bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamical Simulations of Hα Emission in Algol Binaries
Authors: Ratliff Mark A. , Richards Mercedes T.
Published: July 2016

Two-dimensional hydrodynamical simulations of mass transfer in short period Algol type binaries were performed using the numerical code VH−1. This code uses the Piecewise Parabolic Method with a Lagrangian Remap. Our version of the code also accounts for radiative cooling processes. The purpose of performing the simulations was to study the Hα emission from circumstellar gas in the Algols. Using observational evidence from the literature to constrain the gas stream properties, hydrodynamical maps of the Hα emissivity in the two systems β Per (P = 2.87d) and TT Hya (P = 6.95d) were made in both Cartesian and velocity coordinates from the simulation data. The velocity maps were then compared to Doppler tomograms constructed from observed Hα line emission in these systems. Since the tomograms cannot be directly transformed to maps of emission in spatial coordinates, the simulated Cartesian maps enable us to interpret the dynamical processes which produce the features observed in the Doppler tomograms. We find that the simulations produce asymmetric accretion structures with many features similar to those found in the Doppler tomograms of Algol systems.
ASCA Observations of the Eclipsing IP XY Ari
Authors: Schlegel Eric M. , Mukai Koji , Ishida M.
Published: July 2016

We describe the ASCA observation of the eclipsing intermediate polar (IP) XY Ari (=H0253+19). This system was first discussed by Patterson & Halpern (1990, ApJ, 361, 173) as a possible IP based upon the HEAO-1 data. This system is impossible to study in the optical or ultraviolet because of the 12 mag of optical extinction associated with the molecular cloud Lynds 1457=MBM 12. The system has an orbital period of 0.2526 day and a pulse period of 208 sec. Our preliminary analysis of the ASCA data shows that the eclipse is nearly total (the precision of the background subtraction sets the limit). The eclipse ingress and egress occur very quickly, although we have not yet derived accurate numbers. There are sufficient photons that we can perform crude phase-resolved spectroscopy. The resulting spectra, each covering about 1/4 of the orbit, show that the Fe Kα line is not constant as a function of phase. A sample spectrum is reproduced below. We expect to submit a paper describing the results to the ApJ before the end of 1996.
Magnetic Torque Induced High/Low Accretion States in AM Herculis Binaries
Authors: Sparks Warren M. , Howell Steve B. , Huang Min
Published: July 2016

The AM Herculis binaries (AM Hers) have high and low accretion states. A model is proposed in which the white dwarf’s rotation acts like an angular momentum storage battery for the binary orbit. The accreted material from the Roche lobe-overflowing secondary charges up this battery, whereas the magnetic torque of the white dwarf on the secondary discharges it back into the binary’s orbit. The Roche lobe’s volume becomes alternately larger and smaller than the secondary’s volume. This alternation causes the mass flow to vary between a high and low rate.
Strong Soft X-ray Emission and High Accretion Rates in Seyfert Galaxies
Authors: Szuszkiewicz Ewa
Published: July 2016

Slim accretion disk models with high accretion rates provide a natural explanation for the strong soft X-ray emission observed in several narrow–line Seyfert 1 galaxies.
Self-Similar MHD Collimated Outflows
Authors: Trussoni E. , Sauty C. , Tsinganos K.
Published: July 2016

We present a class of steady axisymmetric MHD solutions, self-similar in the meridional direction, that are suitable to model collimated winds accelerated in the potential well of a spherical object.
On the 1994 Outbursts of GRO J1655–40
Authors: Wu Kinwah , Hunstead Richard W.
Published: July 2016

We discuss some of the issues raised by the X-ray, radio and optical observations made during the 1994 outbursts of GRO J1655–40.
The Formation of Astrophysical Jets
Authors: Livio Mario
Published: July 2016

It is assumed that the acceleration and collimation mechanisms of jets are the same in all the classes of astrophysical objects which are observed to produce jets. These classes now include: active galactic nuclei, young stellar objects, massive x-ray binaries, low mass x-ray binaries, black hole x-ray transients, symbiotic systems, planetary nebulae, and supersoft x-ray sources.

On the basis of this assumption, an attempt is made, to identify the necessary ingredients for the acceleration and collimation mechanism. It is argued that: (i) jets are produced at the center of accretion disks which are threaded by a vertical magnetic field, (ii) the production of powerful jets requires, in addition, an energy/wind source associated with the central object. Tentative explanations for the presence of jets in some classes of objects and absence in others are given. Some critical observation that can test the ideas presented in this paper are suggested.
Search for Short Timescale Structural Variation of 3C 273 at 22 GHz and 43 GHz
Authors: Mantovani F. , Valerio C. , Junor W. , McHardy I.M.
Published: July 2016

The results of VLBI observations of the quasar 3C 273, obtained during a multi-frequency campaign in late 1992 in the radio, millimeter, and X-ray bands are presented. The aim of the campaign was to test the application of the SSC (Synchrotron Self-Compton) model to 3C 273. Independent estimates are obtained through the assumption of the energy equipartition between particles and magnetic field.
Multi-Epoch VLBA Observations of γ-Ray Bright Blazars
Authors: Marchenko S.G. , Marscher A.P. , Mattox J.R. , Wehrle A.E. , Xu W.
Published: July 2016

We have investigated the sub-milliarcsecond scale structure of 41 γ-ray bright blazars with the VLBA at frequencies of 22, 43, and occasionally 8.4 GHz. All of the blazars have dominant, unresolved (less than 0.1 to 0.2 milliarcsec) cores, with the exception of 0954+556, which has no structure apparent on scales less than about 1 milliarcsec. Some have prominent jets, others show only faint secondary components or no non-core structure at all. Apparent velocities have been measured for 13 sources. These range from no detected motion to > 25c.
A Polarimetric Survey of CSS Sources at 22 GHz with the VLA
Authors: Lüdke Everton , Adornes Rosane B.
Published: July 2016

We discuss the preliminary results from radio polarization observations of 22 compact steep spectrum sources made with the VLA at 1.3 cm wavelength. We confirm that 1) the detection of a flat-spectrum synchrotron halo and a radio bridge in two CSSs, suggesting that they may be young sources, 2) CSS galaxies with two lobes of emission asymmetric to the core position show strong polarization asymmetry with the highest polarized emission arising from the component farther away from the core and 3) Source components which are nearest to the cores are generally unpolarized even at such short wavelength, suggesting that the spread in the λ2 polarization spectra is much narrower than in extended sources.
Faraday Rotation Measure Observations on the Pc-Scale: Probing the AGN Environment
Authors: Taylor G. B. , Venturi T. , Udomprasert P. S.
Published: July 2016

We present multi-frequency VLBA polarimetric observations of a small sample of quasars revealing their Faraday rotation measure (RM) structure at ~ 1 mas resolution. Two of the sources (OQ 172 and 3C 216) were chosen on the basis of high RMs seen by the VLA and single dish telescopes. A few more typical quasars (3C 273, 3C 279, 3C 345 and 3C 380) were also included in the study. In OQ 172, 3C 273, 3C 279 and 3C 380 we find high RMs (>3000 rad m−2) associated with the nuclear region. Only 1-10 mas from the nucleus the jet |RM|s in all 4 of these sources fall to less than 100 rad m−2. This RM structure may be produced by strong magnetic fields in the the narrow line region of the quasar.
Evolution of the Parsec-Scale Structures of OJ 287 and 3C 273
Authors: Ojha R. , Homan D. C. , Roberts D. H. , Wardle J. F.C.
Published: July 2016

We have obtained 15 and 22 GHz linear polarization VLBA images of a sample of strong and rapidly variable polarized sources at six epochs over one year. We observe rapid changes, in both cores and jet components, in total intensity, both with and without associated changes in polarization. Changes in the cores are probably associated with the births of new components. Images of one quasar (3C 273) and one BL Lacertae object (OJ 287) from two epochs are shown here. No significant Faraday rotation is observed at any epoch in any position in either source.
A MERLIN and VLBI Survey of Faint Compact Radio Sources
Authors: Garrett M. A. , Garrington S. T.
Published: July 2016

We have selected a field from the VLA FIRST Survey which is typical in all aspects except one: it contains a bright, but extremely compact VLBI calibrator - J1159+291. 127 unresolved FIRST sources with SFIRST ≥ 10 mJy lie within 2.5° of this calibrator. λ6 cm MERLIN observations with a resolution ~ 60 mas detect around half the sources. These detections form the basis of a sample of faint but compact radio sources which are ideally suited to follow-up VLBI observations.
A VLBI Survey of 461 Southern Flat Spectrum Sources
Authors: King E. A. , Lovell J. E. J. , Ellingsen S. P. , Costa M. E. , McCulloch P. M. , Reynolds J. E. , Jauncey D. L.
Published: July 2016

We are undertaking a 1-baseline “cuts” VLBI survey of 461 flat spectrum radio sources selected from the Parkes Catalogue.
3C 216: Is It the CSS Source with the Highest Rotation Measure?
Authors: Lüdke E. , Cotton W. D. , Sanghera H. S. , Dallacasa D.
Published: July 2016

We discuss our VLBA observations at 5 and 2.7 GHz and our MERLIN observations at 1.6 and 5 GHz. A MERLIN+VLBA image provided good starting model for self-calibration and we obtained an unprecedent image of the bent jet of 3C 216. Our observations suggest the detection of strong polarization position angle variation across the observing band. If this is due to Faraday rotation then 3C216 may have a four-figure observed rotation measure, which is unlikely to be due to errors in the polarization position angle calibration.
GPS Sources with High Peak Frequencies
Authors: Edge A. C. , Pooley Guy , Jones Mike , Grainge Keith , Saunders Richard
Published: July 2016

We 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

The 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.
Nonthermal Nuclei in 374 UGC Galaxies
Authors: Wrobel J. M. , Condon J. J. , Machalski J.
Published: July 2016

The VLA was used at 1.5-2 arcsec resolution at 20cm to search for compact continuum sources in the inner regions of 374 UGC galaxies.
Evidence for a Circumnuclear Atomic Disk and Massive Black Hole in the Hidden Quasar Cygnus A
Authors: Conway J. E.
Published: July 2016

We present evidence for a compact ( ≈ 50pc scale) rotating H ɪ disk or torus in Cygnus A, which may represent part of the structure which hides the quasar nucleus.
VLBI Observations of Intraday Variability
Authors: Gabuzda D. C. , Kochanev P. Yu. , Kollgaard R. I.
Published: July 2016

Integrated 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

Sources 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

A 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.
VLBI Observations of Gravitational Lenses
Authors: Porcas R. W.
Published: July 2016

The application of the VLBI technique to the study of gravitational lenses is described, and results from recent VLBI observations are reviewed.
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

From 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

Interstellar 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.
Two Types of Jet in Cepheus A
Authors: Hughes V. A.
Published: July 2016

The young star forming region, Cepheus A, has been monitored since 1981, and shows four new types of time-dependent events. Two of these are briefly described.
86 GHz VLBI Imaging of the SiO Masers in VX Sgr
Authors: Doeleman S. S. , Lonsdale C. J. , Greenhill L. J.
Published: July 2016

We 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

VLBI 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

We 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

A 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

Weak 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

The 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

A 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

Lunar 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.
Some Aspects of Constructing Long Ephemerides of the Sun, Major Planets and the Moon: Ephemeris AE95
Authors: Eroshkin G.I. , Glebova N.I. , Fursenko M.A. , Trubitsina A. A.
Published: July 2016

The construction of long-term numerical ephemerides of the Sun, major planets and the Moon is based essentially on the high-precision numerical solution of the problem of the motion of these bodies and polynomial representation of the data. The basis of each ephemeris is a mathematical model describing all the main features of the motions of the Sun, major planets, and Moon. Such mathematical model was first formulated for the ephemerides DE/LE and was widely applied with some variations for several national ephemeris construction. The model of the AE95 ephemeris is based on the DE200/LE200 ephemeris mathematical model. Being an ephemeris of a specific character, the AE95 ephemeris is a basis for a special edition “Supplement to the Astronomical Yearbook for 1996–2000”, issued by the Institute of the Theoretical Astronomy (ITA) (Glebova et al., 1995). This ephemeris covering the years 1960–2010 is not a long ephemeris in itself but the main principles of its construction allow one to elaborate the long-term ephemeris on an IBM PC-compatible computer. A high-precision long-term numerical integration of the motion of major bodies of the Solar System demands a choice of convenient variables and a high-precision method of the numerical integration, taking into consideration the specific features of both the problem to be solved and the computer to be utilized.
Rotational Dynamics of Janus and Epimetheus
Authors: Gozdźiewski Krzysztof
Published: July 2016

We 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

Dynamics 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

Averaging 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

We 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

Currently 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

The 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

A 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

During 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

Preliminary 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

The 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.
Hidden Manifestations of Inverse Polarity in Filaments
Authors: Filippov Boris P.
Published: July 2016

Some aspects of inverse polarity of transverse magnetic fields in filaments are presented following from their fine structure and structure of the chromosphere underneath.
Plasma Electric Field Measurements as a Diagnostic of Neutral Sheets in Prominences
Authors: Foukal P.
Published: July 2016

Measurements 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

An 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

We 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

This 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

We 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).
Filament Channels: Contrasting Their Structure in Hα and He I 1083 nm
Authors: Harvey Karen L. , Gaizauskas Victor
Published: July 2016

From a direct comparison, we find that filament channels are more easily detected in He I λ1083 than in Hλ, particularly for polar crown filaments. He I 1083 nm filament channels appear to coincide with the outer boundaries of Yohkoh/SXT X-ray cavities.
Force-Free Models of a Filament Channel in which a Filament Forms
Authors: Mackay D.H. , Gaizauskas V. , Priest E.R.
Published: July 2016

Over the years few examples of the formation of filament channels or filaments have been observed. One such example was recently seen by Gaizauskas et al. (1997). This paper constructs force-free models of the main stages of formation.
Helical Structure in an Eruptive Prominence Related to a CME (SUMER, CDS, LASCO)
Authors: Kucera T.A. , Poland A.I. , Wiik J.E. , Schmieder B. , Simnett G.
Published: July 2016

SOHO (SUMER/CDS) observed an eruptive prominence on May 1,1996, associated with a CME observed by LASCO. We investigate the physical conditions of this prominence in order to quantify velocity, temperature, and density. SUMER spectra in Si IV and O IV lines are used to obtain Doppler-shift images of the prominence. The prominence shows large-scale red and blueshifted regions, revealing a large helical structure with a global twist. In addition, fine structure analysis shows multiple components in the line profile, suggesting integration of many threads along the line-of-sight with a large dispersion of velocities (±50 km s−1).
Horizontal Expansion of Eruptive Prominences
Authors: Rompolt Bogdan
Published: July 2016

It is well known that quiescent prominences (QPs) as well as active region prominences (ARPs) occasionally undergo eruptions. The process of eruption of these prominences is caused by eruption of a huge magnetic system (HMS) associated with the prominence channel and the prominence itself (Rompolt 1984). Material of these prominences is frozen-into only a part of such a magnetic system – before as well as during the eruption. When an HMS erupts it simply lifts with it the frozen-in prominence material.

Usually during the eruption a large part of the prominence material is lifted high into the corona and/or into interplanetary space. Nevertheless, on some occasions during the eruption a significant part of the original prominence material flows down to the chromosphere (Rompolt 1990).
Radio and X-ray Investigations of Erupting Prominences
Authors: Gopalswamy N. , Hanaoka Y. , Lemen J.R.
Published: July 2016

Prominence eruption is one of the most important solar phenomenon because of the possibility of using it as proxy of geoeffective solar disturbances. In a series of investigations using Nobeyama radio observations in conjunction with Yohkoh data we have found that there is more to a prominence eruption than the simple picture portrayed by Hα observations. The extent of coronal volume associated with the eruption is much larger than the prominence. We illustrate this with several examples and discuss the implication of the results for understanding the interplanetary manifestation of coronal mass ejections.
Digital “Cartes Synoptiques de la Chromosphere Solaire et Catalogues des Filaments et des Centres d’Activite”
Authors: Coffey Helen E. , Hanchett Christine D.
Published: July 2016

Almost 70 years ago Lucien d’Azambuja published the first “Cartes Synoptiques de la Chromosphere Solaire et Catalogue des Filaments de la Couche Superieure” (d’Azambuja 1928), a compendium of reduced solar observations covering the time period March 1919–January 1920. The compiled database gives both visual and quantitative measures of solar activity beginning with Carrington rotation 876. Since then, data through 1989 have been published in succeeding Cartes Synoptiques issues. The World Data Center A (WDC-A) for Solar-Terrestrial Physics has digitized several long term solar publications, including the numerical text portion of the Cartes Synoptiques. We present an overview of this extraordinary historical solar database. WDC-A is using current technology to meet user requirements for data management, analysis and distribution, has compiled over 100 Megabytes of historical solar data and made it available over the Internet as part of a continuing data rescue effort. The data can be accessed via the World Wide Web at http://www.ngdc.noaa.gov/stp.
Application of the Telluric-Line Technique to Study Late-Type Stars for Radial-Velocity Variations
Authors: Greimel Robert , Yang Stephenson L.S.
Published: July 2016

Although the use of telluric lines as wavelength fiducials to measure radial velocities does not achieve as high a precision as other fiducial-imposition techniques, this very convenient technique can be used concurrently with other observing programs to increase the temporal sampling of target stars. We have been carrying out a program to monitor the line-profile variations of early-type non-radial pulsators at the Hα and He I 667.8-nm region. With the rather modest reciprocal dispersion of 1nm/mm and the use of a 4096-element CCD, the telluric lines in the 630-nm region are also available in the observed spectra. We decided to use these telluric lines as wavelength fiducials to monitor bright, latetype stars for radial-velocity variations. As an experiment, we have also decided to reduce the spectra using available simple IRAF tasks to see how high a velocity precision can be achieved with only minor tweaking. The precision certainly would not rival other precise techniques, but the convenience in both the observing and reduction procedure may enable more target stars to be monitored by more observers. Moreover, interesting results can still be obtained with a mere 100 m/s precision. The result for a few late-type stars which also have prior HF velocities will be presented.
Limitations of Precise Radial Velocity Measurements in Pulsating Stellar Atmospheres
Authors: Vinkó J. , Kaszás G. , Kiss L. L.
Published: July 2016

We study the velocities of specific stellar absorption lines of Cepheid-type variable stars determining line bisector velocities from newly obtained high-resolution echelle spectra. We compare these velocities with recent CORAVEL measurements of Cepheids to reveal systematic differences of 2 – 3 kms−1.
Radial-velocity Variations of Late-type Variables
Authors: Yang Stephenson L.S. , Walker Gordon A.H. , Larson Ana M.
Published: July 2016

Low-amplitude, radial-velocity variations of bright late-type stars were monitored at the 1.2-m telescope of the Dominion Astrophysical Observatory (DAO) with the hydrogen fluoride (HF) absorption-cell technique. Many of the stars appear to be semi-regular red variables (SRb and SRc) and irregular red variables (Lb). The radial-velocity amplitudes range from a few tens of meters per second to a few kilometers per second while the timescales of the variations appear to range from a few tens of days to a few hundreds of days. These irregular-looking velocities are analysed for multiperiodicities. There are also variations in the chromospheric Ca II 8662 index for a few of the variables.
Stellar Rotation and Precise Radial Velocities
Authors: Gray David F.
Published: July 2016

This paper focuses on the limitations of establishing rotation rates (to be thought of as differential radial velocities across the surface of the star) and how rotation infringes on our ability to measure precise positions of spectral lines and hence spectroscopic radial velocities.
Future Directions for Radial-Velocity Research
Authors: Latham David W.
Published: July 2016

I review the status of ground-based radial-velocity searches for extrasolar planets and speculate about the new results that can be expected in this field over the coming years. Then I review the plans for astrometric space missions and speculate about the impact that these missions will have on ground-based radial-velocity work, citing the specific examples of extra-solar planet research, the mass-luminosity relation for M dwarfs and metal-poor stars, and Galactic structure and evolution.
Recombination in Radar Meteors
Authors: Southworth Richard B.
Published: July 2016

Recombination of the Electrons in the ionized column has often been considered (see, for example, Öpik, 1955), but the uncertainties in the atomic and molecular species present and in the rate constants have made it difficult to predict. Furthermore, recombination has not been recognized in the observations, so that it has been judged to be negligible (McKinley, 1961). More recently, however, a relatively high rate constant has been found for dissociative recombination of certain molecular ions. We have now observed recombination at comparable rates in our radar meteor recordings.
Evidence from Spectra of Bright Fireballs
Authors: Ceplecha Zdeněk
Published: July 2016

Spectral data with dispersions from 11 to 94 Å/mm on 4 fireballs of actual brightness of —4 to —12 magnitude and with velocities of about 30 km/s at 70 to 80 km heights are used for studies of meteor radiation problems. Previously published analyses need revision for two main reasons: (a) the absolute values of oscillator strengths of Fe I lines from laboratory data were recently recognized to be 1 order of magnitude lower, (b) the luminous efficiency factor τ of Fe I is now much better known from several different experiments. The radiation of fireballs is found to be strongly affected by self-absorption. But if the emission curve of growth is used for correction oj the self-absorption of Fe I lines, a great discrepancy between spectral data and efficiency data for total Fe I light is found. If one assumes that the self-absorption is superposed on another effect, a decrease of the dimensions of the radiating volume with increasing lower potential E1, the spectral data on Fe I lines will be in agreement with the luminous efficiency of total Fe I meteor radiation. Formulas for emission curve of growth and Boltzmann distribution including this effect are derived. This effect is important for fireballs brighter than about —1 or — 2 magnitude, while self-absorption seems to be important even for fainter meteors. The optically thin radiation of all Fe I lines might be expected for meteors fainter than +5 magnitude. Excitation temperature of 5500° K and relaxation time of 0.02 s were found as typical values for the Fe I radiation of fireballs studied. The light of fireballs is emitted during a relatively long relaxation time, which is many orders of magnitude longer than the time necessary for spontaneous radiation of excited Fe I atoms. The dimensions of the radiating volume of Fe I gas for lines with E1 = 0 were found to be 0.3X9 m at 0 absolute magnitude and 2×60 m at —10 absolute magnitude. It ivas not possible to determine any realistic abundances of other elements due to small numbers of lines for an analysis independent of Fe I, while the Fe I curve of growth cannot be used for other elements, because the radiation originates mainly from the effective surface of the radiating volume. A general formula for meteor radiation is also derived and compared with the conventional luminosity equation.