bluuebunny/crossref_metadata_2025 huggingface dataset:
The Origin of Comets
Authors: Whipple F. L.
Published: July 2016

The evolution of the solar system is surveyed, it being presumed that the Sun, Jupiter, and Saturn formed rather quickly and essentially with the composition of the original collapsing cloud of dust and gas. Just as the refractory material of the cloud is considered to have formed into planetesimals, from which the terrestrial planets collected, so is the icy material supposed to have produced comets, or cometesimals, from which Uranus and Neptune (and to some extent Saturn and Jupiter) were built up. The presence of a residual belt of comets beyond the orbit of Neptune is discussed, analysis of possible perturbative effects on P/Halley indicating that the total mass of such a belt at 50 AU from the Sun could not now exceed the mass of the Earth.
On the Rate of Ejection of Dust by Long-Period Comets
Authors: Lebedinets V. N.
Published: July 2016

A model of the interplanetary dust medium that includes two subsystems, a spherical component and a flat one, has been proposed by the author as a result of analysis of radar meteor orbits. The disintegration of short-period comets is the main source of the flat dust cloud, while the disintegration of long-period comets is the main source of the spherical cloud. Assuming that dust particles fall into the Sun due to the Poynting-Robertson effect, one can estimate the intensity of ejection of dust from long-period comets necessary for the maintenance of the observed density of interplanetary dust. It has been found that the long-period comets should eject between 7 × 1014 and 2 × 1015 g of meteoric dust per year.
Deformation of a Meteor Stream Caused by an Approach to Jupiter
Authors: Levin B. Yu. , Simonenko A. N. , Sherbaum L. M.
Published: July 2016

The increase in the width of a meteor stream with time is usually regarded as due to differences in the secular variations of the slightly different orbits of individual meteoroids. However, the ordinary differential planetary perturbations acting on different parts of an elliptical ring of meteoroids have a more important effect. Model calculations are presented for a filament-like stream that makes close approaches to Jupiter. They confirm the major importance of deformations of the stream by direct planetary perturbations that act even on a filament-like stream of zero thickness. The disturbed part of the stream takes the form of a bend, dispersing along the initial orbit and producing a significant decrease in the spatial density of the meteoric particles.
Optical Observations of the Crab Nebula
Authors: Trimble Virginia
Published: July 2016

The continuum radiation from the Crab Nebula has a great deal of structure, the majority of which is strongly polarized. Wisps in the vicinity of the pulsar at the centre of the nebula move noticeably in a few months. The appearance of the nebula changes markedly when photographed in different emission lines, as a result of the variations of physical conditions from place to place within the nebula.
X-Ray Observations of the Crab Nebula
Authors: Kellogg Edwin M.
Published: July 2016

This paper is a review of the X-ray observations made on the Crab Nebula They include angular size, location, energy spectrum as high as 560 keV, upper limits on time variability and line emission, interstellar absorption and polarization. Some data on the X-ray spectrum of the pulsar NP0532 are included, but for details on the X-ray pulsar, see the paper by Rappaport (1971). The X-ray luminosity versus radius of the Crab, compared with that of other known X-ray emitting supernova remnants is also discussed.
Recent Results on the Search for 1011 eV Gamma Rays from the Crab Nebula
Authors: Fazio G. G. , Helmken H. F. , Rieke G. H. , Weekes T. C.
Published: July 2016

The detection of Čerenkov light emitted by cosmic-ray air showers was used to search for cosmic gamma rays from the Crab Nebula. By use of the 10-m optical reflector at Mt. Hopkins, Arizona, the Crab Nebula was observed during the winter of 1969–1970 for approximately 112 hours, which was a significant increase in exposure time over previous experiments. Above a gamma-ray energy of 2.2 × 1011 eV, no significant flux was detected, resulting in an upper limit to the flux of 8.1 × 10-11 photon/cm2 sec. In the synchrotron-Compton-scattering model of gamma-ray production in the Crab Nebula, this limit on the flux indicates the average magnetic field in the nebula must be greater than 3 × 10-4 G.
Small-Scale Solar Magnetic Fields
Authors: Stenflo J. O.
Published: July 2016

The observed properties of small-scale solar magnetic fields are reviewed. Most of the magnetic flux in the photosphere is in the form of strong fields of about 100–200mT(1–2 kG), which have remarkably similar properties regardless of whether they occur in active or quiet regions. These fields are associated with strong atmospheric heating. Flux concentrations decay at a rate of about 107Wb s-1, independent of the amount of flux in the decaying structure. The decay occurs by smaller flux fragments breaking loose from the larger ones, i.e. a transfer of magnetic flux from smaller to larger Fourier wave numbers, into the wave-number regime where ohmic diffusion becomes significant. This takes place in a time-scale much shorter than the length of the solar cycle.

The field amplification occurs mainly below the solar surface, since very little magnetic flux appears in diffuse form in the photosphere, and the life-time of the smallest flux elements is very short. The observations further suggest that most of the magnetic flux in quiet regions is supplied directly from below the solar surface rather than being the result of turbulent diffusion of active-region magnetic fields.
Drift of Sunspots in Latitude
Authors: Tuominen Jaakko
Published: July 2016

I am going to show two slides which should clearly prove that sunspots are drifting very regularly in the north–south direction on the solar surface.
Long Term Evolution of Solar Sector Structure
Authors: Svalgaard Leif , Wilcox John M.
Published: July 2016

The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles, with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given.
The Pattern of Convection in the Sun
Authors: Weiss N. O.
Published: July 2016

The structure of solar magnetic fields is dominated by the effects of convection, which should be incorporated in any model of the solar cycle. Although mixing length theory is adequate for calculating the structure of main sequence stars, a better description of convection is needed for any detailed dynamo model. Recent work on nonlinear convection at low Prandtl numbers is reviewed. There has been some progress towards a theory of compressible convection, though there is still no firm theoretical evidence for cells with scales less than the depth of the converting layer. However, it remains likely that the pattern of solar convection is dominated by granules, supergranules and giant cells. The effects of rotation on these cells are briefly considered.
Mean-Field Magnetohydrodynamics as a Basis of Solar Dynamo Theory
Authors: Rädler K.-H.
Published: July 2016

One of the most striking features of both the magnetic field and the motions observed at the Sun is their highly irregular or random character which indicates the presence of rather complicated magnetohydrodynamic processes. Of great importance in this context is a comprehension of the behaviour of the large scale components of the magnetic field; large scales are understood here as length scales in the order of the solar radius and time scales of a few years. Since there is a strong relationship between these components and the solar 22-years cycle, an insight into the mechanism controlling these components also provides for an insight into the mechanism of the cycle. The large scale components of the magnetic field are determined not only by their interaction with the large scale components of motion. On the contrary, a very important part is played also by an interaction between the large and the small scale components of magnetic field and motion so that a very complicated situation has to be considered.
Chromospheric Variations in Main Sequence Stars
Authors: Wilson O. C.
Published: July 2016

The work described here is still in progress; hence this paper will be a brief sampling of the results to date.
The Internal Structure of the Sun and Solar Type Stars
Authors: Roxburgh IAN W.
Published: July 2016

Our understanding of the internal structure of the Sun and solar type stars has been undermined by recent observations. In this paper we consider some of the puzzles and possible resolutions; the solar neutrino problem, lithium and beryllium abundance, rotation and calcium emission, variation of the solar constant, solar oscillations and the solar convective zone. The picture that emerges is one of confusion, and so it should be since we have no idea of what is going on inside the Sun anda fortioriof what is going on inside other stars.
Chromospheric Activity in F- and G-Stars
Authors: Dravins Dainis
Published: July 2016

Chromospheric activity, as seen by the presence of a central K2 emission in the Ca II K λ 393.4 nm line, is studied in F- and G-stars of all luminosity classes. K2 equivalent widths have been measured and corresponding absolute K2 fluxes (power per unit area at the stellar surface) calculated. Large K2 equivalent widths and thus easily detectable chromospheres occur only for stars later than about F8 but the absolute level of K2 flux does not significantly change between F0 and K0; there is no break in chromospheric activity between F- and G-stars. The apparent break, cited in the past (e.g. Wilson, 1973) is illusory and due to the observational threshold being different for different spectral classes.
Double-Peaked Flare Events on red Dwarf Stars and Solar ‘Sympathetic’ Flares
Authors: Rodonò M.
Published: July 2016

About 50% of the flare events observed on red dwarfs are at least double-peaked. As the majority of flare stars are members of double or multiple systems, the possibility that time-overlapping flares originate quasi-simultaneously on the individual components is discussed.

Assuming a poissonian occurrence of flares in both components, the expected probability of observing double-peaked flares is lower than 1% for the most active binary systems.

However, from photometric observations of the double flare star EQ Peg (BD +19°5116 AB) carried out by the author with an area scanner (the components' angular separation is 3.7″) about 20% of the observed flares have been found to be double-peaked flares resulting from separate flares, one in each component. A direct flare triggering of the following flare by the preceding one can be ruled out since the light travel-time between the two components is 3.5 h, while the observed time delay between the flare peaks is about 10 min. Moreover, the proximity effect does not seem to play an important triggering role.

It is concluded that, although the analogy with solar ‘sympathetic’ flares is not always applicable, it is the most promising framework within which the majority of double-peaked flare events on red dwarfs must be interpreted.
Abundance Effects for the A0–G2 Stars in the Geneva System
Authors: Hauck B.
Published: July 2016

The abundance effects on the tri-dimensional representation for the A0-G2 stars in the Geneva system are reviewed. B2–V1 anddare not affected by the Am characteristic, but B2–V1 is too blue (blocking effect on V1) anddsmaller for the Ap stars. For B2–V1 ≥ 0.230, we have a residual effect Δ(B2–V1) = 1.20 (Δm∗2+ 0.060). d is also affected and the residual effect is Δd= −0.4 Δm2for Δm2≥ −0.060 and Δd= −1.1 Δ(B2–V1) −0.024 for Δm2< −0.060.

The abundance effects on the relations between B2–V1 and the parameters of temperature in other systems are studied.
Observed Relations Between Physical Properties and MK Classification as Functions of Metal Abundance for F5-K4 Stars
Authors: Grenon M.
Published: July 2016

The Geneva photometric system has been calibrated in terms of [M/H], θeff, Mv in the spectral range F5 to K4. As the spectral type is a datum generally available, we derive empirical relations showing the coupling of θeff and [M/H] at given spectral type and luminosity class. Similar relations are offered for the absolute magnitudes and provide a more accurate means for deriving spectroscopic parallaxes. Systematic effects on the estimation of the luminosity class are also shown.
On the Derivation of Abundances by Means of Features in the Sequences of the old Open Star Clusters
Authors: Maeder A.
Published: July 2016

Stellar evolution near the main-sequence is still subject to many discussions. In addition to the case of the cluster M 67 (Racine, 1971), quite systematic differences have been encountered during the comparison of theoretical isochrones and observed sequences in the colour-magnitude diagram of the old open star clusters (Maeder, 1974). In the case of M 67 and NGC 188, many attempts to discuss the characteristics of their sequences (such as the gap corresponding to the hydrogen-exhaustion phase) in terms of chemical composition have been made (e.g. Aizenman et al., 1969; Demarque and Schlesinger, 1969; Demarque and Heasley, 1971; Torres-Peimbert, 1971; Hejlesen et al., 1972; Caloi et al., 1974); some of these works have suggested to explain the gap parameters by a high metal content. Attemps to explain the differences between models and observations by means of simplified models with overshooting from convective cores have also been made (Maeder, 1973; Prather and Demarque, 1974). Let us also note that it has been shown that it is unlikely that the anomalies found are due to systematic effects, like the interstellar reddening, binarity, rotation or effects in calibrations or composition of the initial homogeneous models.
Mass Estimation of Twelve K Dwarfs
Authors: Perrin M.-N.
Published: July 2016

Detailed analyses giving the chemical composition have been carried out for twelve K dwarfs. Iron over hydrogen values have been found. Estimates of the masses of these stars are given.
Chemical Evolution of the Galactic Disk and the Radial Metallicity Gradient
Authors: Mayor M.
Published: July 2016

An analysis of the kinematical and photometric properties of about 600dF stars and 600 gG-gK stars permits the estimation of the radial chemical gradient in the Galaxy. The mean value in the solar neighbourhood obtained for all of these stars is:

The values of [Fe/H] used for this estimation are deduced for the dF stars using uvby β photometric measurements and for the gG-gK stars from a list published by Hansen and Kjaergaard. An estimate of the chemical gradient using UBV photometry of dG stars in the solar neighbourhood gives a similar value. For all the samples studied (dF, dG or giants) the order of magnitude for the gradient is the same. However, for the youngest stars in these samples the metallicity gradient could be larger:

Such a value may be affected by dynamical perturbations of the galactic disk.

The values published by Hansen and Kjaergaard for the sodium concentration in giant star atmospheres also indicate a radial galactic gradient of the same order.

If only the dF stars which are sufficiently evolved to allow an age estimate are considered, then a very distinct correlation is found between age and metallicity:

An important fraction of the heavy elements actually present in the solar neighbourhood seems to have synthetized during the life of the galactic disk.

The two derivatives and are not independent, but are connected by the chemical evolution of the galactic disk. Some elementary deductions show the coherency of these two estimates.

The intrinsic dispersion of metallicities, at a given age and birthplace, is somewhat lower than the admitted values.

It has not been possible to find any significant variation with age of this quantity from the present observational material. The simultaneous variation of σ2w and [Fe/H] as function of age is evidence for a z stratification in the mean abundance of the heavy elements. The ratio between the mean metallicity in the plane and at z = 500 pc is estimated to be about a factor of two.

Finally it is shown that the interpretation of the kinematical diagrams for different groups of given metallicity is ambiguous. A relation as e vs [Fe/H] depends not only on the chemical and kinematical history of the Galaxy but is also strongly dependent on the observational errors of [Fe/H] and on criteria used to define the sample.

A paper containing the above results has been submitted for publication in Astronomy and Astrophysics.
Curve-of-Growth Analysis of a Red Giant in M 67
Authors: Griffin R.
Published: July 2016

A coudé spectrogram of a red giant (IV-202) in M 67 has been analyzed with respect to Arcturus by the differential curve-of-growth method. The overall metal abundance is found to be approximately twice that in Arcturus, i.e. half the solar value. The error limits exclude the interpretation that IV-202 is ‘super-metal-rich’. According to other observational evidence, IV-202 is quite typical of the red giants in M 67.
Masers as chemical probes of star-forming regions
Authors: Menten Karl M.
Published: July 2016

Maser emission from the OH, H2O, and CH3OH molecules is found toward hundreds of molecular cloud cores with recent and on-going star formation. The often very high intensities of the observed emission imply substantial abundances of the maser molecules, which are difficult or impossible to explain with ion-molecule gas phase chemistry. We summarize relevant observations which show that OH and Class II CH3OH masers form in the envelopes of ultracompact HII regions in which the high abundances of these molecules are produced by evaporation of methanol and water from icy dust grain mantles. In contrast, H2O masers form in outflows from protostellar objects, where high H2O abundances are produced by endothermic neutral-neutral reactions in hot postshock gas. Finally, we briefly discuss Class I CH3OH masers, which also arise in interstellar outflows.
Evidence for collapse in dark clouds
Authors: Zhou S.
Published: July 2016

Bart Bok speculated back in the 1940's that dark cloud cores (i.e. Bok globules) are sites of star formation. The means for probing the dark cloud cores, molecules, were not discovered until much later. Today, we can finally say Bart Bok was right! Evidence for collapse in dark cloud cores will be discussed in general, along with specific examples of collapse candidates. We also describe methods to search for new candidates and the complications in identifying the infall motion.
Inelastic collisions of interstellar molecules
Authors: Ter Meulen J.J.
Published: July 2016

The rotational energy transfer of NH3, OH and D2CO in inelastic collisions with He and H2 is studied in a crossed molecular beam experiment. The molecules are prepared in a single initial state by rotational cooling in an adiabatic expansion followed by electrostatic state selection. Relative state-to-state cross sections are determined by measuring the collision induced redistribution of the population of the initial state by using state selective laser detection techniques. The results for NH3 and OH are compared to theoretical values obtained from quantum calculations. Except for NH3 — He where theory predicts a parity selection rule for transitions to the 33 and 43 states, which is not observed in the experiment, good agreement between experiment and theory is obtained.
Infrared and optical spectroscopy of astrophysical molecules
Authors: Bernath Peter F.
Published: July 2016

The recent laboratory spectroscopy of a number of astrophysically important molecules are discussed. Examples include small molecules such as CrH, HF, FeF, SiS, CH4, H20, SiO and TiO as well as large molecules such as COO and polycyclic aromatic hydrocarbons (PAHs). Many of these examples illustrate the utility of infrared and far infrared emission spectroscopy. The close coupling of laboratory spectroscopy and molecular astronomy has led to advances in both areas.
Infrared spectroscopy with the Infrared Space Observatory
Authors: Genzel R. , Drapatz S. , Lutz D. , Wright C. , De Graauw Th.
Published: July 2016

The Infrared Space Observatory (ISO) is opening the 2.5 to 200 μm band for detailed infrared spectroscopy. Concentrating on ionic and molecular emission lines observed with the Short Wavelength Spectrometer (SWS) we discuss ISO's first results on Galactic and extragalactic sources.
Millimeter-wave observations of diffuse clouds
Authors: Lucas R. , Liszt H. S.
Published: July 2016

Using the IRAM instruments (interferometer on Plateau de Bure and 30-m telescope on Pico Veleta) we have made numerous observations of molecular absorption lines in front of extragalactic millimeter wavelength radio sources. Observations of HCO+, CO and OH show that the lines of sight studied in this way sample the outer edges of molecular clouds or the diffuse clouds with highest column densities. Collisional excitation of the rotational levels is not significant in this density range for most molecular species, and accurate column densities may be derived by assuming radiative equilibrium with the cosmic microwave background. Using this technique we have measured column densities of CO, HCO+, H2CO, CN, HCN, HNC, CS, SO, H2S, C2H, and C3H2 in several lines of sight, intersecting about 20 individual clouds with CO column densities in the range 2 1014 to ∼ 1016 cm−2. These results confirm that complex molecules achieve dark-cloud abundances at low extinctions, either by formation in the gas phase or on grains.
Water megamasers as a probe of a circumnuclear accretion disk in an active galaxy
Authors: Neufeld David A.
Published: July 2016

In the past three years, observations of extragalactic water masers have demonstrated the extraordinary power of spectral line radio interferometry to probe the inner regions of active galaxies on subparsec scales. In the case of the active galaxy NGC 4258, the observations of Miyoshi et al. (1995) have established the presence of a thin, slightly warped, and Keplerian circumnuclear accretion disk that orbits a central object of mass 3.6 × 107M⊙. In addition to their immense value as kinematic probes, extragalactic water masers also provide valuable constraints upon the physical and chemical conditions in the masing circumnuclear gas, yielding an estimate of the mass accretion rate through the circumnuclear disk of NGC 4258. These recent observational and theoretical developments are reviewed here.
Chemistry in the LMC and SMC
Authors: Johansson L.E.B.
Published: July 2016

Molecular abundances derived in a sample of CO complexes in the Magellanic Clouds are discussed. With a possible exception of HCO+, the chemical compositions observed in this sample show a striking uniformity. The data indicate that the molecular concentrations are down by a factor of 5 in the SMC, relative those observed in a cloud associated with the H II region N159 in the LMC. A similar difference seems to exist within the LMC, between the 30 Doradus region and the N159 area. An estimate of the electron abundance in the N159 cloud is presented, based on a recent detection of DCO+.
Infrared Spectra of T Tau Stars and Related Objects
Authors: Shanin G. I. , Shevchenko V. S. , Shcherbakov A. G.
Published: July 2016

Four T Tau stars and related objects (RY Tau, T Tau, AB Aur and V1057 Cyg) have been included in our spectroscopic programme since 1973. The present paper is concerned with the spectroscopic observations made at the Crimea with the single-stage image tube S1. Tentative atomic line identifications are given for programme stars. CaII and OI emission line equivalent widths and profiles are presented for RY Tau, T Tau and AB Aur. The λ10830 Å line of neutral helium has shown P Cyg-type features for T Tau and V 1057 Cyg.
Photographic Photometry of V 1057 Cygni
Authors: Mandel O. E.
Published: July 2016

The photographic magnitude of V 1057 Cyg is estimated on all plates available at the Odessa plate depositary. The light variation is similar to that of FU Orionis.
Autocorrelative Analysis of the Brightness of Irregular and Semi-Regular Variable Stars
Authors: Lukatskaya F.I.
Published: July 2016

This paper gives an introduction to the use of autocorrelative analyses in the case of irregular and semi-regular brightness variations.
A Photoelectric Investigation of the Double Cepheid CE Cas
Authors: Franz Otto G. , Franz Otto G.
Published: July 2016

A photoelectric area scanner (Franz, 1970) was used to carry out photometry of the separate components of the double Cepheid CE Cas, a binary of 2.5″ separation located in NGC 7790. CE Cas A was found to undergo rapid fluctuations as well as a slow change of its brightness near minimum phase, while its brightness at maximum has remained the same over more than 10 yr. The absence of the effect from the observations of CE Cas B and evidence for its presence in earlier observations by Sandage and Tammann (1969) serve to establish the reality of this phenomenon. Manifestation of this effect during early phases of this investigation had led to the erroneous conclusion that CE Cas A had undergone a significant change of period in recent years (Franz, 1972).
On the Structure of the Cepheid Instability Strip
Authors: Yakimova N. N. , Nikolov N. S. , Ivanov G. R.
Published: July 2016

Using rich photometric material on the Cepheids in the Galaxy and the Large and Small Magellanic Clouds, the structure of the instability strip in the HR diagram is investigated. The method of the δ-δ diagrams is used, δ being the difference of certain Cepheid characteristics from the means for a given period. The Cepheids in the three galaxies, studied separately, show the same relationship: the light amplitude increases toward the low temperature limit of the instability strip and is also related with the temperature at maximum in the sense that Cepheids with a given period and fixed mean temperature have a greater light amplitude for a higher temperature at maximum. Our results do not coincide with those by Sandage and Tammann, probably because they have studied the Cepheids in the different star systems as one single complex.
Radial Pulsations of δ Scuti Stars: Theory in Comparison with Observations
Authors: Pamjatnykh A. A.
Published: July 2016

In this paper the pulsations of δ Sct star models are compared with observational data. The locations of the blue edges of the instability strips were computed as a function of helium abundance. Linear non-adiabatic pulsations were computed following Dziembowski's programme.
The Wolf-Rayet Stars
Authors: Rublev Sergej V.
Published: July 2016

This review discusses the spectral classification, the absolute magnitude, the position in stellar systems, the physical properties and the evolution of WR stars.
Spectroscopic Investigations of Luminous Emission-Line Objects
Authors: Cassatella Angelo , Nesci Roberto , Viotti Roberto
Published: July 2016

Emission lines are frequently observed in the spectra of the high luminosity stars, indicating the presence of extended atmospheric envelopes. We are investigating the physical characteristics (differential expansion velocity, density, extension, mass loss) and the origin of these envelopes in relation to the high luminosity of the parent star, and its evolutionary stage. Some results are presented concerning Eta Car, S Dor, HD 34664, P Cyg, AG and HR Car, and two WR stars.
Novae
Authors: Arhipova V. P. , Mustel E. R.
Published: July 2016

This paper is a review of some of the most important problems on novae. Special attention is paid to the interpretation of recent observational data on novae, structure of the principal envelopes, infrared emission from novae and especially to the problems of magnetic fields in novae.
VW Hydri, a U Geminorum-Type Star with Periodic Variations During Outbursts
Authors: Vogt N.
Published: July 2016

Extensive photoelectric observations of VW Hyi have been carried out during minimum light and eruptions. In the minimum stage VW Hyi shows a periodically repeating hump (similar to that of U Gem) from which an orbital period of has been derived. No eclipses are present. The two types of eruptions known previously for VW Hyi correspond to different physical processes: the short eruptions (lasting ∼4d) resemble again those of U Gem; the minimum hump disappears during bright phases. During the long eruptions (lasting ∼ 17d) a light curve with pronounced peaks has been observed with periodicities of . Significant colour variations with this period are also present. During one long maximum, the repeating feature separated into two peaks. A first attempt has been made to interpret qualitatively the observed facts by an interaction between gas streams from the inner Lagrangian point and ejected matter from the white dwarf component.

The detailed results were published in Astronomy and Astrophysics36 (1974), 369.
Symbiotic Stars
Authors: Boyarchuk A.A.
Published: July 2016

There are some arguments that the symbiotic stars are binary, where one component is a red giant and the other component is a small hot star which is exciting a nebula. The symbiotic stars belong to the old disc population. Probably, symbiotic stars are just such an evolutionary stage for double stars as planetary nebulae for single stars.
Combined Optical and X-Ray Observations of Variable Stars
Authors: Bowyer C. Stuart
Published: July 2016

Two problems of X-ray astronomy are discussed: (1) Optical identifications of X-ray sources, and (2) Optical and X-ray observations of U Geminorum.
A Search for Super-Rapid Variability of X-Ray Sources and Other Peculiar Objects
Authors: Evseyev O. A. , Mansurov V. N. , Pavlova V. S. , Pustil'Nik L. A. , Shvartsman V. F. , Tsarevsky G. S. , Yakushev A. K.
Published: July 2016

At the Special Astrophysical Observatory of the U.S.S.R., an experiment to detect super-rapid variability of brightness and polarization in a number of peculiar objects is being carried out. This includes the optical stars identified with X-ray sources, specifically Cyg X-1, Her X-1 and Sco X-1, as well as the so-called DC-dwarfs and some BL Lac-type objects (that is optical objects possessing a continuous spectrum). The time range of measurements varies for different objects; however as a rule, it lies within 10−5 to 10 s.

At the time of our observations no rapid and super-rapid fluctuations of radiation exceeding in amplitude 10% have been detected.
Observations of Circular Polarization in V 1357 CYG = CYG X-1
Authors: Shulov O. S.
Published: July 2016

Our observations of the X-ray binary V 1357 Cyg suggest that a small circular polarization increasing towards the longer wavelength exists in the light of the star.
Discovery of Light Variability in the White Dwarf G 29–38
Authors: Shulov O.S.
Published: July 2016

Rapid variations with small amplitudes were detected in the light of the white dwarf EG 159 = G 29–38, a 13th magnitude star.
RR Lyrae- and W Virginis-Type Stars
Authors: Kukarkin B. V.
Published: July 2016

RR Lyrae stars: Normalized period-frequency diagrams are discussed, see Table I and Figure 1. Two ‘standard’ period-frequency relations were derived: one for − 1.17 and the other for − 1.72. The peculiarity of the diagrams for some clusters is pointed out. Various metallicity criteria are discussed together with other features of globular clusters. Some unexplained anomalies are found.

W Virginis stars: Properties of these stars are discussed. They too seem not to form a homogeneous group. The lack of accurate observations is stressed.
General Properties of the Two Groups of Globular Clusters and Their Variable Stars
Authors: Mironov A. V. , Samus' N. N.
Published: July 2016

The dependences of the numbers of variable stars in globular clusters on the chemical composition are studied. For given metallicity the numbers of RR Lyrae stars reduced to some definite total number of stars in the cluster are different for the two groups of globular clusters introduced by Mironov.
The Study of Light Curves with the Aid of Smoothing Spline-Functions
Authors: Pop V. , Pop P.
Published: July 2016

By means of smoothing spline functions an attempt is made to approximate cepheid-type light curves. As an example the light curve of XZ Cyg is used.
Optical Variability of the Nuclei of Seyfert Galaxies
Authors: Lyuty V. M. , Pronik V. I.
Published: July 2016

The continuum variability (UBV observations), the variations in the emission lines, and the properties of the central source in the nuclei of Seyfert galaxies are discussed. There is the quasi-periodicity in the light variations of the nuclei. The emission lines show the variations both in the intensity and the profiles. All data lead to the conclusion, that both continuum and emission-lines intensity variations are due to the variability of the central nonthermal source.
Stellar Photometric Observations at Hα Through a Narrow-Band Interference Filter
Authors: Butler Hugh E.
Published: July 2016

The paper describes the results of stellar photoelectric observations made with a small telescope and a 3 1/2 Å wide filter centred at Hα.

The method proved to be a sensitive one for detecting change in the spectrum but did not allow differentiation between changes in the Hα profile and wavelength changes due only to the Doppler effect. It was possible, however, to recognise and qualitatively to eliminate the Doppler changes due to the Earth's Annual Motion.

Of ten Be stars examined three, although in strong emission, showed little change over the periods of observation, the longest of which was 9 months. The other seven showed large and random changes.

Warnings are given about the difficulty of tuning such a filter exactly to Hα and the need to monitor accurately the filter for long term changes in passband and throughput.
Observations Récentes de HD 200120
Authors: Herman R. , Hubert H.
Published: July 2016

HD 20012 (f1 Cyg) fait partie des étoiles des premiers types B. Nous l'avons classée O9 V?, Nina Morguleff l'a classée B1 IV et Janet Lesh B1, 5 V). Elle fait partie de notre programme d'observation qui concerne les étoiles Be de magnitude ≤7 et de déclinaison ≥ −15°. Parmi les étoiles les plus chaudes de ce programme, on peut signaler au moins deux catégories.
A Survey of Mass Loss from Be and Shell Stars Using Ultraviolet Data from Copernicus
Authors: Marlborough J. M. , Snow Theodore P.
Published: July 2016

Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of twelve objects classified as Be or shell stars, and an additional 19 dwarfs of spectral classes B0-B4. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si iv doublet at λ 1400 Å, indicating the presence of outflowing material with maximum velocities of nearly 1000 km s−1. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5. Later than B0.5, the only survey objects showing this phenomenon are Be stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the UV flux from B1-B3 dwarfs is sufficient to drive high-velocity stellar winds only if rotation reduces the effective gravity near the equator. The role of mass-loss in producing the Be star phenomenon and the effects of rotation on mass loss are discussed.
Spectroscopic Observations of the Be Stars η Cen, γ Cas and φ Per
Authors: Burton W. M. , Evans R. G.
Published: July 2016

The main part of this paper is concerned with observations obtained using the Princeton ultraviolet telescope-spectrometer on the Copernicus satellite through the Princeton guest investigator programme. These observations provided high resolution ultraviolet spectra of the bright southern shell star η Cen, which are now being analysed in detail. A short description of the new η Cen spectra and a progress report on the data analysis are presented below. In the second part of the paper we describe visible-region spectra of the northern Be stars γ Cas and φ Per obtained with a cross-dispersed echelle spectrograph on the 36-inch Yapp telescope at the Royal Greenwich Observatory.
Line Formation in Expanding Atmospheres: (Review Paper)
Authors: Hummer D. G.
Published: July 2016

The current state of understanding of line formation processes in expanding atmospheres is reviewed, and the successes and limitations of current computational techniques are summarized. Some results for differential rotation are also given, although very little work has been done in this area. Special attention is given to the severe difficulties that are encountered in inferring the structure of rapidly expanding or rotating atmospheres from observed line profiles because of the failure under these conditions of the Eddington-Barbier relation in integrated light; the value in this respect of continuum and interferometric observations is emphasized.
Toward a Model for the Be Binary System φ Per
Authors: Hendry E. M.
Published: July 2016

Arguments are presented against the adoption of an early B-red giant combination for the Φ Persei system. Velocity curves of the primary and secondary components based on the measures of the He I lines on nearly two hundred plates are shown and discussed insofar as orbital parameters and system membership are concerned. Evidence from the He I lines, the emission edges, shell absorptions, and underlying wide absorptions of the hydrogen lines indicate that the system is made up of a B1 primary and a B3 secondary, both of which are emission-line stars.
Massive Binaries – Early Evolutionary Stages
Authors: Hutchings J. B.
Published: July 2016

Fundamental data on OB supergiants and binary systems are presented. Mass loss is reviewed, and its correlation with close binary membership. The evolution of massive binaries is discussed and several classes of observed binaries compared with the theoretical picture. Individual systems of significance are pointed out and the chief problems in massive binary research are indicated.
Binary X-Ray Stars and Supernovae of Type I
Authors: Gursky H.
Published: July 2016

Most of the strong galactic X-ray sources must be low mass, close binary systems, such as Her X-1 and Sco X-1. Two evolutionary scenarios are discussed, both involving type I supernovae that occur when mass-accreting white dwarfs are driven over their mass limit. In one, accepting the correctness of the idea that a neutron star or black hole is the seat of the X-ray emission, the SN occurs before the system is an X-ray source. Another possibility is that the white dwarf is the X-ray source, just prior to its collapse and the ensuing SN.
The Post-Supernova Stage of Massive Close Binaries: The Possibility of a Tidal Instability
Authors: De Grève J. P. , De Loore C. , Sutantyo W.
Published: July 2016

It has been proposed that tidal interaction is the mechanism which restored the circular orbits of X-ray binaries after the supernova explosions which produced the compact components in those systems. (Lea and Margon, 1973; Sutantyo, 1974). This implies that the primaries must possess large viscosity in order to provide large energy dissipation rates required in this process. At the end of this process the system reaches a stable synchronous and circular orbit. If this hypothesis is true, there will be further consequence of the strong tidal interaction during the later stages of evolution of the system. The gradually changing structure of the primary during the post main-sequence stages will continuously disturb the stability of the orbit. There will be transfer of angular momentum from the orbital motion into the rotation or vice versa through the tidal interaction. At a certain stage, the radius of the primary exceeds a critical radius, the orbit becomes unstable and synchronism becomes impossible. The compact component will be spiralling down onto and into the primary as proposed by Sparks and Stecher (1974).
Tidal Interactions in Compact Binary Systems
Authors: Wheeler J. C. , Lecar M.
Published: July 2016

An analytic model has been constructed for the change of orbital elements because of tidal drag in a binary system where one of the components is compact (Lecar et al., 1976). The basic assumptions are (i) tides on the compact object are neglected (ii) only P2 deformations of the non-compact star are considered (iii) the lag angle is linearly proportional to the difference between the instantaneous orbital angular velocity and the spin angular velocity of the non-compact star (iv) the semi major axis a and eccentricity e do not change significantly in a single orbit. The results are exact solutions for a and ė as a function of e and the ratio of primary star to orbital angular velocity, Ω/ω.

Tidal instability in this model is manifest by the dynamical inability to attain or sustain synchronism. An analysis to second order in e and first order in (Ω/ω−1) shows that the criterion for instability is the same as in the work of Counselman (1973), namely ma2 > I where m is the reduced mass and I the moment of inertia of the primary star. This criterion is shown to apply to eccentric orbits and is thus more general than the criterion derived from the energetics of circular orbits. Stable systems may overshoot the condition of synchronism before settling into the final circular synchronous orbit.
The Eclipsing Binary White Dwarf BD + 16° 516
Authors: Nelson B. , Young A.
Published: July 2016

From spectroscopic and photoelectric data BD +16° 516 (V 471 Tau) is inferred to consist of a white dwarf of mass 0.72M⊙ and radius 0.012R⊙, with a detached K2V companion of mass 0.70R⊙ and radius 0.78R⊙; the separation of the two components is 3.02R⊙. The evolutionary history of the system is discussed.
Angular Momentum Loss and the Origin of Cataclysmic Binaries
Authors: Eggleton Peter P.
Published: July 2016

A two-stage mechanism is proposed whereby detached dwarf systems like V471 Tau may evolve into cataclysmic binaries. The two stages are (1) angular momentum loss from the secondary due to braking by a stellar wind linked with magnetic fields, and (2) angular momentum gain by the secondary from the orbital motion, due to tidal friction. This combination may be able to remove angular momentum from short-period binaries on a timescale of ~109 yr.
A Hydrodynamic Calculation of Gas Flow in a Cataclysmic Variable Star
Authors: Flannery Brian P.
Published: July 2016

A numerical simulation of mass transfer in a semi-detached binary star, modeled to resemble the dwarf nova Z Cam, indicates that the basic flow pattern rapidly (in less than an orbital period) assumes a stream-ring configuration. The effect producing the ring is radiative energy dissipation in a shock front which initially forms between gas in the stream from the Lagrangian point (L1) and gas farther upstream which, having already circuited the white dwarf, returns to collide with the L1 stream. The accumulating shocked gas settles into a circular orbit at a radius appropriate to its angular momentum. The ring is soon massive enough (and the Keplerian radius is large enough) to obstruct the stream from L1, so that the shock becomes concentrated at the intersection of stream and ring. This shock front can be identified with the hot spot observed in cataclysmic variable stars. Similar rapid ring formation can be expected in any binary in which the mass transfer is through L1 at low velocity, and the star receiving mass is small enough to avoid collision with the stream from L1.
Mass Flow in Close Binary Systems
Authors: Kondo Yoji , Mccluskey G. E.
Published: July 2016

The manner of mass flow in close binary systems is examined with a special view to the role of the so-called critical Roche (or Jacobian) lobe taking into consideration relevant physical conditions such as radiation pressure that may affect the restricted three-body problem treatment. The mass does not necessarily flow from component one to component two through the L1 point to form a gaseous ring surrounding the latter. These considerations are applied to X-ray binaries with early-type optical components, such as Cyg X-1 (HDE 226868) and 3U 1700-37 (HD 153919). In the two bright close binary systems β Lyr and UW CMa, which are believed to be undergoing dynamic mass transfer, recent Copernicus Princeton Telescope Spectrometer observations show that the gas giving rise to the prominent ultraviolet emission lines surrounds the entire binary system rather than merely component two. Implications of these observations are also discussed.
The Mass-Exchange Binary Sco X-1
Authors: Hutchings J. B.
Published: July 2016

Data on the binary character of Sco X-1 are presented.
Contact Binaries
Authors: Hazlehurst J.
Published: July 2016

Observational statements about close and contact binaries are compared with the theoretical consequences of assuming that contact binaries have a common convective envelope. It is concluded that such contact systems cannot be in thermal equilibrium, and that the inefficiency of convective heat transport in the common envelope must be allowed for. Even so, current theory seems to predict about equal numbers of contact and semidetached systems of short period, in conflict with the observations.
The Evolution of Contact Binaries
Authors: Van'T Veer F.
Published: July 2016

Asymmetric light curves and period changes of contact binaries can be explained by large-scale prominence activity. From the mass outflow accompanying this activity the mean lifetime of a contact binary is estimated as 5 × 107 yr. From the lifetimes of contact binaries and normal solar type dwarfs on the one hand and the proportion of the former among the latter in equal volumes of space on the other hand, it is concluded that (almost) all solar type dwarfs were contact binaries at the beginning of their main sequence life.
An Aspect of Star Fission
Authors: Leung K.-C. , Wilson R. E.
Published: July 2016

Parameters are derived for two massive, unevolved, contact binaries.
Les Orbites de Collision du Probleme Restreint
Authors: Nahon Fernand S.
Published: July 2016

The article studies collisions with the smaller primary, m2, in the planar restricted problem of three bodies. The formulation is in polar coordinates and the corresponding momenta. The results are based on the fact that the collisions correspond to a solution of a partial differential equation.