bluuebunny/crossref_metadata_2025 huggingface dataset:
The Solar Dynamo
Authors: Brandenburg Axel , Tuominen Ilkka
Published: July 2016

The traditionalαΩ-dynamo as a model for the solar cycle has been successful in explaining the butterfly diagram, phase relations between poloidal and toroidal field, and polar branch migration features. Observational and theoretical achievements in recent years have however shaken this picture. The current trend is towards dynamos operating in the overshoot region of the convection zone. Nevertheless, there are many open questions and a consistent picture has not been established. In this paper we compare recent approaches and discuss remaining problems.
Dynamo Action in Evolved Stars
Authors: Gray David F.
Published: July 2016

Evolved stars tell us a great deal about dynamos. The granulation boundary shows us where solar-type convection begins. Since activity indicators also start at this boundary, it is a good bet that solar-type convection is an integral part of dynamo activity for all stars. The rotation boundary tells us where the magnetic fields of dynamos become effective in dissipating angular momentum, and rotation beyond the boundary tells us the limiting value needed for a dynamo to function. The observed uniqueness of rotation rates after the rotation boundary is crossed can be understood through the rotostat hypothesis. Quite apart from the reason for the unique rotation rate, its existence can be used to show that magnetic activity of giants is concentrated to the equatorial latitudes, as it is in the solar case. The coronal boundary in the H-R diagram is probably nothing more than a map of where rotation becomes too low to sustain dynamo activity.
Long-term Polarimetric Activity of the Cool Supergiant μ Cephei
Authors: Arsenijević J. , Jankov S.
Published: July 2016

The intrinsic polarisation parameters P, θ, Q and U of the star μ Cep, in the V spectral region during the period 1979-1989, are presented. The data were obtained from the Belgrade polarimetric observational program. The polarization percentage of the star exhibits change is of about 2.5% during this interval and the position angles change by about 90 degrees. These very large long-term changes of polarization parameters are discussed briefly.
Ca II H High-Resolution Spectral Monitoring of Active Late-type Dwarfs
Authors: Beckman J. E. , López R. J.García , Rebolo R. , Crivellari L.
Published: July 2016

We have monitored Ca II H with a spectral resolution of 8 × 104, in asimple of late-type MS stars over a four-year period. The high resolution enables us to add information on velocity fields to the usual flux monitoring. We detect changes in wavelength of different parts of the Ca II H feature, which can be interpreted as velocity fields in the lower chromosphere, with downflow and upflow of order 0.5 km s−1, depending on the star. Flux variations in Ca II H emission can be ascribed, via velocity tagging, to long-term change in plage cover rather than short-term modulation by (incompletely sampled) rotation cycles.
The Onset of Chromospheres in A-type Stars: The Altair Affair
Authors: Catalano S. , Gouttebroze P. , Marilli E. , Ferrero R. Freire
Published: July 2016

Here we present preliminary results on the study of the chromosphere of Altair from Lα high dispersion profiles. We report also the detection of Lα chromospheric emission from α Cep (A7V) and β TrA (F0 V) with the IUE. We show that chromosphere may exist up to B – V = 0.22. The possible heating mechanism, magnetic or nonmagnetic, for the chromosphere of these stars is also discussed.
Ca II H and K Spectroscopy of ER Vul
Authors: Fernández-Figueroa M.J. , Armentia J.E. , de Castro E. , Cornide M. , Reglero V.
Published: July 2016

ER Vul (HD 200391) is a double-lined spectroscopic binary, at a distance of 45 pc, catalogued as a short-period RS CVn binary, and has been found to present eclipses. The components have spectral types G0V/G5V, masses 1.07/0.98 M⊙, radii 1.23/1.23 R⊙ and Mv 4.8/4.6m (Strassmeier et al., 1988, and references therein). The system presents emission reversals of the H and K absorption lines (Bond, 1970; Eggen, 1978), but no information on the character of these emissions has been previously reported.
On the Coronal Activity of RS CVn Systems
Authors: Demircan Osman , Derman Ethem
Published: July 2016

An analysis of the X-ray emission of a large sample of single MS stars shows that X-ray luminosity is strongly correlated with the photospheric radius (Fleming et al., 1989) which implies the dependence of activity on bolometric luminosity Lbol, effective temperature Teff, and thus stellar mass M (Micela et al., 1985; Bookbinder et al., 1986). The role of the emission area on the coronal activity of RS CVn systems has been noted independently by Majer et al. (1986), and Demircan (1986).

By using new data on some well known RS CVn systems, we produce new evidence that above idea is indeed valid. A plot of X-ray luminosity Lx versus (B – V) for the sample of well known RS CVn systems in Fig. 1 shows that cooler, long period, more evolved systems with larger surface area have stronger X-ray emission.
The Distribution of The Periods of the Hagnetic Variable Stars
Authors: Catalano F.A. , Strazzulla G.
Published: July 2016

The distribution of the periods of about 80 of the known variable Ap stars is studied in the framework of the oblique rotator model. It is shown that for the long period variables (P > 100 days) the oblique rotator has trouble in explaining the observed variations.
Kinematic and Dynamic Reference Frames
Authors: Gaposchkin E. M.
Published: July 2016

The fundamental properties of kinematic and dynamic reference frames are defined, first as an abstract concept and second in a practical (although idealized) thought experiment. A four dimensional spacetime description in coordinate free notation illustrates the properties, limitations, and relationships between kinematic and dynamic reference frames. Kinematic reference frames can be defined quite rigorously. Dynamic reference frames cannot be defined so well, but are nonetheless very useful. In practice a combination has been generally adopted. Presently we can materialize purely kinematic terrestrial and celestial reference frames.
The Theoretical Description of the Nutation of the Earth
Authors: Smith Martin L.
Published: July 2016

This talk was intended, I think, to be an opportunity to recite the conventional wisdom of the class of geophysicists who are interested in investigating theoretically the Earth’s wobble and nutation. It has become clear since the Kiev meeting in 1977, however, that we have not yet agreed upon the contents of our conventional wisdom and it would be premature, and presumptuous, of me to pretend to recite it. What I can do is to tell you what I think the conventional wisdom ought to be. In doing so I shall give free rein to my prejudices and little consideration to opposing points of view (they must speak for themselves). Nothing in this talk is noticeably original; virtually all of it is extracted from the work of others or from the folklore of this topic.
A New Parameterization of Polar Motion
Authors: Papo Haim B.
Published: July 2016

The rotational motion of the earth is decomposed into spin, polar motion and local motions. The rotation vector components are associated to phenomena such as precession, nutation, diurnal spin, polar motion and local motions. The above decomposition is accomplished without refering to an earth-fixed CIO pole or BIH zero meridian. The time-like variations of the coordinates of a surface point in a geocentric equatorial reference frame are presented as a function of the rotation vector components. In the rigid earth approximation three scalar parameters are necessary for evaluating point coordinate variations, namely spin rate of the earth, polar motion magnitude and spin rate of the polar motion vector. Two numerical examples are given as an illustration.
The Stellar Reference Frame from Space Observations
Authors: Murray C. A.
Published: July 2016

The HIPPARCOS Satellite, to be launched by the European Space Agency, will provide a stellar reference frame over the whole celestial sphere with an average accuracy of ± 0002 in each coordinate and component of annual proper motion, for some 100,000 stars.

The origin of coordinates will be arbitrary. Absolute rotation of the system of proper motions can be obtained by measuring quasars relative to stars in the HIPPARCOS catalogue, either with the NASA Space Telescope or by conventional ground based astrometric observations.
An Attempt to Compare the Radio Astronomical System of Coordinates of Quasars With FK4
Authors: Kumkova I. I.
Published: July 2016

A method of comparison of the FK4 system to a system based on extragalactic sources is tested on actual data for 140 sources observed by radio-interferometric and whose optical counterparts have positions referred to FK4. The difference of coordinates is analyzed in spherical harmonics series. The computation show that the method gives satisfactory results. However, the precision of the data prevents from any interpretation in terms of systematic errors of the FK4.
On Solar Type Protostars
Authors: Winkler Karl-Heinz A. , Newman Michael J.
Published: July 2016

The formation of a 1 M⊙ protostar in spherical symmetry has been followed in time dependent hydrodynamics with a detailed description of the equation of state and a careful treatment of radiative transport. The comparison of the dynamic evolution with observation is made in terms of the Hertzprung-Russell diagram. It is found that the evolution following from Larson’s initial condition produces quantitatively and qualitatively better agreement than that following from the initial condition of Hayashi, including the first appearance of the object as an infrared source. Of particular importance for a correct physical understanding of the formation process is an adequate description of the accretion shock. Pressure ionization and electron degeneracy effects are of increasing importance for the internal structure of lower mass objects.
Solar Pulsations (Review)
Authors: Hill Henry A.
Published: July 2016

Recent observational evidence on solar oscillations is reviewed; this evidence strongly favors the global interpretation for much of the observed spectrum. Implications of these observations for the study of the solar interior and atmosphere are discussed.
An Extended Work Integral for Pulsating Stars
Authors: Simon Norman R.
Published: July 2016

This paper contains a preliminary report on research aimed at extending the pulsational work integral to next highest order beyond the linear regime.

We begin by writing the integral in fully nonlinear form (Cox and Giuli 1968), normalized by the stellar luminosity L
The Light Curve Epochs of Supernovae Explosions
Authors: Falk S. W.
Published: July 2016

A brief description of the current state of knowledge for Type II light curves is given, including discussion of some of the remaining problems. The use of supernovae of both types as independent distance indicators is outlined and difficulties are pointed out. A summary of new ideas regarding the origin of Type I light curves is presented.
X-Ray Burst Sources - A Simple Two Zone Model
Authors: Buchler J. Robert , Barranco Manuel , Livio Mario
Published: July 2016

With the help of a very simple two zone model, we demonstrate the possibility of periodic thermal relaxation (limit cycle) oscillations in the helium burning envelope of accreting neutron stars. Physically reasonable model parameters can be chosen which yield agreement with the observed features of x-ray bursts and we suggest that this limit cycle is operative in neutron stars which have an accretion rate in a specific range. For hydrogen burning a similar cycle is possible, but it operates at such high temperatures that an unrealistically large accretion rate would be required.
A New Instability Strip for Hot Degenerates
Authors: Starrfield Sumner G. , Cox Arthur N. , Hodson Stephen W.
Published: July 2016

A completely new kind of variable star has recently been discovered (McGraw, et. al. 1979). Designated as PG1159-035 (hereafter PG) this star is distinguished not only by the complete lack of hydrogen in its spectrum but also by an effective temperature that exceeds 8 × 104 K (McGraw, private communication). The photometric data show that this star is pulsating with two periods - 539 seconds and 460 seconds and the light curve is very reminiscent of that of a ZZ Ceti variable star (DA white dwarfs pulsating in non-radial modes). However, its spectral characteristics show that it cannot be included in this class since analysis of both optical and IUE spectra show that the major atmospheric constituents are probably helium and carbon and that its surface gravity is considerably lower than 108 cm sec−2 characteristic of a DA white dwarf. Its energy distribution suggests a small amount of reddening and since it is far out of the plane it must be at a distance at least 1 kpc. This estimate is supported by a null proper motion over a 13 year baseline (Luyten 1979, private communication to J Liebert). These data suggest that its luminosity exceeds 10 L⊙. In any case, it would need a luminosity as large as 10 L⊙ to fall on or above the white dwarf cooling curve at Te = 8 × 104 K (Lamb and Van Horn 1975). All of these facts suggest strongly that this star is unique and a new kind of pulsating variable.
Rotational Modes in A Uniformly Rotating Star
Authors: Smeyers P.
Published: July 2016

The linear adiabatic oscillations of a uniformly rotating star are examined with respect to a co-rotating frame of reference. It is shown that time-independent displacement fields are allowed and can be represented as toroidal fields. The time-dependent oscillation modes are governed by a system of differential equations of the fourth order in time for axisymmetri’c perturbations, and of the fifth order for non-axisymmetric perturbations. Therefore, in comparison to a non-rotating spherical star, a rotating star allows a new class of non-axisymmetric oscillation modes with non-zero frequencies. These modes correspond to the r-modes, which originate from purely toroidal displacement fields in a non-rotating spherical star.
Towards effective data processing: portable software models
Authors: Mistrik I.
Published: July 2016

In many application fields a need for more effective data processing has been identified. There are various means to achieve this goal: 1) new technological developments; 2) new information management and organizational techniques; 3)new methods and tools for systems development; 4) greater awareness of economic, legal, and social aspects of data processing. An attempt is being made to integrate these means into the “optimal solution” of effectiveness problem. The approach taken is to develop flexible software models in order to test for applicability in the real-world environment. Major characteristics of such software models are: 1) portability; 2) modifiability; 3) functionality; 4) operationality.
Aids to the retrieval and evaluation of astronomical data
Authors: Wilkins G.A.
Published: July 2016

Authors, editors and data centres should ensure that data on astronomical objects and systems can be readily located and that their accuracy can be properly judged by the user. In particular, authors and editors should endeavour to ensure that the title, abstract and other retrieval aids are accurate and informative and that the procedures used are described in sufficient detail to allow a proper evaluation of the results. Data centres should, where appropriate, provide additional aids to allow the users to find data efficiently and should, in all cases, ensure that each datafile contains adequate information about the sources of the data and about the significance of the fields in the records of the file.
Dictionnaire de la nomenclature des objets celestes
Authors: Fernandez A. , Lortet M.C. , Spite F.
Published: July 2016

The confusing situation of the nomenclature of the astronomical objects led us to build, as a first step, a dictionary of the designations presently used. The future publication of this work is supported by Commission 5 of IAU. A brief description of this dictionary, as well as a sample of it, is given here. The designations (acronyms) will be given, together with the format, the total number of objects, the type of objects, the code for the complete bibliographical reference, the signification of acronym… Nomenclature for X and γ-ray sources, designations by constellations and descriptive designations will be dealt with as well. Good compilations are a considerable help in nomenclature problems; every effort should be made in order of : 1) urging specialists to build compilations 2) announce compilations in progress to Astronomical Data Centers and to the present authors.
Large scale photometric surveys using archival plates
Authors: Janes Kenneth
Published: July 2016

Modern microdensitometers and image processing software suggest the possibility that it may soon be feasible to utilize the enormous amount of photometric and positional data potentially available on existing photographic plates. This paper describes the possibility of large-scale surveys and outlines a method for densitometric calibration of plates from an analysis of the detailed structure of the star images on the plate.
Catalogue bibliographique de vitesses radiales stellaires
Authors: Barbier M. , Petit M.
Published: July 2016

The continuation of the Abt-Biggs catalog of stellar radial velocities from 1970 is presented. A first part (6000 references) has been published on microfiches (CDS, 1980). Five thousand new references should be published in a near future.
The new catalogue of optical HII-Regions
Authors: Polechova P.
Published: July 2016

The principles of the work on the new catalogue of the optical HII-regions are described.

On the basis of thirteen catalogues and lists of the optical HII-regions the catalogue of these objects had been compiled by me (Marsalkova, 1974). The main source of the objects on the northern sky was the catalogue of Sharpless (1959) which up to now is the only one in computer-readable form, the southern sky being characterized by a larger number of smaller catalogues represented in first place by that of Rodgers et al (1960) and that of Gum (1955). For this already published catalogue (now referred to as the “old” one) only optical data were taken into account. The catalogue was supplemented by a list of excluded HII-regions like supernova remnants, planetary nebulae and galaxies.
A Spectrophotometer Devoted to Stellar Seismology
Authors: Fossat Eric , Decanini Yves , Grec Gérard
Published: July 2016

I wish to begin by saying a few words on an instrument which has been utilized thus far only to observe the sun, with a very small telescope of about 5cm diameter. This may appear to stand far away from the main topic of this meeting but in fact, the scientific program which is successfully being developed on the sun would be of major interest for stellar astronomy if it could be extended to at least a few bright stars. I will therefore describe also a possible extrapolation of an instrument to be used on the largest available telescopes for stellar observations.
Two-Dimensional Television System: Application for Direct Acquisition of Images and Speckle Interferometry
Authors: Balega Yu.Yu. , Somov N.N. , Fomenko A.F.
Published: July 2016

A two-dimensional photon counting and analog television system has been developed at the Special Astrophysical Observatory of the Academy of Sciences, USSR, for morphological investigations and
photometry of faint extended objects, spectrophotometry and speckle interferometry.
TV Spectrum Scanner of the 6-Meter Telescope
Authors: Somova T.A. , Somov N.N. , Markelov S.V. , Nebelitskii V.B. , Spiridonova O.I. , Fomenko A.F.
Published: July 2016

The television multichannel spectrophotometer of the BTA (SAO, USSR AS), used for accumulating and recording the spectra of faint astronomical objects, is described. The Soviet image detection system comprises a three-stage image tube (UM-92) optically coupled to a high sensitivity SIT TV tube. The system operates in a photon counting mode with digital definition of the centres of photoelectron events. The spectrophotometer operates on-line with a minicomputer which exercises control of the system and performs primary reductions of the data collected. Illustrations of scans obtained during observations are given.
An efficient integrator that uses Gauss-Radau spacings
Authors: Everhart Edgar
Published: July 2016

This describes our integrator RADAU, which has been used by several groups in the U.S.A., in Italy, and in the U.S.S.R. over the past 10 years in the numerical integration of orbits and other problems involving numerical solution of systems of ordinary differential equations. First- and second-order equations are solved directly, including the general second-order case. A self-starting integrator, RADAU proceeds by sequences within which the substeps are taken at Gauss-Radau spacings. This allows rather high orders of accuracy with relatively few function evaluations. After the first sequence the information from previous sequences is used to improve the accuracy. The integrator itself chooses the next sequence size. When a 64-bit double word is available in double precision, a 15th-order version is often appropriate, and the FORTRAN code for this case is included here. RADAU is at least comparable with the best of other integrators in speed and accuracy, and it is often superior, particularly at high accuracies.
Do comet groups exist?
Authors: Lindblad B.A.
Published: July 2016

The phenomena of comet groups, i.e. sets of comets that exhibit similarity in their orbital elements, is investigated. A computer program based on the D-criterion of orbital similarity is used to search for comet pairs and groups. The reality of the groups is tested by making computer searches in random samples of comet orbits.

The data base for the study is 599 long-period comet orbits. The degree of orbital similarity within a comet group was first assumed to be identical to that encountered in meteor streams. The computer search at this level produced five comet pairs plus two groups with four and seven members, respectively. The latter two represented the eleven known members of the Kreutz group of sun-grazing comets. A comparison with searches in random samples showed that the two Kreutz groups were significant. There is a probability of 0.2 that the five comet pairs found in the real sample could be accidental formations.

In a second study the orbital similarity parameter Ds was varied and the number of comet groups found in the real and synthetic comet populations was compared at each level of Ds. Apart from the Kreutz group of comets, the number of groups detected in the real comet sample was for all levels of orbital similarity only slightly higher than the average found in the random samples. At the 2σ confidence level we conclude that comet groups exhibit similarity in their orbital elements, that is no greater than might be expected by chance.
Influence op non-gravitational forces on the orbital evolution of the short-period comets
Authors: Belyaev N.A. , Ivanovskaya K.P.
Published: July 2016

This paper is concerned with the influence of non-gravitational forces on the orbital evolution of the short-period comets. This influence is variable for different comets and is especially noticeable for those comets which undergo approaches with Jupiter. When studying the dynamic evolution it is desirable to take into account the non-gravitational effects.
On the nongravitational effects in the comet Encke motion
Authors: Batrakov Yu.V. , Chernetenko Yu.A.
Published: July 2016

A factor depending on geomagnetic index was introduced in the B. Marsden’s formula for the nongravita-tional force. The orbit of the cornet Encke covering seven apparitions (1895-1914) obtained with this modified formula shows better residuals than that obtained with the non-modified one.
The F-Corona and the Circum-Solar Dust Evidences and Properties [G. Nikolsky Memorial Lecture]
Authors: Koutchmy S. , Lamy P.L.
Published: July 2016

This review deals with the main properties of the F-corona. Analysis of its morphology and photometry allows to derive a new axisymmetric, non-spherical model. Polarization, color and infra-red properties are further considered. We suggest the existence of a variable “local” component surperimposed on a quasi-stationnary “far” component.
Doppler Shifts Measurements of the Zodiacal Light at the Pic Midi Observatory
Authors: Robley R. , Bücher A. , Koutchmy S. , Lamy Ph.
Published: July 2016

At the Pic-du-Midi Observatory, we have started a program to observe the spectrum of the zodiacal light in the region of the b absorption lines of MgI. We use a 1 meter spectrograph with a holographic grating followed by a focal reducer to obtain a 19 Å/mm dispersion over the micro-channel plate camera. Calibrated spectra obtained with an exposure time of 10 minutes systematically show earth atmospheric emission lines attributed to both NI and OH. The temporal variability of these emissions prevents an accurate determination of the line profiles. Our best processed measurements of Doppler shifts obtained during five nights do not allow to descriminate between circular and hyperbolic orbits of the interplanetary dust.
Explorer 46 Meteoroid Bumper Experiment: Earth Orbital Debris Interpretation
Authors: Kessler D.J.
Published: July 2016

The Meteoroid Bumper Experiment on Explorer 46 (launched 1972) was placed in Earth orbit to evaluate the effectiveness of using double-wall structures against meteoroids. This paper re-examines the data from this experiment. Certain sets of sensors were found to be penetrated much more frequently than other sets. The most plausible explanation is that nearly all of the penetrations were from an Earth orbiting population of particulates. In addition, because a large percentage of the penetrations occured soon after solid rocket motors were fired in space, the particulates are most likely 75 μm diameter aluminum oxide. Aluminum oxide particulates are a major exhaust product from solid rocket motors. The size of particulates from most current solid rocket motors is found to range between 0.1 μm to 20 μm. Modeling the orbits of particulates from these rockets predicts that measurements in Earth orbit of interplanetary dust in this size range are also likely to include Earth orbiting particulates from solid rocket motors.
Prospects for Cosmic Dust Experiments on the Planned Reflight of LDEF
Authors: Walker R.M. , Zinner E.
Published: July 2016

The Long Duration Exposure Facility (LDEF-I), which contains a number of cosmic dust experiments, is due to be launched in the spring of 1984 and recovered about a year later. Current plans call for re-fitting the LDEF spacecraft with a large area of plastic nuclear track detectors and relaunching (LDEF-II) for a flight that will last about 2 years. The main purpose of the mission is to extend primary cosmic ray abundance measurements to the actinide region. A meeting was held at Washington University in December 1983 to discuss the problems and prospects for cosmic dust experiments on LDEF-II. Most participants were drawn from the LDEF-I community of investigators. The meeting resulted in a report which treated the scientific rationale for LDEF-II dust experiments, discussed various implementation options, and concluded with a set of summary recommendations. We discussed this report and summarized the status of LDEF-II as of this meeting. It is important to note that the report serves equally well as a basis for discussion of dust experiments on future space stations.
Acoustic Penetration and Impact Detector for Micrometeoroid and Space Debris Application
Authors: Kuczera H. , Iglseder H. , Weishaupt U. , Igenbergs E.
Published: July 2016

An active detector is described which recently has been developed for laboratory impact measurements and which already has been proposed for cosmic dust flight experiments. The detector consists of a very thin penetration foil and an impact plate. By means of piezo detectors the elastic-wave propagation times between the impact location and the piezo detectors can be measured in the foil and in the target. The evaluation of these signals gives the time of the event, the impact location, the projectile velocity, the flight path direction and at least the order of magnitude of mass of the impacting particle. This type of sensor will meet all requirements for particle detection in the diameter range from a few microns (dust particles) up to approx. a few millimeters (space debris) at all velocities. Small-sized projectiles can be detected by sensitive amplifiers. Low-energy electronics including data storage can be used for triangulation and impact time calculation. First experimental results which have been achieved in the Munich Accelerator Facilities will be presented.
Complementary Laboratory Measurements of Individual Interplanetary Dust Particles
Authors: Fahey A. , McKeegan K.D. , Sandford S.A. , Walker R.M. , Wopenka B. , Zinner E.
Published: July 2016

Complementary analysis techniques including electron microscopy (SEM/EDX and TEM), molecular spectroscopy (FTIR and Raman), and secondary ion mass spectrometry (SIMS), are used to study individual dust particles collected in the stratosphere. Large deuterium enrichments and solar flare tracks show that most particles in the “chondritic” class are interplanetary dust particles (IDPs). Infrared transmission spectra of most IDPs fall into three major classes (layer-lattice silicates, pyroxenes and olivines). TEM and Raman measurements confirm this classification. The IR spectra show certain similarities to spectra observed in comets and protostars. In particular the 6.8 μm features observed in protostars and IDPs may have a common origin. Large D excesses are observed in IDPs of the first two IR classes. The correlation of D/H ratios with the C concentration indicates a carbonaceous carrier of the excess D. The D enrichments and IR spectra provide links to interstellar molecular cloud material.
Physical Properties of Submicronic Carbonaceous Particles Candidate as Cosmic Dust
Authors: Borghesi A. , Bussoletti E. , Colangeli L.
Published: July 2016

We present here a compendium of our laboratory measurements of the physical properties of submicronic particles made by some carbonaceous materials candidate as cosmic dust: amorphous carbon, silicon carbide. Comparison with data obtained by other authors is presented and discussed in view of astrophysical applications.
Microwave and Laser Facilities to Determine Scattering and Colour Signatures Related to the Physical Properties of Dust Particles
Authors: Weiss-Wrana K. , Giese R.H. , Zerull R.H.
Published: July 2016

At Bochum there exist three experimental setups for measurements of the scattering properties of dust particles. The microwave analog experiment is the best choice for systematic studies of particles in the size range between 0.5 and 10 times the wavelength (correspondig to about 0.25 to 5 μm in the optical region). The multicolour laser experiment providing electrodynamic suspension of single dust particles is optimized for studies of particles in the size range between 20 and 150 μm. Another laser experiment is designed for rapid analysis of particle mixtures in view of in-situ applications. The measuring principles of all instruments are shortly summarized.
Preliminary Results of a Dust Scattering Experiment
Authors: Bliek P. , Lamy P.L. , Courtes G.
Published: July 2016

An experimental device, of the nephelometer type, to study the scattering properties of dust particles is presented. A fluidized bed generator produces a continuously flowing aerosol which is illuminated by either a He-Ne laser or a Xenon are lamp with interference filters. The size of the dust particles ranges between 1 and 30 μm. The scattering properties of dust particles are measured in the two directions of polarization. The first results are presented.
Zodiacal Light and the Spatial Density of Interplanetary Grains
Authors: Lamy P.L. , Perrin J.M.
Published: July 2016

Using our model of light scattering by large rough grains, the compatibility of the observed properties of the zodiacal light with models of the spatial density of interplanetary grains is investigated. The agreement is not yet satisfactory and probably calls for further revision of the density distribution function. Our previous conclusion that submicronic grains gives a non-negligible contribution (Lamy and Perrin, 1980) is confirmed.
Wavelength Dependence of the Zodiacal Light
Authors: Schiffer R. , Thielheim K.O.
Published: July 2016

We calculated the scattering cross section of an ensemble of large, convex, randomly oriented particles with a slight surface roughness. If the roughness structure is described by an exponential correlation function, the degree and angular dependence of the zodiacal light reddening are well reproduced by our model.
Equilibrium Temperatures of H2O, Co2 and NH3 Ice Grains in the Solar System
Authors: Crifo J.F.
Published: July 2016

The equilibrium temperatures of spherical grains of pure H2O, CO2 and NH3 ice in the solar system are computed at heliocentric distances ranging from 1 AU out to (> 1500 AU) where solar illumination becomes negligible compared to galactic and extra-galactic light; the grain size range is from submicron to tens of meter in diameter. These results are based on recently published optical constants and on the use of the “complex angular momentum” (CAM) theory for computing the interaction of the grains with light.
The Gravitational Zones of Influence of the Planets Acting on Small Celestial Bodies
Authors: Misconi N.Y. , Rusk E.T.
Published: July 2016

Tisserand’s definition of the “sphere of action” of a planet is based on the equality of tidal vs. gravitational acceleration ratios of the sun and planet. Öpik and others based their relation on equating the differential solar and planetary forces on a particle. Neither expression was formulated to describe the zone of influence surrounding a planet when considering the small, but significant, long-term perturbative effects of the planets on a particle’s orbital elements. For the purpose of determining these effects on interplanetary dust we derive a zone of influence based on equating the gravitational forces of the sun and planet.
An Analysis of IRAS’ Solar System Dust Bands
Authors: Dermott S.F. , Nicholson P.D. , Burns J.A. , Houck J.R.
Published: July 2016

Measurements of longitudinal variations in the brightness and in the latitude of the solar system dust bands recently discovered by IRAS will determine the orbital elements of the particles involved and may discriminate between cometary and asteroidal models of the origin of these bands. The expected variations for bands of dust particles with common orbital elements and small eccentricity and inclination are calculated as functions of semimajor axis.
Soft X-Ray Spectroscopy from the X-Ray Polychromator on the Newly Repaired Solar Maximum Mission
Authors: Strong K.T. , Stern R.A. , Lemen J.R. , Phillips K.J.H.
Published: July 2016

The X-Ray Polychromator (XRP) resumed operations on 24 April 1984 following the successful in-orbit repair of the Solar Maximum Mission Satellite. Since that time the two instruments that comprise the XRP, the Flat Crystal Spectrometer (FCS) and the Bent Crystal Spectrometer (BCS), have been used to obtain new spectroscopic data from active regions and flares. The FCS, in particular, has accumulated far more observations of soft X-ray line profiles than were obtained during SMM-I in 1980. For this short presentation, we have chosen two topics to illustrate the type of data that we have obtained since the repair.
Measurement of the Increase in Altitute of the Soft X-Ray Emission Regions of Solar Flares
Authors: Seely J.F. , Feldman U.
Published: July 2016

The upward motion of the hot thermal regions of several large (M type) solar flares have been determined from the soft X-ray spectral data recorded by the scanning spectrometer (SOLFLEX) on the P78-1 spacecraft. The change in position of the emission is measured with a spatial resolution of 2000 km and a temporal resolution of 58 sec. For the limb flares that are studied, the centroid of the Ca XIX emission region moves to a higher altitude with a speed of 20 to 40 km/sec for a period of 20 to 30 minutes following onset of the flare and reaches an altitude of 30,000 to 40,000 km. The speed of ascent decreases with time, and in several flares that are studied, there is an indication that the centroids of the Ca XIX emission oscillate in altitude with amplitudes of 5,000 to 10,000 km and with periods of 5 to 8 minutes.
Comparative Study of Electron Bremsstrahlung in Various High ρ - T Potentials
Authors: Lamoureux M. , Cauble R. , Kim L. , Perrot F. , Pratt R.H.
Published: July 2016

In order to calculate bremsstrahlung cross sections in plasmas, an atomic potential which includes the effects of the surrounding plasma is required. For the high ρ - T conditions we are considering (ne = 1025 cm−3, T = 500 ev), plasma correlative effects are important. In these strongly coupled plasmas, the Debye-Huckel potential is irrelevant and not considered here. The statistical Thomas-Fermi (TF) potential (Feynmann, Metropolis, and Teller, 1949) is known to be correct at very high densities but does not contain correlation information. A semiclassical treatment of correlations that accurately reproduces results of numerical simulations of strongly coupled plasmas is the hypernetted chain (HNC) approximation to the hierarchy of equations describing density distributions (Hansen and McDonald, 1981). The method generates many-body distributions using an analytic two-body interaction that successfully approximates quantum effects at short distances. These distributions are used in the Poisson equation to find the effective potential (Cauble, Blaha, and Davis, 1984). An alternative method (Gupta and Rajagopal, 1982) of including correlations is to treat them in a quantum mechanical manner, taking into account ion correlations as well as electron exchange and correlation; this is done in density functional theory (DFT), where electron wavefunctions and the effective potential which is used here are obtained self-consistently (Dharma-wardana and Perrot, 1982; Perrot and Dharma-wardana, 1984). Comparison of these methods can be found elsewhere (Cauble, Gupta, and Davis, 1984). These potentials for aluminum at 1025 cm−3 and 500 eV are displayed in Fig. 1.
Physical Constraints on Models of Gamma-Ray Bursters
Authors: Epstein Richard I.
Published: July 2016

The power per logarithmic bandwidth in gamma-ray burst spectra generally increases rapidly with energy through the x-ray range and does not cut off sharply above a few MeV. This spectral form indicates that a very small fraction of the energy from a gamma-ray burst source is emitted at low energies or is reprocessed into x-rays and that the high-energy gamma rays are not destroyed by photon-photon interactions. The implications are that the emission mechanism for the gamma-ray bursts is not synchrotron radiation from electrons that lose most of their energy before being re-accelerated and that either the regions from which the gamma rays are emitted are large compared to the size of a neutron star or the emission is collimated and beamed away from the stellar surface.
Computer Simulations of Astronomical Phenomena
Authors: Noels A. , Papy R.
Published: July 2016

The basic idea of this project is to introduce a senior student to an astronomical phenomenon that he analyses carefully and simulates on the graphic screen of a personal computer. In a second step, this simulation serves as a demonstration for junior students.

Three examples are presented here: the retrograde motion of the planets, the Earth’s rotation, and the precession and the equilibrium figure of the Earth due to tides. Programs have been written on an IBM PC/AT.

It would be highly desirable to start an exchange program of material of didatic interest among the international astronomical community
A Series of Astronomy Programs for Television in India
Authors: Narlikar Jayant V.
Published: July 2016

Astronomy, unlike most other sciences, arouses great curiosity amongst laypeople. It is a subject that can be described relatively easily in public lectures. Distinguished astronomers like James Jeans and Arthur Eddington in the past and many more in recent times have “stooped down” to the public level to share the excitement of astronomical discoveries. Today, the popularization program normally proceeds in four different ways — through popular articles, public lectures, planetarium shows, and radio – TV programs. However, this overwhelming public interest in astronomy brings its own difficulties. Not all of it is motivated by a scientific interest! Many persons read mystic significance into astronomical findings. Many more are guided by astrological interest. Many fail to perceive the scientific basis for astronomy, a subject whose laboratory is the whole cosmos with objects too remote to be subject to scientific experimentation.
Process and Practice
Authors: Bishop Jeanne E.
Published: July 2016

I would like to discuss strategies for participation within planetarium programs. The planetarium is not only a theater in which passive audiences can hear lectures and see demonstrations. It is also a classroom in which people of all ages can benefit from involvement. Participatory programs have been advocated in the US since the early 1970’s, and the idea has grown and spread.

One participatory method involves drawing. For example, an elementary school group can draw a planet group for two or three different times. The psychological value of learning by drawing is well known. And drawing positions of stars and planets with appropriate labels produces take-home sky charts. Families can and do use them to learn astronomy and enjoy the sky together.
Teaching Teachers in the Planetarium
Authors: Szostak Roland
Published: July 2016

Many people do not know what a planetarium is. Since this disappointing fact is even true for well-educated people, including students and teachers, many pupils will never hear about planetariums. In order to spread knowledge about planetariums, universities can play a major role. One of the best ways is to visit a planetarium with students, especially those who will become teachers. Such a visit is a very efficient multiplying factor.

But in order to make a planetarium visit efficient, one should not go unprepared. We therefore go with education students who are enrolled in an astronomy course. Before their visit, we inform them about what a planetarium is and about how it is used. We teach them, for example, specific terms of the rotating sky, its coordinates, and the significance of the ecliptic and of retrograde loops. And of course, we teach the students how the sky appears from different latitudes, including the equator and the southern hemisphere. We also teach the technical aspects of how the projector works.
Astronomy for the Visually Handicapped
Authors: Lacombe Pierre
Published: July 2016

It is important to add that in addition to the general public and all the students and teachers involved in school systems, the planetarium community in general tries also to reach some special groups of the public. The groups could be those with hearing problems, those who have never seen any stars (the visually handicapped), amateur astronomy groups, and even gifted students.

As you can imagine, these special groups represent a very small fraction of our attendance at the planetarium but they need special treatment, and for that reason many planeteria around the world have at one time or another prepared a unique program in the star theater for them, built new and special exhibits, or given technical tours of their installations.
A Planetarium Oriented Sequence of Exercises
Authors: Chambliss Carlson R.
Published: July 2016

The introductory course in astronomy intended for non-majors is taken by about 150 students per semester at Kutztown University. This institution is fortunate in having a planetarium, which is used extensively both in course work in astronomy and with visiting school groups. The projector is a Spitz model A3P, the dome is of perforated aluminum and has a diameter of 10.5 meters, and the seating capacity of the planetarium is about 120. The introductory astronomy course at Kutztown consists of two hours of lectures and a two-hour laboratory session per week. There are five or six laboratory sections, each of which contains about 25-30 students.
Teaching and Popularizing Astronomy in Egypt and other Arab Countries
Authors: Aiad A.
Published: July 2016

The recent astronomy of the Arab countries began by the last decade of the 19th century in Alger and the first decade of the 20th century in Helwan. Two Arab countries have been members of the IAU, namely Egypt (since 1925) and Iraq (since 1976). Saudi Arabia, Algeria, and Morocco became members in 1988. We restrict ourselves here to the teaching and popularizing of astronomy.

In Egypt there is a single department of astronomy; since 1937 it has belonged to the Faculty of Science of Cairo University. A B.Sc. in astronomy requires two years’ study of mathematics and physics followed by two more years devoted mainly to astronomy, including a small project. Elementary courses for other sciences, such as geography and geophysics, are also taught at Cairo University and the American University in Cairo.
Theoretical Modelling of Algol Disks
Authors: Hubeny I.
Published: July 2016

A brief review of various theoretical approaches to model accretion disks is presented. Emphasis is given to models that determine self-consistently the structure of a disk together with the radiation field. It is argued that a proper treatment of the vertical structure is essential for calculating theoretical spectra to be compared with observations. In particular, it is shown that hot layers above an accretion disk (sometimes called disk “chromospheres” or “coronae”), whose presence is indicated by recent UV observations of strong emission lines of highly ionized species, may be explained using simple energy balance arguments.
Algols: Wherefrom, Whereto, and What in Between ?
Authors: De Greve J. P.
Published: July 2016

Four different aspects related to the evolution of Algols are discussed: the occurrence of a contact phase during the mass transfer, the evolution of short period systems evolving through case A mass transfer, the influence of the mass transfer on the surface abundances of both components, and the problem of the initial parameters of Algol systems. For the latter, a search is made for conservative case B systems. UZ Cyg seems to be a good candidate for such evolution. Finally, some remarks are given on the initial values of the low mass Algol S Cancri.