bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absolute Eigenbewegungen ausgewählter blauer Objekte in der Nähe des galaktischen Nordpols
Authors: Schilbach E. 
Published: July 2007

AbstractEs werden absolute Eigenbewegungen von 74 blauen Objekten der Größenklassen 16μm5 bis 19μm5 und von weiteren 28 schwachen Sternen (17μm5) in der Nähe des galaktischen Nordpols angegeben. Die absoluten Eigenbewegungen wurden in Bezug auf 45 Referenzgalaxien als Mittel aus 5 im B‐System aufgenommenen Tautenburger Schmidt‐Platten bestimmt. Die mittleren Fehler der Eigenbewegung für einen Stern betragen m̄ = 0˝″0058 und m̄ = 0˝″0069. Für ein blaues Objekt mit einer B‐Helligkeit zwischen 17m̄m0 und 18m̄m0 erreichen diese Fehler die Werte m̄ = 0˝″0059 und m̄ = 0˝″0051, und sie vergrößern sich mit Abnahme der Helligkeit. Für 16 der untersuchten blauen Objekte konnte mit einer Wahrscheinlichkeit von 0.99 die Existenz von Eigenbewegungen nachgewiesen werden.The absolute proper motions of 74 blue objects (from 16m̄m5 up to 19m̄m5) and 28 additional faint stars (17m̄m5) near the galactic north pole are presented. They were derived with reference to 45 galaxies as the mean value from 5 plates taken in the B‐system with the Tautenburg Schmidt telescope.The mean errors of the proper motion of a star are equal to m̄ = 0˝″0058 and m̄ = 0˝″0069. The errors of a blue object with a B‐magnitude between 17m̄m0 and 18m̄m0 are m̄ = 0˝″0059 and m̄ = 0˝″0051 and increase with decreasing brightness. For 16 of the investigated blue objects it was possible to show that proper motions exist with a probability of 0.99.
Turbulent viscosity, magnetic diffusivity, and heat conductivity under the influence of rotation and magnetic field
Authors: Kitchatinov L. L. , Pipin V. V. , Rüdiger G. 
Published: July 2007

AbstractThe old problem of turbulent diffusion is addressed to define the influence of rotation and magnetic field ‐ the usual ingredients of astrophysical bodies ‐ on the effective transport coefficients. Either rotation and magnetism produce the anisotropy and quenching. The tensorial structures of the diffusivities and their dependences on the angular velocity and the field strength are explicitly defined. An example of application of the theory to the global stellar circulation model is given and the implications for cosmic dynamos are briefly discussed.
Investigation of the kinematics and structure of the Galaxy in the vicinity of the North galactic pole
Authors: Kharchenko N. , Schilbach E. , Scholz R.‐D. 
Published: July 2007

AbstractIn the framework of the programme of studying the meridional section of the Galaxy (MEGA) the absolute proper motions of more than 11000 stars with respect to 3000 galaxies and their stellar magnitudes in the B, V Johnson system are determined in two sky regions near the North Galactic Pole (NGP) by means of Tautenburg Schmidt plates. The limiting and completing apparent stellar magnitudes are B = 20.4 and 18.3 mag, the overall and the investigated sky areas are 16.4 and 14.6 square degrees, respectively. Distances have been determined using the stellar magnitudes, colours, proper motions and reduced proper motions. Stellar kinematics, eccentricities of Galactic orbits, spatial distribution and changes of these characteristics with Z‐distance from the Galactic plane are obtained up to 15 kpc. Four subsystems distinguished in the NGP direction, respectively with semithicknesses of 0.25, 0.38, 0.67, 1.48 kpc and density ellipsoid axial ratios of 0.09, 0.20, 0.28, 0.49 show mean velocities in the Galactic rotation direction relative to the LSR of 5.6 ± 0.6, − 11.0 ± 0.6, − 62.5 ± 1.2, − 181.6 ± 4.4 km/s, and ages of 0.1, 0.4, 0.9, 1 of the Galaxy age.
Autocorrelation function bias owed to a limited number of de‐trended observations. Applications to autoregressive models with noise
Authors: Andronov I. L. 
Published: July 2007

AbstractAnalytical expressions were derived for the expectation of the autocorrelation function (ACF) corresponding to lowfrequency least squares fits and deviations from them in the case of a limited number of observationsN. A vector of values of the autocovariation function may be obtained by multiplication of aN . NmatrixZ(dependent on concrete basic functions used for trend determination) by a vector of the unbiased ACF. Because much computational time is needed to obtain such a matrix, its components are to be computed once for concreteNand basic functions, and then stored as a file. An algorithm is proposed for determining the contribution of the correlated signal to the ‘signal+noise’. The expressions are written for general form of the ACF, and illustrated by the application to autoregressive models. The statistical properties of the model parameters are studied. The method is applied to cataclysmic binaries AM Her and TT Ari. The precise expressions allow us to obtain reliable results and to avoid misinterpretation being possible when using the approximate methods.
Cr 135 revisited
Authors: Amieux G. , Röser S. 
Published: July 2007

AbstractIn this paper we combine information on photometry, radial velocities and proper motions to study the nature of the suspected open cluster Cr 135. For the first time we introduce proper motions of a large number of stars in the region of Cr 135 into the discussion. The proper motions taken from the PPM catalogue favour the hypothesis that Cr 135 is a real open cluster with at least 12 members at a distance of 300 pc having a space motion U, V, W of (−11, −13, −15) km s−1. But still more accurate observations are needed to separate it from the field stars without any doubt.
Scalar field instability in multi‐dimensional cosmology
Authors: Bleyer U. , Zhuk A. 
Published: July 2007

AbstractThe scalar field theory on the background of cosmological models with n(n ≥ 1) spaces of constant curvature is considered. We take the integrable case of Ricci flat internal spaces. The coupling between the scalar and the gravitational fields includes the minimal coupling as well as the conformal case. In the ground state of the scalar field we find the conditions for vacuum instability realized for most of the possible solutions to Einstein's equations if the coupling parameter takes appropriate values. For the excited states of the scalar field we show the induction of massive modes and discuss their properties.
Generalized de Sitter solution in multi‐dimensional cosmology with static internal spaces
Authors: Zhuk A. 
Published: July 2007

AbstractA multi‐dimensional cosmological model with space‐time consisting of n(n ≥ 2) Einstein spaces Mi is investigated in the presence of a cosmological constant λ and a homogeneous minimally coupled free scalar field. A generalized de Sitter solution was found for λ > 0 and a Ricci‐flat external space for the case of static internal spaces with fine tuning of parameters.
Size scale of the R Coronae Borealis variables
Authors: Rosenbush A. E. 
Published: July 2007

AbstractThe radius of R CrB is estimated to 90–100 radii of the Sun. The dust layer, which is the cause of the deep minimum in the visible light of R Coronae Borealis‐type stars, has a radius of about 6 radii of the star. This follows from the delay of the infrared light increase after the visual minimum and also from the analogy with the dust formation in novae. The emission lines appearing in the minimum have an origin analogous to the metal emissions in the comets of 1882 II and 1965 VIII in which they were observed at a distance of 20–30 R⊙. The permanent dust shell has a radius about of 26 stellar radii.
Revealing of periodicities in the variations of differential rotation of the Sun
Authors: Gigolashvili M. Sh. , Gogoladze N. A. , Khutsishvili E. V. 
Published: July 2007

AbstractIt is presumed that a north‐southern asymmetry of a solid‐body rotation of large spots, depending on even and odd solar activity cycles (Gigolashvili and Khutsishvili 1 1989, 1990) may possibly be explained by the asymmetry of the appearance of large structures with strong magnetic fields in the corresponding hemispheres.Spectral analysis of the observational data shows the presence of cyclic variations of differential rotation of large‐ and middle‐sized spots. Variations of differential rotation of small spots are either absent or overlapped by noise.It is also supposed that the discovered and most frequently realized component of the spectrum of solar differential rotation variations — a four‐years periodicity — may be either a real phenomenon or the result of overlapping of multiple quasi bi‐annual variations.
On the Behaviour of Test Matter in the Neighbourhood of Caustics of Homogeneous Cosmological Models
Authors: Paul H. G. 
Published: July 2007

AbstractUsing power asymptotes for the metric of the metric of the BIANCHI types I, V, VIIO, VIII and IX the intensity of geodesic focused scalar test matter is calculated in the neighbourhood of the caustic singularity of these space‐time models. In all considered BIANCHI types there is a caustic diffraction field bounded by regions of extinction depending on the structure of the gravitational lense.
New Light Curve Analyses for the Eclipsing Binaries u Her and UV Leo
Authors: Giuricin G. , Mardirossian F. , Mezzetti M. 
Published: July 2007

AbstractUsing WOOD's (1972) model we have analyzed two sets of photoelectric observations as yet unsolved, i.e., ROVITHIS' and ROVITHIS‐LIVANIOU's (1980) B and V light curves of the semi‐detached system u Her and BROGLIA's (1961) three‐colour observation of the detached system UV Leo.The observations of u Her have yielded solutions in which the secondary's radius exceeds its ROCHE lobe. On the other hand, our new elements of UV Leo confirm the most recent investigations, thus giving for the primary eclipse an unexpected occulatation solution which hardly permits a simple picture of UV Leo.
Limits to Intergalactic Neutral Hydrogen from Photoionization Absorption in Ultraviolet Quasar Spectra
Authors: Dautcourt G. 
Published: July 2007

AbstractMeasurement of the continuum beyond the LYMAN limit in the spectra of highly redshifted quasars allows to put upper limits to intergalactic neutral hydrogen which are comparable to those derived from the GUNN‐PETERSON‐SCHEUER‐SCHKLOWSKI test. The data apply to a weighted average of neutral hydrogen along the whole line of sight to the quasar, not to a small region around the quasar as in the GPSS test. Some conclusions are derived for a possible clumped component of neutral hydrogen in different FRIEDMAN models.
Die MARKARJAN‐Galaxienkette im Sterbild Virgo
Authors: Litzroth E. 
Published: July 2007

AbstractDen von MEURERS untersuchten zwei Strukturvarianten der MARKARJAN‐Galaxienkette im Sternbild Virgo wird eine dritte, wahrscheinlichere Variante hinzugefügt. Eine Untersuchung der Abstands‐Geschwindigkeits‐Beziehungen dieser Variante zeigt, daß von den acht Galaxien der Kette sieben zu demselben kinematischen Kettensystem gehören. Dieses rotiert wie ein starres Gebilde mit gleicher Winkelgeschwindigkeit, wobei es sich zugleich mit einer Geschwindigkeit von etwa 700 km/s von uns entfernt. Die Galaxie NGC 4374 am Rand der MARKARJAN‐Kette gehört offenbar nicht zu diesem einheitlich rotierenden Kettensystem, da sie nicht in die Abstands‐Geschwindigkeits‐Struktur dieses Systems paßt.
Stress‐Energy Density Tensor of Isotropic Homogeneous Universe
Authors: Popić R. V. 
Published: July 2007

AbstractThe relation between timelike and spacelike components of the stress‐energy density tensor is obtained from EINSTEIN equations in ROBERTSON‐WALKER metrics. The timelike component of the stress‐energy density tensor is developed as a power series of cosmological scaling radius. FRIEDMANN cosmology is recognized as a part of a more general cosmology.
Koordinateninvariante Erhaltungssätze in der Schwarzschildgeometrie
Authors: Burghardt R. 
Published: July 2007

AbstractDie Einsteinschen Feldgleichungen für das Schwarzschildfeld werden so umgeschrieben, daß in ihnen nur meßbare Größen vorkommen. Die Austdrücke sind völlig koordinateninvariant, jedoch vom Beobachter abhängig. Verallgemeinerte Lorentztransformationen im Sinne von TREDER vermitteln zwischen den Meßwerten verschiedener Beobachtersysteme. Die Feldgleichungen enthalten einen Ausdruck für die Energie und die Spannungen des Gravitationsfelds, die kovariante differentielle Erhaltungssätze erfüllen.
A Second‐order Correlation Approximation for Thermal Conductivity and Prandtl Number of Free Turbulence
Authors: Eschrich K.‐O. , Rüdiger G. 
Published: July 2007

AbstractBy means of a linearizing approximation we determine the scalar thermal eddy conductivityχTin its dependence on the spectral function of the (given) turbulence and the microscopic conductivityχ. The discussion of the profileχT(χ) reveals the importance of the shape of the frequency spectrum of the velocity fluctuations. Spectra which decrease with increasing frequency produce eddy conductivities which decrease with increasingχ. A distinct peak in the frequency spectrum corresponds to a non‐trivial maximum of theχT‐profile. These general findings are confirmed by examples some of which are numerical. Very small molecular diffusivities generally lead to a turbulent PRANDTLnumber of 0.4in rough accordance whith most of the measurements. For large diffusivities, however, the turbulent PRANDTLnumber behaves inversely to the molecular PRANDTLnumber. We have to doubt thus the general belief that eddy conductivity always exceeds eddy viscosity. For the effective PRANDTLnumber of the Sun we find an upper limit of 0.3. An application of our theory to the smallscale motions in the upper Earth core yields values of 0.4.
The Light Curve Changes of VW Cephei
Authors: Kotarska I. , Glownia Z. 
Published: July 2007

AbstractA long series of photoelectric observations of the W UMa‐type eclipsing binary VW Cephei collected since 1952 is discussed. The so‐called KWEE effect is examined — regarding the heights of maxima and the depths of minima — in order to detect periodicities i n the light curve changes. The frequency analysis reveals periodicities at the small homogeneous observational domains only, but the power spectrum (in sence of DFT) of all observations is very complicated for exact interpretation. The light curve changes are entirely real much exceeding the possible errors, but they have lost their periodic character in the whole discussed time interval.
Large‐scale distribution of clusters of galaxies
Authors: Schmidt K.‐H. 
Published: July 2007

AbstractThe redshifts of 576 clusters of galaxies have been compiled from literature. This sample was used to study the large‐scale distribution of clusters up to about z = 0.15. The distribution of the clusters reveals several chains and filaments 50 to 200 h−1 Mpc in size. There are many empty regions and holes, too, some of them known previously.
The interstellar 2200 Å band: A second catalogue of equivalent widths and preliminary statistical analysis (Mitteilungen der Universitäts‐Sternwarte zu Jena Nr. 162)
Authors: Friedemann C. , Gürtler J. , Schielicke R. , Dorschner J. 
Published: July 2007

AbstractA second catalogue of equivalent widths of the interstellar 2200 Å band is presented. It is based on spectrophotometric data obtained with the TD‐1 satellite and supplements a catalogue already published (paper I). Both catalogues list a total of 779 stars. The reliability of the derived parameters is analysed. There is a satisfying agreement with spectrophotometric data obtained with the OAO‐2 satellite. The relationship between the equivalent width of the 2200‐Å band and and the colour excess is discussed, making use of additional data for more strongly reddened stars obtained with OAO‐2 and IUE.
On the Past Star Formation Rate in the Solar Neighbourhood
Authors: Meusinger H. 
Published: July 2007

AbstractThe present day mass function (PDMF) is derived from the data material of the immediate solar neighbourhood. From the comparison of the lower mass part (R<R) and the high mass part of the PDMF it is estimated that the mean past star formation rate related to the present one is in the range 0.08—2.0, supposed the initial mass function (IMF) is time independent. References to probable time dependences of the IMF are summarized. Using the PDMF as a constraint on the temporal variation of the IMF, unplausibilities for the star formation rate result if the IMF monotonously flattens in time uniform over the whole mass range.
Photometrische Untersuchungen im Zentralgebiet der Praesepe (NGC 2632)
Authors: GÖtz W. 
Published: July 2007

AbstractIn Ergänzung der photometrischen Skala in der Zentralregion der Praesepe und ihrer Erweiterung auf schwächere Sterne wurde eine photographische Photometrie im UBV‐System auf Platten der Schmidtkamera (134/200/400 cm) des Karl‐Schwarzschild‐Observatoriums durchgeführt. Die bereits bekannten photometrischen Daten von Sternen, die von HAFFNER, HECKMANN und WEIS erhalten wurden, wurden durch (U – B)‐Farbenindizes vervollständigt. Außerdem wurde eine Anzahl von helleren und schwächeren Sternen, Haufenmitgliedern einschließlich weißer Zwerge und Feldsternen, untersucht, um eine photometrische Skala bis zu V ≈ 18.m9 zu erstellen. Eine Umgebungskarte, in der alle gemessenen Sterne gekennzeichnet sind, wird gegeben.
Berücksichtigung inhomogenen Hintergrundes bei der Irisblendenphotometrie
Authors: Ziener R. 
Published: July 2007

AbstractVerschiedene Methoden der Berücksichtigung inhomogenen Hintergrundes bei der Irisblendenphotometrie werden miteinander verglichen. Dabei werden sowohl Meßwerte von SCHAEFER (1979, 1981) als auch eigene Messungen auf Tautenburger Platten herangezogen. Schließlich werden einige Regeln für die Messung von Platten mit Hintergrundinhomogenitäten gegeben.
An Unusual Group of Low Surface Brightness Galaxies in the Region 1046 + 65
Authors: Börngen F. , Karachentseva V. E. , Karachentsev I. D. 
Published: July 2007

AbstractA complex of 11 objects with a surface brightness of about 26 mag/□” is detected in the direction of the M81 group of galaxies. The argumentes are presented in favour of the fact that they are at the distance of the M81 group; their linear diameters (2 to 3 kpc) and absolute magnitudes (MB = ‐11m to ‐12m) are in agreement with the parameters of the known dwarf galaxies of the Local group. An assumption about the tidal stability of the complex of dwarfs relative to M81 gives an estimation of its summary mass ≳ 1 · 108 M ⊙ and of its mass‐to‐luminosity ratio ℜ/L ≳ 1.2 in the solar units.
Error Analysis for the Astrometric Determination of Absolute Proper Motions by means of a Monte Carlo Simulation
Authors: Hirte S. , Neumann P. 
Published: July 2007

AbstractFor the determination of positions and proper motions of celestial objects until now only corrections of errors caused by the instrument and by the atmosphere have been carried out. Errors of measurement as random errors have not been considered. Therefore a Monte Carlo simulation of the propagation of these random errors in the calculation of the so‐called averaged measurement coordinates and the proper motions were undertaken. As a typical quantity, the corresponding standard deviation was estimated, and its dependence on occuring parameters was studied. With this method, the true values of the considered quantities are known (generated by simulation) so that the errors of the calculated quantities can be directly determined. Inferences to the accuracy of a single measurement were made.
The Physical Nature of the Blue Objects in the Field of BD + 15° 2469 (Virgo Cluster)
Authors: Abati L. E. , Lorenz H. 
Published: July 2007

AbstractThe physical nature of 277 ultraviolet excess objects of the third Asiago field (22 square degrees, 15 ≦ mpg ≦ 18, U–B ≦≦ ‐0.2) is investigated on the basis of objective prism plates. Most of them are stars, 8% are quasar candidates and 7% compact galaxies. The proportions of different kinds of objects changes with the magnitude and U–B colour index. The surface density of quasars is estimated to be between 0.5 Q/sq. deg. and 1.0 Q/sq. deg. for the UVX A3 objects.The results of the A3 field (located in the Virgo cluster of galaxies) statistically agree with the ones of the A1 field, outside clusters of galaxies.
Mean Magnetic Field in Renovating Random Flow
Authors: Dittrich P. , Molchanov S. A. , Sokoloff D. D. , Ruzmaikin A. A. 
Published: July 2007

AbstractAn integral equation is derived for a mean magnetic field in a random velocity field that renovates after a characteristic time τ. It is shown that in two cases, i.e. when (a) the correlation time is short, τ < l/v0 (where l and v0 are the characteristic scale and velocity), and (b) for long wave components of the field, k−1 ≫ v0τ, the equation is reduced to the differential one, whose form has first been given by STEENBECK, KRAUSE and RÄDLER. Expressions for the equation coefficients are obtained in the two above cases. In a general case the integral equation cannot be reduced to the differential one although its spectral properties are close in a certain sense to those of the SKR‐equation. There are differences, however (specifically, the integral equation yields a higher rate for the field growth), that are shown on the example of the Gaussian distribution (at time renewal) of particles moving along random paths.
Theory of stellar magnetic activity: A review
Authors: Belvedere G. 
Published: July 2007

AbstractThe unified sight of solar and stellar activity has revealed a worthwhile concept under several aspects, gaining in the last decade the increasing favour of observers and theorists, and the term solar‐stellar connection has recently been introduced to point out the complementarity of solar and stellar observations in the background of the basic role of the magnetic field.The great development of ground and space stellar activity observations suggests a much wider scenario than it were possible to imagine even a few years ago, and stimulates theoretical work, most of which is in the framework of the α–ω dynamo theory. Dynamo models of stellar activity in the main sequence, although subjected to different assumptions, do converge in predicting that activity should increase with the increasing angular velocity of rotation ω and colour index (B–V), in agreement with almost all existing observational evidence. However, even if linear dynamo theory seems to have captured the essentials of the mechanism of stellar activity, the complexity of stellar activity phenomenology and operation modes suggests that the future is in the non‐linear approach.Finally, observational and theoretical uncertainties and difficulties, which affect the present status of dynamo theory, are briefly discussed.
Bimodal mass and angular momentum losses by magnetically controlled winds during stellar evolution
Authors: Castellani V. , Paternò L. 
Published: July 2007

AbstractIn recent times evidence for bimodal distributions of stars in the H–R diagram has reached a striking evidence. These bimodal distributions seem to be correlated with a bimodal distribution of masses and angular velocities. The approach we propose to explain the observed bimodality suggests that this latter is due to a bimodal mass loss by magnetically controlled stellar winds during stellar evolution, owing to different magnetic field configurations. It is assumed a mechanism analogous to that which produces solar wind, with magnetic field generated by dynamo working in the convection zone. Different field geometries (dipole cr quadrupole), which depend on the mode the dynamo operates, can produce different but discrete mass losses during stellar evolution, thus producing bimodal distributions of masses and angular velocities.