UBVR photometry of gas-darkened variable systems. EM Cep

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.     

Variable synchrotron emission from BL Lacertae objects. II. Optical and X-ray flares in HBL source 1ES 1959+650

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.     

Investigation of barred galaxies. V. Surroundings of SB and SA galaxies

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.     

Formation of a mass distribution of objects in an initially uniform field. I. Mergings in a one-component set of particles

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.     

Do Quasi-Regular Structures Really Exist in the Solar Photosphere? I. Observational Evidence

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.     

Associations of very high energy gamma-ray sources discovered by H.E.S.S. with pulsar wind nebulae

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     

The BM Ori System. III. The Depth of the Minimum in the Infrared

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).     

Main stages of evolution of matter in the universe. I

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.     

Barred galaxies. I. A catalog

A catalog of barred spiral galaxies of types SB and SAB with B_T ≤ 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.     

Long-term evolution of orbits about a precessing oblate planet. 2. The case of variable precession

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.     

Color–Density Relation of Galaxies in the Redshift Region of 0.60 < z < 0.75

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.     

Barred galaxies. III. Comparative statistics on SB and SA galaxies in the infrared

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.     

Physical parameters of the continuum emission layer of Mira-type stars. I. Spectrophotometric temperatures

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).     

Moment of inertia of a neutron star. I. Relativistic equation for the accumulated moment of inertia

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.     

Upper limit for the angular momentum of galaxies. I

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.     

Black holes in the Einstein–Gauss–Bonnet theory and the geometry of their thermodynamics—II

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.     

An exact spherically symmetric space–time in Einstein–Cartan theory

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.     

Similarity law in the spectral estimation of a time series. I

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.     

Solar Cycle Predictions Based on Extrapolation of Spectral Components: An Update

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.     

Similarity law in the spectral estimation of a time series. II

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.