bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation pressure — a stabilizing agent of dust clouds in comets?
Authors: Fr$Ouhlich H.‐E. , Notni P. 
Published: July 2007

AbstractThe internal dynamics of an illuminated dust cloud of finite optical thickness is investigated. The dependence of the radiation pressure on the optical depth makes the individual particles oscillate, in one dimension, around the accelerated centre of gravity of the cloud. The cloud moves as an entity, irrespectively of the velocity dispersion of the particles and their efficiency for radiation pressure. If the optical depth does not change, i.e. if the cloud does not expand laterally, its lifetime is unlimited. A contraction caused by energy dissipation in mechanical collissions between the dust particles is expected.The range of particle sizes which can be transported by such a “coherent cloud” is estimated, as well as the acceleration of the whole cloud. The structure of the cloud in real space and in velocity space is investigated. A comparison with the “striae” observed in the dust tails of great comets shows that the parent clouds of these striae may have been of the kind considered.
Runaway instabilities in geometrically thin accretion disks around Kerr black holes
Authors: Elstner D. , Paul H. G. 
Published: July 2007

AbstractThe stability of the innermost disk region orbiting a Kerr black hole is investigated for geometrically thin accretion disks. The infalling matter transports mass and angular momentum into the Kerr hole. This affects the inner disk boundary and leads to runaway instabilities in some cases.
Harmonic maps from spacetimes and their coupling to gravitation
Authors: Schimming R. , Hirschmann T. 
Published: July 2007

AbstractThe paper focusses on harmonic maps f from an m‐dimensional space‐time or Lorentzian manifold into an n‐dimensional properly Riemannian field manifold: the energy‐momenturn tensor of f, the coupling of f to a gravitational field, and the Cauchy problem to the harmonic map equations are studied.
Die Entdeckung eines neuen Asteroiden (1988BJ) vom “Hungaria”‐Typ
Authors: Elst E. W. , Goffin E. 
Published: July 2007

AbstractWährend eines Asteroiden‐Beobachtungsprogramms in Haute Provence (Frankreich) wurde am 22. Januar 1988 ein Asteroid 17. Größe entdeckt (Elst 1988). Weitere Beobachtungen an der Europäischen Südsternwarte (ESO) und eine vorläufige Bahnbestimmung ergaben, daß der Asteroid zur “Hungaria”‐Familie (Resonanzgruppe) gehört.
On the cosmological evolution of the quasar population
Authors: Boller T. H. , Lorenz H. , Afanas'Ev V. L. , Dodonov S. N. , Yu. Terebizh V. 
Published: July 2007

AbstractTwo selected fields (south east of the galaxie M 82 and in SA 57) are completely spectroscopically searched for quasars. The (N — m) relation is enlarged by 0.4 and 1.6 magnitudes with regard to the value determined by KRON and CHIU (1981). Consequences for models of the evolution of the luminosity function are discussed.
Possibilities of investigation of interstellar matter by radio recombination lines (Review)
Authors: Sorochenko R.L. 
Published: July 2007

AbstractRadio recombination lines (RRL) discovered about 25 years ago became a very effective tool for the investigation of interstellar matter (ISM). These lines are unique by the number of transitions and the spectral range observed: from 2 mm to 20 m wavelength. This allows to study the ISM under variety of physical conditions which differ by 7 to 8 orders of magnitude in density and 3 orders of magnitude in temperature.RRL allow to determine the main physical conditions in HII and HI‐CII regions, to map the galactic distribution of ionized hydrogen, and to obtain the helium abundance of the ISM. Furthermore, the information contained in the RRL allows to estimate the intensity of cosmic rays and to draw conclusions on the galactic evolution.The physical properties of the RRL and the results obtained by observations of RRLs are reviewed.
Physical processes in the interstellar matter determining parameters of radio recombination lines in meter and decameter ranges
Authors: Bochkarev N.G. 
Published: July 2007

AbstractWe give a review of problems connected with the interpretation of meter and decameter carbon radiolines. The lines are formed inside clumps of molecular clouds in layers with a column density N ≈ 6 · 1021 cm−2. These clumps are very typical structures. The distribution of physical parameters (number density, temperature, etc.) inside the clumps is poorly known. The most difficult and important question is the penetration of subcosmic rays into the clumps. Observations show that the ionization rate is ζ = (1–7) · 10−17 s−1 inside molecular clouds and significantly greater in the diffuse gas. Long‐wave radio recombination lines can probably be used for the analysis of the distribution of subcosmic rays inside molecular clouds. The interpretation is complicated by the influence of low‐temperature dielectron recombination and poorl known variations of carbon depletion in the clumps.
Three‐dimensional distribution of high‐velocity stars
Authors: Greiner J. 
Published: July 2007

AbstractNumerical calculations support the conjecture that high velocity stars born in or near the rotating disk are not distributed spherically throughout the galaxy. Instead an empty funnel region forms around the rotation axis of the galaxy, where no stars reside. The funnel appears only for high velocity stars, such as old pulsars. Within about 50 kpc distance from the galactic center the funnel shape is almost not dependent on the existence of a massive corona.
A survey of the peculiar radio emission of the solar behind‐limb event on 16th February 1984
Authors: Chertok I. M. , Fomichev V. V. , Gorgutsa R. V. , Markeev A. K. , Podstrigach T. S. , Aurass H. , Hildebrandt J. , Kliem B. , Krüger A. , Kurths J. , KarlickýA M. , Tlamicha A. , Urbarz H. W. , Zlobec P. 
Published: July 2007

AbstractBasing on radio measurements from different stations the paper presents a compilation of observations and resultinng questions concerning the interpretation of some remarkable features of the solar behind‐limb event on 16th February 1984. The event was related to a very strong relativistic particle emission. Attention is paid to the related microwave radiation stimulating a discussion of the discrimination between plasma and gyromagnetic radiation being important for plasma diagnostics. Another outstanding feature is the occurrence of a spectacular multi‐band U‐shaped type II burst pattern challenging a discussion of possible higher harmonic plasma radiation.
The massive scalar field in a closed Friedmann universe model — new rigorous results
Authors: Schmidt H.‐J. 
Published: July 2007

AbstractFor the minimally coupled scalar field in Einstein's theory of gravitation we look for the space of solutions within the class of closed Friedmann universe models. We prove D ≥ 1, where D ≥ is the dimension of the set of solutions which can be integrated up to t → ∞ (D > 0 was conjectured by PAGE (1984)). We discuss concepts like “the probability of the appearance of a sufficiently long inflationary phase” and argue that it is primarily a probability measure μ in the space V of solutions (and not in the space of initial conditions) which has to be applied. μ is naturally defined for Bianchi‐type I cosmological models because V is a compact cube. The problems with the closed Friedmann model (which led to controversial claims in the literature) will be shown to originate from the fact that V has a complicated non‐compact non‐Hausdorff Geroch topology: no natural definition of μ can be given.We conclude: the present state of our universe can be explained by models of the type discussed, but thereby the anthropic principle cannot be fully circumvented.
New solutions in linearized R+R2 gravity
Authors: Teyssandier P. 
Published: July 2007

AbstractA general method is proposed to solve in the linear approximation the fourth‐order gravitational equations, which stem from Lagrangians \documentclass{article}\pagestyle{empty}\begin{document}$ \text{Q} = 1 &#x02010; g\left( {R + \frac{1}{2}aR^2 + bR_{av} R^{av} } \right) &#x02010; x\text{Q}. $\end{document} The metric of a static spherically symmetric body and the metric of a straight infinitely thin cosmic string are given.
Electromagnetism and gravito‐inertial behaviour in Einstein's unified field theory
Authors: Antoci S. 
Published: July 2007

AbstractSources are added to the field equations of Einstein's unified field theory and a purely electromagnetic model of matter is proposed, in which all the properties of the material sources ultimately depend on one four‐current. Examples show that between charged matter built in this way electrodynamic interactions only arise when there is true scope for them, i.e., when the previously mentioned current deviates from geodesic flow.
Topological approach to nonlinear models of molecular electronics: Topological solitons, phenomenology, and compactification
Authors: Nikolaenko V. M. , Rambidi N. G. 
Published: July 2007

AbstractThe U(1) × SO(1,1)‐gauge field model of gravitating topological solitons is considered for the physical construction of information logic devices at the molecular level. It is of interest due to stability both from the energetical and the topological point of view. Coupled to the Weinberg‐Salam theory of electroweak interactions, the gravitating solition may be stable in the case of the negative curvature. The case of positive curvature leads to a radius over 10−11 cm.
Magnetic field topology of an active region
Authors: Linke J. , Ioshpa B. A. , Selivanov V. L. 
Published: July 2007

AbstractThe global 3‐dimensional topology of the magnetic field of the weakly flaring active region AR 5420 in the early phase has been estimated using a series of photospheric longitudinal and vector magnetogams together with Hα filtergrams and white‐light images. As a physical model for this task, we have used the assumption ofa force‐free magnetic field character. An arcade‐like structure of the magnetic field has been identified in the preflare phase with an apparent sheared configuration already present in the current‐free field case. This system might have been an important source of generation of a field‐aligned current system for the eruptions that followed. That was, in particular, suggeted by a significant extension of the active region area in the observation period from June 22 to 25, 1984, that resulted in a stronger shear of the detected arcade‐like system. The atmospheric electric currents generated in such a way and the transition triggered by a large‐amplitude perturbation generated by new flux emergences on June 23 at this place together might be the reason of the sequence of flares observed. Despite the changes in the Hα structure, the global force‐free character of the field did not change significantly over the time of observations. The invariance (in the first order) of the force‐free (nearly current‐free) character of the magnetic field is consistent with the occurrence of relatively small flares only.
On gravitational instability in a multi‐component cosmological medium
Authors: Haubold H.J. , Mathai A.M. , Mücket J.P. 
Published: July 2007

AbstractThe paper presents results for deriving analytic solutions of the non‐relativistic linear perturbation equations, which govern the evolution of inhomogeneities in a homogeneous spatially flat multi‐component cosmological model. The multi‐component dark matter problem is reviewed.
Evolution of a magnetic blob in a helical flow
Authors: Reshetnyak M. , Sokoloff D. , Shukurov A. 
Published: July 2007

AbstractAn intermediate stage of magnetic field evolution in kinematic dynamo systems, during which the growing field does not coincide with the leading eigensolution, can be physically important in those cases, if the difference of the growth rates of individual dynamo eigenfunctions is small in comparison with the growth rates themselves. The eigenvalue problem is also insufficient for complete analysis of evolution of an initial distribution of magnetic field which is initially concentrated within a small portion of the dynamo volume. In this case there arise magnetic fronts which spread over the whole volume. Here we solve the Cauchy problem, which describes such situations, for the case of helical axisymmetric flow, the screw dynamo.We consider evolution of an initially small magnetized region (called here a “blob” or “magnetic packet”) embedded in the axisymmetric helical flow. A prototype of such flow is a helical flow in a tube or a swirling jet. As shown below, the group velocity of such magnetic packet is equal to the fluid velocity at the radius where the eigenfunction concentrates which has the maximal growth rate. The field within the packet grows at this rate. On the contrary, the growth rate of the field outside the packet (within the jet) grows at another rate given by the growth rate of the eigenfunction which has the minimal oscillation frequency v, i.e. dv/dk = 0, where k is the longitudinal wave number. If the latter growth rate is negative, the field within the jet decays and the growing magnetic packet moves through the jet leaving it unmagnetized.
On the discovery of the Trojan object 4060 = 1987 YT1 = Deipylos
Authors: Elst E.W. , Debehogne H. 
Published: July 2007

AbstractDuring an extensive search in 1987 for new Trojan objects with the ESO Schmidt telescope, two new Trojans were discovered. One of these objects, 1987 YT1, was recovered at the subsequent dark run at ESO by DEBEHOGNE with the GPO instrument used in the astrographic mode.New observations in 1989 by ELST at the GPO and ESO Schmidt led to definite numbering (4060) and naming (Deipylos) of this Trojan object. The orbit is calculated starting from the discovery 1987/88 observations using a classic Gaussian procedure. The orbit is subsequently improved by the method of the variation of the geocentric distances. These orbital elements are compared with the osculating elements which have been obtained from orbit calculation using all available observations (1942–1989).
Helium surface distribution on He‐peculiar stars
Authors: Vetö B. , Hempelmann A. , Schöneich W. , Stahlberg J. 
Published: July 2007

AbstractA method has been developed to determine the geometrical parameters of surface distributions of chemical elements on a spotted rotator from observations of variable line strengths. On the basis of simple assumptions for spot geometry and limb darkening this problem has been traced back to the same inverse problem as the determination of surface brightness parameters from photometric observations. The method was applied to eight He‐peculiar (CP4) stars (HR 1441, HR 1890, HR 1932, HD 37776, HR 2509, HR 3089, HR 5387 and HR 7129) to derive the He surface distribution of these He‐rich and He‐weak stars from the line strength variation of the HeI λ 4026 line. The result and a discussion of the analysis is given.
On star formation in cooling flows of clusters of galaxies
Authors: Schmidt K.‐H. 
Published: July 2007

AbstractA correlation between the masses of cooling flows in clusters of galaxies and the absolute magnitudes of the central parts of the brightest galaxies of the clusters is detected. This correlation is consistent with star formation in the cooling flows according to an initial mass function of stars truncated at stellar masses corresponding to absolute magnitudes in the most probable cases between +7 and +2.
A coarse analysis of Seyfert‐I narrow‐line properties
Authors: Rafanelli P. , Schulz H. 
Published: July 2007

AbstractMedium‐resolution spectrophotometry of 19 Seyfert‐I galaxies with Mv between ‐20m and ‐24m is presented. Balmer line broad and narrow components are decomposed and relative narrow‐line intensities are compared with a grid of power law photoionization models. Diagrams displaying ratios of strong forbidden lines are devised which allow to read power law indices α and ionization parameters U for individual objects. On the average, α‐values derived from [O I]/[O III] versus [N II]/[O III] are in good agreement with power‐law slope indices αux derived from continuum measurements at 1450 Å (U) and 0.7 keV (X). However, for the same parameters, the theoretical [S II]/[O III] values appear to be 40% too large. Based on trends in current photoionization models we suggest that this discrepancy might be removed by including a black‐body component in the ionizing continuum and a high‐density component in the narrow‐line region. Mkn 1044 has been isolated as an unusual object whose strong [S II] λλ4068,4076 feature suggests that its NLR emission is dominated by a high‐density zone with Ne ∼ 107 cm‐3.
Synthetic curves of some observational properties of contact binary asteroids
Authors: Hoffmann Martin 
Published: July 2007

AbstractThe shape of some asteroids may be deduced by other ground based means than rotation light curves or advanced techniques like speckle imaging or radar observations: the analysis of high precision astrometry and lunar occultation light curves. Calculations of the phenomena among the cosmogonically interesting case of a double asteroid configuration, when the objects are in contact with each other, are presented with special emphasis on the involved shadow phenomena.
FÖPPL's negative gravity masses and the repulsive cosmos
Authors: Treder H.‐J. 
Published: July 2007

AbstractFÖPPL (1897) distincts between the positive inertial masses and gravity masses which may have positive and negative signes. FÖPPL has proved the masses with opposite signes of gravity each other repel. For our normal matter the principle of equivalence is valid. Our “world island” is built by masses with positive gravity only and repels each body with negative gravity.
Image detection and separation on Tautenburg Schmidt plates with the ASAG program package
Authors: Lange M. , Richter G.M. , Scholz R.‐D. 
Published: July 2007

AbstractThe Babelsberg image processing system which will be used for the new automated measuring machine ASAG (Astronomisches Auswertegerät) includes as special feature an adaptive filtering technique. This technique allows a reduction of noise and the determination of the background in astronomical pictures and has already been used for the surface photometry of galaxies on Schmidt plates. For astrometric purposes a method of detecting and separating images in two‐dimensional measuring rasters was developed within the frame of the ASAG software and algorithms.
Radio signature and Hα limb features of the 1979 March 9 and 1982 July 9 flares
Authors: Aurass H. , Krüger A. , Rompolt B. , Garczynska I. , Fomichev V.V. , Chertok I.M. , Ishkov V.N. , Urbarz H. 
Published: July 2007

AbstractWe present a comprehensive compilation of data for both events. Some typical Hα limb and type IV radio spectrogram features are found to be associated. The escape of matter out of loops visible in Hα via blob ejection or loop eruption is associated with fast drift burst signatures resp. early flare continuum (FCE) emission in radio spectra and pulses in HXR. The comparison of both events reveals that the metric radio‐HXR association is essentially a matter of particle escape conditions into the corona.
Relative motions between the inner core and the Earth's mantle due to attractions of the Sun and the Moon
Authors: Jochmann H. 
Published: July 2007

AbstractThe response of the inner core motion with respect to the mantle due to the attraction of the Sun and the Moon is studied. It could be shown that some periodic constituents of polar motion and the dipole part of the geomagnetic westward drift, which correspond with astronomical nutation periods, are in accordance with the applied hypothesis of a relative precession and nutation of the inner core.
ASCHOT — Astrophysical Schmidt Orbital Telescope
Authors: Tovmasyan H.M. , Lorenz H. , Priebe A. , Richter G.M. , Schmidt K.‐H. , Khodzhayants Y.M. , Krmoyan M.N. , Isajanyan R.V. , Zakharyan A.Z. 
Published: July 2007

AbstractThe necessity for a wide‐angle UV space telescope for astrophysical investigations is outlined. Some of the main scientific goals such as full sky survey and massive study of UV emission of extragalactic and galactic objects, which may be achieved by the use of the Astrophysical Schmidt Orbital Telescope ASCHOT, are presented.The concept of the telescope design, its optical system, and its system of guidance are described. Electronic devices which may be used as detectors of UV emission in the telescope are considered. The limiting sensitivity of the telescope is estimated: it is about 24m for stellar objects at 1500 Å. The control system of the telescope is brieffy described. At the end the organizations which take part in designing and manufacturing the telescope are listed.
Small waves in UT1 caused by the inequality of the equatorial moments of inertia A and B of the Earth
Authors: Wünsch J. 
Published: July 2007

AbstractA number of semidiurnal terms in UT1 arising from the inequality of the two equatorial moments of inertia A and B of the Earth are studied. Amplitudes are given using coefficients from Vondrák (1984). The most important waves correspond to the M2, S2, N2 and K2 tidal frequencies. At present, these are below the detection limit of geodetic VLBI experiments.
Aerodynamic drag perturbations in artificial satellite nodal period
Authors: Mioc V. , Radu E. 
Published: July 2007

AbstractThe difference caused by the atmospheric drag between the nodal period of artificial satellites and the corresponding Keplerian period is analytically studied for orbits with small eccentricities. Considering various effects in the distribution of the upper atmospheric density (described by the Total Density thermospheric model) and the atmospheric rotation as well, an analytic expression for the mentioned difference is established. Some particular cases are discussed.
Speckle‐interferometry and provisional orbit of BU 738
Authors: Scardia M. , Neri R. , Grewing M. 
Published: July 2007

AbstractThree different orbits of BU 738 ‐ WDS 02189 S 3019, a close visual binary, have been proposed up to now: Finsen (1969, elliptic orbit), Finsen (1969, parabolic orbit) and Heintz (1984, elliptic). In the last few years, three micrometric observations [MS] and a single speckle‐interferometric observation [RN and MG] have been independently carried out with the ESO/GPO 38 cm astrograph and ESO/MPI 2.2 m telescope. From these measurements and a list of observations of C. E. Worley of the Naval Observatory a new provisional orbit is proposed. Whereas new observations will improve the presented solution, the validity of the first two orbits suggested by Finsen has definitively to be ruled out. The masses of the two components are estimated as MA = 1·09 MȮ and MB = 1·01MȮ, respectively.
Determination of absolute proper motions in the main meridional section of the Galaxy
Authors: Schilbach E. , Scholz R.–D. 
Published: July 2007

AbstractIn two fields of the programme of the main meridional section of the Galaxy (MEGA) the proper motions for several thousands of stars were obtained in respect to a frame of background galaxies. An average proper motion accuracy of about 6 milliarcseconds per year was achieved from an analyses of MAMA measurements of Tautenburg Schmidt plates. The tautenburg and Lick mean proper motions for stars in the same magnitude range (15 < B < 17) and in the same galactic latitude zone (40° < b < 50°) show good agreement within the error bars.
Breitenänderungen der Station Potsdam
Authors: Meinig M. 
Published: July 2007

AbstractDie Breitenbestimmungen mit dem photographischen Zenitteleskop PZT 2 des geodätisch‐astronomischen Observatoriums Potsdam, wurden für den Zeitraum von 1981‐90 analysiert mit dem Ziel, Aussagen über das Langzeitverhalten abzuleiten. Die Ausgangsdaten wurden wegen der Polbewegung korrigiert. Der Verlauf der korrigierten Breitenwerte zeigt neben einem signifikanten linearen Trend jahreszeitliche Schwankungen mit zeitlich veränderlichen Parametern. Vergleichende Untersuchungen für die tschechoslowakische Station Ondrejov führen zu ähnlichen Ergebnissen. Als Ursache für die erhaltenen Breitenänderungen könnten systematische Fehler der Eigenbewegungen der beobachteten Sterne in Frage kommen.