bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stellar populations and dust in the galaxy NGC 2976, a low‐luminosity member of the M81 group
Authors: Bronkalla W. , Notni P. , Mutter A. A.‐R. 
Published: July 2007

AbstractPhotographic UBV photometry of NGC 2976, a low‐luminosity member of the central M81 group of galaxies, is presented. Young stars in the central disk determine the optical view and the classification of this Sc(pec) galaxy. It is surrounded by a halo of an old population which contains nearly all the mass and half the luminosity of the system. This halo has some properties typical of spheroidal dwarf galaxies: an exponential brightness profile, an ellipticity trend of the isophotes typical of low‐mass systems, and mass and luminosity near the upper limit of typical dwarfs. In the central population I disk, star formation proceeds in dense associations scattered irregularly in a broad ringlike region of 1.2 kpc radius just inside the turnover of the rotation curve. This star formation episode may last since some 108 a; it is possibly triggered by gas infall from the interstellar cloud generated during encounters between other group members in the central M81 group. A direct triggering by recent encounters is excluded since NGC 2976 is undisturbed in its outer parts.
On the photographic detection of novae: a specific case in Libra
Authors: Debehogne H. 
Published: July 2007

AbstractComparing ESO GPO astrograph plates taken in September 1990 at La Silla with the Palomar Sky Survey from 1955, a nova was ostensibly discovered at α = 15h07m31s, δ = −1°44′01″.6 (equinox 1950.0). Its magnitudes in 1955 estimated from the Palomar plates are mB = 16·m9 and mR = 17·m. Finally (March 1991), it was identified as a high redshift (z ∼ 0.3) galaxy (Rafanelli, private communication) by spectroscopic means. Radio observations are requested.
Looking for a massive KeV pseudo‐scalar in gamma ray bursts
Authors: Wolf C. 
Published: July 2007

AbstractLooking for repetitive signals within a γ burst may provide evidence for a massive KeV pseudo‐scalar coupled to electromagnetism. We study the possible signatures that may occur for pseudo‐scalar electromagnetic propagation and outline possible probes to the pseudo‐scalar mass as well as its coupling to electromagnetism.
Elliptic integrals for cosmological constant cosmologies
Authors: Feige B. 
Published: July 2007

AbstractFollowing the discussion of some general properties and analytical formulae for cosmological models with non‐zero cosmological constant, we show how the elliptic integrals for comoving distance and light travel times as function of redshift can be expressed through Legendre integrals of the first and third kind, for which standard implementations are readily available. Observational properties are then illustrated for selected but typical models using the previously derived formulae.
Rapid oscillations of five stars in the spectral range A and F. I
Authors: Hildebrandt G. 
Published: July 2007

AbstractThe five stars HD 4849, HD 24712, HD 182475, HD 184552 and HD 215874 are a small group of objects enclosed in a larger observational programme for searching of rapid oscillations. They have been observed with the 50 cm ESO‐telescope at La Silla (Chile). These objects are characterized as a suspected δ Scuti‐type star, an Ap star, an A9 V star, an A1m star and an A9 III‐IV star, respectively. For the first two stars the periods, dedected by other authors, were confirmed. For HD 182475 a period of 112.3 min has been estimated. In the case of HD 184552 an oscillation with a period of 163.3 min has been found. The star HD 215874 shows unambiguously a variation with a period of 97.2 min.
Lymanα forests and the evolution of the universe
Authors: Liebscher D.‐E , Priester W. , Hoell J. 
Published: July 2007

AbstractThe Lyα forest absorption lines in the spectra of quasars are interpreted as caused by the crossings of the light beam with the walls of a bubble structure (expanding with the Hubble flow only). Then, the typical separation between the absorption lines is proportional to the mean size of the bubbles. The variable factor is the expansion rate H[z]. The Friedmann regression analysis of the observed line separations determines the density parameter ω0 and the normalized cosmological term λ0 = λc2/3H20 of the appropriate cosmological model:ω0 = 0.014 ± 0.002,λ0 = 1.080 ± 0.006.Depending on the Hubble parameter this method reveals the values of the present mean matter density pm,0 = 2.6 h2 · 10−28 kg m−3 and of the cosmological constant Λ = 3.77 h2 · 10−52 m−2 (with h = H0/(100 km/s·Mpc)). According to our analysis all models with Λ = 0 must be excluded. The curvature of space is positive. The curvature radius R0 is 3.3 times the Hubble radius (c/H0). The age t0 is 2.8 times the Hubble age (H0−1).
The 100—year periodic modulation of solar rotation
Authors: Yoshimura H. , Kambry M. A. 
Published: July 2007

AbstractA periodic long‐term modulation of the solar surface rotation with a time scale on the order of 100 years is found in the sunspot data from 1874 to 1992 obtained by combinig the Greenwich Photoheliographic Results from cycle 11 to cycle 20 analysed by Balthasar, Vázquez, and Wöhl and the Mitaka sunspot sketch data from cycle 18 to 22 of the National Astronomical Observatory of Japan which was the Tokyo Astronomical Observatory of the University of Tokyo until 1988. A new index of the solar rotationMdefined by integrating the angular momentum density over the whole surface, which we call the angular momentum surface layer density, reached a maximum at solar cycle 14, decreased to a minimum at cycle 17, and then increased to reach another maximum at cycle 21. The increase ofMmeans acceleration of the surface layer as a whole by transport of angular momentum from the deeper layer. This implies an decrease (increase) of the radial gradient of the differential rotation if the basic radial gradient of the differential rotation increases (decreaes) inward. The decrease ofMmeans deceleration of the surface layer and implies an increase (decrease) of the radial gradient. The degree of the equatorial acceleration of the surface differential rotation is also found to have undergone the same 100 year periodic modulation during the same interval, reaching a minimum at cycle 14, a maximum at cycle 17, and a minimum at cycle 21 in antiphase with the modulation ofM. Thus both radial and latitudinal gradients of the differential rotation increased and decreased in phase (in anti‐phase) if the basic radial gradient increases (decreases) inward.
Determination of proper motions for AC stars: First results
Authors: Volchkov A. A. , Kuzmin A. V. , Nesterov V. V. , Bastian U. , Röser S. 
Published: July 2007

AbstractProper motions of the stars of the Astrographic Catalogue are being derived, using the Hubble Space Telecope Guide Star Catalogue as second epoch. Results on the San Fernando and Cordoba AC zones are presented. Identification with GSC stars (i.e. determination of proper motion) was successful for 97 percent of all AC stars. Comparison of the proper motions thus derived with those of Preliminary PPM South shows that the accuracy is about 0.8 to 0.9 arcsec per century. Thus we can derive proper motions for about 4 million stars, with an accuracy higher than that of the SAO Catalogue.
Der Informationsgehalt langbelichteter Sternaufnahmen
Authors: Müller R. , Geyer E. H. 
Published: July 2007

AbstractWith this paper we present the mathematical background for a novel method for the deconvolution of longer exposed double star images, merged by seeing and other effects. This method, which was recently presentcd in a short paper (Müller and Geyer 1993) makes use of the autocorrelation of the odd function of the merged, and thus asymmetric two dimensional double star image profile. We give the mathematical evidence that digital filtering during the image processing does not influence the angular distance of the binary components, and that it can be determined independently of the brightness difference of the components. The brightness difference itself can be obtained without ambiguity, if it does not exceed 3 mag, and then the distance has been derived before. We further show that the information content of stellar images is generally less degraded by seeing effects as was previously supposed. Thus closer double stars can be resolved and photometrically deconvoluted by the method. By atmospheric disturbances, telescope guiding errors, optical distortions and silhouetting generally the stellar images on astrometric photographs of modern opto—electronic detectors are asymmetrically deformed. Therefore, the method yields also better accuracy and more adequate results for astrometry, photometry, and also astropspectroscopy.
Zum optischen Langzeitverhalten von AM Herculis I. Das Beobachtungsmaterial, die Langzeitlichtkurve und der bahninduzierte Lichtwechsel
Authors: Götz W. 
Published: July 2007

AbstractFür den veränderlichen Doppelstern AM Herculis, der den Prototyp einer Untergruppe von kataklysmischen Sternen darstellt, werden Untersuchungsergebnisse über das Langzeitverhalten mitgeteilt. Der nachfolgende Teil der Publikation bezieht sich auf das Beobachtungsmaterial, die Langzeitlichtkurve und die bahninduzierten Helligkeitsänderungen. Auf der Grundlage von 1275 photographischen Beobachtungen in B, V and U, die meisten von ihnen in B, die das Zeitintervall zwischen den Jahren 1982 und 1991 überdecken, können neue Aussagen über das allgemeine photometrische Verhalten des Sternes, dessen inaktive und angeregte Zustände sowie die gegenseitigen Beziehungen unter ihnen, die einzelnen Einflüsse der bahninduzierten Helligkeitsänderungen auf die Gesamthelligkeit und nicht zuletzt über das Farbverhalten des Sternes innerhalb der einzelnen Erscheinungen und des gesamten Zeitintervalls, das Gegenstand des zweiten Teils dieser Untersuchung ist, gemacht werden.
Zum optischen Langzeitverhalten von AM Herculis. II. Das Farbverhalten
Authors: Götz W. 
Published: July 2007

AbstractIn Ergänzung und Vervollständigung der Ergebnisse aus dem ersten Teil dieser Publikation (Götz, 1993) wurde das Langzeit‐Farbverhalten von AM Her auf der Grundlage von 138 (B — V)– und 136 (U — B)‐Farbenindizes untersucht. Die photometrischen Parameter des engen Doppelsterns und die Spektraltypen seiner Komponenten konnten abgeleitet werden. Es konnte auch gezeigt werden, daß die meisten Einflüsse, die den unterschiedlichen Farben‐Helligkeits‐Diagrammen überlagert sind, durch eine zusätzliche Lichtquelle hervorgerufen werden, die im inaktiven Zustand den stellaren Materiestrom und im aktiven Stadium das polare Emissionsgebiet charakterisiert. Das entwicklungsbedingte Verhalten dieser Erscheinungen wird in allen Farben‐Helligkeits‐Diagrammen durch typische Merkmale angezeigt.
Photometric catalogue of Shakhbazian compact groups of galaxies. II
Authors: Stoll D. , Tiersch H. , Oleak H. , Baier F. , Macgillivray H. T. 
Published: July 2007

AbstractThe second part of the photometric catalogue of Shakhbazian compact groups of galaxies contains optical and geometrical properties of another 24 groups (Shkh 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287). As in the first paper photometric data were obtained from the COSMOS/UKST catalogue of the Southern sky with δ ≤ +2°30′. The survey of compact galaxy groups by Shakhbazian, Petrosian, Baier, and Tiersch is a basis for studying dynamical processes in such groups.
Optical and X‐ray structures of galaxy clusters. I
Authors: Baier F. W. , Lima G. B. , Wipper H. , Braun M. 
Published: July 2007

AbstractThe differences between optical and X‐ray structures of galaxy clusters are discussed. We analyse in detail 7 Abell clusters. There is an increasing number of arguments in favour of different distributions of galaxies, gas, and dark matter in many clusters. We argue that most clusters present sub‐structures at least in the gaseous and galactic components and, moreover, the subclustering of different components does not always coincide. Such arguments strongly support the idea that most galaxy clusters are by far more complex systems than accepted until now and are usually not in an hydrostatic isothermal equilibrium.
On the question of radio emission of spiral galaxies in groups of galaxies
Authors: Malumian V. H. 
Published: July 2007

AbstractIt has been shown that the radio emission properties of spiral galaxies, if the other conditions are the same, are determined rather by the presence of the close neighbours than by space density of galaxies around them. The rate of occurence of radio sources and their radio luminosities among the spiral members of groups of galaxies depend on the projected seperation between them and their nearest neighbour. The shorter this seperation the higher the probability of radio emission.
Astrometric positions of comet Hale‐opp (1995 O1) in 1995
Authors: Ikbal M. A. , Irfan M. , Raharto M. , Hidayat B. 
Published: July 2007

AbstractNine positions of comet Hale‐Bopp (1995 O1), derived from the X‐Y positions on Bosscha Schmidt plates, taken between August 15 to August 22, 1995, are given.
Photometric variability of the Herbig Ae/Be star HD 200775
Authors: Sūžius J. , Sperauskas J. 
Published: July 2007

AbstractWe present results of photometric monitoring of HD 200775 in the passbands X and V of the VILGEN system obtained over the period from September 1994 to May 1995. It is shown that the star varies with a period of 10.225±0.041 days and an amplitude of 0.02 mag in X passband. The variations on the time scale of several hours and/or days are also confirmed.
Interactions of high velocity clouds with the disk of the LMC
Authors: Braun M. 
Published: July 2007

AbstractHigh‐resolution (∼1′0…2′4) IRAS maps, optical broad‐band, and narrow‐band images as well as H 1 λ 21 cm data have been used in order to analyse the environment of two large‐scale distortions (LMC 4 and DEM 268) in the disk of the Large Magellanic Cloud. This study has revealed cone‐like structures connected to DEM 268 and LMC 4 indicating high‐velocity cloud impacts as the most probable source of the formation of these two distortions. In both cases, the tip of the cone, which is a place of increased star formation, has a shape which is typical of supersonic motion of gaseous matter through a compressible medium. Expansion velocities of the cone‐like structures of about 12 km·s−1 can be derived from the H 1 λ 21 cm data. From these velocities, ages of the distortions of about 40 Myr (LMC 4) and 36 Myr (DEM 268) are estimated. The energy input for the formation of the distortions might have been provided by high velocity clouds with masses of the order of 105 M⊙ (assuming an initial velocity of 100 km·s−1 relative to the disk of the LMC).
Catalogue of Shakhbazian compact groups of galaxies. VII.
Authors: Stoll D. , Tiersch H. , Braun M. 
Published: July 2007

AbstractThe seventh part of the catalogue of Shakhbazian groups contains the positions and references of all the galaxies of the following 48 groups (north of δ > +2°30′): Shkh 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 142, 149, 150, 153, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166. For the estimation of the coordinates the Digitized Sky Survey was used.
New and misclassified Planetary Nebulae
Authors: Kohoutek L. 
Published: July 2007

AbstractAltogether 86 objects discovered in the period 1991–1994 have been accepted by the author as new PN (Table 1). In Appendices A and B to this table the lists of possible pre‐PN as well as of possible post‐PN, respectively, are given. Table 2 presents 6 misclassified objects which we suggest removing from CGPN.
Large‐scale transport of plasma in the Earth's plasma sheet: comparative analysis for adiabatic and non‐adiabatic cases
Authors: Zakharov V. E. , Meister C.‐V. 
Published: July 2007

AbstractA system of multi‐fluid MHD‐equations is used to compare adiabatic and non‐adiabatic transport of the energetic particles in the magnetospheric plasma sheet. A “slow‐flow” approximation is considered to study large‐scale transport of the anisotropic plasma consisting of energetic electrons and protons. Non‐adiabatic transport of the energetic plasma is caused by scattering of the particles in the presence of both wave turbulence and arbitrary time‐varying electric fields penetrating from the solar wind into the magnetosphere. The plasma components are devided into particle populations defined by their given initial effective values of the magnetic moment per particle. The spatial scales are also given to estimate the non‐uniformity of the geomagnetic field along the chosen mean path of a particle. The latters are used to integrate approximately the system of MHD‐equations along each of these paths. The behaviour of the magnetic moment mentioned above and of the parameter which characterizes the pitch‐angle distribution of the particles are studied self‐consistently in dependence on the intensity of non‐adiabatic scattering of the particles. It is shown that, in the inner magnetosphere, this scattering influences the particles in the same manner as pitch‐angle diffusion does. It reduces the pitch‐angle anisotropy in the plasa. The state of the plasma may be unstable in the current sheet of the magnetotail. If the initial state of the plasma does not correspond to the equilibrium one, then, in this case, scattering influences the particles so as to remove the plasma further from the equilibrium state. The coefficient of the particle diffusion across the geomagnetic field lines is evaluated. This is done by employing the Langevin approach to take the stochastic electric forces acting on the energetic particles in the turbulent plasma into account. The behaviour of the energy density of electrostatic fluctuations in the magnetosphere is estimated.
VRI photometry of the Einstein Cross Q2237+0305 at Maidanak observatory
Authors: Vakulik V. G. , Dudinov V. N. , Zheleznyak A. P. , Tsvetkova V. S. , Notni P. , Shalyapin V. N. , Artamonov B. P. 
Published: July 2007

AbstractObservations of the gravitationally lensed quasar Q2237+0305 were made with the 1.5‐meter AZT‐22 telescope at Maidanak (Uzbekistan) on 17–19 September 1995. All four components of the quasar are clearly resolved. The results of photometric measurements of the components are presented. It is confirmed that the component A again became the brightest one in the system. A noticeable change of the mutual colours of the components A and B in comparison with previous observations is detected and discussed. We cannot decide, on the basis of existing observational data, whether varying extinction or “chromatic” microlensing is the cause. Stronger, correlated colour changes in the system are probably caused by quasar variability. The dominant time scale of the microlensing‐governed brightness variations since the discovery is of the order of 10 years. A correlation between radio brightness and optical colour is found but cannot be explained.
Catalogue of Shakhbazian compact groups of galaxies. IX
Authors: Stoll D. , Tiersch H. , Cordis L. 
Published: July 2007

AbstractThe nineth part of the catalogue of Shakhbazian groups contains the positions and references of all the galaxies of the following 48 groups (north of δ < +2°30'): Shkh 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 253, 254, 255, 256, 257, 258, 259, 260, 328, 338, 339, 340, 340a. For the estimation of the coordinates the Digitized Sky Survey was used.
Search for magnetic field oscillations in a sunspot umbra
Authors: Landgraf V. 
Published: July 2007

AbstractIn order to search for oscillations in velocity and magnetic field strength within a sunspot umbra, a time series of spectra has been obtained through a circular analyzer and the Gregory‐Coudé telescope at the Observatorio del Teide, Tenerife. The velocity oscillations clearly show peaks of power at periods between 2 and 7 minutes, with a maximum at 5 minutes. The apparent variations of the magnetic field strength, however, don't exhibit significant oscillations; these fluctuations are rather produced by the influence of parasitic stray light from the surrouding quiet sun which are also visible in the measured time variations of the umbral contrast of continuum intensity.
ROSAT public PSPC observations in the Las Campanas Redshift Survey
Authors: Tucker D. L. , Hasinger G. , Lin H. 
Published: July 2007

AbstractThe Las Campanas Redshift Survey, an optically selected survey which contains 26 418 galaxy redshifts, has been correlated with “The First ROSAT Source Catalogue of Pointed Observations with the PSPC,” which contains 50 408 sources from 2876 ROSAT pointed observations. Ten matches were found. The optical spectra of most of the ten matches show weak narrow emission lines. Due to their high x‐ray luminosities, their high x‐ray‐to‐optical flux ratios, and the evidence of rapid x‐ray variability in the two brightest matches, we interpret the majority of these objects to be narrow‐line Seyfert galaxies or “hidden” active galactic nuclei. Of the ten matches, only one galaxy shows the characteristics of a bona fide starburst.
The axial angular momentum of the general circulation of the oceans
Authors: Brosche P. , Wünsch J. , Maier‐Reimer E. , Segschneider J. , Sündermann J. 
Published: July 2007

AbstractWith the Hamburg geostrophic ocean general circulation model, the temporal variation of the angular momentum of the oceans is studied. The input wind stresses consist of climatological winds plus the deviations of the actual winds 1981–1989. The motion part of the angular momenta of the two hemispheres resembles the (counter‐phase) behaviour of the corresponding atmospheric angular momentum. The dominating matter part however shows no phase shift between the hemispheres. The sum of the angular momenta of the solid Earth and the atmosphere is deduced from observations; in principle it should be inversely correlated to the oceanic angular momentum. A first attempt to recognize the correlation between these empirical data and the theoretical values is described.
Narrow‐line Seyfert 1 galaxies
Authors: Boller Th. 
Published: July 2007

AbstractThis paper summarizes the soft X‐ray properties of narrow‐line Seyfert 1 galaxies (NLS1). NLS1 have generally steeper soft X‐ray continuum slopes than Seyfert 1s with broader lines, and there exists an anticorrelation between 0.1–2.4 keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1–2.4 keV continuum slopes and Hβ FWHM > 3000 km s−1 are clearly discriminated against by nature. When simple power‐law models are fit to the data, photon indices reach values up to about 5, much higher than is usually seen in Seyfert 1s. Models with smaller mass black holes and/or higher Eddington fractions show some promise to explain the relation between the FWHM of the Hβ line and the X‐ray continuum slope. We further report evidence for persistent gaint and rapid variability in the ultrasoft narrow‐line Seyfert 1 galaxy IRAS 13224–3809. We have examined possible explanations for the gaint variability. Unusually strong relativistic effects provide a plausible explanation of the X‐ray data. Relativistic boosting effects may be relevant to understanding the strong X‐ray variability of some steep spectrum Seyferts more generally.