bluuebunny/crossref_metadata_2025 huggingface dataset:
Data and Data Retrieval in Space Astronomy
Authors: Vette J.I.
Published: July 2016

To illustrate the range of storage and retrieval facilities and data products that are involved in space astronomy, the present situation on data from some instruments on the following missions is presented: Small Astronomy Satellite-B, Orbiting Astronomical Observatory 3, High Energy Astrophysics Observatory 2, International Ultraviolet Explorer, Viking Orbiter, and Solar Maximum Mission. In addition the Coordinated Data Analysis Workshops conducted at the National Space Science Data Center are outlined to demonstrate the usefulness of building a problem-oriented on-line data base from instruments flown on a number of spacecraft and operating from ground-based facilities.
Numerical data documentation in physics in the Federal Republic of Germany
Authors: Ebel G.
Published: July 2016

Owing to the ever-increasing number of publications it has become more and more difficult for scientists to find physics data relevant to their respective activities in the primary scientific and technical literature. With the exception of their special field of research they have to rely on data compilations. In many fields of physics, however, such data compilations do not exist or do not fulfill the requirements of the users, either because they are out of date or because they are published in places that are not well known. This unsatisfactory situation has been confirmed by an inquiry performed by the German Physical Society in 1972.
Progress Report on the Performance of the Multiple Mirror Telescope
Authors: Beckers Jacques M. , Ulich Bobby L.
Published: July 2016

The MMT utilizes a number of most unusual features many of which will probably be included in future advanced technology telescopes. We report here on the performance of these unconventional functions as we have determined them until now.
Optical System for the University of Texas 7.6m Telescope
Authors: Tull R.G. , Barnes T.G. , Dittmar D.N. , Ray F.B. , Pearson Earl
Published: July 2016

As presently conceived, the large telescope now being planned at The University of Texas will have a Ritchey-Chrétien configuration, f/13.5, with a 7.6m diameter f/2 primary of ultra-thin construction, on an alt-azimuth mount.

In this paper we will describe the current concept for the mounting, the building, mirror handling techniques, and the optical system. We will give preliminary results of the finite element flexure analysis of the mirror on its support system.

Studies have demonstrated a workable concept and have shown that there exists a method of adequately supporting an ultra-thin mirror against gravity and wind loads. We are continuing these studies, including also thermal effects on the mirror figure, in order to determine the best choice of mirror material and construction at the most reasonable price.
A 6-metre Polar-viewing Telescope
Authors: Gajur E.B.
Published: July 2016

The construction of a 6 metre polar-viewing telescope has been proposed (Karachentsev and Gajur, 1979), based upon the use of the paraboloidal primary mirror installed originally in the 6m BTA at Zelenchukskaya and later replaced by a mirror of improved performance. The mirror would be mounted with its axis in a fixed orientation pointing to the celestial pole and observations would be made at the prime focus using instrumentation mounted on a pylon. Object tracking is then performed by rotation of the detector around the point which represents the “image” of the celestial pole. In particular, the polar axis may coincide with the optical axis of the system.
Aerodynamic and Thermal Problems Around and Inside a Dome and Telescope
Authors: Rösch Jean
Published: July 2016

Much effort has been spent at Pic-du-Midi, with increasingly large telescopes, to reduce the instrumental causes of image deterioration and take best advantage of local atmospheric conditions. With the new 2-meter reflector, specifically intended for high resolution imaging, the concept has been, ideally, to separate three air-masses: outside, inside the tube, and inside the dome. As a first step, no parallel plate of required size and quality being available, the tube is open to the outer air, but a connection between tube and dome aims at preventing the dome-air flowing across the light-beam. Results and expectations are presented.
The Performance of Ground Based Telescopes
Authors: Brown D.S.
Published: July 2016

The paper identifies causes of degradation of image quality in astronomical telescopes, describes how the effects of these can be calculated using MTFs, considers the validity of multiplication of MTFs for this purpose and gives the results of measurement of external and dome seeing, system MTF and image quality obtained during the commissioning of UKIRT.
Multi-Order Formats to Increase the Versatility of Cassegrain Spectrographs
Authors: Harmer Dianne L.
Published: July 2016

“Grism” and compound prism cross-dispersers have been proposed for the new Cassegrain spectrograph of the 2.5m telescope at La Palma. The RGO image-tube spectrograph has been fitted with a grism to provide us with experience in designing layouts, operating the equipment and handling the data.
Transit Telescope Designs Optimized for Multiple Object Spectroscopy with Fibers
Authors: Angel J.R.P.
Published: July 2016

Instruments to study simultaneously the spectra of many objects in the field of view of a telescope can be made with the aid of fused silica fibers. The spectrograph at the 2.3m telescope of the University of Arizona has been modified for such operation, and is used routinely to investigate the dynamics of clusters of galaxies (Hill et al. 1981). The system presently in use locates up to 40 fibers in the telescope's Cassegrain focal plane, with the aid of plates previously drilled with holes in the configuration of the objects to be studied. Each field must be set up by hand by inserting fibers into a hole plate. An obvious improvement to this method would be to mount each fiber on a mechanical actuator, so new field configurations can be set up by remote control. It is our intention to make such a system with 32 fibers for the 2.3m telescope, over the next two years.
Optical Designs of Plane Aspherized Grating Spectrographs
Authors: Richardson E.H.
Published: July 2016

Spectrographs using plane aspherized gratings have excellent resolution over a wide field and require one less element than a conventional Schmidt or Maksutov camera. However, they are restricted to configurations where the grating is approximately normal to the camera axis.
High Angular Resolution with Rotation Shearing Interferometers: Preliminary Results and Future Potentials
Authors: Roddier F. , Roddier C.
Published: July 2016

Compared to speckle-interferometry, amplitude-interferometry has the following advantages:

(1)

The amplitude of the object Fourier components is insensitive to both turbulence and telescope induced aberrations, permitting an accurate calibration of visibility curves,

(2)

Interferograms are free from speckle noise, permitting a better signal-to-noise ratio on bright sources,

(3)

Information can be retrieved from fewer exposures (including complete image reconstruction),

(4)

Accurate visual measurements of stellar diameters and of the angular spacing of binary stars can be easily performed.
A High Resolution Fourier Transform Spectrometer for the Cassegrain Focus at the CFH Telescope
Authors: Maillard Jean P. , Michel G.
Published: July 2016

A high resolution interferometer (60cm maximum path difference) for use from the visible region to 5μm has been designed and manufactured at Meudon Observatory to be part of the instrumentation of the Canada-France-Hawaii Telescope. The considerations which led to the choice of the interferometer being operated at the Cassegrain focus, and the design features which allow this to be achieved, are outlined.
Solid State Imagers for Astronomy
Authors: Latham David W.
Published: July 2016

This is a summary of the meeting “Solid State Imagers for Astronomy” held at the Harvard-Smithsonian Center for Astrophysics in June 1981. The main emphasis of this report is a comparison of the performance characteristics of the CCD detectors now in use.
Stellar perturbations on comets
Authors: Remy F. , Mignard F.
Published: July 2016

The stochastic processes involved in the evolution of a hypothetical cloud of comets are investigated. The cloud is assumed to be randomly perturbed by passing stars approaching the Sun at distance less than 1 pc. Within the frame of the impulse approximation we derive analytical expressions for the probability distribution of the impulse imparted to comets for both close and distant approaches. An application to the rate of ejection of comets is presented.
Errors in numerical integrations and chaotic motions
Authors: Milani A. , Nobili A.M.
Published: July 2016

The methods to estimate the integration errors, including the effects of truncation, rounding off, and instability of the solutions, are discussed. Polynomial error accumulation depends upon numerical method, stepsize, orbital period and also eccentricity; it is also machine dependent. Comets correspond to the most difficult case of exponentially diverging orbits; however they can be very close to resonant ordered regions.
The past orbit of comet Halley and its meteor stream
Authors: Hajduk A.
Published: July 2016

The present paper studies the structural features of the meteor streams associated with Comet Halley deduced from the observations of its meteor showers, as check points of orbital elements in a deeper history of the comet orbit. Libration of the argument of perihelion of the comet and the corresponding displacement of the nodes, as recognized in the distribution of condensations within the stream, allows to estimate the maximum lifetime of the comet in the inner Solar System at about 2 × 105 years.
Ground-Based Observations of Near Ecliptic Zodiacal Light Brightness
Authors: Misconi Nebil Y. , Weinberg J.L.
Published: July 2016

Ground-based observations of the evening zodiacal light taken by Weinberg and Mann from Mt. Haleakala, Hawaii, during March 1966 are used to derive a table of zodiacal light brightnesses at high spatial resolution (as little as 0.5° in differential ecliptic longitude λ−λ⊙ and 1.0° in ecliptic latitude β) over the region 29. 5°< λ−λ⊙ < 56°, −30°< β <30°. Significant differences are found in the brightness distributions above and below the ecliptic plane.
The Change in Near-Ecliptic Zodiacal Light Brightness with Heliocentric Distance
Authors: Toller G.N. , Weinberg J.L.
Published: July 2016

Background starlight observed by the Pioneer 10 Imaging Photopolarimeter from beyond the asteroid belt is used to isolate zodiacal light in Pioneer observations at heliocentric distances R between 1 and 3 AU. Near-ecliptic zodiacal light brightness data in the range 65° to 180° elongation ε are used to depict changes in the shape of the zodiacal light with ε and R and are compared to the corresponding views seen from the Earth and from the Helios 1 and 2 spacecraft.
On the Solar Dust Ring(s)
Authors: Mukai T.
Published: July 2016

Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grain alone. Preliminary analysis on the recent infrared data of F-corona by Maihara et al.(1984) has suggested that the ring particle has different physical properties compared with the dust grains, which produce the background F-corona.
Interpretation of F-Corona Radial Velocity Field
Authors: Shestakova L.I.
Published: July 2016

The radial velocities of F-corona for total eclipse July 31, 1981 obtained at elongations (3-7) R⊙ are interpretated assuming prograde motion in circular Keplerian orbits of circumsolar dust. In computations isotropic plus diffraction scattering functions are used. In supposition of silicate grains the best coincidence with observations is received for grains with radii about 0.4 μm with the presence of dust free zone (d.f.z.) around the Sun to heliocentric distances (6.5-14) R⊙ and high grain concentration at the edge of this dust free region.

The presence of negative radial component of radial velocities can be explained by falling of the matter into the Sun under influence of Poynting-Robertson effect of solar wind for porous grains with radii less than 0.4 μm . The effect of radiation drag for these small grains is essentially less. Using grains with radii less than 0.4 μm the sizes of which decrease as approaching to the Sun one may explain the inner F-corona brightness.
Interferometric Observation of the F-Corona Radial Velocities Field Between 3 and 7 R⊚
Authors: Shcheglov P.V. , Shestakova L.I. , Ajmanov A.K.
Published: July 2016

During the July 31, 1981 solar eclipse, F-corona interferograms near MgI λ 5184 Å were obtained using a Fabry-Perot etalon (FPE) with an FWHM of 0.5 Å (corresponding to 30 km/sec) and an image tube. Radial velocities Vr of the interplanetary dust (i.d.) were measured in different directions.

Both prograde and retrograde motions of i.d. in the ecliptic region is discovered. Most of velocity values do not exceed 50 km/sec. A negative velocity component appears after averaging all Vr for all directions. Its average increases to − 20 km/sec toward the Sun. Some ejections are observed. The strongest (+ 130 km/sec) is located at the north ecliptic pole at a distance of 6 to 7 R⊙.

From the lack of unshifted Fraunhofer lines in the scattered sky light, we conclude that the sky brightness continuous component is predominant and its source is K-corona scattered light in the Earth’ s atmosphere.
The Motion of Interplanetary Dust Particles
Authors: East I.R. , Reay N.K.
Published: July 2016

Radial velocity measurements on the solar MgI 5183.618Å Fraunhofer absorption line in the Zodiacal Light spectrum have been made with a microprocessor-controlled servo-stabilised Fabry-Perot interferometer. Observations were made at 5 and 10 degree intervals in the ecliptic plane between morning and evening elongations of 25 degrees. These new data are of much greater precision and coverage than any previously obtained. Obtained over a two year period, the observations show a consistent evening/morning asymmetry in the radial velocity curve with the Gegenschein receding from the Earth at 4 Km/sec. These data do not support the hypothesis that the majority of interplanetary dust grains are in hyperbolic trajectories.
Orbits of Interplanetary Dust Particles Inside 1 AU as Observed by Helios
Authors: Grün E. , Fechtig H. , Kissel J.
Published: July 2016

The in situ dust detectors on board the Helios spaceprobes detected impacts of micrometeoroids between 0.3 AU and 1 AU distance from the sun. Among the measured quantities were mass, impact speed and flight direction of the dust particles. Radial variations of the flux, azimuthal distribution and impact speed are discussed. Significantly different results were obtained for the “apex” particles observed by both ecliptic and south sensors and for the “eccentric” particles detected only by the south sensor. The radial spatial density variation of the “eccentric” particles is compatible with that derived for zodiacal light particles. Whereas the spatial density of “apex” particles peaks at 0.5 to 0.6 AU. From the measured quantities probability distributions of orbital elements were derived for the observed micrometeoroids. About 60% of the observed micrometeoroids (“apex” particles) are on low energy orbits (a ≲ 0.6 AU). About 30% of the particles (“eccentric” particles) had high energy orbits (a ≳ 0.9 AU). More than 10% of the observed particles show high probabilities for travelling on hyperbolic orbits.
Calibration of the Galileo/ISPM Dust Detectors with Iron Particles
Authors: Göller J.R. , Grün E.
Published: July 2016

The impact-ionization-detectors for the Galileo-/ISPM-Missions were calibrated using about 7000 iron particles with speeds between 1 km/s and 67 km/s and masses between 10−15 g and 2 × 10−10 g. These calibrations showed that the impact charge (Q) was proportional to the particle mass (m) at a fixed velocity. The speed dependent charge yield (Q/m) showed significant deviations (up to one magnitude) from a power law.

There are three independent methods (risetimes of electron and ion pulses, amplitude ratio between channeltron and ion pulse) for measuring particle speed and two possibilities (charge yields of electron and ion pulses) for mass measurement. This calibration showed that the speed can be determined within a factor of 1.2 and the mass within a factor of 2.0.
An Empirical Penetration Equation for Thin Metallic Films Used in Capture Cell Techniques
Authors: Carey W.C. , McDonnell J.A.M. , Dixon D.G.
Published: July 2016

The problem in the determination of impact particle parameters from hypervelocity impact damage on a foil or multilayer structure is one which deserves close attention in the era of ready access to recovered space impact events. In the MFE experiment (McDonnell et al 1984), we chose metallic foils, and this paper addresses the decoding of perforations in metallic foils, primarily of aluminium of typical dimensions 5 μm (hard temper rolled). Data is examined to establish for the first time a penetration relationship which extends over:

1.

marginal and thin sheet perforation;

2.

velocities varying from some 2 to 69 kms−1

3.

particle densities varying from some 1 g cm−3 (ices?) to 7.8 g cm−3 (iron?)
Collection of Cosmic Dust: Past and Future
Authors: Brownlee D.E.
Published: July 2016

The collection of cosmic dust began in the middle of the last century with the recovery of spheres from the ocean floor and from Greenland ice (Murray and Renard 1891). The occurence of native metal in some of the deep sea spheres was the first clue that they were extraterrestrial. The deep sea spheres were described as “chondres” and their origin was attributed to the atmospheric melting of meteors. Polar ice and the ocean floor sediments often contain only minor amounts of magnetic terrestrial particles > 100μm and in these sites it is possible to collect rather large magnetic extraterrestrial particles that fell in historic times. In the intervening century an extensive series of particle searches were carried out in nearly all likely types of terrestrial collection sites. These included glaciers, islands, beaches, deserts, lakes, rooftops, rainwater, and all levels of the atmosphere up to low Earth orbit. Most of these efforts were not successful in collecting particles that were later proven to be extraterrestrial. In addition to the earlier deep sea and polar work, successful recoveries were made from a beach sand, a desert, and the stratosphere. All of these efforts are described in an excellent review by Hodge (1981).
A Method for Deriving the Mean Volume Scattering Phase Function for Zodiacal Dust
Authors: Hong S.S.
Published: July 2016

A linear combination of 3 Henyey-Greenstein phase functions is substituted for the mean volume scattering phase function in the zodiacal light brightness integral. Results of the integral are then compared with the observed brightness to form residuals. Minimization of the residuals provides us with the best combination of Henyey-Greenstein functions for the scattering phase function of zodiacal dust particles.
Laboratory Results on Polarization Properties of Elongated Particles and Comparisons to Dust in the Tail of Comet Ikeya-Seki (1965 VIII)
Authors: Gustafson Bo.Å.S.
Published: July 2016

Data obtained through microwave analog measurements are used to compare optical polarization characteristics of silicate particles ranging in shape from spheroids and cylinders to chains of spheres. It is confirmed that the dependence of the degree of polarization on scattering angle is a powerful indicator of particle shape. The reversal and steep gradient in the degree of polarization found by Weinberg and Beeson (1976a,b) in the dust tail of comet Ikeya-Seki (1965 VIII) is suggestive of laboratory measurements corresponding to 1.6 μm long, 0.4 μm in diameter silicate cylinders.
Optical Models of the Three Dimensional Distribution of Interplanetary Dust
Authors: Giese R.H. , Kinateder G. , Kneissel B. , Rittich U.
Published: July 2016

Several models of three dimensional distributions of the interplanetary dust number densities are compared with observational values. It is shown that a comparatively satisfying fit can be achieved by distributions similar to the “Sombrero-Model” of Dumont and that multilobe models as recently proposed by Buitrago et al. can be rejected due to discrepancies with rocket photometry of the inner zodiacal light.
Plans for Release of Simulated Interplanetary Materials into Low Earth Orbit
Authors: Strong I.B. , Brownlee R.R. , Farnum E.H. , Huebner W.F. , Kunkle T.D. , Stephens J.R. , Bode M.F.
Published: July 2016

A number of experimental releases into low earth orbit of small, but detectable, quantities of very fine particulates are planned for the next several years. The principal materials are chemically and physically similar to those generally assumed to be the major constituents of interplanetary and circumstellar dusts (silicates, silicon carbide, graphitic materials). Later releases will include multi-phase releases of non-volatile particulates and volatile ices, simulating cometary material. Both ground-based and Space-Shuttle-based observations will be made in the visible and infra-red to study particle-plasma interactions, cometary physics and cloud dynamics in orbit.

Since opportunities for observing the behavior of such well-characterized materials in space are likely to be rare, and the effective duration of significant concentrations will be very short, we wish to have early input from the scientific community so as to maximize the scientific return. We will be receptive to all suggestions including collaborations in making the observations.
On Two Mechanisms of X-Ray Generation in Comets
Authors: Ibadov S.
Published: July 2016

The intensity of solar X-radiation scattered by a comet is calculated and compared to the proper X-radiation of the comet due to impacts of cometary and interplanetary dust particles. Detection of X-radiation of dusty comets at small heliocentric distances (R ≤ 1 a.u.) is found to be an indicator of high-temperature plasma generation as result of grain collisions.
Dynamics and Spatial Distribution of Interplanetary Dust
Authors: Leinert Ch.
Published: July 2016

Three attempts to explain the radial power law distribution n(r)~r−1.3 of interplanetary dust are reviewed, which include the influence of Poynting-Robertson effect, collisions and interplanetary magnetic fields. Electromagnetic forces are unlikely to affect appreciably the spatial distribution. The replenishment of the cloud of interplanetary dust by the disruption of larger meteoritic particles in catastrophic collisions appears to give the most natural explanation for the observed spatial distribution.
Possible Distributions of Some Orbital Elements of Interstellar Particles in the Solar System
Authors: Belkovich O.I. , Potapov I.N.
Published: July 2016

Distribution of eccentricities, perihelion distances of interstellar particles and their concentrations in the Solar system have been computed in the assumption that their velocities are similar to ones of the nearby stars of late spectral classes. More than 75% of orbits have eccentricities not exceeding the value 1.1 and concentration of particles at the Earth’s orbit 3.5 times greater than in the interstellar space.
Interpretation of Electric fields in Coronal Magnetic Loops
Authors: Foukal P. , Landman D.
Published: July 2016

Stark effect detected in high Balmer lines emitted from flares, prominences, and quiet chromosphere is generally interpreted as pressure broadening in a plasma of relatively high density. But a recent study of post-flare loops indicates that the densities of order 1012 cm−3 required to explain the observed Balmer line broadening are an order of magnitude higher than values derived using other plasma diagnostics such as Thomson scattering and Balmer line emission measures (Foukal, Miller, and Gilliam 1983). The disagreement might be explained as the difference expected between the true local density (measured by the Stark effect) in the obviously inhomogeneous loop plasma, and the straight mean or root mean square densities measured by Thomson scattering and line emission measures. More interestingly, the disagreement might imply a macroscopic electric field generated by, e.g., plasma waves in coronal magnetic loops.
X-Ray Satellite Lines
Authors: Dubau J.
Published: July 2016

Satellite lines are typical features of X-ray spectra. They correspond to radiative transitions involving an inner-shell vacancy. The most studied satellite lines are of the - type, i.e., (ls–2p) transition.

With the advent of Space Astronomy, X-ray spectra emitted by very hot solar plasma have been obtained. By a simple comparison of different spectra, it appears that, for highly ionized atoms, some satellite lines have intensities as large as resonance lines intensities and, more particularly, this is the case for the ls2n. – ls 2pn satellite lines of the 1s2 – ls2p resonance lines.

The analysis of the different population mechanisms responsible for the satellite lines and resonance lines emission has shown that different spectroscopic diagnostics could be derived from line ratios only if atomic data of great accuracy were available. There exists nowadays different atomic data programs adapted to X-ray satellite lines. They have in common to give a great amount of data simultaneously: wavelengths, autoionization and radiative transition probabilities. They take into account correlation and relativistic effects.

After tackling the simple 3-electron system, the programs give now appropriate data for more complex systems but this required large computers because the lines become blended. It is therefore impossible to limit the calculation to the most intense lines.
Supra Thermal Electron Tails Effects on X-Ray Line Emission in a Tokamak Plasma
Authors: Bartiromo R. , Bombarda F. , Giannella R.
Published: July 2016

The soft X-ray lines emitted by highly ionized impurities are one of the most prominent spectral features of today’s tokamaks. In fact the hydrogen isotope plasmas produced in these devices attain temperature values ranging from about one to several keV. A great deal of information about the plasma conditions can be drawn, in particular, from the highly resolved spectra of medium-Z ions which are very rich in satellites excited via dielectronic recombination and innner shell excitation (Dubau and Volontè 1980, Bitter et al. 1979).
Ultraviolet Spectroscopy of Cool Stars from IUE
Authors: Jordan C. , Judge P. , Johansson S.
Published: July 2016

Observations of cool stars with the IUE satellite have shown that although main sequence stars have uv spectra similar to that of the sun, the spectra of the giants and supergiants are dominated by lines of neutral atoms and singly charged ions. The atmospheres of the low gravity stars are greatly extended and there is a large opacity in the stronger lines. This leads to multiple scattering and the appearance of many transitions through line ‘leakage’.

A review is given of how high resolution IUE spectra have allowed line identifications to be established and some current problems are discussed.

The spectroscopic diagnostic techniques for the low gravity, low density atmospheres are also briefly outlined.
Soft X-Ray Spectroscopy with Exosat
Authors: Mewe R.
Published: July 2016

With the 500 and 1000 l/mm transmission gratings aboard the European x-ray Observatory SATellite (EXOSAT) we have measured medium-resolution (Δλ 5 A at 100 A) spectra of some ten objects of various categories such as isolated white dwarfs, cool stars with convective mantles, cataclysmic variables (e.g. AM Her) and a high-luminosity X-ray source (Sco X-1).

The Instrument configuration was mostly such that one low-energy telescope was used as a photometer, while the other telescope was used as a spectrometer with the 500 l/mm grating inserted.

The white dwarf spectra were measured between about 60 and 300 A. They show a continuum with no clear evidence of aborption and emission lines except for the He II absorption edge at 227 A in the spectrum of Feige 24. For the cooler (28 000 K) white dwarf Sirius B the emission is peaked between about 100 and 160 A and limited to about 200 A. which can be expected from atmospheric model spectra of DA white dwarfs. The soft X-ray emission of the hotter (> 60 000 K) DA white dwarfs (HZ43. Feige 24) is also interpreted in terms of photospheric emission. In the HZ43 spectrum the absorption edge is apparently absent which sets a stringent upper limit to the abundance ratio He/H of about 10−5. On the other hand the spectrum of Feige 24 shows a dominant absorption edge, implying He/H > 10−3. Moreover, here the shape of the continuum may be indicative of a stratification of element abundances in the outer atmosphere.
X-Ray Spectroscopic Measurements of Non-Equilibrium Ionization in Supernova Remnants
Authors: Markert T.H. , Canizares C.R. , Pfafman T. , Vedder P. , Winkler P.F. , Pradhan A.
Published: July 2016

When a cool plasma is shock-heated to X-ray temperatures, the ionization structure does not attain its final, equilibrium value immmediately, but proceeds toward it through electron-ion collisions with a timescale τ ≡ net of order 1012 cm−3 sec. For supernova remnants (SNRs), where 0.1 ≤ ne ≤ 10 cm−3 typically, the time required to achieve collisional ionization equilibrium (CIE) can be greater than the age of the remnant. Even if the SNR is quite old, that part of the remnant which is emitting most of the X-rays may have been shocked relatively recently, so that the assumption of CIE may be inappropriate (see below).

The question of ionization equilibrium is of great astrophysical importance in the study of SNRs because it affects the deduced values of their masses and elemental abundances (e.g. Shull 1982). Mass determinations are affected because underionized plasma generally has a much higher emissivity in soft X-rays than equilibrium plasma. Unless this is accounted for, the deduced value of the density and therefore of the mass, will be considerably overestimated.
High Resolution EUV & Soft X-Ray Spectrometers Using Variable Groove Spacings
Authors: Lampton M. , Hettrick M.C , Bowyer S.
Published: July 2016

Spectroscopic analysis is a powerful technique for the diagnosis of temperatures and compositions of astrophysical plasmas. The EUV (100–1000Å) and soft x-ray (10–100Å) bands contain hundreds of potentially useful diagnostic lines. Unfortunately, traditional types of grating spectrometer become inefficient or unwieldy when adapted to stellar spectroscopy onboard a spacecraft. At grazing incidence, the required length of a high-resolution plane-grating spectrometer can easily exceed the length of the telescope feeding it. For these reasons, we have systematically explored ways to introduce a reflection grating into the converging beam formed by a given objective optical system ahead of its first focus. A spectrometer of this type results in an optical train no longer than the telescope’s existing prime-focus beam.
The Measurement of Branching Ratios of Spontaneous Radiative Transition Probabilities for Be-Like Ions N IV and O V
Authors: Lang J. , Hardcastle R.A. , Spurrett P.H.
Published: July 2016

In an experiment to measure emission line intensities from the Belike ion Ne VII (Lang 1983), the intensity ratio I(2s3s3S−2s3p3P)/I(2p23P−2s3p3P) was found to be a factor six larger than predicted from the ratio of the theoretical spontaneous radiative transition probabilities (A values). Indeed, to reconcile the Ne VII experiment and theory in several respects it was suggested also that in Be-like C III the theoretical ratios I(2s3s1 S−2s3p1P)/I(2p21D−2s3p1P) was about a factor three too low.

The same apparatus was used to measure A value ratios in Be-like N IV and 0 V. Briefly the 40 kJ θ-pinch plasma source was viewed radially using a m Ebert and a l m grazing incidence photoelectric spectrometer. The m Ebert was intensity calibrated from 7300 Å to 3600 Å using a tungsten filament lamp, and from 3800 Å to 2500 Å using a deuterium lamp, both lamps having been calibrated by NPL. As described fully by Lang (1983), the branching-ratios method was used to calibrate the front exit slit of the grazing incidence instrument in the wavelength range 88 Å to 500 Å. Only Li-like line pairs of those listed in that paper were used with the addition of the C IV doublets 2s2S−3p2P (312.4 Å) and 3s2S−3p2P (5801.33 Å, 5811.98 Å). The H-like ion He II 1–4 transition (243.0 Å) and 3–4 transition (4685.7 Å) were used to cross-check the calibration. As shown in the figure, the He II result agrees excellently with the calibration as defined from the Li-like lines.
Study of Electron Capture in the N5+-He, H2 Collisions by UV Spectroscopy
Authors: Druetta M. , Cotte P.H.
Published: July 2016

The physics of multicharged ions has considerably developped during the last few years. Aside from its fundamental interest and its motivation for fusion research with Tokamak devices where charge exchange involving highly charged impurities are important, this new effort in this direction is due to the development of new sources of highly charged ions.

We report results concerning spectroscopic study of radiative transitions observed during the collision between multicharged N5+ ions with a helium or molecular hydrogen target. Nx+ ions are produced with the E.C.R. ion source in Grenoble (Geller and Jacquot 1981). The N5+ ions are then selected with two 168° bending magnets and finally sent into the target chamber where they collide either with He or H2 gas. Spectra are observed with a grazing incidence (82°) spectrometer equipped with photon detection.
High Spectral Resolution Observations of Coronal X-Ray Emission from the RS CVn Binary Sigma Corona Borealis
Authors: Riegler G.R. , Agrawal P.C. , Markert T.H.
Published: July 2016

Results of a high spectral resolution observation of the RS CVn binary σ Cr B, made with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory, are reported. A spectral scan in the 800–840 eV interval shows clear presence of an X-ray emission line at 826 eV identified with the 1S0 − 1P1 transition of Fe XVII. A prominent peak at 1007 eV in the scan band 987–1013 eV is attributed to a blend of lines due to Fe XVII and Fe XXI. Using the observed line fluxes and the Raymond-Smith model, best fit values of corona temperature and volume emission measure, with associated 90% confidence level uncertainties, are derived to be (6.9 ± 0.8) × 106 K and (1.7 ± 0.7) × 1053 cm−3, respectively. Pressure and density of the X-ray emitting plasma and loop length are deduced by applying a Constant Pressure Coronal Loop Model.
Measurement of Wavelengths and Abundances from Solar Flare X-Ray Spectra
Authors: Seely J.F. , Feldman U. , Doschek G.A.
Published: July 2016

The measurement of transition energies in highly charged ions represents an important test of quantum electrodynamics (QED) in strong fields. The OED contributions to the hydrogenic transition energies increase as (αZ)4, where α is the fine structure constant and Z is the atomic number. Transitions in hydrogenic ions of sulfur, chlorine, argon, and iron have previously been measured to a precision of 100 ppm or better. These measurements are in satisfactory agreement with accurate calculations of the energy levels, and this confirms the calculation of the QED contributions to the energy levels of one-electron ions.
The Effect of Resonances on the Excitation Rates for the Ions of the He-Like Isoelectronic Sequence
Authors: Faucher P. , Bely-Dubau F. , Dubau J.
Published: July 2016

The Helium-like-resonance intercombination and forbidden lines (ls21S−ls2p 1P, ls21S−ls2s 3P, ls21S−ls2s 3S respectively) can be observed from hot, low density plasmas such as coronal or tokamak plasmas. They can be used either to measure the electron temperature from the ratio of their intensity to that of the corresponding satellite lines (1s2nℓ′ − ls2ℓnℓ′) as described by Gabriel (1972) or directly as a density diagnostic (Gabriel and Jordan, 1972). The soft X-ray spectra obtained from these plasmas have been observed from space satellite experiments such as the Solar Maximum Mission (Acton et al., 1980), Hinotori (Tanaka et al., 1982) and P78–1 (Doschek et al., 1982) or from tokamaks such as PDX, PLT (Princeton, USA), TFR (Fontenay-aux-Roses, France). The analysis of some of these spectra, for example, Mg XI (Faucher et al., 1983), Ti XXI (Bely-Dubau et al., 1982b) and Ca XIX (Bely-Dubau et al., 1982a, Jordan and Veck 1982) show that these diagnostics are sensitive to the accuracy of the atomic data.and demonstrate the need for improved calculations of the excitation rates for the He-like ions.
Proton-Induced Fine-Structure Transitions
Authors: Zygelman B. , Dalgarno A.
Published: July 2016

Experimental studies of the intensity of the (2pl/2-lsl/2) and (2p3/2-lsl/2) lines of SXVI in the Alcator Takamak show large departures from the statistical ratio of 0.5 (Källne et al. 1982). Similar enhancements in the intensity ratio have been reported in solar observations (Grineva et al. 1973, Phillips et al. 1982) for the Mg XII lines and in laser produced plasmas (Boiko et al. 1977). Theoretical calculations of the intensity ratio have been carried out by Vinogradov et al. (1977), Beigman et al. (1979) and Ljepojevic et al. (1984) . We suspect that proton-impact induced transitions play a crucial role which depends sensitively on the conditions of temperature and density in the Plasma. In this abstract we will present some preliminary results of proton-impact excitation cross section calculations, for the n=2 sub levels of hydrogenic ions.
Charge State Distribution Measurement in an ECR-Discharge by VUV-Spectroscopy
Authors: Marlinghaus E.H. , Wiesemann K.
Published: July 2016

The charge state distribution of multiply charged Ar ions in an electron cyclotron resonance (ECR) heated microwave discharge (Bernhardi et al. 1976) was measured by means of VUV-spectroscopy in the wavelength region λ ≤ 100 nm (Marlinghaus 1984). Ion densities were computed from absolute line intensities in a modified corona model. Assuming electron impact excitation of groundstate ions to play the major role and neglecting all other processes leading to excitation, the ion density nz is given by
XUV and Soft X-Ray Radiation from Laser Produced Plasmas as Laboratory Spectroscopic Sources
Authors: Gohil P. , Ginter M.L. , McIlrath T.J. , Kapoor H. , Ma D. , Peckerar M.C.
Published: July 2016

Laser produced plasmas have been shown to be excellent sources for applications in the XUV and soft X-ray spectral region. We are using a 550 mj, 25 ns (FWHM) ND:YAG laser operating at a repetition rate of 10 Hz to produce plasmas above rotatable solid targets. The focal spot of the laser beam with a 31 cm lens was measured to be 170 μm (approximately twice the diffraction limit), using a diode array having a 170 μm resolution. Broadband output in the soft X-ray region was studied using a windowless PIN photodiode with an A1203 surface covered with a polyethylene filter with transmission between 44 Å and 120 Å. Results are presented for the source’s soft X-ray intensity for several elements as a function of laser energy, focus and driving wavelength, as are preliminary results using the source for high resolution spectroscopy and for soft X-ray lithography.
X-Ray Measurements from the Tandem Mirror Experiment-Upgrade (TMX-U)
Authors: Silver E.H. , Clauser J.F. , Failor B.H.
Published: July 2016

We report the results of X-ray emission measurements made at various plasma locations in the Tandem Mirror Experiment-Upgrade (TMX-U). By manipulating the electron and ion density profiles within the magnetic mirror end cells, a local minimum in the axial electrostatic potential creates a barrier that thermally isolates central cell electrons from those in the end cells. This thermal barrier makes it possible to heat end cell electrons to a temperature (~1.6 keV) that is significantly higher than the central cell value (30 to 200 eV), thereby increasing the ion confining potential. Formation of this potential peak is attributable, in part, to mirror-trapped hot ions (8 keV) that are injected as beams of neutral particles. The resulting ion density profile exhibits two symmetric peaks at the locations of the ion turning points and a depression where the magnetic field is a minimum. Electron cyclotron resonance heating (ECRH) is applied at the density minimum and produces a population of hot, mirror-trapped electrons (20 to 200 keV). It reduces an already depressed electrostatic potential to establish the thermal barrier. In addition, ECRH applied at the outer density peak raises the -ion confining potential and enhances central cell ion confinement by increasing the end cell electron temperature. X-ray measurements are made with solid state and scintillation detectors at the ECRH locations. Medium resolution spectra are obtained over a broad energy band and have proven to be an important tool for determining the efficiency of thermal barrier formation. We present our initial findings from these non-Maxwellian plasmas.
Population of Excited States of Al10+ in a Plasma by a Time-Dependent Model
Authors: Guennou H. , Sureau A.
Published: July 2016

The present model is the time-dependent version of a previous model (Sureau et al. 1983) in which the population distribution was assumed in steady state. A finite set of levels is partitioned in four subsets: the Z-ion ground-level and, contingently, the first near-degenerated levels (subset 1); all the successive excited Z-ion levels up to n=5 (subset 2); a finite number of higher Rydberg levels (because of the limitation of the series in the plasmas) which are assumed in LTE with the Z+l−ion ground-level (subset 3, called the thermal band); and the Z+l ion ground-level (subset 4).

The physical processes explicitly considered are the radiative cascades and the transitions between the Z-ion bound levels induced by electron-ion collisions. The radiative-transition probabilities are given by ab-initio calculations using a modified Hartree-Fock method including the spin-orbit interaction (Sureau et al., 1984). The collision rates are derived by the Van Regemorter formula multiplied by an adjustable parameter Fc.
X-Ray Spectroscopy of Laser-Produced Plasmas
Authors: Kauffman Robert L.
Published: July 2016

Laser-produced plasmas have some of the highest temperatures and densities obtainable in the laboratory. This offers the opportunity to perform spectroscopic studies in new temperature and density regimes under controlled laboratory conditions. Temperatures can range from greater than 1 keV to less than 1 eV, while densities range from less than 1020e−/cm3 to greater than 1023e−/cm3. X-ray spectroscopy has been an important tool in diagnosing these large ranges of temperature and density. Relative line intensities of resonance and satellite lines can be used to diagnose the lower densities and higher temperatures. (Galanti and Peacock 1975, Boilo et al. 1979) For the denser plasmas Stark broadening is a good density diagnostic. (Yaakobi et al. 1977) Absorption spectroscopy measuring edge shifts had recently been used to probe the low temperature, high density region. These plasmas, with their high-energy density, are transient with total time scales ranging from 100 psec to greater than 1 nsec, depending on the laser driver pulse. In order to make detailed measurements from these plasmas, sensitive, time-resolved spectrographs have been developed. (Lewis et al. 1980, Kauffman et al. 1983) These spectrographs can measure time histories of spectral lines with resolving powers of 300 or greater and with time-resolutions of 20 psec. By using such instruments, studies of the dynamics of the plasma can be made.
Opacity Broadening as a Density Diagnostic for Spot Spectroscopy
Authors: Apruzese J.P.
Published: July 2016

Recently, a novel technique known as spot spectroscopy has been developed for use in diagnosis of laser-produced plasmas. This method involves the implantation of tracer microdots (circular or rectangular) of material in laser targets whose composition and size (typically about 100 μm) are known. Aluminum has been a popular choice since its K-shell lines are readily produced; however, any element appropriate to the experiment may be chosen. A major advantage of this technique is that the plasma produced from each microdot is generally homogeneous in the direction parallel to the plane of the original target. Since the dots can be distinguished spectroscopically, the diagnosis of each spot is not subject to the ambiguities created by the presence of gradients. Gradients do exist in each blowoff tracer perpendicular to the target plane; however, it is possible to resolve spatially the cylindrical blowoff created by each dot with appropriate orientation of the spectrograph slit.
A High-Resolution VUV Spectrometer With Electronic Parallel Spectral Detection
Authors: Cromer C.L. , Bridges J.M. , Lucatorto T.B. , Roberts J.R.
Published: July 2016

We demonstrate a new high resolution grazing incidence spectrometer system for spectroscopic applications in the range 50 to 400 Å. The instrument is comprised of a laser-plasma VUV continuum source, a 1.5 m grazing incidence spectrometer, and a 1024-channel VUV optical multichannel analyzer (VUV-OMA). The VUV-OMA is of new design, featuring a special resolution-enhanced channel electron multiplier array in an overall configuration chosen to optimize the spatial resolution of the detector while maintaining single-photoelectron sensitivity. The instrument has the capability of bringing the advantages of linear response and parallel spectral detection to general VUV photoabsorption studies of atoms, ions, molecules, and thin solid samples, as well as studies involving laboratory plasmas. The instrument has the additional special capability of performing time resolved absorption spectroscopy of transient species. The characteristics of the source and detector, along with various applications of the instrument to atomic physics will be discussed.
The Optical Radiation of Supernovae
Authors: Harkness Robert
Published: July 2016

Most of our knowledge of supernovae comes from studies of their optical radiation. Very high quality optical spectra have been available for several years now. The new data have aided the development of theoretical models of supernova explosions, particularly Type I events, which until recently, were very poorly understood. Type II explosions, which are believed to arise from core collapse in massive stars (Woosley, this volume;, produce optical spectra which can be simply interpreted in terms of a nearly blackbody continuum with prominent lines of hydrogen superimposed. The Type II atmosphere is of near solar composition, expanding at a characteristic velocity of 5000 km/s and at least bears some resemblance to a more familiar stellar atmosphere. Type I supernovae produce a much more violent expansion and the optical spectrum cannot be so easily accounted for. The progress made in the last few years stems mostly from the work of David Branch (Branch 1980,1981; Branch et. al. 1982,1983,1985). His synthetic spectra for Type I’s showed that the spectrum can be explained in terms of the resonance lines of mostly singly ionised metals. The lines are formed in matter moving with a bulk velocity of about 11,000 km/s and at a characteristic temperature of approximately 10,000 K. Furthermore, Branch concluded that the density profile in this region should be relatively steep and that the matter was very deficient in hydrogen and helium. As we shall see, this description fits very well with the hypothesis that Type I supernovae originate in the incineration of white dwarfs. Following the focus of recent developments this discussion will be mainly limited to the early evolution of Type I models of this kind, although many of the important features of the radiation transport are directly relevant to Type II explosions.