bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy Levels and Classification Problems in Spectra of Highly Ionized Elements of the Fifth Period
Authors: Zohar M. Even , Fraenkel Benjamin S.
Published: July 2016

New Spectra of highly ionized atoms of the fifth period are to be published soon. Selected energy levels obtained with 104 A peak current vacuum sparks are presented in Table I.
X-Ray Spectra from Highly Ionized Iron and Nickel
Authors: Schwob J. L. , Fraenkel B. S.
Published: July 2016

X-ray radiation is obtained from a point plasma produced by pinch effect Cohen et al. (1968) in a vacuum spark similar to that used by Lie and Elton (1971) with a 220 kA peak current. The extremely dense and hot minute plasma appears at a distance of 0.5 to 1 mm from the anode tip and has maximum dimensions of a few microns.

The spectroscopic observations are performed by means of a focusing Cauchois spectrometer so as to avoid effects of fluctuations in the source position.
Identifications of Emission Lines in the EUV Solar Spectrum
Authors: Jordan Carole
Published: July 2016

In this brief review of solar line identifications the progress made since the previous conference in this series, which was held in Maryland in 1968, will be discussed.

Only lines which appear in emission when seen in the solar disk will be included, thus excluding lines from low stages of ionization at wavelengths of above about 2000Å which can appear in emission at the limb.

It is convenient to divide the solar spectrum between about 1.5 Å and 2300 Å into wavelength regions, since the various types of transitions which will be discussed tend to appear over restricted wavelength ranges.
Spectrograms of α Lyra and β Cen in the Region of 2000–3800 Å
Authors: Gurzadyan G. A. , Ohanesyan J. B.
Published: July 2016

During the flight of the spaceship ‘Salyut’, manned by the spacemen G. T. Dobrovolsky, V. N. Volkov, and V. I. Patsaev, nine spectrograms of α Lyra and six spectrograms of β Cen were obtained with the help of the ‘Orion’ system, in the range of wavelengths 2000–3800 Å and with a spectral resolution of about 5 Å near 2600 Å.

The ‘Orion’ system is a telescope of the Mersenn system, with a large mirror of 280 mm diameter, and a slitless spectrograph of the Wadsworth system with a diffraction grating (Figure 1). The dispersion is 32 Å mm-1. The spectrograms were recorded on a perforated photographic film, 16 mm wide, covered with emulsion of the UFSH-4 type.
Experiment to Determine the Temperature Structure in the Solar Chromosphere and Corona
Authors: Negus C. R.
Published: July 2016

An experiment is in course of preparation at the Astrophysics Research Unit at Culham for flight on a Sun-pointing rocket. It is designed to determine the ionization temperature and electron density as a function of height in the temperature range of about 8 × 104 K to 3 × 106 K by measuring limb to disk intensity ratios of extreme ultraviolet emission lines in the 170 to 850 Å region. The work is an extension of current experiments in which normal-incidence spectrographs are used to determine the structure lower in the chromosphere-corona transition region.
Solar X-Ray Source Unassociated with Sunspots
Authors: Gurzadyan G. A. , Vartanian K. V.
Published: July 2016

On October 3, 1970 the astrophysical rocket observatory K-2 was launched from the Soviet Union, designed to investigate the Sun in the region of short- and X-ray waves Gurzadyan et al. (1971). During the launching a series of X-ray pictures of the Sun was received, in the period 04 h 22 min to 04 h 30 min universal time, through an aluminum foil 5000 Å thick, covering a polistriol film 1000 Å thick. The pictures were taken by means of a pinhole camera under the following conditions: the focal length was 150 mm, the angular resolution – from 8’ to 0.’92, which corresponds to the dimensions of the input diaphragm from 0.28 mm to 0.04 mm, effective exposure – 520s, the pointing accuracy by a stabilised platform carrying the instruments – 0.′7-0.′8. The picture was taken by a film of the UF-R type (Kalinkina et al, 1965).
Mapping the Solar Corona in X-Ray Lines of OVII and NeIX
Authors: Catura R. C. , Acton L. W. , Meyerott A. J. , Culhane J. L.
Published: July 2016

Some preliminary results of a rocket experiment, which utilized collimated Bragg Crystal spectrometers to map solar X-ray line emissions from He-like ions of oxygen and neon are presented. The two spectrometers used KAP crystals with a common field of view 1.7’ FWHM in the narrow dimension. The spectrometers were scanned in wavelength once each second to observe the resonance, intersystem and forbidden lines of OVII and NeIX.
The Classification of Fe XVIII to XXIV Emission Lines in Solar Flare Spectra
Authors: Fawcett B. C.
Published: July 2016

This paper reports recent progress in the classification of the spectra of iron XVIII to XXIV. Emission lines due to these stages of ionisation were reported in the spectra of solar flares by Neupert et al. (1967) who pointed out that the 2s2 2pn–2s2 2pn-1 3d configurations were mainly responsible. The present work verifies this and in addition gives individual line classifications of some of the strongest lines. Earlier studies of these transitions were reported by Fawcett (1965), Fawcett et al. (1967), and Feldman and Cohen (1968, 1970). Spectra of Fe XVIII to XXIV dueto 2s2 2pn–2s 2pn+1 transitions lie near 90 Å. Satisfactory solar and laboratory observations of these spectra are not yet available. The new classifications in these isoelectronic sequences are extended almost as far as iron and enable accurate extrapolations to iron. Isoelectronic spectra of both the forementioned transitions have been studied and the wavelengths tabulated (Fawcett, 1970, 1971a, b; Fawcett et al., 1971) for all the elements in the period between silicon and iron. The wavelength data enables the calculation of the 2s2 2pn energy levels and hence provides confirmation of the identity of solar forbidden lines in silicon, sulphur, argon and calcium. These energy levels are in close agreement with the theoretical calculations of Edlén reported at this Conference.
Polarimetry of Symbiotic Stars
Authors: Piirola V.
Published: July 2016

Five symbiotic stars have been observed for linear polarization (UBVRI) in September 1981. Three systems, CH Cyg, CI Cyg and AG Peg show intrinsic polarization while in the case of Z And and AX Per the observed polarization seems to be mostly of interstellar origin. The position angle of polarization of CI Cyg and AG Peg rotates strongly vs. wavelength, as observed also for CH Cyg in 1977-80. The polarization of CH Cyg has decreased since May 1980, especially in the I, R and U bands, so that the maximum polarization is now in the blue (PB ~ 0.3 %). Probably we are monitoring the formation, growth and disappearance of dust particles in the atmosphere of this star. Two related systems, PU Vul (Nova Vul 1979) and R Aql (Mira) have polarization behaviour rather similar to that of symbiotic stars which suggests that the M type giant present in these systems is responsible for most of the intrinsic polarization.
The Evolutionary Status of the Secondaries of Cataclysmic Binaries
Authors: Ritter H.
Published: July 2016

It is shown that the secondary components of cataclysmic binaries with orbital periods of less than ~10 hours are indistinguishable from ordinary low-mass main-sequence stars and that, therefore, they are essentially unevolved. On the other hand, it is shown that, depending on the mass ratio of the progenitor system, the secondary of a cataclysmic binary could be significantly evolved. The fact that nevertheless most of the observed secondaries are essentially unevolved can be accounted for by assuming that the probability distribution for the initial mass ratio is not strongly peaked towards unity mass ratio.
Star-Planet Systems and Their Relation to Low Mass Cataclysmic Variables
Authors: Livio Mario
Published: July 2016

We investigate the possibility of forming a low mass cataclysmic binary from a star-planet system. Using certain simplifying assumptions it is shown that an analytic solution for the evolution of the separation can be obtained. The fate of the system is determined by the competition between mass loss and accretion drag. While it is found that some fine tuning is required for the formation of a close binary, such a binary can still be formed, for parameters that are not too exotic.
Mass Loss Associated with X-Ray Bursts of Neutron Stars
Authors: Sugimoto D. , Ebisuzaki T. , Hanawa T. , Kato M.
Published: July 2016

Basic features of observed Type I X-ray bursts are thought to be interpreted in terms of helium shell-flash near the surface of the accreted neutron stars (Lewin and Joss 1981). Numerical models of the helium shell-flash show that the luminosity grows very close to the Eddingotn luminosity just after the peak of energy generation.
Pre-Concluding Remarks
Authors: Bath G.T.
Published: July 2016

In the same spirit as the local organising committee’s “post-final announcement” I should like, as chairman of this session, to extend an invitation to myself to present a few pre-concluding remarks before asking Brian to summarise his view of the highlights of the past few days. My comments will be eclectic, coloured by a theorist’s wish to impose pattern on chaos; order on the anarchy of observations.
Radial Velocities of Extreme Helium Stars and of Hot sdO Stars
Authors: Drilling John S. , Heber U.
Published: July 2016

Radial velocities have been determined for nearly all the extreme helium stars and for the very hot sdO stars discovered by Drilling from high-resolution spectra obtained at ESO and at CTIO.
A Preliminary Analysis of the Pulsating Extreme Helium Star V652 Her (BD+13°3224)
Authors: Jeffery C.S. , Heber U. , Hill P.W.
Published: July 2016

A preliminary fine analysis of the atmosphere of the pulsating extreme star V652 Her (=BD+13°3224) is reported. The mean effective temperature and temperature variation have been determined from the ionisation equilibria of Si and N. Both of these elements are strongly overabundant, whilst C appears to be underabundant.
Ry Sgr: Can the time of the Next Deep minimum Be Predicted?
Authors: Menzies J W
Published: July 2016

The L magnitude of the RCB star, RY Sgr, varies with an amplitud of up to 2.0 mag on a time scale of about 1500 days. The last two deep optical minima have occurred approximately one year after a maximum in L. This behaviour may be characteristic of the star and may allow the time of onset of the next deep minimum to be predicted, in which case it will occur in the second half of 1986.
Hydrogen Deficiency in Algol Secondaries
Authors: Nagar Praveen , Abhyankar K.D.
Published: July 2016

A study was carried out for 309 Algol systems to show that most of the secondary components of low mass-ratio systems are hydrogen deficient stars. This hydrogen deficiency is evident from their positions on a Δ log L - Δ log T plot, where Δ is the difference between the observed quantity, log L or log Te, and the value of the same quantity for a star of the same mass on the empirical Main Sequence. The secondary components are shown to occupy the region of mass losing helium dwarfs on this plot. A correlation has also been obtained between the excess of effective temperature and the mass ratio of the system.
Line Band Profiles in the Spectra of Cool Magnetic Helium-Rich White Dwarfs
Authors: Bues I.
Published: July 2016

For white dwarfs with effective temperatures smaller than 12000 K, the percentage of objects with a helium-rich atmosphere increases compared to the hydrogen-rich sequence. The carbon abundance, which can be determined from line and band strengths (Bues, 1973; Koester et al., 1982), varies by more than a factor of 1000 within this class. Moreover, for the subclass of white dwarfs with strong magnetic fields, the abundance ratio of H/He differs from that of the DB and DA sequences. The hot star Feige 7, analyzed by Liebert et al. (1977), shows lines of hydrogen and helium at a comparable strength for a moderately strong field of 103 Tesla. If there is any chance of finding white dwarfs which are descendants of hot, non-degenerate helium stars with rotation and magnetic fields, then it should be within these objects of mixed composition.
Theory of Dust Formation in R Coronae Borealis Stars
Authors: Fadeyev Yu. A.
Published: July 2016

Application of the homogeneous nucleation theory to the problem of R CrB stars shows that the radial distance of the inner boundary of the carbon supersaturation region is at about 12 photospheric radii for a stellar effective temperature Te = 6000 K. Formation of an optically thick dust shell becomes possible at mass loss rates Ṁ ≳ 10−6 M⊙/yr. However, the upper limit of this mass loss rate cannot considerably exceed 10−5 M⊙/yr since, at higher Ṁ, the theoretically predicted rate of the visual brightness decline is larger than that derived from observations. Comparison of the theoretically predicted radii of dust grains with those observed in R CrB and RY Sgr shows that the mass loss rate in these stars should be in the range of 1 × 10−7 M⊙/yr to 3 × 10−6 M⊙/yr.
On the Origin of Helium Rich Stars
Authors: Tutukov A.
Published: July 2016

The modem theory of stellar evolution leads to several possible scenaria for the formation of many types of hydrogen deficient (usually helium rich) stars. Some of these scenaria are briefly discussed in this paper to provide possible explanations for origins of R Cr B, hot helium and Wolf-Rayet stars; hot sub dwarfs, non-DA degenerate dwarfs and helium stars in binaries like KS Per. The merger of two degenerate stars in close binaries due to the radiation of gravitational waves can lead to several types of helium and carbon rich stars as well as to supernova explosions.
On the Perturbation Technique for the Influence of Magnetic Field on Stellar Oscillations
Authors: Vorontsov S.V.
Published: July 2016

The modification of the Rayleigh’s principle is developed for the determination of the perturbations of the eigenfrequencies due to a weak magnetic field. The perturbational procedure is outlined, including its generalization for a slowly rotating magnetic star.
Model Atmospheres and Radiative Transfer in Chemically Peculiar Stars: Interpretational Significance of Non-LTE
Authors: Hubený I.
Published: July 2016

One of the main problems in studying chemically peculiar (CP) stars is the question of the extent to which the conceptual framework of the contemporary spectroscopic diagnostics is reliable. As the first step, it should be clarified whether the traditional assumption of local thermodynamic equilibrium (LTE) provides an adequate approximation to reality, or whether a more general non-LTE approach should be employed.

The period of rapid development of computational methods and extensive calculations of NLTE model atmospheres is now past its culmination point. The importance of a relevant NLTE description is viewed as unquestionable for hot stars (B and earlier). Consequently, the hot stars attract the attention of most “NLTE theoreticians,” while considerably less attention is being devoted to later types (late B and A). Moreover, the abundance anomalies found in the CP stars are no longer expected to be a spurious result of an inadequate (LTE) analysis (Cowley 1981). It is not commonly accepted that other phenomena such as diffusion, magnetic field, inhomogeneous abundance distribution, etc., are quite essential ingredients of the general atmospheric pattern of CP stars. Therefore, a large part of the astronomers investigating the CP stars now consider the NLTE effects to be rather minor perturbations of the LTE predictions.
Influence of the Magnetic Field on the Polarization of Radiation Scattered by Electrons in Stellar Atmospheres and Envelopes
Authors: Dolginov A.Z. , Gnedin Yu.N. , Silant’ev N.A.
Published: July 2016

The radiation scattering by electrons play an important role for stars with the surface temperature ≥ 2.104 °K. Many among these stars have magnetic fields of the order 1 - 100 G. We shall consider the role of the field for the radiative transfer in continuum spectra.

Electrons in the field form an axisymmetric medium similar to the single axis crystal. Hence, the medium will have dichroism and birefringency. If the gyrofrequency ωB is much less than the radiation frequency ω then the dichroism can be neglected. The circular birefringency can be characterized by the angle of the Faraday rotation
Missing Levels and Lines of Astrophysical Importance
Authors: Johansson Sveneric , Cowley Charles R.
Published: July 2016

The purpose of this paper is to make a brief survey of the knowledge of iron group elements as concerns energy levels and transition arrays in neutral and singly ionized atoms and to give rough predictions of missing levels and lines. The amount of data that have been published for these elements after the edition of the Multiplet Tables are considerable. For detailed information about sources of new data and compilations the reader is referred to the Report from Commission 14 in the Transactions of IAU. In this paper we will focus on still missing energy levels and associated missing transitions, which have to be considered in the construction of synthetic spectra.

The structure of the iron group elements is complex not only because of the filling of the 3d shell but also because of the competition in binding energy between the 3d- and the 4s electron. For a given number of valence electrons, k, we have to consider three different low configurations in the complex (3d + 4s)k having about the same energy in neutral and singly ionized atoms. In neutral atoms the 3dk−2 4s2 configuration generally occupies the ground state, while the 3dk configuration appears at rather high excitation energy. In the singly ionized atoms all three configurations have about the same energy, giving the most pronounced complexity.
Space Observations of Chemically Peculiar and Related Normal Stars
Authors: Leckrone David S.
Published: July 2016

Progress in the spectroscopic study of CP stars and related sharp-lined normal stars from the IUE is briefly reviewed as a preamble to a discussion of the potential for research with the Hubble Space Telescope. The substantial gains in spectral resolution, signal-to-noise ratio and photometric accuracy that will be realized with the High Resolution Spectrograph on the HST will dramatically increase our ability to disentangle the complex ultraviolet spectra of these stars and to carry out accurate quantitative analyses.
The Nature of Balmer Line Variability in Chemically Peculiar Stars
Authors: Musielok B.
Published: July 2016

Photoelectric measurements of the β-index were made for six Ap-stars (56 Ari, 41 Tau, φ Dra, HD 188041, HD 215441, HD 221568) and one He-rich star (HD 184927). For all these stars the minimum of β occurs at a phase of maximum light at a wavelength longward of the null-wavelength region. Such coincidence can be explained by the blanketing mechanism proposed by Kodaira (1973) for the explanation of the Hγ line variations in HD 221568. According to Kurucz (1979), for stars hotter than 9000K an increase of metal abundance in the atmosphere causes an increase of the visible flux and an simultanous decrease of equivalent widths of Balmer lines. The same changes of the visible flux and equivalent widths of Balmer lines can be obtained using a model atmosphere with a suitable higher temperature. Using the Kurucz (1979) model atmospheres, temperature differences were calculated, which are necessary to obtain the observed decrease of the (β-index and the increase of the flux in a given photometric band.
Hα and OI Photometry of Upper Main Sequence Stars with Anomalous Abundances
Authors: E. Eugenio , V. Mendoza
Published: July 2016

Additional α(16)Λ(9)-photometry of upper main sequence stars with anomalous abundances confirm our previous results, namely, Ap stars are neatly separated from normal main sequence stars. Furthermore, Ap stars are located on three different zones of the α(16)Λ(9)-plane, according to their abundance anomalies to form three photometric groups, (i) Si stars, (ii) Hg,Mn stars, and (iii) Cr,Eu,Sr stars.
Short-Periodic Radial Velocity Variations of the B9P Star ET and
Authors: Gerth E.
Published: July 2016

Spectroscopic observations of the B9p star ET and secured at the Bulgarian National Observatory Roshen in the years 1981–1984, consisting of 97 plates, show clearly a radial velocity period of 0.198 d - with a ratio to the photometrical period of exactly 2:1. This behaviour would hint at a close binary system; but there arise difficulties in explaining it by this way because of the extreme short period, so that pulsation must be taken into account. However, besides of the confident period of 0.198 d, there is evidence for shorter periods in the region of 45 min, which may be attributed only to pulsational processes.
On the Ultraviolet Photometric Variability of the Helium-Weak B Stars (From ANS Data)
Authors: Želwanowa E.I. , Sohöneich W.
Published: July 2016

Photometric observations in the ultraviolet region obtained by the ANS satellite enabled us: to confirm with a slight improvement the rotational period of HD 22470 (UV lightcurves of HD 22470 compared with u and magnetic curves are shown in fig. 1); to confirm the variability with very small amplitudes for HD 74196, a member of the open cluster IC 2391 (Fig. 2)

to compare the amplitude-wavelength relations of some other He-weak stars with known periods (HD 35298, HD 142884, HD 144334, HD 175362, and HD 109026). A preliminary rotational period for the star HD 109026 using the 11 ANS observations was found to be about 1.5 days.
A Spectroscqpic Study of the Bp-Star θ Aur
Authors: Kolev D. , Georgeva E.
Published: July 2016

The atmosphere parameters, spectral variability and the magnetic field geometry of the Bp-star θ Aur are evaluated from 30 coude-spectrograms. We adopt Te = 10 800K and lgg = 3.40 (with lower reliability of lg g ) . The equivalent widths of the metalic lines show a relatively great scattering which troubles the period search. The best fit to our data gives the period P = 3.620d, but the variability is clearly seen only for Sill lines. The uncertainties in the star parameters obtained bring to a great uncertainty in the magnetic dipole geometry: i = 86° + 39° and β = 18° + 80°. We adopt the most plausible star parameters to be: R = 3.8R⊙ M = 3.5R⊙, i = 80°, β = 20°, Bp = 1 KGs.
Absorption Lines of Call and H in the Near IR Region of the Magnetic Star HD 152107
Authors: Kuznetsova T.N.
Published: July 2016

A behaviour of H lines P12 - P13 and CaII triplet of the star HD 152107 is studied in the range λλ 8400 - 8800 Å. An analysis of the obtained data enabled us to suspect the presence of a relationship between the variation of equivalent widths of the lines of the Paschen series of Hydrogen CaII lines and that of the star’s magnetic field.
Diffusion Processes and Chemical Peculiarities in Magnetic Stars
Authors: Alerian G.
Published: July 2016

This review tries to expose some essential aspects of our current understanding of diffusion processes in magnetic CP stars. Many problems remain to be explained due to the fact that the presence of strong magnetic fields increases the number of free parameters in “diffusion models”. More observational constraints are needed before one can attempt modelling every aspects of magnetic CP stars.
The Light and Spectrum Variable CP2 Star HR 6127
Authors: Žižňovský J.
Published: July 2016

Photometric and spectroscopic variability of HR 6127 was found. The value of the magnetic axis inclination was derived from the radial velocity variations of metallic lines. The star was classified as cool CP2 star.
Particle Transport in Non-Magnetic Stars
Authors: Michaud G.
Published: July 2016

The observations of AmFm, λ Booti, HgMn and He rich stars that are explained without any arbitrary parameter by diffusion are briefly reviewed, followed by those observations that are not explained by this simple model. Mass loss is then shown to explain a large fraction of the observations that are not explained in the parameter free model. It seems to play a role in the λ Booti, AmFm, He rich and the hot horizontal branch stars. It is only of about 10−15 to 10−13 Mo/yr. Abundance anomalies then help to determine stellar hydrodynamics. It is finally suggested that recent observations of Li underabundances in F stars of the Hyades represent an extension of the AmFm star phenomenon.
Amateur Astronomy from Its Origins to Camille Flammarion
Authors: Seidengart Jean
Published: July 2016

It is not possible to sketch the history of astronomy by amateurs without first defining what the term “amateur astronomer” truly means. But we must avoid using “the benefit of hind-sight” to interpret the past in terms of a concept, the relevance of which has been perceived only during the course of the last one hundred years. In order to avoid the sophistry arising from such a purely imaginary history that is based on false conceptions, it is useful to examine amateur astronomy’s precise status, since its emergence in the dawn of classical science, by outlining the type of relationship that it has had with “professional” astronomy. In doing so, we can evoke some of the major developments in amateur astronomy, the scientific contributions of which, although often of high quality, have at times reached the very forefront of the discipline of astronomy.
Roberts of Lovedale and Eclipsing Binary Stars
Authors: Williams Thomas R.
Published: July 2016

Alexander William Roberts, a great humanitarian and teacher in South Africa, was also a luminary in the astronomical world. This paper discusses his work on variable stars and touches briefly on his career in other areas. Born and educated in Scotland, Roberts migrated to South Africa in 1883, at age 25, to teach at the Native College at Lovedale. He studied mathematical astronomy as a recreational pursuit, but became an active observer in 1889. After two years of general observing, be began a systematic survey using binoculars and an old one-inch theodolite. He carefully plotted all visible stars in selected areas and ranked them in order of their apparent brightness, doing so repeatedly on six evenings for each of the selected areas. His composite sketch became a reference chart as he searched for changes in these fields. With this technique, Roberts discovered more than 20 variable stars.
The Map of the Heavens at the Chateau de Saint-Jean-de-Chepy
Authors: Barbier Joël
Published: July 2016

In the Dauphiné, near Tullins, there is a fortified manor-house known as the Chateau de Saint-Jean-de-Chépy, built in the 13th century, that has in one of its towers an Italian Renaissance map of the heavens painted on the ceiling. The south tower could have been designed for astronomy, with the octagonal-roofed, second floor with its seven windows being used for observation. The first and ground floors have hemispherical vaults, and painted on the ceiling of the first floor there is a map of the heavens that is unique in France. It is painted on the ceiling, with the southern constellations extending down onto the cylindrical wall. It is similar to Italian Renaissance maps, like those in the Old Sacristy at San Lorenzo in Florence (painted by Brunelleschi in 1429), in the Villa Farnesine at Rome (Peruzzi, 1511), and in the Villa Farnese at Caprarola (artist unknown, 1575).

An owner of Saint-Jean-de-Chépy was Maurice Bressieu (1546–1617), a distinguished mathematician, holding the mathematical chair at the Collège de France between 1575 and 1586. He wrote Metrices Astronomicae, which was “highly regarded by mathematicians” and became Speaker for the Kings of France at the Vatican. Pope Sixtus-Quintus made him steward of the Vatican Library. It therefore seems very likely that the map could have been painted for him.
Amateur Astronomers’ Contribution to the HIPPARCHOS Programme
Authors: Bacchus P.
Published: July 2016

The HIPPARCHOS satellite (High Precision Parallax Collecting Satellite) is designed to determine position, proper motion and parallax for a large number of stars. The precision expected (0.002 arcsec), and the absence of systematic errors with position in the sky arise from the following characteristics of the system:

–

Measurements of angular distances between stars a long way apart (58°), are by comparison with a very stable angular reference. This reference is formed by an optical block consisting of two plane mirrors, rigidly mounted, forming an angle of 29° between them, and sending two separate stellar fields into the same telescope;

–

the absence of flexure (thanks to weightlessness) and of thermal deformation (non-expansion material and thermal control) ensure that the angular reference is very stable;

–

operation outside the atmosphere allows the theoretical resolution to be reached; refraction, dispersion and atmospheric scintillation are avoided; diurnal and seasonal effects that interfere with ground-based measurements are non-existent.
The S.A.F. Double Star Section’s Contribution to the INCA-HIPPARCHOS Programme
Authors: Durand P.
Published: July 2016

The Double Star Section of the Société Astronomique de France has been in existence since 1980. It has set up observing groups covering various areas: close binaries, photographic measurements, re-observation of neglected pairs, and astrolabe measurements. All this has been thanks to our sceintific advisors, professionals specializing in double stars: Muller, Couteau, Soulié, Bacchus, and Dommanget. The Section meets twice a year, and it was at Lille in 1984 that J. Dommanget suggested that we should collaborate in the programme of identifying doubtful doubles for the input catalogue for the future satellite Hipparcos.

The first observations were made after the meeting in November 1984, from Paris and with amateur equipment, thanks to an initial list prepared by Prof. Bacchus. After several months we could tell that our equipment was insufficient, and that photocopies of the Palomar Sky Survey were not accurate enough. We needed more powerful instruments and a different organisation to resolve the ambiguity in identification that can arise by two close stars being confused and given the same coordinates, by the presence of a cluster, or by the existence of a faint star that is not given in the catalogues. In all these cases, identifying the star means being able to give it a designation, allowing it to be found on an atlas, and obtaining better coordinates so that the ambiguity is removed. It is a question of astrometry.
A Spectrograph for the T.60 at Pic du Midi
Authors: Bardin Daniel , Buty Didier
Published: July 2016

For several years now the 60-cm telescope at Pic du Midi has been made available to amateur astronomers. We felt that this telescope, which fulfils its role of gatherering light very well, could be fitted with equipment to analyze light. To this end the members of the Teachers and Astronomers Liaison Committee (which includes one of the authors of this communication) collaborated in producing and perfecting a spectrograph suitable for the T.60.

Of basic construction, this equipment enables spectra to be recorded on photographic cassettes. It should be transported to the summit at the end of 1987, and will then be available for any amateur projects that may want to use it.
Amateur Polarimetric Research
Authors: Böhme Dietmar
Published: July 2016

The construction of both single- and twin-channel polarimeters was described. Refractors are suitable for this form of work, and Cassegrains may be used, but Newtonians are not recommended, because of the polarization it introduces. A summary of objects and their degree of polarization was given. Examples of variation in the amount of polarization and its correlation with visual observations of μ Cephei were given.
Reliability and Accuracy of Astronomical Observations by Amateurs
Authors: Kviz Zdenek
Published: July 2016

Who is an amateur-astronomer? We would certainly find several definitions if we tried to get answers from the audience. I am not trying to force anyone to accept my definition, in fact I do not know if I really have one. Someone who likes to read books about astronomy? Professional scientist, expert in other areas of science, but interested in astronomy? Science fiction writer who writes about space travel? Retired professional astronomer who is no longer paid for his work in astronomy? Constructor of telescopes or astronomical instruments? Well, each of these could be discussed. But we will rely, on this occasion, on common sense and take any one who is interested in astronomy and contributes to its progress either by observation or by construction of astronomical equipment and has not an official education in astronomy. He/she simply likes the idea that he/she is contributing by his/her work to our knowledge of the universe and feels proud of it.
Astrometric Measurements of Rarely-Observed Minor Planets
Authors: Chanal Roger
Published: July 2016

The 1986 Minor Planet Ephemerides call observers’ attention to the need for astrometric observations of 120 objects on the “critical list”. Their magnitudes are generally between 15 and 18 at opposition. The author’s programme of observation with simple means was described. The equipment used was a Newtonian 41-cm, f/4.8 reflector, a standard camera back, and Kodak TP2415 film, hypersensitized in forming gas. Out of 25 observations attempted, 20 photographs were obtained, 8 of which were of sufficient quality for the positions to be measured and to be published in Minor Planet Circulars. On two photographs, the minor planet (1982 KM) was detected, but there were no suitable reference stars within the field. (The lack of reference stars brighter than mag. 10 in certain regions should be noted.) The return of measured positions versus photographs obtained (40%) appears very acceptable.
The Contribution of Amateur Astronomers to Cometary Observation
Authors: Heck André
Published: July 2016

Most professional astronomers do not conduct specific comet-discovery programmes and a new comet is, in general, an intrusion into an observational programme, although one that does, of course, receive all the attention it deserves. Comet discoveries are by-products of professional work. This may also be the case with some amateurs (G.E. Alcock discovered his fifth comet while looking for novae). Most amateur discoveries are the result of active and systematic work. Over the period 1951–70, on average 9 comets per year were discovered by amateurs.

The time spent scanning the sky before discovering a comet is typically hundreds of hours. The times of W. Bradfield between his first comets were 260, 306, 145 and 106 hours. Astronomers at Skalnaté Pleso discovered eight comets in six years, averaging one comet for 206 hours of searching. R.D. Austin and R. Meier spent 151 and 105 hours, respectively, between discoveries. These figures are only indicators, because many other factors (including luck) play a part. Alcock’s two comets in six days is quite exceptional.
Amateur/Professional Cooperation in 2 Solar Studies
Authors: Roudier T. , Muller R. , Hulot J.C. , Vaissière F.
Published: July 2016

The modification of properties of granules around magnetic flux tubes has been studied for the first time from photographs (at λ = 4803Å and 5770Å) taken with the 50-cm refractor at Pic du Midi. Statistically, these granules are more numerous, smaller, and more elongated than other granules. During their first two minutes of life they show very pronounced radial orientation to the magnetic flux tube.

Angular measurements on the same granules have a precision of ± 10°, which is sufficient as theoretical studies show that they rotate by 360° in the course of their life. Initial results appeared to show that only explosive granules had intrinsic rotation, but further examination showed that it is a general trend. It seems that the granules do rotate significantly, but that there is a more important “push-pull” effect, in agreement with A. Title’s theory drawn from SOUP images.
The Contribution of Amateur Astronomers to the Study of Variable Stars
Authors: Proust Dominique , Schweitzer Emile
Published: July 2016

The observation of variable stars is one of the most important and the most fruitful areas of stellar astronomy. The contribution of large numbers of visual observations is a determining factor in drawing up light-curves, the latter being the key to the interpretation of the process of variability within these stars.

It is not easy for a professional astronomer to obtain access to modern telescopes, especially to those of large aperture, and it may even be difficult, given the large number of projects put forward. In any case, these large instruments are often unsuitable for the observation of variable stars. Amateurs, on the other hand, have instruments that have a lower degree of precision, but their greater number and the good organization that exists for the reduction of data obtained, represent trump cards in preparing light-curves.
The French Network for Observing Comets and Small Solar-System Bodies
Authors: Chemin Robert
Published: July 2016

For the apparition of P/Halley the CNRS set up RCP639 (Cooperative Research Programme), one part of which was to coordinate French amateur work. This carried out a training programme, at first by publishing (with help from ESO) an observational manual (eds: J.L. Heudier, J.C. Merlin and M. Festou), and then by a series of courses covering astrometry, photography, visual magnitude estimation, and drawing of jets. These courses were provided by J.L. Heudier, J.C. Merlin and T. Laverge, and were taken by about 100 observers. The author was asked to undertake the organization of the section so that it might become a permanent network of observers of comets and minor bodies.
The Role of the Amateur in Modern Astronomy
Authors: Howse H. Derek , Moore Patrick
Published: July 2016

This contribution dealt with the need for international coordination between amateur astronomers and the failure of the IUAA (International Union of Amateur Astronomers) to meet this need. [The substance of this contribution was given in Sky & Telescope,73, 482 (1987 November).The text was not received. – Eds.]
Opening the Sky to Everyone
Authors: Chanoir Joel
Published: July 2016

CEMEA [Centres d’Entraînement aux Méthodes d’Education Active – Centres for Training Methods of Active Education] exists to encourage better understanding of science among teachers, organisers of youth groups, leaders of summer camps, etc. Its activities with regard to astronomy were described.
Interesting Business in Astronomy
Authors: du Moutier Michel Lyonnet
Published: July 2016

Support from firms is of increasing importance in amateur astronomy. Two projects were described. In the first, a company running a winter resort in Argentina was persuaded to hold Halley observation sessions at their site in the Cordillera de los Andes. A similar event was later held by the same company at a new resort in southern France. The second project involved interesting a professional journal for construction engineers in producing a special issue devoted to Comet Halley. This was speedily exhausted, most of the demand for back numbers coming not from the engineers themselves but from their families.
Teaching Astronomy and the Vital Role of the True Amateur
Authors: Mills H. Robert
Published: July 2016

This contribution summarized the situation in the United Kingdom where there are 5 organisations that are concerned with astronomical observation, but where there are hopes that a single unifying committee may be formed. Practical work for pupils was essential and many examples of simple equipment and practical applications were shown.
Astronomical Education in Poland
Authors: Turaj Katarzyna
Published: July 2016

Astronomical education is undergoing a fundamental change in Poland with the introduction in 1987 September of a revised astronomy programme. Although previously taught as a separate subject, it was often neglected by pupils concentrating on examinations for other subjects. Astronomy is now treated as part of the physics course and will be taught to all grades of pupils. This contribution also described the encouragement of astronomy through school astronomy groups, summer camps and the Astronomy Olympiads, where the winners are excused from entrance examinations to university if taking astronomy or physics courses.
Astronomy and Computing in Spanish (Aragon) High Schools
Authors: Elipe Antonio , Ezpeleta Joaquín , Lanchares Víctor
Published: July 2016

Astronomy is an optional subject available at some schools, but is generally underfunded. A recent government campaign aims to increase the knowledge of computing and astronomy has been fruitfully linked with this. Details of three specific areas were given: computer-based training; modelling and simulation; and guided programming, where the pupil has to master both astronomical and computational problems.
Tailor-Made Messages: Astronomical Information for Diverse Audiences
Authors: Cornell James
Published: July 2016

The SAO offers a wide range of public-relations services. For example, research results may be transmitted, via reporters, to newspapers or television stations. More direct approaches include “Observatory Nights”, special events for children, series of popular lectures, and publication of lecture series as popular books. Television, radio and film are used whenever possible to provide information about general and specific events. Standard information packages answer many of the 5000 written requests received annually. Day-to-day queries are handled (in part) by an automatic telephone answering service. At the SAO’s Whipple Observatory in Arizona (site of the MMT), visits are by guided bus tours from the foot of the mountain 18 miles (32.5 km) away. Concrete pads have been installed at the base-camp for the use of amateur astronomers – perhaps the only amateur observing site connected with a major U.S. observatory.
The Role of the Observatoire de Paris, Meudon in Providing Astronomical Information
Authors: Floquet M. , Schmieder Brigitte
Published: July 2016

The three research centres (Paris, Meudon, Nancay) receive groups totalling about 10 000 visitors per year, consisting primarily of school-children and the general public. Tours begin with a slide-show and then visits to the instruments are guided by an astronomer. One-day courses for teachers are held at Meudon and Nancay once a month and observing evenings at Meudon. Open days are held frequently, and in May 1985, despite dreadful weather, 30 000 people visited Meudon. Each centre has prepared brochures describing its work, together with lists of postcards, slides and other material. Three slide-shows are available, and others are in preparation.
Nucleosynthesis and Mixing in Low- and Intermediate-Mass AGB Stars
Authors: Hollowell David , Iben Icko
Published: July 2016

The existence of carbon stars brighter than Mbol=-4 can be understood in terms of dredge up in thermally pulsing asymptotic giant branch (AGB) stars. As a low- or intermediate-mass star evolves on the AGB, the large fluxes engendered in a helium shell flash cause the base of the convective envelope to extend into the radiative, carbon-rich region, and transport nucleosynthesis products to the stellar surface. Numerical models indicate that AGB stars with sufficiently massive stellar envelopes can become carbon stars via this standard dredge-up mechanism. AGB stars with less massive stellar envelopes can become carbon stars when carbon recombines in the cool, carbon-rich region below the convective envelope.

Neutron capture occurs on iron-seed nuclei during a shell flash, and the products of this nucleosynthesis are also carried to the stellar surface. The conversion of 22Ne into 25Mg can initiate neutron capture nucleosynthesis in largecore mass AGB stars, but only if these stars can survive their large mass loss rates. The current estimates of nuclear reaction rates do not allow for appreciable neutron capture nucleosynthesis via the 22Ne source in lower mass AGB stars. The carbon recombination that induces dredge up in AGB stars of small envelope mass, however, also induces mixing of 1H and 12C in such a way that ultimately a 13C neutron source is activated in these stars. The 13C source can provide an abundant supply of neutrons for the nucleosynthesis of both light and heavy elements. While the existence of neutron-nucleosynthesis products in AGB stellar atmospheres can be understood qualitatively in terms of an active neutron source, the combination of nuclear reaction theory and evolutionary models has yet to provide quantitative agreement with stellar observations.
The Abundance of Oxygen in M92 Giants
Authors: Pilachowski Catherine A.
Published: July 2016

Studies of the carbon and nitrogen abundances in metal poor giants have generally supported the models of Sweigart and Mengel (1979) which indicate the action of meridional circulation in CN-processing metal poor red giant envelopes. Carbon et al. (1982) find the trends in the carbon and nitrogen abundances in M 92 stars to be at least qualitatively consistent with CN-cycle processing of the envelope, but stars at all phases of giant branch evolution have unusual, and unexplained, carbon and nitrogen abundances. The oxygen abundance is the missing piece of information which may explain what’s going on. Sweigart and Mengel’s models suggest that ON-processing might also occur in the most metal poor giants. The sample of giants in M 92 for which Carbon et al. have provided carbon and nitrogen abundances is ideal for the determination of oxygen abundances to look for the effects of ON-processing. Once the oxygen abundances are known, the sum C+N+0 can be computed to see if it is constant along the giant branch or varies from star to star.
White Dwarf Seismology: Inverse Problem of g-Mode Oscillations
Authors: Shibahashi Hiromoto , Sekii Takashi , Kawaler Steven
Published: July 2016

Since light variability in white dwarfs was first discovered twenty years ago, eighteen DA white dwarfs, several pulsating DB white dwarfs, and hotter pre-white dwarfs have so far been found to be pulsating variables. The most conspicuous characteristics of pulsations in these stars are that they seem to consist of multiple g-modes of nonradial oscillations. Attention should be paid to multiplicity of modes. Stimulated by the success of helioseimology, a research field called ‘asteroseismology’, in which we may probe the internal structure of stars by means of observations of their oscillations, is going to develop. How well such a seismological approach succeeds is dependent on how many modes are observed in each of stars. Since the number of modes of an individual pulsating white dwarf is larger than those of other types of pulsating stars but for the Sun, the seismological study may be the most promising as to the white dwarfs. In fact, by applying the asymptotic relations among eigenfrequencies of high order g-modes with low degree, the degreel, and the radial ordern, Kawaler(1987a,b,c) succeeded to get some constraints on the physical quantities of some of pulsating white dwarfs.
Winds of Hot Stars as a Diagnostic Tool of Stellar Evolution
Authors: Kudritzki R.P. , Pauldrach A. , Puls J.
Published: July 2016

Modern quantitative spectroscopy of hot stars has two aspects: the analysis of photospheric lines and stellar wind lines. The first one is meanwhile established as an almost classical tool to determine stellar parameters. NLTE model atmosphere and line formation calculations yield Teff, log g and abundances with high precision (see recent reviews by Husfeld (this meeting), Kudritzki (1987), Kudritzki and Hummer (1986), Kudritzki, (1985)). The second aspect, however, the quantitative analysis of stellar wind lines is still at its very beginning. For long time the stellar wind lines have been used to determine mass-loss rates and terminal velocities v∞ only. While these studies were pioneering and of enormous importance, it was also clear that very approximate calculations were done with respect to NLTE ionization and excitation and the radiative transfer in stellar winds. Thus, stellar wind lines could be used only in a more qualitative comparative sense, with no theory behind, which allowed the determination of precise and reliable numbers.