bluuebunny/crossref_metadata_2025_split huggingface dataset:
Circumstellar disks and rings ‐ observational results
Authors: Elsässer H. 
Published: July 2007

AbstractRecent 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

AbstractStrong 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.
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

AbstractThe 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

AbstractVarious 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

AbstractThe 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

AbstractThe 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 observationsGegenstand 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

AbstractTo 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

AbstractIn 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

AbstractComparing 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

AbstractThe 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractWe 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.
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

AbstractApproximation 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

AbstractThe 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

AbstractThe 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

AbstractWe 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

AbstractScalar 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.
The heterotic string and the Kaluza‐Klein approach to a supersymmetric Einstein‐Yang‐Mills background
Authors: Kuusk P. 
Published: July 2007

AbstractWe 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.
On thermodynamics of fluids, solids and superconductors
Authors: Meier W. 
Published: July 2007

AbstractWe 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

AbstractA 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.
The spectroscopic period of the Cepheid SU Cassiopeiae
Authors: Häupl W. 
Published: July 2007

AbstractThe 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

AbstractIt 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.
On the origin of transient effects in the solar neutrino experiment
Authors: Subramanian A. , Lal Siddeshwar , Yvas P. 
Published: July 2007

AbstractCorrelation 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

AbstractThe 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

AbstractAnalysing 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

AbstractWe 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

AbstractWe 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.