bluuebunny/crossref_metadata_2025_split huggingface dataset:
The redshift distribution law of quasars revisited
Authors: Depaquit D. , Pecker J.–C. , Vigier J.–P. 
Published: July 2007

AbstractCan observational selection effects, tied with the existence of strong lines, explain the observed log (1 + z) periodicity of the quasar's histogram, as sometimes claimed? A first approach shows that one must distinguish radio from optical quasars. In the former case spectroscopic selection due to strong lines is investigated from the study of homogeneous samples. Then, the role played by pairs of strong lines in the redshift's determination is evaluated and it shows that teh spectroscopic selection cannot explain the observed periodicity of the radio quasar's histogram. The study of the complete sample confirms this conslusion.
Strong gravity effects in the temperature profile of accretion disks
Authors: Paul H. G. 
Published: July 2007

AbstractThe temperature profile of accretion disks moving axially symmetric in the static, spherically symmetric field of a compact, massive object is calculated without specifiing the gravitational theory. Using the covariantly written viscous, fluiddynamical equations of motion, the α viscosity law and free‐free radiation of a cooling region is obtained under very general assumptions about the behaviour of the external gravitational field. The used gravitational theory is reflected by inner boundary processes taking place in the region of strong gravity; the cooling region could give a significant „bremsstrahlung”︁ correction to the ”︁cool'' part of the spectrum radiated away from the outer, weak gravity region of the disk.
Beobachtungen der Geminiden und Quadrantiden
Authors: Rendtel J. , Rendtel I. , Otto F. , Koschack R. 
Published: July 2007

AbstractGeminiden und Quadrantiden werden wahrscheinlich erst seit etwa 100 Jahren beobachtet. Infolge von Bahnstörungen unterliegen sie schnellen Veränderungen. Eine Verformung des Geminiden‐Ratenprofiles läßt sich jedoch nicht finden.Beobachtungen der Geminiden und Quadrantiden durch den Arbeitskreis Meteore werden mit den Perseiden verglichen. Bei allen drei Strömen wird zum Maximum der Gesamtaktivität auch eine Zunahme der Zahl heller Meteore festgestellt. Zum gleichen Zeitpunkt sinkt der Populationsindex r für Perseiden und Quadrantiden, während der der Geminiden steigt. Daraus wird eine Abschätzung der Zunahme der Teilchenzahl zu schwächeren Helligkeitsklassen gewonnen.
Solutions of the linearized Bach‐Einstein equation in the static spherically symmetric case
Authors: Schmidt H.‐J. 
Published: July 2007

AbstractThe Bach‐Einstein equation linearized around Minkowski space‐time is completely solved. The set of solutions depends on three parameters; a two‐parameter subset of it becomes asymptotically flat. In that region the gravitational potential is of the type φ = ‐m/r + ε exp (‐r/l) m and ε being small parameters.Because of the different asymptotic behaviour of both terms, it became necessary to linearize also around the Schwarzschild solution φ = ‐m/r. The linearized equation resulting in this case is discussed using qualitative methods. The result is that for m ≤ 2l the asymptotic behaviour is φ = ‐m/r + εr−m/l exp (‐r/l) u, and for m ≧ 2l φ = ‐m/r + εr−2 exp (‐r/l) u, where u is some bounded function; m is arbitray and ε again small. Further, the relation between the solution of the linearized and the full equation is discussed.
Spherical simulations of large‐scale structure of the Universe
Authors: Mücket J. P. 
Published: July 2007

AbstractWe consider a spherical‐smmetric perturbation in an initially homogeneous dust filled universe within the frame‐work of the Bondi‐Tolman solution. The decoupling of the perturbed region from the background evolution naturally leads to shell‐crossing in a certain outer environment, which describes energy relaxation. In the approximation of Newtonian gravity it can be analytically determined the behaviour of the outgoing front shell and different parameters of the shell‐crossing region. On the basis of the obtained results we give a possible explanation for the “large voids” in the observed galaxy distribution.
Stability of amorphous circumstellar silicate grains
Authors: Henning Th. , Svatoš J. 
Published: July 2007

AbstractBerechnungen innerhalb der klassischen Nukleationstheorie zeigen, daß Mg2SiO4‐Staubteilchen mit Radien von etwa 0,1 μm, die sich mit hoher Wahrscheinlichkeit im zirkumstellaren Raum um Sterne späten Spektraltyps bilden, bei etwa 750 K auskondensieren müssen, um amorph zu bleiben. Beträgt die Kondensationstemperatur 1000 K, müssen die neugebildeten Teilchen kleiner als 0,01 μm sein, wenn sie während der Abkühlung amorph bleiben sollchen. MgSiO3‐Teilchen mit Radien kleiner als 1 μm sind bei Tcond ≤ 1000 K gegenüber der Kristallisation stabil.
Verwendbarkeit des Prismas auf der Korrektionsplatte des Tautenburger Schmidt‐Spiegels bei Positionsbestimmungen
Authors: Hirte S. , Schilbach E. 
Published: July 2007

AbstractTo overcome a possible magnitude equation a weakly refracting prism fitted on the correcting plate of the Tautenburg Schmidt telescope was used, forming a secondary image of every object 3.8 mag weaker than the primary one. Because the distances between these two images are not constant, a polynomial was searched which could reflect these variation in dependence on the magnitude of a star and its position on the plate. For each of the 11 plates tested we have got another polynomial, therefore this way to tide over large magnitude differences is unefficient for astrometric investigations.
Bestimmung der Helligkeitsgleichung auf Tautenburger Schmidt‐Platten
Authors: Schilbach E. 
Published: July 2007

AbstractAus Messungen von 3 Plattenpaaren, die mit dem Tautenburger Schmidt‐Teleskop im B‐System aufgenommen wurden, wurden die Koeffizienten dx und dy des Reduktionsmodells in Abhängigkeit von der Sternhelligkeit abgeleitet. Die Analyse der Ergebnisse zeigt, daß bei der Bestimmung von Eigenbewegungen von Sternen mit Helligkeitsunterschieden von mehr als 6‐‐7 mag in bezug auf die Refrenzpunkte systematische Fehler auftreten können, die größer als die Meßfehler sind. Diese Fehler entstehen auf Grund der Helligkeitsgleichung und variieren von Plattenpaar zu Plattenpaar.
Investigations of spherical kinematic mean‐field dynamo models
Authors: Rädler K.‐H. 
Published: July 2007

AbstractThe paper supplements an earlier one on the mean‐field approach to spherical kinematic dynamo models (Rädler1980a) by results of numerical investigations.A number of dynamo models working on the basis of the α2‐mechanism are considered. Cases of pure α2‐mechanism are studied, which includes only the simplest form of α‐effect and no other induction effect, as well as cases with several additional effects due to fluctuating or mean motions. By the pure α2‐mechanism axisymmetric and non‐axisymmetric fields, can be excited and maintained with nearly equal ease. Part of the additional induction effects, however, clearly favour axisymmetric fields, and others non‐axisymmetric fields. The non‐axisymmetric fields are waves which travel in azimuthal direction, eastward or westward, depending on the models.For special dynamo models the transition from α2to αω‐mechanism and properties of the latter are investigated. The results support the presumption that the αω‐mechanism is able to maintain only axisymmetric but never non‐axisymmetric fields. Conditions for the occurrence of non‐oscillatory or oscillatory fields are discussed, and again the influence of additional induction effects is studied.There are further presented a model with βω‐mechanism maintaining an axisymmetric non‐oscillatory field, and models with two kinds of δω‐mechanisms allowing axisymmetric non‐oscillatory and oscillatory fields.Some ideas concerning dynamo models for the Earth, the Sun and magnetic stars are discussed.It seems possible to construct dynamo models for the Earth, on the basis of the α2‐mechanism which explain not only the presence of a magnetic field with a strong dipole part but also the inclination of the dipole axis against the axis of rotation, the occurrence of higher multipoles and the westward drift of the non‐axisymmetric parts. Models with αω, βω or δω‐mechanism, which have to be considered in the case of a strong differential rotation inside the core, provide an explanation at first only of the axisymmetric parts of the field, and the non‐axisymmetric parts have then to be interpreted, for example, as MAC‐waves.As far as dynamo models for the Sun are concerned, in addition to the possibility of an αω‐mechanism also that of a βω or δω‐mechanism is discussed, which, however, does not look not very promising. In the models developed so far, which work with the αω‐mechanism, only a few of the induction effects of fluctuating motions have been included; it seems necessary to investigate also influences of other effects. The sectorial structure of the solar magnetic field can hardly be understood in terms of the traditional mean‐field concept.The magnetic stars possess fields which strongly deviate from symmetry with respect to the axis of rotation. The occurrence of such fields seems understandable only if there is no noticeable differential rotation. They can be maintained by an α2‐mechanism but hardly by αω, βω or δω‐mechanisms.
Mass loss from very young massive stars (Mitteilungen der Universitäts‐Sternwarte zu Jena Nr. 172)
Authors: Henning Th. 
Published: July 2007

AbstractA very important property of very young and massive stars (BN objects) is their intensive mass loss. We describe the main methods to derive the mass loss rates. Available observations are used to characterize the ionized stellar winds and the CO flows. The results are confronted with theories describing the anisotropic mass loss.
Empirical properties of nearby groups of galaxies
Authors: Vennik J. 
Published: July 2007

AbstractVirial parameters of individual groups and of synthesized groups of galaxies are determined on the basis of a new list of nearby groups of galaxies (V0 < 3200 km/s). Small values of the crossing time ({TcrosH0} ≈ 0.2) allow us to consider the groups of being gravitationally bound systems. The cumulative mass of the synthesized groups increases up to ∼1 Mpc from the center, giving the total mass‐to‐luminosity ratio f = 97 f⊙ (H0 = 75 km/s/Mpc). Statistically significant correlations between virial parameters (σv, RVT, f) are found: f ∝ σv1.5 and f ∝ RVT0.7; σv and RVT are uncorrelated.
Zur Abschätzung der Zyklenlänge bei langzyklischen U‐Geminorum‐Sternen
Authors: Wenzel W. , Richter G. A. 
Published: July 2007

AbstractVerschiedene Methoden zur Ermittlung mittlerer Zyklenlängen werden beschrieben, und der Einflß von Beobachtungslücken wird diskutiert. Am Beispiel von SW UMa werden statistische Aussagen und direktere Bestimmungen verglichen; die übereinstimmung ist nicht schlecht.
Vacuum polarization and scalar field effects in the early Universe
Authors: Gottlöber S. , Müller V. 
Published: July 2007

AbstractHomogeneous isotropic cosmological models driven at early times by a coherent scalar field and the vacuum polarization are considered. Both effects can lead to the existence of a finite minimal value of the scale factor and an inflationary stage of expansion. The early as well as the late time behaviour of the cosmological evolution depends critically on the ratio of the contribution from the vacuum polarization and the scalar field.
Extraterrestrial possibilities to measure cosmic antimatter
Authors: Halm I. 
Published: July 2007

AbstractThe question of the existence of primary cosmic antimatter (PCA) is of fundamental interest for cosmogony and cosmology. The relcvance of PCA to processes in the very early Universe (corresponding to an energy of 1015 GeV) is shown. A satellite experiment consisting of a magnet spectrometer is proposed, which identifies antiprotons (p̄), antihelium nuclei (α), and positrons (e+) in the kinetic energy range from 100 MeV to 10 GeV to get statistically significant p̄‐ and e+‐spectra and possibily some α events in a year of exposure.
Generalized harmonic gauge conditions in General Relativity as field equations for lapse and shift
Authors: Hirschmann T. , Schimming R. 
Published: July 2007

AbstractThe prescription of the harmonicity quantities to a spacetime metric may be read, in the ADM decomposition, as a system of evolution equations. Cauchy's initial value problem for this system is investigated here. Additionally, the differential‐geometric substance behind the ADM scheme is analysed.
Oscillatory α2‐dynamo: numerical investigation
Authors: Baryshnikova Y. , Shukurov A. 
Published: July 2007

AbstractLinear and nonlinear equations describing the generation of a large‐scale magnetic field (α2‐dynamo) in a thin disc of turbulent conducting fluid are derived and discussed. The numerical procedure is based on a finite‐difference implicit scheme for the corresponding nonlinear Cauchy problem with boundary conditions. In addition, the QR‐algorithm for the linear eigenvalue problem is realized.It is demonstrated that the α2‐dynamo is able to generate oscillatory magnetic fields. The periods of oscillation are typically of the order of or less than the diffusion time. These oscillations are suggested to be due to boundary effects. Dependence of the solutions on the generation efficiency and on the distribution of the mean helicity across the disc are discussed in detail.The period of oscillations only slightly depends on the specific form of distribution of the mean helicity across the disc and is determined mainly by the magnitude of the helicity and by the position of the helicity extremum: the nearer this point to the boundary, the greater the oscillation frequency. Nonlinear effects suppress oscillations when the mean helicity attains its maximum at a depth not more than a quarter of the disc thickness, and promote them otherweise.The one‐dimensional system of nonlinear α2‐dynamo equations is reduced to a single nonlinear equation of the Schrödinger type.
On the oscillatory behaviour of kinematic mean‐field dynamos
Authors: Rädler K.‐H. , Bräuer H.‐J. 
Published: July 2007

AbstractThe paper considers the question after the circumstances in which kinematic mean‐field dynamos can have oscillatory magnetic field modes. The conducting fluid body is allowed to be of almost arbitrary shape; its surroundings are vacuum. A general relation for the frequency of oscillation is derived. This relation is discussed more closely for models with pure α2‐mechanism. Proof is given that no oscillations can occur for constant α. The investigations published so far on spherical models with pure α2‐mechanism call up the question whether there is a chance for axisymmetric modes to be oscillatory. For both spherical models and disk models the possibility of oscillatory axisymmetric modes is demonstrated by examples.
Combined UBV and uvby photometry of open clusters. I. NGC 1502
Authors: Reimann H.‐G. , Pfau W. 
Published: July 2007

AbstractFor at all 24 stars in the field of the heavity reddened open cluster NGC 1502 we obtained UBV and uvby photometry. 19 of these stars we classified definitely as members. From the photometric results we derived 1·1 × 107 years as the cluster age, 960 pc as its distance, and <E(B—V)> = 0·78 mag as mean reddening of the cluster. From the reddening of the foreground stars we evaluated that the intracluster reddening has to be smaller than 0·2 mag. The value of the colour excess ratio E(b—y)/E(B—V) = 0·770 leads us to the conclusion that in the spectra of the cluster stars a very broadband structure (VBS) with a central depth of about 0·04 mag is present.
The influence of the electromagnetic core‐mantle coupling torques on earth's rotation
Authors: Greiner‐Mai H. 
Published: July 2007

AbstractThe electromagnetic core‐mantle coupling is one of the most likely hypotheses to explain the connections between both, the decade fluctuations of the Earth rotation and such of the magnetic field of the Earth. Within this paper, the axial and equatorial electromagnetic torques are computed at time intervals of two years from 1903.5 to 1975.5. They are compared with mechanical torques necessary for the excitation of the decade variations of the rotation of the Earth. The comparison is made with regard to the magnitude of the torques, to their time behaviour and to the periods within the time variations of both types of the torques. The computed electromagnetic torques are comparable with that necessary to excite the variations of the rotation of the Earth. But they are two or three orders less than that necessary to excite the decade variations of the polar motion. Some comparable periods were found within the spectra of the electromagnetic and the mechanical torques. This speaks in favour of the core‐mantle coupling. But there are differences between both spectra too hinting at other processes which we cannot describe by a simple model of the core‐mantle coupling.
Photoelectric photometry of comets in the system of standard IHW filters and the special case of comet P/Halley
Authors: Stecklum B. , Pfau W. , Hesse M. 
Published: July 2007

AbstractMagnitudes of comets P/Giacobini‐Zinner (1984e), P/Halley (1982i), P/Hartley‐Good (1985 1), and Thiele (1985 m) in the bandpasses of the standard IHW comet filters are presented. For comet P/Halley production rates for CN, C3, C2, and solids were derived. For the gaseous components these show a strong dependence on heliocentric distance. The dependence is less steep for the solids which may be due to relatively pronounced backscattering properties in case of comet P/Halley. During one night (1985 Dec. 22/23) intensity profiles along three sections through the coma of comet P/Halley were measured. Compared with theoretical profiles they show a global anisotropy of the coma and possibly local structure.
Mesures micrometriques d'etoiles doubles visuelles (3me liste)
Authors: Scardia M. 
Published: July 2007

AbstractThe results of 521 micrometric measurements of 140 binary stars are given. The measurements have been made at Brera‐Merate and Collurania (Teramo) observatories during the period February 1984‐December 1985 with two refractors of 23 cm and 40 cm, respectively.
Binary star statistics: the mass ratio distribution for very wide systems
Authors: Trimble V. 
Published: July 2007

AbstractThe distribution of mass ratios for a sample of common proper motion (CPM) binaries is determined and compared with that of 798 visual binaries (VB's) studied earlier, in hopes of answering the question: Can the member stars of these systems have been drawn at random from the normal initial mass function for single stars? The observed distributions peak strongly toward q = 1·0 for both kinds of systems, but less strongly for the CPM's than for the VB's. Due allowance having been made for assorted observational selection effects, it seems quite probable that the CPM's represent the observed part of a population drawn at random from the normal IMF, while the VB's are much more difficult to interpret that way and could, perhaps, result from a formation mechanism that somewhat favors systems with roughly equal components.
Isotropization by scalar field driven inflation and the cosmological quantum boundary
Authors: Lukash V. N. , Schmidt H.‐J. 
Published: July 2007

AbstractWe derive the Wheeler‐de Witt equation for the scalar field of mass m > 0 in a Bianchi‐type I universe. We argue that classical trajectories become possible at h2 ⩽ αtp‐2, h being the mean Hubble value and tp the Planck time. We feel justified to set the numerical constant α ≈︁ 1. We discuss this condition in geometrically invariant quantities and compare it with ⩽tp‐4. The proposed quantum boundary of classical trajectories represents a 3‐dimensional sphere in the 4‐space of the dynamical system. Equipartition of the initial energy over field (m < mp) and shear variables at the quantum boundary will cause inflation with a probability p of the order p = 1 ‐ m/mp thus, p = 1 ‐ 10‐4 for m taken from GUT. In the course of the inflationary stage the initially arbitrarily large shear‐anisotropy exponentially decays.
MV Lyrae: Entering the period gap?
Authors: Andronov I. L. , Fuhrmann B. , Wenzel W. 
Published: July 2007

AbstractMV Lyrae was studied on about 2000 photographic plates of the Moscow, Odessa and Sonneberg collections. A brief review of these results in comparison with literature data is given. The object might be a unique system, entering the period gap. Outbursts are observed in the minimum state, which may be possibly explained by the trigger mechanism for the radiation‐induced mass outflow from the secondary, underfilling its Roche lobe.
Model calculations of the degree of polarization of solar S‐coniponent emission at millimetre waves
Authors: KrÜger A. , Hildebrandt J. 
Published: July 2007

AbstractModel calculations of the S‐component accounting for the emission from uniform sunspot and inhomogeneous plage regions are applied to a prediction of the spectral distribution of the degree of circular polarization at millimetre waves. The results are compared with observations adopted from the literature and a sufficient agreement between model computation and measurement can be slated. However, observations with higher spatial resolution than presently available are needed in order to check the predicted fine structures and to verify details of the applied model.
Beobachtungen Kleiner Planeten. VII
Authors: BÖrngen F. 
Published: July 2007

AbstractEs wird eine Übersicht über die im Jahr 1986 auf Tautenburger Schmidtplatten gefundenen Kleinen Planeten gegeben. Es wurden 129 Objekte entdeckt und für sie 312 Positionen gerechnet. Es handelt sich um 29 numenerte Objekte und 100 Planetoiden mit provisorischer Bezeichnung, von denen sechs keine neue Bezeichnung haben. Für fünf im Berichtszeitraum numerierte Planeten haben Tautenburger Beobachtungen einen Beitrag geleistet. Darunter ist der in Tautenburg entdeckte Planetoid 1981 VW1, der die Nummer (3499) und den Namen Hoppe erhielt.
Investigation of clusters of galaxies II. A two colour photometry for the cluster Abell 1795
Authors: Baier F. W. , Ziener R. 
Published: July 2007

AbstractA photographic photometry in B and V was performed for the cD cluster of galaxies A 1795 which is located near the north galactic pole. Our catalogue contains 721 galaxies in a field of 1.6 ° around the cluster center.
Analysis of the light curve of the magnetic CP star HD 56022
Authors: Hempelmann A. , Sch;Öneich W. 
Published: July 2007

AbstractAn examination of the published observational data concerning the light curves of magnetic CP stars has shown that only one star — HD 56022 — shows a light curve with a very long phase interval of light constancy. Only for this type of variability it is imaginable that the equatorial symmetry of the surface brightness distribution could be excluded. However, the analysis of the light curve of HD 56022 in the colour u of the Strömgren system has indicated that the possibly equatorial position of the small bright spot is not in contradiction to this observed curve.From the analysis in u the maximum amplitude of a light curve at another wavelength, where the curve is in counterphase to the light curve in u, can be predicted. The amplitude of such a light curve must be much smaller than 0.1 mag. From unpublished observations of HD 56022 by the satellites TD‐1 A and ANS we have determined the amplitude at $LD = 155 nm, where the light curve is in counterphase to that in u, to be 0.2 mag.The consequences from the contradiction between the model and the observations in UV are discussed.