bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-Frequency VLBA+Effelsberg Observations of 1038+528 A/B
Authors: Rioja M. J. , Porcas R. W. 
Published: July 2016

AbstractWe made a November 1995 observation of the close (33 arc sec) pair 1038+528 A,B using the VLBA+Effelsberg at 2.3 and 8.4 GHz, and the VLBA alone at 15 GHz. Our analysis of the precise astrometric separation between the core peak in A and a component ~ 1.8 mas from the core in B sheds new light on the observed changes with time and frequency.
Rotation-Measure Mapping of 3C 119
Authors: Flatters C. 
Published: July 2016

AbstractThe compact steep-spectrum source 3C 119 has been mapped using the VLBA at four frequencies spread over the 5 GHz observing band. The high rotation-measure reported at short wavelengths is found to continue unbroken beyond the depolarization wavelength indicating that 3C 119 is depolarized by an external medium.
Magnetic Field Configuration in 4C 39.25
Authors: Alberdi A. , Lara L. , Gómez J.L. , Marcaide J.M. , Pérez-Torres M.A. , Kemball A. , Leppänen K. , Marscher A.P. , Patnaik A. , Porcas R. 
Published: July 2016

AbstractWe have performed simultaneous multi-frequency polarization VLBA observations of the compact radio sources 3C 395 and 4C 39.25 which show both stationary and superluminal components in their parsec-scale structures. Those of 3C 395 have been reported elsewhere. Here we report on high resolution maps of the total intensity and polarized radio emission of 4C 39.25, trace the magnetic field configuration along the jet, and explore different possibilities for the nature of the components within the framework of the bent shocked relativistic jet model.
Detection of Parsec-Scale Circular Polarization with the VLBA
Authors: Homan D. C. , Wardle J. F.C. , Ojha R. , Roberts D. H. 
Published: July 2016

AbstractCircular polarization has been detected in 3C 279 and 3C 84 at multiple epochs, using the VLBA at 15 GHz. This is the first detection of circular polarization in a compact radio source at VLBI resolution. In the case of 3C 279 the polarization is most likely produced by the conversion of linear to circular polarization by low energy relativistic electrons in the emitting region. If this is so, the absence of Faraday rotation by the same electrons suggests that the jet consists of an electron-positron plasma.
Millimeter Continuum Monitoring of Extragalactic Radio Sources with the IRAM 30M Telescope
Authors: Ungerechts H. , Kramer C. , Lefloch B. , Leon S. , Masset F. , Moreno R. , Paubert G. , Reynaud D. , Sievers A. , Wild W. 
Published: July 2016

AbstractWe continue to determine flux densities at 3mm, 2mm, and 1.3mm wavelength for selected extragalactic sources. Light-curves for some sources now cover nearly 12 years.
The Rosat-Green Bank Sample of Intermediate BL Lac Objects
Authors: Laurent-Muehleisen S. A. , Kollgaard R. I. , Feigelson E. D. 
Published: July 2016

AbstractThe Rosat-Green Bank BL Lac sample consists of 119 objects and smoothly bridges the gap between the previously disparate subclasses of radio- and X-ray-selected objects. Further study of this sample should provide useful constraints to the unified scheme and help determine if modifications are necessary.
Very Long Baseline Polarimetry of BL Lac
Authors: Denn G. R. , Mutel R. L. 
Published: July 2016

AbstractWe have made polarization sensitive maps of BL Lac with the VLBA at 15, 22, and 43 GHz at seven epochs from 1995.42 to 1997.16. Three new superluminal components (S8, S9, and S10) have been identified, each having a unique signature in trajectory and polarization characteristics.
A Spectral Analysis of 3C 67 and 3C 190
Authors: Katz-Stone D. M. , Rudnick L. 
Published: July 2016

AbstractUsing new high resolution VLA and VLBA data and existing MERLIN data of 3C 67 and 3C 190, we find both sources have a complex spectral structure similar to larger Fanaroff-Riley type II sources. Our analysis of 3C 190 predicts either an unusually steep injection index of −0.8 and a young age, or a superposition of different age spectral components.
Maser Radiation from a Turbulent Keplerian Disk: NGC 4258
Authors: Watson W. D. , Wallin B. K. , Wyld H. W. 
Published: July 2016

AbstractCalculations are summarized for the spectral and spatial distribution of maser radiation that emerges from a turbulent Keplerian disk when viewed nearly edge-on. A close comparison is made with the refined observational data about the masing accretion disk around the presumed massive black hole at the nucleus of the galaxy NGC 4258.
SiO and H2O Masers in the Central Parsec of the Galaxy
Authors: Menten Karl M. , Reid Mark J. 
Published: July 2016

AbstractWe have discovered maser emission from SiO and H2O molecules toward a number of evolved stars within the central parsec of our Galaxy. The maser positions can be registered with milliarcsecond precision relative to the radio continuum emission of the nonthermal Galactic center source Sgr A*. Since the masing stars are prominent infrared sources, our data can be used to locate the position of Sgr A* on infrared images of the Galactic center region. Using VLBA observations it will be possible to measure proper motions of the maser stars, which can be used to put constraints on the mass distribution in the central parsec.
Multi-Frequency Monitoring of a Sample of Extragalactic Radio Sources
Authors: Mingaliev M. , Botashev A. , Stolyarov V. 
Published: July 2016

AbstractThe preliminary results of monitoring of simultaneous spectra of a sample of extragalactic sources are given. Eight sets of observations were done at the RATAN-600 radio telescope in 1995-1996 at six frequencies (0.96, 2.3, 3.9, 7.7, 11.2, and 22 GHz). The light curves as well as the variability parameters are given
An Image of a Highly Relativistic Jet from a Large Flare in the X-Ray Binary Cyg X-3
Authors: Mioduszewski A. J. , Hjellming R. M. , Rupen M. P. , Waltman E. B. , Pooley G. G. , Ghigo F. D. , Fender R. P. 
Published: July 2016

AbstractA VLBA image of the X-ray binary Cyg X-3 made two days after a 10 Jy radio flare shows a one-sided, curved jet with a size scale of ≈60 mas. This seems to indicate a jet with a velocity of ≥0.89c with a inclination of a few degrees to the line of site, and indicates that some of events where Cyg X-3 flares above 3 Jy may come from highly relativistic jets close to the line of sight.
Super-Resolution of the Radio Remnant of SN 1987A
Authors: Gaensler B. M. , Tzioumis A. K. , Manchester R. N. , Staveley-Smith L. , Reynolds J. E. , Kesteven M. J. 
Published: July 2016

AbstractThe radio remnant of SN 1987A is now of sufficient flux density that super-resolution is possible at 9 GHz. We present a sequence of images from 1992 to 1996 with a resolution of ≈ 0″.5xb, showing the continuing interaction between the expanding shock front and the surrounding axisymmetric circumstellar material.
Mitaka Correlator for the Space VLBI
Authors: Shibata K. M. , Kameno S. , Inoue M. , Kobayashi H. 
Published: July 2016

AbstractThe Mitaka correlator is an FX-type correlator with 10-station inputs, which is designed for space VLBI and will be used for VSOP mainly. We report here the capabilities of the correlator, the results of model comparisons and the preliminary results of fringe test between the satellite HALCA and Japanese ground telescopes.
HALCA Spacecraft Calibration
Authors: Kobayashi H. , Wajima K. , Murata Y. , Hirabayashi H. , Kameno S. , Kawaguchi N. , Inoue M. , Murphy D. W. ,   the international VSOP team
Published: July 2016

AbstractOn February 12, 1997 the world’s first dedicated VLBI spacecraft, HALCA, was successfully launched as the space borne element of the VSOP mission. This paper describes the calibration observations that have been undertaken so far with this spacecraft.
Estimation of the Lunar Physical Librations
Authors: Newhall X X , Williams J. G. 
Published: July 2016

AbstractThe recent long-term integration of JPL ephemeris DE403/LE403 yielded lunar physical librations covering 6000 years. A Fourier analysis of a 718-year subset of this span produced estimates of the component frequencies of the forced and free librations. A subsequent iterative least-squares estimation procedure provided precise values for phases and for time-varying amplitudes and frequencies. Two free libration modes were found; presence of a third is possible but close to the noise.
CCD Astrometry of the Solar System
Authors: Arlot J.-E. , Colas F. 
Published: July 2016

Astrometry in the solar system made more progress during the past ten years than it did during the seven or eight decades before. In fact, the development of large refractors with micrometers, and after the improvement of the photographic technique, allowed one to get very accurate positions at the end of the 19th century. After that, relatively little progress was made. Astronomers faced several difficulties: first, was the poor sensitivity of the photographic plates leading to long exposures and therefore to low accuracy for faint objects; second, was the poor quality of the catalogues of stars which depended upon a very small number of available astrometric reference stars.New receptors appeared around the 1950, such as electronic cameras or T.V. tubes. But, most of these new receptors were not interesting for astrometry, mainly because of the field of view – which was too small – and of the difficulty of using such receptors. However, the development of a new technique based upon the CCD targets changed most of the astrometric observational programs. In fact, CCD receptors were made for small fields, but the CCDs were easy to use; the images were numerical, allowing processing by computers, and the sensitivity was much more important. Because of that, the accuracy increased and relative astrometry was developed. The recent development of new catalogues, such as the Guide Star Catalogue and Tycho, permits astronomers to reduce small fields, which was not possible earlier.
Construction of Relativistic Ephemerides and Applications
Authors: Moisson X. 
Published: July 2016

AbstractThe present precision of VLBI observations for the Earth rotation, the accuracy of time measurement realised with modern atomic clocks, and the necessity to obtain precise definition of reference systems and links between them, imply that we compute in the near future more accurate ephemerides, based on general relativity theory (GRT), in accordance with the recent IAU resolutions (IAU, 1992). This paper is dedicated to the presentation of semi-analytical integration of the motion of bodies in the Solar system which completes the theories built at the Bureau des Longitudes by (Bretagnon and Francou, 1988), with some applications in the determination of coordinate time scales links.
Determination of Resonance terms using Optical Observations of Two Meteosat Satellites
Authors: Hugentobler U. , Schildknecht T. , Beutler G. 
Published: July 2016

AbstractDuring an observation campaign in winter 94/95 astrometric positions from Meteosat 4 and 5 were acquired at the Zimmerwald observatory using a CCD camera mounted in the prime focus of the 0.5 m Satellite Laser Ranging telescope. The measurements cover a time interval of four months, their precision is of the order of .The modeling of radiation pressure for the small, cylindrically shaped satellites is relatively easy and they are therefore excellent objects to probe the geopotential. The orbital parameters and the radiation pressure coefficients for the two satellites as well as the resonant coefficients C22, S22 of the geopotential were determined by a single least square adjustment procedure including all the Zimmerwald observations. The relative errors estimated for the terms C22 and S22 are of the order of 1 ÷ 3 · 10−4.
Investigations on Optical and Radio Reference Frames
Authors: Puliaev S. , Andrei A.H. 
Published: July 2016

AbstractFeatures of the systematic errors of the Carlsberg Automatic Meridian Circle (CAMC) reference frame are investigated using a secondary radio reference frame defined by a set of astrometric VLA, VLBI and submillimetric positions of radio stars, taken from the literature. The radio positions of 62 stars are compared against the corresponding CAMC positions. The systematic errors of the CAMC catalogue are found to be generally smaller than 005. The radio positions were also compared with the positions obtained with the Bordeaux Automatic Meridian Circle (BORD). It was found a good coincidence between (CAMC–Radio) and (BORD–Radio) systematic differences.
Carlsberg Positions of Planets Compared with JPL DE403
Authors: Morrison L.V. , Buontempo M.E. 
Published: July 2016

AbstractThe Carlsberg meridian telescope has made nearly 20 000 observations of outer Solar System objects since it began operation in 1984. A preliminary version of the Hipparcos catalogue has been used to refer the positions to the International Celestial Reference Frame (ICRF). The observed positions of the major planets are compared with JPL DE403 which is also referred to the ICRF. The agreement with DE403 is good, except for the declination of Jupiter where there is a systematic difference reaching 015 in 1995. The cause of this discrepancy is being investigated at JPL with recent VLBI observations of Galileo.
One - Image Poznań Astrolabe: Project and Prospects
Authors: Kurzyńska K. , Baranowski R. , Dybczyński P. A. , Gabryszewska A. , Lehmann M. 
Published: July 2016

AbstractA classical astrolabe has been modernised and reconstructed into a new fully automatic instrument equipped with a CCD camera and allowing observations at two different zenith distances: 45° and 60°, respectively. The new instrument permits observations of objects fainter than those observable with the classical instrument. The work on the project is fairly advanced and regular observations are expected to begin in the nearest future. The paper reports results of the first observations and plans for the near future.
Magnetic Fields in Filaments
Authors: Démoulin P. 
Published: July 2016

AbstractFilaments are present in highly non-potential magnetic configurations. On one hand, the complexity of modeling such 3-D configurations makes a useful comparison between observations and models difficult. On the other hand such highly sheared regions are more interesting and challenging for understanding eruptive phenomena like flares and coronal mass ejections. Fortunately, the presence of cold plasma allows us to measure the magnetic field inside prominences. Together with photospheric field measurements and other morphological observations, these provide a large set of puzzling constraints for plausible models of the magnetic configurations. Models are reviewed in the framework of present observational constraints with the aim to clarify a piece of the mystery which surrounds the magnetic configuration of filaments.
Latitudinal Variations of Line-of-Sight Velocity Oscillations in the Photosphere, Chromosphere and Prominences
Authors: Mashnich G.P. , Bashkirtsev V.S. 
Published: July 2016

AbstractBy studying line-of-sight velocity time variations in prominences, we found that velocity oscillations with a period over 40 min have a reasonably well-marked dependence of the period length with heliolatitude. Simultaneous observations of line-of-sight velocities in the photosphere and chromosphere showed that quasi-hourly oscillation periods at these levels in the solar atmosphere and in prominences have a similar latitudinal behavior.
Nonlinear Waves in Force-Free Fibrils
Authors: Zhugzhda Y.D. , Nakariakov V.M. 
Published: July 2016

AbstractKorteweg-de Vries equations for slow body and torsional weakly nonlinear Alfvén waves in twisted magnetic flux tubes are derived. Slow body solitons appear as a narrowing of the tube in a low β plasma and widening of the tube, when β ≫ 1. Alfvén torsional solitons appear as a widening (β > 1) and narrowing (β < 1) of the tube, where there is a local increase of tube twisting. Two scenarios of nonlinear dissipation of strongly nonlinear waves in twisted flux tubes are proposed.
SUMER/SOHO Filament Observations in Selected Lyman Lines
Authors: Schmieder B. , Kucera T. , Heinzel P. , Vial J.-C. 
Published: July 2016

AbstractOn September 21, 1996 a filament located in a region close to an enhanced network was observed with the SOHO SUMER and CDS instruments. Four Lyman lines have been detected (Lδ, Lϵ, L-6, L-7) by SUMER in the raster mode. We have corrected the spectral data for flatfield and destreching and made wavelength and absolute intensity calibrations. In all these lines we detect a central absorption and an asymmetry in the intensity of the two peaks. Preliminary NLTE computations indicate that these Lyman profiles and their absolute intensities can be reproduced with the existing models provided that we take into account a prominence-corona transition region (PCTR).
Prominence-like Clouds Near HK Aqr
Authors: van den Oord G.H.J. , Byrne P.B. , Eibe M.T. 
Published: July 2016

AbstractA time series of Hα spectra of the rapidly rotating star HK Aqr has been analyzed. Evidence is found for the presence of cool clouds which are in co-rotation with the star. The cloud velocities, as derived from the clouds’ absorption features, can be used to put constraints on the clouds’ co-latitudes and their distances from the star using a so-called visibility diagram. For HK Aqr most clouds are at distances of 2–3 stellar radii and do not extend beyond the co-rotation radius. By using a simple radiative transfer model, we demonstrate that for most stars the presence of clouds affects the whole Hα profile and does not result in discrete absorptions. Only clouds near rapidly rotating stars, with an inclination close to 90°, will cause discrete absorption features. The cool cloud plasma can form when a temperature inversion is created at the apex of a stellar-sized coronal loop because of reduced coronal heating at large distances from the star. It is likely that the cloud condensations are related to inverse polarity filaments because, near rapidly rotating stars, the axial current in normal polarity filaments decreases with height and has to change sign at the co-rotation radius.
The Energetics of Flux-Rope Prominence Models in Axially Symmetric Systems
Authors: Lin J. , Forbes T.G. , Isenberg P.A. , Démoulin P. 
Published: July 2016

AbstractWe analyze a prominence model containing a flux rope which is completely detached from the photosphere. The maximum magnetic energy which can be stored in the configuration does not exceed the open-energy limit proposed by Aly and Sturrock. However, a loss of ideal-MHD equilibrium can occur and create a current sheet which is likely to undergo rapid reconnection.
Prominence Disappearance Related to CMEs
Authors: Hiei E. 
Published: July 2016

AbstractDB (disparition brusque) events are associated with dynamic phenomena such as a CME, a flare, brightening of a soft X-ray arcade, and soft X-ray dimming, and probably a change of the coronal magnetic field on a large scale. The DB event observed on January 16, 1993 identified with a CME occurred on the solar disk.
CMEs and Prominences and their Evolution Over the Solar Cycle
Authors: Webb David F. 
Published: July 2016

AbstractCoronal mass ejections (CMEs) are an important aspect of coronal and interplanetary dynamics. They cause large geomagnetic storms and can drive transient interplanetary shocks, which in turn are a key source of energetic particle events. However, our knowledge of the origins and early development of CMEs at the Sun is limited. CMEs are most frequently associated with erupting prominences and long-enduring soft X-ray arcades, but sometimes with no observed surface activity. I review some of the well determined coronal properties of CMEs and what we know about their source regions, with emphasis on the characteristics of the associated prominences and helmet streamers. One of these characteristics is that many CMEs seem to arise from multipolar magnetic structures with multiple or kinked inversion lines. I also discuss the solar-cycle dependencies of these structures, including the role that erupting prominences and CMEs may play in the ejection of magnetic flux and helicity from the Sun.
Disappearances of High-Latitude Filaments as Sources of High-Latitude CMEs
Authors: Oliver E.W. , Webb D.F. 
Published: July 2016

AbstractFrom a statistical comparison of high-latitude coronal mass ejections (CMEs) and disappearing solar filaments (DSFs), we find: (1) Beginning with the “rush to the poles”, DSFs arise at an increasing rate from the “emerging” or polar crown relative to the “true” polar crown. At maximum, these “opposite polarity” filaments are the dominant source of high-latitude DSFs. Following polarity reversal, the emergent polar crown becomes the true polar crown and the source of virtually all highlatitude DSFs. (2) At the last two solar maxima, we estimate that there were ~ 4 times as many high-latitude (≥ 60°) CMEs as high-latitude (≥ 45°) DSFs. Possible reasons for this discrepancy include the following: (a) DSFs, particularly small ones, are under-reported, (b) propagation effects, whereby radially propagating CMEs appear at higher latitudes than their underlying source regions, are more important than currently thought, or (c) some combination of these effects.
Time-Latitude Prominence and the Green Corona Distribution Over the Solar Activity Cycle
Authors: Minarovjech M. , Rybanský M. , Rušin V. 
Published: July 2016

AbstractWe present a distribution of prominences over the solar cycle activity. There are found both polar and equatorial branches of prominences that migrate in opposite directions. Prominences of the high-latitude crown migrate, starting in the minimum of the cycle, towards the poles, which they reach at the maximum of the cycle and then decay. The equatorward-migrating branch of prominences appears also in the minimum of the cycle at mid-latitudes and disappears at the end of the cycle. The distribution of the prominences is compared with a time-latitudinal distribution of the green corona. It is assumed that the polar branches in cycle 23 will reach the poles in 2002 (the north pole) and 2003 (the south one), respectively.
A New Station of Prominence Patrol Observations in Slovakia
Authors: Dorotovič I. , Lukáč B. , Pintér T. , Rybanský M. 
Published: July 2016

AbstractThe data from prominence observations provide an opportunity to study spatio-temporal distribution of prominences over a solar cycle. The Slovak Central Observatory (SCO) at Hurbanovo (South Slovakia) in cooperation with the coronal station at Lomnický Štít (Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, Slovakia) constructed a Lyot coronagraph with parameters D/f of 90/1250/3750 mm in 1996 for regular prominence patrol at Hurbanovo (112 m above sea level).The aim of this collaboration is a joint annual publication of a catalogue of the observed prominences for each year. This paper also describes the form of the catalogue. The authors would appreciate if other observational stations would join this activity. The editor of the catalogue will be the SCO at Hurbanovo.
Precise Radial Velocity Measurements with a Cassegrain Spectrograph, I: Wavelength calibration
Authors: Ilyin I. V. , Duemmler R. 
Published: July 2016

AbstractWe briefly describe the instrumental effects which affect the accuracy of the radial velocity measurements. We have implemented several methods to correct for the instability effects and improve the accuracy of the measurements. These include modifications of the observational strategy and a time-dependent wavelength solution as well as a discussion of the error of the offset from cross-correlation. These methods are applied to observations obtained with the high resolution échelle spectrograph SOFIN mounted at the Cassegrain focus of the alt-azimuth 2.56-m Nordic Optical Telescope, La Palma, Canary Islands.