bluuebunny/crossref_metadata_2025 huggingface dataset:
Ein Programm zur Periodensuche bei großen Anzahlen von Meßwerten
Authors: Schöneich W. , Lange D.
Published: July 2007

Es wird eine Methode zur Periodensuche in umfangreichen Meßreihen beschrieben. Das Verfahren beruht, wie die Methode von Lafler und Kinman, auf der Berechnung der Streuung. Da das Verfahren aber nicht der Sortierung der Meßwerte nach der Phase bedarf, lassen sich Periodogramme wesentlich schneller berechnen. Ein FORTRAN‐Programm wird angegeben.
Die wahre periode des rotationslichtwechsels des Ap sterns HD 219749 = ET and
Authors: Hildebrandt G. , Hempelmann A.
Published: July 2007

Die photometrischen Messungen des Ap Sterns HD 219 749 wurden analysiert und mit Hilfe verschiedener Methoden die wahre Periode des Rotationslichtwechsels mit P = 1.61883 Tagen ermittelt. Die in der Literatur außerdem noch angegebenen Periodenwerte konnten zweifelsfrei ausgeschlossen werden.
The Amount of Dust and the Distance of NGC 253
Authors: Issa Issa Ali
Published: July 2007

The areas of 267 dark clouds in the galaxy NGC 253 were measured. It is shown that the size distribution of these clouds obeys the same exponential formula found for the galaxies NGC 3031, 5128, 5194, and 5457. From the apparent size distribution of the dark clouds the amount of dust and the distance of NGC 253 is found to 4.4 · 107 M⊙ and 2.06 Mpc, respectively.
Recovery of the Long Lost Minor Planet (843) Nicolaia after 65 Years (Astronomisches Rechen‐Institut Heidelberg – Mitteilungen Serie B)
Authors: Schmadel L. D. , Kohoutek L.
Published: July 2007

The long lost minor planet (843) Nicolaia was recovered with the 1 m ESO Schmidt telescope after 65 years. This was due to the careful examination of the old 1916 plates and the wellbalanced computation of search ephemerides. An improved orbit based on 19 right ascensions and 20 declinations from the two apparitions 1916 and 1981 is given.
Photometric Elements of the Eclipsing Binary AZ Vir
Authors: Giuricin G. , Mardirossian F. , Mezzetti M.
Published: July 2007

Using WOOD's (1972) model we have analyzed MEINUNGER's (1977) B and V photoelectric light curves – as yet unsolved–of the W UMa‐type eclipsing binary AZ Vir, for which no photometric elements have as yet been determined. Our results describe AZ Vir as a contact pair in which the star eclipsed at the deeper minimum is smaller than its companion. AZ Vir appears to conform to the general properties of the W‐type subclass of W UMa systems.
On the Widths of Dust Layers in Galaxies (Mitteilungen der Universitätssternwarte Jena Nr. 156)
Authors: Hacke G. , Schielicke R. , Schmidt K.‐H.
Published: July 2007

From prints of the Palomar Observatory Sky Survey the widths of the equatorial dust layers of a sample of 39 galaxies seen on edge are obtained to be in the range 500 ≤ D ≤ 1600 pc. The width of a dust layer seems to be correlated with the luminosity of the galaxy. The dust lanes of field galaxies are obviously broader than those of the members of the Virgo cluster. This result may be interpreted as a dust deficiency caused by stripping of interstellar matter resulting from galactic collisions and interaction of the galaxies with the intracluster medium.
The Artificial Earth Satellite Motion in an Oblate, Rotating Atmosphere with Symmetrical Diurnal Effect
Authors: Burs Deva L. , Minier Liceul , Á.Pál
Published: July 2007

The equations describing the disturbed motion of an artificial Earth satellite in the atmosphere are integrated by using a new variable instead of the true anomaly. The atmospheric flattening and rotation, the linear variation of the density scale height with the altitude, the symmetrical diurnal effect and the variation of its amplitude with the heigth are taken into account. Approximate formulae for the perturbations in all the orbital elements over a revolution of the satellite are given.
Inhomogeneous Cosmological Models with Flat Slices Generated from the EINSTEIN‐DE SITTER Universe
Authors: Schmidt H.‐J.
Published: July 2007

A family of cosmological models in considered which in a certain synchronized system of reference possess flat slices t = const. They are generated from the EINSTEIN‐DE SITTER universe by a suitable transformation. Under physically reasonable presumptions these transformed models fulfil certain energy conditions.
New and misclassified Planetary Nebulae
Authors: Kohoutek L.
Published: July 2007

Altogether 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

Periodic 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

Nearly 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

Infall 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

High 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.
Compilation of nearby northern Abell clusters (z < 0.1) with central dominant galaxies
Authors: Baier F. W. , Wipper H.
Published: July 2007

We compiled informations with respect to optical structures, X‐ray structures, cooling flow properties, and X‐ray luminosities, respectively, for 342 nearby northern Abell clusters with central dominant galaxies.
Large‐scale streaming of flat galaxies
Authors: Karachentsev I. D. , Karachentseva V. E. , Kudrya Yu. N. , Parnovsky S. L.
Published: July 2007

We 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

In 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.
The Influence of Waves on Line Formation in Stellar Atmospheres
Authors: Stahlberg J.
Published: July 2007

The influence of acoustic waves on line formation is investigated. The effect of velocity model parameters, e.g. wave number and amplitude, and of the μ‐dependence on line formation are discussed by simplified model assumptions. The effect of waves and Gaussian stochastic turbulence is compared.
Self‐Modulation and Envelope Solitons of Spiral Density Waves
Authors: Meinel R.
Published: July 2007

A 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

We 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

With 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

Determination 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

Photographic 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

Some 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

The 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

The 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

A 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

Der 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

Eine 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

We 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

The 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.
Light curves analysis of AB Andromedae
Authors: Rovithis‐Livaniou H. , Rovithis P.
Published: July 2007

The new B and V light curves of the eclipsing variable AB And obtained during 1979 are analysed. Frequency Domain techniques is used and new geometric and photometric elements are given.
Large‐scale magnetic fields in discs with strong differential rotation
Authors: Chagelishvili G. D. , Lominadze J. G. , Sokhadze Z. A.
Published: July 2007

The 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

Charged 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

Die 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

The 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
Rigidly rotationg perfect fluids
Authors: Kramer D.
Published: July 2007

A class of stationary rigidly rotating perfect fluids in General Relativity is investigated. This class which is characterized by zero Simon tensor contains only the Wahlquist solution and its limits. It is shown how a recently given solution follows from the Wahlquist solution by a limiting procedure.
Density profiles of suspected optical counterparts of gamma‐ray bursts
Authors: Greiner J. , Lorenz H. , Richter G. M.
Published: July 2007

Four 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.
UW Persei
Authors: Richter G. A.
Published: July 2007

Von diesem Doppelobjekt konnte die Durchsicht von 314 photographischen Aufnahmen zusätzlich zu den 3 bekannten historischen Aufhellungen kein weiteres Maximum liefern. Es gelang nicht nachzuweisen, welche der beiden Komponenten die veränderliche ist. Das UV‐Defizit der helleren Komponente macht dessen Zugehörigkeit zur Gruppe der kataklysmischen Veränderlichen nicht sehr wahrscheinlich; für die schwächere Komponente läßt sich keine Aussage machen.
AM Cas — Spectral variations during the eruption cycles
Authors: G. A. Richter , P. Notni , H. Tiersch
Published: July 2007

Spectroscopic investigations of this dwarf nova of Z Camelopardalis type were performed during quiescence and eruption. Although over the period of spectroscopic observations the cycle‐length was only 8d.2 at times, no systematic differences to results on objects of larger cycle‐lengths could be established.
Nonlinear dynamo effects for an inhomogeneously turbulent rotating fluid
Authors: Kichatinov L. L.
Published: July 2007

The mean electromotive force and the turbulent stress tensor are derived for an inhomogeneously turbulent conducting fluid under global rotation. The influence of the mean magnetic field on microscale turbulence is taken into account. As a result, the coefficients of magnetic field generation and sources of differential rotation are now functions of the magnetic field; i.e. nonlinear effects are involved. Only nonlinear corrections quadratic in the magnetic field are included (weak nonlinearity). These corrections reduce the $aL‐effect of the $aL$OM‐dynamo for both slow and rapid rotation. Some astrophysical implications are discussed. It is suggested that observed torsional oscillations of the Sun may be brought about by cyclic variations of the magnetic corrections to theA‐effect of differential rotation over the solar activity cycle.
On the accuracy of the Refraction Tables of Pulkovo Observatory, fifth edition
Authors: Kurzyńska K.
Published: July 2007

A systematic deviation has been found of the refraction given in Pulkovo Tables, fifth edition, from the standard refraction calculated for the same ground level meteorological conditions by the procedure described in one of our previous papers. This deviation, negative for zenith distances smaller than 75° and positive for zenith distances larger than 80°, is considerably greater than the error proven to be admissible for the pure refraction determined in the latter way. The value of deviation is of the order of 0″.03 already at z0 = 45°. For zenith distances smaller than 75° the deviation originates almost exclusively from unsufficiently accurate corrections for the air humidity. For larger zenith distances the deviation originates mainly from the correction for the air temperature and contributions of the remaining corrections can partly compensate for it. In conclusion a proposition of a new unique standard of the pure refraction is stated.
Report on the physical characteristics of Vaidya‐Tikekar's exact relativistic model for a superdense star
Authors: Knutsen H.
Published: July 2007

We report here the results of our examination of the physical properties of Vaidya‐Tikekar's model for a relativistic star. Full details will be published elsewhere. The analysis yields a strong indication that the model is stable with respect to infinitesimal radial oscillations. We find that the adiabatic speed of sound is smaller than the speed of light everywhere inside the fluid sphere if the radius of the sphere is larger than 1.46 times its Schwarzschild radius. We also find that the fluid must necessarily be supraluminal somewhere if the speed of sound is decreasing outwards close to the center. We further find that the strong energy condition is fulfilled everywhere if it is fulfilled at the center. Since the ratio of the pressure p and the density ⋅ is decreasing outwards, this indicates that the temperature gradient is negative. We also find that the relativistic adiabatic index is larger than two. Demanding the fluid to be causal, and taking the pressure and the density to be somewhere given by 7.4 ⋅ 1033 dynes/cm3 and 5.1 ⋅ 1014 g/cm3, we calculate the maximum mass of the fluid sphere to be 3 solar masses.
On Ellis' programme within fourth order gravity
Authors: Schmidt H.‐J.
Published: July 2007

For the non‐tachyonic curvature squared action we show that the expanding Bianchi‐type I models tend to the dust‐filled Einstein‐de Sitter model for t tending to infinity if the metric is averaged over the typical oscillation period. Applying a conformal equivalence between curvature squared action and a minimally coupled scalar field (which holds for all dimensions > 2) the problem is solved by discussing a massive scalar field in an anisotropic cosmological model.
Analysis and results of cooperative magnetographic measurements III. Vertical gradients of the magnetic field in the sunspot photosphere
Authors: Hofmann A. , Rendtel J.
Published: July 2007

We compare vertical gradients of sunspot magnetic fields which were derived for the first time from nearly simultaneous vector magnetograms. The measurements were obtained in the photospheric lines Fe I 5250 and Fe I 5253 by the vector magnetographs of the Sayan‐Observatory (Irkutsk) and the Solar Observatory “Einsteinturm”. The gradients derived from the different measurements show a good correspondence with respect to the numerical values as well as to the morphological structure of the distributions in the magnetograph's field of view. In the umbral region of the spot the vertical gradients amount to about 0.32 Gkm‐1 indicating that the umbral field can extend with strong field strengths into chromosphere and corona. A circle‐like area with opposite sign to the umbral gradient was found on the boundary between penumbra and surrounding photosphere. The physical significance of this area should be the goal of further observations and interpretations.

Wir vergleichen Vertikalgradienten des Magnetfeldes von Sonnenflecken, die erstmals aus fast simultan aufgenommenen Vektormagnetogrammen abgeleitet wurden. Die Messungen erfolgten unter Verwendung der photosphärischen Linien Fe I 5250 Å und Fe I 5253 Å mit den Vektormagnetografen des Sayan‐Observatoriums (Irkutsk) und des Sonnenobservatoriums “Einsteinturm”. Die aus den verschiedenen Messungen ermittelten Gradienten zeigen sowohl hinsichtlich der numerischen Werte als auch bezüglich der morphologischen Struktur ihrer Verteilung im Bildfeld der Magnetografen eine gute Übereinstimmung. Im Kern des Flecks erreicht der Vertikalgradient 0,32 g kin‐1. Das weist darauf hin, daß sich das umbrale Feld mit hoher Feldstärke bis in die Chromosphäre und Korona erstrecken kann. Ein kreisförmiges Gebiet mit entgegengesetztem Vorzeichen zum umbralen Gradienten ist an der Grenze zwischen Penumbra und umgebender Photosphäre zu finden. Die physikalische Bedeutung dieses Gebietes soll durch weitere Beobachtungen und Auswertungen geklärt werden.
On a simple model for self‐regulating star formation in the galactic disk
Authors: Meusinger H.
Published: July 2007

Star formation in galaxies is a process with feedback to the interstellar medium (ISM) and possibly it is part of a self‐regulating cycle. DOPITA (1985) proposed a model in which star formation in spiral and irregular galaxies is self‐regulated by the pressure in the ISM. In the present paper it is shown that available data for radial distributions of gas, total mass and the flux of Lyman continuum photons in the disk of our Galaxy do not support such a simple model. Several possible causes are discussed.
Rotation and free precession of the comet Halley nucleus
Authors: Möhlmann D.
Published: July 2007

Rotational properties (rotation, precession) of the nucleus of comet Halley are investigated on the basis of image processing results of VEGA and GIOTTO and a compilation of recurrence periodicity of 71 events of activity of P/Halley in 1986. It is shown that the analysis of recurrence periodicity gives strong indications for the two periods of 2.2 days and 4.9 days. These periods are well compatible with the three known positions of the nucleus of comet Halley, as they were derived from image processing of the data of VEGA‐1 and ‐2 and GIOTTO. The resulting long‐axis mode of rotation and precession can be described by a 4.9 days rotation around the long axis which is precessing once around the total angular momentum vectorMwith a period of 2.2 days and with an angle θ1= 73° between the long axis and the spatially fixedM, while the angle ω1between the vector Ω of angular velocity and the long axis is given by ω1= 52°.
Instellar extinction curves originated in single clouds
Authors: Krelowski J. , Wegner W.
Published: July 2007

The paper presents great differences between extinction curves derived from spectra of bright nearby stars, likely to be obscured by only single clouds. The differences concern the shapes of the curves as well as the total‐to‐selective extinction ratios (R) which, in some cases, reach the value of about 15. The changes of extinction laws coincide with those of intensity ratios of two prominent diffuse bands at 578 nm and 579.7 nm. We have concluded that physical (optical) parameters of single interstellar clouds differ seriously; interstellar absorption features observed in the spectra of heavily reddened stars are usually ill‐defined averages over many different clouds. The lack of reasonable identification of structural details of interstellar grains follows this fact. The derived individual extinction curves are proposed to be compared with theoretical or laboratory results.
Two populations of open clusters
Authors: Strobel A.
Published: July 2007

The paper proposes a division of the local open clusters into two different disklike subpopulations on the base of the metallicity enhancement history, spatial distribution in the Galaxy and morphology of their C‐M diagrams. The thin disk population objects exhibit higher metallicities and are more closely concentrated to the center and the disk of the Galaxy than the thick disk clusters. The former contain also frequently blue stragglers while the later exhibit the presence of Clump giant members, typical for the thick disk globular clusters. Kinematical properties of the two considered open cluster subpopulations remain unknown due to the lack of observational data.
Relationship of solar coronal millimetre wave sources to bursts in the centimetre range
Authors: Urpo S. , Teräsranta H. , Krüger A. , Hildebrandt Potsdam J. , , Ruždjak V.
Published: July 2007

A sample of 48 observations of coronal mm‐wave (off‐limb) sources (CMMSs) has been analysed in order to check relationships to cm‐wave bursts and to study the emission process. CMMSs appear to be related to gradual and/or stronger microwave bursts with post‐burst increase which start up to a few hours prior to the time of the mm‐wave observations. The lifetime of CMMSs is much larger than that of these bursts. The interpretation of the mm‐wave emission by optically thick bremsstrahlung at the temperature Tb,o ≈ 104 K (which also corresponds to observations in Hα) requires emission measures N2e Δs ≧ 2 · 1028 cm−5 at 37 GHz. On the other hand, optically thin bremsstrahlung at temperatures of Te ≈ 5 · 106–107 K (which are observed in X‐rays) can apply to cm‐waves. Application of this mechanism to mm‐waves, too, would require source sizes much smaller than the half‐power beam width (HPBW) of the radio telescopes (so that in this case the presently observed brightness temperatures Tb,o would be underestimated).
Turbulence influenced line formation in stellar atmospheres
Authors: Stahlberg J.
Published: July 2007

The influence of stochastic velocity fields with finite correlation lengths on the formation of spectral lines is taken into account without restrictions to specific velocity models. To construct a perturbation theory treating the influence of stochastic motion on the radiative transfer we start with the stochastic transfer equation for plane‐parallel atmospheres and expand it to an infinite hierarchical system. An appropriate cut‐off of the infinite system admits to achieve exactly the micro‐ and macroturbulent limit at every level of approach. The formalism is derived forn‐point correlations of the absorption coefficient and specialised for 2‐point correlations.
The line‐ratio method applied to vectormagnetographic measurements
Authors: Bachmann G.
Published: July 2007

Since solar magnetic fields are inhomogeneous, the averaging of Stokes parameter I within the entrance slit of the magnetograph is different from averaging Stokes Q0 and V, because the former contains also light from non‐magnetic, while the latter only contain light from magnetic regions. If the magnetographic calibration functions are calculated for homogeneous magnetic fields, errors arise, when they are used to reduce measurements of inhomogeneous fields. Therefore, we propose to use the line‐ratio method to transform magnetographic measurements into the parameters of the magnetic vector field. The Q ratios and the V ratios of two carefully selected lines are free from errors of this kind. This is also the case for the Q ratios in line core and line wings in single‐line magnetographs. An iterative method is presented to calculate the magnetic field parameters using the corresponding new calibration functions. An important advantage is, that the influence of scattered light in sunspots is also eliminated in a good approximation and the filling factor in plages can be estimated.

This method is now used to determine magnetic vector fields in plages and sunspots of active regions with a new double‐vector magnetograph.
The asymmetry of the Coma cluster of galaxies
Authors: Baier F. W. , Fritze K. , Tiersch H.
Published: July 2007

A detailed reinvestigation of the Coma cluster basing on enlarged observational material of number density distributions and radial velocities of galaxies as well as radio and x‐ray data is performed and supports our previous conclusion that this cluster possesses a substructure. This substructure is in the south‐western region of the cluster and produces the impression of an elongated cluster structure in the direction of the bridge between Coma and A 1367. A 1656 seems to be a cD‐like cluster with NGC 4874 as the only dominating giant central galaxy.
Exact solutions to Kaluza‐Klein cosmologies
Authors: Bleyer U. , Polnarev A. G. , Liebscher D.‐E.
Published: July 2007

We consider general methods to find exact solutions of Kaluza‐Klein cosmologies with phenomenological matter and show some general conclusions about factorwise homogeneous and isotropic models.
Mixed metric perturbations in Kaluza‐Klein cosmologies
Authors: Bleyer U. , Polnarev A. G. , Liebscher D.‐E.
Published: July 2007

We consider metric perturbations of Kaluza‐Klein cosmological models filled with phenomenological matter. We find the exact solution for the development in time of the mixed perturbations, which have one index in the ordinary and one in the internal space. The initial values are assumed to be taken from the results of the quantum fluctuation analysis. The contraction of the internal scales produces effectively massive field modes in the ordinary space. The comparison of this particle creation with dark matter estimations informs us about the fundamental parameters of the model.
Populations of Rydberg states of atoms in nebulae
Authors: Gulyaev S.A. , Nefedov S.A.
Published: July 2007

Populations of highly‐excited states of hydrogen in gaseous nebulae are calculated including effects of lowering the atomic ionization potential. Factors bn and dln bn/dn were computed for a large range of temperature and densities. Collisions only between adjacent levels (Δn = ±1) were included in the set of the statistical balance equations. Results predict the existence of a negative branch of the dln bn/dn curve. They have to be taken into account in calculating the nebulae models.
The calculation of standard coordinates in Schmidt plate astrometry
Authors: Dick W.R.
Published: July 2007

Starting from an exact definition of the tangential point on Schmidt plates the three azimuthal projections used in Schmidt plate astrometry are compared and plate‐tilt effects, which differ from those on astrographic plates, are discussed. It is shown that the azimuthal equidistant projection should be used preferably in Schmidt plate reduction. Practical recommendations are given to minimize the number of significant terms in the reduction model.
Results of magnetographic line‐ratio measurements
Authors: Bachmann G.
Published: July 2007

We adapt the line‐ratio method to magnetographic measurements. The method yields information on inhomogeneous magneitc fields without resolving their fine structure. Supplementing the magnetic field measurements, each day several polarization calibrations were made to eliminate the influence of the instrument. Modified theoretical calibration curves served for the transformation into inclination angles and magnetic field strength. The circular polarization along some scans across two sunspots practically shows the same distributions in both wings. The linear polarization in these selected scans attained only about half as large values as the circular polarization. The maxima were found in the steep parts of the V distributions. Comparing the two lines a similar behaviour was found, but also differences of about 0.5 percent, which may be significant.

The inclination angles determined by means of calibration curves also seem to be more accurate than those calculated from transverse and longitudinal magnetic field components. As an evidence the results in sunspots and faculae are quoted. The values separately determined for the lines scattered only by 3 respectively 7 degrees from the mean values. In the darkest points of an umbra practically accordance of inclination and heliocentric angle was obtained, i.e., the magnetic vector was directed perpendicular to the surface. From the amount of the circular polarization in faculae comparing it with results of model calculations the filling factors were determined. Our results arranged between 3 and 11 percent nearly agree with the values by SOLANKI and STENFLO (1984).

The line‐ratio method in the version adapted to our magnetograph yielded from the V ratios in sunspots an average of 1880 G, but from the Q0 ratios an average of 2240 G. In faculae both values are practically identical and run to 1980 G. These results show that the line‐ratio method is superior to the old reduction procedure of magnetographic measurements.