativistic effects to the moment of
inertia of a superdense star. For configurations of an incompressible fluid, this approximation describes the results of the
numerical calculations of Chandrasekhar and Miller to within 5% in the entire range of central pressures from 0 to ∞.
Translated from Astrofizika, Vol. 40, No. 1, pp. 87–96, January–March, 1997. 相似文献
19.
We performed a detailed analysis of 27 slow coronal mass ejections (CMEs) whose heights were measured in at least 30 coronagraphic
images and were characterized by a high quality index (≥4). Our primary aim was to study the radial evolution of these CMEs
and their properties in the range 2 – 30 solar radii. The instantaneous speeds of CMEs were calculated by using successive
height – time data pairs. The obtained speed – distance profiles [v(R)] are fitted by a power law v = a(R−b)
c
. The power-law indices are found to be in the ranges a=30 – 386, b=1.95 – 3.92, and c=0.03 – 0.79. The power-law exponent c is found to be larger for slower and narrower CMEs. With the exception of two events that had approximately constant velocity,
all events were accelerating. The majority of accelerating events shows a v(R) profile very similar to the solar-wind profile deduced by Sheeley et al. (Astrophys. J.
484, 472, 1997). This indicates that the dynamics of most slow CMEs are dominated by the solar wind drag. 相似文献
20.
Michael Nowak 《Astrophysics and Space Science》2005,300(1-3):159-166
Previous work by Motch et al. [1985, Space Sci. Rev. 40, 219] suggested that in the low/hard state of GX, the soft X-ray power-law extrapolated backward in energy agrees with the
IR flux level. Corbel and Fender [2002, ApJ 573, L35–L39] later showed that the typical hard state radio power-law extrapolated forward in energy meets the backward extrapolated
X-ray power-law at an IR spectral break, which was explicitly observed twice in GX. This has been cited as further evidence
that jet synchrotron radiation might make a significant contribution to the observed X-rays in the hard state. We explore
this hypothesis with a series of simultaneous radio/X-ray hard state observations of GX. We fit these spectra with a simple,
but remarkably successful, doubly broken power-law model that indeed requires a spectral break in the IR. For most of these
observations, the break position as a function of X-ray flux agrees with the jet model predictions. We then examine the radio
flux/X-ray flux correlation in CYG through the use of 15 GHz radio data, obtained with the Ryle radio telescope, and Rossi X-ray Timing Explorer data, from the All Sky Monitor and pointed observations. We find evidence of ‘parallel tracks’ in the radio/X-ray correlation which are associated with
‘failed transitions’ to, or the beginning of a transition to, the soft state. We also find that for CYG the radio flux is
more fundamentally correlated with the hard, rather than the soft, X-ray flux. 相似文献