bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relativistic Jets in Low Power Radio Galaxies
Authors: Giovannini G. , Arbizzani E. , Feretti L. , Venturi T. , Cotton W.D. , Lara L. , Taylor G.B. 
Published: July 2016

AbstractFrom VLBI observations of 11 FR I radio galaxies we find that: 1. parsec scale jets are relativistic; 2. 3C 264 shows a relativistic jet decelerating moving from the core to the extended lobes; 3. 3C 338 is a source with asymmetric parsec scale structure and morphological changes, implying proper motion on both sides of the source; 4. 1144+35 is an extended low power radio galaxy with an apparent superluminal motion in its parsec scale radio structure.
Multi-Frequency VLBI Observations of the GPS Source 1934–638
Authors: Tzioumis A. K. , King E. A. , Reynolds J. E. , Jauncey D. L. , Gough R. G. , Preston R. A. , Murphy D. W. , Tingay S. J. , Meier D. L. , Jones D. L. , Lovell J. E.J. , Edwards P. G. , McCulloch P. M. , Costa M. E. , Kedziora-Chudczer L. , Campbell-Wilson D. , Nicolson G. D. , Quick J. F. H. 
Published: July 2016

AbstractPKS 1934–638 is an archetypal GPS source, peaking at 1.4 GHz and exhibits almost no flux density variability. VLBI images at frequencies of .843, 2.3, 4.8, & 8.4 were made with the southern hemisphere VLBI array and they reveal that the source is a 42 mas compact double. There is no detectable change in separation over the last 20 years, yielding an upper limit of ~ 0.03c ± 0.2c on any expansion velocity. The spectral shapes of the two components are remarkably similar, despite indications of finer structure on longer baselines. Magnetic field calculations indicate fields of a few mGauss and the results are consistent with equipartition.
Milliarcsecond Structure of the Faraday Effects in 3C 147: “The CSS Prototype with Highest Rotation Measure” (Which Is Not)
Authors: Lüdke E. , Cotton W. D. , Sanghera H. S. , Dallacasa D. 
Published: July 2016

AbstractWe analyze polarization observations of 3C 147 at milliarcsecond scale which we have made with the VLBA at L, S, and C band and with the MERLIN array at K band. Several constraints placed by the observations on the physical conditions of the magnetoionic gas which produces the Faraday rotation are briefly discussed. Our data show that the Faraday rotation increases towards the VLBI core component with a maximum observed value of RM~ 4600±80 rad m−2. Such a value does not support the inclusion of 3C 147 as a source with exceedingly-high faraday rotation (SEFR), as suggested from published low-resolution observations.
PKS 1718–649, the Nearest GPS Radio Source
Authors: Jauncey D. L. , Tingay S. J. , Preston R. A. , Reynolds J. E. , Tzioumis A. K. , King E. A. , Lovell J. E. J. , McCulloch P. M. , Costa M. E. , Koekemoer A. , Tornikoski M. , Kedziora-Chudczer L. , Campbell-Wilson D. , Nicolson G. D. 
Published: July 2016

AbstractPKS 1718–649 has a classic GPS spectrum and is identified with the galaxy NGC 6328. At a distance of 56 Mpc, PKS 1718–649 becomes the nearest known GPS radio source.
NGC 1052: A Different Class of H2O Megamaser?
Authors: Diamond P. J. , Claussen M. J. , Braatz J. A. , Wilson A. S. , Henkel C. 
Published: July 2016

AbstractWe present VLBA observations of the H2O megamasers in the LINER galaxy NGC 1052. The structure we observe suggests a different origin for the masers than those seen in NGC 4258.
Imaging of the Arp 220 OH Megamasers with VLBI
Authors: Lonsdale Colin J. , Diamond P. J. , Lonsdale Carol J. , Smith H. E. 
Published: July 2016

AbstractGlobal VLBI imaging of the luminous IR galaxy Arp 220 reveals four major emission regions in the 1667 MHz line, each with complex spatial and velocity structure showing intriguing symmetries, suggestive of an AGN-related phenomenon. The continuum emission consists of about a dozen sub-mJy unresolved features which appear unrelated to the maser emission, and are interpreted as radio supernovae in an ongoing nuclear starburst.
VLBA Imaging of UX Ari
Authors: Beasley A. J. , Bastian T.S. 
Published: July 2016

AbstractWe have used the Very Long Baseline Array (VLBA) and the Very Large Array (VLA) to perform multi-wavelength radio imaging of the RS CVn active binary UX Arietis during the period November 16–21 1995. A series of strong flaring events exhibiting optically-thick spectra peaking above 100 GHz and extended source structures consistent with inter-binary emission were detected.
Sgr A* and Company—Multiwavelength Observations of Sgr A* and VLA Search for “Sgr A*’s” in LINERs
Authors: Falcke H. , Goss W. M. , Ho L. C. , Matsuo H. , Teuben P. , Wilson A. S. , Zhao J.-H. , Zylka R. 
Published: July 2016

AbstractWe report first results from a multiwavelength campaign to measure the simultaneous spectrum of Sgr A* from cm to mm wavelengths. The observations confirm that the previously detected submm-excess is not due to variability; the presence of an ultracompact component with a size of a few Schwarzschild radii is inferred. In a VLA survey of LINER galaxies, we found Sgr A*-like nuclei in one quarter of the galaxies searched, suggesting a link between those low-power AGN and the Galactic Center.
VLBA Observations of GRS 1915+105
Authors: Dhawan V. , Mirabel I. F. , Rodríguez L. F. 
Published: July 2016

AbstractDuring quasi-periodic flux variations, the core of this galactic superluminal source shows: (a) a flat radio spectrum between 13cm and 2cm; (b) elongation of the core along the axis of arcsecond-scale ejecta; (c) a time-delay of ~4 mins at 3.6cm, relative to 2cm; (d) progressively less variation of the flux at 2cm, 3.6cm & 13cm; and (e) scatter-broadening to 1.9mas at 8.4GHz (135mas at 1GHz).
ARISE - A Proposed Future Space VLBI Mission
Authors: Ulvestad J. S. , Linfield R. P. 
Published: July 2016

AbstractWe are developing a future space VLBI mission, ARISE, that would involve placing a VLBA-equivalent radio telescope in a highly elliptical Earth orbit. The telescope would operate at VLBI frequencies of 5, 22, 43, and 86 GHz, as well as being capable of single-dish operation at 60 GHz. Fringe-detection thresholds will be less than 10 mJy except at 86 GHz. Key scientific goals include dual-polarization imaging of blazars on the same physical scale as their γ-ray emission, astrophysical and astrometric studies of extragalactic water megamasers, and single-dish observations of O2.
New Observational Techniques and Precise Orbit Determination of Artificial Satellites
Authors: Schutz B. E. 
Published: July 2016

AbstractModern observational techniques using ground-based and space-based instrumentation have enabled the measurement of the distance between the instrument and satellite to better than one centimeter. Such high precision instrumentation has fostered applications with centimeter-level requirements for satellite position knowledge. The determination of the satellite position to such accuracy requires a comparable modeling of the forces experienced by the satellite, especially when classical orbit determination methods are used. Geodetic satellites, such as Lageos, in conjunction with high precision ground-based laser ranging, have been used to improve for modeling of forces experienced by the satellite. Space-based techniques, such as Global Positioning System (GPS), offer alternatives, including kinematic techniques which require no modeling of the satellite forces, or only rudimentary models. This paper will describe the various techniques and illustrate the accuracies achieved with current satellites, such as TOPEX/POSEIDON, GPS/MET and the expectations for some future satellites.
Determination of Initial Eigenorbits for Asteroids
Authors: Muinonen Karri , Milani Andrea , Bowell Edward 
Published: July 2016

AbstractWe consider initial determination of asteroid orbits in the case of small numbers of observations and short observational arcs. For asteroids having long arcs, we can assess the orbital uncertainties with the help of the covariance matrix that, in the phase space of the orbital elements, defines a set of probability ellipsoids. In initial orbit determination, because of the nonlinear characteristics and multiple solutions of the inversion problem, we cannot readily use the covariance matrix to estimate the orbital uncertainties. However, by computing the eigenvalues and eigenvectors of the formal correlation matrix (that is, by deriving the eigenorbits), we can discern the most indeterminate orbital elements. Here we solve the eigenproblem for 17 single-apparition asteroids.
Gravitational Capture to Resonance Rotation of the Early Moon in General Relativity and Gravitation
Authors: Gusev Alexander 
Published: July 2016

The capture of the Moon represents a very unique event in the history of the solar system (Singer, 1968; Goldreich et al., 1975; Goldreich, 1966). The Moon formed separately in a heliocentrical orbit similar to the Earth’s and was later captured by the Earth. The capture of the Moon defines also a severe heating event where the Earth’s kinetic energy of rotation is largely dissipated by the mechanism of tidal friction.A corrected tidal theory (Singer, 1977) leads to a dramatically different result of MacDonald’s theory (MacDonald, 1964) suggesting lunar capture from a prograde orbit.
Analysis of LLR Data by the Program System ERA
Authors: Aleshkina E.Yu. , Krasinsky G.A. , Vasilyev M.V. 
Published: July 2016

AbstractSome results of analysis of lunar ranging data of 1969–1995 are presented. A relevant dynamic theory has been constructed by numerical integration of the equations of motion of the major planets and the Moon and of lunar libration equations. To make the dynamical theory completely self-consistent an optional approach is tested in which the equations of Earth rotation are integrated simultaneously. Partial derivatives with respect to estimated parameters are also obtained by numerical integrations of variational equations. Preliminary results of evaluation of a large set of parameters involved in the lunar ranging data are presented.
New Approach to the Earth’s Rotation Problem Consistent with the General Planetary Theory
Authors: Brumberg V.A. , Ivanova T. V. 
Published: July 2016

AbstractThe equations of the translatory motion of the major planets and the Moon and the Poisson equations of the Earth’s rotation in Euler parameters are reduced to the secular system describing the evolution of the planetary and lunar orbits (independent of the Earth’s rotation) and the evolution of the Earth’s rotation (depending on the planetary and lunar evolution).
Geosynchronous Satellite Orbit Determination
Authors: Rudenko Sergei 
Published: July 2016

AbstractThe paper presents the results of the orbit determination of geosynchronous satellites derived from 1921 positional observations of a few dozens of satellites obtained at the double wide-angle astrograph DWA (D=0.4m, F=2m) of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine in 1985–1991. The observations cover the longitude range from 19°Wto 80°E. Orbital inclination of the observed objects is less than 3°. The mean values of the rms residuals are 066 in R.A. and 101 in Dec. over all processed orbital arcs.
Ideal Frame and Multi-Revolution Methods for Space Debris Dynamics
Authors: Calvo C. , Melendo B. , Palacios M. 
Published: July 2016

AbstractUsing the computational advantages offered by the formulation of orbital problems with respect to the ideal frame, with or without regularization, we consider the multi–revolution methods to obtain numerically the short and long–term propagation of the resulting debris clouds after a breakup event of an operational satellite. The problem posed and solved in this form gives high efficiency. We think that software with these features will serve two purposes: it will support studies of the hazards of space debris for operational orbital space systems and also will help to create debris analysis programs more transferable and reliable.
Semi-Analytical and Semi-Numerical Methods in Celestial Mechanics
Authors: Breiter Slawomir 
Published: July 2016

AbstractMany quite different theories and methods of celestial mechanics are referred to as semi-analytical or semi-numerical. Their common feature is the trade-off of a generality for a computational efficiency. Four main ideas behind semi-analytical theories are identified and reviewed: series contraction, analytical support of numerical integration, piecewise solutions, and numerical evaluation of action-angle variables. The role of numerical analysis tools in analytical theories is briefly discussed.
Optical-Radio Reference Ties
Authors: Kovalevsky J. 
Published: July 2016

In the course of the Hipparcos data reduction, the system of coordinates obtained is the result of complicated and partly random processes. It is therefore an arbitrary system which could not be retained. It was decided to compute a rotation ϵ at epoch (1991.25) and a time-dependent rotation ω (or spin) such that, when applied, it would be a realisation of the IAU extragalactic reference system as defined in 1991 and implemented by IERS in 1995.A working group was set up by the Hipparcos Science Team with the task to provide these rotations from all possible techniques. Actually eleven independent teams provided a solution. One can group them in four categories.1.Radio techniques included VLBI observations with the US Deep Space Network, VLBA and the European VLBI Network, and connected radio interferometers MERLIN and VLA. While VLBI provided a solution for both ϵ and ω, the other techniques allowed to get only ϵ.2.Medium and small field astrometry including the optical positions of compact sources (Hamburg and USNO), and observations with the HST which both provided solutions for ϵ only and comparisons of plates taken at large intervals of time (Bonn and Potsdam) which gave solutions for ω only.3.Star catalogues refered to galaxies: Lick Northern proper motion program, Yale Southern proper motion program, and KSZ catalogue. Yale University, ARI in Heidelberg and Kiev Observatory yielded solutions for ω.4.Comparison of Earth rotation parameters as obtained by VLBI and by a reduction of ground-based determinations with Hipparcos data (Prague Observatory) gave components of ϵ and ω in the equator.
Determination of Nutation and Precession Based on Observations with the Pulkovo Polar Tube
Authors: Kotreleva Olga V. , Naumov Vitalj A. 
Published: July 2016

AbstractSince 1953 regular observations have been carried out with the polar photographic tube (PT) of A. A. Mikhailov at Pulkovo, a fixed astrograph (D = 200 cm, F = 600 cm) which can take photographs of a circumpolar zone of 60′radius. An analysis of measured polar distances of the same 30 stars on each plate gives corrections to the adopted values of coefficients of the nutation and precession constant. Though several papers have appeared during the last decade in which VLBI and LLR observations were used for the determination of the nutation coefficients and precession constant, the results from a 40-year series of observations with the PT are of interest, because of its two-times period of the principal nutation term. The method is fully independent.
Astrometric Positions of Quasars by CCD Observations
Authors: Assafin M. , Vieira Martins R. , Andrei A.H. 
Published: July 2016

AbstractWe present results of CCD observations for 85 quasars with −80° ≤ δ ≤ +20° declination, belonging to the International Celestial Reference System (ICRS). The positions are referred to the Carlsberg Series (CAMC) and PPM catalogues. We discuss a method which allows one to obtain precise positions based only on CCD observations, on the use of the Digitized Sky Survey of ST ScI and on the Guide Star Catalogue. The results are compared with the VLBI positions.
Observations of the Association of Prominences and the Surrounding Corona
Authors: Smartt Raymond N. , Zhang Zhenda , Airapetian Vladimir S. , Kim Ira S. 
Published: July 2016

AbstractEmission-line coronal images in Fe XIV (530.3 nm) and FeX (637.5 nm) show faint enhancements at the location of quiescent prominences. Such enhancements can appear in the outer portions of a prominence, similar to the high-temperature sheath surrounding prominences as inferred from UV and EUV observations. The observational evidence supports the interpretation that this enhanced coronal emission is due to energy carried by the prominence threads and dissipated in the adjacent coronal region. Also, observed coronal loop interactions involving partial magnetic reconnection have associated Hα structures. These structures can have the appearance of an active prominence, similar to those typically observed in post flare loop systems. It appears that the association of such active prominences with the adjacent corona is fundamentally different from that of quiescent prominences. The observations indicate that these types of active prominences arise simply as a consequence of reconnection processes in the corona itself.
Are Prominences Formed by Flux Convergence?
Authors: Galsgaard K. , Longbottom A.W. 
Published: July 2016

AbstractNumerical 3D resistive MHD experiments are used to investigate the dynamical properties of a quadrupolar magnetic field, as the two dipolar regions are pushed together. A current concentration is formed between the approaching flux concentrations and, when reconnection starts, material is lifted against gravity. As it rises the material spreads out along the polarity inversion line and forms a prominence-like structure.
Solar and Stellar Dynamo Waves Under Asymptotic Investigation
Authors: Kuzanyan Kirill M. 
Published: July 2016

AbstractThe main magnetic activity of the Sun can be visualised by Maunder butterfly diagrams which represent the spatio-temporal distribution of sunspots. Besides sunspots there are other tracers of magnetic activity, like filaments and active regions, which are observable over a wider latitudinal range of the Sun. Both these phenomena allow one to consider a complete picture of solar magnetic activity, which should be explained in the framework of one relatively simple model.A kinematic αѡ-dynamo model of the magnetic field’s generation in a thin convection shell with nonuniform helicity for large dynamo numbers is considered in the framework of Parker’s migratory dynamo. The obtained asymptotic solution of equations governing the magnetic field has a form of a modulated travelling dynamo wave. This wave propagates over the most latitudes of the solar hemisphere equatorwards, and the amplitude of the magnetic field first increases and then decreases with the propagation. Over the subpolar latitudes the dynamo wave reverses, there the dynamo wave propagates polewards and decays with latitude. Butterfly diagrams are plotted and analyzed.There is an attractive opportunity to develop a more quantitatively precise model taking into account helioseismological data on differential rotation and fitting the solar observational data on the magnetic field and turbulence, analyzing the helicity and the phase shift between toroidal and poloidal components of the field.
Large-Scale Patterns of Prominences in the Global Solar Cycles During 1880–1995
Authors: Callebaut Dirk K. , Makarov Valentine I. , Tavastsherna Ksenia S. 
Published: July 2016

AbstractThe zonal distribution of prominences, their poleward migration from the sunspot zone to the poles, the polar magnetic field reversals and a correlation of the mean latitude of filament bands at minimum activity with the maximum of Wolf number in the next cycle are briefly discussed for the period 1880–1995. The need for research on the longterm latitude distribution of the prominences is emphasized. New results concerning long-term variations of the torsional oscillations of the Sun and quasi-periodic oscillations of the latitude zonal boundaries from an analysis of Hα charts (1915–1990) are given.
Reconstruction of Sun-as-Star Magnetic Field Structure and Evolution Using Filament Observations
Authors: Ponyavin Dmitri I. 
Published: July 2016

AbstractA technique is used to restore the magnetic field of the Sun viewed as star from the filament distribution seen on Hα photographs. For this purpose synoptic charts of the large-scale magnetic field reconstructed by the McIntosh method have been compared with the Sun-asstar solar magnetic field observed at Stanford. We have established a close association between the Sun-as-star magnetic field and the mean magnetic field inferred from synoptic magnetic field maps. A filtering technique was applied to find correlations between the Sun-as-star and large-scale magnetic field distributions during the course of a solar cycle. The correlations found were then used to restore the Sun-as-star magnetic field and its evolution in the late 1950s and 1960s, when such measurements of the field were not being made. A stackplot display of the inferred data reveals large-scale magnetic field organization and evolution. Patterns of the Sun-as-star magnetic field during solar cycle 19 were obtained. The proposed technique can be useful for studying the solar magnetic field structure and evolution during times with no direct observations.
Spectrographs for the Measurement of Radial Velocities
Authors: Baranne André 
Published: July 2016

AbstractIn this article I discuss the design of échelle spectrographs for the measurement of radial velocities. I consider the attainment of very high precision, and whether we can do still better than the current generation of instruments, and what problems have been resolved and what problems still remain to be solved in spectrograph design. The article makes special reference to the design principles followed in the Marseille-Geneva instrument ELODIE, for which the goal has been the measurement of stellar radial velocities of high precision using an R4 échelle grating.
A new spectrograph dedicated to precise stellar radial velocities
Authors: Bouchy F. , Connes P. , Bertaux J.L. 
Published: July 2016

AbstractThe fiber-fed echelle spectrograph EMILIE designed for the measurement of stellar radial-velocity changes is presently being laboratory-tested. Using a 204 × 408 mm grating and a 1k × 1k CCD detector, it samples about 50% of the 410−620 nm wavelength range with spectral resolution R ∼ 150 000. This spectrograph is coupled to the telescope via a single 50μm fiber, which accepts 2.7 arcsec from the sky. An automatic guiding system stabilizes the image at the entrance of the fiber. The fiber transmits alternately to the spectrograph the stellar beam and the reference beam. The same pixels of the CCD detector are used alternately for the two spectra, which requires an excellent short term stability. Hence, later on, the spectrograph will be located within a vacuum tank, with active thermal control. The instrument will be set up at the focus of the 1.52-m coudé telescope at the Observatoire de Haute-Provence (OHP) and will undertake programs of asteroseismology and detection of extrasolar-planets.
Precision versus Accuracy: some astrophysical and operational limitations
Authors: Griffin R. E. M. 
Published: July 2016

AbstractThe measurement of accurate radial velocities for A- or B-type dwarfs poses a separate category of problems: the small number of suitable lines, the wide wavelength range over which such lines are distributed, thermal broadening, rotational broadening, line distortions caused by rotating spots, spectrum variations due to obvious duplicity, and low-level velocity variations due to undetected companion spectra. Moreover, the fact that A- and B-type spectra fall into very distinct groups, each with its own sub-set of the above problems, means that it may be both difficult and unsatisfactory to specify velocity standards, since intrinsic uncertainties caused by differences in spectral type may exceed the measuring errors. The investigation summarized here into the nature and magnitude of some of these intrinsic errors employs wide spans of high-resolution, high-dispersion spectra of Sirius and Vega as ‘natural’ templates. Attention is also drawn to systematic errors which may arise (a) when modelling a cross-correlation ‘dip’ and (b) whenever a spectrum or a cross-correlation dip is measured in the unavoidable presence of another such spectrum or dip.