On reverberation and cross-correlation estimates of the size of the broad-line region in active galactic nuclei

It is known that the dependence of the emission-line luminosity of a typical cloud in the active galactic nuclei (AGN) broad-line regions (BLRs) upon the incident flux of ionizing continuum can be non-linear. We study how this non-linearity can be taken into account in estimating the size of the BLR by means of the 'reverberation' methods. We show that the BLR size estimates obtained by cross-correlation of emission-line and continuum light curves can be much (up to an order of magnitude) less than the values obtained by reverberation modelling. This is demonstrated by means of numerical cross-correlation and reverberation experiments with model continuum flares and emission-line transfer functions and by means of practical reverberation modelling of the observed optical spectral variability of NGC 4151. The time behaviour of NGC 4151 in the Hα and Hβ lines is modelled on the basis of the observational data by Kaspi et al. and the theoretical BLR model by Shevchenko. The values of the BLR parameters are estimated that allow to judge on the size and physical characteristics of the BLR. The small size of the BLR, as determined by the cross-correlation method from the data of Kaspi et al., is shown to be an artefact of this method. So, the hypothesis that the BLR size varies in time is not necessitated by the observational data.     

Do Long-Lived Features Really Exist in the Solar Photosphere? II. Contrast of Time-Averaged Granulation Images

The decrease in the rms contrast of time-averaged images with the averaging time is compared between four data sets: (1) a series of solar granulation images recorded at La Palma in 1993, (2) a series of artificial granulation images obtained in numerical simulations by Rieutord et al. (Nuovo Cimento 25, 523, 2002), (3) a similar series computed by Steffen and his colleagues (see Wedemeyer et al. in Astron. Astrophys. 44, 1121, 2004), (4) a random field with some parameters typical of the granulation, constructed by Rast (Astron. Astrophys. 392, L13, 2002). In addition, (5) a sequence of images was obtained from real granulation images by using a temporal and spatial shuffling procedure, and the contrast of the average of n images from this sequence as a function of n is analysed. The series (1) of real granulation images exhibits a considerably slower contrast decrease than do both the series (3) of simulated granulation images and the series (4) of random fields. Starting from some relatively short averaging times t, the behaviour of the contrast in series (3) and (4) resembles the t ^−1/2 statistical law, whereas the shuffled series (5) obeys the n ^−1/2 law from n=2 on. Series (2) demonstrates a peculiarly slow decline of contrast, which could be attributed to particular properties of the boundary conditions used in the simulations. Comparisons between the analysed contrast-variation laws indicate quite definitely that the brightness field of solar granulation contains a long-lived component, which could be associated with locally persistent dark intergranular holes and/or with the presence of quasi-regular structures. The suggestion that the random field (4) successfully reproduces the contrast-variation law for the real granulation (Rast in Astron. Astrophys. 392, L13, 2002) can be dismissed.     

The results of the third geodetic campaign in the local geodynamic test area of the MAO NAS of Ukraine

The high-precision coordinates of reference (reduction) points of stations located in the geodynamic area of the MAO NAS of Ukraine were determined in the local topocentric coordinate system. The local geodetic ties (eccentricities) between the reference points of the GPS station “Kiev/Goloseev” and satellite laser location station “Goloseev-Kiev” that are equal to 100.2358 m, ?11.0398 m, ?85.8256 m on the X, Y, Z axes, respectively, were obtained in the ITRF97 system as of the epoch 1997.0. The coordinates of the reference point of the station “Goloseev-Kiev” were determined in the ITRF97 system as of the epoch 1997.0 by adding local geodetic ties to the coordinates of the reference point of the GPS station “Kiev/Goloseev.” They were compared with the estimates of the coordinates of these stations obtained by the methods of cosmic geodesy and geodynamics. The local deformations of the geodynamic area that took place in the 1997–2006 period were estimated and the conclusion was made about the existence of certain trends with respect to the local displacements of the points of the geodynamic area of the MAO NAS of Ukraine.     

Cross-identification between the HIPPARCOS and 2MASS catalogs: The second 2MASS data release (162 million stars)

A cross-identification between the HIPPARCOS and 2MASS (the second data release, 162 million stars) catalogs has been made. This cross-identification has been used to produce a reference infrared catalog of 41143 stars.     

Nonresonant effects and hydrogen transition line shape in cosmological recombination problems

Data on the fluctuations in cosmic microwave background (CMB) radiation, whose accuracy is expected to increase in the immediate future, allow the cosmological recombination of atomic hydrogen and its interaction with the CMB radiation to be studied. Nonresonant effects play an important role in these recombination processes. We consider the quantum-mechanical foundations of the nonresonant processes and present our calculations for the differential two-photon decay rates of the 3s and 3d levels in the hydrogen atom. This article was submitted by the authors in English.     

Gravitational radiation of a differentially rotating superfluid neutron star

The gravitational radiation of a neutron star with a weakly coupled superfluid component is considered. It is assumed that regions can exist in the star's core which rotate at substantially higher angular velocities than the observed angular velocities of pulsars. A star of this sort has a quadrupole moment on the order of the maximum value for the neutron star configurations that have been discussed, so it could be a powerful source of gravitational radiation for the planned Advanced LIGO detector. Translated from Astrofizika, Vol. 51, No. 4, pp. 647–652 (November 2008).     

Cosmological model with a conformally coupled scalar field

Modern concepts of the universe support the assumed existence of a nongravitational source, known as dark energy, for which ε + 3 P < 0 (where ε is the energy density and P is the pressure). This ensures accelerated expansion of the universe. This paper examines a tensor-scalar variant of the theory of gravitation with a conformally coupled scalar field. Various cosmological models are examined and the possible evolutionary development of the universe with accelerated expansion is discussed. Translated from Astrofizika, Vol. 51, No. 4, pp. 653–661 (November 2008).     

The first experience of solar eclipse observations with a miniature torsion balance

We observed the behavior of the pointer of an asymmetric torsion balance (TB) at solar eclipse dates and on other off-eclipse days. A peculiar reaction of the miniature TB different from its reaction at off-eclipse time was recorded for some solar eclipses. The relative positions of the Earth, Moon, and Sun are among the possible factors affecting the position of the TB pointer. A time shift between the maximum phase of a solar eclipse and the maximum TB reaction was detected. We conclude that base observations of such phenomena from different points of the terrestrial globe are necessary.     

Diagnostics of the early explosion phase of a classical nova using its X-ray emission: A model for the X-ray outburst of CI Camelopardalis in 1998

We have computed a spherically symmetric model for the interaction of matter ejected during the outburst of a classical nova with the stellar wind from its optical component. This model is used to describe the intense X-ray outburst (the peak 3–20 keV flux was ～2 Crab) of the binary system CI Camelopardalis in 1998. According to our model, the stellar wind from the optical component heated by a strong shock wave produced when matter is ejected from the white dwarf as the result of a thermonuclear explosion on its surface is the emission source in the standard X-ray band. Comparison of the calculated and observed time dependences of the mean radiation temperature and luminosity of the binary system during its outburst has yielded very important characteristics of the explosion. We have been able to measure the velocity of the ejected matter immediately after the onset of the explosion for the first time: it follows from our model that the ejected matter had a velocity of ～2700 km s^?1 even on 0.1–0.5 day after the outburst onset and it flew with such a velocity for the first 1–1.5 day under an external force, possibly, the radiation pressure from the white dwarf. Subsequently, the matter probably became transparent and began to decelerate. The time dependence of the mean radiation temperature at late expansion phases has allowed us to estimate the mass of the ejected matter, ～10^?7–10^?6 M _⊙. The mass loss rate in the stellar wind required to explain the observed peak luminosity of the binary system during its outburst has been estimated to be \(\dot M\) ～ (1 ? 2) × 10^?6 M _⊙ yr^?1.