bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Radial Pulsation Models of the H-Alpha Profile in BW Vulpeculae
Authors: Odell Andrew P.
Published: July 2016

The profile of the Hydrogen alpha spectral line in the large-amplitude Beta Cephei star BW Vulpeculae was modeled in terms of a linear, non-radially moving, and rotating stellar atmosphere. The pulsation and rotation parameters were derived from fitting the radial velocity amplitude, and the best fit was obtained for l=2, m=-2, i=90°, rotation velocity=120 km/sec, and pulsation amplitude=27 km/sec. When the line profiles are compared to this model, the fit is quite encouraging for most phases, but several discrepancies remain. At the time of writing, it is not clear whether tliese can be made to disappear by increasing the sophistication of the model, or whether a completely different physical model (e.g. radial) is necessary.
Mode Discrimination in Nonradially Oscillating Stars From Light, Colour and Velocity Observations
Authors: Balona L.A. , Stobie R.S.
Published: July 2016

Expressions for the amplitudes and phases of the light, colour and radial velocity variations are derived for a star in nonradial oscillation. For stars in the cepheid instability strip the spherical harmonic mode of the oscillation can be obtained from the phase difference between the light and colour variations. For 3 Cep stars the mode can be estimated from the amplitude ratio of the light and colour variations.
Double-Mode Cepheids
Authors: Stobie R. S.
Published: July 2016

As their name implies double-mode (or beat) cepheids form a subgroup of cepheid variables which appear to be pulsating simultaneously in two modes. From the period ratio of the two frequencies, the modes have been identified with the fundamental and first overtone modes of radial pulsation. Petersen (1973) was the first to establish that the two periods can be used to determine the masses and radii of these stars independent of any other knowledge such as luminosities, effective temperatures or gravities. The masses derived by this technique are 2 to 3 times lower than the expected evolutionary masses, given that these stars are normal population I cepheids. It is this result that has stimulated much of the subsequent research on double-mode cepheids.
HR 7308: A Unique Cepheid+
Authors: Percy John R. , Evans Nancy Remage
Published: July 2016

We have obtained photometric observations and radial velocities of the F6I-IIb star HR 7308. The spectral type, the period (1d.49), the relative range and phase of light, colour and velocity variations all suggest that the star is a small-amplitude Cepheid. The metal abundance appears to be normal. However, the light amplitude decreased slowly during 1978 from 0m.3 to 0m.1, and increased during 1979 and 1980 from 0m.05 to 0m.15. Such behaviour is unprecedented in a population I Cepheid.
Ultra-Short Period Cepheids in the LMC
Authors: Connolly Leo
Published: July 2016

Six Cepheids in the Large Magellanic Cloud have been discovered with periods less than one day. They lie at the faint, blue end of the instability strip as would be expected but form a separate Period-Luminosity relation from that for normal Cepheids. Membership in the LMC is based upon the existence of the P-L relationship. Several of the variables have uncertain periods although all apparently have periods under one day. One additional variable has tentatively been identified as a bright Anomalous Cepheid.
Bump Masses and Radii of BL Herculis Variables
Authors: Petersen Jørgen Otzen
Published: July 2016

Bump masses and radii are derived for 18 BL Her stars from the observed bump phase and the accurately known fundamental period. The mean mass M/M⊙ = 0.60 ± 0.09 agrees precisely with predictions from standard stellar evolution theory and gives a new test of the theoretical models. The derived radius of V553 Centauri is in good agreement with the radius recently determined by an independent modified Baade-Wesselink method by Balona. Finally, a preliminary discussion of possible continuations of the BL Her bump progression is given.
Core Collapse, Bounce and Shock Propagation
Authors: Bowers Richard L. , Wilson James R.
Published: July 2016

Recent developments in the physics input for iron core collapse models of type II supernovae are reviewed. The effect of these developments on collapse calculations is also discussed. The inner core collapses homologously, with little change in specific entropy, bounces in the neighborhood of nuclear density, and sets up; an outward moving shock. In adiabatic models an explosion may result. The inclusion of neutrino effects may produce substantial shock damping. Current results indicate that core collapse, bounce and shock propagation does not produce an explosion when neutrino effects are included.
White Dwarf Models for Type I Supernovae and Quiet Supernovae, and Presupernova Evolution
Authors: Nomoto Ken’ichi
Published: July 2016

Supernova mechanisms in accreting white dwarfs (WDs) are presented, i.e., the carbon deflagration as a plausible mechanism for producing Type I supernovae and electron captures to form quiet supernovae leaving neutron stars. These outcomes depend on accretion rate of helium, initial mass and composition of the WD. The various types of hydrogen shell-burning in the présupernova stage are also discussed.
White Dwarf Pulsations: A Review
Authors: McGraw John T.
Published: July 2016

The DA white dwarfs are those which show only the Stark-broadened lines of hydrogen in their spectra. They comprise about 80% of the total white dwarf population. A subset of the DA dwarfs, the ZZ Ceti stars, form a highly homogeneous class of nonradially pulsating variable stars. In this paper we shall review the observations from which both the physical properties of the stars and the characteristics of the pulsations have been derived. Data obtained since the last review of these variables (Robinson 1979) is stressed, as these data are forcing a somewhat revised understanding of the ZZ Ceti stars and their relationship to investigations of white dwarfs and to pulsating variable stars, in general.
The Effect of a Magnetic Field on Stellar Pulsations as a Singular Perturbation Problem
Authors: Goossens M. , Biront D.
Published: July 2016

The perturbation problem that describes the effect of a weak magnetic field on stellar adiabatic oscillation is considered. This perturbation problem is singular when the magnetic field does not vanish at the stellar surface, and a regular perturbation scheme fails where the magnetic pressure is comparable to the thermodynamic pressure. The application of the Method of Matched Asymptotic Expansion is used to obtain expressions for the eigenfunctions and the eigenfrequencies.
An Introductory Review of our Present Understanding of the Structure and Composition of Uranus’ Atmosphere
Authors: Belton Michael J. S.
Published: July 2016

Measurements of the gross properties of Uranus are enough to show that it is a planet with quite unique characteristics. The best estimates of its radius (24900 km; Danielson, Tomasko and Savage, 1972) and of its mass (14.54 Earth masses; Klepczynski, Seidelmann and Duncombe, 1970) imply an interior structure and overall composition that set it clearly apart from Jupiter and Saturn (Hubbard and MacFarlane, 1980).
Meteorology of the Outer Planets
Authors: Hunt Garry E.
Published: July 2016

One of the fundamental problems in atmospheric physics is concerned with providing improved weather forecasts for the Earth and predicting the future climate of our planet. However, this is a particularly difficult task since the meteorology of the Earth is affected by a wide range of physical factors - clouds, oceans, continents, polar caps, deserts and forests - all of which respond differently to ‘the solar energy which drives the weather systems. In addition, external factors, such as the changing energy from the sun, are thought to strongly influence the Earth’s meteorology. To provide a broader understanding of atmospheric phenomena, detailed studies of planetary atmospheres have been conducted, since they provide a unique opportunity to investigate these basic problems in fluid dynamics under boundary conditions which are quite different from those found on the Earth.
IUE Data Distribution
Authors: Heck André
Published: July 2016

The IUE project is described, with special emphasis on the IUE data management and archive retrieval.

This paper briefly describes a more specific data center providing also a service to the astronomical community, or more precisely a group of data centers dedicated to a given instrument.

This instrument is the IUE ( International Ultraviolet Explorer) launched on Jan. 26, 1978 and collecting since then spectral images of all kinds of celestial objects in the ultraviolet wavelength range.
Retrieval of astronomical information from Padova-Asiago Observatory plates archives
Authors: Benacchio Leopoldo
Published: July 2016

This paper shortly describes a software procedure for the on line information retrieval from astronomical plates archives. The procedure is active in Padova Asiago Observatory and will be improved linking them with other retrieval and graphic procedures acting on astronomical catalogues.
Design of the 4.2m Herschel Telescope and Instruments
Authors: Murdin Paul
Published: July 2016

The UK Science and Engineering Research Council (SERC), through the Royal Greenwich Observatory (RGO), is installing on the island of La Palma, a 4.2 m altazimuth telescope, as part of the Observatorio del Roque de los Muchachos, at an altitude of 2300 m in the Canary Islands. The telescope, known as the William Herschel Telescope, is fully designed and manufacture has begun. It is due for completion in the mid-1980's. The telescope, dome and instrument design have all interacted with one another, particularly in the search for economy. Among the proposed instruments is a novel collimator-less spectrograph.
A Coronographic Mode for Large Telescopes
Authors: Courtes G. , Lamy Ph. , Mauron N. , Saisse H.
Published: July 2016

The study and efficiency test of the optics of the Space Telescope Faint Object Camera carried out at the Laboratoire d'Astronomie Spatiale, led the authors to design a similar coronographic mode for large ground based telescopes. Adaptation of this design to the Mount Chiran 1 meter and E.S.O. 3.6 meter Ritchey-Chrétien telescopes has given new levels of performance in the detection of faint features in stellar and planetary observations.
Recent Progress with Multi-Anode Microchannel Array Detector Systems
Authors: Timothy J. Gethyn
Published: July 2016

The Multi-Anode MicroChannel Arrays (MAMAs) are a family of photoelectric, photon-counting array detectors that are being developed specifically for use in instruments on space-borne and ground-based telescopes. In this paper we review briefly the construction and modes of-operation of the MAMA detectors and describe the current development status of the different detector systems.
Application of the Electronographic Image Converter for Spectroscopy at the 2.6m Reflector of the Crimean Astrophysical Observatory
Authors: Petrov P.P.
Published: July 2016

An Electronographic Image Converter (EIC) of the “Spectracon” type is being used for routine spectroscopic observations at the 2.6m reflector of the Crimean Astrophysical Observatory. Some details of the EIC and film-loop applicator are given and the spectrophotometric accuracy and detective quantum efficiency are discussed.
First Results with an Electronographic Camera Used at the Prime Focus of the C.F.H. Telescope in Hawaii
Authors: Picat J.P. ,   Groupe Caméra
Published: July 2016

First results have been obtained with an electronographic camera used at the prime focus of the C.F.H. Telescope in Hawaii. The camera is briefly described. It is an electronic camera with a new technological design and a tight valve allowing the recovery of the nuclear plates without destroying the photocathode. Some preliminary results are given.
The transition between long period comets, short period comets and meteoroid streams
Authors: Hughes David W.
Published: July 2016

It has long been realised that Jovian perturbation is the dominant cause of the transition of long period comets (Period > 200 yr) into short period ones (P < 200 yr). When the differences in the detectability of comets in the two groups are taken into account it is clear that the present day flux of long period comets is sufficient to provide the present collection of short period comets in the inner solar system.

The fact that meteoroid streams are produced by decaying short period comets was first recognised around 1866 (see Hughes 1982a). The magnificent display of Leonids in that year enabled the radiant position and time of maximum rate to be easily calculated. Assuming the orbital period to be 33.25 yr Le Verrier (1867) and Schiaparelli (1867) published orbits for the meteoroid stream. The orbit of comet 1866 I, which had been discovered by Guillaume Tempel, from Marseilles on December 19, 1865 and independently by Horace P. Tuttle from Harvard, Massachusetts on January 5, 1866, has been calculated and published by Oppolzer (1867a). Almost to a man Peters (1867), Schiaparelli (1867) and Oppolzer (1867b) realised that the comet and the stream had similar orbits. Since that time many more examples have been put forward, two famous ones being the Perseids and comet Swift-Tuttle (1862 III) and the Eta Aquarids and Orionids both of which have comet Halley (1910 II) as their parent. For more details see Cook (1973).
The long-term evolution project
Authors: Carusi A. , Kresák L. , Perozzi E. , Valsecchi G.B.
Published: July 2016

The Long-Term Evolution Project (LTEP), realized in collaboration by the IAS-Reparto di Planetologia (Rome, Italy) and the Astronomical Institute of SAV (Bratislava, Czechoslovakia), has been developed with the aim of giving a general insight into the dynamical evolution of short-period comets. The motion of all the known short-period comets has been investigated over a long time span (over 800 years) taking care, as far as possible, to eliminate the sources of possible discrepancies within the computations. An internally consistent data-set and an atlas of orbital evolutions are the first outputs of this project. The main characteristics of the LTEP are discussed, together with some general remarks on its importance for cometary studies, its limitations and the future developments.
One of the problems of long-term integrations of cometary orbits
Authors: Carusi A. , Perozzi E. , Pittich E.M. , Valsecchi G.B.
Published: July 2016

One of the problems of the numerical integrations of cometary orbits is that of their numerical stability. For those bodies which undergo close encounters with the giant planets the problem has a specific feature. Apart from the numerical instability of integrations in the mathematical sense, there is an additional source of instability due to the inaccuracy of initial data, i.e. the orbital elements. An example of this case is presented in this paper by the numerical integration of the motion of comet P/Shajn-Schaldach over an interval of 368.4 years, within which six close encounters with Jupiter occurred. The inaccuracy of the starting orbital elements of this comet is modelled by changes in the last digit of each element of the central orbit, determined by the set of the best orbital elements. In the process of integration, eight model orbits experience differential perturbations with respect to the central orbit. The numerical instability, caused by the inaccuracy of starting orbital elements and represented by the dispersion of these orbits, tends to increase abruptly beyond each encounter with Jupiter. It is shown that, with the attainable accuracy of the osculating elements representing the observations, one or two approaches to within 1 AU from Jupiter can make the orbit entirely indeterminate.
Review of studies on capture of comets by neptune and its role in the dynamic evolution of cometary orbits
Authors: Kazimirchack-Polonskaya E.I.
Published: July 2016

A historical review of investigations on encounters of minor bodies with outer planets is presented. The dominating role of Jupiter in the capture of comets and in determining their secular evolution is emphasized. Participation in the above process of Saturn, Uranus and, especially, Neptune is investigated. In the present paper are considered five fictitious comets, penetrating into the depths of Neptune’s sphere of action, where they undergo large orbital transformations and capture by Neptune. Two near-circular orbits are transformed into elliptical ones, their perihelia being moved inside the planetary system; one hyperbolic orbit is transformed into a transplutonian one, another into a typical short-period orbit of the Neptune’s family with a perihelion accessible to terrestrial observers. One fictitious comet is captured by Neptune as a stable satellite.
The problem of the 1/a-distribution and cometary fading
Authors: Bailey M.E.
Published: July 2016

The background to the problem of explaining the frequency distribution of cometary 1/a-values is briefly reviewed and it is emphasised that the explanation in terms of the Oort Cloud model relies on an ad hoc fitting function - the fading/disruption probability per revolution. Assuming an underlying steady-state Oort Cloud and the integral equation formalism developed by Oort and Yabushita to predict the 1/a-distribution for an arbitrary fading probability, we have been able to constrain the unknown fading function by comparison with observations. In agreement with previous work we find that the tendency for fading or disruption should be strong at small 1/a-values and weak at large 1/a-values. The mean fading probability per revolution, k(x), is found to lie within a factor roughly of order 2 about k(x) ≈ 0.3(1+(x/4 × 10−3)2)−3/2, where × is 1/a in units AU−1. A physical model for fading which might qualitatively account for this behaviour is tentatively proposed. This depends on the thermal shock experienced by a long-period comet nucleus around perihelion passage. It is emphasised that until a viable model for fading has been found, the validity of the steady-state primordial hypothesis remains unresolved.
Nongravitational forces on comets: the first fifteen years
Authors: Marsden B.G.
Published: July 2016

The recent and current situation with regard to our analysis and understanding of the nongravitational effects in cometary motions is reviewed. Comets can be categorized according to the different physical situations that may exist in their nuclei. Further experimentation with theoretical models and empirical fits to observations is encouraged.
The selection of comets for future space missions
Authors: Yeomans D.K.
Published: July 2016

The criteria used to select a short period comet for possible future rendezvous space missions are stated and the selection process is outlined. For the time period 1900 - 2000, several candidate comets offer opportunities for spacecraft rendezvous. Two of the best candidates are periodic comets Kopff and Wild 2.
Zodiacal Light, Gegenschein and Sky Background
Authors: Maucherat A. , Llebaria A. , Gonin J.C.
Published: July 2016

Results from photometers on board the D2B satellite (1975) for the whole sky in ultraviolet and blue light, are combined to generate a very well defined empirical representation of the zodiacal light and Gegenschein. The sky background is then obtained by subtraction of this model from the data.
Some Remarks on the Density of Interplanetary Dust Grains
Authors: Lamy P.L.
Published: July 2016

The relevance of the bulk density as a physical parameter characterizing interplanetary dust grains is discussed. The various measurements which lead to a determination of this parameter are reviewed. The specific case of the collected interplanetary dust grains is considered.

The bulk density of interplanetary dust grains has been and is still a matter of controversy. This quantity cannot, in general, be directly measured; it is used to relate the mass and the size of a grain. This duality stems from physics itself as there are interactions sensitive to the mass (e.g., gravitational forces) while others are sensitive to the size or the cross-section (e.g., light scattering, radiation pressure, gas and plasma interactions). The measuring technics of the grains reflect this duality as, for instance, impact sensors are generally sensitive to the kinetic energy and thus to the mass, while optical sensors are sensitive to the cross-section. One sees that the density is not strictly speaking the relevant parameter, but what is needed is a relationship between mass and average cross-section.
Cosmic Ray Exposure Age Determinations of Cosmic Spherules from Marine Sediments
Authors: Yamakoshi Kazuo
Published: July 2016

The cosmic ray exposure ages of deep sea metalic lie spherules were determined by various methods; low level countings (Ni-59), neutron activation analysis (Mn-53), high energy accelerator mass spectrometry (Be-10, Al-26) and mass spectrometry (K isotopes). The exposure ages of 0.3 - 50 Ma were obtained. According to Poynting-Robertson effect, the starting points (supplying sources) are located at inner region of the orbit of Saturn.
Cosmic Spherules, Asteroid Collisions and the Solar Constant
Authors: Parkin D.W.
Published: July 2016

In 1980 (Phil. Trans. Roy. Soc. 297, 495) and in 1983 (Geophys. Jour. Roy. Astr. Soc. 75, 473) it was proposed that cosmic spherules are formed as splash ejecta in asteroidal collisions. The Poynting-Robertson effect size-sorts the spherules as they spiral to Earth in circular orbits. The time taken in My is given by

Δt = 3.5 × 10−7 Dδ (a2 − 1)

where a (in AU) is the collision distance from the Sun, D (in um) is the diameter of the spherules and δ (in kg/m−3) its density. In the 1983 paper, we tested the hypothesis by plotting the size of all the iron spherules (≥ 43 μm diam.) against time for two dated N. Pacific cores. Sloping lines, giving a ~ 2.1 AU, could be discerned; but their existence could be disputed - see figure 6.

In current work, all the spherules from core V21-65 have been cracked open to find δ. Out of 220 spherules, 65 have rusted metal globules and these (Dδ) points give a confused plot, because of inaccurate δ-values. However, 66 spherules have their metal globules well preserved. Since globule diameter and %Ni can be accurately measured, δ can be calculated. These (Dδ) points show two sloping lines with some clarity, giving a ~ 3.4 AU; also, there are vague lines, giving a-values well within the main asteroid belt.

To establish the hypothesis, wide cores are needed, giving an abundance of undamaged spherules. To obtain accurate a-values, the Robertson formula requires correction because of the spherule’s “hummocky” oxide surface. Also, any waviness in the sloping lines could be a measure of a variable solar constant.

A new kind of iron spherule was found because of the cracking; 13 enclose opaque beads of true glass (rich in Fe, Ni and Si, no Mg) instead of metal globules. Crushed bits are deep ruby-red and nonmagnetic.
Cometary Dust and the Periodicity of Rainfall Singularities
Authors: Kviz Z.
Published: July 2016

Periodicity in rainfall singularities in the U.S.A. corresponds to the periods of two comets whose orbits are sufficiently close to Earth’s orbit. These effects are connected with the position of a stratospheric jet stream over the territory of the U.S.A. This investigation indicates that some processes, so far not properly understood, could be responsible for the influence of cometary dust on the triggering of atmospheric precipitation.
Optical Detection of Large Meteoroids in Space
Authors: Zook H.A. , Potter A.E.
Published: July 2016

CCD sensors placed across the focal plane of large Schmidt telescopes have great potential for detecting and measuring the very low flux in space of meteoroids with diameters larger than 1 meter. With the Palomar “Big Schmidt”, a detection rate of 1.4 per hour is obtained for meteoroids between 0.6 and 200 meters in diameter. For the Baker-Nunn “Satellite Tracking Camera”, the corresponding rate is about 0.8 per hour. The key to obtaining such high detection rates derives from approximately setting the sensor integration time equal to the time it takes a meteoroid to cross a pixel field of view. This minimizes signal to noise problems and is accomplished, in practice, by multiple summing of short integration time data records to obtain data records of longer effective integration times.
Meteoroid Orbits Determined by Southern Hemisphere Radar
Authors: Steel D.I. , Baggaley W.J.
Published: July 2016

A radar meteor orbit facility of novel design has been developed at the University of Canterbury. Synchronous digital noise averaging,impulse suppression and meteor echo recognition using a microprocessor system, along with high gain antennas, allow a limiting radar magnitude of about +13 to be achieved, making this the most sensitive meteor orbit radar to’ date. An exhaustive survey of faint sporadic meteors will be carried out, along with an investigation of the little-known Southern showers. Since the observatory is ideally located with respect to the Eta Aquarid radiant, a programme of observations during the Comet Halley perihelion epoch is planned.
Dust-Plasma-Gas Interactions in the Heliosphere
Authors: Fahr H.J. , Ripken H.W.
Published: July 2016

Several, different forms of how neutral gases and dusty media can interact with a plasma have been discussed in the Literature. Common to all of these interactions is that they in principle lead to changes in both the composition and dynamical state of all interacting media. The most important scenarios in the heliosphere involving these kinds of interactions are described in this paper. Special emphasis is placed on the solar wind interaction with the zodiacal dust. In regard to the dust, this leads to severe complications with respect to its dynamics due to the plasma Poynting- Robertson effect and due to Lorentz scatterings. As for the plasma, this causes the appearance of dust-generated neutrals and secondary ions. An influence on the plasma dynamics, at least in the present solar system, can be neglected. The surface chemistry of the plasma-dust reactions is described in some detail here, and the densities and fluxes of exotic, dust-generated ions not originally belonging to the coronal solar wind are calculated. Observabilities of these neutrals and ions are investigated and it is discussed how physical, chemical, and dynamical parameters of the zodiacal dust cloud could be derived from these observations.
Computer Calculation of Collision Cascades by Energetic Particles Penetrating Dust Grains
Authors: Rössler K. , Eich G.
Published: July 2016

The penetration of energetic particles from stellar winds, cosmic rays and fast moving gas clouds in interstellar dust grains induces a variety of physical and chemical changes. Detailed information on penetration ranges, number of secondary projectiles produced by knock-on and their energy distribution is obtained from computer simulation of collision cascades with the program MARLOWE. Model targets are polycrystalline H2O-ice, NH4Cl, and SiO2, projectiles are lo2 - lo4 eV H, He, and C. Depending on the energy and the projectile/ target mass ratio up to lo2 secondary projectiles are created per primary impact with energies ranging from a few to some lo3 eV. In composite grains, condensed gases and ice mixtures the energetic secondaries can undergo hot chemical reactions leading to a series of precursors for larger organic and biomolecules.
A New Approach to Evaluate Planetary Perturbations on a Cloud of Dust in Low Eccentricity Heliocentric Orbits
Authors: Gustafson Bo. Å. S.
Published: July 2016

Dynamical perturbations on ensembles of particles in heliocentric orbits of low eccentricity are integrated over time. The dust is perturbed by radiation pressure, Poynting-Robertson drag, their corpuscular counterparts, and by gravitation due to any number of planets. A dust cloud is represented by a set of centroids and orbital dispersions (about the centroids). Gravitational perturbations on the centroid are derived from a single matrix, valid for any planet, in the appropriate frame of reference. After transformation of the time derivatives to a common coordinate system, the perturbation rates are summed up and integrated. The time dependence of the planets’ orbital elements are evaluated inside the time integral.
The Soft X-Ray and EUV Spectra of Solar Flares
Authors: Nishi K. , Tanaka K.
Published: July 2016

The Japanese solar maximum satellite HINOTORI was launched on 21 February 1981, and so far 720 Solar flares were detected including many large flares; the largest observed was a X12 class flare occurred on June 6, 1982. Unfortunately, the data recorder malfunctioned in June, 1982, since then the real time basis observation has been possible to continue. The general introductory explanation and some important results were already published in some proceedings (1, 2, 3 ), therefore we would like to focus on presenting some new results of the Soft X-ray spectra obtained by the spectrometers rather than on talking a review.
HRTS Ultraviolet Solar Spectroscopy
Authors: Dere K.P.
Published: July 2016

The NRL High Resolution Telescope and Spectrograph (HRTS) consists of a telescope, stigmatic UV spectrograph, UV broadband spectroheliograph and Hα film and video cameras. An image of the Sun is focussed onto the slit jaws of the spectrograph by a 30 cm Cassegrain telescope with a spatial resolution of 1". The stigmatic UV spectrograph employs a tandem-Wadsworth mount and photographically records spectra along the 1000" (1 solar radius) slit with a resolution of 50 mÅ in the 1170–1710 Å wavelength region. Images of the slit jaws in a tunable 100 Å bandpass are produced on film by the UV spectroheliograph which uses a reversed tandem-Wadsworth mount. The slit jaws are also viewed through an Hα filter by video and film cameras. To date, the HRTS instrument has flown on four rocket flights and is being prepared for flight on Spacelab-2.
Intensities in Complex Spectra of Highly Ionized Atoms
Authors: Klapisch M. , Bar-Shalom A. , Cohen A.
Published: July 2016

We describe a package of programs for the implementation of the collisional-radiative model to complex configurations. The number of levels taken into account may be several hundreds. The heart of the package is a very efficient program for excitation cross sections in the Distorted Wave framework, using the Relativistic Parametric Potential wave functions. The basic jj coupling scheme actually simplified the computations, enabling a useful factorization into radial and angular parts. Intermediate coupling and configuration interactions are accounted for. We computed ratios of intensities of 3d9 − 3d84s (E2) to 3d9 −3d84p (El) transitions as functions of ne and Te in Xe XXVIII and other Co-like spectra. The atomic model involves all the levels of configurations (3p6)3d9; −3d84s, −3d84p, −3d84d, −3d84f, and (3p5) −3d10, −3d94p. (275 levels) and all the transitions between them. Results compare very well with experimental spectra from TFR.
New Calculations of Inner Shell X-Ray Lines in Ti, Cr, and Ni as Density Diagnostics
Authors: Lemen J.R. , Phillips K.J.H. , Doschek G.A. , Cowan R.D.
Published: July 2016

We present new calculations for ls−2p transitions in C−, N−, and O-like Ti, Cr, and Ni for application to tokamak X-ray spectra. This extends our earlier work for the corresponding iron ions (Phillips et al. 1983, Ap.J. 265, 1120) in which a density dependence of line intensities was pointed out. These lines are principally formed by dielectronic recombination; the density effect arises due to the density-dependent populations of the fine structure levels in the ground configuration of the recombining ion. In the present work the calculations of the Ti, Cr, and Ni lines have been made for the wavelengths and the dielectronic recombination rates using a Hartree-Fock technique with statistical exchange. The density dependence of the collisionally excited transitions was also included. Density-dependent populations of the fine structure levels of the ground configuration were obtained from Feldman et al. (1980 J. Appl. Phys. 51, 190) and Bhatia et al. (1980, J. Appl. Phys. 51, 1464). In calculating the ionization fractions we have assumed coronal equilibrium; new ionization rate coefficients were calculated using the formalism given by Burgess and Chidichimo (1983). The spectra were synthesized with Voigt line profiles and typical tokamak radius-dependent temperature and density profiles were assumed. The N-like lines, in-particular show a strong dependence over tha range: <1011 −3.1013 cm−3 (Ti XVI) <1011 −3.1014 cm−3 (Cr XVIII), 1012 −1015 cm−3 (Ni XXII). If a density profile across the torus is available from Thomson-scattered laser radiation, observations of these lines may serve to show where the N-like ions are formed in the tokamak plasma.
Uv Spectra of Nebulae and Novae
Authors: Seaton M.J.
Published: July 2016

Optical spectra of nebulae and novae are dominated by recombination lines of H I, Be I and He II and by forbidden lines, such as those of [0 III]. Their IR spectra show the fine-structure lines and continua due to dust. Most of the lines observed in the UV (say from 3000 to 1200 Å) are either due to resonance transitions (e.g. C IV 1549) or are of intercombination type (e.g. C III] 1908). Some elements do not have many lines in the optical - nitrogen gives only [N II] and there are no forbidden lines of ionized carbon - and for such elements much valuable information is provided by UV lines (e.g. N III], N IV], N V, C II], C III] and C IV). Carbon/oxygen abundance ratios deduced from combined UV and optical observations agree well with those deduced from IR continuum features (Seaton, 1983).
The Proposed Columbus Mission: High and Low Resolution Spectroscopy in the 100–2000 Å Spectral Region
Authors: Linsky Jeffrey L.
Published: July 2016

For the past year a Joint Working Group of NASA and ESA scientists and engineers has been defining the scientific objectives and instrument parameters for a proposed satellite to obtain far and extreme ultraviolet spectra of stars, interstellar gas, solar system objects, and galaxies. The project, now called Columbus, incorporates the scientific goals of the previously proposed NASA Far Ultraviolet Spectrograph Explorer (FUSE) and ESA Magellan missions.

The prime spectral range of Columbus, 900–1200 Å, cannot be observed by IUE or Space Telescope. In this spectral range Copernicus was able to observe bright stars (mv ≤ 6) with high resolution and the Hopkins Ultraviolet Telescope (HUT) will observe faint sources at low resolution, but Columbus will be the first instrument capable of high spectral resolution observations of faint sources (mv ≈ 17). High resolution spectra in the 900–1200 Å region will permit studies of the Lyman lines of atomic H and D, the molecules H2 and HD, resonance lines of C III and O VI, and other species listed in Table 1. Columbus also is being designed to observe the 1200–2000 Å spectral region at high resolution, permitting measurements of many stages of ionization for the same atom (i.e. N I, II, III, V; C II, III, IV; and S II, III, IV, VI). The broad coverage of ionization states is essential for the analysis of interstellar and stellar plasmas where the ionization balance can be quite complex.
The Statistical Equilibrium of H and He and the H/He Ratio in WR Stars
Authors: Underhill A.B. , Bhatia A.K.
Published: July 2016

The mixed selection of strong emission lines present in the spectra of WR stars suggests that we are observing plasma with an electron temperature of the order of 105 K somewhere in the atmospheres of these rare stars. In the spectra of some WR stars emission lines of H are detected; this suggests that plasma with an electron temperature of the order of 104 K may be present also. Since the observations made in the last 30 years show that the masses, luminosities, effective temperatures, and general distribution in space of WR stars are similar to those of stars with spectral types in the range from about B2 to O9, a prime question is why are the spectra of WR stars so different from those of the B stars with which they are associated.
Distorted Wave Calculations: Application to Astrophysics and Tokamak Plasma
Authors: Bhatia A.K.
Published: July 2016

During the last few years, observations of solar phenomena have been carried out by rocket flights, manned satellites like Skylab, unmanned satellites like Orbiting Solar Observatories and more recently Solar Maximum Mission. The wavelengths, line intensities and line profiles in UV and X-ray regions of the solar spectra have been measured. The spectroscopic data obtained are of high spatial and spectral resolution. The goal is to understand the physical properties of the emitting plasma and determine the electron temperatures, densities and volume of the emitting plasma from UV and X-ray spectra.
Radiative Corrections to Intensities of Dielectronic Satellite Lines Emitted from Helium- and Lithium-Like Argon
Authors: Jacobs V.L. , Rogerson J.E.
Published: July 2016

The process of dielectronic recombination has been the subject of intense theoretical activity mainly because of the pioneering work by Burgess (1964), who demonstrated that this process can be the dominant recombination mechanism for multiply-charged atomic ions in low-density high-temperature astrophysical and laboratory plasmas. Recent attempts to measure dielectronic recombination cross sections and rate coefficients have renewed interest in the development of a rigorous quantum-mechanical theory of the resonant electron-ion recombination process. A precise theory is clearly required for the interpretation of the dielectronic satellite lines, which have been found to be of great value in the spectroscopic determination of temperatures, densities, and departures from ionization equilibrium.
Collision Strengths and Line Strengths for Transitions from the ls23ℓ, Levels to the ls2ℓ'3ℓ" Levels in Li-Like Ions
Authors: Sampson D.H. , Goett S.J. , Petrou G.V. , Clark R.E.H.
Published: July 2016

It is well known that radiation from the levels of the ls2ℓ2ℓ' and ls2ℓ3ℓ' configurations of Li-like ions form satellites of spectral lines from He-like ions that are of high interest for plasma diagnostic purposes. Recently Sampson et al (1984) have made calculations of the collision strengths for innershell excitation to these upper levels from the ls22s and ls22p levels for a large number of Li-like ions using a Coulomb-Born-exchange method. Here we consider the alternative mechanism for populating the ls2ℓ3ℓ' levels by collisional excitation from the ls23s, ls23p and ls23d levels. Although the poDulations of the ls23ℓ levels are lower than those of the ls22ℓ levels, this is at least partially compensated for by the fact that the collision strengths for the ls23ℓ − ls2ℓ'3ℓ" transitions are considerably larger on the average than those for the ls22ℓ − ls2ℓ'3ℓ" transitions. The method of calculation is the same as that used by Sampson et al (1984), where all possible configuration mixing, parentage mixing and intermediate coupling type mixing among the states in a complex (the states having the same n values, parity and J values) was included. Also the present application is sufficiently simple that after summation over J values for the initial level the results for the collision strength Ω can be expressed in a simple manner in terms of the Z scaled hydrogenic collision strengths Z2ΩH and analogous to Eqs (8)-(15) of Sampson et al (1984). The appropriate formulae and the numerical results for both excitation to upper fine structure levels and to upper energy terms for 19 Li-like ions have been submitted for publication to Atomic Data and Nuclear Data Tables. Here we give only the pertinent formula and sample numerical results for transitions between energy terms in Li-like iron. This formula is

where due to configuration mixing neither ℓ need equal ℓ" nor ℓa need equal ℓ'. The recommended values for σ and σe are zero for transitions involving ls−2s and are −0.5 and 0.3, respectively, for transitions involving ls−2p. Numerical values for the coefficients A and Ae for Li-like iron are given in Tables I-III. Values for Z2ΩH and for impact electron energies up to 15 times threshold are given in Golden et al (1981) and Clark et al (1982) and are repeated in Table IV for convenience. Finally we note that the line strengths S for transitions involving ls−2p are obtained by multiplying the corresponding value for A(ls−2p) by the scaled hydrogenic line strength 1.665 and dividing by (Z-σ)2.
Recent Laboratory Studies of Dielectronic Recombinations
Authors: Dunn G.H.
Published: July 2016

The breakthrough in 1978 by Brooks et al. and by Breton et al. provided the first plasma rate measurements on dielectronic recombination (DR), and their basic technique has been followed up on in a few other investigations. An important new plasma technique was introduced in 1982. Another breakthrough in 1982–1983 led to colliding beams cross section measurements for DR and to more direct comparisons with theory. Experiment/theory disagreements and agreements have led to follow-up experimental and theoretical efforts which are pointing to better understanding of DR and which emphasize issues that should be paid attention to by plasma modelers. An overview will be given with strong emphasis on the beams experiments and the implications.
Solar Coronal Fe XVII X-Ray Line Ratios
Authors: Rugge H.R. , McKenzie D.L.
Published: July 2016

The SOLEX bragg crystal spectrometer experiment on the P78-1 satellite (Landecker, McKenzie and Rugge, 1979) has been used to determine accurate flux ratios of several strong solar Fe XVII x-ray emission lines in the ~ 15 to ~ 17 Å wavelength region. The ratios chosen were selected because the lines used permitted an accurate determination of the ratios both from the aspect of counting statistics as well as the lack of interference from other lines of comparable strength. Observations for a variety of conditions of solar activity, ranging from quiet conditions to large solar flares, are presented. For these observations intensity variations of a factor of about 60 were observed for the Fe XVII lines. Variations of a factor of almost 800 were observed for the Fe XVIII line at 14.2 Å. The observed ratios of the Fe XVII lines are compared to the theories of Loulergue and Nussbaumer (1975) and Smith, Raymond, Mann and Cowan (1984).
Spectroscopic Diagnostics of the UV Emitting Plasmas in Solar Flares Observed from SMM
Authors: Cheng Chung-Chieh , Tandberg-Hanssen E.
Published: July 2016

The transition region exhibits dynamic changes during solar flares. To understand the energy release and transport processes in solar flares, it is important to determine observationally the physical conditions in the flare transition region plasmas, which emit in the UV wavelength ranges. During the Solar Maximum Mission (SMM) we observed many flares in the UV emission lines of Si IV (1402 Å) and 0 IV (1401 Å) using the Ultraviolet Spectrometer and Polarimeter (Woodgate et al. 1983). In this paper we present the Si IV/O IV flare observations, in particular the dynamic evolution of the transition zone plasmas (~ 105 K). We also studied the temporal and spatial correlations between the impulsive UV and hard X-ray bursts.
Measurement of the A-Value of the Intersystem Transition in Al II at 2670 Å: Å Progress Report
Authors: Johnson B. Carol , Kwong H.S.
Published: July 2016

Ratios of intensities of spectral lines produced in the radiative decay of collisionally-excited levels of atomic ions are versatile indicators of electron density in astrophysical plasmas when one of the lines involves a metastable level (see the review by Feldman 1981 and references therein). Radiative transition probabilities (A-values) and electron excitation cross sections are necessary for accurate, quantitative analyses of these plasmas. The work reported here is part of a program of measurements of astrophysically interesting A-values and radiative lifetimes (see the review by Smith et al. 1984); until we began, such anaylyses of astrophysical plasmas depended upon unconfirmed calculated A-values.
Relative Intensities of Lines in F I- B I-Like Ti, Cr, Fe, Ni, and Ge: A Comparison of Theory and Experiment
Authors: Stratton B.C. , Moos H.W. , Feldman U. , Seely J.F. , Suckewer S. , Finkenthal M.
Published: July 2016

Allowed 2s22pk − 2s2pk+1 transitions in the F I- B I-like ions of elements with Z ≥ 20 are often observed in spectra of high-temperature (Te ≥ 107 K) laboratory and astrophysical plasmas. Calculations of level populations in these ions are important in the interpretation of measured intensities of these lines for plasma diagnostics. Impurity ion densities and radiated power losses in tokamak plasmas, and the emission measure of astrophysical sources, can be derived from spectroscopic measurements using level population calculations. Certain line-intensity ratios can be used to measure the electron density in astrophysical plasmas; this technique may also be useful in some low-density laboratory plasmas. It is therefore important to experimentally check the level populations in high-Z ions using spectra from a well-diagnosed laboratory plasma, such as that of a tokamak. This has been previously done only for some transitions in Fe XVIII - Fe XXII (Suckewer and Hinnov 1979).
Atomic Potentials in Very Dense Aluminum Plasmas
Authors: Cauble R. , Gupta U. , Davis J.
Published: July 2016

The calculation of atomic properties is plasma is critically dependent on the form of the ion-electron interaction potential. In the case of weak collisions in a low density ionized gas, the screening of the ion under consideration by surrounding plasma is adequately described by the Debye-Hückel potential (see, e.g., Weisheit, 1983). If the plasma is very dense, the perturbation approximations leading to the Debye form break down and other techniques must be employed to incorporate additional correlative effects. The transition from classical to this strongly coupled plasma occurs when the parameter , where is the mean charge per ion, , and ro is the ion-sphere radius, is greater than about one.
Theoretical Calculation of X-Ray Emission from Laser-Produced Plasmas
Authors: Duston D. , Clark R.W. , Davis J.
Published: July 2016

The interaction of an intense short-wavelength laser beam with a solid foil target is a topic which has been studied vigorously for many years. Many inherent problems still exist, however, in our understanding of observed experimental data. In particular, the problem of transport through the target material of the deposited laser energy continues to be the focus of many investigations. Although most.of the work has been dominated by particle transport phenomena, it was shown in a previous paper that radiation processes and photon transport often play a major role in the redistribution of the deposited energy in laser driven plasmas. In this presentation, we continue our investigation of the role of atomic physics and radiative emission in laser-produced plasmas by studying the effects of these physical processes as a function of varying initial conditions for both aluminum and carbon foil targets.
Spectral Line Intensities for Δ N = 0 (L-Shell) Transitions of N, O, and F-Like Ions
Authors: Lee Y.T. , Reed K.
Published: July 2016

Many laboratories are actively investigating radiation spectra emitted from high temperature/high density plasmas produced using gas-puff Z-pinch machines and high power lasers. Spectral-line intensities from these plasmas can be useful temperature and density diagnostics. In a well-diagnosed plasma, information on the emission spectrum can also be used to test the accuracy of theoretical rate coefficients.

Recently time-resolved spectra from an oxygen-like argon plasma produced in a gas-puff z-pinch were measured in the wavelength range 150–200 Å . Over this wavelength range the spectrum contains mostly the Δn = 0 (L-shell) transitions in ArX-ArXIV and some weak transitions for n = 3 to n = 4 of ArVI-ArVIII. The measured spectra show the predominance of 0-like Ar L-shell transitions.