bluuebunny/crossref_metadata_2025_split huggingface dataset:
GPS Sources with High Peak Frequencies
Authors: Edge A. C. , Pooley Guy , Jones Mike , Grainge Keith , Saunders Richard 
Published: July 2016

AbstractWe have found two extreme GPS sources with peak frequencies of 20 and 30 GHz. The sources are both associated with X-ray bright, low redshift (z < 1) quasars. We have undertaken a search for similar sources using the Green Bank 5 GHz, NVSS 1.4 GHz surveys and follow-up observations with the Ryle Telescope at 15 GHz and the VLA up to 43 GHz.
The Two-Sided VLBI Source in the Seyfert Galaxy Mrk 231
Authors: Ulvestad J. S. , Wrobel J. M. , Carilli C. L. 
Published: July 2016

AbstractThe Seyfert 1/starburst/IR galaxy Mrk 231 (UGC 08058), at z = 0.0422, has been imaged with the VLBA at frequencies ranging from 1.4 GHz to 22 GHz. The radio image shows a triple source of total size 50 mas (30h−1 pc), with a self-absorbed central component and two detached lobes. The northern lobe, located 12h−1 pc from the core, is free-free absorbed at the lowest frequencies; there also seems to be free-free absorption in the southern component. The linear scale over which this absorption takes place is several times larger than that seen in NGC1275/3C84.The axis of the 50-mas radio source is approximately 60° from the elongation of the central component on the 1-mas scale. The spectrum of this central component becomes optically thin between 5 and 8.4 GHz, and resolves into a small triple source of size ~ 1.0h−1 pc at 15 GHz. There is no hint of a jet or other structure directly connecting this central component to the outer VLBI lobes.
VLBI Observations of Intraday Variability
Authors: Gabuzda D. C. , Kochanev P. Yu. , Kollgaard R. I. 
Published: July 2016

AbstractIntegrated VLA measurements during our 6 cm global VLBI polarization observations of the intraday variable sources 0716+714, 0917+624, and 0954+658 indicate that although there were no significant total intensity variations during the 24-hour VLBI experiment, the polarization for all three sources varied substantially. Independent polarization images made for 2–3 hour segments show that there were no variations on VLBI scales for 0716+714 or 0954+658, but that there were appreciable variations in the VLBI core of 0917+624, which correlate well with the integrated variations in the simultaneous VLA data.
Interstellar Scintillation and Intraday Variability
Authors: Rickett Barney J. 
Published: July 2016

AbstractSources that are compact enough to show intrinsic variability on times of a day or less (IDV) at cm wavelengths must also show interstellar scintillation (ISS) on similar timescales. However for many IDV sources, the variations could be entirely due to ISS, reducing the implied brightness temperatures to ~ 1013 K or less.
Evidence for Self-Similar Evolution of Gigahertz-Peaked–Spectrum Sources
Authors: Snellen I. A. G. , Schilizzi R. T. , van Langevelde H. J. , de Bruyn A. G. , Miley G. K. 
Published: July 2016

AbstractA sample of gigahertz-peaked–spectrum (GPS) sources has been selected from the Westerbork Northern Sky Survey (WENSS) at flux densities one to two orders of magnitude lower than bright GPS sources studied until now. VLBI observations on our faint sample and other brighter samples provide evidence that GPS sources evolve in a self-similar way.
Evidence of a Low-Mass Companion to AB Doradus
Authors: Guirado J. C. , Reynolds J. E. , Lestrade J.-F. , Preston R. A. , Jauncey D. L. , Jones D. L. , Tzioumis A. K. , Ferris R. H. , King E. A. , Lovell J. E. J. , McCulloch P. M. , Johnston K. J. , Kingham K. A. , Martin J. O. , White G. L. , Jones P. A. , Arenou F. , Froeschlé M. , Kovalevsky J. , Martin C. , Lindegren L. , Soderhjelm S. 
Published: July 2016

AbstractFrom the combination of VLBI phase-referenced observations and Hipparcos satellite data, we have found evidence of a low-mass object orbiting the late-type star AB Doradus. The mass of the new object is near the hydrogen burning limit and will constitute a precise point for calibrating the low end of the main sequence. This represents the first detection of a low-mass stellar companion using the VLBI technique, which could become an important tool in future searches for planets and brown dwarfs orbiting other stars.
Interstellar Scattering in the Galactic Anticenter
Authors: Lazio T. Joseph W. , Cordes James M. 
Published: July 2016

AbstractInterstellar scattering dictates the limiting resolution for many pulsars and OH masers and some extragalactic sources, a limit made more important by the advent of spacebased VLBI. Scattering observations have been biased toward the inner Galaxy, leaving largely unconstrained basic parameters such as the scattering medium’s extent in the outer Galaxy. Ionized gas at ~ 50 kpc is suggested by the appearance of H ɪ in nearby galaxies and models of low-redshift quasar absorption systems. We combine multiwavelength, VLBA observations of twelve extragalactic sources with previous scattering measurements of extragalactic sources and pulsars in the anticenter and constrain the radial extent of the scattering medium to 20 kpc, comparable to that of massive star formation. The H ɪɪ disk does not display significant flaring or warping, though this conclusion may reflect the coarse sampling.
86 GHz VLBI Imaging of the SiO Masers in VX Sgr
Authors: Doeleman S. S. , Lonsdale C. J. , Greenhill L. J. 
Published: July 2016

AbstractWe present the first 86 GHz spectral line VLBI map. Strong SiO masers in the late type star VX Sgr are mapped with a relative astrometry of 0.15 mas revealing an irregular ring of maser emission that echos structure seen at 43 GHz. A surprising feature of this map is the detection of a large (0.5 km s−1 AU−1 ) linear velocity gradient that can be interpreted as rigid rotation of the circumstellar envelope.
Spatially Resolved H2O Masers as Probes of Supersonic Turbulence
Authors: Strelnitski V. S. , Alexander J. , Moran J. M. , Reid M. J. 
Published: July 2016

AbstractVLBI of the H2O maser sources associated with outflows from young stars reveals, besides the regular velocity component (expansion and rotation), a random component suggestive of highly supersonic turbulence generated by the interaction of the star’s jets with the quiescent ambient gas. Our analysis of the geometry and velocity statistics in Sgr B2(M)–H2O demonstrates low fractal dimension of the turbulence and strong deviations of the velocity increments from Gaussian statistics—both indicating strong intermittency of the turbulent energy dissipation. These properties are discussed, along with the two-point velocity scaling law, and compared with the related properties of incompressible turbulence.
Determining Motions and Birthplaces of Pulsars through VLBI Astrometry
Authors: Galama T. J. , Van Paradijs J. , van den Heuvel E. P. J. , de Bruyn A. G. , Campbell R. M. , Vermeulen R. C. , Lestrade J.-F. , Verbunt F. , Schilizzi R. T. 
Published: July 2016

AbstractWe present first results of global VLBI astrometric pulsar parallax and proper motion measurements (phase-reference). The aim is to obtain information on pulsar motions and pulsar birthplaces. Proper motions could provide answers to questions like: How large are pulsar velocities at birth? How are these velocities produced and what is the final galactic pulsar distribution? Identification of birthplaces (with, e.g., an OB-association) provides information on the pulsar progenitor population (the fraction of pulsars born in binaries; the mass range of the progenitors etc.). We have a first epoch on three pulsars, selected on the basis of age (young < 3 Myr), flux density (relatively strong) and presence in the solar neighborhood (d < 3 kpc). Gating increases the SNR by typically a factor of 5.
Space VLBI Assistance Software—A New Version
Authors: Frey S. , Fejes I. , Heitler G. , Noszticzius I. , Paragi Z. 
Published: July 2016

AbstractA new version of the Space VLBI Assistance Software (SPAS) developed at the FÖMI Satellite Geodetic Observatory (Penc, Hungary) is described. SPAS version 2.0 will be a useful software tool for proposal preparation in response to the second Announcement of Opportunity of the VSOP satellite.
Improving Mark III Correlator Models After Correlation
Authors: Beasley A. J. , Alef W. 
Published: July 2016

AbstractWeak objects such as stars can only be mapped with VLBI using phase-referencing techniques. Phase-reference mapping is highly sensitive to imperfect interferometer delay models, and therefore cannot generally be performed on data from MKIII correlators for source separations of more than a few minutes of arc. An AIPS task has been developed to replace the correlator model in a UV data set with the VLBA correlator model (CALC 8.0). It is mainly intended for MKIII data which was read into AIPS via the task MK3IN, but can also be used to improve the precision of phase-reference mapping of VLBA data by correcting wrong apriori geometric information. A second task can replace the atmospheric model used in the correlator with measured values and an improved mapping function.
High Resolution Imaging of Compact Radio Sources by Gridding with Regularization
Authors: Likhachev S. F. , Hjellming R. M. 
Published: July 2016

AbstractThe problem of VLBI image reconstruction is a classical example of an ill-posed problem. A new procedure of gridding with regularization has been developed. This procedure was used in traditional methods (CLEAN, Hybrid) to improve the quality of compact radio source images. A few sources (GRO J1655–40, RY Scuti and Cyg X-1), observed with the VLA and VLBA, were processed with this procedure.
Reference Systems
Authors: Fukushima Toshio 
Published: July 2016

AbstractA reference system is a relation connecting observables and their mathematical represententions. The principle of general relativity assures that any sort of coordinate system can be used to describe physical phenomena. Thus, any reference system is only a convention. There is no absolutely true reference system. Instead, people seek for abestreference system, whose meaning may differ thus need to clarify. Taking an example from Earth rotation, we discuss how to find such a best reference system. The definition of the best system will change as scientific understandings deepen and computational environments develop. Therefore, we can not stop improving reference systems. However, when replacing an existing widely-spread system, one must take great care to minimize the inconvenience caused by its transition, especially the inconvenience which users might endure. The Standards Of Fundamental Astronomy (SOFA) project being conducted by the IAU WG on Astronomical Standards has the opportunity to ease this troublesome task. The World Wide Web (WWW) will be a main device to realize the project, namely to provide working standards including reference systems to the world.
Discoveries in the Solar System
Authors: Débarbat Suzanne 
Published: July 2016

The subject of IAU Colloquium 165 and the year 1996, which is the 150th anniversary of the discovery of the planet Neptune, give the opportunity to recall facts which have led to the discovery of three new major planets in the Solar System.Five planets plus the Earth, the Sun and the Moon were the only permanent objects known in the Solar System from Antiquity up to the 17th century when Galileo (1564–1642) discovered four new bodies around Jupiter.The question of the dimensions of the Solar System and the distances of the stars soon became one of the main problems. From the parallax of Mars J.-D. Cassini (1625–1712) deduced the diameter of the Earth’s orbit and the astronomers attempted to determine the stellar parallax at six-month intervals at the Paris and Greenwich Observatories, leading Bradley (1693–1762) to the discoveries of aberration in 1726, and nutation in 1745.
Recent Progress in Analytical Modeling of the Relativistic Effects in the Lunar Motion
Authors: Nordtvedt Kenneth , Vokrouhlický David 
Published: July 2016

AbstractLunar motion serves for a number of important tests of the relativity theory. Although the final quantitative results come out from the direct numerical treatment of the lunar laser ranging data, the analytical solutions yield important keys for understanding sensitivity of the lunar motion on diverse effects. In the last few years, important relativistic phenomena, notably the equivalence principle violation and the preferred direction effects, have been reexamined using detailed Hill-Brown type theories. Surprising amplification of the former effect, indicated also from the numerical tests, has been explained by intricate coupling with the tidal deformation of the lunar orbit. Similar treatment proved that the lunar motion hides potentially a high-quality test of the preferred frame effects. In both cases, fundamental resonances of the problem cause singular amplification of the effects for particular lunar-like orbits.
Rotational Dynamics of Janus and Epimetheus
Authors: Gozdźiewski Krzysztof 
Published: July 2016

AbstractWe investigate simplified models of flat rotational motion of the coorbital satellites of Saturn, Janus and Epimetheus. We try to verify the hypothesis of chaotic rotation of the moons, caused by gravitational interaction between them. The possibility of parametric resonance in the librations of Janus is also investigated.
Numerical Simulation of the Rotational Motion of the Earth and Moon
Authors: Eroshkin G.I. , Pashkevich V.V. 
Published: July 2016

AbstractDynamics of the rotational motion of the Earth and Moon is investigated numerically. Very convenient Rodrigues-Hamilton parameters are used for high-precision numerical integration of the rotational motion equations in the post-newtonian approximation over a 400 yr time interval. The results of the numerical solution of the problem are compared with the contemporary analytical theories of the Earth’s and Moon’s rotation. The analytical theory of the Earth’s rotation is composed of the precession theory (Lieske et al., 1977), nutation theory (Souchay and Kinoshita, 1996) and geodesic nutation solution (Fukushima, 1991). The analytical theory of the Moon’s rotation consists of the so-called Cassini relations and the analytical solutions of the lunar physical libration problem (Moons, 1982), (Moons, 1984), (Pešek, 1982). The comparisons reveal residuals both of periodic and systematic character. All the secular and periodic terms representing the behavior of the residuals are interpreted as corrections to the mentioned analytical theories. In particular, the secular rate of the luni-solar inclination of the ecliptic to the equator J2000.0 (–0027, with a mean square error 0000005) is very close to its theoretical value (Williams, 1994).
Mean Orbital Motion of Geodetic Satellites and its Applications
Authors: Exertier P. , Métris G. , Bruinsma S. , Barlier F. 
Published: July 2016

AbstractAveraging methods are convenient tools for studying long-periodic variations of the motion of artificial satellites. The main lines of a semi-analytical theory of the mean motion are given. We show how, when coupled with a careful reduction of the tracking data, this theory allows to determine parameters related to the temporal variations of the Earth gravity field (e.g. the amplitude of 18.6 years tide and the secular variation of even zonal harmonics). The theory is also very useful for other applications such as mission analysis.
Orbital Instability Zones of Space Balloons
Authors: Krivov A. V. , Sokolov L.L. , Getino J. 
Published: July 2016

AbstractWe consider the motion of a spherically-symmetric balloon satellite perturbed by the Earth’s oblateness and solar radiation pressure. For equatorial satellite orbits and neglecting the Earth obliquity, the orbit-averaged equations for eccentricity and longitude of pericenter are integrable in quadratures (Krivov and Getino, 1996). The instability zone associated with the saddle separatrix in the phase space has been found and explored in depth. For semimajor axes about two Earth’s radii, and for area-to-mass ratios in the order of several tens cm2g−1, the amplitude and period of eccentricity oscillations may change nearly twofold under a small change of initial conditions or force parameters. We then restore the actual Earth obliquity of 235 and consider a spatial (non-integrable) problem. Near the saddle separatrix, a stochasticity zone appears that leads to large unpredictable eccentricity variations. The quasirandom motions of space balloons are investigated in terms of two-symbol (0-1) sequences by methods of stochastic celestial mechanics.
Ephemeris Astronomy Definitions and Constants in General Relativity
Authors: Brumberg Victor A. 
Published: July 2016

AbstractCurrently employed definitions of ephemeris astronomy and the system of astronomical constants are based on Newtonian mechanics with its absolute time and absolute space. To avoid any relativistic ambiguities in applying new IAU (1991) resolutions on reference systems (RS) and time scales one should specify the astronomical constructions and definitions of constants to make them consistent with general relativity (GRT). Such an approach is developed with the aid of the existing relativisting hierarchy of relativistic reference systems and time scales.
The ROTOR: Rotation of Frames Via Representation of Systematic Differences in Terms of Spherical Functions
Authors: Vityazev V. V. 
Published: July 2016

AbstractThe paper presents a method to derive rotational angles between two reference frames from the systematic differences represented in terms of spherical functions – hereafter referred to as the ROTOR (ROTation by Orthogonal Representation). It is shown that the ROTOR is preferable over the least-squares technique since it (a) takes into account only the harmonics which correspond to rotation, (b) tests them for pure rotation, and (c) discovers the existence of quasirotational terms which may smear rotation. Due to these properties the ROTOR yields realistic results even in the case when the observational data contain not only noise but other systematic terms that have nothing to do with rotation. Numerical experiments with the FK5 and three catalogs of radio sources are described.
Star Cross-Identification in Big Catalogs with Significant EPOCH Difference and without proper Motions
Authors: Yagudin L.I. 
Published: July 2016

AbstractA classical task of cross-identification of stars taken from different catalogs becomes a non-trivial one in a case of very big catalogs with significant epoch difference and without proper motions. Some new concepts for this problem solution are proposed here. The method discussed was applied for the Guide Star Catalog with the Astrographic Catalogue identification. About 4.3 million stars were identified in both catalogs.
Dynamics and Fine Structures in Quiescent Prominences (MSDP/Pic du Midi, SOHO/SUMER and CDS)
Authors: Li Kejun , Malherbe J.-M. , Wiik J.E. , Schmieder B. , Roudier Th. , Kucera T. , Poland A. 
Published: July 2016

AbstractDuring the June 1996 campaign using the MSDP spectrograph at Pic du Midi and SUMER/CDS (JOP 12) on board SOHO, quiescent prominences were observed. We present observations and physical quantities of the June 5 prominence. Doppler shifts, temperatures and electron densities of fine structures were deduced from Hα data.
Small-Scale Structure in Loops and Prominence Threads
Authors: Rudawy P. , Madjarska M.S. 
Published: July 2016

AbstractPreliminary results of the morphology of prominence fine structure are presented. Long time series of three post–flare loops, a spray and an eruptive prominence were digitalized and analyzed. The length-to-width ratio of the blobs was determined and, in some threads, a continuous movement of separate blobs of matter was detected.
A Large Filament and Flares in Active Region NOAA 5669 on September 2, 1989
Authors: Porfir’eva G.A. , Yakunina G.V. , Mouradian Z. 
Published: July 2016

AbstractThe behaviour of extended filaments in the vicinity of a new emerging magnetic flux site has been investigated during the 2N/M5.8 flare on September 1 and several flares on September 2, 1989.
Plasma Electric Field Measurements as a Diagnostic of Neutral Sheets in Prominences
Authors: Foukal P. 
Published: July 2016

AbstractMeasurements of plasma electric fields offer, in principle, a direct test for the presence of neutral sheets in prominences. Macroscopic electric field intensities of order 1–10 V cm−1 are an essential element of MHD models of prominences containing neutral sheets. These fields should be detectable with our electrograph techniques using the high Paschen-series lines in the NIR, and the 15–9 and 16–9 transitions of H I around 10.5 μ. We discuss the upper limits of 1 V cm−1 we have achieved so far, and their implication for our ability to distinguish prominence models of the ideal-MHD type (e.g., Kippenhahn-Schluter 1957), from those fundamentally different models (e.g., Kuperus and Tandberg-Hanssen 1967, Martens and Kuin 1989) in which neutral sheets play a central role.
Observation of a Prominence Heating and the Heating Mechanism
Authors: Ofman L. , Mouradian Z. , Kucera T.A. , Poland A.I. 
Published: July 2016

AbstractAn arch-shaped prominence was observed with SUMERSOHO spectrometer on March 31–April 1, 1996. The observations were performed at three wavelengths in the Lyman continuum. Ten successive images were obtained at 41 minute time intervals. Based on the computed models of Gouttebroze-Heinzel-Vial we have determined the temperature distribution of the prominence using the intensity ratio of 876 Å and 907 Å. The observed time sequence shows that the prominence disappears by heating, i.e., ionization of hydrogen: a thermal DB. We model the heat input with the linearized MHD equations using a prescribed initial density and a broad-band spectrum of Alfvén waves and find a good qualitative agreement with observations. In the model the prominence is heated by the resonant absorption of Alfvén waves with frequencies that match the resonant condition for a particular flux tube structure that is determined by the magnetic field topology and density.
Axial Soft X-ray Brightening Associated with Hα Filaments
Authors: Solberg Frank C.R. , McAllister Alan 
Published: July 2016

AbstractWe have studied coronal soft X-ray (SXR) arcades around filament channels, as observed with the Yohkoh Soft X-ray Telescope (SXT). We have found about a dozen events (1991–1993). Comparisons with Hα filaments have revealed an association between some SXR structures and filaments. These bright thread-like SXR structures (often) appear to be parallel to and co-spatial with Hα filaments. The SXR structures are occasionally maintained for days, although transient brightening of axial structures is more common.
Solar Prominence Diagnostics
Authors: Vial J.-C. 
Published: July 2016

AbstractThis paper reviews the diagnostic techniques currently used to establish estimates of the physical properties of prominences. Most often the fine structure of prominences cannot be resolved. Because of this and the complex structures and the varied forms of prominences, it is difficult to establish definitive values for temperature, density, magnetic field, electric field, differential emission measure, mass flows, etc. Nevertheless, there are many useful techniques ranging from spectroscopic analysis to measurements of prominence oscillations. Most of the major techniques are reviewed in this paper, with examples of the results and an extensive bibliography. Special attention is paid to the potential diagnostic value of optically thick lines. Suggestions are made for further progress based on SOHO and other observations.
Prominences and Circumstellar Emission Around FK Comae Berenices: Balmer Lines Diagnostics from MUSICOS Spectra
Authors: Oliveira J.M. , Foing B.H. , Gondoin Ph. , Stempels H.C. , Beaufort T. , Le Poole R.S. , de Jong J.A. 
Published: July 2016

AbstractWe present results from the analysis of spectra of the fast rotating active giant star FK Comae Berenices. The extended emission is interpreted as arising in giant active loops and prominences. The absorption is due to a shell of cold and dense gas (like solar filaments).