bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Formation of the Asteroids
Authors: Hills J.G.
Published: July 2016

Recently Anders (1965) has shown that the smaller asteroids are overabundant relative to their initial numbers because of the collisional fragmentation of larger asteroids. Allowing for this fragmentation, he has derived a reconstructed initial radius distribution. Although the reconstructed distribution only comprises a little more than 100 asteroids and consequently has a large statistical uncertainty as well as the uncertainty introduced by the reconstruction process, Anders finds that when displayed on a log-log plot, the distribution can be represented fairly well by a gaussian curve with a peak near radius R = 30 km. This work has basically been substantiated by Hartmann and Hartmann (1968), although Hartmann (1968) notes that a gaussian distribution underestimates the observed number of more massive asteroids. This suggests that the initial asteroid distribution function was probably broader than a gaussian function, but it still retains a distinct bell-like appearance.
Collisional Focusing of Particles in Space Causing Jetstreams
Authors: Trulsen Jan
Published: July 2016

Jetstreams probably played an important role at an intermediate stage of the formation of the solar system (Alfvén and Arrhenius, 1970). A Jetstream is defined here as a collection of grains moving in neighboring elliptical orbits around a central gravitating body and with the dynamics modified by the action of complicated collision processes among the grains themselves.

Three main types of collisions will take place in such a stream. Hyper-velocity impacts will lead to fragmentation of the grains involved. At lower impact velocities, the particles will retain their identities after the collision even if they might be deformed to some degree depending on impact velocity and internal structure of the grains. With still lower impact velocity, accretion can take place, the grains sticking together after collision to form larger grains. A common feature of these collision processes are that they will be partially inelastic. A certain fraction of the kinetic energy of the colliding particles will be spent on changing their internal structure. The internal kinetic energy in an isolated Jetstream thus will tend to decrease with time. The mass spectrum of the grains also will vary during the lifetime of a stream, the probability for accretive processes increasing with time.
Evolution of Comets into Asteroids?
Authors: Marsden B.G.
Published: July 2016

There has long been speculation as to whether comets evolve into asteroidal objects. On the one hand, in the original version of the Oort (1950) hypothesis, the cometary cloud was supposed to have formed initially from the same material that produced the minor planets; and an obvious corollary was that the main physical difference between comets and minor planets would be that the latter had long since lost their icy surfaces on account of persistent exposure to strong solar radiation (Öpik, 1963). However, following a suggestion by Kuiper (1951), it is now quite widely believed that, whereas the terrestrial planets and minor planets condensed in the inner regions of the primordial solar nebula, icy objects such as comets would have formed more naturally in the outer parts, perhaps even beyond the orbit of Neptune (Cameron, 1962; Whipple, 1964a). Furthermore, recent studies of the evolution of the short-period comets indicate that it is not possible to produce the observed orbital distribution from the Oort cloud, even when multiple encounters with Jupiter are considered (Havnes, 1970). We must now seriously entertain the possibility that most of the short-period orbits evolved directly from low-inclination, low-eccentricity orbits with perihelia initially in the region between, say, the orbits of Saturn and Neptune, and that these comets have never been in the traditional cloud at great distances from the Sun.
Possible Magnetic Interaction of Asteroids with the Solar Wind
Authors: Greenstadt Eugene W.
Published: July 2016

Investigation of extraterrestrial objects is habitually accompanied by the observation of extraterrestrial magnetic fields, which often have significant effects on the solar wind in the vicinity of the objects. Should we be surprised to find this experience repeated at an asteroid?

A recent study considered the conditions that would have to be satisfied by the surface magnetic field of a small planetary body at asteroidal distances so that the field would be an obstacle capable of stopping the solar wind or deflecting it sufficiently to generate a detectable magnetic interaction (Greenstadt, 1971).
Future Work
Authors: Gehrels Tom
Published: July 2016

In the past decade the question has been raised, at IAU meetings, as to whether more asteroids should be discovered, and the answer now is: “Yes, indeed, do discover as many comets and asteroids as possible.” Marsden gives strong encouragement to search for “lost” comets and asteroids. The more ephemerides known the better physical and statistical studies we can make. We have completion of the asteroids now to about 14 mag. With existing patrol instruments of about 25 cm opening, for instance at Indiana and in South Africa, the limiting magnitude for an extended program is about 16.
Theoretical Studies on Transition Wavelengths and Transition Probabilities
Authors: Dalgarno A.
Published: July 2016

A discussion is presented of some theoretical methods for predicting atomic transition wavelengths and transition probabilities that are especially useful for highly stripped ions. Particular attention is given to procedures involving model potentials and pseudo-potentials and to procedures involving expansions in inverse powers of the nuclear charge. The importance of relativistic effects is assessed. The results of some recent calculations are compared to experimental data. Theoretical studies of molecular absorption and emission are briefly summarized.
Ionization Equilibrium for Ions of Na, Al, P, Cl, A, K, Ca, Cr and Mn
Authors: Landini M. , Monsignori Fossi B.C.
Published: July 2016

Ionization equilibrium calculations, which have a number of astrophysical applications, have been computed by Jordan for the ions of C, N, O, Ne, Mg, Si, S, Fe, and Ni.

The aim of this paper is to extend the evaluation to other elements relevant to the investigation of the solar atmosphere. Ions of Na, Al, P, Cl, A, K, Ca, Cr, and Mn have been considered and the ionization balance has been computed for temperature from 104to 107K.

The computation is performed including collisional ionization, autoionization, radiative recombination and dielectronic recombination.
Wavelengths of Solar Lines in the 50–380 Å Region and their Identifications
Authors: Feldman U. , Behring W. , Cohen L.
Published: July 2016

In this work we decided to concentrate on the region 50–380 Å for which the grazing incidence grating spectrograph is the most suitable instrument. This portion of the spectrum contains many rather intense lines lying very close together which arise primarily from very highly ionized atoms in the solar corona. Wavelength measurements and identifications have been made for a portion of the lines, but for many of them, especially the weaker ones, the situation was not completely clear and many doubts existed. Therefore we decided to build a rocket spectrograph which would significantly improve the resolution and wavelength accuracy for lines in the solar spectrum. Thus, we attempted to achieve wavelength accuracy of 0.003 Å and to limit the instrumental broadening of the lines to 0.03 Å.
The Solar EUV-Emitting Plasma
Authors: Noyes R. W. , Withbroe G. L.
Published: July 2016

The extreme ultraviolet (EUV) solar spectrum is considered in this review to cover a decade in wavelength from about 300 Å to about 3000 Å. The lower end is close to the practical limit of normal-incidence optics, and the upper end is the approximate limit of visibility from Earth’s surface. The solar plasma that gives rise to emission within this interval is very complex and covers a huge range of physical conditions. Temperatures range from about 4 × 103 K (the temperature minimum in the low chromosphere, observed in the 1600 Å continuum) to about 4 × 106 K. (corresponding to emission of the FeXVI doublet at 335 and 361 Å). The density of the emitting plasma ranges from 1015 cm-3 in the upper photosphere to 108 cm-3 in the quiet corona. Major types of energy transport and deposition within the plasma include not only radiation, but also acoustic waves, magnetohydrodynamic waves, thermal conduction, and convective flow. Magnetic energy often completely controls detailed structure and energy balances within the plasma. Inhomogeneities are not a small perturbation on the overall structure of the plasma, but rather may completely dominate that structure. Extreme departures from local thermodynamic equilibrium (LTE) are the rule rather than the exception. (It is interesting to contrast this complex situation with that seen in the next wavelength decade, from 3000 Å to 3 μ, which includes the visible spectrum. With the exception of a few strong chromospheric lines, this radiation emerges from a comparatively isothermal (5000 K<T<6000 K), horizontally homogeneous, atmosphere in hydrostatic and radiative equilibrium, in which LTE is the rule rather than the exception.)
Models of Active Regions in the Transition Zone from UV Observations
Authors: Cantú A. M. , Poletto G. , Tagliaferri G. L.
Published: July 2016

The Harvard College Observatory UV spectroheliometer aboard the OSO-4 spacecraft has obtained the enhancement of active regions, i.e. the ratio of their intensity to that of the quiet Sun Ia and Iq, for several lines formed in the transition region between the solar chromosphere and the corona (The subscripts a an q indicate active and quiet regions, respectively.)
The Use of Synchrotron Radiation in the Energy Calibration of Astronomical Apparatus
Authors: Gurzadyan G. A. , Ohanesyan J. B.
Published: July 2016

The problem of energy calibration of astrophysical apparatus is essential for every or almost every space experiment. The utilization of synchrotron radiation from an electronic accelerator should perhaps be taken as an ideal solution of this problem, if of course, such a possibility is available.

Special equipment for the extraction of synchrotron radiation has been devised at the circular electron accelerator with a maximum electron energy of 6 GeV, in the Physics Institute of Erevan (Gurzadyan and Ohanesyan, 1972). The equipment is designed primarily for the energy calibration of astronomical apparatus operating in a vacuum and hard ultraviolet and X rays. However, the equipment can also be applied to a wide range of experiments relating to the physics of solids, crystallography, physics of thin films, X rays, etc.
Missing Solar Ultraviolet Opacity and Diatomic Molecules
Authors: Tarafdar S. P. , Vardya M. S.
Published: July 2016

The solar atmosphericmodel calculations incorporating absorptionby hydrogen and metals and Rayleigh scattering by hydrogen give larger specific intensity in the solar ultraviolet spectrum than that observed. This discrepancy has been interpreted as due to some unknown source(s) of opacity in this spectral region. We have, therefore, compared the absorption coefficient due to bands of nine diatomic molecules with that of metals and hydrogen in the ultraviolet spectral region at temperatures and pressures appropriate to the solar photosphere. The molecular band absorptions due to A-X bands of CO, SiO and OH and to B-X band of CH have been found to be larger than or equal to the total absorption by metals and hydrogen below 4000 Å and may be able to account for the missing opacity except possibly between 2500 Å and 3000 Å. Whether absorption due to some other molecular band or bands is responsible for the opacity in this wavelength interval is not certain.
The Expected behaviour of the Hydrogen Lyman Lines in Solar Flares
Authors: Švestka Z. , De Feiter L.D.
Published: July 2016

While the merging of the higher lines of the Balmer series emitted by solar flares is solely determined by the electron density, the merging of the high Lyman lines is determined both by the electron density, through Stark broadening of the line absorption coefficient, and by the total number of hydrogen atoms in the flare, through the effect of self-absorption. Preliminary results of model calculations indicate that two or more intensity measurements, each midway between two consecutive lines of the Lyman series (lines 3–4, 4–5, 5–6) allow the determination of the column density of hydrogen atoms in the ground state provided that the electron density is known. One can believe that in between the Lyman lines only the flare elements contribute to the measured intensity since excited interflare matter of much lower electron density produces line profiles of substantially smaller width. Thus the data in between the lines can be reasonably compared to the Ne values deduced from high members of the Balmer series.
Spectroscopic Techniques in X-Ray Astronomy
Authors: Speybroeck Leon Van
Published: July 2016

The catalog of X-ray sources now includes types I and II super-novae remnants, at least one pulsar, other periodic or quasi-periodic sources, starlike objects which emit primarily in X rays, normal galaxies, radio galaxies, Seyfert galaxies, a quasar, and an apparently isotropic extragalactic background. There is ample evidence that X-ray emission is characteristic of many of the most interesting objects in astronomy, and the background may have cosmological implications. This should not be too surprising, since significant X-ray emission occurs whenever high energy electrons interact, and high energy electron production is usually associated with explosive phenomena.

The most useful energy range for X-ray observations extends from about 200 eV to perhaps 10 keV. The low energy limit results from the absorption by the interstellar media, which of course varies from object to object; some typical cutoffs are given in Table I. The high energy limit, which is much more arbitrary, results from the usually observed rapidly decreasing emission with increasing energy, and also from the lack of important characteristic emission or absorption features above this energy range. In many cases, however, observations outside of this energy range are required to definitively identify a dominant source mechanism.
CNO Abundances and Nova Outburst Strengths
Authors: MacDonald Jim
Published: July 2016

Simple theories of hydrogen shell flashes on accreting white dwarfs are used to find the requisite conditions for classical novae. It is shown that enhancement of CNO abundances, relative to the Sun, is necessary for fast novae yet slow novae, such as DQ Her, can still occur with large CNO abundances. An analysis of observational data indicates that the white dwarfs in nova binaries have masses typically 1.1 Mʘ. For some old novae, the accretion rate, deduced from the accretion disk luminosity, is too high to permit a strong enough hydrogen flash to give the observed nova strength. Some possible resolutions to this paradox are suggested.

Recurrent novae are probably not thermonuclear runaways on accreting white dwarfs.
The Formation of Optical CNO Emission Lines in Cataclysmic Variables
Authors: Williams Robert E. , Ferguson Donald H.
Published: July 2016

Spectroscopic observations of CNO emission lines are presented for old nova systems, and possible excitation processes for the lines are considered. The Bowen fluorescence mechanism cannot generally be responsible for the strength of N III λ4640 because of the weakness of 0 III λ3429. Other CNO lines are observed which indicate that all of the lines are excited by resonance fluorescence of UV continuum radiation. Several nonfluorescent excited lines of carbon are also present in old novae, probably formed by recombination processes. The available data for the optical CNO lines suggest that non-solar CNO enhancements exist in quiescent novae, indicating that some of the binary systems may be evolved.
The Intermediate Polars
Authors: Warner Brian
Published: July 2016

Until 1976, cataclysmic variable star research proceeded with few requirements for the inclusion of magnetic fields in theoretical models. Although models for low-mass X-ray binaries stressed the importance of magnetic fields (Lamb et at. 1973) and there was an increasing number of known magnetic single white dwarfs (Angel 1977), and a magnetised white dwarf had been one of the models proposed to explain the rapid oscillations in DQ Her (Herbst et al. 1974, Katz 1975), there was no anticipation of the more general role that magnetic fields now seem destined to play. The two major reviews of the time (Robinson 1976, Warner 1976) scarcely considered the presence of magnetic fields.
The Origin and Evolution of Cataclysmic Binaries
Authors: Eggleton P.P.
Published: July 2016

Some cataclysmic binaries may be products of Case C evolution of low mass stars (orbital period ~ 1 yr; masses ~ 1 - 4 Mʘ), involving a common envelope phase. Other mechanisms, probably involving late Case B and even early Case B, but with significant loss of angular momentum, may be necessary to account for some evolved binaries such as AA Dor or V Sge. Further angular momentum loss, probably by magnetic braking coupled with tidal friction, causes secular evolution in cataclysmic binaries. It is suggested that tidal friction may account for the shortage of cataclysmics with periods ≲ 1.3 hr; but this cutoff, as well as the gap in the period distribution between 2 and 3 hrs, is hard to explain and imposes more severe constraints on possible theories than is commonly acknowledged.
Origin of Very-Short Orbital-Period Binary Systems
Authors: Miyaji Shigeki
Published: July 2016

Recent observations of four close binaries have established that there is a group of very-short orbital-period (VSOP) binaries whose orbital periods are less than 60 minutes. The VSOP binaries consist of both x-ray close binaries (4U1626-67; Middleditch et al. 1981 and 4U1916 -0.5; White and Swank 1982) and cataclysmic variables (AM CVn; Faulkner et al. 1972 and G61-29; Nather et al. 1981). Their orbital periods are too short to have a main-sequence companion. However, four binaries, none of them belongs to any globular cluster, are too abundant to be explained by capturing mechanism of a white dwarf. Therefore it seemed to be worth to present an evolutionary scenario from an original binary system which can be applied for all of VSOP binaries.
Basic Data on Hydrogen-Deficient Stars
Authors: Drilling J.S.
Published: July 2016

The current state of our knowledge on the distribution and motions of various types of hydrogen-deficient stars, and of their positions in the H-R diagram, is reviewed. It is concluded that the extreme helium stars (with the exception of the H-deficient binaries) and cool hydrogen-deficient stars belong to the population of the Galactic nuclear bulge, whereas the intermediate helium stars are young stars of Population I. The helium-rich sdO stars appear to be a local sample which is predominantly Population I.
Spectroscopic Analyses of Hot Extreme Helium Stars
Authors: Heber U.
Published: July 2016

Spectroscopic fine analyses of hot extreme helium stars are reviewed. The chemical composition is discussed in detail and conclusions as to the nuclear history of the atmospheric material are drawn. Evidence of inhomogeneities among the hot extreme helium stars is presented and it is concluded that the extreme helium stars can be found in the halo population (BD+10°2179) as well as in the disc population. Their mass loss rates are of the same order of magnitude (10−9 M⊙/yr) as those of normal stars. Four helium rich sdO stars are identified as possible descendants of the B-type extreme helium stars.
The Light Curve of the Pulsating Extreme Helium Star BD +13°3224: Further Evidence of a Decline in the Period Decrease Rate
Authors: Lynas-Gray A.E. , Kilkenny D.
Published: July 2016

Further optical and infrared (J-filter) observations are presented for the extreme helium star BD +13°3224. No infrared excess, which could have been attributed to a cool companion, is found. Very recent times of maximum light confirm the ephemeris cubic term already proposed. Current models for the evolution of BD +13°3224, while approximately accounting for the period decrease rate (Ṗ), do not explain the decreasing Ṗ indicated by the cubic term.
The RCB Stars and their Circumstellar Material
Authors: Feast M.W.
Published: July 2016

RCB stars are surrounded by circumstellar dust and gas moving radially outwards at ~200 km/sec. The circumstellar shell is made up of discrete puffs of matter, a typical puff occupying an area ~0.03 of a complete shell. On the average puffs are ejected about once every 40 days (comparable with the known pulsation periods of RCB stars). The reddening law of the dust indicates that it is composed of small carbon particles (radii ~100A). The flux from the shell at L typically varies by 1 to 3 mags over periods of 1000-2000 days. The average mass loss rate is ~10−6MO/yr.
Abundance Analysis of R CrB Variable UW Cen
Authors: Giridhar Sunetra , Rao N. Kameswara
Published: July 2016

Burrell (1976) performed an abundance analysis of the southern R CrB star UW Cen and reported a metal deficiency by a factor of 660 compared to the sun. However, his analysis was made employing very uncertain gf values, which resulted in lower estimates for Texc and Tion etc. We have reanalysed his data using new values and model atmospheres calculated by Schönberner (1975). Our analysis shows that the star has nearly solar abundance.
Spectrophotometric Observations of R CrB During 1972, 74 Minima
Authors: Rao N. Kameswara , Vasundhara R. , Ashoka B.N.
Published: July 2016

The spectrophotometric observations obtained in the wavelength range 3400A to 8000A during 1974, 1972 minima of R CrB have been fitted with Mie scattering calculations assuming sperical graphite particles and various size distributions. Power law type distributions fit the observations fairly well, and indicate that there is decrease in mean particle size as the star comes out of minimum.
3.0 To 3.5 Micron Spectrum of V348 Sgr and R CrB
Authors: Nandy K. , Kameswara Rao N. , Morgan D.H.
Published: July 2016

The circumstellar dust in R CrB stars is often thought to be due to graphite, because of the high carbon abundance in the stars. Further, the spectra of these stars in the infrared show feature-less smooth continuum (Forrest 1974, Roche and Aitken 1984) which was also thought to be characteristic of graphite. However, the recent comparison of the ultraviolet spectra obtained at maximum and minimum light of R CrB showed an extinction peak in the region of 2400 to 2500A (Holm, Wu & Doherty 1982, Hecht et al. 1984) which was identified as due to amorphous or glassy carbon particles. According to Duley and Williams (1981,83) amorphous carbon is supposed to show spectral features in the 3.3-3.4 μm region. Further many dust emission features are also supposed to appear in the spectral region 3 to 3.5 μm (Aikten 1981). The previous studies in this spectral region in R CrB (Forrest 1974) and in the hotter star V348 Sgr (Allen et al. 1982) showed smooth continuum. V348 Sgr shows spectroscopically many similarities with other WC 11 stars and was grouped with CPD-56°8032, He 2-113 and M4-18 (Webster and Glass 1974). All these three stars show strong dust emission features at 3.3, 8.6 11.25 μm. With a view to search for weaker dust spectral features we obtained the spectrum of R CrB and V348 Sgr with higher resolution than employed before.
Ry Sgr: Pulsation Related Phenomenon
Authors: Lawson W.A.
Published: July 2016

The absorption line splitting reported by Cottrell and Lambert has been shown to be associated with the semi-regular pulsations. The event has a time scale of about 10 days (0.23 of a period) occuring about the radial velocity reversal at minimum radius. The velocity reversal is more rapid than indicated in an earlier radial velocity analysis by Alexander et al. There is evidence that the phase of the line splitting event is similar to the phase of the onset of the obscurational light declines.
Anomalous UV-Extinction and the Effective Temperature of V348 Sgr
Authors: Schönberner D. , Heber U.
Published: July 2016

Our idea of the evolutionary state of the hot R CrB-star V348 Sgr is seriously restricted by our ignorance of its effective temperature. A direct determination from photospheric lines is very difficult, owing to contamination by emission lines. Using Johnson photometry, Houziaux (1968) estimated a spectral type of BO or Bl. This result was, however, based on the assumption that V348 Sgr behaves photometrically as a main sequence star. V348 Sgr appears, however, to be an extreme helium star since hydrogen absorption lines are completely absent (Houziaux, 1968). This conclusion has been strengthened by a study of Heber et al. (1984) in which IUE-spectra (low resolution) of V348 Sgr are compared with those of well-known extreme helium stars. From the similarity between these spectra, it was concluded that V348 Sgr must be a helium supergiant with an effective temperature of about 16000 K, though its (dereddened) spectral flux distribution differs in a peculiar way from that of HD 124448 which has about the same temperature. It should, however, be noted that the dereddening was performed by eliminating the λ = 2200 Å dip with Seaton’s law for the interstellar reddening. Obviously, the latter is not applicable when describing the extinction towards V348 Sgr.
Analysis of the Helium Strong Star HD 37017
Authors: Odell Andrew P.
Published: July 2016

High resolution and signal-to-noise spectra (0.22 A; S/N ≥ 50) of the H-alpha and He I 6678 A lines have been obtained over most of the cycle of the intermediate helium strong star HD 37017 with the Coude spectrograph and CCD camera at KPNO. These spectra are modeled with the non-LTE code of Mihalas to derive properties of the star. Both of the observed lines show small equivalent width variations on the previously known timescale of 0.901 days. The profiles can be simulated by a model with temperature 20,000K, log g=3.4, and helium number fraction 0.25, and which has a helium-rich spot of radius 40° and helium number fraction of 0.60 on the equator. Other possible models are discussed, as well as a model of the weak emission on the wings of H-alpha.
Helium Rich Subdwarf O Stars and Central Stars of Planetary Nebulae
Authors: Méndez R.H. , Miguel C.H. , Heber U. , Kudritzki R.P.
Published: July 2016

In this review we will discuss the hottest subluminous H-deficient stars, namely those with Teff> 30000 K. In the absence of reliable distance determinations for hot subluminous stars, the best way to discuss their properties and evolutionary status is to find their positions on the log g - log Teffdiagram. In the last few years, after extensive computational work, first in Kiel and more recently also in Munich, it has become possible to obtain log g and Teff, together with the surface He abundance, directly by fitting the observed H and He absorption line profiles with theoretical profiles obtained from non-LTE model atmospheres and associated line formation codes. The non-LTE models are plane-parallel, in hydrostatic and radiative equilibrium, and the atmosphere is assumed to consist of H and He only. A recent paper by Groth et al. (1985) gives most of the references on the application of this non-LTE model atmosphere approach to the study of all kinds of hot subluminous stars.
NLTE-Analysis of Three Extremely Helium-Rich O-Type Subdwarfs
Authors: Husfeld C. , Heber U. , Drilling J.S.
Published: July 2016

Three extremely helium-rich sdO stars (LSE 153, LSE 259 and LSE 263) were analyzed spectroscopically by means of detailed NLTE model atmospheres. These stars are very hot, with effective temperatures ranging from 70000 to 75000 K and gravities between log g = 4.4 and 4.9. Upper limits for the hydrogen abundance were also derived. The evolutionary status of the sdO stars is discussed and it is concluded that they evolve from the asymptotic giant branch towards the white dwarf stage. A possible evolutionary link between these hot stars and the extreme helium stars of spectral type B is discussed.
The Origin and Structure of the Magnetic Fields of the Chemically Peculiar Stars
Authors: Moss David
Published: July 2016

Rival theories for the origin of the magnetic fields present in the CP stars are discussed, particular attention being paid to the claims of the ‘contemporary dynamo’ and ‘fossil’ theories. The internal structure of the field as predicted by calculations consistent with the fossil theory is discussed at length. It seems that current time dependent models can now give a coherent picture of the fields of the CP stars according to the fossil theory. Dynamo theory modelling has not been developed in such detail. As yet neither the theoretical predictions nor the observational material seem to be detailed enough to allow a decisive comparison between the theories.
On the Spottedness, Magnetism and Internal Structure of Stars
Authors: Gershberg R.E.
Published: July 2016

It is hypothesized that kinematical structures within stellar interiors that are results of a self-organization of these interiors as thermodynamically open nonlinear systems constitute the physical basis for stellar magnetism.
The Magnetic Field and other Parameters of the Chemically Peculiar Stars
Authors: Yu.V. Glagolevskij , I.I. Romanyuk , N.M. Chunakova
Published: July 2016

The surface field Bs ( but not the effective Be one ) is responsible for different processes occuring in the magnetic stars atmospheres. For this reason it is natural that different investigators are interested in working out and improving methods of determination of Bs. Especially great attention attracts the method based on using the multicolor Geneva photometry. Cramer and Maeder have found a dependence between Bs and parameter Z of multicolor photometry wich they use for the estimation of the surface field. But it is necessary to investigate this method before application. Due to this reason we have put the following two problems:

A - The search for stars with a maximal predicted field

B - Examination of calibration of Bs (Z).
On the Magnetic Field of β CrB
Authors: Plachinda S.I.
Published: July 2016

We have discussed the oscillations of the magnetic field (He) of β CrB with a period P2=P1/5=3d.6974, where P1 is stimulated by a rotation of the star. The analysis of other author’s measurements has been confirmed the reality of P2.
Estimation of Stellar Surface Magnetic Fields by the Curve-of-Growth Method
Authors: Ryabchikova T.A. , Piskunov N.E.
Published: July 2016

The curve-or-growth method of estimating the stellar surface magnetic fields is applied to six Ap stars of different temperatures and one normal (or metallic-line) star σ Aqr. The values of Hs determined by the curve-of-growth technique are in good agreement with those obtained by the photometric method.
Inverse Problems in Astrophysics
Authors: Cherepaschuk A.M. , Goncharski A.V. , Yagola A.G.
Published: July 2016

The applications of the regularizing algorithms to the solving of inverse problems in astrophysics are presented.
Spectroscopy of CP Stars in the Groups of Different Age
Authors: Klochkova V.G. , Kopylov I.M.
Published: July 2016

The observational results for 108 stars, members of 10 galactic groups at the age range of lg t = 6,4 - 8,7 (years), are briefly described. It is shown that the peculiarity index, rotational velocity and magnetic field strength of all the types of CP stars do not vary during their evolution across the main sequence stripe.
The Variability of the λ5200 Feature in CP2 Stars
Authors: Maitzen H.M. , Hensbergb H.
Published: July 2016

32 stars have been checked for Δa variability, with the purpose to learn which factor(s) influence the strength of the λ 5200 continuum depression. One third of the stars appear to be constant within a range of 0.005 mag. The results on the remaining ones indicate that maximum strength is related to at least one of the magnetic poles, but spectral inhomogeneities are almost certainly responsible for the largest amplitudes.
Short Time Light Variations of Ap-Stars
Authors: Hildebrandt G. , Schöneich W. , Lange D. , Želwanowa E. , Hempelmann A.
Published: July 2016

Prom 1973 till 1981 sixteen Ap stars were investigated regarding to short time light variations with the twin telescope of the Zentralinstitut für Astrophysik stationed at the observatory Shemahka of the Academy of Science of Aserbaidshan. Only five of these stars show significant varyations with characteristical times in the region of 0.5 to 5 houres and amplitudes of about 0.01 mag. We will present here a short discussion of these five stars.
A Photometric Investigation of the Magnetic Star 53 Cameloprdalis
Authors: Muciek M. , North P. , Rufener F. , Gertner J.
Published: July 2016

Geneva photometry of the important and relatively well known Ap star 53 Cam (HR 3109, HD 65339) is presented. These 27 data, which cover rather evenly the rotational phase interval, are compared with the photometric data in ten bandpasses published by Musielok et al. (1980). They allow to show that at least four “null-wavelength regions” occur between 3400 and 7800 Å.
Computed Spectral Line Variations for Oblique Nonradial Pulsators
Authors: Baade Dietrich , Weiss Werner W.
Published: July 2016

Spectral line profiles are computed for nonradially pulsating CP2 stars. For a range which currently is thought to be typical for these stars, the influence of six parameters on the line profiles is considered: mode order ℓ and degree m, pulsation velocity amplitude, the angle between the rotation and pulsation axis, the angle between the rotation axis and the line-of-sight, and the phase angle of the rotation. In view of the expected low signal-to-noise ratio of observational data it is investigated to what extent easily measurable, simple quantities can still be useful in discriminating between different modes.
The Ultraviolet Spectral Energy Distribution of the Magnetic Ap Star Hd 170000 Inside and Outside of the Spots
Authors: Schöneich W. , Hempelmann A. , Želwanowa E.I.
Published: July 2016

Sixty five TD-1 scans of the magnetic silicon star HD 170000 have been investigated using the method for lightcurves analysis proposed by Hempelmann and Schöneich. The fluxes originating in two spots and in the rest surface of the star have been separated. The conclusion is that the whole stellar surface is strongly peculiar. Spot 1 is a region with the same peculiarity as the rest surface, but strengthened, whereas spot 2 shows additional peculiarities with respect to spot 1 and the rest surface.
A Search for Heavy Elements in the Ultraviolet Spectra of Ap Stars
Authors: Severny A.B. , Lyubimkov L.S.
Published: July 2016

The earlier attempts to detect the lines of heavy elements (Pb, U, Th and others) in the spectra of Ap-stars from the ground-based observations are briefly discussed. UV observations of Ap-stars with the ultraviolet telescope aboard ASTRON space station are described. The reduction of these data is considered. Three spectral regions containing the lines PbIIλ2203.53, UIIλ2556.19 and ThIIλ2368.05 were analyzed by the method of synthetic spectra. It has been shown that relatively cool Ap-star 73 Dra (Teff = 8l50 K) has a great overabundance (≥ 103ε⊙) of heavy elements U, Th, Pb and W.
β CrB – a Rosetta Stone?
Authors: Oetken L.
Published: July 2016

Combining the information from the speckle interferometric and spectroscopic binary βCrB a mass of 1.82 solar masses and an absolute visual magnitude Mv = 1m.42 is found, indicating that the star may be in that state of evolution, when the stellar core has shrinked after hydrogen exhaustion in it and the energy generation mainly comes from the envelope. The question whether all magnetic Ap stars are in that special evolutionary state is revived.
Some Structural Features of Magnetic Fields of the Chemically Peculiar Stars β CrB and α2CVn
Authors: Romanyuk I.I.
Published: July 2016

In spectra of chemically peculiar (CT) stars the weak lines originate at very different levels on the both sides of the Balmer jump (λB = 3646 A): τ ≈ 0.01 at λ > 3646 Å and τ ≈ 0.5–1.0, when λ > 3646 Å (Khokhlova, 1978)

To estimate the radial gradient of the magnetic field, we have observed two CP-stars β CrB and α2CVn. from 1979 to 1984 on the 6-meter telescope with an achromatic circular polarization analyzer (Glagolevskij et al.,1978). Compared with classical Zeeman analyzers, whose working wavelength band is only 300 Å, the achromatic analyzer covers a wide spectral region, enabling many more lines to be measured.

A combination of camera and grating was chosen so as record the 3300 - 4000 Å region all on the same plate at the 6.7 A/mm dispersion. Since the lines used to measure the field on either side of λ 3646 Å are exposed simultaneously on a single plate, one avoids many of the systematic errors arising from various positional, photometric and polarization effects, all these should influence the short and long wave ends of the spectrogramm identically.
The Abundance of Gallium in B-Type Chemically Peculiar Stars
Authors: Takada-Hidai Masahide , Sadakane Kozo , Jugaku Jun
Published: July 2016

Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, 8 He-weak stars, and 7 normal stars are made with the resonance lines of Ga II at 1414 Å and Ga III at 1495 Å in IUE spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper limits of the Ga abundance can be obtained for some stars. However these upper limits are much lower than those inferred from visual spectra. Among the 27 Hg-Mn stars, 17 stars are distributed in the range of 2.0 – 3.8 dex of overabundances of Ga. Ten other stars show upper limits less than 2.1 dex. Fifteen stars of 20 hotter Hg-Mn stars with Teff > 11000 K show high overabundances in a narrow range of 2.6 – 3.8 dex, while, among 7 cooler Hg-Mn stars, the only star HR 7775 shows the same overabundance as in these 15 stars. Of 11 Si stars, 9 stars have Ga overabundances ranging from 1.9 to 3.2 dex. Gallium is overabundant in 5 out of 8 He-weak stars in the range of 1.7 – 3.2 dex, while in the three other stars the upper limits are less than 1.3 dex. The Ga abundances in normal stars are all upper limits which roughly correspond to the solar value.
The Metallic-Lined Star 32 Aquarii
Authors: Kocer Dursun , Bolcal Cetin , Adelman Saul J.
Published: July 2016

Prelimary results from an optical region study of the metallic-lined star 32 Aquarii indicate Teff = 7600 K, log g = 3.10, ξ = 4.6 km s−1, and an iron abundance about one-half solar.
Charles Boyer and the Rotation of Venus
Authors: Dollfus Adouin
Published: July 2016

In August 1957, the magistrate Charles Boyer, who was President of the Court of Appeal at Brazzaville in Africa and an amateur astronomer, began to photograph the planet Venus systematically, using a violet filter and his own personal telescope, 256-mm in diameter, with an optical window. His aim was to study the positions of the dark, changing markings that had been detected in ultraviolet light by Ross at Mount Wilson in 1924. He was collaborating with Henri Camichel at the Pic-du-Midi Observatory, who was simultaneously observing with a 60-cm reflector. Over 68 days’ observation, Charles Boyer noted a periodicity of 4 days in the appearance of the markings. Alerted by this, Henri Camichel found the same effect on his series of images. Charles Boyer photographically added together the images on plates obtained at daily, 3-day, 4-day, and 5-day intervals (1). The combination of different images cause the markings to disappear. Only superimposition of 4-day images revealed any detail, the result of periodicity in the planet’s appearance.
The Instruments of H.E. Dall
Authors: Hysom E.J.
Published: July 2016

In 1926 Horace Dall commenced optical work, with interests covering both microscopes and telescopes. Soon (1928), he was making solid eyepieces of the Tolles type. Eventually he developed skills in making lenses of the smallest size to be incorporated into microscope objectives of the highest numerical aperture; this culminated in an objective with a N.A. of 1.92 (a record). The lenses were jewelled elements worked with diamond dust. During World War 2 he repaired all the microscope lenses damaged in the U.K. that had originated with the German firm of Leitz.

Horace Dall had an exceptionally inventive mind – and was so active in developing his ideas that he had insufficient time to formally write them up, hence much of his work remains unpublished. He did, however, keep extensive notebooks of his researches into optics. These, along with many prototypes, are now in the custody of the Science Museum, London. Combining his interests in travel, optics, and astronomy, Dall developed a number of portable, ultra-lightweight telescopes. He discovered that by incorporating what is in effect a long working distance, low-power microscope with a Cassegrain telescope he had an instrument with several advantages. The image was erect, the secondary small, and by use of a suitably placed internal stop, sky-flooding was eliminated without the use of shade tubes. Always looking for improvements in optical performance he hit on the idea of modifying the classical Cassegrain telescope by employing a prolate ellipsoidal primary mirror with a spherical secondary: independently discovered by Kirkham in the U.S.A. the type is now universally known as the Dall-Kirkham.
Contributions of Amateur Astronomers to Variable-Star Observing
Authors: Mattei Janet Akyuz
Published: July 2016

Astronomy is a unique field of science in which amateur astronomers have made and continue to make significant contributions.

One major area of the science of astronomy is the study of variable stars. There are more than 28,000 known and catalogued stars that change in brightness – variable stars – and about 15,000 suspected to be variable. These stars need continuous and systematic observing over decades to determine their behaviour and to record any of their unusual or rare activity. However, there are not enough professional astronomers or telescopes to observe these stars regularly. Therefore, variable star astronomy needs amateur astronomers to be the record keepers for these stars. It was for this reason that as early as 1844 and continuing throughout the second half of the nineteenth and early twentieth centuries, the astronomers F.W. Argelander of Germany, Sir John Herschel and J. Baxendell of England, D.F.J. Arago of France, and E.C. Pickering of the United States all advocated systematic variable star observing for amateur astronomers. The encouraging appeals from these leading professional astronomers resulted in the formation of several organized groups of variable stars observers, first in England – the British Astronomical Association (1890), Variable Star Section; then followed by the American Association of Variable Star Observers (1911); the Association Française des Observateurs d’Etoiles Variables (1921); the Royal Astronomical Society of New Zealand, Variable Star Section (1927); and the Japanese Astronomical Study Association (1945). Today, there are about 25 variable star observer groups around the world.
The Effects of Light Pollution on Amateur Astronomy
Authors: Crawford David
Published: July 2016

The rapid increase in urban lighting, with the resultant increase in sky glow due to this lighting, has already severely affected both professional and amateur astronomy. It is not possible to observe as faint as was possible in the past from sites anywhere near large cities. Even those sites near smaller cities are compromised.

There are other adverse effects of outdoor lighting. One in particular affects amateur astronomers (more than professionals, in fact). That is light trespass from a (usually) nearby source shining directly into the amateur’s observatory. It ruins dark adaption and can even affect photographic or photoelectric observations.

Astronomers are pushing for communities and individuals to apply “solutions”, which can help greatly. These are: use the correct amount of light for the lighting task, not overkill; use controls on the lighting, such as shielding and correct placement (direct the light downward), and time controls; use low pressure sodium light sources whenever possible (especially in the vicinity of professional observing sites).

Without the widespread application of such solutions, amateurs, professionals, and even the general public will likely lose forever their superb view of the universe, as seen from a prime dark sky site. These solutions also maximize the quality of any lighting installation, often at lower cost than bad lighting.
Using an Image-Intensifier in Astronomy
Authors: Midavaine Thierry
Published: July 2016

The use of an RTC XX1390 second-generation intensifier (which consists of a S20R photocathode, a micro-channel plate and a screen) was described. In visual work, very faint objects become visible. Photographically, an 18th-magnitude object has been detected through a layer of cirrus. The effective focal length used was 20 m, giving a resolution of 1 arcsecond, thanks to the short exposure times needed. With a Celestron C8 telescope, the coma of Comet Halley was photographed with 2-second exposures, allowing transitory phenomena to be detected. Used in conjunction with video techniques, high time-resolution images could be obtained, opening up the possiblity of new forms of observation of faint objects.
Searching for Variables, and Constructing a Slit-less Spectroscope
Authors: Dahlmark Lennart
Published: July 2016

Methods of searching for variables using a short-focal-length (30 cm) and stereo and blink comparators were described, together with the design of a simple slit-less spectrograph suitable for a Newtonian or Cassegrain telescope.
The Scientific Merit of Amateur Astrophotography
Authors: Celnik Werner E. , Riepe Peter
Published: July 2016

Astrophotography is only a small fraction of the broad spectrum of amateur astronomers’ work. With the development of high-sensitivity emulsions, amateur telescopes of large focal ratios and good quality, cheap multi-purpose cameras (both 35- and 70-mm), and intensive public relations work done by observatories as well as by individual, advanced amateurs, the methods and techniques of astrophotography have become accessible to all amateurs. With suitable equipment, experience, and familiarity with astronomical problems (e.g. by close contact with professional astronomers), they are even able to make valuable contributions to science.