bluuebunny/crossref_metadata_2025 huggingface dataset:
Mv−σ Relation: A Universal Law?
Authors: Zaggia S.R.
Published: July 2016

Globular clusters (GC) of different galaxies are thought to be similar in their intrinsic nature, despite the very different environments in which they reside. This statement is mainly based on the luminosity function of GC that appear to be similar for galaxies structurally very different (Secker and Harris 1993). To support the above conclusion only few other GC parameters have been used: integrated colors and metallicity index (Harris 1991). Now, there is a growing body of GC velocity dispersions of other local group galaxies which can be used to perform a useful comparison. The tool for such a comparison is the correlation between GC total luminosity, Mv, and velocity dispersion, σ, found by Djorgovski (1991). This is one of the best non trivial correlation of GC structural parameters that can give important answers to the problems of the formation and evolution of GCs.
On the Retention of Globular Cluster Neutron Stars
Authors: Drukier G.A.
Published: July 2016

Although globular clusters are known to contain a population of neutron stars, the recent finding by Lyne and Lorimer (1994) that field neutron stars are formed with a mean “kick” velocity of 450 km s−1 implies that globular clusters would retain very few neutron stars. The number of neutron stars is important when discussing cluster mortality and the formation rate of millisecond pulsars.
ASCA observation of ω Centauri
Authors: Negoro H. , Kawashima K.
Published: July 2016

The number of compact stars such as white dwarfs, neutron stars, and black holes in globular clusters gives us information on binary formation rates and dynamical history of the clusters.
On the Role of dK and dM Stars in Piling up the Total Mass of Star Clusters
Authors: Szécsényi-Nagy G.
Published: July 2016

Although many projects were aimed at identifying nearby red dwarfs, the catalogues may be complete up to a limiting distance of 5 pc only and may be reliable to 10 pc. From recent observations it is evident that their absolute visual brightness (MV) ranges from about 6 to at least 18.5 what means that an average dK0 star is at least 100,000 times brighter than red dwarfs of the latest spectral subclasses. The photon detecting efficiency of our instruments is to be increased that these can measure late dM stars from the same distance from which dK stars can be analysed now. Another solution is offered by the flare-active red dwarfs which may be 1000 times brighter during their flare ups than usually.
Pre-Collapse Evolution of Galactic Globular Clusters
Authors: Fukushige Toshiyuki , Heggie Douglas C.
Published: July 2016

We investigated collisionless aspects of the early evolution of model star clusters. The effects of mass loss through stellar evolution and of a steady tidal field are modelled using N-body simulations. Our results (which depend on the assumed initial structure and the mass spectrum) agree qualitatively with those of Chernoff & Weinberg (1990), who used a Fokker-Planck model with a spherically symmetric tidal cutoff. For those systems which are disrupted, the lifetime to disruption generally exceeds that found by Chernoff & Weinberg, sometimes by as much as an order of magnitude.
Are Gravothermal Oscillations Gravothermal?
Authors: McMillan Stephen L. W. , Engle Kimberly A.
Published: July 2016

We examine critically the properties of the large-amplitude oscillations seen in Fokker-Planck simulations of globular clusters, with both continuous and stochastic binary heating, and compare them to the defining characteristics of gravothermal oscillations.
Itinerancy of Quasiequilibria in One-Dimensional Gravitating Systems
Authors: Tsuchiya T. , Gouda N. , Konishi T.
Published: July 2016

One-dimensional self-gravitating many-body systems consist of N identical parallel sheets which have uniform mass density m and infinite in extent in the (y, z) plane. We call the sheets particles in this paper. The particles are free to move along x axis and accelerate as a result of their mutual gravitational attraction. The Hamiltonian of this system has a form of
where m, vi, and xi are the mass (surface density), velocity, and position of ith particle respectively.
On the Dynamics of Young Open Star Clusters in the Joint Field of the Galaxy and of a Star Formation Region
Authors: Danilov V. M.
Published: July 2016

The young open star clusters (OCl) with ages of 107 − 108 years in the overwhelming majority of cases are located in the regions of a star formation which are the massive and extensive gas - star complexes (GSC) in our Galaxy. The typical sizes of GSCs are near 600 pc in projection at the Galaxy plane and the masses of such complexes are in range ∼ (105 − 107) M⊙ (Efremov (1989)). It is well known that the old open clusters avoid the regions of an active star formation in our Galaxy. As a result the structural and dynamical parameters of OCls depend on their ages and their locations relatively the nearest GSCs centres.
Dynamics of Collapsing Shells
Authors: Theis Christian
Published: July 2016

In the last decade several scenarios for the formation of globular clusters have been suggested. One of these models starts with an OB-association exploding near the center of a molecular cloud (Brown et al., ApJ 376, 115 (1991)): The expanding shell sweeps up the cloud material and later the expansion will be decelerated or stopped by the external pressure of the ambient hot gas. The shell itself can break into fragments and form stars. If the total energy of these stars is negative, they will recollapse and eventually form a bound system. According to this idea the dynamics of a thin stellar shell has been studied.
Observations of Mass Loss and Circumstellar Matter around Cool Carbon Stars
Authors: Evans T. Lloyd
Published: July 2016

Spectroscopy and infrared photometry of carbon stars show three distinct forms of circumstellar matter. IRAS 12311-3509 probably has an edge-on disk and the spectrum is dominated by resonance emission from atoms and molecules in the vicinity. The long-period variables V Hya and R Lep are undergoing deep fadings, apparently caused by dust formation around the star, while variable emission from circumstellar gas is seen. The semiregular variable T Mus showed absorption bands from very cool material during an unusual episode in 1994.
Upper-air fluorescence as a tool in X-ray astronomy and searches for X-rays from NP 0532 and other pulsars
Authors: Charman W. N. , Drever R. W. P. , Fruin J. H. , Jelley J. V. , Elliot J. L. , Fazio G. G. , Hearn D. R. , Helmken H. F. , Rieke G. H. , Weekes T. C.
Published: July 2016

The object of this paper, which describes work which has been carried out in close collaboration between members of our two groups, is to present the background of the upper-air fluorescence technique as a viable ground-based tool for studies of cosmic X-rays. After a discussion of the characteristics, merits and limitations of the technique, we describe some preliminary experiments which have been carried out, both separately and also jointly, with our respective installations. These are sited at Mount Hopkins (the SAO field station at 2300 m altitude near Amado, Arizona) and at Sparsholt Firs (approx. 300 m altitude, on the Berkshire Downs, near Harwell).
Properties of individual X-ray sources: (Invited discourse)
Authors: McCracken K. G.
Published: July 2016

Prof. McCracken did not communicate any text or Summary of his invited discourse.
Rocket observations of Virgo XR-1
Authors: Adams D. J. , Cooke B. A. , Evans K. , Pounds K. A.
Published: July 2016

Skylark 723, launched at 10.30 GMT on 12th June 1968 was an unstabilised rocket carrying two proportional counter detectors, each of 1385 cm2 effective area. Detector C1 covered the energy range 1.4 to 2.5 keV and detector C2 the range 2.0 to 18 keV. The detector outputs were analysed into 4 and 9 energy channels respectively. The field of view of each detector was 28° and 4° (FWHM) with the greater collimator extension mounted parallel to the longitudinal rocket axis for C2 and 6/10 of the C1 detector, the remaining 4/10 of the C1 collimator being canted at 40° to the major axis. During the flight, the rocket spun at a constant rate of 75° per sec whilst the spin axis slowly precessed about a flat cone, thereby surveying some 80% of the visible sky. On 25 consecutive scans the Vir XR-1 source, which by chance lay near the precession axis, crossed the field of view of both detectors. The count rate profiles for twenty scans in which the source passed within 21° of the centre of the field of view have been added together for each detector, resulting in the totals shown in Figure 1. Significant peaks are seen in the position of Vir XR-1 for both detectors and these have been fitted with the measured transmission profiles of the respective collimators assuming parallel incident radiation. The peaks are consistent with the observation of X-rays from a single point source.
On the magnitude-color relation for Cygnus X-2 and WX Centauri
Authors: Mumford George S.
Published: July 2016

While the short-term fluctuations in the brightness and color of the source Sco X-1 have been found to be correlated in the sense that the system is bluest when brightest, such a result does not appear in the observations of Cyg X-2 or WX Cen described here.
On the nature of the X-ray sources Scorpius X-1 and Centaurus X-2
Authors: Sofia Sabatino
Published: July 2016

Preliminary evidence is presented which indicates that the star WX Cen, associated with the X-ray source Centaurus X-2 belongs to the Scorpio-Centaurus association. It is pointed out that this result greatly strengthens the similar results for the source Scorpius X-1, and lends support to the idea of the existence of a class of X-ray stars formed by young, subluminous objects, probably supernova remnants, thus neutron stars.
X-ray pulsar in the Crab Nebula
Authors: Novick R.
Published: July 2016

No text nor Summary was communicated by the Author.
Radio, optical and X-ray emission from pulsars
Authors: Bertotti B. , Cavaliere A. , Pacini F.
Published: July 2016

We examine the electromagnetic spectrum of the Crab Nebula pulsar NP 0532. The present observations are in rough agreement with the idea that the orbit of the radiating particles involves two different radii of curvature. One of the possible models requires electrons with a typical energy of the order of 100 MeV and a density ≈ 109 cm−3. A correlation length of about 10 cm could then give the coherence of the radio emission. Slow pulsars are unlikely to emit an appreciable amount of optical or X-ray radiation but a weak infrared emission is possible.
Observations on diffuse cosmic X-rays in the energy range 20–120 keV
Authors: Agrawal P. C. , Biswas S. , Gokhale G. S. , Iyengar V. S. , Kunte P. K. , Manchanda R. K. , Sreekantan B. V.
Published: July 2016

In this paper we present observations of the diffuse background X-rays in the energy range 20–120 keV, based on two balloon experiments carried out from Hyderabad (latitude 17.6°N, longitude 78.5°E), India. The flights were made on April 28, 1968 and December 22, 1968. The detector used was a NaI(Tl) crystal of effective area 97.3 cm2and thickness 4 mm. The crystal was surrounded both by active and passive collimators. The passive collimator was a cylindrical graded shield of lead, tin, and copper, and the active collimator was a plastic scintillator surrounding the shield. The FWHM of the telescope was 18.6° and the geometrical factor for isotropic radiation 13.2 cm2sr. The pulses from the NaI crystal were sorted into ten contiguous channels extending from 17 to 124 keV. An Am241source came into the field of view of the telescope periodically and provided in-flight calibration of the detector. All the information was recorded on photographic film.
Results of two balloon flights for the detection of high energy γ-rays
Authors: Niel M. , Vedrenne G. , Bouigue R.
Published: July 2016

After many years of fruitless research on primary γ-Rays, the results obtained by Clarket al.[1] with the OSO-3 satellite, proved for the first time the existence of a primary γ-Ray flux. The study of the distribution of this radiation showed a strong anisotropy in the direction of the galactic disk and, more precisely, in the direction of the galactic center. Now the production of γ-Rays in the spatial medium is related to high energy processes and to the presence of relativistic electrons. The high energy processes bring about an emission of γ-Rays essentially by decay of the π° mesons created for instance, by the interaction of cosmic radiation with interstellar matter or by matter-antimatter annihilation. The relativistic electrons can lead to an emission of γ-Rays by various processes: in particular, by bremsstrahlung of the electrons in the interstellar matter or by the Inverse Compton effect with the photons of the stellar light or of the infrared radiation background.
Soft X-rays from the Galaxy
Authors: Rees M. J.
Published: July 2016

Below 1 keV, analyses of X-ray background data are complicated by galactic absorption effects, which cause the received intensity to vary with galactic latitude. Bowyer et al. (1968) observed that the diffuse background did not fall off as rapidly as was expected towards the galactic plane. One plausible interpretation of their data would be to suppose that a significant flux of soft X-rays emanates from the disc itself. I wish to discuss what could be inferred about the latter component from improved observations of its latitude-dependence, and by indirect methods.
Observational Aspects of Galactic Magnetic Fields
Authors: Verschuur G. L.
Published: July 2016

I will review the impressive advances in the observations of the galactic magnetic field made since the time of van de Hulst's review at the 1966 Noordwijk Symposium (van de Hulst, 1967). Most of these observations are so recent that the consequences have not yet been worked out very well and are in need of discussion. Luckily the emphasis in the present Symposium, unlike that in many others, is on discussion. For this reason I will not hesitate to include in my review provocative speculations. I will base my discussion on Mathewson's (1968) elegant magnetic field model, consisting of a local field in the form of a sheared helix, superimposed on a large scale longitudinal field. I will include the criticism of this model by Gardner et al. (1969b). Mathewson has succeeded in accounting for such data as the distribution of background polarized radiation from the Galaxy, the distribution of rotation measures of extra-galactic radio sources and even the spurs and ridges in galactic continuum emission. There are critics who inherently distrust models that account for too many things at one time, but I feel that we should try to account for as many things as possible with the least number of models. Mathewson has succeeded in uniting much data and I will only add a few pieces to his model.
Stellar Populations in Galaxies
Authors: Van den Bergh Sidney
Published: July 2016

There are significant differences among old stellar systems which may partly be a function of luminosity. One such difference is the presence of nuclei in many high luminosity spiral galaxies but their absence in low luminosity irregular systems. Other differences are seen in the spectroscopic and photometric properties.
Gas in the Nucleus and Disk of M31
Authors: Rubin Vera C. , Ford W. Kent
Published: July 2016

Image tube spectra of emission regions in M31 have been studied to determine relative line strengths and abundances. Lines of H, He, [NII], [SII], [Oi], [Oii], [Oiii] are observed. The analysis indicates: (1) that there are ions whose line strengths, relative to Hα, are a function of the position of the emission region in M31; (2) abundance differences or different excitation mechanisms exist in regions separated by only a few hundred parsecs.
Absorption by Neutral Hydrogen in the Irregular Galaxy M82
Authors: Guélin M. , Weliachew L.
Published: July 2016

A neutral hydrogen survey of the irregular galaxy M82 has been carried out with the transit radio telescope at Nançay, France. The resolving power was 4′ in right ascension and 34′ in declination. The velocity resolution was 59 km s−1.

Drift scans covering 58′ in right ascension were taken across the center of the galaxy where the radio source is located; fourteen scans were averaged.

Line profiles were derived every 2′ in right ascension. The profiles at ±4′ from the radio source are similar within the measurement errors. In particular, they do not show any rotation effect within ±15 km s−1. They were averaged in order to provide an estimate of the expected emission profile at the radio source position.

Subtraction of this average from the line profile measured in front of the radio source yielded significant negative temperatures at all velocities from 180 to 360 km s−1 and no positive temperatures at other velocities.

These negative temperatures were assigned to absorption of the radiation from the radio source by neutral hydrogen in M82.

Absorption is running from 3 to 6% in depth. The average velocity of the absorption profile is lying between the central emission velocity and the optically-determined velocity which are known to show a large disagreement.

The width of the absorption profile shows a velocity gradient of 200 km s−1 across the 35′ × 20′ radio source. Such a large velocity spread across this angular extent is only shown by the excited gas showing emission lines at optical wavelengths (Burbidge et al., 1964).

Since then, the absorption in M82 at the neutral hydrogen wavelength has been confirmed by measurements done with the Owens Valley Radio interferometer at 2 spacings where any emission is completely resolved (interfringes were 3′ and 1′.5).

In addition to the conclusions of the single dish observations done at Nançay, the interferometer data have shown that the steeper velocity gradient occurs along the major axis of the galaxy which coincides with the major axis of the radio source.
Optical Variability of Twenty-Two Quasi-Stellar Objects
Authors: Angione R. J. , Smith H. J.
Published: July 2016

Light fluctuations have been found in all 22 QSOs studied by measurement of plates from the Harvard collection, which cover the last eighty years. The conclusions of this study are: (i) There appear to be at least three general classes of variation: (a) erratic, small-amplitude variations, (b) erratic, large-amplitude variations, and (c) slow quasi-periodic variations, e.g. as in 3C 273; (ii) No significant differences were detected between the rates of rise and decline of luminosity; (iii) Definite secular trends over at least 50 years were found in 5 QSOs; (iv) No simple clearcut periods greater than one year have been found; (v) There may be a trend of decreasing amplitude of fluctuations in apparent magnitude with increasing luminosity.
Intensity Variations in Extragalactic Radio Sources at 13 cm
Authors: Nicolson G. D.
Published: July 2016

Results of a three-year investigation into the variability of 55 Parkes sources at 13 cm are presented. Thirty-six of the sources comprise a complete sample of QSS with fluxes exceeding 2 flux units. The remaining sources include most other known or likely variables stronger than 2 flux units. The relationship between spectra and variability in QSS is investigated and it is confirmed that variables generally have flat low frequency spectra. A possible relationship between redshift and specific types of intensity variations is considered. Limits on the secular change in the intensity of non-variable QSS are set and are generally found to be ± 1.5% p.a. at 13 cm. Results for the remaining 19 sources are discussed and some preliminary findings of an extension patrol to include weaker sources in the range 1-2 flux units are given.
Variable Radio Sources: Comparison of Observations with the Adiabatic Spherical Expansion Source Model
Authors: Epstein Eugene E.
Published: July 2016

The adiabatic spherical expansion model of radio source outbursts has been applied to several outbursts in the quasi-stellar sources 3C 273 and 3C 454.3 and the Seyfert galaxies 3C 84 and 3C 120. Considering the simplicity of the model, it represents the data exceedingly well in a number of outbursts. The times of origin of the outbursts, the electron energy distribution indices, and the acceleration of the expansion parameters have been derived. Estimates of the sizes and magnetic fields of the outbursts have been made.

These results are part of a paper to be submitted to the Astrophys. J.
M87 and the X-Ray Emission from Compact Objects
Authors: Longair M. S.
Published: July 2016

M87 (Virgo A, 3C274) has been observed at 5 GHz with the Cambridge One-Mile telescope, with a resolution of 6.5 arc sec. These observations do not include the extensive halo but show that the central region of the source consists of at least three components. The central of the components is unresolved and appears to coincide with the optical nucleus, the outer pair extending from a point about 5 arc sec south of the optical nucleus. These components are unresolved perpendicular to their extension axes. The north preceding component is related to the optical jet but is more extended.
Optical Identifications of Compact Radio Sources
Authors: Pooley G. G.
Published: July 2016

A study of twelve compact radio sources whose radio spectra show pronounced peaks at centimetre wavelengths has been made using the Cambridge one-mile radio telescope operating at a frequency of 5 GHz. For each of these sources we have measured accurate positions to closer than one arc sec and determined upper limits to their angular sizes.

A search for optical identifications using the prints of the Sky Survey has revealed probable candidates for eleven of the twelve sources, an unusually high success rate. Of the suggested identifications, three are galaxies (OC 328 = 4C 31.04, VRO 20.04.02, OQ 208), and eight are possible or confirmed QSOs (NRAO 140 = 4C 32.14 = OE 355, OI 315, P 0735 + 17 = VRO 17.07.02, OI 363, OJ 287 = VRO 20.08.01, OK 290, OR 103, DA 406). Details are given by G. M. Blake, Astrophys. Letters6, 201 (1970).
Seyfert Galaxies
Authors: Lewis B. M.
Published: July 2016

The four Seyfert galaxies with systemic velocities of less than 2000 km s−1 have been observed at 21 cm with the Jodrell Bank 250-ft telescope and a 5 MHz overall bandwidth setting of the 256 channel auto-correlation spectrometer. Relatively strong signals of 0.5 f.u. are observed in NGC 1068 and 4151, while less well-determined signals of ∼ 0.25 f.u. and covering a wide velocity range are seen in both NGC 3227 and 4051. Measures of the systemic velocity, velocity width and Hi mass are obtained, the Hi mass/L being normal for galaxies of their Hubble type.
21-cm Absorption in BL Lac
Authors: Cohen M. H.
Published: July 2016

Observations with the Owens Valley Radio Observatory interferometer show that BL Lac has a 21-cm hydrogen absorption line, produced by a local intervening cloud. The line is centered on zero velocity (LSR), has a width of about 5 km s−1, and shows an optical depth of 0.5. BL Lac is at galactic latitude b= −10°. No firm distance limit is possible, but such clouds are, typically, 100 pc apart. This observation is consistent with BL Lac being an extragalactic object. Other observations leading to a similar conclusion are of rotation measure (MacLeod and Andrew, 1968) and of reddening (Bertaud et al., 1969).
The Law of Momentum Conservation and Some Problems of Metagalactic Astronomy
Authors: Shklovsky I. S.
Published: July 2016

Because of the anisotropic character of the generation of relativistic particles and synchrotron emission of active galactic nuclei and QSS it should be expected that ‘magnetoids’, the plasma bodies which are responsible for such generation, will attain large momenta. Therefore, magnetoids should be pushed out of nuclei with high velocities. This mechanism can explain several puzzling effects which are observed in the Metagalaxy, e.g. the jet in NGC 4486, connections between some galaxies and QSS and the total positive energy of some clusters of galaxies.
On the Evolution of Quasars and their Remnants
Authors: Kafka P.
Published: July 2016

The evolution of massive cores in the post-quasar phase is considered.
Analysis of the Magnitude-Redshift Relation Including Possible Effects of Evolution
Authors: Solheim Jan-Erik , Tinsley Beatrice M.
Published: July 2016

In this paper, we compare the magnitude-redshift data for brightest cluster galaxies with cosmological models of general relativity, including non-zero cosmological constant. Our study is parallel to that by Peach (1970). We use the same data but an independent method, and obtain somewhat different results. We also consider possible effects of evolution.
A Combined Cosmological Test
Authors: Solheim J.-E.
Published: July 2016

I shall report the result of a combined cosmological test, including both galaxies in clusters and blue objects of different types. The test is performed on uniform models and the result is a high density, ever expanding model.
Statistical Properties of QSOs
Authors: Braccesi A.
Published: July 2016

Counts of quasi-stellar objects selected by their optical properties imply evolutionary properties similar to those found by examining the radio-selected objects. The optical luminosity functions of the 3CR and optically-selected quasi-stellar objects are compared. Data on the radio emission and optical variability of the optically-selected sample are presented.
Redshift Distribution of Quasi-Stellar Objects and the Radio Source Counts
Authors: Petrosian Vahé
Published: July 2016

The evolution of QSOs and the reality of their apparent cutoff for z > 2.3 is determined using their large scale redshift distribution. The contributions of QSRs to radio source counts are calculated on the basis of possible evolution of QSOs having z > 2.2.
Cometary Brightness Variations and Conditions in Interplanetary Space
Authors: Andrienko D. A. , Demenko A. A. , Demenko I. M. , Zosimovich I. D.
Published: July 2016

The study of cometary brightness variations can be a good method for determining conditions in interplanetary space. In this work we compare the light curves of comets with curves showing variations in the geomagnetic field at times when the comets are near the ecliptic plane. We have used photometric observations made of 29 comets between 1881 and 1937. It is shown that an increase in the brightness of a comet is associated with an increase in the geomagnetic activity index and consequently with the influence of the solar corpuscular streams and solar wind.
A Library of Standard Programmes for Constructing Numerical Theories for Studying the Motion and Evolution of the Orbits of the Minor Bodies of the Solar System
Authors: Bokhan N. A.
Published: July 2016

At the Institute for Theoretical Astronomy we have formed a library containing about 120 standard computer programmes. They include calculation of rectangular coordinates and velocities from elements, Lagrangian interpolation, and orbit improvement by the Eckert-Brouwer method. For the investigation of the motions of the minor bodies of the solar system we have constructed a programme for integration with a variable step and making allowance for perturbations by all the major planets and for nongravitational effects. The calculation of the perturbations is carried out using Herrick's vector parameters by the method of variation of arbitrary constants. The programme has been used for studying the motion of P/Encke.
A Method of Integrating the Equations of Motion in Special Coordinates and the Elimination of a Discontinuity in the Theory of the Motion of Periodic Comet Wolf
Authors: Kazimirchak-Polonskaya E. I.
Published: July 2016

From the integration formulae of Numerov and Subbotin we have developed and programmed for an electronic computer a particular method for integrating the differential equations of cometary motion in special rectangular coordinates, with a variable step and allowing for all planetary perturbations and nongravitational effects over a time interval of 400 yr. Application of this method and our set of programmes to the investigation of the motion of P/Wolf permits us to eliminate the discontinuity that has hitherto existed in the theory on account of the comet's close approach to Jupiter in 1922.
The Motion of Halley's Comet from 837 to 1910
Authors: Brady J. L.
Published: July 2016

Numerical experiments have been made in an attempt to remove the residuals of P/Halley and link the seven apparitions from 1456 to 1910. All efforts to link more than two apparitions using Newtonian equations have invariably failed. However, by the addition of a secular term to the equations of motion, the four apparitions from 1910 back to 1682 can be linked by a numerical integration which represents the observations to contemporary accuracy. When this integration is continued, the apparitions of 1607, 1531, and 1456 show residuals of less than one day in the time of perihelion passage. Prior to 1456 the residuals begin to run off but, with the exception of 1222 and 1066, the apparitions back to 837 show residuals no greater than four days in the time of perihelion passage. The residuals of 20 days in 1222 and 7 days in 1066 appear anomalous but can be made reasonable if the Chinese records are adopted in preference to the European records.
A Model for the Nucleus of Encke's Comet
Authors: Sekanina Z.
Published: July 2016

A study of the nongravitational deviations in the motion of P/Encke suggests that the nucleus of this comet can conceivably be approximated by a core-mantle model, composed of a porous solid core with embedded ices, surrounded by a thick envelope of free ices that gradually sublimates out.
On the Stability of the Oort Cloud
Authors: Nezhinskij E. M.
Published: July 2016

An attempt has been made to estimate the rate of destruction of the Oort cloud by stars passing through it. Two different mechanisms of cloud dispersion have been investigated. Numerical estimates show that the cumulative dispersing mechanism plays the leading role. The lower limit for the half-life of the cloud is 1.1 × 109 yr.
Evolution of the Orbits of Selected Minor Planets during an Interval of 1000 Years
Authors: Dirikis M. A.
Published: July 2016

The long-term evolution of the orbits of 944 Hidalgo, 1036 Ganymed and 1134 Kepler is investigated.
Searches for γ-Rays from the Crab Nebula and its Pulsar
Authors: Jelley J. V.
Published: July 2016

The Crab Nebula has been regarded as the most promising celestial object to investigate for the detection of γ-rays. γ-ray emission might be expected from either the synchrotron or the inverse Compton mechanism. Periodic γ-ray emission could come from the pulsar, but no theory has yet been developed for such objects. Searches for γ-rays from both the Crab Nebula and the Crab pulsar made by a number of groups are described. Limits have been set to the γ-ray emission from both objects which are only a little above the extrapolated optical and X-ray fluxes.
Investigation of Coronal Rotation by the Spectroscopic Method
Authors: Stepanov V. E. , Tjagun N. F.
Published: July 2016

Coronal rotation is different in the northern and southern hemispheres of the Sun and varies with the cycle of solar activity. A sharp decrease in linear velocity by 0.4 km s−1on the latitude and its relative constancy in the latitude interval 35° < φ < 50° are the most typical.

In the southern polar region an intensive stream of coronal gas directed oppositely to the solar rotation was detected during the time interval 1969–1972. In the greater part of the latitude range, on average, the corona rotates more slowly in comparison with the solar atmosphere at the photospheric level.
Characteristic Features of Cyclic Change of Solar Activity after 1610
Authors: Bonov A. D.
Published: July 2016

The most characteristic feature of the solar activity is its cyclic change in the course of time. The basic cycle is the 11-year one.
Theory of Convection in a Deep Rotating Spherical Shell, and Its Application to the Sun
Authors: Gilman Peter A.
Published: July 2016

The theory of convection in a rotating spherical shell, when applied to the Sun, should ultimately satisfy at least three broad constraints. The radial heat flux by the convection must not vary significantly with latitude; an equatorial acceleration must be produced; and the convection must give the right dynamo action to produce the gross features of a solar cycle.

Important quantities to look for in the observations with which a convection theory can be compared include evidence of global velocities of giant convection cells, differences in motion features between low latitudes and high, persistence of motion features over successive rotations, evidence of excess brightness and variations in total solar luminosity, correlations of velocities between northern and southern hemispheres, and between north-south and east-west motions, and time periodic changes in motion fields.

The general theory of convective motions in a rotating spherical shell such as the convection zone of the Sun has developed rapidly over the last several years, but is still a long way from providing quantitative models which agree in a satisfactory way with the main solar observations. Most work has (for mathematical reasons) employed the Boussinesq approximation, and most has been either linear or nearly so. Early work demonstrated the basic ability of global convection to transport momentum toward the equator, but whether an equatorial acceleration results depends on the effects of competing angular momentum transport processes, namely transport in the radial direction by convection, and transport by axisymmetric meridional circulations. The end result can be assessed only by nonlinear calculations.

Some recent calculations directed at this question by the author indicate that, at least at Prandtl number of unity, convection growing from an initial state of solid rotation produces equatorial acceleration only when equatorial modes dominate and the rotational constraint is sufficiently strong, which results in a convective heat flux which is strongly dependent on latitude. When the rotational constraint is broken enough to give convection at all latitudes and therefore more nearly uniform heat flux, equatorial deceleration and angular momentum mixing in latitude results. A few calculations for Prandtl number substantially smaller than one give results which suggest it is possible to produce equatorial acceleration and nearly uniform heat flux, but these solutions appear not to be unique. In particular, the amount of differential rotation present in the initial conditions appears to be important in determining the final state.
Mean-Field Magnetohydrodynamics of the Solar Convection Zone
Authors: Krause F.
Published: July 2016

Observations of the solar surface show that some of the physical quantities, especially the velocity field and the magnetic field, show random character.
Welcome to W. W. Morgan
Authors: Strömgren B.
Published: July 2016

It is a great privilege to have the opportunity to welcome William Morgan to the IAU Symposium that has been opened today.
Abundance Effects on uvby Photometry
Authors: Crawford D. L. , Perry C. L.
Published: July 2016

Abundance differences from one star to another cause differences in the observed parameters of the Strömgren four-colour system. The major effect is on the m1 parameter, of course.

This paper describes these effects on the parameters.
Recent Results Pertaining to the Helium-Rich Stars
Authors: Walborn N. R.
Published: July 2016

The term helium-rich stars here refers to those stars with apparent spectral types near B2 ana helium lines which are enhanced, but not stronger than the hydrogen lines. The previously known helium-rich star HD 184927 has been found to be a spectrum variable; the equivalent widths of the helium lines changed by an average of 46% between two observations. HD 186205 has been newly recognized as a member of the helium-rich class. Further work toward understanding the rapidly variable Ha emission in the prototype helium-rich star, Sigma Orionis E, is in progress in co-operation with Dr J. E. Hesser at CTIO.
Abundance Effects in Spectral Classification
Authors: Jaschek C.
Published: July 2016

The paper attempts to put together the spectroscopic definitions used in the literature for different groups of peculiar objects linked with abundance anomalies.

The groups discussed are:

O-type subdwarfs

CNO stars

He-strong stars

He-weak stars

B-type subdwarfs

Ap stars

Am stars

λ Boo stars

δ Del stars

Fm stars

A-F-G stars with weak metal lines

Stars with CN anomalies

Stars with CH anomalies

Ba stars

In each case the useful range in dispersion is quoted and bibliographic references are provided.
Effects of Heavy-Element Abundance on Classification of G-Type Giants
Authors: Keenan P. C.
Published: July 2016

Five stars, including ζ Cyg, which had been classified as G6 II to G8 II bright giants, were found by O. C. Wilson to have K-line luminosities close to those of class III giants. These stars show enhancement of the lines of Ba II and other heavy-metal ions also. To eliminate the serious effect of this abundance anomaly on the spectroscopic luminosities new luminosity criteria involving only intercomparisons of lines of elements of the fourth period (Ti, Fe, etc.) were applied on 9 Å mm−1 Coudé spectrograms taken by O. C. Wilson. This Coudé classification gave luminosity classes near IIIa for these stars, implying absolute magnitudes considerably below those of bright giants but somewhat above Wilson's MK values.

Another advantage of Coudé classification is the possibility of estimating luminosities for individual barium stars. From Wilson's plate of HD 205011 a luminosity class of III-IIIa is derived. This is consistent with the mean value of Mv = −0.4 derived from statistical parallaxes by MacConnell, Frye and Upgren (Astron. J. 77, (1972), 384) for the barium stars.

The detailed account of this investigation will be published elsewhere.
Can We Check by High-Dispersion Analyses Stars Belonging to Eggen's Moving Groups?
Authors: Pasinetti L. E.
Published: July 2016

We describe the results of analysis of the giant star HD 6497, which belongs to the Arcturus group.
Spectral Classification of B and A Stars from Data of S2/S68 Experiment
Authors: Cucchiaro A. , Jaschek M. , Jaschek C. , Macau-Hercot D.
Published: July 2016

The S2/S68 experiment on the satellite TD1A has supplied, in the wavelength region of 1350 Å to 2550 Å, a very large number of spectra of early stars.

A statistical study, as well as a general analysis of these spectra, has been carried out in order to establish criteria relative to the spectral region envisaged and independent of any previous study in the visible. On the basis of these criteria a system of classification has been outlined.

In a first stage, the spectra of stars visually classed from B0 to A5 have been considered. From four sets of spectrophotometric criteria a two-dimensional ultraviolet classification has been derived.
Molecules in astrophysics half a century ago
Authors: van de Hulst H. C.
Published: July 2016

I feel a bit embarrassed to be talking about things which happened before most of you were born. But this is what Ewine asked me to do.
High angular resolution observations of the gas phase composition of young stellar objects
Authors: Blake Geoffrey A.
Published: July 2016

Recent advances in the observational characterization of young stellar objects (YSOs) with millimeter-wave aperture synthesis arrays and (sub)millimeter single dish telescopes are reviewed. Studies of circumstellar material with ∼arc second resolution, which have only become possible at these frequencies within the past few years and which can potentially probe all stages of the star formation process, are emphasized. Molecules that are sensitive to different routes of formation and modification are outlined, including comments about their utility in distinguishing between a variety of environments and histories in star-forming cloud cores.
In Memoriam: Sheldon Green
Authors: Flower David
Published: July 2016

Many of you will know that Sheldon Green died suddenly, towards the end of 1995. When Ewine asked me to say a few words at this meeting, in Sheldon's memory, I thought it very appropriate to do so and did not hesitate to agree. Although several people here probably knew Sheldon personally better than I (because our careers evolved on opposite sides of the Atlantic), it is possible that no-one present is more familiar with his published work.
Dynamics of chemical reactions of astrophysical interest
Authors: Alagia M. , Balucani N. , Cartechini L. , Casavecchia P. , Volpi G.G.
Published: July 2016

The dynamics of the astrophysically relevant reactions OH + H2,OH+CO,N(2D)+C2H2 and O(1D)+H2 are studied using the crossed beam scattering technique. Comparisons of the experimental results with those of dynamics calculations on ab initio and semi-empirical potential energy surfaces are discussed.
Laboratory simulation of physical and chemical processes in interstellar ices
Authors: Schutte W.A.
Published: July 2016

We review the techniques which are applied to study by means of laboratory simulation the chemical and physical processes taking place in ices in interstellar dense clouds. We summarize the current situation with regard to spectroscopy of interstellar ice analogs and with regard to the simulation of chemical processes such as modification of the ices by UV photons and surface reactions between reactive atoms and molecules. It is discussed how such data can be used to explore the potential of the icy mantles both as a record of the various chemical conditions that occur in dense clouds and as an environment for unique interstellar chemical processes.
First detection of thermal H2O Emission from a Herbig-Haro Object
Authors: Liseau R. ,   The LWS Consortium
Published: July 2016

The first detection of thermal H2O emission from an Herbig-Haro flow was made with the LWS (Long Wavelength Spectrometer) aboard ISO (Infrared Space Observatory). In addition to H2O, rotational lines of CO and OH as well as lines from [O I] and [C II] were also recorded from HH 54. These observations are consistent with the concept of interstellar shock waves, but a quantitative unifying shock model, capable of explaining all observations, has yet to be developed.
CO detection in the quasar BR1202-0725 at z = 4.69
Authors: Omont A. , Petitjean P. , Guilloteau S. , McMahon R.G. , Solomon P.M. , Pecontal E.
Published: July 2016

The number of identified high-redshift far-infrared hyperluminous sources (LFIR ≥ 1013L⊙) is now approaching ~20 (see e.g. Rowan-Robinson 1996). In about half of them, at z > 3.5, evidence for strong far-infrared emission has been obtained from its redshifted detection in the mm continuum. Most of the latter are bright radio-quiet QSOs (Omont et al. 1996b). The most prominent one, BR1202-0725 at z = 4.7, was first detected at 1.25mm with the IRAM 30m telescope (McMahon et al. 1994) with a flux of ∼ 10-15 mJy. Its submm detection at JCMT (Isaak et al. 1994) supports dust emission because of a submm-mm spectral index ≥ 3.
Solar Neighborhood Flare Stars – a Review
Authors: Kunkel W. E.
Published: July 2016

Since Gershberg's (1970a) very thorough review of the subject, numerous papers dealing with the collective properties of flare stars have appeared (Petit, 1970; Kunkel, 1970d, 1973; Ambartsumian and Mirzoyan, 1971; Gurzadyan, 1971; Oskanian and Terebizh, 1971a, b; Gershberg, 1972; Veeder, 1973). The basic features of flare activity can be taken as known, then.
An Observational Approach to Stellar Evolution (Flare Stars and Related Objects)
Authors: Haro Guillermo
Published: July 2016

Flare stars in the solar neighborhood and in associations belong to the same class of objects but might represent different evolutionary stages. In this report, fundamental contributions, based on observations by various groups, on flare stars ranging from extremely young ones to dMe flare stars are summarized.
On Variations in the Flare Activity of V 1054 Oph
Authors: Kunkel W. E.
Published: July 2016

Four years ago I examined the flare incidence data then available for UV Ceti and V1054 OPH (Wolf 630) and concluded that no evidence could be found for periodic or secular variation in the levels of activity (Kunkel, 1971). Variations greater than 0.3 mag. (rms) should have been found.
A Possible Mechanism of Stellar Flares
Authors: Vandakurov Yu. V.
Published: July 2016

Magnetohydrodynamic considerations on the origin of stellar flares.
Comparison of UV Ceti Flares with Solar Flares
Authors: Haupt W. , Schlosser W.
Published: July 2016

During several intervals totalling 26 h, 84 flares of UV Ceti were observed using a photometer with 1 s time resolution. Using solar flare terminology, all flares of UV Ceti observed here can be characterized by a typical light curve, consisting of a preflare, a flash and a slow phase. Observations of Bopp and Moffett (1973) show that the flash phase of UV Ceti is dominated by continuous and Hα emission. UV Ceti flare flash phases are compared with solar ‘white-light’ emission during the flash phase and it is suggested that during all UV Ceti flares strong-particle emission occurs, as is the case for solar white-light flares (Švestka, 1970). The characteristics of the solar flare particles are similar to those of the soft cosmic ray sources (Mogro-Campero and Simpson, 1972). If all flare stars emit particles with these characteristics they could produce the soft cosmic ray component in agreement with the work of Comstock (1969).
Circumstellar Dust Shells
Authors: Shulman L. M.
Published: July 2016

The optical properties of circumstellar graphite particle shells are considered. In the case of the optically thin shell (e.g. the shell of a RCB star after minimum), the temperature of the grains is calculated. It is shown that the dust shell always has a sharp inner border. The RCB phenomenon may be considered as a sudden moving of this border toward the star and the consequent increase in its optical thickness.
On the Presence of Variable Stars in Open Clusters
Authors: Popova M.
Published: July 2016

The significance of variable stars as members of open clusters is outlined. The results of a search for such stars are briefly mentioned.
On Spectral Observations of ζ Gem
Authors: Shcherbakov A.G.
Published: July 2016

I want to show two slides with the evidence of the presence of the λ 10830 Å HeI absorption line in the spectrum of the classical Cepheid ζ Gem. In Figure 1 you can see the profile of the blend near λ 10830 å (dispersion 48 Å mm−1); this blend consists of lines of neutral silicon, helium and atmospheric water. The monotonous phase changes of the profile are easily seen.
The Mass and Evolutionary Status of AI Vel-Type Variables
Authors: Dziembowski W.
Published: July 2016

Arguments are presented that the AI Velorum variables are about 0.2 M⊙ objects evolving with a roughly constant luminosity toward the white dwarf stage.
New Data on the δ Scuti Star 44 Tauri
Authors: Morguleff N. , Oskanian V. , Rutily B. , Terzan A.
Published: July 2016

Photometric and spectroscopic observations were made by Oskanian and Terzan (1974) on the 40-cm telescope at Byurakan Observatory and by Morguleffet al.simultaneously at the 80-cm photometric telescope and the Coudé Spectrograph of the 152-cm telescope of the Observatoire de Haute Provence.
Towards a Realistic Model for Nova Envelopes
Authors: Friedjung M.
Published: July 2016

Arguments are given, suggesting that the most probable type of model is one in which ejection continues after maximum light in the visual region, but with rapid time variations.
On the Origin of Nova-Like Binary Systems
Authors: Gorbatsky V. G.
Published: July 2016

Basic physical characteristics of nova-like binary systems are similar to W UMa systems. Externally, however, these systems are different – nova-like systems contain a white dwarf as a component, whereas both components of W UMa systems are near the main sequence. The hypothesis is suggested of the origin of contact W UMa systems by means of the fission of the rapidly rotating isothermal helium core of an evolved giant star. The contraction of the more massive component leads to the formation of a white dwarf and consequently to the transformation of a W UMa type system to a nova-like system.

Submitted to Astrophysics and Space Science.