bluuebunny/crossref_metadata_2025_split huggingface dataset:
New and misclassified Planetary Nebulae
Authors: Kohoutek L. 
Published: July 2007

AbstractAltogether 81 objects discovered between 1987 and 1990 have been accepted by the author as new PN (Table 1). In the Appendix to Table 1 we give the list of possible pre‐PN. In the list of misclassified PN (Table 2) 86 objects were included. A statistics of the new and misclassified PN since CGPN is presented.
On the “rotational angular momentum” of the oceans and the corresponding polar motion
Authors: Brosche P. , Wünsch J. 
Published: July 2007

AbstractPeriodic polar motions caused by ocean tides are predicted. In the Liouville equations for rotational motion the complete excitation functions for the ocean tides have to be used. This does not depend on the fact that hydrodynamical ocean tide models do not consider the centrifugal acceleration. The observable polar motion of the Celestial Ephemeris Pole CEP (more exactly: the terrestrial location of the CEP) is tabulated for the ten ocean tidesM2,S2,N2,K1,O1,P1,M f, M f′, M m, Ssa. Typical amplitudes for the largest ocean tides are 0.4 milliarcseconds. This is within the reach of geodetic VLBI and SLR observations.
Multi‐density models of the Broad Line Region in Active Galactic Nuclei: a comparative study with single‐cloud models
Authors: Radovich M. , Rafanelli P. 
Published: July 2007

AbstractNearly ten years ago Kwan and Krolik (1979, 1981) published the firstsuccessful photoionization model of the Broad Line Region of Active Galactic Nuclei, the so‐called ‘Standard Model’. Since then several efforts have been made to obtain better results using more sophisticated models. Anopen issue is that photoionization models are generally computed startingfrom the assumption that the emission line spectrum is produced by a single‐slab cloud with a ‘standard’ hydrogen density nH = 109.5 cm‐3, but it seems more likely that a range of densities is present in the Broad Line Region.Purpose of this paper is to review the results given by single‐cloud models using the most recent photoionization code, Cloudy 84, and to investigate if the addition of one or more components with different densities does affect the line ratios. To this aim we compute the emission line ratios produced by photoionized single‐slab clouds for a wide range of hydrogen densities (nH = 109.5−1013 cm−3), ionization parameters (U = 10−4− 10−0.5) and column densities (NH = 1023−1025 cm−2). Two or more populations of clouds are then combined and the resulting emission line spectrum is compared with a sample of mean observed line ratios. We find that the addition to the standard component of clouds having different densities and located at different positions from the central source introduces many changes in the line ratios, and that these changes are in the direction of a better agreement with the observed emission line ratios.
Toward a more consistent evolution model for the local galactic disk
Authors: Meusinger H. 
Published: July 2007

AbstractInfall models for the evolution of the local galactic disk were studied and confronted with a large number of observational constraints from the solar vicinity, inclusive of the white dwarf luminosity function. The models are characterized as follows: 1. The key‐functions (SFR, IMF, gas infall rate) are not prescribed by simple laws, but are directly derived from observational constraints. 2. A scatter in the metallicity at fixed age is considered which partly reflects inhomogeous chemical evolution. 3. Special attention is drawn to the internal consistency of the models. 4. In addition to infall of low‐metallicity gas, metal‐enriched outflows are allowed. The “best” model is characterized by a disk age of ≈︁ 12 Gyr, a SFR which is decreasing over the first half and is nearly constant over the second half of the disk evolution, and by a similar temporal run of the gas infall rate. Moderate metal‐enriched outflow can not be excluded.
Dynamo theory and liquid metal MHD experiments
Authors: Lielausis O. 
Published: July 2007

AbstractHigh values of magnetic Reynolds numberRmare characteristic not only to astrophysics, but also to other interesting objects, including liquid metal (LM) flows. Since sixties LM experiments have been performed illustrating important predictions of the dynamo theory, for example, about the existence and features of the α effect. Consideration of so called “laminar” dynamos provides a theoretical base for direct experimental realization and examination of the dynamo process. First step results, gathered at subcritical conditions, confirm the statement that self‐excitation in LM experiments can be achieved practically today.In such devices as LM (sodium) cooled fast breedersRmcan reach values up to 50 and specific MHD phenomena have been observed in operating fast reactors. Cautions against crisis like processes have been expressed. It is important for the dynamo theory to understand what kind of perturbed motion is able to coexist with the generated magnetic field. Fundamentally new ideas here are issuing from the theory of 2D MHD turbulence. LM MHD served for the first direct proves, confirming, that the predicted surprising features of 2D turbulence can be observed in reality. It is worth incorporating these already not new ideas in the dynamo theory. In such a way a field for new solutions could be established.
Large‐scale streaming of flat galaxies
Authors: Karachentsev I. D. , Karachentseva V. E. , Kudrya Yu. N. , Parnovsky S. L. 
Published: July 2007

AbstractWe consider a sample of thin edge‐on galaxies from new a Flat Galaxy Catalogue, FGC (Karachentsev et al. 1993) covering the whole sky. The galaxies have been selected into the Catalogue by their apparent axis ratio a/b > 7 and angular diameter a ≥ 0.6 arcmin. Among 4455 such galaxies 893 have estimates both radial velocity and inner motion amplitude, however most part of them (542) are concetrated in the Arecibo zone. This sample is characterized by the medians: uh = +5300 Km s−1, W50 = 285 km s−1 and Ty = Scd.To determine distances and peculiar velocities of the flat galaxies we use different modifications of the Tully‐Fisher relation between linear diameter and HI linewidth taking into account also their surface brightness. A typical scatter of galaxy distance estimates by this method corresponds to dex (0.09).In a dipole approach we calculated the terms of bulk motion of the galaxies. Relative to the CMB frame the population of FGC galaxies is moving to apex l = 319° ± 10°, b = +28° ± 11° with velocity 260 ± 40 km s−1. Here the formal 1σ errors correspond to a scattering of estimates carried out with different kinds of the TF relation (blue or red diameters, two‐ or three‐parametric regressions).A consecutive removing of nearby galaxies by a condition of V < Vmin leads to a rise of the mean bulk velocity and to a drift of the apex direction: Vbulk = 400 ± 70km s−1, l = 304° ± 6°, b = +23° ± 12° for Vmin = 3500km s−1 and Vbulk = 450 ± 40km s−1, l = 301° ± 7°, b = +23° ± 4° for Vmin = 8500km s−1, what remains not far from the Shapley concentration (l = 311°, b = +30°) of rich clusters.
Observable Physical Effects during New Solar Active Regions Formations
Authors: Bumba V. 
Published: July 2007

AbstractIn the present paper we are trying to demonstrate the importance of detailed observations for the theory of solar local magnetic field generation. Mutual relations of solar background magnetic fields and new active region formations are described. The influence of various factors, dependent as independent on the cycle of solar activity and the dynamics of background fields is considered. In the main chapter all forces and effects whose action can be derived from systematic observations of magnetic field distribution and high resolution photospheric photographs of all stages of active regions development are discussed. Before all the influence of convection, of the reaction on field lines penetration, of various magnetic forces, of differential rotation and of hydrodynamical forces is demonstrated. The importance of a „center of magnetic activity”︁ — a magnetic subsystem orthogonal to the main system of active region's field as a source of new magnetic flux is underlined. The necessity of a new approach to the problem of local magnetic field generation is stated.
Self‐Modulation and Envelope Solitons of Spiral Density Waves
Authors: Meinel R. 
Published: July 2007

AbstractA nonlinear evolution equation describing the modulation of the LIN‐SHU density waves in the tight winding approximation is discussed. A fluid dynamical model with a polytropic relationship between the pressure and the density is used. The equilibrium state is assumed to be homogeneous in the considered radial range. As in the case of plane density waves (IKEUCHI and NAKAMURA 1976) the modulation of spiral density waves is governed by the nonlinear SCHRödinger equation. For large wave numbers the process of self‐modulation generates envelope solitons and could explain the permanent renewal of the spiral design of galaxies.
HD 134 518: A Main‐Sequence Detached or a Semi‐detached Eclipsing Binary?
Authors: Russo G. 
Published: July 2007

AbstractWe have analyzed PRZYBYLSKY's (1981) photometric observations of HD 134518, an eclipsing binary with a period of 1.15 days and a β Lyrae type light curve. Performing a grid of solutions with different assumed values of the mass ratio by means of the WILSON‐DEVINNEY method we have determined the photometric elements of this variable, which shows an extremely low mass ratio (q = mc/mh = 0.06) and appears as semi‐detached system.The discrepancies between the WILSON‐DEVINNEY solution and the WOOD solution (GIURICIN et al. 1982) are pointed out. Die photometrischen Beobachtungen PRZYBYLSKYS (1981) von HD 134 518, einem Bedeckungsveränderlichen mit P = 1d.15 und einer β‐Lyrae‐artigen Lichtkurve, wurden analysiert. Mittels der WILSON‐DEVINNEY‐Methode wurden für verschiedene Masseverhältnisse die photometrischen Elemente des Veränderlichen bestimmt, der ein extrem niedriges Massenverhältnis (q = mc/mh = 0.06) besitzt und halbgetrennt zu sein scheint.
Revised photometric elements of the eclipsing binary DS and
Authors: Giuricin G. , Mardirossian F. , Mezzetti M. 
Published: July 2007

AbstractWith the aid of WOOD's (1972) model we have reanalyzed MAGALASHVILI and KUMISHVILI's (1978) UBV light curves of the eclipsing binary DS And.Our photometric elements considerably differ from the previous ones and show that DS And can be related to the contact systems.
Problems of Bias Free Determination of Cluster Luminosity Functions
Authors: Balázs L. G. , Paparó M. 
Published: July 2007

AbstractDetermination of cluster luminosity functions require separation of cluster members from the stellar background. Methods of selecting true members from projected field stars in the same area usually suffer from selection effects. Selection effect arising from utilizing membership probabilities to discrminate between field and cluster stars are discussed. A small excess of interstellar absorption in a cluster area could cause serious bias if one utilizes statistical subtraction. Such bias in statistical filtering is studied on a numerical example. A filtering procedure is described to prove the presence of cluster in the given sample. This procedure yields, as byproduct, the cluster radius as well. Evidence is presented that the luminosity functions of SANDAGE(1957) and TAFF(1974) may suffer from bias.
The Central Regions of M82 – Scattered Light and Extinction
Authors: Notni P. , Bronkalla W. 
Published: July 2007

AbstractPhotographic photometric measurements of 2 arcsec resolution of the central regions of M82 are presented in the three colours U, B, V. The observed light is decomposed into two parts: stellar light and light from the central source scattered by dust. The variation of the reddening of both components is derived.The dust distribution pattern is different near the spatial centre of M82 and farther out. The equator of the dust complex obscuring the central source is inclined to the overall symmetry plane of M82. The outer dust clouds responsible for the obscuration of the visible stellar light are probably arranged in a spiral‐like fashion; the “plane” containing these clouds is strongly warped and distrubed.The light of the bright knots A and C consists to a considerable part of scattered light from the central source nearly behind them. Hα light and scattered continuum light is strongly correlated in M82, pointing to an ionisation of the gas by the source of this continuum in addition to the presence of scattered Hα.
Simple nonlinear recursions and the mean‐field concept
Authors: Krause F. 
Published: July 2007

AbstractSome questions concerning the formation of mean‐field theories are analyzed by a consideration of simple nonlinear recursions. The results suggest that a general closure scheme does not exist, rather there is a great variety of closures, each of the valid in only a certain interval of the characteristic parameter.Furthermore, questions connected with the appearance of random behaviour in these deterministic systems and the modelling of random reversals are discussed.
On spherical mean‐field dynamo models with coupling between axisymmetric and non‐axisymmetric field modes
Authors: Rädler K.‐H. 
Published: July 2007

AbstractThe mean‐field dynamo models developed on the basis of mean‐field magnetohydrodynamics reflect some essential features of the magnetic phenomena accompanying the Earth, the Sun and other cosmical bodies. The magnetic fields of those objects may be understood as superpositions of modes which are obtained if the fields are subjected to Fourier decomposition with respect to the longitudinal coordinate and each Fourier component is split into two parts which are either symmetric or antisymmetric with respect to the equatorial plane. The mean‐field models investigated so far provide no satisfactory explanation for the distinct multimodal structure of the observed fields. Within the framework of the traditional mean‐field concept, and with reasonable assumptions, possibilities of couplings of modes occur only due the back‐reaction of the magnetic field on the motions. These possibilities are discussed, and results of relevant numerical experiments are presented. It is open to question whether couplings of this kind are able to explain the coexistence of modes of the observed fields. A modified mean‐field concept is proposed which implies couplings of modes even without any back‐reaction. Contrary to the couplings due to back‐reaction these couplings imply that, in general, axisymmetric modes are accompanied by non‐axisymmetric ones.
Investigation of the initial mass spectrum of open star clusters
Authors: Stecklum B. 
Published: July 2007

AbstractThe mass spectra of 228 open star clusters were derived by comparison of colour‐magnitude diagrams with evolutionary tracks. The application to binary stars showed the reliability of the mass determination. The derived mass spectra were fitted by power laws as well as exponential laws. It could be shown that both approximate the mass spectra of open star clusters on the same average significance level. The present investigation revealed a correlation of the slope of the mass spectra with the cluster age, whereas a detected correlation of the slope with galactocentric distance is slight. The results suggest that the slope of the mass spectrum increases with increasing cluster age and galactocentric distance. These findings are discussed with respect to their reasons and previous results concerning open clusters and field stars.
Three‐dimensional model for generation of the mean solar magnetic field
Authors: Ivanova T. S. , Ruzmaikin A. A. 
Published: July 2007

AbstractA three‐dimensional (non‐axisymmetric) model for the solar mean magnetic field generation is studied. The sources of generation are the differential rotation and mean helicity in the convective shell. The system is described by two equations of the first order in time and the fourth order in space coordinates. The solution is sought for in the form of expansion over the spherical function Ynm. The modes of different m are separated. A finite‐difference scheme similar to the Peaceman‐Rachford scheme is constructed so to find coefficients of the expansion depending on the time and radial coordinates.It is shown that a mode with a smaller azimuthal number m is primarily excited. The axisymmetric mode m = o describes the 22 year solar cycle oscillations. The modes of m o have no such periodicity, the oscillate with a period of rotation of the low boundary of the solar convective shell, The solutions which are symmetric relative to the equator plane are excited more easily compared with the antisymmetrical ones.The results obtained are confronted to the observational picture of the non‐axisymmetric large‐scale solar magnetic fields.
Der Lichtwechsel des Ap‐Sterns HD 221568 (Osawas Stern) in zehn Spektralbereichen
Authors: Schöneich W. , Želwanowa E. I. 
Published: July 2007

AbstractDer schon zu den langperiodischen Ap‐Sternen gehörende Stern HD 221568 wurde im Zeitraum 1976 bis 1981 in zehn Spektralbereichen (3450 Å – 7650 Å) beobachtet. Der Stern zeigt typische Rotationslichtkurven mit einer Doppelwelle. Die Eigenschaften der Amplituden‐Wellenlängen‐Beziehung haben Ähnlichkeit mit der einiger kühler kurzperiodischer Ap‐Sterne. Die berechnete Variation des Strahlungsstroms im Sichtbaren deutet auf eine im ultravioletten zu erwartende Variabilität mit großer Amplitude hin.
Die Beobachtungen des Halley'schen Kometen im Jahre 1836 von Johannes Lamont in München
Authors: Landgraf W. 
Published: July 2007

AbstractEine der besten Beobachtungsreihen des Halley'schen Kometen bei seiner Erscheinung von 1835/6, die Beobachtungen von J. LAMONT in München‐Bogenhausen, die den Zeitraum der verwendbaren Beobachtungen um über ein halbes Jahr ausdehnt, liegt bisher noch nicht in reduzierter Form vor. Wegen diverser zu berichtigender Fehler in den vom Beobachter publizierten Meßwerten wurden die Reduktionsrechnungen detailliert wiedergegeben, um die Beobachtungen den Bahnrechnungen zugänglich zu machen.
Evidence of a star formation burst in a spheroidal dwarf galaxy
Authors: Schmidt R. , Richter G. M. , Karachentseva V. E. 
Published: July 2007

AbstractWe present here the luminosity profile and the colour distribution of the irregular dwarf galaxy UGC 5423 = M81 dwB. Using digital surface photometry we show that UGC 5423 is a burst of young stars in the central body of a larger spheroidal dwarf galaxy.
The relative luminosities of the disk and the invisible of M82 a rediscussion of the polarization pattern
Authors: Notni P. 
Published: July 2007

AbstractThe origin of the noncircular pattern of the polarization vectors in the halo of scattered light around M82 is discussed anew. This pattern had been interpreted by SOLINGER and MARKERT (1975) to indicate a high contribution of the disk to the illumination of the halo, whereas the blue colour of the halo demands a significant contribution from a very blue illuminating source, the nucleus. The discussion of SOLINGER and MARKERT has been modified in two respects: 1. an extinction in the disk M82, distributed similar to the stars, is assumed; this strengthens the disk's ability to turn the polarization vectors parallel to itself, and 2. an original polarization of the nuclear light parallel to the galaxy's plane is assumed; this also causes a corresponding turning of the polarization vectors.The new estimate of the nuclear luminosity relative to the disk luminosity is LN/LD = 0.7 ± 0.3 compared to 0.05 by SOLINGER and MARKERT. This luminosity ratio enables the nucleus to determine the colour of the scattered light near the minor axis at low and medium distances from the centre.
Large‐scale magnetic fields in discs with strong differential rotation
Authors: Chagelishvili G. D. , Lominadze J. G. , Sokhadze Z. A. 
Published: July 2007

AbstractThe evolution of a large‐scale magnetic field is considered in the non‐linear dynamo situation in discs with α‐effect due to non‐mirrorsymmetric turbulence and with strong differential rotation. The maximal value of the field strength is estimated by using an idealized dependence of the α‐coefficient on the field strength. It is assumed that α is a positive constant if the field strength is below, and equal to zero if the field strength is above a certain critical value. On natural assumptions it can be concluded that the maximal value of the field strength exceeds that critical value by about one power of ten.
About the third integral of charged particle motion in strongly curved magnetic fields
Authors: Büchner J. 
Published: July 2007

AbstractCharged particle motion is studied in magnetic fields with an inversion of field direction and a strong curvature in the reversal region, that means field structures which are expected to play a crucial role in energetics and dynamics of space plasma. Investigations are performed in a typical field model. Due to its symmetry and stationarity two of the integrals of motion of the resulting Hamiltonian immediately arise. The question is analyzed whether the system is integrable (this means regular solutions exist) and of what kind the third integral is. Two different third integrals are found, which are valid in different parts of the phase space. Their validity is estimated analytically for particles, crossing the neutral plane (z = 0) ‐‐ in addition the action integral Iz previously unusual in plasma applications is verified numerically. Further numerical research establishes that there are no more third integrals ‐‐ all remaining parts of the phase space are filled with chaotic solutions.Because in strongly curved field reversals the conservation of the magnetic moment as an integral of motion is shown to be restricted to very small energies or very large pitch angles, the unusual Iz‐integral will be an important tool for solution of plasma problems of cosmical current sheets and plasma boundaries.
Theoretische Betrachtungen zum Verhalten des Magnetfeldes in einem sphärischen Erdmodell
Authors: Greiner‐Mai H. 
Published: July 2007

AbstractDie Lösung der Feldgeichungen des Magnetfeldes im Mantel ist Voraussetzung für die theoretische Behandlung vieler geophysikalischer Probleme. Es werden die Feldgleichungen für ein sphärisches Erdmodell in skalarer Form aufgeschrieben und analytisch darstellbare Lösungen angegeben. Die Randbedingungen werden unter dem Gesichtspunkt diskutiert, daß im Erdkern ein Dynamoprozeß stattfindet und für die Erdoberfläche eine aus Meßinformationen ermittelte Felddarstellung existiert. Es wird die Frage aufgeworfen, inwieweit das Feld im Mantel bei bestimmten Modellanahmen durch diese Felddarstellung bestimmt ist.
Green's functions of the induction equation on regions with boundary. I. General properties and a construction principle
Authors: Bräuer H.‐J. , Rädler K.‐H. 
Published: July 2007

AbstractThe evolution of a magnetic field is considered which pervades an electrically conducting fluid and its non‐conducting surroundings under the influence of electromotive forces due to internal motion and other causes. The governing equations ‐‐ among which the induction equation of magnetohydrodynamics is the most prominent ‐‐ pose an initial value problem for the magnetic flux density. Properties of this initial value problem and of the solving Green's function are reviewed and a general construction principle for the Green's function is given.Detailed treatment of cases where the fluid occupies a sphere or an evenly bounded half‐space are presented in two subsequent papers
Density profiles of suspected optical counterparts of gamma‐ray bursts
Authors: Greiner J. , Lorenz H. , Richter G. M. 
Published: July 2007

AbstractFour suspected optical flashes on archival plates with coordinates within or near to the error boxes of gamma‐ray bursts, respectively, are investigated by surface photometry, Their density profiles are shown to be consistent with that of stars of similar magnitude. Hence, the suspected flashes are not likely to be plate defects but real objects on the sky.