bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systematics of Dwarf Novae
Authors: Warner B. 
Published: July 2016

AbstractFrom about 30 Dwarf Novae with the best determined distances the following relationships are found.(i)a tight correlation between absolute magnitude at maximum light, Mv (max), and orbital period, P.(ii)a correlation between Mv (min) and P showing wide scatter.(iii)a correlation between Mv (mean), the mean absolute magnitude averaged over normal outbursts, and P, again with wide scatter. The scatter is shown to correlate strongly with outburst timescale Tn.(iv)a strong correlation between range, Mv (min) - Mv (max), and Tn (the Kukarkin-Parenago relationship).(v)a strong correlation between range My. (mean) - Mv (max), and both Tn and P.This final correlation is interpreted in terms of the disc instability model of dwarf novae and successfully predicts the observed width of outburst versus P relationship.
Collective Properties of a Magnitude-Limited Sample of Cataclysmic Binaries
Authors: Ritter H. 
Published: July 2016

AbstractResults of an analytical discussion of observational selection in a magnitude-limited sample of cataclysmic binaries (CBs) are presented. It is shown that the dependence of the strength of selection in favour of massive white dwarfs, of the mean orbital inclination and the fraction of eclipsing systems in a sample on the limiting magitude mv reflects the large-scale distribution of CBs in the galaxy and the influence of interstellar absorption. Furthermore it is shown how selection in favour of massive white dwarfs depends on the mass radius relation of white dwarfs.
Cataclysmic Variables in a White Dwarf Survey at the South Galactic Pole
Authors: Bues I. 
Published: July 2016

AbstractDuring a ¡photometric and spectrophotometric survey of 200 white dwarf candidates with in a field around the South Galactic Pole two new cataclysmic variables have been identified and new observations of one already known object have been accumulated. Observations in the visible and UV-region show variability and differences in spectral type. If compared to the numbers of cataclysmic variables/white dwarfs as computed by Ritter and Burkert (1985)there is a shortage of a factor of 5.
Mapping the Line Emission Distribution of Cataclismic Variable Stars
Authors: Marsh T.R. , Horne K. 
Published: July 2016

AbstractWe describe a method for imaging the accretion disc of a Cataclysmic Variable star. We use the two-dimensional information contained in the line profiles as they vary with phase to invert the line formation process. Asymmetries in the disc, as are caused by the bright-spot, for example, are accounted for naturally.
Spectroscopy of the Primary and Secondary Components of the Dwarf Nova AH Herculis
Authors: Bruch A. 
Published: July 2016

AbstractThe dwarf nova AH Her belongs to those cataclysmic variables which show a composite spectrum in the optical range, containing emission lines from the accretion disk and absorptions from the secondary star. This has been shown by Horne et al. (1986). Anticipating the composite nature of the spectrum from the the B-V colour of AH Her, which is intrinsically redder then , I took spectra of the system in four nights in June 1984 at the 1.2-m-telescope of the DSAZ on Calar Alto in order to detect the secondary component. The wavelength range observed was 5300 Å – 7150 Å. Apart from H in emission which behaves in the same way as described by Horne et al., the spectra show in fact a definite absorption of the Na D lines to be attributed to the secondary star. The linestrength and the absence of any strong TiO features confines the spectral type of the secondary to between K2 and MO. It is possible to calculate the relative contributions of the primary and secondary to the total light at the wavelength of Na D as a function of the exact spectral subtype of the secondary, using the measured equivalent width of the Na D lines. Taking the spectral gradient of primary and secondary from the current literature the same can be done for the effective wavelength of the V band. It is then straightforward to calculate the system’s absolute visual magnitude and the distance. It turns out that AH Her is one of the intrinsically brightest dwarf novae known, regardless of the exact spectral subtype of the secondary.A complete account of the observations of AH Her and of the interpretations is given in a paper which has been submitted to Astronomy and Astrophysics.
Long-Term Optical Photometry of the Dwarf Nova VW Hyi
Authors: Van Amerongen S.F. , Van Paradijs J. 
Published: July 2016

AbstractLong-term five-colour photometry of the dwarf nova VW Hyi shows no evidence for a secular change of the flux during the quiescent interval between normal outbursts (3σ upper limits between 0.16 and 0.20 mag in the five passbands). However, the amplitudes in the orbital B-U and U-W colour curves change during quiescence. A delay in the progress of normal outbursts toward higher frequencies confirms the delay, seen with IUE, in the onset of a normal outburst toward higher frequencies. Just after outburst, the system is substantially bluer than later in quiescence.
X-Ray Emission from Non-Magnetic Cataclysmic Variables
Authors: Van Der Woerd H. 
Published: July 2016

AbstractEXOSAT observations of a large sample of non-magnetic cataclysmic variables have led to the detection of VW Hyi and OY Car as strong soft X-ray sources during superoutburst. The spectral characteristics of the X-ray emission of these SU Uma systems are compared. It is proposed that both systems have, besides a cool, optically thick boundary layer, an extended hot, optically thin corona.
Exosat Observations of H2252−035: Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission
Authors: Pietsch W. , Voges W. , Kendziorra E. , Pakull M. 
Published: July 2016

AbstractThe 805 sec pulsing X-ray source H2252−035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ~ 100% in the 2.3–7.9 keV band it is only ~ 40%. X-ray dips that are more pronounced in low energies occur simultaneously with the orbital minimum of the optical light curve. The medium energy spectra during dips with respect to the non dip spectrum can be explained by just enhanced cold gas absorption of an additional absorbing column of 2 1022 cm−2. Model spectra for the 805 s minimum have to include a strong iron emission line at 6.55 keV with an equivalent width of 3 keV in addition to a reduced continuum intensity (radiating area) and enhanced low energy absorption.
The Boundary Layer in Cataclysmic Variables
Authors: Shaviv G. 
Published: July 2016

AbstractRecent development in the theory of the boundary layer is considered. The model for the formation of a corona above the WD is discussed in some detail.The interaction of the boundary layer with the stellar interior and possible mixing between the hydrogen-rich accreted matter and the core material is discussed in view of recent numerical simulations of the boundary layer.
Two-Dimensional Numerical Models of the Boundary Layer of Accretion Disks in Cataclysmic Variables
Authors: Kley W. , Hensler G. 
Published: July 2016

AbstractNearly half of the total available accretion energy can be released in the boundary layer (BL) if the accreting object is slowly rotating. The spectral distribution of the emitted radiation depends crucially on the internal structure of the BL. Up to now no detailed models concerning the BL exist. We have developed an explicit two-dimensional numerical method written for axisymmetric accretion flows including viscosity effects and angular momentum. We display our first models concerning the BL structure incorporating variation of the stellar rotation and of the fraction of the released energy. The first results show a strong dependence of the BL structure on the local rate of cooling and on the rotation of the primary.
Disk-Instability Model for Outbursts of Dwarf Novae: Fine Mesh Calculations
Authors: Mineshige S. 
Published: July 2016

AbstractWe have executed fine mesh calculations which can almost fully resolve the transition front in the accretion disk of dwarf novae. Results show that the effects of thermal diffusion become very important only when the heating wave passes by. But it is unlikely that they cause drastic changes’ in the situation of wave propagation. The validity of the localized front approximation is examined. It is found that this approximation is relatively good for heating waves but it is marginal for cooling waves.
Theoretical Spectra of Cataclysmic Variables
Authors: Křiž S. , Hybený I. 
Published: July 2016

AbstractWe present two methods of modelling accretion disks in dwarf novae. The first one determines self-consistently the structure of a disk together with the radiation field. The computed theoretical spectra agree well with the observations of the dwarf nova WX Hyi in quiescence as well as in superoutburst. The second method is a modification of Tylenda’s (1981) approach. We have used it to calculate models of disks around main-sequence accretors. The most interesting result is that no unique solution exists for a moderate mass flux around 10−6 M⊙yr−1. Such disks are thus probably unstable.
The May 1985 Superoutburst of OY Carinae: II. Phase-Resolved IUE Spectroscopy and Exosat Observations
Authors: Hassall B.J.M. , Naylor T. , Bath G.T. , Charles P.A. , Sonneborn G. , Van Paradijs J. , Van De Woerd H. 
Published: July 2016

AbstractWe present ultraviolet and X-ray observations of the eclipsing SU UMa dwarf nova OY Car early in the decline from a superoutburst. From the UV emission line spectrum and lack of X-ray eclipse, we deduce the presence of an extended coronal region.
The Optical Spectrum of Nova LW Serpentis 1978
Authors: Prabhu T.P. , Anupama G.C. 
Published: July 2016

AbstractWe present optical spectroscopic data on the nova LW Serpentis 1978, covering its diffuse-enhanced phase until the onset of [OI] flash. The spectra, cover a range of 4000–8700 A, at dispersions ranging from 83–675 A mm−1.
‘Swinging Dipoles’ in Magnetic Close Binary Stars
Authors: Andronov I.L. 
Published: July 2016

AbstractThe recently discovered phenomena in polars - Magnetic Close Binary Stars (MCBS), are discussed. Asynchronous MCBS are on the ‘propeller stage’ (which is analogous to the investigated one for neutron stars), and are synchronizing during ts ≲ 103 yr, being during this stage rapidly evolving, mass ejecting systems. The accretion rate is largest when the angle θ between the magnetic axis and the line of centers is near zero. If θ ≈ 90°, then the magnetic field prevents the plasma flow, and the ‘magnetic valve’ becomes closed. Near this position the oscillations of the orientation of the white dwarf’s magnetic axis may be excited. This model of a ‘swinging dipole’ has such observational properties: (a) the system’s luminosity changes with characteristical times of some years; (b) the phase curves of light, polarization and radial velocities must be cyclically changing with a few year cycle; (c) one would observe the correlation between the phase shift of these curves, and the system’s luminosity. The observational data on polars are briefly discussed. All these phenomena are observed in AM Herculis and some other polars, but subsequent studies are needed to investigate the orientation changes of the magnetic axis, and so the structure and evolution of this exotic class of our Galaxy population.
Atomic Data Relevant to Line Formation in Strongly Magnetized White Dwarf Stars
Authors: Wunner G. , Geyer F. , Ruder H. 
Published: July 2016

AbstractThe discovery of magnetic field strengths in the range of 500 million Gauss in the objects Grw+70°8247 and PG1031+224 has given enormous impetus to investigations of magnetic white dwarf stars. We have determined intensities of Balmer transitions for B > 108 Gauss as a function of field and find strong oscillations of the transitions strengths, which are of importance to the quantitative analysis of the observed spectra and the interpretation of polarimetric measurements in these objects.
Spectral Variations in CH Cygni during the Activity Phase in 1982
Authors: Skopal A. , Mikolasjewski M. , Tomov T. 
Published: July 2016

AbstractRapid variations of the radial velocities of absorption components of Ti II lines in CH Cyg are presented. The periods of these variations are determined to 1.89 and 41.07 days in 1982. The variations are interpreted through oscilliations in the mass transfer from the M component onto the accretion disk of the companion during periastron passage.
The Symbiotic Binary System EG Andromedae
Authors: Chochol D. , Skopal A. , Vittone A. , Mammano A. 
Published: July 2016

AbstractPhotometric observations of the symbiotic star EG and confirm that the binary system is eclipsing. The epoch of primary minimum is computed. The new period 474 days instead of 470 days is estimated by a comparison of line profiles of Balmer lines taken in 1967–69 and 1982–84. The new ephemeris is
X-Ray and Ultraviolet Observations of AG Draconis during Quiescence and Outburst
Authors: Cassatella A. , Córdova F.A. , Friedjung M. , Kenyom J. , Piro L. , Viotti R. 
Published: July 2016

AbstractWe describe the first X-ray monitoring of a symbiotic star during phases of enhanced activity. AG Dra is a Pop II object with a composite spectrum, characterized by a cool K-type component, prominent high ionization emission lines and a strong UV continuum which is attributed to a hot dwarf companion. Periodic variability of the UV radiation during minimum could be attributed to the orbital motion of the system. In April 1980 HEAO-2 detected an intense, soft X-ray flux from AG Dra, stronger than in other symbiotic stars. After one major outburst of November 1980, which continued until 1983, two more outbursts occurred in February 1985 and January 1986, and coordinated X-ray (EXOSAT) and ultraviolet (IUE) observations were organized to study the behaviour of AG Dra during different activity phases. EXOSAT observations made during decline after the 1985 outburst, revealed a weak X-ray flux in the Thin Lexan filter of the Low Energy dedtector. Observations made during minimum, in June and November 1985, at phases 0.22 and 0.50 of the UV light curve, disclosed the presence of an intense X-ray flux, which was not occulted in November. AG Dra was again observed with EXOSAT in February 1986 when the stellar luminosity was still at maximum. No X-ray flux was detected, in spite of the prominent, high ionization UV spectrum observed with IUE.A detailed discussion of the X-ray and ultraviolet results on AG Dra in the light of possible models is in progress.
Periodic Nature of Cometary Motions as Known to Indian Astronomers Before Eleventh Century A.D
Authors: Sharma S.D. 
Published: July 2016

AbstractApparitions of comets were thought to be a bad omen in earlier times in almost all the old civilizations. This led to correlating these apparitions with some particular events which took place simultaneously. Although the information was collected and recorded merely for astrological purposes, yet these records are in no way less important from astronomical points of view. Ancient Indian astronomers like Garga, Marīci, Asita, Devala and others made cometary studies and recorded their trajectories(Bṛhat-saṃhitā, Chapter on Ketucārādhyāya).In earlier times there was a notion that the comets were heavenly bodies and their apparitions, paths, rising and setting in the sky, could not be found out by mathematical calculations as is clear from the following śloka(Bṛhat-saṃhitā, Chapter on Ketucārā dhyāya).
Sky Calendars of the Indo-Malay Archipelago
Authors: Ammarell Gene 
Published: July 2016

Research conducted over the past several years has revealed a richly diverse astronomical tradition in the Indo-Malay cultural area. I wish, in this paper, to share some of this richness by describing several of the many and diverse observational techniques used by the Indo-Malay peoples to help regulate their agricultural cycles.Inhabiting mountain sides, river valleys, and coastal plains, the Indo-Malay peoples are faced with a rather unpredictable tropical monsoon climate. In response to this geography and climate they have adopted two distinct types of rice farming: swidden and padi, or dry and wet.Padi farming is sedentary and relies upon heavy monsoon rains and/or irrigation for the rather large and dependable supply of water required: rice plants must be submerged from the time that they are planted in the nursery through transplanting and until seed is set. From thereon, dry weather is essential for the seed to properly ripen. Padi fanning is widely practiced on coastal plains and terraced hillsides by people such as the Javanese, the Sasak of Lombok, and the Malays of Kedah and Perak.
Astronomical Aspects of “Pranotomongso” of The 19th Century Central Java
Authors: Daldjoeni Nathanael , Hidayat Bambang 
Published: July 2016

It has been shown by Aveny (1981) that the development of indigenous astronomical systems in tropical cultures, whether the motive was religious or practical, centered toward a reference system consisting of zenith and nadir as poles and the horizon as a fundamental reference circle. Such a reference system differs remarkably to the celestial pole-equator (or ecliptic) systems employed by civilizations in temperate zones (also see Brennand, 1896; Stencel, et.al., 1976).In order to obtain more insight of the view expounded by Aveny (1981) the authors undertook a test case study of the astronomically related time-keeping practice in Java. “Pranotomongso” has been chosen as it is well documented since 1855. According to Daldjoeni (1984) the “pranotomongso” (literaly means the arrangements of seasons) functions well as a practical guide for agricultural activities for the rural peasants in Central Java.
Enhancement of Faint Images from UK Schmidt Telescope Plates
Authors: Hadley B.W. 
Published: July 2016

The UK Schmidt Telescope has taken several thousand photographs especially on fine grain Eastman Kodak IIIa-J and IIIa-F emulsions (see Cannon, 1984) which were hypersensitised before exposure in the telescope to improve their ability to record very faint signals.Relatively little work has been done on further post-processing techniques to enhance photographically the faint signal from sources very near to the sky background level. Work is currently being undertaken by Malin (AAO) and others including staff at ROE to enhance faint photographic signals without a corresponding increase in noise, either by making high contrast enlargements from small areas of the original plate, or by making contact copies of the whole plate onto high contrast line material.
A System for Object Detection and Image Classification on Photographic Plates
Authors: Malagnini M.L. , Pucillo M. , Santin P. , Sedmak G. , Sicuranza G.L. 
Published: July 2016

AbstractA system for detecting and classifying (faint) astronomical objects on photographic plates is presented. The system is planned to perform all the main operations, from the digitization of the plates with a PDS lOlOA microdensitometer up to the final classification, under the control of the VAX-11/750 central processor. The aim of the project is to obtain an objective classification and reliable description of large amounts of objects, in a reasonable amount of time,for specific research projects. The detection and classification procedure is organized in modules, each of which is general enough to be applied to different kinds of analyses and to different classes of objects, according to astronomical requirements. An example of application to the problem of star/galaxy discrimination is given.
Objective Prism Spectroscopy of the Tail of Comet Austin 1982 G
Authors: Jockers K. , Balázs L.G. 
Published: July 2016

AbstractThe main emissions of the cometary plasma tail are due to CO+ (400/402 and 425/427 nm) and H2O+ (aroud 650 nm). Emissions of CO2+ at 367 nm have also been observed (Swings and Page 1950). These ions relate much more directly to the presumed mother molecules of the cometary nucleus (like H2O, CO2, CO) than most strong emissions of the neutral cometary coma (Ruebner and Giguere, 1980, see also Jockers, 1982). Therefore it is important to determine column densities of cometary ions. So far only very few measurements of ion column densities are available (Wyckhoff and Wehinger, 1976a, b; Arpigny, 1965).
Statistics of A-Type Stars As Possible Indicator of Star Formation
Authors: Balázs L.G. 
Published: July 2016

AbstractSpace distribution and kinematics of stars are determined by the initial distribution, i.e. the distribution of spatial positions and kinematical data just after the birth, and dynamical effects the stars experienced during their life. Evidence is presented that the space distribution of A type stars perpendicular to the galactic plane might be a result of periodic star formation having a characteristic time of 108<τ<6x108 years.
Ellipticities of “Blue” and “Red” Globular Clusters in the SMC
Authors: Kontizas E. , Dialetis D. , Prokakis Th. , Kontizas M. 
Published: July 2016

AbstractThe projected ellipticities of twenty four “blue” and “red” globular clusters of various ages and positions in the SMC have been found using isodensity contours. The derived ellipticities have shown that the globular clusters of the SMC are more elliptical than their counterparts of the Large Magellanic Cloud (LMC) and our Galaxy. The observed ellipticities for both cluster types, do not support any age dependence.
Reduction of Slitless Spectra - The Detection of Faint Emission Lines
Authors: Adorf H.-M. , Röser H.-J. 
Published: July 2016

AbstractWe have developed a spectra reduction system producing relative spectrophotometry directly from prism as well as from grating spectra plates. Lines and other spectral features are detected, and their essential parameters are measured automatically. A deep quasar survey using this technique is now underway.
High Resolution Multichannel XUV Spectrometer with A 3-Picosecond Time-Resolution for Laser-Produced Plasmas Diagnostics
Authors: Schwob J.L. , Mexmain J.M. , Busquet M. , Bourgade J.L. , Louis-Jacquet M. , de Mascureau J. , Sauneuf R. 
Published: July 2016

AbstractA new XUV spectrometer designed to have a time-resolution of 3 ps and a spectral resolution of 0.1 Å is described. It is basically a modified version of a Schwob-Fraenkel spectrometer, which is coupled to a new ultrafast electronic streak camera.