bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of Comets at the Crimean Astrophysical Observatory
Authors: Chernykh N. S.
Published: July 2016

The cometary observing programme at the Crimean Astrophysical Observatory is described.
A Series-Solution Method for Cometary Orbits
Authors: Nacozy P. E.
Published: July 2016

A series-solution method for highly-eccentric perturbed orbits using a modified form of Hansen's method of partial anomalies is presented. Series in Chebyshev polynomials in the eccentric anomaly of a comet and the mean anomaly at an epoch of a planet provide a theory valid to first order with respect to the masses. The first-order solution becomes a reference solution about which higher-order perturbations are obtained by the method of successive approximations. The first-order solutions are valid approximations for long durations of time, whereas the higher orders are valid only over the interval of time that is selected for the Chebyshev expansions. The method is somewhat similar to Encke's method of special perturbations except that for each successive interval of time perturbations about a first-order solution are calculated instead of perturbations about a conic solution.
On the Motion of Short-Period Comets in the Neighbourhood of Jupiter
Authors: Chepurova V. M.
Published: July 2016

An intermediate orbit is developed for studying the hyperbolic jovicentric motion of a comet in the vicinity of Jupiter, where the effect of Jupiter's oblateness may become significant. A comparison is made with some of the results obtained by other investigators on the motions of specific periodic comets.
Nongravitational Effects on Comets: the Current Status
Authors: Marsden B. G.
Published: July 2016

A method for allowing for the effects of nongravitational forces on the motions of comets is summarized. Study of the motions of specific comets indicates that these forces act essentially continuously but have a high inverse dependence on heliocentric distance; there is also evidence for secular changes. The equations of motion employed are discussed in terms of the Whipple icyconglomerate model. Nongravitational parameters are tabulated for all 46 comets observed at three or more perihelion passages. We point out the particular problems that still exist for certain comets and suggest directions for future research.
A Non-Newtonian Orbit for Periodic Comet Borrelly
Authors: Yeomans D. K.
Published: July 2016

A non-Newtonian orbit has been determined for P/Borrelly which successfully represents all eight apparitions. Although this comet has a substantial secular acceleration in its mean motion, the transverse nongravitational force is time independent over the 64-yr observed interval.
The Chemical Composition of Cometary Nuclei
Authors: Shul'man L. M.
Published: July 2016

The probable parent-molecules of radicals such as C3 and N2+ are discussed, and it is concluded that cometary nuclei may contain complicated organic molecules, such as C3H4, CH2N2, and C4H2. It is suggested that these molecules are formed by radiation synthesis in solid phase. In a time interval of order 107 to 109 yr bombardment from cosmic rays would be expected to transform the chemical composition to a depth of 1 m. Solar cosmic rays do not penetrate as far, and as a result the surface layer of the nucleus can be enriched with unsaturated hydrocarbons. After a critical concentration of this explosive material is reached a further burst of solar cosmic rays can initiate an explosion and thus an outburst in the comet's brightness. This mechanism is the only one advanced to date that can explain the synchronism of the energy output over the whole nuclear surface.
Splitting and Sudden Outbursts of Comets as Indicators of Nongravitational Effects
Authors: Pittich E. M.
Published: July 2016

It is shown that sudden outbursts of comets, or even complete splitting of their nuclei into several parts, are rather frequent phenomena that need to be accounted for in the evolution of cometary orbits. The distribution of the points in which such events occur indicates that the tidal action of the Sun and Jupiter, and also solar radiation, are much more probable causes of these effects than are collisions with the asteroids. Splitting is found to be relatively more frequent for comets moving in hyperbolic orbits. The observed velocities of separation indicate that the disruption of the nucleus provides an effective mechanism for the ejection of the fragments from long-period into hyperbolic orbits, augmenting the loss by planetary perturbations. The outbursts can be responsible for smaller changes in the orbits, which after repetition might produce a quasi-secular variation.
Comets and Problems of Numerical Celestial Mechanics
Authors: Vsekhsvyatskij S. K.
Published: July 2016

A number of problems concerning the motions and orbital statistics of comets are suggested for numerical discussion.
A New Orbital Classification for Periodic Comets
Authors: Bielicki M.
Published: July 2016

A new classification for short-period comets is proposed – one based on minimum approach distances to the respective planets, rather than on aphelion distances.
Secular Perturbations on the Minor Bodies of the Solar System
Authors: Galibina I. V.
Published: July 2016

By means of the Gauss-Halphen-Goryachev method secular orbital variations have been studied for a period of 4000 yr (from −50 to +3950). The method has been applied to the periodic comets Halley, Brorsen-Metcalf, Pons-Brooks, Westphal, Olbers, Neujmin 1, and Encke. Investigations have demonstrated that the use of the method for most comets is not expedient as it does not allow for the possibility of approaches to the major planets and thus does not reflect the real evolution of the cometary orbits. Application of the method over the interval of 2000 years back from the epoch 1950.0 for the planets 279 Thule, 1162 Larissa, 1180 Rita, and 1202 Marina, as well as from the epoch 1850.0 for 1 Ceres has given adequate results and has displayed the stability of these orbits. Study of the secular perturbations on the Leonids over the interval of 4000 yr has confirmed the stability of that meteor stream. By means of the same method 14 minor meteor streams were investigated, and their orbits also proved to be stable. The availability of the various systems of osculating elements has permitted us to estimate for the first time the possibility of the encounter of those streams with the Earth over a 4000-yr period. For further details see Galibina (1970a, 1970b, 1971).
The Use of the Halphen-Goryachev Method in the Study of the Evolution of the Orbits of the Quadrantid and δ Aquarid Meteor Streams
Authors: Zausaev A. F.
Published: July 2016

The Halphen-Goryachev method has been used for estimating the elements of the orbits of the Quadrantid and δ Aquarid meteor streams 4000 yr back from the epoch of osculation. Three meteor orbits were selected for each stream: the mean orbit, based on data by Shelton (1965) and by Jacchia and Whipple (1961), and also two variants. Two cases were discussed: in the first case only the perturbations by Jupiter were taken into account, and in the second those by Jupiter and Saturn. Designating the initial epoch of osculation as the year zero, we compared our results for the Quadrantids with those by Hamid and Youssef (1963) at the final epoch (the year −4000). The disagreements in the elements i, ω, and Ω were 3°, 8°, and 1°, respectively (in absolute value). In comparing the mean orbits of the two streams it was noticed that between the years −800 and −900, and also between −2300 and −2400, the eccentricities and inclinations to the ecliptic were practically identical. However, the minimum differences in Ω and ω were 174° and 153° between −800 and −900, and 15° and 30° between −2300 and −2400. Consequently, if only secular perturbations are taken into account we cannot obtain a positive answer to the question of connection between the Quadrantid and δ Aquarid streams during the 4000-yr interval. The orbital changes caused by the Poynting-Robertson effect will be negligible for the meteors discussed and can be disregarded.
Orbital Evolution of the α Virginid and α Capricornid Meteor Streams
Authors: Kazimirchak-Polonskaya E. I. , Belyaev N. A. , Terent'Eva A. K.
Published: July 2016

The motions of two typical meteor streams of the Jupiter family, the α Virginids and the α Capricornids, were considered over the interval 1902–2003, perturbations by Venus to Neptune being taken into account. The substantial transformations of their orbits in Jupiter's sphere of action and its neighbourhood were studied. Conclusions are made concerning the role of large perturbations by Jupiter in dispersing meteor streams and altering the visibility conditions of meteor showers.
On the Relation Between Comets and Meteoroids
Authors: Alfvén H.
Published: July 2016

In order to understand the origin and evolution of the solar system it is especially important to study the small bodies – asteroids, comets and meteoroids – because in the planetesimal state (preceding the present state) the matter was dispersed.
Fast Variations of the Solar Rotation
Authors: Chistyakov V. F.
Published: July 2016

The rotation law of the Sun is often described by the Faye formula:

where ϕ is a heliographic latitude and a and b are constants. For a long time researchers have been studying the problem in what way the constants a and b change in time and in dependence on a phase of 11-year cycles.
Cyclical and Secular Variations of Solar Activity
Authors: Kuklin G. V.
Published: July 2016

It is difficult to prepare an invited paper on topics which are ABC for any specialist in Solar Physics. I considered my task as a systematization of a lot of information about cyclic and secular variations of solar activity rather than an account of new striking results in order to illustrate a certain concept. I beg your pardon in advance for possible defects in my report and for lack of time to quote all related papers.
Sequences of Large Sunspot Groups
Authors: Kotrč P.
Published: July 2016

The concept of a sequence of large sunspot groups is defined. From distribution functions of large groups from the period of sequences and that outside sequences it has been found that there are relatively more groups with a smaller maximum area in the period of sequences than in the period outside sequences. With an increased frequency of the occurrence of large sunspot groups on the solar disc their size decreases.
Solar Magnetic Fields and Convection: VII.A Review of the Primordial Field Theory
Authors: Piddington J. H.
Published: July 2016

We review the primordial field theory of solar magnetic fields (Papers I–VI) whose three main features are, first, a permanent dipole-like magnetic field, second a mainly toroidal field formed by shearing and rolling into individual, helically twisted ropes as suggested by Babcock, and third a mechanism for reversing the toroidal field. The theory explains numerous observational effects where the dynamo theory fails.

(i) An active region forms when a rope section emerges and expands layer by layer to form a rotating arch filament system and then spots. Only a rope model explains the radial inflow of magnetic elements to build up a spot, as well as the spiral structure and other features pointed out by Babcock. (ii) The model explains umbral and penumbral structures, the Wilson depression, Evershed flow, the sunspot energy deficit and the very slow loss of flux fragments by some sunspots. (iii) The model is then extended to background magnetic fields to show that surface magnetic fields are like the upppermost branches of a magnetic ‘tree’ whose trunk is a flux rope. This explains unipolar magnetic regions, ‘pepper and salt’, and ephemeral active regions. Tension in the submerged flux ropes accounts for the observed migrations of magnetic regions, active longitudes and magnetic longitudes. (iv) On a smaller scale spicules, mottles and other network elements are explained in terms of the tree structure. (v) The mechanism of reversal of the toroidal field system is explained and the manner of disposal of old toroidal fields. (vi) The basic error in the dynamo theory is discussed briefly. We point out that radical changes in dynamo theory have been suggested by Parker, but appear to have been ignored by others.
Synthesis of Classification Dispersion Spectra from Stellar Atmospheres Theory and from High Dispersion Spectra
Authors: Irwin A. W. , Bolton C. T. , Garrison R. F.
Published: July 2016

The ATLAS programme has been corrected and modified for use at low effective temperatures. A grid of unblanketed model atmospheres has been generated for the region G5-K5, V-II. A spectrum synthesis programme has been written for the calculation of flux vs wavelength for selected regions of the spectrum. Temperature distributions from the grid of continuum models and from published blanketed models will be used along with published oscillator strengths as input data for the spectral synthesis programme.

Spectrograms of MK standards have been taken at 12 Å mm−1 and 120 Å mm−1. The University of Toronto PDS microdensitometer system has been programmed to allow comparison between the synthesized spectra and the observed spectra to determine the effects of effective temperature, surface gravity, microturbulence, and abundance on classification criteria.
Derivation of Abundances Through Photometric and Spectroscopic Methods
Authors: Bell R. A.
Published: July 2016

Several points of detail which affect stellar abundance determinations are discussed. In particular, the importance of including the effects of hyperfine structure and isotopic shifts when considering the lines of some elements is stressed.

The abundance determinations for F dwarfs by Bell and Peytremann, who use theoretical calibrations for intermediate band photometry, and Nissen, who observes very narrow spectral intervals, are intercompared. The agreement between Bell and Nissen, who have 46 stars in common, is quite satisfactory.

Recent work on carbon and nitrogen abundances in cool stars is described. The suggestion of Hearnshaw, that [C/H] = 1.5 [Fe/H] for disc stars with −0.7 < [Fe/H] < 0.4, is compared with recent results by Clegg. Whilst Clegg's results are quite precise, they neither confirm nor deny Hearnshaw's suggestion. Work by Branch and Bell on K giants shows that [C/Fe] = 0, or a constant, for the stars in the sample. A value of about 7 for the C12/C13 ratio in the atmosphere of Arcturus has now been confirmed by several authors and Lambert and his collaborators have determined this ratio for several K giants.

The suggestion by Spinrad, Taylor and others that the M67 dwarfs are more metal-rich than the Hyades, i.e. that they are super-metal-rich or SMR, seems to be erroneous. However some SMR stars, such as 31 Aql, certainly exist even though there is still some uncertainty in the precise abundance of strong CN stars such as μ Leo.

Examples of synthetic spectra for metal-deficient giant stars are given and a theoretical colour-colour diagram is compared with observations of globular cluster and Draco stars.
A Test of the Accuracy of low Dispersion Objective Prism: Spectral Classification of Late-Type Stars Using DDO Photometry
Authors: Clariá J. J. , Osborn W.
Published: July 2016

A test has been made of the reliability of the multidimensional classification of late-type stars from low dispersion objective prism plates recently attempted by Stock and Wroblewski. Such classification at low dispersion is difficult due to the problem of separating the effects of luminosity from those of abnormal metal abundance. A sample of the stars classified by Stock and Wroblewski as metal weak (pec) and of those classified as luminous stars (class I) were observed using the DDO intermediate-band system. The photometry shows that the stars classified as pec are indeed population II giants, of low metal abundance ([Fe/H] < −1.0). The stars classified as I, however, were found in general not to be true supergiants but rather a mixture of various types of giants, such as CN strong stars, with spectral features that resemble, in one way or another, those of higher luminosity stars.
Abundance Effects in the Classification of K Stars
Authors: Williams P. M.
Published: July 2016

The influence of metal abundance and gravity on the relation between spectral type and effective temperatures of late G and K type stars is investigated and calibrated using metal abundances from narrow-band photometry, near infrared photometry and independent luminosity estimates.
Comparison of Colour Curves of Mira Stars of Spectrum M and S
Authors: Payne-Gaposchkin C.
Published: July 2016

Colour variations for Mira stars of spectrum Me and Se are deduced from the two micron survey of Neugebauer and Leighton and concurrent visual observations of the same stars.

The colours change cyclically during the periodic change of brightness. Colour is a function of maximal spectrum and also of period. Mira stars of class Se are bluer than those of Me of similar period.
The Colour Excess Scalf and Intrinsic Colour Properties of the Longer Period Cepheids
Authors: Canavaggia R. , Mianes P. , Rousseau J.
Published: July 2016

Following a discussion of two recent papers by Schmidt (1973, 1975), we conclude that for the large amplitude, longer period Cepheids (log P greater than about 1.1), the small colour excesses derived from the six-colour photometry (traditional method or Parsons method) are to be preferred to the large colour excesses derived from the γ-index photometry (Kraft's scale).
A Method for Determining the Chemical Composition Parameters (X, Y, Z) of Galactic Clusters
Authors: Osborn Wayne , Clariá Juan J.
Published: July 2016

A method is described by means of which the chemical composition parameters (X, Y, Z) may be derived for galactic clusters that contain evolved red giant members and for which the cluster reddening and distance moduli are known. The method is based on observations of the evolved stars utilizing the DDO intermediate-band system. First, the DDO photometry by itself allows one to separate with a high degree of certainty the physical members of the clusters from the field stars. In cases where membership in the cluster can be confirmed, the unreddened DDO colours can be used to obtain the effective temperatures, surface gravities and metal abundances (Z) of the stars. These data combined with the absolute magnitudes available from the distance modulus permit the masses to be calculated. Finally, if some of the observed red giants form part of a clump on the giant brach in the HR diagram, the helium abundance (Y) of the clusters can be estimated by comparing the derived physical parameters of these stars with theoretical models. An example of the application of the method to the galactic cluster NGC 2420 is given.
HD Stars South of δ = −53° Having Peculiar Abundances: Statistics and Notation
Authors: Houk N. , Hartoog M. R.
Published: July 2016

The HD stars between δ = −90° and −53° have been classified on the MK system, using Michigan 4° +6° objective-prism Schmidt plates (108 Å mm−1) taken at Cerro Tololo, Chile, and the results are published in Vol. 1 of the University of Michigan Catalogue, Catalogue of Two-Dimensional Types for the HD Stars. First, various statistics on the 32 500 normal stars and 2500 peculiar stars found are presented. Peculiar/normal ratios for various types of stars are given, along with discussion of the assumptions made. About 40% of the peculiar stars are of the Am or Ap types, and these will be covered in detail. Secondly, what notation to use for spectral types of stars with peculiar abundances is discussed and an explanation given of the notation used in Vol. 1 of the Michigan Catalogue for Am, Ap, strong and weak CN, weak metal, and other categories of peculiar stars.
The Spectral Type of HD 101065
Authors: Przybylski A.
Published: July 2016

The eighth magnitude star HD 101065 has an extremely peculiar spectrum dominated by numerous lines of the rare earths and lacking the lines of ‘normal’ elements, such as iron peak elements and lighter elements. For this reason it cannot be fitted into the adopted framework of spectral classification. The spectral type of this star can be defined only by fixing its effective temperature, which is 6040 ± 100 K. However, because of the extremely high blanketing the temperature of the continuum is about 450 K higher. This means that HD 101065 is a late F type star.
Classification of Stars with Different Chemical Constitution
Authors: Chalonge D. , Divan L.
Published: July 2016

The possibility of obtaining a segregation between stars of different chemical constitution using the BCD classification is reviewed.
Infrared Lines in Peculiar Emission-Line Stars
Authors: Andrillat Y. , Houziaux L.
Published: July 2016

An image-tube Cassegrain spectrograph, equipped with an S-1 photocathode enabled us to obtain infrared spectra of peculiar emission-line objects, as V 1016 Cyg, HBV 475, HD 51585, HD 45677, XX Oph and CI Cyg. Many of these objects display emission lines of H I, He I, He II, O I, N I, Ca II [S II] [S III], [Fe II]. The line intensities can be used together with data from other parts of the spectrum to determine relative abundances of these ions in the shells of these objects, which may be at a critical phase of their evolution.
Conflicting Evidence on the Composition of Am Stars
Authors: van 'T Veer Claude , Burkhart Claude
Published: July 2016

Our programme involves the study of Am stars of differing temperatures and luminosities as well as of the Am stars deviating from the positions of the classical ones in the photometric diagrams. We have found for certain stars a significant disagreement between the so-called ‘abundance indices’ and the abundances determined at high dispersion. Often giants or spectroscopic binaries, or stars with a detectable rotation, are involved. However, there are no consistant relationships between these different peculiarities and the observed disagreements. We shall give some examples of stars studied by us. Are these ‘abundance indices’ really what they are supposed to be in all cases? In which cases are they not and why?
Abundances in Stellar Populations
Authors: Spinrad H.
Published: July 2016

Stellar abundances are reviewed with emphasis on large-scale effects which may yield clues to galactic structure and evolution. Spectroscopic and indirect photoelectric abundance criteria are discussed, and utilized.

The abundance statistics of nearby galactic disk stars, dominated by M dwarfs, but observed at spectral types F and GV and K III, suggest a weak age-abundance relationship with a substantial dispersion at any time. Very metal-poor stars are extremely rare. Spatial abundance gradients, with higher metal abundances occurring nearer the galactic centre, are indicated. Disk abundance gradients are prevalent for light elements in other Sb and Sc galaxies.

The confusing status of supermetallicity is again reviewed. The super-metal-rich (SMR) giants (like μ Leo) are either over-abundant because of self-N-enrichment (from C–N–O processing?)and boundary-temperature cooling, or are really SMR. Each case may be reasonably argued. The old galactic clusters M67 and NGC 183 seem, by recent indirect acclaim, to be only slightly more metal-rich than the Sun. The Spinrad-Taylor data on the M67 giants would still seem to superficially suggest overabundances in Na and Mg, but other interpretations are possible.

SMR dwarfs, like HR 72, and subgiants, like 31 Aql are surely very old, and have metal abundances larger than the Hyades. However, they are, by number, only ≈ 5% of the local main sequence.

The galactic halo star tracers – red giants and RR Lyrae stars, have been observed extensively, lately. There is some indication of an abundance gradient from 5 or 10 kpc galactocentric radius out to r ~ 100 kpc. The most metal-poor stars observed in the Draco system are about 1000 times less abundant in heavy elements than is the Sun, and much of the galactic disk.

Abundances in other galaxies, as a function of their total mass, and stellar/gaseous composition are also reviewed. There is a clear dependence of abundance on galaxian total mass.
Some Comments on the Age – Abundance Relation
Authors: Grenier S. , da Silva L. , Heck A.
Published: July 2016

From the results obtained with the tri-dimensional quantative classification method of Spite (1966), the relation age-abundance is analyzed for the Galaxy. The dispersion on the abundance for stars at a given age appears to prevail over a possible relation between the age and the abundance for these stars. From a detailed analysis of eight F2-G2 stars, it appears that the index Δm1 is sensitive to microturbulence velocity.
Molecular observations of shocks and outflows
Authors: Bachiller R.
Published: July 2016

We discuss recent high-sensitivity observations carried out with the IRAM instruments of the shock chemistry associated with bipolar outflows. We highlight the recent mm-wave studies of L1157, a highly-collimated outflow driven by a Class 0 source. These observations illustrate nicely the chemical segregation produced by the outflow. Different molecular lines are observed to trace different components of the gas. Some molecules are abundant in the quiescent medium but are not observed in the shock (e.g. C3H2, N2H+, H13CO+, DCO+), whereas some other molecules are very enhanced at the shocked region (e.g. SiO, CH3OH, H2CO, HCN, CN, SO, SO2, H2CS). We briefly discuss the chemistry of the most important molecules, devoting special attention to the species which are thought to be abundant in interstellar ice mantles.
X-ray ionization of protostellar disks
Authors: Glassgold A.E. , Igea J. , Najita J.
Published: July 2016

X-rays from young stellar objects can influence the physical properties of their surroundings. A particularly interesting example is the ionization of the accretion disk by hard X-rays at distances of the order of 1 AU or more. We show that X-rays induce a layered ionization structure in which the outer layer is sufficiently ionized to permit the Balbus-Hawley instability to operate and to allow accretion.
The impact of comet D/Shoemaker-Levy 9 with Jupiter
Authors: Weaver H. A.
Published: July 2016

The collision of comet D/Shoemaker-Levy 9 with Jupiter in July 1994 was an unprecedented opportunity to witness a phenomenon that was ubiquitous in the early solar system and which continues to shape its evolution. The tidal breakup of the comet, and the subsequent evolution of its fragments, have provided important insights into the nature of cometary nuclei, although conclusions regarding the comet's fundamental properties remain controversial. Detailed models describing the passage of the fragments through the jovian atmosphere have been fairly successful in explaining many aspects of the observations, including the appearance of giant plumes extending >3000 km above Jupiter's limb, the huge infrared signals following the splashback of material into the jovian atmosphere, and the formation of dark impact scars over large regions at mid-southern jovian latitudes. New chemical species (e.g., CO, H2O, S2, CS2, CS, OCS, HCN, C2H4, and possibly H2S) were created in Jupiter's atmosphere due to the shock heating of the mixture of cometary and jovian gases. The large NH3 enhancement in the jovian stratosphere was apparently caused by heating of the ambient NH3 cloud followed by upwelling. The presence of metal atoms and ions in the jovian atmosphere was an unmistakable signature of the comet. Photochemistry may have played an important role in the temporal evolution of the newly-created species. The appearance of expanding rings emanating from the impact sites was originally explained as the propagation of gravity waves, but this required an oxygen abundance in the deep jovian atmosphere that was ∼10 times solar, an hypothesis that has been apparently contradicted by recent results from the Galileo probe. Although the impacts clearly produced dramatic effects in Jupiter's atmosphere, most traces of the trauma were barely discernible one year later.
Interstellar dust grains - an overview
Authors: Henning Th.
Published: July 2016

During the last years our knowledge about the structure and chemical composition of cosmic dust grains has very much deepened mainly driven by the rapid progress in infrared observations, laboratory experiments, and a much better theoretical treatment of grain evolution and the microphysical interactions of solid particles with gas, radiation, and with each other. This contribution will review the progress in the understanding of cosmic grains especially concentrating on the different grain populations, the physical processes which they link together, and the morphological and chemical structure of the particles.
Optical and ultraviolet observations of diffuse interstellar clouds
Authors: Meyer David M.
Published: July 2016

Absorption-line studies of diffuse interstellar clouds have recently been invigorated at ultraviolet wavelengths with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope and at optical wavelengths with efficient high resolution spectrographs and CCD detectors. These instruments have made it possible to explore new regimes in determining the atomic and molecular abundances of diffuse clouds and tracing the velocity structure of interstellar lines. In the case of the atomic gas, the abundances of elements as diverse as oxygen and krypton have been accurately measured with GHRS and are consistent with a local ISM whose metallicity is about 2/3 that of the Sun. GHRS has also provided new insight on molecular processes in diffuse clouds through observations of CO, C2, HCl, and vibrationally-excited H2. With velocity resolutions of 0.3 km s−1 now attainable, optical spectra of species like CH, CH+, and CN are beginning to probe the physical characteristics of diffuse clouds in detail. Similar spectra of interstellar Na I toward resolvable binary star systems have recently revealed a rich variety of small-scale structure in the cold diffuse gas.
Chemical models of AGB winds
Authors: Cherchneff I.
Published: July 2016

We present chemical models of the inner circumstellar envelope of a typical carbon-rich AGB star. The effect of pulsation-driven shocks on the gas close to the stellar photosphere is considered. The chemistry of dust condensation nuclei formation is described and applied to the gas layers close to the star. We derive formation yields for polycyclic aromatic hydrocarbon (PAH) species and their dimers and discuss their role in the condensation of dust. Models of the chemistry of silicon- and sulfur-bearing molecules in the inner envelope are also presented.
Chemistry in planetary nebulae
Authors: Cox P.
Published: July 2016

We review the properties of the molecular envelopes of planetary nebulae with an emphasis on the on-going chemistry which takes place in these regions.
High-Speed Photometry of Cluster Flare Stars
Authors: Rodonò M.
Published: July 2016

Recent photoelectric observations made at Catania Observatory show a high occurrence of short-lived faint flares on the Hyades member II Tau (H II 2411). Its activity level turns out to be higher than for UV Cet-type stars of equal absolute luminosity.

II Tau could represent a transition prototype between UV Cet-type flare star in the solar neighbourhood and cluster ones.

The importance of coordinated photoelectric patrol of properly selected flare stars in clusters of different age is emphasized.
Possible Groupings of Irregular (Orion) Variables
Authors: Dolidze M. V.
Published: July 2016

New groupings of Hα-emission stars connected with young clusters, associations and nebulae are considered to be possible regions of clusterings of irregular (Orion-type) variables. They are listed in Table I and an example, No. 19, is shown in Figure 1.
Spectral and Polarimetric Investigation of RCB Stars
Authors: Orlov M. Ya. , Rodríguez M. H.
Published: July 2016

Spectroscopic and polarimetric observations of the RCB variables DZ And, R CrB and XX Cam are described. DZ And is not a RCB-type star.
Cool Carbon Stars in Open Clusters
Authors: Alksnis A. , Alksne Z.
Published: July 2016

By combining lists of carbon stars with the catalogue of open clusters (Alter et al., 1970), a list of variable carbon stars, being probable members of clusters is given. The number of stars is too small to derive reliable statistics on cluster membership. Too few radial velocities are yet available. Photometric criteria are still too inaccurately known.
Physical Classification of Short-Period Variables
Authors: Jones D. H. P.
Published: July 2016

It is widely accepted that pulsating variables with periods less than 0.2 day fall into two distinct groups. These defined by Kukarkin et al. (1969) as, firstly,

RRs:RR Lyrae type variables with the period not exceeding 0d.21 (dwarf Cepheids). Belong to the population of the disk, are absent in clusters. Their luminosity is 2m–3m fainter than the luminosity of RRab and RRc stars. A typical representative – SX Phe.

and secondly,

δSct:δScuti type stars. Pulsating variables of spectral class A (late sub-classes) and F, the amplitudes of light variation do not exceed, as a rule, 0m.1 (rarely up to 0m.3). The form of light curve strongly varies usually. According to many characteristics resemble dwarf Cepheids, but differ from them by the small amplitudes. Are met in the Hyades-type clusters. Similar to the RRs type stars their periods do not exceed 0d.2. A typical representative – δSct.
On the Chemical Composition of Wolf-Rayet Stars
Authors: Nugis T.
Published: July 2016

The chemical composition of 5 WR stars in Cygnus are considered by using the quasi-nebular variant of Beals' model. On the basis of the general considerations which follow from this model it was concluded that the C/He ratio for the WC stars appears to be more than 10 times higher than for normal OB stars and the N/He ratio in the case of the WN stars seems also to be somewhat higher than for normal OB stars. From the solution of the equations of statistical equilibrium for the level populations, it was found that in the case of the WC stars C/He≈1 and in the case of the WN stars N/He≈0.05–0.1. For the star HD 192163 (WN6) it was found that He/H≈4.2–7.3 and for the other stars He/H≳10.
Nonstationary Processes and Magnetic Field Generation in Binary Stellar Systems
Authors: Dolginov A. Z.
Published: July 2016

This note gives introductory remarks to the three papers mentioned in the references.
Photometric Properties of V 1329 Cygni
Authors: Arhipova V. P. , Mandel O. E.
Published: July 2016

Light curve and position of V 1329 Cyg in the colour-magnitude diagram are discussed.
Observations of the Peculiar Emission-Line Objects with Infrared Excess HD 45677, HD 87643 and GG Carinae
Authors: Swings Jean-Pierre
Published: July 2016

Spectroscopic data in the visual region is described for the peculiar emission-line objects with IR-excess HD 45677, HD 87643, and GG Car. A model consisting of a central star surrounded by an equatorial disc and a dust shell is suggested.
The X-Ray Sources Sco X-1 and Cyg X-2 as Binaries
Authors: Lyuty V. M.
Published: July 2016

The analysis of photometric observations of the X-ray source Sco X-1 leads to the conclusion of the existence of a periodic component in the light variations of this source. For 1966–74, the results can be presented as

The photoelectric observations of some authors are shown in Figure 1, using the period. Figure 2 shows the mean light-curve of Sco X-1. The amplitude ΔB is about .
The Identification and Ubv Photometry of the Visible Component of the Centaurus X-3 Binary System
Authors: Krzemiński W.
Published: July 2016

The optical component of the pulsating binary X-ray source Cen X-3 is identified with a faint,  = 13.35, heavily reddened variable star lying slightly outside the 3rd Uhuru Catalogue error box. It shows a double peaked light curve with an amplitude of about 0.12 mag. which agrees both in period and phase with the X-ray data. The shallower minimum coincides in time with the X-ray pulsar eclipse. Interpretation of the light curve leads to the conclusion that the contribution from gravity darkening dominates to a large extent the reflection effect. The estimated distance to Cen X-3 is about 8 kpc.
Period Changes of RR Lyrae Stars in Globular Clusters
Authors: Szeidl B.
Published: July 2016

The dependence of the period changes of RR Lyrae stars, especially in globular clusters, on the evolutionary track through the instability strip has still found no explanation. The present paper is an attempt to give a review of the observed phenomena.
Some RR Lyrae Variables with Blažko Effect
Authors: Chis G. H. , Ureche V.
Published: July 2016

Observations of some RR Lyrae stars with varying periods and shapes of the light curves were discussed. These are:

TU Com (Ureche, V., 1965)

WY Dra (Chis, D., Chis, G. H., and Mihoc, I. (1974))

SW Psc (Ureche, V. (1971a, b))
Variability of the Emission-Line Spectrum of the Nucleus of the Seyfert Galaxy NGC 7469
Authors: Pronik I. I.
Published: July 2016

It is shown that the emission lines of the NGC 7469 nucleus spectrum are variable. Time variability of hydrogen lines is less than 20 days. The Hα emission line is at the profile base about a factor of two narrower than the Hγ line. Estimation of the density of hydrogen envelope, where Balmer lines wings were emitted, gives the value of about 108–109 cm−3.
Spectroscopic Observations of Be Stars in the Near Infrared
Authors: Polidan R. S. , Peters G. J.
Published: July 2016

The results of near infrared spectroscopic observations of over 120 Be stars are presented. In particular, the O I lines at λ 7774 and λ 8446 Å and the Ca II triplet (λ 8498 Å, λ 8542 Å, and λ 8662 Å) are discussed. The presence of emission at O I λ 7774 Å is shown to correlate with Fe II emission. Shell absorption at this line is found to be similar in appearance to that found in the photospheric spectra of supergiants. The O I λ 8446 Å line, the result of a fluorescence with Lyman β, is briefly discussed in connection with Be envelope dimensions. The paradox presented by the presence of strong Ca II triplet emission without H and K emission is discussed. The implications of this phenomenon on the structure of Be envelopes and possibly the binary nature of some Be stars is discussed.

Evidence indicating the presence of cool companions to the Be stars HD 218393 and HR 894 is presented.
The Surface Gravities of Be Stars
Authors: Peters Geraldine J.
Published: July 2016

In an attempt to shed some light on the origin of the material in the envelopes of Be stars, surface gravities were determined for 30 objects by comparing their observed profiles of Hγ and Hδ with those computed from the Princeton model atmospheres and the VCS theory of hydrogen line broadening. The program stars are predominately well-known Be stars and display a wide range of envelope spectra and v sin i. The mean and range in log g for the Be stars appear to be identical to that obtained from a similar analysis on non-Be stars. No correlation was found between log g and Hα emission strength or the strength and/or presence of emission of Fe II, O I λ 7774 Å, or the infrared Ca ii triplet. The suggestion made by Schild (1973) and Schild et al. (1974) that the extreme Be stars are in the post main sequence phase of rapid core contraction is weakened by the fact that there are several members of the class which have log g ≥ 3.8. All shell stars considered in the program appear to have low values of log g (≤3.5). Some possible explanations for this occurrence are discussed.
Pleione as a Variable Star
Authors: Sharov A. S. , Lyuty V. M.
Published: July 2016

The well-known shell star Pleione is also an interesting variable star, BU Tau. Its variability was first discovered by Calder (1937) from photoelectric observations in the 1930's. The light curve of this star from the end of the 19th century to 1954 was studied by Binnendijk (1949, 1955). Botsula and Sharov (1959) and Sharov (1961) added some old and new observations and continued the light curve up to 1959.
Ultraviolet Observations of Rapidly Rotating B-Type Stars
Authors: Heap Sara R.
Published: July 2016

Evidence of anomalous C – N abundances in the atmospheres of six rapidly rotating B-type stars has been found from an LTE analysis of ultraviolet line spectra obtained by Copernicus. Such anomalies are in the direction (carbon depletion, nitrogen enhancement) predicted by Paczyński (1971), but the extent of the anomaly grows toward earlier spectral type, contrary to Paczyński's predictions.
The Far Ultraviolet Spectra of υ Cyg and μ Cen
Authors: Peters Geraldine J.
Published: July 2016

The spectra of the ‘pole-on’ Be stars υ Cyg and μ Cen have been observed in the region λλ 1000–1450 Å with the Princeton Ultraviolet Spectrometer on board the Copernicus satellite. The data include scans of intermediate resolution (0.2 Å) with U2 and high resolution scans (0.05 Å) of selected suspected shell lines with U1. The spectra of υ Cyg and μ Cen are compared with a complete intermediate resolution Copernicus scan of the equator-on Be star φ Per. The ultraviolet spectra of υ Cyg and μ Cen appear to be identical to those observed in non-Be stars of comparable ground-based spectral type. Neither emission nor shell features are observed. However, numerous strong shell features are seen in φ Per. An upper limit on the column density of hydrogen in our line of sight is computed for υ Cyg from the observed strength of a weak feature at λ 1130.4 Å identified as an Fe III shell line. Estimates for the dimensions of the circumstellar envelope are then obtained. Some implications of the strengths of the Fe III shell lines at λ 1130 Å observed in υ Cyg, μ Cen, φ Per, and other Be stars are discussed.
Paschen Decrements in Be Stars
Authors: Briot D.
Published: July 2016

We searched for the general properties of the Be stars with Paschen emission lines. First, we obtained a relation between the infrared excess of the Be stars and the presence of emission in the Paschen lines. Until now, these emission excesses could be related to no physical characteristics of classical Be stars. Then, the measures of Paschen decrements of 12 stars whose spectral types range from B0e to B5e allowed us to check several theoretical calculations about the formation of emission lines in the envelopes of Be stars. Thus we can see the prominent part played by the electronic collisions in the Sobolev theory. Indeed, only with calculations taking the electronic collisions into account, can we obtain theoretical values agreeing with both measured Paschen and Balmer decrements for the hottest stars of our sample. However, no theoretical values agree with the observed decrements for the cooler stars.
The Classification of Faint Be Stars
Authors: Allen David A.
Published: July 2016

Faint emission-line stars found on Hα surveys are usually classified as planetary nebulae or Be stars on rather arbitrary criteria. A comparison of spectra of such stars with their optical and infrared properties suggests that a next step in their classification can be made quite rapidly by photometry. In particular the more unusual specimens can be readily isolated.
Polarization in Be Stars: (Review Paper)
Authors: Coyne George V.
Published: July 2016

A review of polarization produced in the extended circumstellar disks about Be stars is given. While variability of the polarization and its peculiar wavelength dependence in wide-band continuum measurements are discussed, emphasis is placed upon the recently discovered polarization effects in the emission lines and upon a discussion of models. Scattering in the photosphere of a star, even one rigidly rotating near breakup velocity, does not explain the observations. Better fits to the observations are obtained by scattering from electrons in a flattened gaseous disk extending some 10 stellar radii from the star with electron temperatures Te ≅ 10 000 K and electron densities Ne ≅ 1012 cm−3. In some stars the emission flux in Hα and Hβ appears to be partly polarized.
Intrinsic Linear Polarization of Be Stars as a Function of v sin i
Authors: Poeckert R. , Marlborough J. M.
Published: July 2016

The polarization of 48 Be stars has been measured in two bands near Hα with the aim of determining the relation between intrinsic polarization and v sin i. A technique developed by Poeckert (1975) is used to remove the effect of interstellar polarization. It is found that intrinsic polarization depends strongly on v sin i; stars with low v sin i having little or no polarization. We have calculated the i dependence of linear polarization for a disk model envelope and find that the polarization is proportional to τe sin2i when the disk is optically thin (τe is a characteristic electron scattering optical depth). A comparison of the observed relation between intrinsic polarization and v sin i, and that predicted for the disk model is illustrated. We find that an envelope with an electron density of ≤5 × 1011 cm−3 can account for the degree of intrinsic polarization observed in all the program stars. The fact that stars of low v sin i have little intrinsic polarization is evidence for the assumption that these stars are seen pole-on and that the envelopes around these stars are axi-symmetric. No apparent difference between pole-on stars and extreme Be stars was obtained.
On the Possible Role of Magnetic Fields in the Dynamics of the Be Phenomenon
Authors: Limber D. Nelson
Published: July 2016

A problem that has intrigued me for some years is that of the dynamics of the Be phenomenon. For, although the Be phenomenon has been extensively studied for decades, the problems associated with the dynamics of the circumstellar envelopes about Be stars - the problems associated with their formation, with their maintenance, and with their dissolution - have, until very recently, received little more than qualitative consideration.
Common Envelope Binaries
Authors: Paczynski B.
Published: July 2016

When a contact binary expands so much that the stellar surface moves beyond the outer Lagrangian point, a common envelope binary is formed. The suggestion is made that while the two dense stellar nuclei spiral towards each other, the envelope expands and is eventually lost. Most of the angular momentum is lost with the envelope, and therefore the final orbital period may be orders of magnitude shorter than the initial period. V471 Tau could have formed from a binary with a ten year orbital period. Most probably, cataclysmic variables are products of the evolution of systems like V471 Tau. Observational discovery of a short period binary being a nucleus of a planetary nebula would provide very important support for the evolutionary scenario presented in this paper.
Observations of Dwarf Novae
Authors: Warner B.
Published: July 2016

Spectroscopic and photometric observations relevant to the structure of classical novae, recurrent novae and dwarf novae are collected together. Details are given of optical, infrared, satellite ultraviolet, X-ray and radio observations. Most of these can be understood in terms of the hot spot model of cataclysmic variable stars. Estimates are made of luminosities, temperatures and rates of mass transfer. Observations made during eruptions of dwarf novae imply large changes taking place in the accretion disc.