bluuebunny/crossref_metadata_2025_split huggingface dataset:
11 . Absorption of radio waves in the ionosphere and distribution of electron concentration in the F2layer
Authors: Kazantsev A. N. 
Published: July 2016

AbstractOne of the methods used in the treatment of the results obtained during radio observations of Earth satellites consists of determining the radio-wave absorption coefficients by measurements of the electric-field strength at comparable positions.Over the territory of the Soviet Union the Earth satellites sometimes passed below the maximum of the .F2-layer, sometimes above it, and sometimes near it.
The Accuracy of Ground-Based Optical Interferometry Observations
Authors: Hutter Donald J. 
Published: July 2016

AbstractThe problem of wide-angle astrometry via interferometry is to recover the two coordinates for each star from the observed delays. In the absence of atmospheric turbulence, the geometrical delay can be defined as: dG, ij(t) ≡ dj(t) ‒ di(t) = Bij(t)·ŝ0 ‒ Cij. Here the geometrical delay is the difference between the delay line lengths di and dj that is required to equalize the effective optical paths from the star to the point of beam combination via each of two apertures i and j. Bij(t) is the baseline between the apertures, ŝ0 is the star position, and Cij is the difference between the ‘fixed’ internal optical path lengths Ci and Cj within the instrument. In principle, sufficient delay measurements would allow solution for the baseline vectors and the delay constants, as well as the positions of the stars. However, the actual situation is greatly complicated by the presence of the atmosphere and the fact that neither the delay ‘constants’ Cij nor the baseline vectors are stable over time. The design of, and the analysis of the data from, any ground-based optical interferometer must overcome all three of these effects. The design, operation, and the analysis of data from the Navy Prototype Optical Interferometer (NPOI) are presented here as examples of how to overcome the effects of the atmosphere and the instrumental instabilities in order to achieve accurate wide-angle astrometry. The status of the implementation of these techniques at the NPOI is presented.
Possible Relativistic Definitions of Parallax, Proper Motion and Radial Velocity
Authors: Klioner S. 
Published: July 2016

AbstractIt is argued that the relativistic definitions of parallax, proper motion and radial velocity consistent with an accuracy of 1 μas should be considered only within a well-defined algorithm of relativistic reduction of observational data. Such an algorithm is formulated and the corresponding definitions of astrometric parameters are discussed.
Crossing the “Yellow Void” – Spatially Resolved Spectroscopy of the Post–Red Supergiant IRC+10420
Authors: Humphreys Roberta M. , Davidson Kris , Smith Nathan 
Published: July 2016

AbstractIRC+10420 is a post–red supergiant at the empirical luminosity boundary in the HR diagram. It has now reached a stage in its blueward evolution where increasing opacity and partial ionization destabilize its atmosphere leading to rapid mass loss. Indeed, its wind is so dense that it is opaque and hides the underlying star. We have obtained HST/STIS spectroscopy with spatial resolution good enough to separate the star from its complex ejecta with numerous arcs, knots and jet-like features. The ejecta form essentially a reflection nebula, allowing us to view the star from a range of directions. The kinematics of the ejecta cannot be reconciled with existing models with either an equatorial disk or a bipolar outflow. Therefore we propose a model with a uniform spherically symmetric outflow of gas with random, asymmetric ejections superimposed. In our model, local instabilities allow for inflowing and outflowing material to coexist.
FG Sagittae
Authors: Schönberner Detlef , Jeffery C. Simon 
Published: July 2016

AbstractFG Sagittae has evolved from a hot central star of a planetary nebula to an K-type supergiant within approximately the last 100 years. The generally accepted interpretation for this redward evolution is that of a late thermal pulse during the planetary nebula stage, wherein helium burning at the surface of the electron-degenerate carbon-oxygen core is reignited. As the star expands in response to the energy released by helium burning, envelope convection digs deeper and deeper until nuclearly processed material may get dredged-up to the stellar surface. Analysing the spectra as FG Sge is evolving would then give unique information about the temporal development of mixing processes occurring inside the star that are otherwise impossible to obtain. The existing abundance analyses do not give, however, a consistent picture. Especially the question about FG Sge’s hydrogen abundance is still unsettled. We present a critical assessment of all the existing data, trying to find a self-consistent picture of the evolution of FG Sge, based on the latest evolutionary models.
Sakurai’s Object, V605 Aql and FG Sge: An Evolutionary Sequence Revealed
Authors: Lawlor Timothy M. , MacDonald James 
Published: July 2016

AbstractWe have completed a grid of stellar evolution calculations to study the behavior of the born again phenomenon. All our evolutionary sequences begin with a uniform composition 1 M⊙ star on the pre-main sequence Hayashi phase and end on the white dwarf cooling track. We find a very late thermal pulse occurs in 10 – 15 percent of cases. Our models supply an answer to the question of why the born again stars V4334 Sgr (Sakurai’s Object) and V605 Aql have a significantly shorter evolutionary time scale than the otherwise similar born again star FG Sge. Models with low convective mixing efficiency, η = 10–4, first evolve quickly to the AGB, return to the blue, and then evolve more slowly back to the AGB for a second time before finally returning to the white dwarf cooling track. The difference in evolution time scales can then be explained by proposing that Sakurai’s Object is evolving to the AGB for the first time but FG Sge has been observed during its second return to the AGB.
The β Lyrae Puzzle
Authors: Linnell A.P. 
Published: July 2016

AbstractAccurate simulation of optical wavelength CCD spectra is possible by adopting a black-body representation for the radiation characteristics of the β Lyrae accretion disk rim. Application of this model to IUE spectra shows that the anomalous system light curves, in the satellite UV, arise from a source of radiation, not included in the current model, which is visible during the phase 0.0 eclipse.
Magnetically Driven Warping and Precession of Accretion Disks: Implications for Exotic Stellar Variabilities
Authors: Lai Dong 
Published: July 2016

AbstractThe inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. These novel magnetic effects give rise to some “exotic” stellar variabilities, and may play an important role in explaining a number of puzzling behaviors related to disk accretion onto magnetic stars, such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries (including precession of jets), low-Frequency (10-50 Hz) QPO’s in low-mass X-ray binaries, and photometric variabilities of T Tauri stars.
The Later Evolution of the Contact Binaries AP Leo, AK Her, AB And and AM Leo
Authors: Li L. , Han Z. , Zhang F. 
Published: July 2016

AbstractA detailed study of the periods and light curves of binaries AK Her, AP Leo, AB And and AM Leo is presented. Based on the study of the O – C curves, we find that the period variation of each system contains several components with different frequencies, and we suggest that the periodical variations in the periods are likely influenced by different mechanisms. Based on the study of the light curve changes, we find that the light curves exhibit two kinds of variations: rapid variations and long-term variations. We investigate the physical mechanisms which may underlie the variations of the period and the light curve of each system and obtain some new conclusions. According to the characteristics of the rapid light variation in these systems, we suggest that the rapid change in the light curve is probably caused by pulsation of the common envelope, and that the mechanism(s) causing the pulsation may be mass transfer through the inner Lagrangian point L1 or its variation. Finally, the evolutionary trends of these systems are discussed, and we suggest that these systems may be progenitors of cataclysmic variables.
Variability of the Light Curves of the Close Binary GR Tauri
Authors: Yamasaki A. , Takeda M. , Yamauchi T. , Takada G. , Hattori S. 
Published: July 2016

AbstractVariability of the light curves of the short-period eclipsing binary system GR Tau (, almost-contact binary) is studied. It is found that GR Tau experienced both the state which is characterized by asymmetric light curves and the state characterized by symmetrical light curves.
Magnetic Field Evolution in Accreting White Dwarfs
Authors: Cumming Andrew 
Published: July 2016

AbstractI discuss the effect of accretion on the magnetic field of an accreting white dwarf. Whereas the magnetic fields of isolated white dwarfs are not expected to change significantly with time, I show that if an accreting white dwarf increases in mass at a rate > 1–5 × 10−10MΘ yr–1, accretion overcomes ohmic diffusion and has a significant effect on the field structure. I discuss the implications of this result for observed systems. In particular, accretion induced field evolution may provide the missing evolutionary link between the strong field, slowly accreting AM Her systems and the weak field, more rapidly accreting intermediate polars.
The Spin-Up Rate of the White Dwarf in GK Per
Authors: Mauche Christopher W. 
Published: July 2016

AbstractWe use hard X-ray light curves measured by the Chandra HETG and RXTE PCA during the late rise and plateau phases of the 2002 March–April outburst of the intermediate polar GK Per to determine that its X-ray pulse period P = 351.332 ± 0.002 s. Combined with previous X-ray and optical measurements of the spin period of the white dwarf, we find that its spin-up rate Ṗ = 0.00027 ± 0.00005 s yr−1.
High-Speed Imaging and Spectro-Polarimetry with Subaru Telescope
Authors: Sekiguchi Kazuhiro , Charles Phil , van Zyl Liza , Woodhouse Guy F. 
Published: July 2016

AbstractWe are developing a high-speed option for the Faint Object Camera and Spectrograph (FOCAS) at the Cassegrain focus of the Subaru 8.2 meter telescope at Mauna Kea, Hawaii. FOCAS has been used for direct imaging, low-dispersion multi-object spectroscopy, imaging polarimetry and spectro-polarimetry of faint objects. The high-speed option utilizes an EEV CCD47-20 with the frame transfer operation to achieve up to ~ 0.1 sec time resolution. This paper presents a summary of the expected capability and the implementation schedule.
The Spin Periods of Magnetic Cataclysmic Variables
Authors: Norton A. J. , Somerscales R. V. , Wynn G. A. 
Published: July 2016

AbstractWe have used a model of magnetic accretion to investigate the rotational equilibria of magnetic cataclysmic variables (MCVs). This has enabled us to derive a set of equilibrium spin periods as a function of orbital period and magnetic moment which we use to estimate the magnetic moments of all known intermediate polars. We further show how these equilibrium spin periods relate to the polar synchronisation condition and use these results to calculate the theoretical histogram describing the distribution of magnetic CVs as a function of Pspin/Porb. We demonstrate that this is in remarkable agreement with the observed distribution assuming that the number of systems as a function of white dwarf magnetic moment is distributed according to .
Blobby Accretion in Magnetic Cataclysmic Variables
Authors: Halevin A. V. , Andronov I. L. , Shakhovskoy N. M. , Kolesnikov S. V. , Ostrova N. I. 
Published: July 2016

AbstractThe processes of accretion of the gaseous blobs with different masses and densities onto strongly magnetized white dwarfs in the systems of polars have been modelled. We prove that shot noise in blue wavelengths represents accretion of the smaller and denser blobs than in redder wavelengths. Using combined “smooth particle hydrodynamics - drag force” model, we have predicted a shape of the accretion stream and active regions on the white dwarf surface.
Computational Models of the Accretion Stream in Polars
Authors: Cash Jennifer L. 
Published: July 2016

AbstractI present the current results of my computational modeling of the accretion stream in polars. These numerical stream models, generated using an SPH code, yield a 3-dimensional map of the gas distribution throughout the stream, including the distribution of material as it impacts the white dwarf surface. The major features of the accretion streams generated by the model code are presented as well as results of a model representing EF Eri. The prospective future development of the model is also discussed.
Modeling the radio outbursts in AE Aquarii
Authors: Venter L. A. , Meintjies P. J. 
Published: July 2016

AbstractIn this paper we model the non-thermal radio to infra-red flares from AE Aqr. In our model the non-thermal flares originate in highly magnetized (Bblob ≥ 2000 G) blobs that may be among the propeller ejected outflow. It was shown that the condition ß ≤ 1 constrains the frozen-in magnetic field in these blobs to Bblob ≥ 2000 G, which is of the same order of magnitude as the inferred polar field of the secondary. As these magnetized blobs encounter the violent mhd-propeller, processes such as reconnection, magnetic pumping, and shocks will result in continuous acceleration of electrons from (γ = 2 → 30; δ = 2.8 → 2.6) with resultant synchrotron emission. The total radio to infra-red flare spectrum was modelled in terms of such expanding magnetized synchrotron emitting blobs in various stages of their evolution from ρ = (r/r°) = 1 → 400. In terms of our model, the total integrated flux during outbursts, over the wide frequency range from 1 GHz is the result of several (~ 20) synchrotron emitting blobs observed in different stages of their evolution, resulting in a spectrum showing a peak flux of Sv ~ 148 mJy at v ~ 1805 GHz (~ 166 microns), where the spectrum changes from a typical self-absorbed Sv ∝ vα spectrum to Sv ∝ v-(δ-1)/2 spectrum, i.e. where the blobs are combined optically thin.
White Dwarfs in Magnetic Cataclysmic Variables
Authors: Shylaja B. S. 
Published: July 2016

AbstractAn attempt has been made here to seek the origin of the magnetic white dwarfs in Cataclysmic Variables. Following the suggestion made in the case of isolated white dwarfs, we look at the possibility of binaries with magnetic A type stars known as chemically peculiar stars as progenitors of MCVs. The evolution of the binary is discussed and compared with the available statistics.
Dynamo-Induced Mass-Transfer Variations in MCVs
Authors: Hessman F. V. 
Published: July 2016

AbstractThe fully convective secondary stars in short-period CVs are rapidly rotating and thus should have a characteristic global magnetic field produced by an α2-Dynamo. This field is expected to be dipole-like, with an axis lying in the orbital plane, and to rotate slowly through the mass of the star on magnetic diffusion timescales of years to decades. When one of the poles of this field is near the inner Lagrange point, the reduction in the sound speed, scale-height and possibly the density in the giant “starspot” will modulate the mass-transfer to the primary. Given the extremely high Coriolis numbers (low Rosby numbers) of CV secondaries, this is a generic mechanism which is capable of explaining the extended high- and low-states in the mean light curves of shorter period MCVs and perhaps the lightcurves of non-magnetic CVs (where a disk may make it difficult to see this effect). The diffusion timescale and hence the period of rotation of the field within the secondary is of order the synchronization timescale, so shorter period polar’s are unlikely to be in rotational equilibrium.
Earth’s Rotation and Polar Motion Based on Global Positioning System Satellite Data
Authors: Anderle R. J. , Beuglass L. K. , Carr J. T. 
Published: July 2016

AbstractUsing current procedures, polar motion and Earth’s rotation can be computed from 7 days of observations from four stations to four Global Positioning System Satellites to an accuracy of 1.5 m and .3 msec/day, respectively. Improved computational techniques or instrument accuracy and/or measurements from additional satellites or stations would give significant improvements in accuracy.
A New Dimension to Retrieval
Authors: Collins Mike J. 
Published: July 2016

AbstractSearching in online databases for specific numerical data and for chemicals by formulae has always been difficult or, at best, complex. Two new additional indexing services were introduced to the INSPEC database at the beginning of 1987 to overcome these problems: Chemical Indexing - for searching all kinds of inorganic compounds and material systems, and Numerical Data Indexing - for limiting searches to a specific value or range of values of a particular physical quantity. The literature of SN 1987A, the first supernova to be discovered in 1987, is used to demonstrate the powers of these new indexing tools and how they compliment traditional retrieval aids such as classification, descriptors, and identifiers.
Impact of Outdoor Lighting on Moths
Authors: Frank Kenneth D. 
Published: July 2016

ABSTRACTOutdoor lighting incapacitates and destroys some moths. It disturbs flight, navigation, vision, migration, dispersal, oviposition, mating, feeding, and crypsis. It may also snift circadian rhythms. Lamps may incinerate or desiccate moths, or lead to moth’s destruction by birds, bats, spider, and vehicular traffic. Conservation efforts need to consider disruptive ecological effects of outdoor lighting. Low pressure sodium lamps may reduce these effects.
Observations of Space Debris
Authors: Taff L. G. 
Published: July 2016

ABSTRACTOptical observations of near Earth and deep-space debris conducted at M.I.T.’s artificial satellite observatory will be discussed. A brief review of observing technique, regions of high debris density, and amount of debris in orbit will be given. The unique, duplex facilities of the observatory allow the discrimination of debris from meteors, the construction of an orbital element set, and real-time identification of cataloged artificial satellites. Near-Earth debris is present in large numbers in all the popular near-Earth orbits; at least 5-6 times the 5000-6000 objects in the NORAD catalog. In deep-space, the new presence of Ariane-related debris adds significantly to the existing population which is treble that cataloged by NORAD.
Electronic Smog in Europe
Authors: Kahlmann H.C. 
Published: July 2016

ABSTRACTWith so many satellites (current and anticipated) broadcasting all sorts of signals in all sorts of bands, a group of radio astronomers came together in 1987 to discuss the problems. This group has become the European Science Foundation Committee on Radio Astronomical Frequencies (ESF-CRAF). The terms of reference of this Committee, together with its future activities and possibilities within the European legal context were discussed in the oral paper.
Estimating Harmful Levels of Radio-Frequency Radiation
Authors: Crane Patrick C. , Hillenbrand Lynne A. 
Published: July 2016

Determining whether a particular radio transmitter will produce harmful levels of radio-frequency radiation at a location of interest (the “receiver,” be it a nearby home or a distant radio telescope), has two steps. The first is to determine which standard for harm applies: Section II reviews those for human exposure, for interference with electronic devices, for interference with optical and infrared astronomy, and for interference with radio astronomy.The second step is to estimate the propagation losses between the transmitter and the “receiver.” Many factors, several highly time variable, contribute to such losses - including atmospheric refraction, diffraction by obstacles, tropospheric scattering, and atmospheric absorption - and are discussed in Section III.
Radio Astronomy and the CCIR
Authors: Pankonin Vernon 
Published: July 2016

ABSTRACTThe International Radio Consultative Committee (CCIR) is a permanent organization within the International Telecommunication Union (ITU). The purpose of the CCIR is to provide technical advice to the ITU and its various organs and members on the characteristics of the radio services which are governed by the International Radio Regulations, a product of the ITU. This is accomplished through reports and recommendations which may result from the regularly scheduled meetings of the CCIR or from meetings convened to prepare for a special event such as an upcoming World Administrative Radio Conference (WARC). The CCIR is divided into Study Groups. Study Group 2 covers Space Research and Radioastronomy. This paper describes the interactions of radio astronomers with Study Group 2. The radio astronomy related Study Questions currently before this Study Group are delineated, and the nature of the active reports and recommendations are discussed.
Heat Pollution by Large Buildings and the Effects upon Astrometric Observations
Authors: Hughes James A. , Kodres Calvin A. 
Published: July 2016

ABSTRACTRecent, large scale, real estate development near the U.S. Naval Observatory has led to an investigation of the systematic atmospheric effects which heat from large buildings can cause. Results show that non-negligible slopes of the atmospheric layers can be induced which cause a surprisingly large anomalous refraction. The Navier-Stokes equations were numerically integrated using the appropriate boundary conditions and the resulting isopycnic tilts using the appropriate boundary conditions and the resulting isopycnic tilts charted. Rays were then essentially traced through the perturbed atmosphere to determine the magnitude of the anomalous refraction.
The distribution of types of Luminous Blue Variables
Authors: Bohannan Bruce 
Published: July 2016

AbstractIf Luminous Blue Variables (LBVs) are not each unique types, three broad groups can be characterized depending on the luminosity and location ofLBVsin the Hertzsprung-Russell diagram. To assist in defining the evolutionary nature ofLBVs, connections are made to stars that have similar spectral character with the suggestion that some of these objects that may someday becomeLBVs.
The optical micro-variations of the S Dor-type stars AG Car and HR Car
Authors: van Genderen A.M. , Thé P.S. , Heemskerk M. , Heynderickx D. , Larsen I. , Wanders I. , van Weeren N. 
Published: July 2016

Abstract.VBLUW photometry of high precision of two S Dor type stars AG Car (in a quiescent stage) and HR Car was made in 1987 and 1988. Both stars show visual micro variations with amplitudes of 0m.1 – 0m.2 with time scales– 10dfor AG Car and– 20dfor HR Car.
A Multi-Frequency Study of the Peculiar Interacting System ARP 206
Authors: Noreau Louis , Kronberg Philipp P. 
Published: July 2016

Arp 206 is a nearby (7.8 Mpc), relatively large (7′.5 x 2′.0), and bright ( = 11.07) interacting system comprising unequal members: NGC 3432 and UGC 5983. A third anonymous galaxy, “Arp 206c”, is visible in the field, (see Figure la) Vorontsov-Velyaminov (1959) included the NGC 3432-UGC 5983 pair in his Atlas and Catalogue of Interacting Galaxies (VV-11). On the other hand Arp (1966) interpreted the system as a galaxy with material ejected from the nucleus (Arp 206).Bertola (1966, 1968, and priv. comm.) obtained long-slit spectra of the largest galaxy of the pair, NGC 3432. This showed strong non-circular motions that could be interpreted as an explosion in its nucleus. This work is in line with a similar study of another system, Arp 205 (Bertola et al. 1983, Noreau and Kronberg 1986, 1987). In this first case it was found that the non-circular radial velocities were caused by the ‘re-entry’ of galactic material torn away by the interacting system.