bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Planetary Nebulae towards the galactic bulge I. Objects in the central area
Authors: Kohoutek L. 
Published: July 2007

AbstractIn the first part of this study of PN towards the galactic centre we present the discovery of 24 new planetary nebulae found on the objective‐prism spectra in three ESO fields (Table 1 ‐ parameters of the survey, Tables 3 and 4 ‐ new objects). The observations of those objects are listed in Table 5. Besides, we give the classification and the positions of known objects in this area (Table 2).
Photometry of groups of galaxies. II. The NGC 972 group
Authors: Vennik J. , Richter G. M. 
Published: July 2007

AbstractA nearby group of galaxies, centered at the spiral galaxy NGC 972 and conspicuously rich in faint dwarf spheroidal galaxies, has been investigated photometrically on the B and V plates, obtained with the Tautenburg 2m Schmidt telescope. For ten certain and probable group members the equivalent B and V brightness profiles have been extracted. Integrated magnitudes and mean colours of faint group members have been estimated. Typically, the dwarfs show a “subexponential” (i.e. a convex curvature over the linear radius) surface brightness profile and often a central excess. Their equivalent profiles are reasonably well fitted by modified isothermal (King) models.
Variable objects with UV excess in the surroundings of M33
Authors: Richter G. A. , Börngen F. , Afanas'ev V. , Karachentsev I. D. , Kopylov A. 
Published: July 2007

Abstract13 objects, motly with UV excess, in a field of about 10 square degrees in the surroundings of the Triangulum galaxy were investigated and classified, using photometric, spectroscopic, and proper motion data. 9 of them are probable quasistellar objects, 3 cataclysmic variables, and 1 eclipsing binary.Die Arbeit enthält für 13 veränderliche Objekte, überwiegend mit UV‐Überschuß, die Ergebnisse der Klassifizierung auf Grund von photometrischen, spektroskopischen und Eigenbewegungs‐aten in einem etwa 10 Quadratgrad großen Feld in der weiteren Umgebung von M33. Unter diesen Objekten sind 9 vermutlich quasistellare Objekte, 3 kataklysmische Doppelsterne und ein Bedeckungsstern.
Ein Vorschlag zur Erzielung hochreflektierender Teleskop‐Optik
Authors: Schmidt‐Kaler T. H. 
Published: July 2007

AbstractSince 60 years the common method generally used to coat astronomical mirrors is vacuum deposition of pure aluminium by evaporation. Such mirror surfaces degrade very fast resulting in a considerably reduced optical throughput. Protecting layers (oxides like SiO2, fluorides like CaF2) are not applied because their removal, necessary before realuminization, involves damage to the optical surface of the mirror substrate which would necessitate a costly refiguring of that surface. The reduction of the throughput exceeds typically 30 % for a Cassegrain system; it precludes the introduction of excellent optical design solutions in astronomy based on Schwarzschild's theory using four‐reflection optics. In addition, the cost of the conventional procedure of aluminizing and its risks increase tremendously with the size of the mirrors of the very large telescopes now planned or under construction. Here I propose a three‐layer composion in two forms (Fig. 1): a) stopping layer ‐‐ reflecting layer ‐ protecting layer, or b) carrier layer ‐ protecting layer. The stopping layer is supposed to be completely insensitive to the chemical agents dissolving or detaching the protecting (and the reflecting) layers. On the other hand, in modification b), the carrier layer is supposed to be chemically removable from the substrate, thereby detaching also the protecting (and reflecting) layer. As an example for a layer system of type a) experiments are under way with the system gold/silver/quartz on various mirror substrate materials. Quartz can be easily dissolved by fluorid acid without any damage to the gold stopping layer. Dense. pore free Al2O3+SiO2 layers without defects can be expected to protect the silver reflectance R⩾ 0.98 under real observatory conditions effectively for more than 10‐20 years. In addition this protecting layer permits frequent and effective cleaning of the mirror from dust etc. The reflectance of silver exceeds that of fresh conventionally aluminized mirrors with R ≅ 0.87 for all wavelengths λ ⩾ 3370 Å. In the blue the silver mirror realizes with R = 0.995 ideal conditions for Schwarzschild optics. In the V‐IR region it is with ≅ 0.99 by the factor 1.2 better than present‐day mirrors.
Rapid variability of active galactic nuclei: The 160min periodicity in NGC 3516, NGC 4151 and Quasar 3C 273
Authors: Kotov V. A. , Haneychuk V. I. , Lyuty V. M. 
Published: July 2007

AbstractThe analysis of all the available data between 1968 and 1991 on rapid variability of optical and X‐ray luminosity of three AGNs, NGC 3516, NGC 4151 and 3C 273, shows the presence of small‐amplitude (˜ 1 %) but statistically confident (≈︁ 5s̀) periodicity of 160.0105 (± 6) min. Within the error limits it coincides with the period P0 = 160.0101 (± 1) min of global oscillations of the Sun. An independence of the observed period on AGN red shift z favours the hypothesis about a cosmological origin of the 160min oscillation.
Black hole stability in multidimensional gravity theory
Authors: Bleyer U. , Melnikov V. N. , Bronnikov K. A. , Fadeev S. B. 
Published: July 2007

AbstractExact static, spherically symmetric solutions to the Einstein‐Maxwell‐scalar equations, with a dilatonic‐type scalar‐vector coupling, in D‐dimensional gravity with a chain of n Ricci‐flat internal spaces are considered. Their properties and special cases are discussed. A family of multidimensional dilatonic black‐hole solutions is singled out, depending on two integration constants (related to black hole mass and charge) and three free parameters of the theory (the coordinate sphere, internal space dimensions, and the coupling constant). The behaviour of the solutions under small perturbations preserving spherical symmetry, is studied. It is shown that the black‐hole solutions without a dilaton field are stable, while other solutions, possessing naked singularities, are catastrophically unstable.
Spectroscopic verification of suspected planetary nebulae. III.
Authors: Kohoutek L. , Pauls R. 
Published: July 2007

AbstractClassification of eight objects as planetary nebulae (Table I/A) was confirmed according to our image tube spectra; as to further two objects (Table 1/B) their status remains unclear. In Table 2 we give estimates of line‐strengths, derived heliocentric radial velocities and their standard deviations.
New mass formula for spherically symmetric stellar configurations
Authors: Bleyer U. , Sh. Grigorian L. , Avakian R. M. , Chubarian E. V. 
Published: July 2007

AbstractA new formula is derived for the mass of spherically symmetric stellar configurations. An expression will be given where the mass square is connected to an integral over the pressure of gravitating matter. This formula turns out to hold for Newtonian gravity, for Einstein's GRT, for projective and bimetric scalar‐tensor and further theories of gravitation.
Duplicity amongst HIPPARCOS stars
Authors: Brosche P. , Odenkirchen M. , Tucholke H.‐J. 
Published: July 2007

AbstractStars observed by the astrometry satellite Hipparcos may be unknown double stars. A subsample of those are dangerous for the extragalactic link of Hipparcos proper motions by long‐term photographic proper motions, if the time base of Hipparcos is too short to detect the orbital motion. The probability of these cases and the typical size of the photocentric orbital motion are estimated by Monte Carlo simulations for the sample of 33 stars used in the Bonn extragalactic link. Both are found to be considerable: about 16% and 9 mas/yr respectively.
Variations of the IMF Bz component over a solar activity cycle for different regimes of solar wind formation
Authors: Kovalenko V. A. , Molodykh S. I. 
Published: July 2007

AbstractThe behavioural features of the IMF Bz component for different solar wind velocity regimes have been studied. The study revealed a significant difference in variations of the Bz component between high‐speed and low‐speed regimes. Formation mechanisms for the IMF meridional component as well as the relationship of Bz with dynamical properties of the large‐scale magnetic fields on the Sun are discussed.
Equations for transfer of radiation in plasma at decay interactions with ionacoustic waves
Authors: Lomadze R. D. 
Published: July 2007

AbstractEquations for spectral energy densities of waves are obtained describing transfer of high frequency radiation through plasma without magnetic field at the decay of electromagnetic waves into electromagnetic and ionacoustic ones, as well as the decay of Langmuir waves into Langmuir and ionacoustic ones in case of isotropic distributions of all the above waves.
Hierarchical dark matter from fragmenting macroscopic superstrings
Authors: Brosche P. , Tassie L. J. 
Published: July 2007

AbstractDark matter is explained within our scenario of the formation of the universe from the decay of macroscopic superstrings. The observed increase of the fraction of dark matter with the hierarchical rank of astronomical objects is explained by assuming that about 90% of superstrings of each rank decay into unbound fragments. The dark matter consists essentially of asteroids and smaller objects which are not bound to stars.
Stream formation in W Serpentis‐type binaries
Authors: Karetnikov V. G. , Menchenkova E. V. , Nazarenko V. V. 
Published: July 2007

AbstractBy the method proposed by Nazarenko (1993) and using observational data obtained by different authors, the physical conditions in the stream in the neighbourhood of the inner Lagrangian point L1 were calculated for three interacting binary systems of W Ser‐type: β Lyr, V367 Cyg, RY Sct. It is shown, that as a result of the evolutional expansion of the mass losing component the deep layers of its atmosphere reach the neighbourhood of the first Lagrangian point L1 and a stream of axial symmetric shape is formed. Its radius is comparable to the dimension of the mass losing component. The rate of the mass transfer increases up to 10−5 M⊙/yr. The calculated parameters of the stream in the neighbourhood of the point L1 explain the main observational properties of the investigated systems (existence of extended circumstellar matter with a developed structure, high mass transfer rate).
Positions of 46 radio stars: Observations of 1984–1985 and 1989–1991
Authors: Tel'nyuk‐Adamchuk V. V. , Molotaj O. A. , Gregul O. Ya. 
Published: July 2007

AbstractThe results of observations of 46 radio stars carried out with the Repsold meridian circle of the Kyyiv University Observatory in 1984–1985 and 1989–1991 are presented. The main goal of these observations is to improve the optical positions of radio stars for determination of a relationship between the optical and VLBI reference frames. The standard errors of averaged positions in two catalogues amount to 0.2 arcsec. These results were compared with those obtained with the Bordeaux meridian circle.
Filaments and large‐scale magnetic fields
Authors: Maksimov V. P. , Prokopiev A. A. 
Published: July 2007

AbstractWe have used Stanford magnetic field maps to construct distributions of longitudinal magnetic field gradients in the neighbourhood of polarity inversion lines. The distributions were constructed with proper account of the type of the polarity inversion lines and of the existence or absence of dark filaments above them. It is shown that for polarity inversion lines that pass inside active regions or on their boundary, grad BII distributions for portions of the lines with persisting filament are shifted toward lower values of gradient as compared with grad BII distributions for portions of the lines without filaments. The influence of the spatial resolution of the magnetograms upon polarity inversion line characteristics is discussed.
Brightness profiles of C3 and NH3 in the atmosphere of P/Brorsen‐Metcalf
Authors: Korsun P. P. 
Published: July 2007

AbstractSpectroscopic observations of Comet P/Brorsen‐Metcalf were made on August 9–13, 1989. Spatial profiles extracted from long‐slit spectra were analyzed to determine the lifetimes of C3 and NH2 radicals and their parents, as well as the tailward acceleration of these radicals. In our investigations we used a Monte Carlo model. The average lifetime for C3 has been found to be 6.3 × 104 s and that for the parent of C3 to 6 × 103 s. The spatial profiles of C3 were almost symmetric and we need only 0.1 cm s−2 as the tailward acceleration. According to our simulations, C3H4 (allene) can be considered as the parent for C3. We obtained the average value 7.6 × 104 s for the lifetime of NH2 and 1.1 × 104 s for the lifetime of the NH2 parent. The tailward acceleration of NH2 was not more than 0.1 cm s−2. This result does not exceed the latest theoretical calculations of NH2 and NH3 lifetimes by a factor of 1.4. So, NH3 may be considered as a parent for NH2 in the atmosphere of P/Brorsen‐Metcalf.
Programme of the Galactic meridian: Star counts and galactic models. 1. Distributions of stellar magnitudes and colours
Authors: Andruk V. , Kharchenko N. , Schilbach E. , Scholz R.‐D. 
Published: July 2007

AbstractA comparison of observed stellar distributions with a three‐component model of the Galaxy is presented. The analysis is based on photometric and photoelectric data obtained along the main Galactic meridian and in two fields near the North Galactic pole (programme MEGA). The assumed model considers the Galaxy as composed of the disk (main sequence and disk red giants), the thick disk and spheroid populations. To model the observed colour distribution, we distinguish main sequence stars and disk red giants as the disk subsystem; white dwarfs, subdwarfs and intermediate giants as the thick disk subsystem; extreme subdwarfs, spheroid giants and horizontal branch stars as the spheroid subsystem.A statistical relation between the apparent and absolute magnitudes of stars which make the maximum contribution to the star counts for a given disk subsystem is derived.In order to achieve the best agreement between the model and observations, we fit the values of the ‘dip’ (aw) of the disk luminosity function, the correction to the absolute magnitude of disk red giants (ΔMVRG) and the expression for interstellar extinction. As the main result, we obtained aw = 0.6 (logarithmic scale) and ΔMVRG = 0.5 mag; the interstellar extinction has to be taken into account by the modified Sandage law.
A refined model for the influence of ocean tides on UT1 and polar motion
Authors: Seiler U. , Wünsch J. 
Published: July 2007

AbstractPeriodic changes in Universal Time and polar motion have been derived from a numerical ocean model for a number of small partial tides. Combined with the results reported earlier our model now includes the 34 most important constituents of degree 2 (measured by the amplitude of the tidal potential). The results show that the terms neglected in all existing models amount to 80 μs in UT1 and to 0.3 mas in polar motion.
Position Angle Variation of the Major Axis of some Galaxies
Authors: Gamaleldin A. I. , Issa I. A. 
Published: July 2007

AbstractThe variation in the direction of the major axis in three ellipticals, five lenticulars and three spirals has been studied using B or V isophotic maps. It is noticed that there is a turn point in most of the curves especially for spirals and lenticulars. This turn point can be used to define the galaxy nucleus region.There seems to be a correlation between the rotation curve and the position angle curve especially for NGC 2784 and NGC 3640
Stellarstatistische Untersuchungen in der Sonnenumgebung
Authors: Guseva N. G. , Kolesnik L. N. , Metreveli M. D. 
Published: July 2007

AbstractSpace densities for stars given in the „Catalogue of nearby stars”︁ and in „Nearby star data published 1969—1978”︁ were calculated for the stellar groups listed in Table 1 as a function of the distance from the galactic plane. The stars are symmetrically distributed with respect to the galactic plane. Space densities for giant stars nearer than 22 pc were also computed. The comparison between the luminosity functions of stars nearer than 5 pc and 22 pc shows that the number of M dwarfs up to 22 pc is given uncompletely.
Softening Effects in the Equation of State and Influence of General Relativity on the Outcome of Stellar Collapse
Authors: Kämpfer B. 
Published: July 2007

AbstractHydrodynamical evolution of a collapsing stellar core is followed to test the influence of general relativity and of softening effects in the equation of state. The general relativistic treatment of the collapse does not show any spectacular deviation from the Newtonian treatment. In particular there is no indication within the standard scenario for potential barrier penetration and continued collapse to a black hole. In the case of strong electron capture during the collapse the nuclear matter equation of state is of importance. A softening according to a phase transition below the bounce density is found to reduce the shock strength, but the shock is strong enough to cause the usual blowing‐off.
REDUCE programs for algebraic computation in general relativity
Authors: Dautcourt G. , Jann K.‐P. 
Published: July 2007

AbstractREDUCE programs for algebraic computation in General Relativity are presented which use the metric tensor as input. The programs calculate — according to the user's option — the CHRISTOFFEL symbols, the RIEMANN tensor, the RICCI tensor, the RICCI scalar, the EINSTEIN tensor and the WEYL tensor.
Zeitlich periodische Variationen des solaren Neutrinoflusses und das Standardmodell der Sonne
Authors: Haubold H. J. , Gerth E. 
Published: July 2007

AbstractDie FOURIER‐Transformation der von DAVIS gemessenen 37Ar‐Erzeugungsrate im solaren Neutrinoexperiment weist auf zeitliche Variationen des Neutrinoflusses mit Perioden von 100.0, 58.8, 35.7, 25.6, 19.6, 15.2, 8.8 und 6.3 Monaten hin. Wir diskutieren physikalische Voraussetzungen des Standardmodells der Sonne, die nicht allgemein mit den Beobachtungen übereinstimmen und führen Pulsationen des solaren Neutrinoflusses mit der Zeitskala von Jahren auf im Sonneninneren angeregte Schwerewellen zurück.
Modulation of Solar Constant by Active Regions during 1980
Authors: Pap J. 
Published: July 2007

AbstractIrradiance records of the Nimbus‐7 and SMM satellites indicate a systematic downward trend of the solar constant of the order of a few hundredths of a percent and a slow variation of the solar constant on a time scale from days to weeks. The reason for the downward trend is not known as yet; it seems that the slow variation of the solar constant is linked with the solar rotation period via the effect of solar active regions.This paper deals with the connection between the solar constant variation and the age of the solar active regions. It seems that decreases in the solar constant took place when sunspot groups developing quickly in time and space with complex structure occurred on the solar disk. On the other hand, when the “older” groups with simple structure were dominant the value of the solar constant increased slightly or these groups could reduce the effects of “younger” groups.
On the Structure of the Perseus Cluster of Galaxies
Authors: Baier F. W. 
Published: July 2007

AbstractThe investigation of the distribution of number densities and radial velocities in the Perseus cluster led us to the conclusion that this cluster possesses dominant substructures. This result is in agreement with a corresponding result for the Hydra‐I cluster and with former conclusions of different authors that substructures are a typical phenomenon for a high percentage of all clusters of galaxies. The complex of the Perseus cluster has a diameter of 60–80 minutes of arc.
On the Structure of the Coma Cluster of Galaxies
Authors: Baier F. W. 
Published: July 2007

AbstractThe investigation of the distributions of number densities and radial velocities in the Coma cluster led us to the conclusion that this cluster possesses substructures. This result is in agreement with corresponding results for the Hydra I cluster and the Perseus cluster and with former conclusions by different authors that substructures are a typical phenomenon for a high percentage of all clusters of galaxies.
Solar magnetism: Observation and theory
Authors: Stix M. 
Published: July 2007

AbstractThis introductory review consists of four parts. The first is a discussion of the concentration of magnetic flux into small elements, the large electrical conductivity and the superadiabatic stratification as the main reasons for these “flux tubes”, their relationship to the mean field, and the observational evidence of the latter. The second briefly repeats the approximations and merits of kinematic mean field dynamos. In the form of the αω‐dynamo, this theory esplains the reversals, latitude migration, dipolar parity and other properties of the mean solar field. The third part treats the question of flux loss from the bottom of the convection zone, or in a transition layer beneath it. The last part discusses further dynamic aspects of the Sun's magnetism, e.g. models of limit cycles and models with chaotic behaviour and in particular the question of phase stability of the solar cycle.
The energy flux number and three types of planetary dynamo
Authors: Stevenson D. J. 
Published: July 2007

AbstractIt is proposed that the existence and nature of a planetary dynamo can be characterized by a dimensionless number Φ ≡ FeR/ϱλ2ω, called the energy flux number, where Fe is the energy flux available for dynamo generation, R is the core radius (or thickness of the dynamo generating region), ϱ is the fluid density, λ is the magnetic diffusivity and ω is the angular velocity. For Φ ≲ 1, there is no dynamo. For 1 ≲ Φ ≲ 102.5 there is an “energy‐limited dynamo”, in which Fe is insufficient to enable the dynamo to reach the dynamically desirable state A ≡ B2/8πϱλω ∼ 1, where B is a typical field amplitude (in Gauss). For 102.5 ≲ Φ ≲ 105, there is a dynamically determined dynamo (Λ ∼ 1) in which the magnetic Reynolds number of turbulent eddies is small. For Φ ≳ 105, there is a turbulent dynamo. Probable planetary examples of these three dynamo states are Mercury (Φ ∼ 102‐103), Earth (Φ ∼ 104) and Jupiter (Φ ∼ 1011), respectively.
Theory of magnetic stars
Authors: Mestel L. 
Published: July 2007

AbstractThe principal observational facts on the early‐type magnetic stars are summarized, and interpreted in terms of the oblique rotator model. In the theoretical discussion of the interaction between a large‐scale magnetic field and the star's thermal, gravitational and rotation fields, emphasis is laid on effects that are relevant to both fossil and dynamo theories of the origin of the magnetic field.
Photometry and spectrophotometry of magnetic stars
Authors: Stępień K. 
Published: July 2007

AbstractA review of selected photometric and spectrophotometric properties of magnetic stars is given. It is shown that unreddened B–V of magnetic stars around B9 type can be transformed to log Te using the calibration for normal stars and no systematic errors are introduced. Mechanisms of light variability are discussed. It is concluded that different mechanisms must be operating in different stars.Recently obtained photometric observations of short‐period variability by KURTZ and Hβ variability by MADEJ et al. are discussed. An information about internal structure and the atmospheric structure of these stars can be derived from these observations.