bluuebunny/crossref_metadata_2025 huggingface dataset:
On the problem of secular variability in the stellar initial mass function
Authors: Meusinger H.
Published: July 2007

The hypothesis of secular variations in the stellar initial mass function (IMF) is studied. It is found that neither the present‐day mass function of the nearby main sequence field stars nor the velocity distribution of these stars are contradictory with this hypothesis. The luminosity functions of unbiased kinematically defined age‐groups of the nearby stars also provide no strong constraints. Simple evolution models with time‐dependent IMF and star formation rate enable to fit the data of blue irregular galaxies. Some problems with an universal IMF are pointed out.
Analysis of light curves produced by surface inhomogeneities on magnetic CP stars
Authors: Hempelmann A. , Schöneich W.
Published: July 2007

The problem of the determination of surface brightness distribution parameters from the observed CP2‐star variability, usually explained with the “oblique rotator model”, is discussed.

A simple geometrical model of the surface brightness distribution is derived from the common properties of the observed light curves of these stars. This “spot model” which is supported from the known facts concerning the magnetic field structure and the surface distributions of chemical elements serves as a basis of the special inverse problem: the determination of the number of large scale inhomogeneities, their locations and extents and further parameters, from all the observed light curves of a given star.

A suitable technique for solving the special inverse problem is explained. The problem of ambiguity which even arises for the proposed simple model and, in connection with that, the remaining possibilities to win the relevant information on the inhomogeneities of surface brightness are discussed. For the purpose of illustration, the result of the light curve analysis of the CP2 star HD 8441 is given.
Circumstellar disks and rings ‐ observational results
Authors: Elsässer H.
Published: July 2007

Recent advances in the observation of star‐forming regions at visual, infrared and radio wavelengths have demonstrated that disks or rings of dust and molecules are suspected or even seen to exist around newly borne stars. They might be the prestage of a planetary system. Typical objects of this kind which are discussed in some detail are the bipolar nebula S 106 and the molecular cloud surrounding it as well as the CO outflow source in the dark cloud L 1551 with its central infrared star IRS 5.
Effect of changes in magnitudes of QSOs in their redshift distribution
Authors: Basu D.
Published: July 2007

Strong emission lines may change the brightness of QSOs and hence their observed magnitudes. Since different lines will affect the magnitudes by entering a particular filter at different redshifts, this effect may alter the number of QSOs at a particular redshift and hence the redshift distribution. The present analysis shows that the influence of the emission lines on the U and B magnitudes are significantly correlated to the redshift distribution. It is concluded that the changes in observed magnitudes of QSOs caused by the emission lines have significant effects on the present redshift distribution.
Polarization line radiative transfer in the atmospheres of magnetic white dwarfs
Authors: Nagendra K. N.
Published: July 2007

Some physical mechanisms which can affect the Zeeman line profiles of magnetic white dwarfs are studied. The pure absorption polarization transfer equation is solved including these mechanisms. The broadening of lines in magnetic white dwarfs is briefly discussed.
The connection of the HIPPARCOS reference system to extragalactic objects by photographic astrometry
Authors: Yatsenko A. I. , Rybka S. P. , Scholz R.‐D.
Published: July 2007

The expected error of the connection of the HIPPARCOS system with an extragalactic reference system by means of ground‐based photographic astrometry was calculated. Two different catalogues of proper motions with respect to extragalactic objects and the HIPPARCOS proper motions were simulated. An accuracy of 0″14 per century using only 10 fields with 119 link stars of the Tautenburg Schmidt telescope (134/200/400) and 0″07 per century using 93 fields with 336 link stars of the Kiev long focus astrograph (40/550) were obtained.
Precision in determination of astronomical refraction from aerological data
Authors: KurzyńSka K.
Published: July 2007

Various errors in determination of the local pure astronomical refraction are evaluated versus the apparent zenith distance z0. Numerical integration with the step imposed by heights of an aerological sounding brings the error smaller than 0″01 until z0 = 70°. For larger zenith distances integration with a more dense step is possible after fitting the data to a five‐parameter functional dependence of the refractive index on height. The fitting is simultaneously a good equalization of aerological data reducing considerably their experimental error as well as short‐term local fluctuations of the atmosphere. After equalization, the error in the refraction originating from the error in the aerological data is found to approach 0″01 at z0 = 72°, 0″1 at z0 = 82°, 1″ at z0 = 87°, and 10″ at the horizon. This has to be taken into account when considering systematic deviations of the local pure refraction from that determined in a standard way. The purely stochastic error in the refraction originating in the error of the refractive index at the observation site is discussed within the context of local fluctuations of the atmosphere. It is evaluated that until z0 = 85° the precision in determining the astronomical refraction in a single observation is limited by refraction anomalies (image motion) and only above 85° the error in aerological data becomes more important.
On the gravitational instability in thin gaseous Kepler disks
Authors: Rüdiger G. , Tschäpe R.
Published: July 2007

The idea that the Titius‐Bode law reflects an unstable mode of a self‐gravitationl instability in very thin Keplerian disks makes a careful discussion of the Poisson equation especially necessary. Due to the planetary distances in the solar system (δr/r ⋍ 0·5) the well‐known short‐wave approximation is not appropriate for definite asertions. We will here use a simple series expansion of the relation between the radial and vertical wave numbers of the disturbances which is additionally valid for medium‐scale and non‐zonal modes. The numerical solution of the dispersion relation reveals an extra unstable branch for wave‐lengths of rings and spirals two orders of magnitudes larger than those already known. Though we are not yet able to consider modes long enough for application to the planetary system, we feel the existence of the medium‐wave instability (δr/r ⋍ 0·1) to be a serious challenge for a better, i.e. non‐local theory.
Systematic errors in visual and photographic latitude star catalogues
Authors: Sadžakov S. N.
Published: July 2007

The point discussed is the importance of investigation of the systematic errors of Δδx and Δμx types and their effects on stellar positions as obtained from visual and photographic observations

Gegenstand des Artikels ist die Untersuchung der systematischen Fehler Δδx und Δμx und ihrer Einflüsse auf die Sternpositionen, erhalten aus visuellen und photographischen Beobachtungen.
Astrometrische Verwendung der zweiten kurzen Exposition auf Tautenburger Pilotprogrammplatten
Authors: Scholz R.‐D.
Published: July 2007

To overcome a possible magnitude equation the Tautenburg Schmidt plates of the Lohrmann programme were taken with a long 20‐minute exposure (System A) and a short 20‐second exposure (System C) displaced about 0·5 minute of arc in declination from the long exposure. The distance between the two images in dependence on the magnitude of a star and its position on the plate was analysed. The transformation of coordinates from system C to A can be performed by using first order polynomials. No higher order terms were found to be necessary. The coefficients of the polynomials can not be assumed as constant for all plates but must be computed from least squares solutions involving a sufficient number of stars on each plate. For three of four plates investigated significant orthogonal linear terms were detected.
Green's functions of the induction equation on regions with boundary. III. Half‐space
Authors: BrÄuer H.‐J. , RÄdler K.‐H.
Published: July 2007

In two earlier papers (BRÄUER and RÄDLER 1986, 1987) the evolution of a magnetic field was considered which pervades an electrically conducting fluid and its non‐conducting surroundings. A construction principle for Green's functions of the corresponding initial value problem was proposed, and worked out for the case in which the fluid fills a spherical region. Now the principle is applied to the case of a fluid body occupying a half‐space. Green's functions are constructed for arbitrary motions of the fluid. More concrete results are derived for shear flow, and explicit expressions of Green's functions are given for rigid body motion.
Comparison of three catalogues of absolute proper motions of stars in the M33 field
Authors: Scholz R.‐D. , Rybka S. P.
Published: July 2007

Comparing absolute proper motions of stars obtained by different methods from observations with the Tautenburg Schmidt telescope (134/200/400), the Kiev long focus astrograph (40/550) and the Pulkovo normal astrograph (33/350) the external accuracy of the Tautenburg absolute proper motions was examined. It agrees well with the Tautenburg internal accuracy which is known from earlier investigations as 0″.7 per century. That accuracy was now achieved for all AGK3 stars in the M33 field including the bright stars from 7m to 10m.
The distribution of interstellar dust in nine regions near the galactic plane
Authors: Dubjago I. A. , Tokhtas'Ev S. S. , Urasin L. A.
Published: July 2007

The interstellar extinction and the space distribution of interstellar dust is investigated up to 8–10 kpc in the direction of galactic clusters NGC 6531, NGC 6866, Tr 35, NGC 7062, NGC 7654, IC 1805, NGC 1664, NGC 2251, and NGC 2323 which are located from 7° to 222° in longitude.
Application of an adaptive filtering technique to surface photometry of galaxies. I. The method tested on NGC 3379
Authors: Capaccioli M. , Held E. V. , Lorenz H. , Richter G. M. , Ziener R.
Published: July 2007

This study reports on the results of the application of an adaptive filtering technique to the two‐dimensional photometric mapping of galaxies. For this test we used the elliptical galaxy NGC 3379, which is a luminosity standard. Our plate material (B‐band), obtained with the Tautenburg Schmidt telescope, was digitized with the Babelsberg microdensitometer and with the ESO PDS. The 2‐D scans were reduced according to the Babelsberg Image Processing Systems, whose key feature is an adaptive filter called ‘H‐Transform’. By comparing our results (E‐W light profile and isophotal parameters) to the most recent studies of NGC 3379 (DE VAUCOULEURS and CAPACCIOLI 1979, and NIETO and VIDAL 1984), we found no systematic errors in the photometric calibration and in the reduction procedure, with typical mean residuals from the other studies not larger than ±0.05 B‐mag up to a threshold of 1% of the night sky level on each plate. We also re‐confirmed the geometrical properties of the galaxy. The new filtering technique proved quite efficient in reducing the noise, with negligible effects on the photometric and geometric characteristics of the star‐like sources.
Collapse and explosion in a rotating star
Authors: Ruben G. , Tuominen I.
Published: July 2007

The collapse, bounce, shock wave and expansion of the envelope of a rotating star have been analysed in the adiabatic approximation using the particle‐in‐cell method.

The bounce takes place first in the equatorial plane and a shock wave arises there which shortly afterwards crosses the surface of the star. In the envelope, and to a less extent in the remainder of the star, there is a fast and lasting meridional motion the direction of which changes. As a consequence of the fast meridional motion in the envelope, mass and angular momentum are transported towards the axis of rotation. If the initial star rotates fast enough this will cause a secondary radial expansion in the polar region and a mass ejection. These motions reduce the strong anisotropy caused originally by the equatorial expansion. Strong whirls may arise along the axis of rotation. In the remainder of the star the meridional motion becomes supersonic. The temperature in the envelope depends to a high degree on the choice of the equation of state. Massloss is proportional to the energy initially added. The final loss of angular momentum and of energy is quite large, both losses being about 25%.
Period search using the DMRT method: The properties of the test function
Authors: Andronov Jena I. L.
Published: July 2007

The test function for the method proposed by DUMONT, MORGULEFF, RUTILY, and TERZAN (1978) is investigated analytically and numerically for some examples with constant and variable periods. The properties of the test function of the DMRT method are discussed in comparison with that of the leastsquare method.
The striae in the dust tails of great comets — a comparison to various theories
Authors: Notni P. , ThÄnert W.
Published: July 2007

We reanalyse positions and motion of the striae in the dust tails of the bright comets Mrkos 1957 V and West 1976 VI. Two theories are compared to the data: the high speed particle ejection theory of NOTNI (1964) and the two‐step kinematical sequence proposed by SEKANINA and FARRELL (1980) in their particle fragmentation theory. The final decision is in favour of the two step sequence, though the real situation may be a mixtum compositum of both. The parent clouds (first step) are found to have low lateral velocity dispersion and higher than expected acceleration. The question how these clouds originate remains unsolved. It is suggested that they comprise particles which left the coma into a tailward region of high magnetic field and plasma density. Another possibility, additionally accounting for the sometimes apparent duplicity, is an origin out of an optically thick coma at angles orthogonal to the radius vector.
Investigation of clusters of galaxies. III. An U band photometry in the central part of the Coma cluster
Authors: Baier F. W. , Ziener R.
Published: July 2007

A photographic photometry in U was performed for 288 galaxies in the central field of the Coma cluster of galaxies.
Empirical transformations from U.T. to E.T. for the period 1800–1988 (Astronomisches Rechen‐Institut — Mitteilungen Serie B)
Authors: Schmadel L. D. , Zech G.
Published: July 2007

Approximation formulae describing the long‐term changes in the rotation of the Earth are evaluated. The time scale reduction from Universal to Ephemeris Time can be accomplished by a 12th degree polynomial with a mean error of less than one second for the entire time span 1800–1988. The maximum residuals of least squares fits of the 19th and 20th century data, respectively, can be limited to this accuracy by even simpler expressions.
Recovery of the long lost minor planet (1179) Mally (Astronomisches Rechen‐Institut — Mitteilungen Serie B)
Authors: Schmadel L. D. , West R. M.
Published: July 2007

The orbit of minor planet (1179) Mally which was supposed to be almost hopelessly lost since its discovery in 1931 is rediscussed. Based on a remeasurement of the original Heidelberg plates, two alternative search ephemerides for the perihelion opposition 1986 have been computed. The object was found on the line of variation very near to the predicted position. The recovery was confirmed by the discovery of additional images on UK Schmidt and ESO Schmidt plates as well as on Palomar Sky Survey exposures. There are no further identities of this faint planet among more than 100,000 reported observations of minor planets in this century. Improved elements based on seven apparitions 1931–1986 are given.
Rotating bodies in the bimetric theory
Authors: Avakian R. M. , Chubarian E. V. , Grigorian H. A.
Published: July 2007

The article deals with the physical parameters of rotating bodies in the bimetric theory of gravitation in second approximation in the angular velocity. The authors present the results of calculations carried out for configurations whose state of matter is described by monoparametric equations of ideal neutron gas and relativistic polytropes.
Phase transitions in perturbed stiff‐fluid Friedmann‐Robertson‐Walker cosmological models
Authors: Gleiser R. J. , Diaz M. C. , Grosso R. D.
Published: July 2007

We consider one‐soliton perturbations of a flat Friedmann‐Robertson‐Walker (FRW) cosmological model, with an ideal fluid with pressure equal to the energy density (stiff fluid), in the case where the “pole trajectory” parameter is negative, introducing thereby singularities along certain null hypersurfaces.

Starting with a metric that approaches asymptotically the FR W background, we show that it is possible to construct an extension through these hypersurfaces such that the energy momentum tensor Tab is finite and satisfies the energy conditions. The extension is only C1, providing a sort of “shock front” with continuity in Tab, that has an associated phase transition from null dust to stiff fluid, the transition being of the form described by CHANDRASEKHAR and XANTHOPOULOS.
Scalar fields and the inflationary phase of the cosmic evolution
Authors: Kasper U.
Published: July 2007

Scalar fields are an important ingredient of modern cosmological models describing the very early universe. If they are of the Higgs field type, scalar fields offer a possibility to understand why the cosmological constant is such a small quantity. This is because of the fact that different ground states are possible for a Higgs field. The unstable ground state gives an inflationary stage of the cosmic evolution and a large cosmological constant whereas the stable ground state has a vanishing cosmological constant and is decisive for the late time behaviour with an Einstein‐De Sitter — like expansion law.
Perfect fluids as minimal surfaces
Authors: Kramer D.
Published: July 2007

The minimal surface interpretation of rigidly rotating perfect fluids in General Relativity is extended to include the more general case of differential rotation. The minimal surface corresponding to the Kerr solution is given.
The heterotic string and the Kaluza‐Klein approach to a supersymmetric Einstein‐Yang‐Mills background
Authors: Kuusk P.
Published: July 2007

We are presenting simple arguments to demonstrate that the Kaluza‐Klein approach to the supersymmetric Einstein‐Yang‐Mills fields, that can serve as a background for a heterotic superstring, demands a modified string action that does not contain the dilaton field explicitly.
Affinely invariant field theory
Authors: Liebscher D.‐E.
Published: July 2007

If we require the effective field equations for a local system to be second order partial differential equations, an affinely invariant theory (not presuming the existence of a metric tensor beforehand) has to be non‐local, the action being a multiple integral over the manifold considered.
On thermodynamics of fluids, solids and superconductors
Authors: Meier W.
Published: July 2007

We derive the relativistic Carnot‐Clausius relation and the set of fundamental equations of the thermodynamic system with the aid of Neugebauer's variational principle for several media. Some equations are already well‐known in the literature but here we obtain the full set from a uniform point of view.
Energy accumulating accretion disk orbiting a Kerr black hole
Authors: Paul H. G.
Published: July 2007

A geometrically thin, energy accumulating $aL‐disk is suggested which orbits a Kerr black hole. With increasing internal forces, the “standard” disks develop into energy accumulating disks. These accumulating disks are geometrically thin as long as their internal forces remain below a certain bound, allowing nearly geodesic orbits.
Superstrings and cosmology
Authors: Perlt H.
Published: July 2007

We discuss some aspects of superstring cosmology. Especially, the influence of winding strings on the compactification scenario is emphazised. It is shown that torus compactified superstrings could improve the compactification behaviour.
The spectroscopic period of the Cepheid SU Cassiopeiae
Authors: Häupl W.
Published: July 2007

The spectroscopic period of the short periodic Cepheid SU Cas was determined from the radial velocity measurements by ABT, GIEREN and HÄUPL. The calculated period is 1.949312 days. Radial velocity differences between measurements by GIEREN and HÄUPL are explained as velocity zero point of the used spectrographs. The zero point of the Tautenburg Coudé spectrograph was determined by measuring the radial velocity standard star ϵ Leo. The difference to the standard value was ‐0.7 km/s. No significant differences are found between the spectroscopic period and light curve of SU Cas in the last 35 years.
Improbability of collinear solutions in the n‐body problem with generalized attraction law
Authors: Diacu F. N.
Published: July 2007

It is shown that in the n‐body problem with generalized attraction law (inverse (α + l )‐power of the distance, α > 0) the set of initial conditions which lead to collinear motion is of Lebesgue measure zero and nowhere dense with respect to the set of initial conditions that define solutions in R3 or R2.
Phenomenological models of cosmic phase transitions II. Application of the classical nucleation theory
Authors: Kämpfer B.
Published: July 2007

Classical nucleation theory is applied to follow the thermal history of a homogeneous and isotropic universe during a first‐order phase transition. The dependence of possible supercooling and reheating scenarios on the surface tension and growth velocity of bubbles is discussed.
On the origin of transient effects in the solar neutrino experiment
Authors: Subramanian A. , Lal Siddeshwar , Yvas P.
Published: July 2007

Correlation studies of the pattern of time variation of the recorded solar neutrino flux monitored through the reaction Cl37 → Ar37 with various parameters of solar activity is suggestive of possible emission of a penetrating neutral particle from the sun influencing directly or indirectly the transformation Cl37 → Ar37 deep underground at the required rates. This possibility has to be invoked in view of the difficulties in generating the observed pattern of variations through a large modulatory mechanism involving the electron neutrino. The prediction that follows is the possible existence of a time varying component (diurnal) in the rate of some nuclear transmutations deep underground caused by an unknown neutral radiation having an interaction cross section with matter probably much larger than the canonical value of 10‐36 cm2 per nucleon speculated upon by some authors in the WIMP scenario for the sun.
Generation of localized magnetic fields by dynamos with conducting surroundings
Authors: Meinel R.
Published: July 2007

The investigation of kinematic dynamos embedded in electrically conducting space leads to an eigenvalue problem whose spectrum contains a continuous as well as a discrete part. It is shown that the continuous spectrum has no relevance to the dynamo problem. The determination of the discrete spectrum can be regarded in analogy to the related quantum mechanical problem.

Die Untersuchung kinematischer Dynamos, die in ein elektrisch leitendes Medium eingebettet sind, führt auf ein Eigenwertproblem, dessen Spektrum aus einem kontinuierlichen und einem diskreten Anteil besteht. Es wird bewiesen, daß das kontinuierliche Spektrum keine Bedeutung für das Dynamoproblem hat. Die Bestimmung des diskreten Spektrums kann in Analogie zur entsprechenden quantenmechanischen Aufgabe gesehen werden.
On the periodical structures in populations of galaxies and of clusters of galaxies
Authors: Litvin V. F. , Holzmann F. M. , Taibin B. S. , Popov V. S. , Poljakova G. D.
Published: July 2007

Analysing the distribution of the redshift of clusters of galaxies, obtained from the catalogue of SCHMIDT (1986), two already known periodical structures were confirmed and both periods were extended by a number of periods — approximately by two times (We elucidated 5 new periods in the first structure and 4 in the second.). The statistical significance of these structures was estimated to 0.01 in the first case and to 0.02 in the second one. Particularly, the second structure may be the largest known object in the Universe (about 900 Mpc at H = 75 km s‐1 Mpc‐1). These results agree with the predictions of the axion‐dominated early Universe. In addition, we discovered periodical structures of an another type — in luminosity functions of galaxies, which are members of rich clusters.

Bei der Analyse des Katalogs von SCHMIDT (1986) wurden zwei periodische Strukturen in den Verteilungen der Rotverschiebungen von Galaxienhaufen festgestellt. In den beiden Strukturen wurden 5 bzw. 4 neue Perioden beobachtet, weshalb sich die Periodenzahl in jeder der beiden Strukturen etwa verdoppelt hat. Die statistische Signifikanzen dieser Strukturen wurden zu 0.01 und 0.02 abgeschätzt. Möglicherweise entspricht die zweite Struktur dem größten bekannten Objekt des Weltalls (etwa 900 Mpc bei H = 75 km s‐1 Mpc‐1). Diese Resultate stützen die Theorie eines axiondominierten frühen Universums. Außerdem wurden weitere periodische Strukturen in der Leuchtkraftfunktion von Galaxien aus reichen Galaxien‐haufen entdeckt.
Neutron stars with orbiting light?
Authors: Luká B.
Published: July 2007

We show that the space‐time of nonsingular final states of collapse is not necessarily asymptotically simple and empty (although presently favoured nuclear equations of state seem to lead to this class at least in the spherical case). The other possibility is a neutron star which can keep light on closed orbits.

Wir zeigen, daß nichtsinguläre Endzustände eines Kollapses nicht notwendigerweise asymptotisch einfach und offen sind (wenngleich heute übliche nukleare Zustandsgleichungen wenigstens im sphärischen Falle zu dieser Klasse führen). Der andere Fall ist ein Neutronenstern, der Licht auf einer geschlossenen Bahn halten kann.
The electric potential on dust particles in comets and in interplanetary space
Authors: Tiersch H. , Notni P.
Published: July 2007

We calculate the electric surface potential reached by small dust particles in cometary atmospheres and in interplanetary space. Plasma temperature and density are varied over a wide range; a two component plasma of ions and electrons in thermodynamic equilibrium is assumed. The calculations are performed for three types of grains whose photoelectric and secondary electron emission yield are choosen to cover about the range expected for real dust. Results for vanishing secondary electron emission are given for comparison. At the beginning, a short review of the theoretical formulation and the main assumptions are presented.

Wir berechnen das Oberflächenpotential kleiner Staubteilchen im Plasma einer Kometenatmosphäre und im interplanetaren Raum. Die Plasma‐parameter Temperatur und Dichte werden in einem weiten Bereich variiert, es wird jedoch stets thermodynamisches Gleichgewicht zwischen Elektronen und Ionen eines Zweikomponentenplasmas angenommen. Die Rechnungen werden für drei Teilchenmaterialien ausgeführt, deren Photo‐effekt und Sekundärelektronenausbeute etwa den an realen Staubteilchen vorkommenden Bereich überdecken dürften; zum Vergleich werden auch die Ergebnisse bei vernachlässigbarer Sekundärelektronenausbeute mitgeteilt. Eine kurze Zusammenfassung der theoretischen Grundlagen und der wesentlichen Voraussetzungen ist den Rechnungen vorangestellt.
An interpretation of the variations of the magnetic core‐mantle coupling torques and the core drift rate
Authors: Greiner‐Mai H.
Published: July 2007

The influence of recently computed axial magnetic core‐mantle coupling torques on the Earth's rotation was investigated. These torques derived from poloidal geomagnetic field within the mantle and at the core‐mantle boundary are retarding torques. An accelerating torque due to the action of unknown parts of the core field was estimated by inverse solution of the equation of the mantle rotation for the periodic variations of the quantities of the magnetic field and the length of day. The variations of the drift rate of the Earth's core were compared with those of the mantle rotation velocity for a force‐free Earth. The time constants of the coupling process were estimated and discussed in connection with the magnetic coupling of the mantle with an upper core layer.

Der Einfluß kürzlich berechneter axialer Kern‐Mantel‐Kopplungsmomente auf die Erdrotation wurde untersucht. Diese Lorentz‐Drehmomente, abgeleitet vom poloidalen geomagnetischen Feld im Mantel und an der Kern‐Mantel‐Grenze, sind retardierende Momente. Ein beschleunigendes Drehmoment, das der Wirkung unbekannter Feldanteile zugeordnet wird, wurde durch inverse Lösung der Mantelrotationsgleichung für die periodischen Variationen der Magnetfeldgrößen und der Tageslänge abgeschätzt. Die Variationen der Kerndriftgeschwindigkeit wurden mit denen der Mantelrotationsgeschwindigkeit für eine kräftefreie Erde verglichen. Die Zeitkonstanten des Kopplungsprozesses wurden ermittelt und im Zusammenhang mit der magnetischen Kopplung des Mantels mit einer oberen Kernschicht diskutiert.
The programme “Milky Way”: the physical and kinematical investigation of galactic structures
Authors: Guseva N. G. , Kharchenko N. V. , Schilbach E.
Published: July 2007

The programme “Milky Way” for a complex study of the structure, kinematics and evolution of the Galaxy is outlined. In the framework of the programme new astrometric and astrophysical observations are carried out. Preliminary results concerning the structure of regions of star formation, the motions and the structure of the local spiral arm as well as the dependence of the kinematic parameters of stellar groups on the distance from the galactic plane are presented. These investigations were based on the new observations within the programme “Milky Way” and data from previously published catalogues.
A method for modelling the surface of irregular celestial bodies
Authors: Wiebicke H.‐J.
Published: July 2007

The surface function R(9) of irregular celestial bodies (small satellites like Phobos and Deimos, cometary nuclei or small asteroids) is expanded in terms of spherical harmonics. A method is given to determine the expansion coefficients by comparing the calculated contours with the contours extracted from a series of images of the body. With given expansion coefficients this method can be applied to orientation systems of the spacecraft approaching the body. Furthermore, physical quantities like volume, centre‐of‐mass coordinates, moments of inertia and the gravitational field of the body can be calculated analytically. Under the assumption that the gravitational potential can be determined experimentally a method is described to calculate the radial mass density profile of the body.
The quasar population density as a result of the formation rate and the evolutionary pathes. I. Analytical formulas and numerical simulations
Authors: Boller T. H. , Liebscher D.‐E.
Published: July 2007

The continuity equation of CAVALIERE et al. (1971) is generalized to age‐dependent luminosity evolution. We show that some simple cases (monomial forms of the formation rate) are integrable and compare some important features. Test procedures and the adaption to the observations are considered in the following parts.
Note on the orbit of the magnetic star 53 Cam
Authors: Oetken L.
Published: July 2007

Based on the known spectroscopic orbital elements of 53 Cam the positions of the companion for times of speckle observations were predicted and compared with the observed positions. Taking into account the ambiguity in speckle interferometry the observations can be represented fairly well by an inclination of approximately 45° between orbital and tangential plane.
On the relation between activity and rotation in main‐sequence stars
Authors: Teplitskaya R. B.
Published: July 2007

A modified index of the level of stellar chromospheric activity, A'Call, is proposed. It is calculated from the measured emission flux density in cores of Ca II H and K lines; however, unlike the other known indices, it is free from the influence of the colour of a star. Application of the new index leads to amodified activityrotation relationship in lower main‐sequence stars. It is shown that in the coordinate system log A'Call, log Ro (Ro being Rossby number) F‐M stars obey a common relationship corresponding to the parameter α = 1.6. The obtained curve shows no evidence for activity saturation for stars with small Rossby numbers, but in slowly rotating stars with thin convection zones the activity level tends to a constant value.
The estimation of distances to Hyades and Praesepe clusters by a geometrical method
Authors: Loktin A. V. , Matkin N. V.
Published: July 2007

The capability of a geometrical distance estimation method is verified by numerical modelling for the Praesepe cluster. The distance estimated by Hertzsprung's method is r = 175 ± 47 pc. The same method gives for the distance to the Hyades r = 48.4 ± 2.2 pc.
An apparent highly sheared magnetic field structure generated by a subphotospheric current system
Authors: Linke J. , Bachmann G.
Published: July 2007

Using Potsdam vector magnetograms and a force‐free model, we have investigated the magnetic field structure of the active region BBR 18474 of 1982 July 15 and 1982 July 16. By comparison of the azimuths of the current‐free model of magnetic field structure in the central part of this active region with the map of the azimuth values estimated from the observation we find a good qualitative agreement. Additional earlier results have shown that the apparence of highly sheared magnetic field structure near the neutral line in the central part of this active region may be a simulated effect generated by a subphotospheric current system.
Diffuse interstellar bands — an observational review (Review)
Authors: Krelowski J.
Published: July 2007

The paper presents a review of observational data concerning the unidentified diffuse interstellar bands (DIBs). The history of the investigation of these fascinating spectral features is presented together with very recent results obtained with the aid of solid state detectors. The high signal‐to‐noise spectra allowed to divide diffuse bands into at least 3 families defined as sets of these features characterized by constant intensity ratios in every observed spectrum. “Intrinsic” profiles of DIBs, i.e. profiles that originated in single interstellar clouds free of any Doppler splitting were derived from high resolution spectra. The same observations revealed convincingly the Doppler structures inside DIB profiles observed in distant objects. It is shown that DIBs may originate in clouds of very low opacity — their agent(s) being thus resistant against diffuse UV radiation. The agent(s) seems not to be the dust causing the visual extinction as the bands may be absent in some of reddened spectra. Relations between DIBs and other interstellar absorptions are also briefly reviewed.
Determination of dust properties and magnetic fields from polarimetric and photometric observations of stars (Review)
Authors: Voshchinnikov N. V.
Published: July 2007

Various models of the interstellar extinction and polarization are considered. Special attention is devoted to alignment mechanisms of the dust grains, such as Davies‐Greenstein mechanism and suprathermal spinning alignment, and their approximate versions. It is concluded that the grain size and the strength and the direction of the interstellar magnetic field may be estimated from the extinction and polarization data. Applications of the theoretical results to the observations of the stars in the galactic plane are discussed.
uvby photometry of open clusters
Authors: Reimann H. G.
Published: July 2007

Für insgesamt 40 Stern im Gebiet des verfärbten offenen Haufens NGC 6871 erhieken wir eine uvby Photometric. 21 dieser Sterne klassifizierten definitely as members. From the photometric results we derived 1.2 × 107 years as the cluster age, 2440 pc as its distance, and E(b ‐ y)) = 0.348 mag as mean reddening of the cluster. From the scatter around this mean colour excess and the deviation of a subgroup of stars by more than twice the standard deviation a varible intracluster reddening in order of 0.1 mag is indicated. The value of the colour excess ratio E(b ‐ y)/E(B ‐ V) = 0.705 for the cluster stars leads us to the conclusion that the very broadband structure (VBS) in the spectra of the cluster stars must be very weak.

Für insgesamt 40 Stern im Gebiet des verfärbten offenen Haufens NGC 6871 erhielten wir eine uvby Photometrie. 21 dieser Sterne klassifizieren wir definitiv als Haufenmitglieder. Aus den photometrischen Ergebnissen leiteten wir ein Haufenalter von 1.2 × 107 Jahren, eine Entfernung von 2440 pc und eine Verfärbung E (b ‐ y) = 0.348 mag ab. Aus der Streuung um diesen mittleren Farbexzeß und der Tatsache, daß eine Gruppe von Sternen um mehr als die doppelte Standardabweichung von diesem Wert differiert, läßt sich eine Verfärbung innerhalb des Haufens in der Größenordnung von 0.1 mag vermuten. Aus der Größe des Farbexzeßverhältnisses E(b ‐ y )/E(B ‐ V) = 0.705 schließen wir, daß die Breitbandstruktur (VBS) in den Spektren der Haufensterne nur sehr schwach ausgeprägt sein kann.
Carbon altotropic composition of interstellar grains
Authors: Maron N.
Published: July 2007

Extinction curves for core‐mantle and muiticored grains containing two allotropic carbon modifications are compared with far UV extinction observations of the stars R CrB and RY Sgr as well as interstellar extinction. We show that these grain models are consistent with the observed far UV extinction, but it is found that only those particles in which amorphous carbon is surrounded by graphite fit well the interstellar extinction curve and that of the R CrB‐type stars.
Polarized light from circumstellar dust: observations and models
Authors: Šolc M.
Published: July 2007

Two models of a biconical dust nebula with an opaque torus in the symmetry plane are presented: a model containing dust in the whole biconical space (A) and an “empty” model with the dust layer on the surface of this empty space (B). Surface brightness distribution and polarization of the emitted light are computed using the Monte Carlo simulation of photon transport in the nebula. The results have features similar to those observed in several compact reflection nebulae.
Modelling of the radiative transfer in the dust shell around n Carinae
Authors: Men'Shchikov A. B.
Published: July 2007

Evolutionary models of structure and spectrum of the dust shell around n Carinae are constructed by means of radiative hydrodynamics calculations. Processes of dust grain growth and destruction are included in the models. The results of the modelling enable us to put some constraints on possible parameters of the object. The theoretical light curve and the spectrum in the visual and infrared are in a good agreement with the observations.
Molecular maser radio emission in the environment of young stellar objects (Review)
Authors: Rudnitskij G. M.
Published: July 2007

A brief review of properties of molecular maser sources in star‐forming regions is given. Different types of sources, their structure and variability are discussed. The variability of H2O masers at a timescale of several days observed in the case of the Cep A maser source is difficult to explain in the model of energy diffusion inside a maser cloud. Another possibility is suggested and analysed. An H2O maser flare may be due to amplification of a strong nonthermal radio flare of the magnetically active central young star (possibly, of the T Tauri variability type) by an initially unsaturated H2O maser. An observational test is suggested.
Pumping cycles of cosmic masers: sense and methods of investigation
Authors: Sobolev A. M.
Published: July 2007

The principles of the search and analysis of the routes of population transfer between the energy levels of quantum systems are formulated. Using the Monte‐Carlo technique it is shown that the number of pumping cycles of cosmic masers may be rather large. For example, the pumping mechanism of the H2O JKK. = 616 – 523 line in a two‐temperature gas needs approximately 2 ± 1013 cycles to account for 75% of population transfer between the maser levels. The degree of participation of various types of cycles in the total population exchange between maser levels is suggested as a means for determining the thermodynamical type of the pumping mechanism. The type of a cycle is determined by the nature of residual population transfer in its ascendant (source of energy) and descendant (sink) transitions. The nature of the transition is definite, if the residual transfer caused by the processes of a certain kind greatly exceeds the others. The knowledge of the degrees of participation of individual levels and transitions provides the possibility to decide whether the scheme of levels and transitions is adequate for kinetical investigations.
Influence of molecular outflows from young stellar objects on molecular clouds
Authors: Henning TH.
Published: July 2007

In this paper it is investigated whether molecular outflows can support the turbulence in molecular clouds against decay. In the momentum‐driven regime of molecular flows the time scale of the replenishment of the fluctuations is longer than the dissipation time scale of pure hydrodynamical supersonic turbulence.
Molecular clouds and the formation of open clusters
Authors: Stecklum B.
Published: July 2007

Using analytical approximations of the mass spectra of molecular clouds and stellar systems including open clusters and associations a relation between the final star formation efficiency (final SFE) and the initial cloud mass is derived. The dependence of the SFE on cloud mass is estimated for two cases of molecular cloud destruction by stellar winds in spherical geometry. The result of growing SFE with rising cloud mass does not agree with current observations and the above relation. A decrease of the SFE is expected if the fraction of high‐mass stars grows with increasing mass of the cloud.
Populations of Rydberg levels of atoms in the interstellar medium
Authors: Gulyaev S.A. , Nefedov S.A.
Published: July 2007

Populations of Rydberg levels of atoms are calculated including effects of lowering the atomic ionization potential. Due to these effects the boundary conditions in bn problem is lim bn = 0. The bn factors were computed for T = 100 K. Ne = 0.1 cm−3 with bn = 0 when n ≧ 3000.

The result allows to interpret observational data of the carbon decametric lines without the use of the subthermal dielectronic recombination mechanism. The calculations predict high relative intensities of Cnβ and Cnγ lines.
Continuum beyond the Lyman limit and effective temperatures of the nuclei of planetary nebulae
Authors: Golovatyj V.V. , Pronik V.I.
Published: July 2007

Using published data on Hß‐,λ4471 Hel‐ and λ4686 Hell‐line fluxes for planetary nebulae the energy distribution in their nuclei is calculated in the wavelength range 100–912 Å by supposing that 1) the spectrum inclination is the same in the regions of continuous absorption of Hl, Hel, and Hell atoms; and 2) discontinuities at 504 Å and 228 Å are present in the nuclei spectra.

From 40 investigated nebulae, only for two nuclei the distribution in all three intervals 504–912 Å, 228–504 Å and λ ≦ 228 Å corresponds to one and the same temperature of black‐body emission. In 24 cases the emission temperature is the same for the first and the second interval. The energy distribution in the wavelength range shorter than 228 Å corresponds systematically to very high temperatures T* > 100,000 K. It is concluded that the emission temperature over the surface of nuclei is markedly inhomogeneous and/or the nuclei of planetary nebulae possess a hot corona.
Kukarkin‐Parenago relationship, period gap, and cause of dwarf nova outbursts
Authors: Richter G.A. , Bräuer H.‐J.
Published: July 2007

It is shown that it can be useful to incorporate the orbital period P as an additional parameter into the Kukarkin‐Parenago relationship. Then it turns out that the relationship splits into two, one holding for objects above and the other for objects below the well‐known and much‐discussed period gap between 2.2 and 2.8 hours

A = ‐2.03 + 2.26 log C + 8.80 log P for P > 2.2 h

A = 2.07 + 2.46 log C ‐ 3.68 log P for P > 2.8 h

(A amplitude (mag), C cycle length (d), P orbital period (h)).

Future theories of the dwarf nova phenomenon and the origin of the period gap will have to deal with this.
Photoelectric and visual observations of AM Cas
Authors: Richter G.A. , RÖSSIGER S.
Published: July 2007

According to statistical informations the orbital period of this cataclysmic binary of Z Camelopardalis type should be in the range between 0d.10 and 0d.19. A sole deep minimum was found photoelectrically. It lasted about 40 minutes and had an amplitude of nearly 2 mag in U. For reasons described in detail it can hardly be interpreted as an eclipsing one. Possibly there is no contribution to the light variation of AM Cas from orbital motion.
Motion of the Earth's inner core and related variations of polar motion and the rotational velocity
Authors: Jochmann H.
Published: July 2007

Correlations between the geomagnetic field parameters and polar motion were explained using the hypothesis of an inner core motion. For a number of periodic constituents of both phenomena it could be proved that this model works well. Secular variations of polar motion caused by inner core dynamics are in the same order of magnitude as the secular variation of the pole derived from pole coordinates of the International Latitude Service (ILS).
Catalogue of non‐Abell clusters of galaxies with published photometric data
Authors: Baier F. W. , Ziener R.
Published: July 2007

This catalogue is a compilation of references of publications with photometric data in and around non‐Abell clusters of galaxies.
Magnetic field and radial velocity of the Ap star 52 Her. I. Observations, measurements, results
Authors: Gerth E.
Published: July 2007

Since 1971 the magnetic Ap star 52 Her has been investigated with respect to its magnettic field and radial velocity on the observational basis of 140 photographic Zeeman spectrograms obtained at the 2m‐telescope in Tautenburg. Additionally, 47 normal spectrograms were used for the determination of the radial velocity only. The technical foundation for observation and measurement is considered. The main purpose of the paper, however, is the documentation of the observations and the measuring results. Deductions drawn from the material assorted here or taken from other sources are put off to following papers.
On linear light polarization of novae: dust envelopes
Authors: Kučinskas A.
Published: July 2007

A review on linear light polarization studies of novae is presented. It is shown that light scattering on dust grains (predominantly graphite) in nova environments is playing a principal role in generation of linear light polarization. A qualitative model responsible for this phenomena is discussed.
Diffussion of a scalar field in a compressible turbulent medium
Authors: Silant'Ev N. A. , Korolkov M. D.
Published: July 2007

The diffusion of scalar fields (temperature, density number of some admixture) in a compressible medium showing an isotropic, homogeneous and stationary turbulence is considered. The derived formulae for turbulent diffusivity χT(ξ) hold up to ξ ≈ 1, where ξ = u0 τ0/R0 (u0, τ0, and R0 are characteristic velocity, life‐time, and correlation length of turbulent pulsations, respectively. The velocity field of turbulent motions u(r, t) is assumed to be known and the influence of the scalar field onto u(r, t) is neglected. It is shown that the velocity correlators, which change their signs in dependence on the space corrdinates, may give negative values for ξT(ξ) when ξ ≠ 0.
Relativistic Astrophysics and Gravitation
Authors: Gottlöber S. , Haubold H. J. , Liebscher D.‐E. , Mücket J. P. , Müller V.
Published: July 2007

Proceedings of the Ninth Potsdam Seminar on Relativistic Astrophysics and Gravitation, held in Wusterhausen, GDR, 1989, October 23–28