共查询到20条相似文献,搜索用时 15 毫秒
1.
N. T. Kochiashvili 《Astrophysics》1999,42(4):399-403
Photoelectric UBVR light curves of the gas-darkened variable EM Cep are given. A flare was detected on November 15–16, 1991:
while a brightness increase was observed in the R band, a decrease in the star’s U luminosity was observed.
Translated from Astrofizika, Vol. 42, No. 4, pp. 531–535, October–December, 1999. 相似文献
2.
This paper presents the results of the optical R band and 1.5–12 keV band X-ray monitoring of the high-energy peaked BL Lacertae source 1ES 1959+650 performed during 2002–2007
with the 70 cm Meniscus Telescope of Abastumani Astrophysical Observatory (Georgia) and the All-Sky Monitor on board the Rossi
X-ray Time Explorer, respectively. The observed long- and short-term outbursts are fitted with the lightcurves obtained by
means of the modeling of synchrotron flares that are assumed to be the result of a propagation of the relativistic shock waves
through the jet of 1ES 1959+650, pointed to the observer. Different values of the input parameters (shock velocity, particles’
spectral index, sizes of emission region, minimum and maximum Lorentz factors of the particles etc.) are used in order to
fit the simulated lightcurves whose constructed by means of observational data. This investigation shows that both shock velocity
and physical conditions in the jet of 1ES 1959+650 should be variable from flare to flare. The shocks are found to be mildly
relativistic with the apparent speeds β=0.46–0.85, expressed in the units of c. Spectral index of the particle energy distribution varied from 2.10 to 2.17 for the long-term flares while it is higher
in the case of short-term outbursts: s=2.32–2.45 that is suggested to be a result of the deceleration of shock front during its passage through the shell situated
downstream the Mach disc. The average strength of a turbulent magnetic field ranged from 0.025 gauss to 0.04 gauss for different
long-term flares while the values of 0.07–0.14 gauss were adopted for the different short-term outbursts. The lengths of variable
jet area found to be of 0.13–0.47 pc with the transverse extents of (0.5–1.0)×1017 cm in the case of long-term flares. The same characteristics for short-term outbursts were (2.74–5.5)×1016 cm and (0.2–04)×1017 cm, respectively. We conclude that both shock velocity and properties of pre-shocked plasma were not the same in 1ES 1959+650
for the different flaring epochs. 相似文献
3.
Using lists of bright galaxies with and without a bar, as well as the Lyon-Meudon Extragalactic Data Set (LEDA), the surroundings
of SB and SA galaxies have been investigated and some differences between them have been found.
Translated from Astrofizika, Vol. 42, No. 4, pp. 579–588, October–December, 1999. 相似文献
4.
A.A. V’uga 《Astrophysics》1999,42(4):460-466
A random quantity ξ, the number of pairwise mergings in a finite set of particles, is constructed in a sequential scheme of
complex trials. Let T0, T1,T2,…, Tm,…be a sequence of times. We then have a discrete approximation of the process of mergings
by a uniform Markov chain.
Translated from Astrofizika, Vol. 42, No. 4, pp. 609–616, October–December, 1999. 相似文献
5.
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
6.
Yves A. Gallant 《Astrophysics and Space Science》2007,309(1-4):197-202
The H.E.S.S. array of imaging Cherenkov telescopes has discovered a number of previously unknown γ-ray sources in the very high energy (VHE) domain above 100 GeV. The good angular resolution of H.E.S.S. (∼0.1° per event),
as well as its sensitivity (a few percent of the Crab Nebula flux) and wide 5° field of view, allow a much better constrained
search for counterparts in comparison to previous instruments. In several cases, the association of the VHE sources revealed
by H.E.S.S. with pulsar wind nebulae (PWNe) is supported by a combination of positional and morphological evidence, multi-wavelength
observations, and plausible PWN model parameters. These include the plerions in the composite supernova remnants G 0.9+0.1
and MSH 15–52, the recently discovered Vela X nebula, two new sources in the Kookaburra complex, and the association of HESS J1825–137
with PSR B1823–13. The properties of these better-established associations are reviewed. A number of other sources discovered
by H.E.S.S. are located near high spin-down power pulsars, but the evidence for association is less complete. These possible
associations are also discussed, in the context of the available multi-wavelength data and plausible PWN scenarios.
For the H.E.S.S. Collaboration 相似文献
7.
E. A. Vitrichenko 《Astrophysics》2005,48(4):475-482
The depth of the minimum of the BM Ori eclipsing system is studied in the infrared. For this purpose, observations have been
made in the JHKLM bands outside the eclipse and in the JHKL bands near the central phase of the eclipse. The depth of the
minimum is found to have a complicated wavelength dependence. In the short wavelength region of the spectrum this depth decreases
from the U band to the R band (λ=0.36–0.71 mm), which is explained in terms of eclipsing of the principal star by a dust cloud
surrounding the companion and by the disk of the companion. In the IR the depth of the minimum increases sharply from the
I to the L band (λ=0.97–3.5 mm). This effect can be explained by partial obscuring of the hot region of the dust cloud by
the disk of the companion.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 565–573 (November 2005). 相似文献
8.
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
9.
A catalog of barred spiral galaxies of types SB and SAB with BT ≤ 13.5 and δ > -10° has been compiled. Some parameters of these galaxies are given.
Translated from Astrofizika, Vol. 4L No. 1, pp. 5–21 January-March. 1998. 相似文献
10.
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
11.
Xin-Fa Deng 《Astronomy Letters》2019,45(11):740-749
In this work, I construct a LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 from the Sloan Digital Sky Survey Data Release 15 (SDSS DR15), which contains 184172 CMASS LRGs and 27158 eBOSS LRGs and examine the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors in this galaxy sample. I divide this LRG sample into subsamples with a redshift binning size of Δz = 0.01, and analyze the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors for these subsamples in each redshift bin. Overall, the u–r, u–g, g–r, and r–i colors of galaxies in LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 are very weakly correlated with the local environment, which shows that minimal environmental dependence of galaxy parameters can continue to higher redshifts. It is noteworthy that i–z color of this CMASS + eBOSS LRG sample shows substantial correlation with the local environment in the redshift region 0.70 ≤ z ≤ 0.75. 相似文献
12.
The characteristics of galaxies with and without a bar in the infrared range are compared, using two complete samples that
we have compiled. The data obtained show that star formation occurs more actively in barred galaxies than in galaxies without
a bar, which it is natural to believe is a consequence of the presence of the bar itself.
Translated from Astrofizika, Vol. 41, No. 3, pp. 349–358, July–September, 1998. 相似文献
13.
The spectrophotometric temperatures of five Mira-type variable stars are determined using observations in the Pulkovo spectrophotometric
data base in the range from 320–1080 nm. All the resulting temperatures are below the effective temperatures of stars in the
corresponding subclasses. Near the brightness maximum, the temperatures are found to be lower with increasing separation in
time from the maximum.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 415–426 (August 2007). 相似文献
14.
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
15.
L. P. Osipkov 《Astrophysics》1999,42(4):451-459
The scalar virial theorem enables one to find the upper limit for the angular momentum of an arbitrary, steadystate, self-gravitating
system. Applying the tensor virial theorem for axisymmetric systems makes it possible to reduce this limit by a factor of
1.5.
Translated from Astrofizika, Vol. 42, No. 4, pp. 597–608, October–December, 1999. 相似文献
16.
In the present work we study (i) the charged black hole in Einstein–Gauss–Bonnet (EGB) theory, known as the Einstein–Maxwell–Gauss–Bonnet
(EMGB) black hole and (ii) the black hole in EGB gravity with a Yang–Mills field. The thermodynamic geometry of these two
black hole solutions has been investigated, using the modified entropy in Gauss–Bonnet theory. 相似文献
17.
L. N. Katkar 《Astrophysics and Space Science》2010,326(1):19-26
By adopting the Newman–Penrose–Jogia–Griffith formalism, the field equations in Einstein–Cartan theory for matter with spin
creating torsion in space–time are solved in a spherically symmetric space–time by assuming only one non-vanishing component
of spin. The exact solution might be the prototype for more realistic models. 相似文献
18.
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
19.
R. P. Kane 《Solar physics》2007,246(2):487-493
Three series (1876 – 1986, 1886 – 1996, and 1896 – 2006) of 111 annual values of sunspot number R
z in each were subjected to spectral analysis to detect periodicities by the maximum entropy method (MEM), and the periodicities
so obtained were used in a multiple regression analysis (MRA) to estimate the amplitudes and phases. All series showed roughly
similar spectra with many periodicities (24 or more), but most of these were insignificant. The significant periodicities
(far exceeding 2σ) were near 5, 8 – 12, 18, and 37 years. Using the amplitudes and phases of these, we obtained reconstructed series, which
showed good correlations (+ 0.7 and more) with the original series. When extrapolated further in time, the reconstructed series
indicated R
z(max) in the ranges 80 – 101 (mean 92) for cycle 24 during years 2011 – 2014, 112 – 127 (mean 119) for cycle 25 during years
2022 – 2023, 115 – 120 (mean 118) for cycle 26 during years 2032 – 2034, and 100 – 113 (mean 109) for cycle 27 during 2043 – 2045. 相似文献
20.
V. Yu. Terebizh 《Astrophysics》1997,40(2):178-182
In the second part of this papersee [V. Yu. Terebizh, Astrofizika,40, 139 (1997)] we give results of an auxiliary nature for a first-order autoregression process. A formal statement of the problem
of estimating the spectral density of a time series is given as an inverse problem of mathematical physics.
The numbering of sections in this and the next three papers in this series is a continuation of the numbering in the first
paper, printed in the preceding issue of the journal [Astrofizika,40, 139–148 (1997)].
Translated from Astrofizika, Vol. 40, No. 2, pp. 273–280, April–June, 1 997. 相似文献