bluuebunny/crossref_metadata_2025 huggingface dataset:
Space Distribution of Carbon Stars in Our Galaxy
Authors: Noguchi K. , Qian Z. , Sun J. , Wang G. , Wang J. , Rao Y.
Published: July 2016

We are attempting to investigate the space distribution of carbon stars in our Galaxy by evaluating the distances of individual carbon stars. We estimate the distance by evaluating the total radiant energy of each star and assuming a value for the bolometric magnitude of carbon stars. Since the flux maxima of carbon stars are mostly in the near-infrared (NIR), NIR photometric data are most useful for evaluating the total energy. We have compiled NIR photometric data for 694 carbon stars at all galactic longitudes and have made new observations of 470 carbon stars in the galactic longitude region between 20° and 160°. We discuss the space distribution of 1164 galactic carbon stars.
A Photometric and Spectroscopic Survey of AGB Stars in M31
Authors: Brewer James P. , Richer Harvey B. , Crabtree Dennis R.
Published: July 2016

We have used a four-band photometric system capable of distinguishing C, S, and M stars to undertake a survey of AGB stars in M31. We discuss the results from this survey and from follow-up spectroscopy.
Quantitative Analysis of Carbon Isotope Ratios in N-, SC-, and J-type Carbon Stars
Authors: Ohnaka K. , Tsuji T.
Published: July 2016

We present the results of a quantitative analysis of 12C/13C ratios in 62 N-type, 15 SC-type, and 26 J-type carbon stars. The 12C/13C ratios are determined from lines of the CN Red System around 8000 Å, based on the iso-intensity method and line-blanketed model atmospheres. The resulting 12C/13C ratios in N- and SC-type carbon stars are consistent with a scenario in which M giants evolve through SC- to N-type carbon stars, as 12C produced during thermal pulses is added to the envelope.
12C/13C Ratios and Li Abundances in Low-Mass C Stars
Authors: Abia Carlos , Isern Jordi
Published: July 2016

High-resolution and high signal-to-noise-ratio spectroscopy is used to derive 12C/13C ratios from the Red System of the CN molecule at 8000 Å in several galactic low-mass C stars previously analyzed for lithium. It is found that Li-rich C stars usually have low isotopic ratios (< 15). This suggests that the Li and 13C enrichments in C stars might be produced by a similar mechanism. However, due to the large uncertainties in the abundance derivations for both Li and carbon isotope ratios, this result must be confirmed with further studies.
R CrB: Photometric Evidence Regarding the Nature of its Pulsation, and a Putative Connection between Pulsation and Deep Declines
Authors: Fernie J. D.
Published: July 2016

It is shown that the historical lightcurve of R CrB contains features that argue against the deep declines being caused by pulsation. As well, recent photoelectric photometry does not show the onset of deep declines occurring at a specific phase of pulsation. The photometry suggests that only one period is present at any time, although this period can drift and/or be replaced by another period. The evidence is strong that the pulsation is radial and obeys relationships found among classical Cepheids.
The Pulsations and Evolution of AGB Stars in the Large Magellanic Cloud
Authors: Gong Z. G. , Li Y.
Published: July 2016

The evolutionary status and pulsational characteristics of AGB stars in the LMC have been studied. It is found that only those stars with a small mixing-length ratio can fit the observed period-luminosity relation. Strong non-adiabatic effects were found in the outer envelope and must be taken into account in future work.
Lines of Circumstellar C2, CN, and CH+ in the Optical Spectra of Post-AGB Stars
Authors: Barker Eric J. , Lambert David L. , Van Dishoeck Ewine F.
Published: July 2016

Recent optical spectra of post-AGB stars show the presence of C2, CN, and CH+ originating in the circumstellar shell. We present here new, higher resolution spectra which provide constraints on the physical parameters and information on the line profiles. An empirical curve of growth for the C2 Phillips and CN Red system lines in the spectrum of HD 56126 yields b = 0.050+0.59−0.23 km s−1. CH+ (0,0) emission lines in the spectrum of the Red Rectangle have been resolved with a FWHM ≈ 8.5± 0.8 km s−1. The circumstellar CN lines of IRAS 08005-2356 are resolved into two separate components with a velocity separation of Δv = 5.7 ± 2.0 km s−1. The line profiles of CN of HD 235858 have not been resolved.
Chemical Composition and Evolution of Post-AGB Stars
Authors: Parthasarathy M.
Published: July 2016

Analysis of the chemical compositions of post-AGB stars reveals the following abundance patterns: (i) Post-AGB stars which are extremely underabundant in Fe and other refractory elements, but which have nearly normal abundances of C, N, O, S, and Zn. The depleted refractory elements are locked up in circumstellar dust grains. Formation of dust close to the star, and dust-gas separation and dust-driven mass loss driving out mostly the dust may explain the abundances of these stars. (ii) High-latitude hot post-AGB stars which show an underabundance of carbon, indicating that they left the AGB before the third dredge-up occurred. (iii) Post-AGB stars with overabundances of carbon and s-process elements, indicating that they have gone through the third dredge-up and carbon-star phase on the AGB. The overabundance of Li, Al, C and s-process elements in some post-AGB stars indicate that they have gone through the dredge-up and Hot Bottom Burning nucleosynthesis at the base of the convective envelope. The observed characteristics of post-AGB stars indicate an evolutionary sequence in the transition region from the tip of the AGB into the young planetary nebula stage.
Binarity among Barium Dwarfs and CH Subgiants: Will They Become Barium Giants?
Authors: North Pierre , Jorissen Alain , Mayor Michel
Published: July 2016

We report the results of monitoring the radial velocities of 31 confirmed Ba dwarfs and CH subgiants, showing that about 27 of them have a variable radial velocity. Therefore, mass transfer in a binary most probably explains their chemical anomalies, as for the Ba giants. The orbital parameters of the 14 systems having sufficient phase coverage are very similar to those of the Ba giants. Whether the CH subgiants and Ba dwarfs may become Ba giants is discussed briefly. Most of the marginal Ba dwarfs listed by Edvardsson et al. (1993) are single, so that their chemical peculiarity, if real, cannot be due to binary evolution.
The Chemical Composition and Orbital Parameters of Barium Stars
Authors: Začs Laimons
Published: July 2016

The observational relation between s-process abundance anomalies and orbital periods for barium stars is discussed and compared with mass-transfer simulations. Recent detailed abundance analyses of a large sample of single-lined long-period binaries provide evidence that all giants with white dwarf companions are likely to have abundance anomalies.
Binary “Post-AGB” Stars
Authors: Van Winckel Hans , Waelkens Christoffel , Waters Laurens B.F.M.
Published: July 2016

In this contribution we report on our radial-velocity monitoring of optically bright, high-latitude supergiants that appear to be in a post-AGB evolutionary stage. Binarity is a widespread phenomenon among our sample stars. More precisely: all objects with a near-IR excess in their energy distribution turn out to be binaries while the fraction of binaries in our program stars with only a far-IR excess is very small. The orbital periods, the often non-zero eccentricities, and the sometimes large mass functions set strong constraints on the previous evolution in which mass transfer must have been an important ingredient. We have accumulated observational evidence that the presence of a circum-binary dusty disk has an important dynamical and sometimes even chemical influence on the binary and its evolution. Some objects with a high mass function still defy an explanation.
Inferring Mass Loss Rates for Cool Luminous Stars from High-Resolution GHRS Spectra
Authors: Linsky J. L. , Harper G. M. , Valenti J. , Bennett P. D. , Brown A.
Published: July 2016

We discuss GHRS spectra of single and binary late-type stars and describe in detail the spectra of α TrA and of ζ Aurigae obtained at ten orbital phases. The wind properties of α TrA are derived using a complete redistribution radiative transfer code, and we describe the properties of a new code, PRISMA, that we are building to fit line profiles using partial redistribution in a spherically-symmetric geometry. The ζ Aur spectra show that the mass loss process is variable on the timescale of several months, the wind density structure does not repeat from orbit to orbit, and the wind ionization structure is complex.
Molecular Optical and Infrared Emission from the Red Rectangle
Authors: Kerr T. H. , Miles J. R. , Hurst M. E. , Hibbins R. E. , Sarre P. J.
Published: July 2016

A link between stellar and interstellar molecules is discussed with particular reference to optical and infrared emission from the Red Rectangle.
Heavy-Element Nucleosynthesis in AGB Stars
Authors: Smith Verne V.
Published: July 2016

The production of certain neutron-rich elements heavier than iron occurs during He shell-burning on the asymptotic giant branch (AGB). These neutron captures occur at rather low neutron densities and, thus, the resulting heavy-element nucleosynthesis is characterisitic of the so-called s-process. Abundance analyses of the s-process elements in AGB stars can reveal details of the neutron densities and the stage of AGB evolution at which s-processing occurs, as well as the nature of the neutron source. These details derived from observations can constrain models of stars evolving along the AGB. Recent results concerning the nature of the s-process as a function of metallicity and the nature of the neutron source are reviewed.
Carbon Stars in the Early-AGB Stage of Evolution
Authors: Frantsman Ju. L.
Published: July 2016

The assumption that faint carbon stars, as well as high-luminosity carbon stars whose effective temperatures are well above those of ordinary N-type stars in the Magellanic Clouds, are in the early asymptotic giant branch (E-AGB) evolutionary stage, is examined using population simulation techniques.
Properties of individual X-ray sources: (Invited discourse)
Authors: Peterson Laurence E.
Published: July 2016

Observations to determine the spectra and time variations of hard X-rays from cosmic sources have been made from balloons and from the OSO-III satellite. These data have been obtained using actively collimated scintillation counters with apertures between 6 and 24° FWHM, areas between 10 and 50 cm2 and which operate over the 10–300 keV range. The Crab Nebula has been observed on three occasions over a 22-month period between September 1965 and July 1967. The power law spectrum has a number index of 2.0 ± 0.1. No long-term changes were observed over the 30–100 keV range with a limit at 3%/yr. A balloon search with a 10 cm2 Ge(Li) detector for X-ray lines at 62.5 keV, 110 keV and 180 keV due to heavy element radioactive decays which would be produced in the initial Crab explosion based on the Cf254 hypothesis has resulted in upper limits at about 10−3 γ-rays cm2-sec. This is about a factor of 20 above the predicted levels. Simultaneous X-ray and optical observations of SCO XR-1 from OSO-III confirm that X-ray and optical flaring are indeed coincident phenomena, and that although the X-ray intensity increases about a factor of two during the flare, the equivalent temperature of the excess radiation is nearly the same as that of the quiescent object. Upper limits, 95% confidence, on the flux of M-87 at 40 keV have been obtained. These are inconsistent with the flux of 1.2 × 10−4 photons/cm2-sec-keV reported in the literature. CYG X-1 has been observed to have a power law of number index 2.0 ± 0.2. The OSO-III has observed a number of sources in the southern skies including NOR XR-2 and the variable source Centaurus XR-2.
Physical processes in Cygnus X-2
Authors: Wilson Robert E.
Published: July 2016

In developing models for the point X-ray sources the general aim has been to find a common explanation for all such objects. However, important observational differences have already become apparent among the systems having optical identifications. A close examination of the evidence shows that those with the most certain optical identifications, Scorpio X-1 and Cygnus X-2, have very few features in common and, in fact, the model proposed here for Cyg X-2 can probably be excluded for Sco X-1.
The electromagnetic spectrum of the Crab Nebula
Authors: Apparao Krishna M. V.
Published: July 2016

The electromagnetic spectrum of the Crab Nebula has been determined experimentally in the radio, optical, and X-ray regions [1], in which it follows a power law of the type S(v) = Av−α, where S(v) is the power (in watts/m2 sec Hz), A and α are constants, and v is the frequency in Hz. Recent measurements [2–5], however, show a deviation from a power law in the microwave region (see Figure 1). In this paper, we investigate the origin of this deviation and calculate the γ-Ray spectrum due to this increase in the microwave photons via the Compton scattering from high-energy electrons.
Evidence for a galactic component of the diffuse X-ray background
Authors: Cooke B. A. , Griffiths R. E. , Pounds K. A.
Published: July 2016

It is widely believed that the diffuse X-ray background, observed on several occasions over the energy range from 0.25 keV to above 1 MeV has an extragalactic origin. Evidence for this comes from the generally reported isotropy above several keV [1, 2, 3] and the observed galactic latitude dependence at 0.25 keV, believed to result from the interstellar attenuation of these low energy photons in passage through the Galaxy [4, 5].
Measurement of the cosmic X-ray background in the 25–200 keV range
Authors: Brini D. , Fuligni F. , Horstman-Moretti E.
Published: July 2016

An apparatus to study the cosmic X-ray background was launched aboard an ESRO Skylark rocket on May 22, 1967 from the Perdas de Fogu range in Sardinia.
The cosmic γ-ray spectrum near 1 MeV observed by the ERS-18 satellite
Authors: Vette James I. , Gruber Duane , Matteson James L. , Peterson Laurence E.
Published: July 2016

In this paper, we wish to report new data obtained on the total, or omnidirectional, cosmic γ-Ray flux in the 250 keV to 6 MeV range. Flux in this energy range up to 2 MeV was first detected on the Ranger 3 (Metzger et al., 1964) and has been confirmed up to 0.5 MeV and extended to lower energies by a series of rocket (Gorenstein et al., 1969; Seward et al., 1967) and balloon measurements (Bleeker et al., 1966; Rocchia et al., 1967). Observation of the spectrum at higher energies has become of considerable importance since the recent successful detection of galactic 100 MeV γ-Rays by the OSO-3 (Clark et al., 1968).
The Gas Dynamics of Accretion
Authors: Spiegel E. A.
Published: July 2016

The term accretion originally referred, in astronomical contexts, to the capture of mass by stars, and, later, to mass capture by other centers of gravitational force. As such, the process has not proved to be of general importance, in spite of early hopes. However, there are other aspects of the problem which may yet prove worthy of attention in interstellar gas dynamics. In particular, the effects of stars, galaxies, or even clusters of galaxies, on ambient matter streaming by them may be detectable, directly or indirectly, and it is on such possible effects that I shall concentrate here. These effects are related to the original accretion problem but may be thought of separately; nevertheless, I retain the use of the term accretion to refer to all aspects of the motions induced in an ambient medium by a gravitating object.
Mass Balance of Interstellar Gas and Stars
Authors: Salpeter E. E.
Published: July 2016

In this paper I will deal almost exclusively with the interchange of matter between the interstellar gas and the stars. Other possible forms of interchange, such as mass-loss to and accretion from intergalactic matter e.g., Oort's (1969) views on mass flowing into our Galaxy, will be discussed later I hope.
Interstellar Molecules
Authors: Stecher Theodore P.
Published: July 2016

The observation of molecules in the interstellar medium offers an excellent oppor- tunity to specify the physical conditions present there. This must be done through the combined use of theory and observation. In the last few years the advancement in this area has accelerated spectacularly. McNally (1968) reviewed the subject and Spitzer (1968) included molecules in his more general review; these are both excellent references and the reader is referred to them for the development and state of the subject in 1966.
Protostars and Other Neutral Condensations in Hii Regions
Authors: Mezger P. G.
Published: July 2016

I have been invited to report on globules and OH emission sources. However, I will extend the topic to protostars and other condensations in Hii regions, of which globules and OH emission sources are only special, although rather conspicuous, objects.
Final Discussion
Authors: Thomas R. N.
Published: July 2016

In the present form the Final Discussion is divided into three sections: 1. Discussion on the Overall Energy Flow in the Interstellar Medium; 2. Summaries and Suggestions for Future Research (more or less prepared talks); 3. Summaries and Suggestions for Future Research (more or less free discussion). The discussion in Section 1 actually took place on Saturday, September 13, but it belongs in the Final Discussion. The (invited) summary papers, presented in Section 2, were given by Parker, van Woerden, and Kaplan. Section 3 starts with the remarks by Busemann on the interrelation between interstellar gas dynamics and aerodynamics, as viewed by an aerodynamicist; these remarks were made on Tuesday, September 16. The rest of Section 3 is taken up by the actual discussion held on the final day of the Symposium.
Distribution of Dust and H II Regions in Spiral Galaxies
Authors: Lynds Beverly T.
Published: July 2016

The bright Hii regions of a galaxy are always found near or in regions of high obscuration. It is also generally true that the dust lanes of a galaxy better define a spiral pattern than do Hii regions. There appears to be a correlation between the size of the central region and the number of Hii regions in a galaxy.
Activity in the Nuclei of Seyfert Galaxies in the Visual and Infrared
Authors: Pacholczyk A. G.
Published: July 2016

This paper reports (1) a possible 5.1 yr period in the optical variations of the nucleus of NGC 4151; and (2) variations with a time-scale of a few days in the 2.2 micron flux density of NGC 1068, implying that the size of the infrared emitting region is not larger than a few times 1015 cm.
A Study of the Continua of the Nuclei of Galaxies
Authors: Alloin D. , Andrillat Y. , Souffrin S.
Published: July 2016

Many people have attacked the problem of synthesizing the stellar population of the galaxies. We have performed such a synthesis, by using only the intensities of absorption lines in the nuclei of galaxies. It is then possible to obtain a synthesized continuous spectrum even if there are several possible solutions for the stellar composition, and the computed continuum does not vary much with the assumed model of stellar population.

The method is to fit the equivalent widths of the absorption lines using different stellar compositions. In order to avoid any instrumental effect, we have observed different lines and bands from 3500 to 8500 å in stars of various well-known stellar types and luminosity classes, under the same conditions as the galaxies.

We have applied this method to some ‘ordinary’ nuclei and to some Seyfert ones. As an example, we show the results for M81 and for NGC 1068.
The Radio Structure of Quasars
Authors: Miley G. K. , Macdonald G. H.
Published: July 2016

The statistics on the angular structures of quasars have been more than doubled. Quasars are discussed from both morphological and statistical viewpoints and the angular diameter-redshift relation has been confirmed.
Neutral Hydrogen in Compact Galaxies
Authors: Heidmann J.
Published: July 2016

In collaboration with Messrs P. Chamaraux and R. Lauqué we have observed five objects of compact type or with compact parts at Nanĉay with the 21-cm line of neutral hydrogen. Details will be found in Astron. Astrophys.8, 424, 1970.
Supermassive Disks
Authors: Wagoner R. V. , Salpeter E. E.
Published: July 2016

The ultimate source of energy in compact objects is investigated. The model is a highly flattened body of mass ≳ 104M⊙, supported by centrifugal force in two directions and by gas and radiation pressure in the third. The properties of this model are compared with those nearly spherical supermassive stars introduced by Hoyle and Fowler.
Matter-Antimatter Annihilation as an Energy Source in Seyfert Galaxies
Authors: Steigman G. , Strittmatter P. A.
Published: July 2016

The extreme infrared luminosities of some Seyfert galaxies place severe requirements on the efficiency of the energy source. It is attractive to suggest that matter-antimatter annihilation supplies the necessary energy source; efficiencies of up to ∼50% are, in principle, obtainable. However, there is a price to pay for such an explanation: gamma rays and neutrinos.

In a typical nucleon-antinucleon annihilation roughly ⅓ Mc2 is released in electron-positron pairs, ∼⅔ Mc2 in ∼3 gamma rays and ∼Mc2 in ∼3 electron-neutrinos and ∼6 muon-neutrinos. As a result, if the observed infra-red power is to be derived from the energy in electron-positron pairs, then the flux of gamma rays would be 102-103 times the upper limits to the gamma ray flux. It is, of course, possible to account for the absence of the gamma rays by insisting that they be absorbed in the source. The neutrinos, however, will not be stopped and hence provide the possibility of testing the annihilation hypothesis.

We have computed the spectrum of neutrinos produced in annihilation. Assuming the product of the space density and infrared luminosity of Seyfert galaxies varies with redshift (z) as: L (z) n (z) = L0n0 (1 + z)m we have computed the flux of μ-neutrinos contributed by all Seyfert galaxies out to a given red-shift for m = 3 and m = 6.5 (strong evolution). Further, assuming the “3K” and “0.3 mm” background radiation fields to be caused by a burst of “Seyfert type” objects at appropriate redshifts, we have again computed the expected μ-neutrino flux. When these results are compared with present limits on the flux of μ-neutrinos at the Earth, as determined from experiments performed by several groups deep underground, it emerges that the predicted flux is comparable to or greater than present upper limits. Thus, annihilation probably does not supply the infrared sources in Seyfert galaxies with the energy they require.
Transient Annular Structures in Exploding Galaxies
Authors: Sěrsic J. L.
Published: July 2016

The explosive events going on in the central parts of some galaxies are related to a very high mass concentration. As an explosion is actually a drastic rearrangement of the concerned masses with energy release, the binding energy of the central core will change and, correspondingly, its effective gravitational mass. A test particle far from the nuclear region, although within the galaxy, will be moving accordingly in a variable-mass Newtonian gravitational field.

On the other hand the observations suggest that explosions in galaxies have axial symmetry, so we are concerned with the global properties of the motion of a particle in a variable mass axisymmetric gravitational field. In order to get rid of the mass variation a space-time conformal transformation is made, which, after imposing some not very restrictive conditions, leads to a conservative potential in the new variables. This new potential has additional terms due to the elimination of the variable mass. The equations of motion in the new variables provide the motion of the test particle relative to an expanding or contracting background which depends on the choice of the transformation and the law of the mass variability. The problem is, at this point, formally similar to Hill's. It is possible to write an equation for the relative energy (a generalization of Jacobi's integral) and also to define surfaces of zero relative velocity for the infinitesimal particle. The general topological properties of these surfaces require singular points along the symmetry axis (analogous to the collinear Eulerian points) and also a dense set in a circumference on a plane perpendicular to the symmetry axis (analogous to the Lagrangian points). The latter one is the main feature characterizing the topology of the zero relative velocity surfaces. Even when we lift some of the restrictive conditions, the Lagrangian ring preserves its properties, as for example, the one of being the only region where zero-velocity curves and equi-potentials coincide when the configuration evolves in time (in the transformed space-time).

It is easy to understand that the topology of the surfaces is kept when we reverse the transformation and go back to physical space-time. If the dust, gas or stars in the system has definite upper limits for its Jacobian constants, spatial segregation of them will arise, as is the case in radio-galaxies such as NGC 5128, NGC 1316, etc. where ringlike dust structures are observed.
Number Counts and Spectral Distribution of Radio Sources at Centimeter Wavelengths
Authors: Pauliny-Toth I. I. K. , Kellermann K. I. , Davis M. M.
Published: July 2016

The results of a survey of selected regions of sky made at a frequency of 5 GHz, and of measurements of the spectral index distributions for sources selected from low frequency surveys are presented. The source counts and spectral distribution at 5 GHz are in excellent agreement with those expected from surveys made at lower frequencies. There is no significant dependence of the spectral distribution on flux density in any of the surveys we have investigated, implying either a low redshift for the sources, or a systematic change in their properties with redshift.
Ghost Images in a Universe with Inhomogeneous Mass Distribution
Authors: Barnothy J. M. , Barnothy M. F.
Published: July 2016

An attempt is made to explain Morgan cD supergiant galaxies, the microwave background radiation and extended discrete radio sources as ghost images in a universe of strong positive curvature and inhomogeneous mass distribution.
Evolution of Cometary Orbits on a Cosmogonic Time Scale
Authors: Chebotarev G. A.
Published: July 2016

A review of modern concepts of the evolution of cometary orbits for the time span of some million years is presented. These concepts are based on the hypothesis of the existence of the Oort cloud, the theory of diffusion developed by Shtejns, and the work by Kazimirchak-Polonskaya concerning the influence of the major planets in transforming cometary orbits. All these ideas are currently being developed with the aid of rigorous mathematical methods by cometary researchers in various parts of the world.
Physical Observations of the Short-Period Comet 1969 IV
Authors: Churyumov K. I. , Gerasimenko S. I.
Published: July 2016

The new short-period comet Churyumov-Gerasimenko, discovered by the authors on plates taken by the Kiev University cometary expedition to Alma-Ata in September 1969, was systematically photographed with fast telescopes at Byurakan and Alma-Ata until March 1970. Measurements were made of the photographic magnitude of the photometric nucleus, as well as of the photographic and photovisual integral magnitudes. The variations in nuclear magnitude were found to be well correlated with changes in the total sunspot area. The integral photometric parameters are Hy = 11.91±0m.54 and n=4.0±0.8 (in the photographic spectral region). Deviations of the tail axis from the prolonged radius vector were considerable. A spectrogram shows the continuum and emission of CN, C2 and C3 in the head, the continuum and a single emission (perhaps CO+) in the tail.
A Numerical Interpretation of the Homogenization of Observational Material for One-Apparition Comets
Authors: Sitarski G.
Published: July 2016

The formulae developed by Bielicki for the objective weighting of observations are combined with an orbital improvement method in which the effects of perturbations are included in the differential coefficients. The procedure is applied to the orbit of comet 1953 I.
The Influence of Properties of a Set of Observations on the Weights of Determination of the Orbital Elements of a One-Apparition Comet
Authors: Bielicki M.
Published: July 2016

An expression is developed for the dependence of the weights of the determination of the elements of the orbit of a one-apparition comet on the number of observations, the length of the observational interval and the apparent motion of the comet during that interval.
Standardization of the Calculation of Nearly Parabolic Cometary Orbits
Authors: Nikonova L. E. , Bokhan N. A.
Published: July 2016

A complex of standard programmes has been developed for computing nearly parabolic orbits. The true anomaly is related to the time using Herrick's formulae. Perturbations are calculated by Encke's method.
Détermination D'orbites paraboliques à partir de N observations au moyen de l'ordinateur électronique
Authors: Debehogne H.
Published: July 2016

The Olbers-Banachiewicz method for computing parabolic orbits has been programmed. A least-square improvement of the orbit is obtained by varying the first and last geocentric distances.
On the Determination of Nongravitational Forces Acting on Comets
Authors: Zadunaisky P. E.
Published: July 2016

Some recent investigations on the existence and nature of nongravitational forces acting on comets have required the application of a good deal of high precision numerical procedures. In this paper these procedures are examined critically; special attention is given to cases where difficulties may appear when a comet makes a close approach to a planet or the Sun.
Periodic Comet Tempel-Tuttle and the Leonid Meteor Shower
Authors: Kondrat'Eva E. D.
Published: July 2016

P/Tempel-Tuttle, the comet associated with the Leonid meteor shower, was observed at only two of its last four passages through perihelion, in 1865–1866 and 1965. We have re-reduced the observations in 1865–1866, and with the help of Belyaev's computer programme for numerical integration have linked the two apparitions.
Determination of the Mass of Jupiter from Observations of 10 Hygiea During 1932–1969
Authors: Chernykh N. S.
Published: July 2016

An attempt has been made to derive the mass of Jupiter from modern observations of the minor planet 10 Hygiea. The calculations have been made using computer programmes prepared at the Institute for Theoretical Astronomy. From 250 observations 1932 to 1967 we obtained the reciprocal mass 1047.345±0.040 (rms error). After excluding some less reliable observations and allowing for the elliptic aberration terms we obtained 1047.326±0.033. By means of a more sophisticated computer programme and utilizing 100 additional observations, some of them made in 1969, we obtained the value 1047.324±0.023. Our results are compared with recent determinations by other investigators.
The Influence of Minor Planets on the Motions of Comets
Authors: Shtejns K. A. , Zal'Kalne I. E.
Published: July 2016

It is shown that in a sufficiently small interval there is a uniform distribution of the minimum distances between the orbit of a comet and the orbits of minor planets. It is also shown that there is a uniform distribution of the distance of the planet from the point of closest approach when the comet reaches that point. It is found that P/Daniel may collide with a microplanet of mass 4.05 × 108 g during 100 revolutions. It is possible for one of 60 short-period comets to meet during 100 revolutions a microplanet of mass 9.9 × 109 g and radius 8.6 m. The changes in reciprocal semimajor axis of a comet arising from close encounters with minor planets are also studied but found to be insignificant.
Physical Processes in Cometary Atmospheres
Authors: Dolginov A. Z.
Published: July 2016

Formulae are obtained for the distribution of molecules in the cometary head, taking into account the conditions of hydrodynamic and free molecular flow in various regions around the nucleus. Experimental data are used to derive physical parameters near the nuclei of comets 1952 III, 1955 V, 1957 III, and 1960 II and the rate of decrease of mass. The possibility of chemical reactions in the region close to the nucleus is discussed. Gas condensation is shown to be a possible cause of dust formation under the conditions existing near the nucleus, and this process may be responsible for the major portion of the cometary dust component. The observed grouping of synchrones in the cometary tail can be explained on the assumption that the nuclear surface comprises two (or more) areas differing essentially in evaporation rate, the amount of matter ejected varying over the rotation period of the nucleus. Charged dust particles are shown to form, with electrons and ions, a common medium, i.e., dust plasma, which can be treated by the same methods used for ordinary plasma. Special investigations appear to be desirable when comets intersect meteor streams.
On the Sizes of Cometary Nuclei
Authors: Konopleva V. P. , Shul'Man L. M.
Published: July 2016

Three methods have been developed for determining the sizes of cometary nuclei. They are all based on the spotted model for an icy nucleus. The first method follows from the relationship between the icy (unshielded) area and the total absolute brightness, although the quantity determined is actually a function of the radius and the shielding coefficient. The second method is based on analysis of the secular brightness decrease and the assumption that it is possible to establish when a new surface layer of dust starts to form; in practice, this method is found to be applicable only in the cases of P/Pons-Winnecke and P/Tuttle. The third method is also based on the secular brightness decrease, and it requires some assumption about the volume fraction of dust in the nucleus.
Rotation Effects in the Nongravitational Parameters of Comets
Authors: Sekanina Z.
Published: July 2016

The effects of rotation of a cometary nucleus on the character of nongravitational parameters are discussed. It is suggested that the change of a nongravitational acceleration to deceleration (and vice versa) may be related to a precessional motion of the nucleus, or to secular variations in the lag angle coupled with severe orbital modifications.
Evolution of Short-Period Cometary Orbits Due to Close Approaches to Jupiter
Authors: Havnes O.
Published: July 2016

Evolution of short-period cometary orbits under the influence of close and moderately close approaches to Jupiter is studied. We have restricted the discussion to orbits in Jupiter's orbital plane and have neglected distant perturbations by Jupiter. The general evolution is a diffusion towards orbits of larger semimajor axes and a loss of comets, mainly due to ejection along hyperbolic orbits. We have found that the dynamical evolution of the orbits severely alters the assumed initial distribution of orbits during a time of some hundred years. We also tried to obtain an idea of the importance of close approaches as compared to the effect of moderate approaches to Jupiter for the evolution of the orbits. This was done by calculating the evolution of a group of comets twice, first considering the effect of perturbations up to a distance of 1.0 AU from Jupiter and then to a distance of 2.0 AU. The statistical results of the two calculations are in general agreement, indicating that close approaches to Jupiter mainly determine the evolution of the short-period comets.
Large-Scale Solar Magnetic Fields
Authors: Bumba V.
Published: July 2016

The characteristics of the large-scale distribution of the solar magnetic fields on the basis of a series of solar magnetic synoptic charts covering more than 15 years of observations are given. The major part of our information concerns the morphology and only some results deal with the kinematics of the field distribution. Results of averaged solar magnetic field fluxes and polarity reversal studies as well as of preliminary investigation of the very-low angular resolution magnetic measurements are given. The regular zonal and sectoral distribution of photospheric background fields, the different role or visibility of structures in both polarities is discussed. The reflection of both main types of the longitudinal distribution of large-scale solar background magnetic fields (the 27-day, the 28–29-day successions, the ‘supergiant’ structures) in the interplanetary magnetic field distribution is also considered.
About the Relation Between the Limb Effect of the Redshift on the Sun and the Large-Scale Distribution of Solar activity
Authors: Ambrož P.
Published: July 2016

The measurement of the magnitude of the limb effect was homogenized in time and a recurrent period of maxima of 27.8 days was found. A relation was found between the maximum values of the limb effect of the redshift, the boundaries of polarities of the interplanetary magnetic field, the characteristic large-scale distribution of the background magnetic fields and the complex of solar activity.
Solar Cycle Evolution of the General Magnetic Field
Authors: Yoshimura Hirokazu
Published: July 2016

The data from magnetic field synoptic charts at Mt. Wilson for 16 years are separated into axisymmetric and nonaxisymmetric fields. The axisymmetric field derived simply by averaging over longitude corresponds to the general magnetic field and can be regarded as reflecting the poloidal (radial) field since bipolar magnetic fields which have been regarded as reflecting the toroidal field are cancelled out by the averaging. The evolution of pattern of the latitudinal distribution of this field shows a conspicuous appearance similar to the Butterfly Diagram of sunspots but having two branches of different polarity in each hemisphere. The two branches start from the middle latitudes, and one branch propagates towards the pole and the other toward the equator. This shows that the solar general magnetic field behaves like a quadrupole not a dipole as was previously believed. This feature is exactly what has been predicted by a numerical solar cycle model driven by the dynamo action of the global convection. Another axisymmetric field is also derived by averaging over longitude the absolute value of the magnetic field after subtracting the poloidal field. This field corresponds to the toroidal field since if this field is averaged over longitude it vanishes. The evolutionary pattern of the latitudinal distribution of this field shows a feature quite similar to the Butterfly Diagram of sunspots. These features of the two fields become conspicuous only after averaging over many rotations, e.g., over 27 rotations (2 yr): such a diagram averaged over a small number of rotations shows rather large noise.
Coronal Bright Points
Authors: Golub L. , Krieger A. S. , Vaiana G. S.
Published: July 2016

Soft X-ray images of the inner corona obtained with the AS&E spectrograph telescope aboard Skylab revealed the presence of coronal bright points in far greater numbers than had previously been suspected. Bright points are associated with bipolar magnetic features with typical diameters of 1–2 × 104 km, mean lifetime of eight hours and magnetic flux 1019–1020 Mx. Several thousand bright points emerge over the solar surface per day, thereby bringing up more magnetic flux than is contributed by the larger active regions during the period of observation, May 1973 to February 1974. Bright points identified in X-ray photographs are seen as small (5–10″) emission features in ground-based Hα and Ca K spectroheliograms as well as in transition region lines observed in other Skylab instruments. Typical bright point temperatures are 1.5–2 × 106 K and typical densities are ∼ 5 × 109 cm−3.
Some Results of the Space Distribution of the Activation Vector of the Filaments in the 11-Year Cycle
Authors: Kasinskij V. V. , Smolkov G. Ya. , Zubkova G. N.
Published: July 2016

In order to obtain new information on the manifestation of basic mechanisms of solar activity with the sunspot cycle development we have studied peculiarities of the latitude-time distribution of activation positions and suddenly disappearing filaments with respect to sunspot groups of cycles 18 to 20.
A Boussinesq Model for the Convection Zone and the Solar Angular Velocity
Authors: Belvedere G. , Paternò L.
Published: July 2016

In this paper we study the dependence of the solar angular velocity on depth and latitude as produced by a meridional circulation in the convection zone.
Two-Dimensional Stochastic Motions and the Problem of Differential Rotation for Unrestricted Rotational Rates
Authors: Rüdiger G.
Published: July 2016

For dealing analytically with the problem of differential rotation we investigate the spatial dependence of the angular velocity in a rotating turbulent fluid. The original turbulence unaffected by the rotation is assumed to be two-dimensional, where the stochastic motions completely lie in the horizontal planes. From the expression describing the relation between the correlations of rotating and nonrotating turbulent fields the meridional flux of momentum is derived. The resulting rotational law is determined by using Bochner's theorem for homogeneous turbulence as well as the characteristic scales of the turbulence field considered. The conclusions are:

(a)

The angular velocity ω is increasing toward the outer layers.

(b)

For 2 Ω ≪ ωc (ωc frequency of turbulent mode) the Biermann-Kippenhahntheory of anisotropic viscosity is deduced. An equatorial acceleration is only caused by a meridional circulation.

(c)

For 2 Ω ≲ ωc a latitudinal dependence of ω is possible without any meridional circulation. If the two-dimensional eddy viscosity is negative the equatorial regions are accelerated. The expression for the two-dimensional eddy viscosity which has been derived earlier allows negativity in contrast to that for three-dimensional eddy viscosity. The scale length and the scale time of supergranulation as well as of giant cells lead to negative two-dimensional eddy viscosity.
A Model of the Solar Cycle Driven by the Dynamo Action of the Global Convection in the Solar Convection Zone
Authors: Yoshimura Hirokazu
Published: July 2016

Extensive numerical studies of the dynamo equations due to the global convection are presented to simulate the solar cycle and to open the way to study general stellar magnetic cycles. The dynamo equations which represent the longitudinally-averaged magnetohydrodynamical action (mean magnetohydrodynamics) of the global convection under the influence of the rotation in the solar convection zone are considered here as an initial boundary-value problem. The latitudinal and radial structure of the dynamo action consisting of a generation action due to the differential rotation and a regeneration action due to the global convection is parameterized in accordance with the structure of the rotation and of the global convection. This is done especially in such a way as to represent the presence of the two cells of the regneration action in the radial direction in which the action has opposite signs, which is typical of the regeneration action of the global convection. The effects of the dynamics of the global convection (e.g., the effects of the stratification of the physical conditions in the solar convection zone) are presumed to be all included in those parameters used in the model and they are presumed not to alter the results drastically since these effects are only to change the structure of the regeneration action topologically.
On the Distribution of Angular Velocity in the Sun
Authors: Tuominen Jaakko
Published: July 2016

The angular velocity distribution as a function of heliographic latitude is directly observed at the solar surface. Also the dependence of the angular velocity on the distance from the solar centre can be studied observationally for the outermost layers of the Sun. But within the Sun the study of angular velocity depends very much on assumptions. One possibility to study the problem is given by the fact that in a bipolar magnetic group the leader is compact while the follower is dispersed over a large area. In Leighton's theory, following Babcock, this phenomenon is explained, in principle, in the following way: Slide 1. When a magnetic rope, as a result of magnetic buoyancy, rises to the surface, it is twisted by differential rotation. Dashed lines in the figure represent isotachial surfaces. When the rope has risen to the surface, the two ends are twisted in opposite directions. The surface differential rotation continues to twist one of the now free ends of the rope, while it untwists the other free end. Both twisting and untwisting are, in fact, very slow. They are fastest at the latitude of 35°, where the magnetic rope is rotated once in 26 days. We understand that the distribution of angular velocity within the Sun is involved in this picture. The twisting in the interior can be written equal to the untwisting of the follower spot produced by the surface differential rotation. Of course there are many solutions. Slide 2 gives two of them. The lines represent calculated isotachial surfaces and the numbers give the observed angular velocities in radians per day. In the left-hand side distribution the velocity decreases inwards, while in the right-hand side distribution it increases inwards. The right-hand side distribution is also consistent with the conclusion derived from observations that the tilt of sunspot axes from the vertical is relatively small, and with the observation that at the equatorial plane, near the surface, the rotational velocity does not vary with depth.
The Sun as a Magnetic Star
Authors: Wilcox John M. , Svalgaard Leif
Published: July 2016

The Sun as a magnetic star is described on the basis of recent work on solar magnetism. Observations at an arbitrary angle to the rotation axis would show a 22-year polar field variation and a 25–day equatorial sector variation. The sector variation would be similar to an oblique rotator with an angle of 90° between the magnetic and rotational axes.
Influence of Abundances Upon Stellar Atmosphere Calculations
Authors: Baschek B.
Published: July 2016

The basic equations for constructing a stellar atmosphere (hydrostatic equilibrium, flux constancy, radiative transfer, convective instability) are briefly summarized. While the parameters Teff (effective temperature) and g (surface gravity) are directly contained in these equations, the element abundances ∈i enter only indirectly through the thermodynamic properties (such as electron pressure, entropy, …) and the absorption and scattering coefficients of stellar matter.

The equation of state, convection, the effects of the absorption coefficients (particularly of line absorption) on the temperature stratification, and the role of velocity fields (microturbulence) are discussed in some detail, emphasizing their dependence on the abundances.

From a given model atmosphere, a ‘theoretical spectrum’ (colours, bolometric correction, line strengths etc.) can be calculated. The (relative) fluxes emerging at the surface are essentially determined by the temperature gradient and the absorption coefficients at the frequencies under consideration. The basic goal of quantitative classification, however, is the inverse problem, namely to deduce the stellar parameters from selected observed spectral criteria. Aspects relevant to this problem such as the question of uniqueness and the occurrence of possible systematic errors (even when using differential analysis techniques) are briefly sketched and illustrated by some examples.