bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-Dependent MHD Simulations of Jets from Accretion Discs: Stationary Solutions
Authors: Romanova M.M. , Lovelace R.V.E. , Ustyugova G.V. , Koldoba A.V. , Chechetkin V.M. 
Published: July 2016

AbstractA family of stationary solutions for magnetically driven outflows has been discovered by time-dependent, axisymmetric magnetohydrodynamic simulations of outflows from an accretion disk threaded by an inclined magnetic field. At the disk surface matter was given a small initial push with a speed less than the slow magnetosonic speed. In the simulations, the outflowing matter is observed to be accelerated by magnetic force and by centrifugal force up to velocities in excess of the fast magnetosonic speed and in excess of the escape speed from the central object.
Gaseous Disks in the Nuclei of Elliptical Galaxies
Authors: Ford H. , Tsvetanov Z. , Ferrarese L. , Kriss G. , Jaffe W. , Harms R. , Dressel L. 
Published: July 2016

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.
m = 1 Oscillations of Accretion Disks in Close Binary Systems
Authors: Okazaki Atsuo T. 
Published: July 2016

AbstractWe examine the two-dimensional structure of m = 1 modes in disks around white dwarfs in close binary systems. We find that the odd modes (warping modes) as well as even modes (eccentric modes) are confined to the outermost part of the disk. The period of the fundamental mode is of a few percent of the binary period, and is insensitive to the parity of the mode. These modes naturally explain the superhump periods of SU UMa stars.
ROSAT Observations of 4 Draconis: AM Her or Symbiotic?
Authors: Wheatley Peter J. 
Published: July 2016

AbstractI present the first X-ray observations of the red giant, 4 Draconis—thought to have an AM Her companion. I find evidence for absorption by the ionised wind of the red giant, but no sign of the soft X-ray emission typical of (high-state) AM Hers.
Beaming in Radio-Quiet AGN
Authors: Young S. , Hough J. H. , Axon D. J. , Bailey J. A. 
Published: July 2016

AbstractWe have obtained new optical spectropolarimetric data for the radio-quiet Seyfert NGC 1068, taken through apertures on the nucleus and at two positions within the ionization/scattering cone. The equivalent width of scattered broad-Hβ at these positions, is consistent with the presence of intrinsically beamed continuum radiation.
Structural Variations in the Quasar 3C 454.3
Authors: Pauliny-Toth I.I.K. 
Published: July 2016

AbstractImaging of the OVV quasar 3C 454.3 (z=0.859) shows that a new component was ejected from the core at epoch 1981 ± 1, close to the time of a major radio outburst. The component moved along a curved path with a mean apparent velocity of ~ 17c (Ho = 100 · h km s−1 Mpc−1). The motion, however, showed variations: from ~ 11c (1984–1985), to ~ 22c (1985–1988.5), then to ~ 14c (1988.5–1991.9).
VLBA Observations of 3C 120
Authors: Gómez J.L. , Marscher A.P. , Alberdi A. , Martí J.Mª. , Ibáñez J.Mª. 
Published: July 2016

AbstractWe present 1.3 cm and 7 mm VLBA observations of the radio galaxy 3C 120 at epochs November 11 and December 22, 1996. The 7 mm maps, with linear resolution of ~0.1 pc, show a very rich structure consisting of up to eight superluminal (~ 7 c) components.
CME and Ejection of Large Scale Magnetic Fields, Helical Magnetic Fields, and Intrinsically Asymmetric Jets - New Findings in AGN
Authors: Chu H. S. , Zhang F. J. , Spencer R. E. 
Published: July 2016

AbstractThe orthodox model of active galactic nuclei (AGN), as is generally accepted, is that of Rees. We have found an AGN (3C 147) which has a counter-jet much longer than the main jet. It also has an unusual sideways ejection from the nuclear region. Both of these and the 3-jet structure per se do not seem to conform with the general accepted model, and are also not explained by relativistic beaming effects. We speculate that this is due to coronal mass ejection (CME) in the accretion disk corona. Recently, we have found convincing new evidence that this is true. We have also found direct evidence of helical magnetic fields in the core region of 3C 147. These results may be of importance to the understanding of AGN.
EVN Observations of BL Lac Objects with Distorted Structures
Authors: Chariot P. , Sol H. , Vicente L. 
Published: July 2016

AbstractWe present results of observations of two BL Lac objects, 0735+178 and 0723–008, with the European VLBI Network (EVN) at 1.7 GHz. These objects have a distorted morphology, characterized by a large misalignment between their inner and outer radio structures. Our EVN observations at intermediate resolution reveal the presence of a highly curved jet in 0735+178, providing evidence for continuity of the radio emission from milliarcsecond to arcsecond scales. No indication of connecting radio structure is found in the case of 0723–008.
Compact Radio Emission in 60 µm Peaker Galaxies
Authors: Heisler C. A. , Norris R. P. , Jauncey D. L. , Reynolds J. E. , King E. A. 
Published: July 2016

AbstractWe present radio interferometric observations of a well defined sample of IRAS galaxies with warm far-infrared colors — 60 µm Peakers (60PKs). The core radio power of 60PKs is intermediate to that of “normal” Seyfert 2 galaxies and radio ellipticals, and follows the same relationship with respect to total radio emission as low and high power radio galaxies. This is consistent with the suggestion that 60PKs represent nascent radio elliptical galaxies.
VLA Imaging of Class I Methanol Masers at 7 mm with Angular Resolution
Authors: Slysh V. I. , Kogan L. 
Published: July 2016

AbstractEight Class I methanol masers were imaged at 44 GHz with A–configuration of the VLA providing angular resolution 0″.2. The images show a distribution of unresolved maser spots forming pairs in simple structure sources, and a distribution of pair clusters in complex sources. We found that the maser pairs are associated with hot, dense gas cores of sub–stellar masses. In complex sources the cores were found over the whole extent of the host molecular clouds.
PKS 0405–385 as Seen by the ISM Telescope
Authors: Kedziora-Chudczer L. L. , Walker M. A. , Jauncey D. L. , Wieringa M. H. , Reynolds J. E. , Tzioumis A. K. , Nicolson G. D. 
Published: July 2016

AbstractWe have found large amplitude intraday variability in the radio quasar PKS 0405–385 on timescales less than an hour. If intrinsic to the source, the inferred brightness temperature is TB ~ 1021 K, far exceeding the inverse Compton limit for a static synchrotron source. We argue that our data are in agreement with interstellar scintillations of a source component which is < 5μarcsec in size.
The Nature of a Homogeneous Sample of Compact Radio Sources Variable at 151 MHz
Authors: Minns A. R. , Riley J. M. , Warner P. J. , Rioja M. J. , Röttgering H. J. A. 
Published: July 2016

AbstractGlobal VLBI snapshot observations at 1.6 GHz (5 EVN + 4 VLBA) of a sample of low-frequency variable (LFV) radio sources found using the Cambridge Low Frequency Synthesis Telescope (CLFST) are presented. Variability at 151 MHz is almost certainly due to propagation effects in our Galaxy (e.g., refractive interstellar scintillation). Theory indicates that only sources with a significant fraction of their low-frequency flux coming from components with angular sizes ≲ 30 mas will show such effects. This is confirmed by the VLBI images.
Disk Structure of the H2O Maser IC 1396N
Authors: Val’tts I. E. , Slysh V. I. , Migenes V. , Umemoto T. , Furuya R. , Kawabe R. , Fomalont E. B. , Hirabayashi H. , Inoue M. 
Published: July 2016

AbstractThe VLBA map of the H2O maser IC 1396N, which was obtained during the VSOP pre-launch survey, shows an ordered position of maser spots. The maser spots are located along an almost straight line with the separation between extreme maser spots of 20 mas. The radial velocity varies along the line from by 3 km s−1. In total 9 maser features have been located on the line, all of them unresolved by the VLBA beam. This geometry is consistent with the disk model of masers. The mass of the disk is estimated between 10−7 and 10−4 M⊙, depending on the thickness and density. The disk must be supported by a central star with the mass of about 0.07 M⊙. The H2O maser in IC 1396N may be a proto-planetary disk around a low mass protostar in the process of accretion.
OH and H2O Maser Distribution in Orion KL
Authors: Horiuchi S. , Migenes V. 
Published: July 2016

AbstractIn order to study the powering source behind KL nebula, we made a map of OH and H2O masers from VLA observations of this region, and compared their spatial distribution and velocity structure with that of the SiO masers. The distribution of the OH masers consists of a multi-stream structure and seems to be related to the Hot Core molecular emission. The low velocity H2O masers may be classified as two groups: i) an inner clump of maser spots surrounding the SiO maser disc and continuum source “I”, and ii) component associated with the Hot Core represented by HDO emission peaks.
The Astronomical Low-Frequency Array (ALFA)
Authors: Jones D. L. , Weiler K. W. , Allen R. J. , Desch M. M. , Erickson W. C. , Kaiser M. L. , Kassim N. E. , Kuiper T. B. H. , Mahoney M. J. , Marsh K. A. , Perley R. A. , Preston R. A. , Stone R. G. 
Published: July 2016

AbstractThe ALFA mission is designed to map the entire sky at frequencies between approximately 0.3 and 30 MHz with angular resolution limited by interstellar and interplanetary scattering. Most of this region of the spectrum is inaccessible from the ground because of absorption and refraction by the Earth’s ionosphere. A wide range of astrophysical questions concerning solar system, galactic, and extragalactic objects could be answered with high resolution images at low frequencies, where absorption effects and coherent emission processes become important and the synchrotron lifetimes of electrons are comparable to the age of the universe.
Position Angle of the HALCA Antenna Feed
Authors: Kogan L. R. 
Published: July 2016

AbstractKnowledge of the position angle of an antenna feed is very important for polarization observations. The issue had been developed for ground based antennas but has not been considered for a orbiting antennas. We provide a calculation of the position angle of the Japanese satellite VSOP/HALCA which was successfully launched in a space VLBI mission.
On Hamiltonian Averaging Theories and Resonance
Authors: Ferraz-Mello S. 
Published: July 2016

AbstractIn this article, we review the construction of Hamiltonian perturbation theories with emphasis on Hori’s theory and its extension to the case of dynamical systems with several degrees of freedom and one resonant critical angle. The essential modification is the comparison of the series terms according to the degree of homogeneity in both and a parameter which measures the distance from the exact resonance, instead of just .
Applications of Parallel Processing to Astrodynamics
Authors: Coffey S. , Healy L. , Neal H. 
Published: July 2016

AbstractParallel processing is being used to improve the catalog of earth orbiting satellites and for problems associated with the catalog. Initial efforts centered around using SIMD parallel processors to perform debris conjunction analysis and satellite dynamics studies. More recently, the availability of cheap supercomputing processors and parallel processing software such as PVM have enabled the reutilization of existing astrodynamics software in distributed parallel processing environments. Computations once taking many days with traditional mainframes are now being performed in only a few hours. Efforts underway for the US Naval Space Command include conjunction prediction, uncorrelated target processing and a new space object catalog based on orbit determination and prediction with special perturbations methods.
Astrometry in the Future
Authors: Seidelmann P. K. 
Published: July 2016

AbstractThe introduction of the extragalactic reference frame and the availability of the Hipparcos and Tycho catalogs will have major impacts on changing the accuracy levels of astrometry in the future.There is a need for accurate densification of the reference frames down to at least 20thmagnitude. Also accurate space motions and distances will be required. The ground based observations must be supplemented by space missions. In addition to traditional positional astrometry, the scientific applications of planetary detection, distance scales, multiple star systems, mass detections, solar system motions and geodesy will be advanced by the new accuracies.
Earth Rotation in the Hipparcos Reference Frame
Authors: Vondrák J. , Ron C. , Pešek I. 
Published: July 2016

AbstractNew determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.
Determination of Some Physical Parameters of the Moon with Lunar Laser Ranging Data
Authors: Wenjing Jin , Jinling Li 
Published: July 2016

AbstractInformation about the structure of lunar interior and evolution could be obtained from measurements of lunar free librations, gravitational field, dissipation etc. In this paper the precision of determining free librations from Lunar Laser Ranging (LLR) data are estimated. Using the observing data from four telescopes for eighteen years, the amplitudes and phases of free librations, and ratios of the moments of inertia of the Moon were determined.
The Ephemerides of the Inner Planets from Spacecraft Range Data and Radar Observations 1961–1995
Authors: Pitjeva E. V. 
Published: July 2016

AbstractA numerical theory of motion of the inner planets and Jupiter is presented. The numerical ephemerides were compared with the set of American and Russian radar observations of planets, obtained during 1961–1995 (nearly 60000 observations), together with range measurements of Martian landers Viking-1,-2 and Mariner-9 tracking data.The main fitted parameters were the elements of Mercury, Venus, Earth, Mars, the Astronomical Unit, the scale corrections to the reference surface of planets and variability of the gravitational constant. The parameters of Mars rotation, coordinates of Viking landers, elements and the mass of Jupiter, the masses of the three asteroids were evaluated from Viking landers observations.
Asteroid Spins: From the Very Fast to the Very Slow
Authors: Harris A. W. , Wisniewski W.Z. 
Published: July 2016

The application of CCD photometry to monitoring the light variations of very small asteroids has led to an explosion of data available, and perhaps as importantly, has made it possible to probe fainter, and hence smaller asteroids. In this paper, we review several new results from the analysis of such lightcurve data, much of it taken by the late W. Z. Wisniewski, a native of Poland who studied at Poznan University (Wisniewski et al., 1997).At the time of the last close pass of the asteroid 4179 Toutatis by the Earth in 1992, it became apparent from radar observations that the asteroid was in a bizarre rotation state, and that the rotation rate was extremely slow. Harris (1994), re-evaluating the work by Burns and Safronov (1973) found that very small and slowly rotating asteroids can have a time scale of damping into a principal-axis rotation state which is long compared to their expected collisional lifetime, or for that matter, the age of the solar system:
Long term Evolution of Earth Orbiting Debris
Authors: Rossi A. 
Published: July 2016

AbstractThe space environment is presently dominated by man-made debris, for particles larger than 1 mg. A comprehensive survey of the debris population from 1 mg to the larger sizes in view of the recent data from radar and optical observations, and from the analysis of materials retrived from space is given.A brief description of the major source and sink mechanisms acting on the debris population is given, along with a very short introduction to the two models for the long term evolution developed by the group in Pisa in the last years.The results of the long term evolution analysis are presented in some detail. A likely scenario of the future space activities leads to a large growth of mmsize particles due to several catastrophic collisions. The simulation highlights the necessity of more realistic explosion models, since the current ones overestimate the 10 cm-sized fragments.An enlarged version of this paper can be found at the CNUCE Spaceflight Dynamics Group Web site: http://apollo.cnuce.cnr.it/~rossi/homerossi.html.
Ita-Crao Minor Planet Survey: Results and Prospects
Authors: Chernykh N. S. , Sokolsky A.G. 
Published: July 2016

AbstractResults of minor planet observation programme that is made jointly by the Institute of Theoretical Astronomy and the Crimean Astrophysical Observatory during three decades with the Zeiss 40-cm double astrograph at Crimea are presented. Almost all permanently numbered minor planets were observed. A catalogue of astrometrical results obtained in the course of this survey contains more than 60 thousand minor planet positions. Many thousand unnumbered asteroids were discovered, 875 of which had received permanent numbers by June of 1996.In the development of this survey programme we plan to use another Crimean telescope – the fast 64-cm telescope of Richter and Slevogt system. We intend to equip it with a CCD camera and use it for searching and observation of the Near Earth Asteroids. In the future this CCD-telescope must be a part of the national Russian network for Near Earth Asteroid (NEA) observations.
Yohkoh Observations of Coronal Structures Surrounding Dark Filaments
Authors: Uchida Yutaka 
Published: July 2016

AbstractWe describe in this paper some of the findings of the Yohkoh satellite about the coronal structure surrounding dark filaments in the pre-event and initial phases of high latitude arcade formation events. The knowledge of pre-event structure and its change is essential for the proper understanding of the arcade flaring process from the causality point of view. The wide dynamic range and high sensitivity obervations by Yohkoh allow us to look into the faint structures and their changes with the use of a faint-feature-enhancing technique in the image analysis.
Magnetic Flux Transport and Formation of Filament Channels
Authors: van Ballegooijen A.A. , Cartledge N.P. , Priest E.R. 
Published: July 2016

AbstractWe present a model of the transport of photospheric and coronal magnetic fields with the aim of explaining the observed global pattern of dextral and sinistral filaments on the quiet sun. The model is based on the assumption that the axial field in a filament channel originates in the surrounding coronal arcade. The model predicts that switchbacks in the polarity inversion line have opposite chirality on the two arms of the switchback: the higher latitude “lead” arm has sinistral (dextral) orientation in the North (South), while the lower latitude “return” arm has dextral (sinistral) orientation. This is in conflict with prominence observations which show that the chirality is the same on the two arms of a switchback. The model predicts the wrong sign of the axial field in polar crown filaments. This suggests that axial field in quiescent filaments are not produced by differential rotation acting on the surrounding coronal arcades.
Simulation Studies of Solar Prominence Formation
Authors: Choe G.S. , Cheng C.Z. 
Published: July 2016

AbstractA series of numerical simulations are presented for formation of solar prominences. We have investigated the dynamic and thermodynamic evolution of coronal plasma in response to photospheric horizontal motions. In three different setups of field configurations and footpoint motions, different types of prominences are found to be formed by thermal instability.
Ultraviolet Spectroscopy of a Coronal Mass Ejection
Authors: Ciaravella A. , Raymond J.C. , Fineschi S. , Gardner L. , Michels J. , O’Neal R. , Kohl J. , Romoli M. , Noci G. , Benna C. , Giordano S. , Antonucci E. 
Published: July 2016

AbstractA coronal mass ejection (CME) event was observed on December 23, 1996 with the Ultraviolet Coronagraph Spectrometer in both ultraviolet and visible light channels at 0.5 R⊙ over the solar limb. The CME was followed during its evolution in the bright lines of Lyα (1216Å), Lyβ (1026Å), Lyγ (972Å), C III (977Å) and the OVI doublet (1032, 1037Å) and in several weaker lines. The Lyα peak intensity shows an excursion of two orders of magnitude during the CME evolution, and blue shifts up to 0.8Å (~200 km/sec). The data provide the emission measure in the Log T range 4.0–5.5 with a 0.3 sampling. Line intensities and profiles have been measured, providing important diagnostics for a detailed study of the CME’s physical and dynamical parameters.
Filament Activity Associated With an Umbral Flare
Authors: Li Wei , Wang Jingxiu 
Published: July 2016

AbstractAn umbral flare in NOAA 6223 was observed at Huairou Solar Observing Station of Beijing Astronomical Observatory. Vigorous filament activity took place in association with this umbral flare. Several filaments formed and/or disappeared, leaving the magnetic neutral lines pointing to or rooted in the P spot in which the umbral flare occurred. We describe the observed configuration and evolution of the vector magnetic fields in the photosphere, and Doppler velocity patterns in the chromosphere during the course of the umbral flare and related filament activity.
Some comments on the design of échelle spectrographs using R2 or R4 gratings for precise radial-velocity measurements
Authors: Hearnshaw John , Rumsey Norman , Nankivell Garry 
Published: July 2016

AbstractA new fiber-fed échelle spectrograph (Hercules) is being designed for the 1-m telescope at Mt John University Observatory. The goals are to have a wavelength capability of 380 to 880 nm, covered in a single exposure on a 50-mm square CCD, to have a choice of resolving powers of 35000 or 70000 and to have no moving parts. High precision radialvelocity observations are a major but not the only goal. Designs with both R2 (blaze angle 63.4 deg) and R4 (blaze angle 76 deg) échelle gratings are being considered, in either case with a dimension of 408 mm perpendicular to the grooves.