bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Emission from Non-Magnetic Cataclysmic Variables
Authors: Van Der Woerd H.
Published: July 2016

EXOSAT 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

The 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

Recent 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

Nearly 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

We 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

We 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

We 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

We 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.
Evolution of Magnetic Cataclysmic Binaries
Authors: Lamb D.Q. , Melia F.
Published: July 2016

More than a third of all cataclysmic variables (CV’s) with established binary periods contain strongly magnetic degenerate dwarfs (Ritter 1985). The history of the manner in which the magnetic character of these systems was established suggests that many more CV’s—perhaps most—are magnetic. By comparison, only ≈ 2% of isolated degenerate dwarfs are magnetic (Angel, Borra, and Landstreet 1981; Schmidt and Liebert 1986). The magnetic CV’s divide naturally into two subclasses: the DQ Herculis stars (recently reviewed by Warner 1983, 1985) and the AM Herculis stars (recently reviewed by Liebert and Stockman 1985). Each subclass currently has about a dozen members.
‘Swinging Dipoles’ in Magnetic Close Binary Stars
Authors: Andronov I.L.
Published: July 2016

The 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

The 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

Rapid 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

Photometric 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

We 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

Apparitions 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.
Guest Stars: Historical Supernovae and Remnants
Authors: Velusamy T.
Published: July 2016

Supernova explosions occur in massive stars in their final stages of stellar evolution. The explosion leaves behind a collapsed object, usually a neutron star observable as a pulsar, and an expanding outer envelope of the star observable as a supernova remnant (SNR). Because of the large amount of energy in the range of 1050 −1052 ergs released in the explosion, the energy radiated by the exploded star is equivalent to that of millions of normal stars. Thus a "new star" seems to appear and is easily visible to the naked eye for several months. Astronomers have estimated that in our galaxy such supernova explosions occur once about every 50 years. In ancient times, the occurrence of supernova might have been noticed as appearance of a bright new star which faded away into obscruity after a few months. Thus the ‘guest stars’ in the ancient records are indeed possible occurrences of supernova explosions in the galaxy. The guest star of 1054 A.D., well recorded by Chinese and Japanese astronomers is the best known historic supernova (Brecher et al. 1983; and references therein); today its remnants the Crab Nebula and the pulsar are observable over the entire electromagnetic spectrum from radio to γ-rays. Of the 150 SNRs known in our galaxy, only about 10 have been identified with guest stars of historical supernovae.
The Detection of Faint Images Against the Sky Background
Authors: Malin David F.
Published: July 2016

This title was first used by William Baum (1955) in his contribution to an IAU Joint Discussion on photoelectric image tubes and their astronomical applications. The general tone of the ten or so papers collected in the 1955 IAU Transactions was optimistic. It seemed quite clear that the high quantum efficiency of the electronic devices existing at the time would soon be turned to astronomical advantage and that objects much fainter than those detectable photographically were well within reach.
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

A 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.
On the Astronomical Research With the Torun 60/90 Cm Schmidt Telescope
Authors: Woszczyk A.
Published: July 2016

The Torun Schmidt telescope and its scientific applications are described. A special attention is given to the Torun Objective Prism Sky Survey.
Astrometry With Schmidt Telescopes
Authors: Murray C A
Published: July 2016

Photographic astrometry, including work with Schmidt telescopes, can be divided into two main fields, (i) the measurement of positions of objects relative to a reference frame of stars with known celestial coordinates, and (ii) the measurement of relative proper motions and trigonometric parallaxes from a series of plates taken on the same field. The former demands a knowledge of the absolute transformation between angles on the sky and measurements on a plate, whereas in the latter we are only interested in differential transformations from plate to plate. The potential value of Schmidt telescopes for both these fields of astrometry lies in the large area of sky and range of magnitude which can be imaged on a single plate. The former advantage is however, to some extent offset by the curvature of the focal surface which means that, in order to utilize the full field the plates must be constrained to the form of the focal surface during exposure.
Objective Prism Spectroscopy of the Tail of Comet Austin 1982 G
Authors: Jockers K. , Balázs L.G.
Published: July 2016

The 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

Space 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.
Use of the UK Schmidt For A Photometric Investigation of Red Stars in the Orion Nebula Molecular Complex
Authors: Andrews A. David , McGee Brian
Published: July 2016

As a region of recent star formation and intense stellar activity the Orion Complex extending over several square degrees is of paramount importance in the study of early evolution and activity in the stellar chromospheres of low mass stars. Although red stars form a rather inhomogeneous group, including foreground K-M dwarfs, distant K-M giants, carbon stars and a variety of reddened objects, in principle these can be separated from a combination of photometric, spectroscopic and kinematic data. The proximity of the Orion Complex and its relatively high galactic latitude mean that future astrometric and radial velocity work will yield useful kinematical information on all member stars, including the enigmatic pre-main sequence stars on the lower part of the HR diagram. For these stars, differences in spectroscopic properties, photometric behaviour, kinematics and the interstellar environment contain the key to some of the problems, presently insurmountable, in the early evolution of the entire Orion Complex.
A Survey of Northern Bok Globules and the Mon OB1/RI Association For H-Alpha Emission Stars
Authors: Ogura Katsuo , Hasegawa Tatsuhiko
Published: July 2016

The most direct approach to the suggested relationship of Bok globules to star formation is to search for actual spots of star birth in or around them. But no protostellar objects have hitherto been found by infrared and/or radio observations. Optically relevant to this are the discoveries of some Herbig-Haro objects and pre-main sequence stars associated with cometary globules inside the Gum Nebula (Reipurth 1983).
Hamburg Observatory Northern Milky Way Spectral Survey For Emission Objects
Authors: Kohoutek L.
Published: July 2016

Objective-prism spectral surveys open the possibility to search for faint emission-line objects with the aim to complete their statistics and to pick out most interesting individual objects for further study. In the years 1964 - 1970 the Hamburg Hα Spectral Survey of the Northern Milky Way was accomplished using the Schmidt camera (80/120 cm, f= 240 cm) in Bergedorf with the following parameters: area 1 32° - 214°, -10°<b<+10°, 160 fields. Kodak 103aE + RG1, exp. 60min, widen. 10", 4° prism (580 Å/mm at Hγ ). As a main result the list of about 140 faint objects classified as planetary nebulae or possible planetary nebulae (Kohoutek,1965, 1969a,1972), and the identification of about 1500 new stars having Hα in emission (Kohoutek, Wehmeyer, in preparation) can be reported. The best known examples of this survey are K 3-50, a prototype of a compact H II region, and the symbiotic variable HBV 475 = V 1329 Cyg (Kohoutek, 1969b), which is also classified as a protoplanetary nebula.
Ellipticities of “Blue” and “Red” Globular Clusters in the SMC
Authors: Kontizas E. , Dialetis D. , Prokakis Th. , Kontizas M.
Published: July 2016

The 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.
Photometry of Extended Sources
Authors: de Vaucouleurs G.
Published: July 2016

As a contribution to the continuing struggle for precision and reliability in photographic surface photometry with Schmidt telescopes the following sections review some of the main sources of errors and ways to avoid them, where possible.
Reduction of Slitless Spectra - The Detection of Faint Emission Lines
Authors: Adorf H.-M. , Röser H.-J.
Published: July 2016

We 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.
Optical Design with the Schmidt Concept: 1) Ground-Based Development: 2) The Space Schmidt Project for the 1990's ?
Authors: Lemaître G.
Published: July 2016

The basic principle of the camera described by Bernard Schmidt in 1932 is that a single concave mirror with a stop at its center of curvature has no unique axis and therefore yields equally good images at all points of its yield. The field is curved, and to correct the spherical aberration produced by the mirror, Schmidt introduced, in the stop at the center of curvature of the mirror, a thin non spherical corrector plate of glass. Around 1930 at the Hamburg Observatory and in spite of many difficulties, it was Schmidt's genius as an optician that succeeded - after several judiciously interpreted trials - in figuring a corrector plate by elastic relaxation, and thus demonstrated the optical performance of this new generation of instruments.
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

A 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.
Laboratory Astrophysics Experiments in X-Ray Transfer Physics Relevant to Cosmic Accretion-Powered Sources
Authors: Kahn S.M. , Craig W. , Schachter J. , Wargelin B. , Kapteyn H. , Falcone R.W. , Hettrick M.C. , London R.A. , Lee R.W.
Published: July 2016

The interpretation of upcoming cosmic soft X-ray spectroscopic observations may require a vast improvement in the state of our knowledge of basic atomic physics and radiation transfer processes, particularly for the important class of accretion-powered systems such as cataclysmic variables, X-ray binaries, and active galactic nuclei. For these sources, short wavelength spectral features are formed in the transfer of X-radiation from a powerful central source outward through a cooler, surrounding medium. The line emitting gas is photoionized and the level populations are determined largely by recombination cascades and photoexcitation as opposed to collisional effects. These processes can be rather complex and many uncertainties remain. We are developing a new approach to this problem using time-resolved studies of laser produced plasmas. Experiments which are currently underway include the measurements of: (a) inner and outer shell photoabsorption cross-sections of intermediate ions of abundant elements, and (b) fluorescent excitation processes due to wavelength coincidences of resonant transitions from different ions. In connection with this program, we have developed a novel reflection grating spectrometer coupled to a streak camera which provides high resolution spectra at soft X-ray and EUV wavelengths at the sub-nanosecond level. We describe our laboratory facility and some of our preliminary experimental results.
Monte Carlo Algorithms for Moments of Transition Arrays
Authors: Goldberg A. , Bloom S.D.
Published: July 2016

Closed expressions for the first, second, and (in some cases) the third moment of atomic transition arrays now exist. Recently a method has been developed for getting to very high moments (up to the 12th and beyond) in cases where a “collective” state-vector (i.e. a state-vector containing the entire electric dipole strength) can be created from each eigenstate in the parent configuration. Both of these approaches give exact results. Herein we describe astatistical(or Monte Carlo) approach which requires onlyonerepresentative state-vector |RV> for the entire parent manifold to get estimates of transition moments of high order. The representation is achieved through the random amplitudes associated with each basis vector making up |RV>. This also gives rise to the dispersion characterizing the method, which has been applied to a system (in the M shell) with≈250,000 lines where we have calculated up to the 5th moment. It turns out that the dispersion in the moments decreases with the size of the manifold, making its application to very big systems statistically advantageous. A discussion of the method and these dispersion characteristics will be presented.
Specific Features of Stark Broadening of Helium-Like Multi-Charged Ion Spectral Lines
Authors: Gavrilenko V.P. , Gaisinsky I.M. , Ispolatov Y.O. , Oks E.A.
Published: July 2016

Recently as a result of more active research on dense high temperature plasmas prominent importance has been acquired by the development of the theory of Stark broadening of multi-charged ions’Spectral lines (SL). This theory must take into account, on the one hand, the presence of fine structures in ion energy levels, and on the other hand, the effects appearing in the dense plasma:(1) dipole as well as quadrupole interaction with plasma ion microfield; (2) plasma polarization shift (PPS) of SL due to the mean electric field where the ion emitter is situated. Over the recent years a number of papers has appeared [1-4] which consider different aspects of the theory for ions with one and with two electrons.
Wavelengths of the 3p-3d Transitions of the Co- and Fe-LIKE Ions: The Effects of Electron Correlation
Authors: Chen M.H.
Published: July 2016

The experimental observations of the 3p63d92D – 3p53d102P transitions of the Co-like ions and 3p63d83F4– 3p53d93F3of the Fe-like ions have recently been extended to highly charged ions of heavy elements up to uranium (Z = 92). A comparison between the observed energies and calculated values from the Dirac-Fock model indicated persistent discrepancies of 3–4 eV for all ions. Systematic multiconfiguration Dirac–Fock calculations for these transitions have been carried out with emphasis on the effects of electron correlation. The previously found discrepancies between theory and experiment have mostly been removed after the inclusion of the electron–electron correlation effects in the theoretical calculations.
Density and Temperature Diagnostics of a Ne-Like Germanium Plasma Created by Laser
Authors: Berthier E. , Bourgade J.L. , Combis P. , Jacquemot S. , Le Breton J.P. , Louis-Jacquet M. , Naccache D. , Nail M. , Peyrusse O.
Published: July 2016

In the frame-work of X-ray laser studies, experiments on Ne-like Ge plasma have been performed by laser Irradiation at λ = 1.053 μm. Amplification in lasing transitions has been observed by varying the plasma length. Theoretical calculations of excited level population allow us to determine density and temperature from line intensity ratios.
The Calculations for Determination of the Age of Supernova Remnants and Galaxy Clusters by Measurements of Hyperfine Splitting in Highly ionized Atoms with Unstable Nuclei
Authors: Band I.M. , Listengarten M.A. , Trzhaskovskaya M.B.
Published: July 2016

The possibility of using the transitions between HFS components of atoms with nonstable nuclei in the spectra of hot gas in the supernova remnants and galaxy clusters for obtaining the information on the age of the objects was mentioned in /l/ without calculations. Here we present the numerical results for some ionized atoms obtained by relastivistic Hartree-Fock-Dirac method. Fermi distribution of nuclear charge density, vacuum polarisation, electron anomalous magnetic moment and reduced mass were taken into account. The HFS energy levels can be written as

where A=A’(μ/J). HFS constants A’ in millielectronvolts for H- Li- and Na-like ions of unstable isotops with well known magnetic moments with Z < 53 are given in the table (abundance rapidly decreases with increasing of Z). For the s-electrons, wavelength λ = (hcJ)/(Aμ(J+(1/2))); J is the nuclear spin, hc= 1,23985.10−4eV.cm T1/2is the halflife.
Recent Radiative and Collisional Atomic Data of Astrophysical Interest
Authors: Baluja K.L. , Butler K. , Le Bourlot J. , Zeippen C.J.
Published: July 2016

Using sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4and 2s2p5configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3ground configuration of CℓIII, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project.
XUV Lasers - A Survey of Progress
Authors: Key M.H.
Published: July 2016

There has been an upsurge recently of both progress and interest in the development of XUV and X-ray lasers to such an extent that it is now possible to envisage the systematic development and application of a new family of powerful pulsed XUV lasers. The potential and actual characteristics of these lasers and the highlights of recent work will be reviewed.
The Possibilities of the Use of Replica X-Ray Imaging Mirrors in Plasma Diagnostics
Authors: Hudec R. , Valníček B. , Svátek L. , Landa V. , Fiedorowicz H.
Published: July 2016

The replica technology based on galvanoplastics offers the unique possibility of manufacturing of precise light-weight and low-cost imaging X-ray mirrors having both very small and large apertures of various types (paraboloid-hyperboloid, paraboloid-paraboloid, elipsoid- hyperboloid). Some of the further advantages such as the wide use of X-ray microscopic systems and the possibility to built large arrays of identical optical systems for simultaneous multispectral analysis are discussed together with the presentation of some examples of the manufactured mirrors. The first preliminary results are also presented.
Ultraviolet Absorption of Refractory Elements by a Dual Laser Plasma Method
Authors: Costello J.T. , Lynam W.G. , Carroll P.K.
Published: July 2016

The dual laser-produced plasma technique for the study of ionic absorption spectra has been developed by the use of two Q-switched ruby lasers to enable independent generation of the absorbing and back-lighting plasmas. Optical pulse handling is used in the coupling cicuits to enable reproducible pulse delays from 250 nsec. to 10 msec, to be achieved. At delay times > 700 nsec. spectra of essentially pure neutral species are observed. The technique is valuable, not only for obtaining the neutral spectra of highly refractory and/or corrosive materials but also for studying behaviour of ionic species as a function of time. Typical spectra are shown in Fig. 1.
Recent Results on Soft X-Ray Amplification by Lithium-Like Ions in Plasmas
Authors: Carillon A. , Klisnick A. , Jamelot G. , Gauthé B. , Gadi F. , Jaeglé P.
Published: July 2016

We have shown that several transitions of Li-like ions give rise to population inversions during the recombination of laser-plasmas /1/. An extensive study has been made for the 3d–5f transition lying at 105.7 Å. It has shown a gain coefficient with a maximum around 2cm−1occuring about 6 nanosecond after the top of the 2-ns laser pulse. We extended recently this study to the 3d–4f line ar 154.7 Å and we observed a similar value of gain with the same temporal behaviour. Moreover, following calculated predictions for higher-Z ions /2/, we studied the 3d-5f transition of S13+which takes place at 65.2 Å. This study gives the first preliminary evidence of a gain coefficient of about 1 cm−1.
Some Applications in Atomic Physics of the Theory of Coupled Differential Equations
Authors: Chuan C.X. , Bougouffa S.
Published: July 2016

La théorie sur la séparation d’un système d’équations différentielles couplées est appliquée à deux exemples comportant chacun deux équatlons. Nous présentons une discussion des résultats numériques ainsi qu’une généralisation à un systèms avec un nombre quelconque d’équations.

The theory on the separation of a system of coupled differential equations is applied to two examples each having two equations. Numerical results are discussed and a generalisation to a system of any number of equations will be outlined

The system of coupled differential equations (CDE) to be considered here is:

The qeneral theory has already been presented In previous papers [1], [2],we continue to keep in the present one the same notations and conventions. Its implementation as well as the test of its efficiency will be discussed below.
High Resolution X-Ray Spectroscopy at Jet
Authors: Giannella R.
Published: July 2016

A high resolution X-ray crystal spectrometer was installed at JET in 1986. The main task of this instrument, designed and built by the ENEA Frascati Laboratory in collaboration with JET, is the measurement of the ion temperature and rotation velocity from Doppler broadenings and shifts. Stringent operation requirements considerably conditioned its versatility as a survey instrument or a tool for fundamental research. The unique conditions of the JET plasmas, however, allowed to observe in high resolution and identify lines from the highest ionization stages (B-like to H-like) of nickel in the vicinity of the resonance transitions of the one- and two-electron systems of this element. These spectra and their relevance to the study of JET physics are briefly presented. The comparison with atomic physics theoretical computations of He-like and H-like ions spectra observed at JET is also shortly presented. The most intense among these lines could regularly be monitored with adequate time resolution as to allow the production of an extensive data base. The experimental spectra are simulated by integrating the theoretical ones along the spectrograph line of sight across the plasma. Ion temperature as well as rotation velocity measurements in ohmic plasmas and additionally heated ones are discussed and their relationship with other physical quantities and operational parameters are shortly reviewed. Details of the spectrometer design, its lay-out on the JET site and its operational capabilities are also given.
Localisation of Chromospheric Evaporation in Solar Flares, by the Analysis of X-Ray Spectra
Authors: Gabriel A.H. , Millier F. , Lizambert N.
Published: July 2016

Analysis of solar flares using the data from the Bent Crystal Spectrometer on the SMM solar flare satellite, shows a thermal plasma which expands vertically at a velocity of up to 350 km s−1. This plasma, at a temperature of the order 25 106K is observed in the line radiation of He-like Ca XIX. Its velocity is determined by measuring the blue shift of the resonance line “w”, whereas its intensity is expressed relatively to that of the stationary component. We analyse the variations of velocity and relative intensity of the evaporating plasma as a function of its location on the solar disc for 33 flares during the year 1980. The results are compared with the values expected from two alternative models A and B. On the basis that when observed at the limb, such flares do not usually show a blue shift, model A interprets this as due to the fact that the motion of the explosive plasma is perpendicular to the line-of-sight. Model B assumes that the process of chromospheric evaporation produces a “well” in the chromosphere, and therebye occults some of the emission of the ejected material. It is clear that the two models predict different velocity and relative intensity variations as a function of the distance of the flare from disc center. The lack of blue shift for 10 disc flares supports strongly the model B, i.e the existence of a “well” whose depth / diameter is between 0.1 and 5 as shown by our observations.
Needs for High Resolution Spectroscopy in Ultraviolet Solar Physics
Authors: Lemaire P.
Published: July 2016

The study of the solar atmosphere (from 5000 °K to few millions °K) is made through ultraviolet lines emitted by ionized elements. Some experiments (OSO 8, SMM, HRTS), observing above 100 nm have resolved the fine solar structure with a good spectral resolution. The understanding of the heating processes, the solar wind generation and its acceleration mechanisms require a global and detailed mass and energy budget of the atmosphere. The new ultraviolet spectrometers proposed on SOHO satellite are able to combine enough angular, spectral and temporal resolutions to establish this budget.
Consideration for the Design of the Driving and Bearing System for Large Telescopes
Authors: Taddei F. , Tomelleri R.
Published: July 2016

The Astronomers target for the present and the next decade is the construction of large telescopes 3,5 - 4 m. primary mirror diameter and very large telescopes 8 - 9 m. primary mirror diameter, in the array or multi-mirror design, improving at the same time the performance of the instruments compared to the efficiency and precision of the same.
The ESO Off-line Telescope Testing Technique Illustrated with Results for the MPIA 2.2 m Telescope II
Authors: Wilson R.N. , Franza F. , Noethe L. , Tarenghi M.
Published: July 2016

The ESO test device is based on the proposal of Shack

Fig. 1 shows the principle of this method, which we call the SHACKHARTMANN (S-H) method as it is derived from the well-known conventional Hartmann technique. The beam from the telescope focus (6) is transmitted by a beam-splitting cube (2) of high quality to a collimating (Fabry) doublet objective (3). This images the exit pupil of the telescope to the plane (4) where a special SHACK lenticular raster is inserted. Each lens of this raster then forms a point image of that part of the parallel beam incident upon it on to a photographic plate (5) placed at the focal distance of the raster lenses from (4). The angular aberration in the telescope image is thus transferred through the system and shows as a transverse displacement of the spots.
Astronomical Seeing at Mauna Kea and in Particular at the CFHT
Authors: Racine René
Published: July 2016

The astronomical seeing at the CFHT is excellent. It now averages  = 0.9" and is continuously improving as a result of seeing conservation measures in the telescope building. Our studies suggest that the average natural seeing on Mauna Kea should be ~ 0.6". Very high (<0.2") resolution imaging at the CFHT, through adaptive optics, appears feasible.
On the Importance of Active Image Stabilisation
Authors: Noordam J.E.
Published: July 2016

The performance of an optical telescope can be improved considerably by opening the shutter only at moments of good seeing. The resulting instantaneous highresolution images must be corrected for shift before adding them all together. The optimum aperture diameter for which this technique works well is 1 meter or less, depending on atmospheric conditions. Image stabilisation not only improves the resolution and thus the point-source sensitivity, but it is also expected to improve the performance of speckle interferometry and optical aperture synthesis. This makes its implementation on large telescopes desirable. While it is certainly possible to do this by treating a large filled aperture like a set of independent subapertures, a much more logical approach would be to build an array of 1-meter telescopes, preferably mounted in a single large frame so that it can be pointed in all directions without extensive pathlength compensation. Such a “Many Mirror Telescope” has many advantages, and is feasible because image stabilisation helps to solve the beam-combining problem.
Image-Slicers
Authors: Richardson E.H. , Fletcher J.M. , Grundmann W.A.
Published: July 2016

The diameter of stellar images produced by Earth-based telescopes often exceeds the width of the entrance slit of the associated spectrograph. It is not uncommon for more starlight to be wasted on the jaws of the slit than is transmitted by the slit. The purpose of an image-slicer is to redirect the light from the slit jaws into the slit; to do so, the length of the slit illuminated by starlight must be increased, either by stacking slices of the image along the slit, or by elongating the image and superimposing full-length slices of it. Thus, in order to work, an image-slicer of whatever type must lose spatial resolution of the sky along the slit.
Refractive vs Reflective Correctors
Authors: Richardson E.H. , Morbey C.L.
Published: July 2016

Improved designs of refractive correctors produce excellent images with fast telescopes such as those with an F/1.5 prime focus and F/3.5 secondary focus. The fields are flat and there is compensation for the chromatic effect caused by windows. Disadvantages of such correctors are that stray light is produced at the optical surfaces, the elements must be supported at their edges, prerequisite high quality glass is available in only limited sizes, and all wavelengths are not transmitted.

Reflective correctors, on the other hand, can produce diffraction limited images at all wavelengths and the mirrors can be supported across their backs as well as at their edges. Disadvantages are that the images are degraded by any substantial window (such as a detector faceplate), there is more central obstruction, and the correctors are sometimes very large and heavy.

Except, perhaps, for a specialized telescope, such as one devoted to multi-object slit spectroscopy using fibres, the refractive corrector is preferable at fast foci.

A good combination is a Ritchey-Chretien (R-C) telescope with refractive correctors at the fast prime and secondary foci, and a reflective corrector-magnifier for the slow infrared focus.
Focal Reducer Techniques for Direct Imaging and Field Spectroscopy with Large Telescopes
Authors: Geyer Edward H. , Nelles Bruno
Published: July 2016

To exploit the full effectiveness of large ground based telescopes, the focal reducer technique can be applied very adequately. We review recent Hoher List observatory developments of observing techniques for direct imaging, field spectroscopy with multi-slit and masking methods for background supression and double-grism arrangements (heliometer principle)for absolute radial velocity determinations with a focal reducer field spectrograph.
Recent Developments in Coatings, Gratings, and Reflective Components
Authors: Shannon R. R.
Published: July 2016

The requirements on gratings and coatings for astronomical use differ from the general industrial requirements primarily in the scale of the components to be fabricated. Telescopes have large primary mirrors which require large coating plants to handle the components. Dispersive elements are driven by the requirement to be efficient in the presence of large working apertures, and usually optimize to large size in order to efficiently use the incoming radiation. Beyond this, there is a “new” technology of direct electronic sensors that places specific limits upon the image scale that can be used at the output of a telescope system, whether direct imagery or spectrally divided imagery is to be examined. This paper will examine the state of the art in these areas and suggest some actions and decisions that will be required in order to apply current technology to the predicted range of large new telescopes.
Interstellar Matter with Very Large Telescopes
Authors: Lequeux J.
Published: July 2016

Interstellar matter is certainly one of the fields where a very large telescope (VLT) will prove to be most fruitful. This includes (somewhat paradoxically, but this will be explained later) the study of extended emissions. I will now examine in turn the different domains of interest for a VLT.

I. Neutral diffuse matter

Optical and near IR observations will mainly contribute to this domain through high-resolution spectroscopy of interstellar absorption lines in the spectra of stars. These lines are resonant lines of atoms (NaI, KI, etc.) or ions (CaII, TiII, etc.) as well as of some molecules (CH+, CH, CN, CS+, C2 in the near IR). Clearly this kind of study is always photon - limited; a VLT will collect more photons than present telescopes, thus increase the possibilities considerably.