bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of International Legal Rules for the Repression of the Unlawful Seizure of Aircraft
Authors: FitzGerald Gerald F.
Published: June 2019

The dramatic increase in the number of incidents of unlawful seizure of aircraft during 1968 and the first few months of 1969 has posed one of the most difficult problems ever faced by the international aviation community. The purpose of this note is to examine the existing state of the law governing the unlawful seizure of aircraft, discuss the efforts of air lawyers to attack the problem from the legal point of view, examine proposed legal solutions put forward in ICAO in the last half of 1968 and early 1969, and indicate the extent to which acceptable legal solutions may be found. As will be seen, although the Convention on Offences and Certain Other Acts Committed on Board Aircraft contains a number of provisions on the unlawful seizure of aircraft, it by no means provides solutions for all existing problems.
The Organization of African Unity and the United Nations: A Study of the Problems of Universal-Regional Relationship in the Organization and Maintenance of International Peace and Security
Authors: Akindele R. A.
Published: June 2019

World peace, like war, has tended to become indivisible. Nonetheless, the formal organization of international peace and security continues to be anchored to the principle of division and imperfect co-ordination of responsibility between universal and regional instrumentalities. The problem of maintaining world peace would probably have been much less troublesome than it is now if the international system had either been hierarchically organized, or based upon a strictly federal foundation. Needless to say, the global system remains largely a semi-primitive political order characterized, as it is, by a decentralized structure of power configuration.
Execution of Foreign Commercial Awards in Post-War Soviet Bilateral Treaty Practice
Authors: Ginsburgs George
Published: June 2019

In 1945, H. J. Hilton, Jr., published an excellent article in the Department of State Bulletin entitled “Commercial Arbitration in the Treaties and Agreements of the U.S.S.R.” which assessed the Soviet record in this area up to the end of the Second World War. The purpose of the present study is to carry the inquiry forward to the present, concentrating, however, exclusively on the problem of execution of foreign commercial arbitral awards in Soviet bilateral treaty practice during this period.

Before proceeding though, a quick review of the salient points of Mr. Hilton’s survey will furnish useful background information.

First, in analyzing the corpus of Soviet treaties and agreements that feature statements concerning arbitration of commercial disputes, the author found that, while the relevant provisions ranged in detail from a single phrase to comprehensive conventions containing as many as 15 articles, the data did not reveal a pattern of historic evolution in the type of formulas regarding arbitration. In other words, although the Soviet regime passed through several phases of development between 1921, when such a reference initially appeared in a treaty signed by the R.S.F.S.R., and 1945, this did not entail technical changes reflecting specific policy shifts; the various approaches used recur throughout the span of observation without any determinable regularity and no correlation could be fixed between the choice of a particular solution and the prevailing conditions at home or abroad at a given juncture. The conclusion here, then, was that “the provisions referring to arbitration included in the treaties and agreements of the U.S.S.R. vary considerably in content; however, these variations cannot be established precisely by periods of time.”
Mediation, Conciliation and Adjudication in the Settlement of International Drainage Basin Disputes
Authors: Bourne C. B.
Published: June 2019

When States Disagree about the way in which the waters of an international drainage basin should be utilized, they should try first to resolve their differences by consultation and negotiation. This is what they usually do and, for the most part, do successfully. Sometimes, however, their negotiations do not lead to agreement. They then face the question whether or not they should involve the aid of third-parties in resolving their problem. In the words of Article 33 of the Charter of the United Nations, must they “seek a solution by … mediation, conciliation, arbitration, judicial settlement, resort to regional agencies or arrangements, or other peaceful means of their own choice”?

It is proposed to examine here the obligation of states to resort to mediation, conciliation and adjudication when they cannot otherwise settle a dispute about the development of an international drainage basin that they share.
The Convention on the Law Applicable to Traffic Accidents
Authors: Fischer Hugo
Published: June 2019

On October 26, 1968, the delegates to the Eleventh Session of The Hague Conference on Private International Law decided to submit, for consideration by their respective governments, a draft Convention on the law applicable to traffic accidents. Article 14 of the Convention permits ratification by a country which, like Canada, has a non-unified legal system, if the Convention has been extended to at least one of its jurisdictions. The Convention aims at uniformity in a branch of the law where, until now, to quote an eminent jurist, “case-to-case decisions [did] not add up to a system of justice.”

Under Canadian constitutional law the implementation of the Convention requires provincial legislation. At the invitation of the government of Canada a delegate of the Conference of Commissioners on Uniformity of Legislation in Canada participated at the session in The Hague as a member of the Canadian delegation.
Towards an International Convention on the Registration of Space Objects: The Gestation Process
Authors: Dalfen Charles
Published: June 2019

Under most legal jurisdictions, motorized vehicles operating on land, in the air and on water are subject to registration. The effective management of traffic, the enforcement of standards of safety and the imputation of liability for damage all require that the parties responsible for the conduct of particular vehicles be identifiable. This identification function is normally provided for by means of a registration system.

Typically, a registration system comprises two elements — characteristic markings on each vehicle operating within the jurisdiction, and a register which lists the vehicles by their markings along with the parties legally responsible for them. The system is underpinned by obligations on the responsible persons — usually the owners — to register and mark their vehicles, and on the state to maintain appropriate registers.

As between jurisdictions there are frequently bilateral and sometimes multilateral agreements providing for reciprocal access to these registers under certain conditions.
La Troisième Conférence sur le droit de la mer et le règlement obligatoire des différends
Authors: Lehoux Gregoire
Published: June 2019

A la premiere Conférence des Nations Unies sur le droit de la mer, qui a abouti à la rédaction des quatre Conventions de 1958, les Etats participants se sont d’abord et avant tout attachés à la codification des règles coutumières du droit de la mer. Comme c’est malheureusement trop souvent le cas lors de ces négociations internationales, on s’est peu préoccupé de la question du règlement des différends. Ainsi, un système de règlement obligatoire des différends n’a été prévu que pour les pêcheries en haute mer. De plus, ce système n’a été accepté que par environ trente Etats et, surtout, il n’a jamais été utilisé. Pour ce qui est des différends pouvant résulter de l’interprétation et de l’application des autres conventions de 1958, on n’a préparé qu’un protocole facultatif qui conférait juridiction à la Cour internationale de justice. Les signataires de ce protocole furent d’ailleurs très peu nombreux, moins de quarante en fait; et, parmi ceux-ci, ne figurent ni les Etats-Unis, ni l’U.R.S.S., deux pays qui s’opposaient au règlement obligatoire des différends à ce momentlà.
Canada’s Role in the Development of the Law of Armed Conflict
Authors: Green L.C.
Published: June 2019

Perhaps the most important contribution made by Canada to the development of armed conflict law, and one that is possibly equal in significance to that made by any other country, was not in fact made by Canada as such, but rather in response to Canadian actions. During the 1837 rebellion, Canadian forces had seized an American vessel, The Caroline, which had been used to support the rebels, and tipped it over Niagara Falls. In response to United States protests, the Canadian authorities justified their action on the ground of self-defence. In negotiations with the British, who then governed Canada, Daniel Webster, United States Secretary of State, propounded a formulation of the plea of self-defence which has stood the test of time. In his words, preventive action in foreign territory is only justified in the case of “an instant and overwhelming necessity for self-defence, leaving no choice of means, and no moment of deliberation.” This concept of the right is so universally accepted today that it was adopted in its Judgment by the International Military Tribunal at Nuremberg when rejecting Germany’s explanations of the invasions of Denmark and Norway.
Derogation of Human Rights in Emergency Situations
Authors: Green L. C.
Published: June 2019

Since Mr. Carter became President of the United States, there bas been a revival in the use of human rights as a weapon in international politics. More and more western countries have stated that they are contemplating measuring the aid they give to members of the developing world in proportion to the extent to which the latter conform to basic humanitarian standards or improve their own record in relation to observance of human rights. In addition, there have been calls for the cancellation of visits by politicians, academics, and artistic performers; for non-participation in international athletic contests — a western adaptation of the African ban of the Montreal Olympic Games because of New Zealand’s participation while the latter’s athletes were not barred from competing in South Africa; for non-participation in technical and scientific conferences; and for the breaking of town-twinning arrangements. This attitude has been fed somewhat by reason of the activities of “Helsinki watchers,” who contend that this or that country, and particularly the Soviet Union, is not living up to its human rights obligations as embodied in the Helsinki Agreement.
The Permanent Court of Arbitration and the Election of Members of the International Court of Justice
Authors: Copithorne M. D.
Published: June 2019

The Hague Conference of 1899 was the first to address the need for a permanent body for the settlement of differences between states. The ensuing Convention for the Pacific Settlement of International Disputes entered into force in 1900. At the second Hague Conference in 1907 the provisions of the 1899 Convention were expanded in a new convention of the same title which entered into force in 1910. These conventions established the Permanent Court of Arbitration, which in reality is neither “permanent” nor a “court” but rather a panel of persons, up to four being named by each participating state, from which arbitrators can be selected.
Organisation des Etats américains, Comité juridique interaméricain : 5ième Séminaire de Droit international, Rio de Janeiro, 6 août - 1er septembre 1978
Authors: Hubert Jean-Paul
Published: June 2019

Le comite juridique interaméricain (CJI) de l’Organisation des Etats américains a tenu son 5ième Séminaire de Droit international à Rio de Janeiro entre les 6 août et 1er septembre 1978. Le CJI a justement son siège à Rio.

Le CJI admet deux catégories de participants à son Séminaire annuel: des boursiers, dont la candidature doit être soumise à l’OEA par les gouvernements des états-membres, et des auditeurs libres, admis par le Directeur du cours sur demande formulée auprès du Secrétariat général de l’OEA à Washington. Il n’y a pas de frais d’inscription. Pour la session de 1978, 27 bourses avaient été accordées, à des représentants de 19 pays de l’hémisphère. De plus, 17 auditeurs en provenance de 5 pays (dont le Canada) avaient reçu autorisation de participer.
Time Variability of the Dispersion of the Crab Nebula Pulsar
Authors: Rankin J. M. , Roberts J. A.
Published: June 2019

The dispersion of the Crab nebula pulsar was measured as a function of time from 10 May 1969 to 24 July 1970. Transient events occurred in the middle of June each year which coincided with the occultation of the pulsar by the solar corona. In addition there were 2 or 3 distinct events which produced enhancements of several times 1016 electrons cm-2; these were characterized by rise times of about 50 days and decay times several times longer. One event correlated with the frejump of the pulsar at the end of September 1969 and with the observation of optical activity in the quency nebula. A discussion is given of the interpretation of the variations in dispersion measure.
Faraday Rotation of the Crab Pulsar Radiation
Authors: Manchester R. N.
Published: June 2019

During April, 1970, the 300-ft telescope of the National Radio Astronomy Observatory was used to determine the mean polarisation of the Crab Nebula pulsar radiation at several frequencies around 400 MHz. The position angle of the highly polarised precursor measured at each frequency, corrected for ionospheric Faraday rotation and plotted against inverse frequency squared is shown in Figure 1. The observed variation of the position angle with frequency is consistent with Faraday rotation of the plane of polarisation with a rotation measure of −40.5 ± 4.5 rad/m2. This value is of the same sign but larger than the rotation measure for the nebular radiation in the vicinity of the pulsar.
Results of Optical Timing Measurements of the Crab Nebula Pulsar
Authors: Papaliolios C. , Carleton N. P. , Horowitz P.
Published: June 2019

Absolute time of arrival measurements were made of the optical pulses from the Crab pulsar between September 1969 and April 1970; they were corrected to the solar system barycentre. The fit to the timing data indicates that the slowdown is due to magnetic dipole radiation, but there are significant deviations indicating the presence of small fluctuations and major jumps. There is no evidence of the quasi-sinusoidal behaviour reported by Arecibo. These measurements allowed an integrated light curve to be constructed with high precision.
Measurement of the Circular Polarization of Pulsar NP 0532
Authors: Angel J. R. P. , Hegyi D. , Landstreet J. D.
Published: June 2019

The polarizer is briefly described. The polarization of the whole pulse is not significantly different from zero (-0.15 ± 0.70 per cent). Polarization measurements of the leading edge and trailing edge of the main pulse are also given.
Search for Pulsed High Energy Gamma Radiation from NP 0532
Authors: Fazio G. , Hearn D. , Helmken H. , Rieke G. , Weekes T. , Chaffe F.
Published: June 2019

During winter 1969 the 10 m optical reflector at Mt. Hopkins, Arizona, was used to search for periodic gamma ray emission above 1011 eV from NP 0532. Based on predicted optical period and phase, approximately 57 h of data were summed together. No evidence of pulsed radiation was found.
Observations of Pulsar Spectra
Authors: Ewing M. S. , Batchelor R. A. , Friefeld R. , Price R. M. , Staelin D. H.
Published: June 2019

The observed width of spectral features in CP 0328, CP 0834, and CP 1919 are approxmately proportional to the fourth power of frequency, thus supporting the hypothesis that the slow spectral variations of these pulsars are due to interstellar scintillation. The spectral features in CP 0834, CP 1133, and CP 1919 are observed to drift systematically at rates compatible with a simple interstellar scintillation model. Pulsar velocities of ~ 100 km sec-1 are inferred from these spectral drift rates.
Crab Pulsar Radiation Characteristics
Authors: Manchester R. N.
Published: June 2019

It has been suggested that for the Crab pulsar the radio radiation mechanism may be different from that in other pulsars. The principal observations leading to this suggestion are, firstly, the essentially constant position angle of the highly linearly polarised precursor, and secondly, the occasional large increases in intensity of the main pulse.
Optical Pulsar in NGC 4254
Authors: Feldman P. A.
Published: June 2019

Dr. Feldman described the optical variability which has been seen over the years in a region near the nucleus of NGC 4254 (M99) and he suggested that it might be a pulsar.
Radio Emission from Supernova Remnants
Authors: Milne D. K.
Published: June 2019

Observations of the radio emission from supernova remnants are reviewed with emphasis on the dissimilarity between the Crab Nebula and the other remnants. From this we conclude that there may be several non-thermal sources in the Galaxy with the same centrally filled structure as the Crab. These are, however, more evolved, and clearly there is no other source of the same age and type as the Crab Nebula.
Pulsars and Close Binary Systems
Authors: Trimble Virginia , Rees Martin
Published: June 2019

It is first considered what must happen if pulsars (i.e. neutron stars) are formed in close binary systems (CBS), and whether the resulting orbital motion and mass transfer should be observable. As this set of alternatives seems unlikely, there follow suggestions of how one might prevent the formation of neutron stars in close binaries. Finally, it is shown that ‘runaway’ pulsars with velocities larger than about 15 km/sec cannot be produced by isotropic supernova explosions within close binaries, and an alternative explanation is suggested for the observed correlation of periods of pulsars with their distances from the galactic plane.
Plasma Interactions in the Crab Nebula
Authors: Kahn F. D.
Published: June 2019

Alfvén waves can be carried by the thermal plasma in the Crab Nebula. Each such wave perturbs the relativistic plasma present, in particular it strongly affects those particles which are in resonance with it. For a wave travelling parallel to the magnetic field the resonances are quite simple, but a wave travelling obliquely can give rise to multiple resonances, and can therefore couple together particles with quite different energies.

It is shown that the interaction with the relativistic plasma leads to an amplification of the Alfvén waves when the mean velocity of relativistic plasma relative to the thermal plasma exceeds the Alfvén speed. The rise time for the instability is quite short, and the waves, once excited, are highly effective in redistributing the directions of motion of the relativistic particles. The relativistic plasma therefore cannot stream freely through the thermal plasma. On the other hand the disturbances will never quite die out in the Crab Nebula as long as the Crab pulsar keeps injecting fresh plasma, and thus keeps producing new inhomogeneities in the relativistic plasma density.
The Effects of Nuclear Forces on the Maximum Mass Limit of Neutron Stars
Authors: Tsuruta Sachiko
Published: June 2019

The original models of neutron stars must be improved by including effects of nuclear interaction. This paper compares the models reached by various groups, and presents an improved model by the Kyoto group. The maximum mass varies between 0.2 M⊙ and 3 M⊙ in the various models. The Vγ model is recommended for use in the absence of further information on the equation of state at high densities.
Pulsar Models and Radiation Properties
Authors: Radhakrishnan V.
Published: June 2019

Dr. Radhakrishnan outlined a geometrical theory of a rotating pattern of field lines, which would account for the pattern of polarisation observed in the integrated radio pulses from pulsars.
Low-Frequency Cutoffs in Synchrotron Spectra and the Optical Spectrum of NP 0532
Authors: O'Dell Stephen L. , Sartori L.
Published: June 2019

We point out the existence of a natural low-frequency cutoff in the spectrum of a synchrotron source. The turnover frequency is eB/mc 〈sin Ψ〉, where Ψ is the pitch angle for the electron motion. The spectrum below the turnover goes as vn, where n is the index in the electron energy distribution. For the Crab pulsar, a model with B ~ 106–107G and 〈sin Ψ〉 ~ 10-3–10-2 provides a plausible explanation for the turnover observed in the infrared.
Pulsar (and X-Star) Emission from the Magnetosphere of a Collapsed Star
Authors: Coppi Bruno , Ferrari Attilio
Published: June 2019

We propose nonthermal plasma mechanisms to account for the most evident physical characteristics of pulsar emission, including the production of X- and γ-rays and the acceleration of high-energy particles. Special reference to the Crab Nebula pulsar (NP 0532) is made and an application of the same model to other non-thermal X-ray sources is suggested.
Preface
Authors: Maeder André , Renzini Alvio
Published: June 2019

“If simple perfect laws uniquely rule the universe, should not pure thought be capable of uncovering this perfect set of laws without having to lean on the crutches of tediously assembled observations? True, the laws to be discovered may be perfect, but the human brain is not. Left on its own, it is prone to stray, as many past examples sadly prove. In fact, we have missed few chances to err until new data freshly gleaned from nature set us right again for the next steps. Thus pillars rather than crutches are the observations on which we base our theories; and for the theory of stellar evolution these pillars must be there before we can get far on the right track.”
Some investigations about the Carson opacities
Authors: Cox Arthur N. , Kidman Russell B.
Published: June 2019

Accurate opacities for stellar composition mixtures are needed for all studies of stellar structure, evolution, stability, and pulsation. In several cases it appears that larger opacities in the range of temperature near one million kelvin would assist is resolving some current discrepancies between observations of stars and some theoretical predictions. Opacities published by Carson, Mayers, and Stibbs (1968) and more recently modified and available informally, have this larger opacity in this temperature region compared to the widely used Los Alamos opacities. See the tables of Cox and Stewart (1965, 1970ab) and Cox and Tabor (1976). It is therefore of great interest to see if the actual cause of the differences between these two sets of opacities can be found and discussed.
X-ray survey of the pleiades: dependence of X-ray luminosity on stellar age
Authors: Micela G. , Sciortino S. , Serio S. , Vaiana G.S. , Golub L. , Harnden F.R. , Rosner R.
Published: June 2019

The study of X-ray emission of stellar clusters, allows to decouple the influence of some individual stellar parameters, as initial conditions, composition and age, on the stellar X-ray luminosity function.
The log L/log Te diagram for intermediate mass pop I red giants
Authors: Grenon M. , Mermilliod J.C.
Published: June 2019

The best empirical evolutionary tracks are provided by open cluster HR diagrams. The scarcity of giants in young clusters implies that diagrams of clusters having similar ages and metallicities have to be summed. Using UBV data, Mermilliod (1981a) has divided the nearby open clusters into 14 age groups, and has described the properties of the composite diagrams MV/(B-V) and Mbol/log T. Several features complicate the structure of composite HRD, namely the presence of double stars which often mimic extended blue loops and the contamination by non-member stars difficult to identify as such in distant clusters. In order to refine the red giant observed evolutionary properties, cluster giants have been remeasured in the Geneva photometry and with the spectrovelocimeter CORAVEL.
A composite color-magnitude diagram for a number of very poor clusterings in the Milky Way
Authors: Lodén L.O.
Published: June 2019

There are indications of the presence of numerous stellar clusterings in the Milky Way which are so poor and unconspicuous that they become detected merely by accident. The true frequency of such objects is probably considerable as there is reason to believe that only a minor fraction has been detected.
Theoretical red-giant branches for globular clusters
Authors: VandenBerg Don A.
Published: June 2019

VandenBerg (1983a; hereinafter V) has recently computed a large grid of stellar evolutionary sequences from the zero-age main sequence to the base of the red-giant branch (RGB) and carried out extensive comparisons of the associated isochrones with published photometry of globular clusters (GCs). These calculations were based on the latest Los Alamos opacities and, in addition, made use of available model atmospheres for improved surface boundary conditions as well as for the transformation of the stellar models from the (Mbol, log Teff)-to the (Mv, B-V)-plane. In general, very encouraging agreement of the predicted and observed morphologies of cluster C-M diagrams was obtained.
Faint CCD photometry in globular clusters. II. Comparison of theoretical isochrones with the globular clusters M4 and M15
Authors: Richer Harvey B. , Fahlman G.G.
Published: June 2019

Globular cluster work touches on virtually all branches of astronomical research. The age of the globular system (or any variations in age among individual clusters) has important cosmological implications as well as relating to the formation time of the halo of our galaxy. Star to star chemical inhomogeneity within a cluster may set important constraints on either mixing within the stars themselves or on the chemical inhomogeneity of the early universe. Metallicity variations among clusters may provide the clue to galaxy-wide enrichment processes, while the cluster color-magnitude diagrams themselves are a testing ground for virtually every facet of stellar evolution.
Systematic main sequence photometry of globular cluster stars for age determination
Authors: Alcaino Gonzalo , Liller William
Published: June 2019

The individual photometric study of the coeval stars in globular clusters presents one of the best observational tests of the stellar evolution theory. Our own globular cluster system provides fundamental clues to the dynamical and chemical evolutionary history of the galaxy, and the study of their ages give us a lower limit to the age of the galaxy as well as to that of the universe. We have been undertaking a systematic research program, and discuss herewith the ages deduced by fitting main sequence photometry to theoretical isochrones of six galactic globular clusters : M4, M22, M30, NGC 288, NGC 3201 and NGC 6397.
Monte Carlo simulations of globular cluster red giant branches
Authors: Crocker Deborah A. , Rood Robert T.
Published: June 2019

Simulations of globular cluster luminosity functions have shown that many of the features observed in actual clusters are probably statistical fluctuations. We suggest one new way of looking at the data which may ultimately lead to some information about the physical parameters of clusters.
Luminosity functions for asymptotic giant branch stars
Authors: Frogel Jay A. , Blanco V.M.
Published: June 2019

To understand the evolution of carbon and oxygen rich asymptotic giant branch (AGB) stars it is important to observationally establish the relations between parameters such as luminosity, age, and metallicity. The existence of luminous (brighter than the top of the first giant branch) AGB stars in clusters in the Magellanic Clouds (Mould and Aaronson 1979; Frogel, et al. 1980) provides a nearly ideal situation in which these relations can be determined. Although metallicities and main sequence turn-off ages are known for only a fraction of the clusters, the ranking scheme devised by Searle, et al. (1980; SWB) indicates that age and metallicity are closely related to one another.
Radial velocity observations of Barium, CH, and R stars
Authors: McClure Robert D.
Published: June 2019

The Ba II, CH, and R0-R3 carbon stars are related in that they are giant stars having about the same position in the HR diagram, and having enhancements of carbon features. The Ba II and CH stars are also noted for enhancements of s process elements. The Ba II stars normally don't exhibit C2 bands that are characteristic of the CH and R stars, indicating that the Ba II stars have a C/O ratio close to but less than unity (Smith 1983). The Ba II and R stars are members of the old disk population (e.g. Eggen 1972), whereas the CH stars are high velocity, population II stars (Keenan 1942).
On the origin of the Barium stars
Authors: Böhm-Vitense Erika
Published: June 2019

We show that Ba stars cannot originate from single stars, they can only be formed in binaries by mass transfer. The companion must then have been an evolved star with log L/L⊙ ≥ 3.2, requiring a radius larger than 0.5 a.u., explaining the long periods of the observed Ba star binaries. If the companion lost half of its mass to the present Ba star we expect to see a white dwarf companion now. Companions with Teff ≈ 12000K have been seen for the nearest Ba stars. For Ba stars at larger distances companions can only be detected if they have Teff ≥ 20000K.
Non-LTE analysis of central stars∗
Authors: Kudritzki R.P. , Méndez R.H. , Simon K.P.
Published: June 2019

Most of our present knowledge about central stars of planetary nebulae (CPN) is obtained by indirect methods using the emission line spectra of the surrounding nebula. These methods, which apply the beautiful recombination theory, can provide us with information about temperature, distance and radius of the CPN. However, we know that these methods are subject to severe problems, which then lead to strong discrepancies in the parameters of the CPN.
Spectroscopic observations of nuclei of planetary nebulae
Authors: Acker Agnès
Published: June 2019

Up to date, 1518 true, possible, and probable planetary nebulae (PN) are known in our Galaxy; 463 nuclei (NPN) were observed. For about 150 stars, a spectral study has been done; only about 30 NPN have a well studied spectrum. (Acker, Gleizes et al, 1982 “Catalogue of the central stars of true and possible PN”) It must be remembered that this is a difficult study, as the PN are very distant objects (the nearest, Helix, is about 120 pc), and that their central stars are very faint (the 35 brightest have a magnitude of from 9 to 12), are generally of a particular spectral type, and have a spectrum in which nebular lines interfere with stellar features.
NLTE analysis of SDO stars
Authors: Heber U. , Hunger K. , Kudritzki R.P. , Simon K. P.
Published: June 2019

Among the faint blue halo stars the sdO's form a group whose evolutionary status is still not fully understood. Phenomenologically they appear to be related to the horizontal branch. The knowledge of stellar parameters and abundances may give a clue for understanding their evolutionary status. As the sdO's are hot (Teff ≥ 35000K), the assumption of LTE leads to substantial errors. Hence detailed NLTE analyses are inevitable.
Massive star evolution in nearby galaxies
Authors: Humphreys Roberta M.
Published: June 2019

In this review I will primarily be discussing the observational data relevant to understanding the process of stellar evolution in galaxies of different types. This discussion will focus on the stellar content of the nearer galaxies; those galaxies in which the brightest individual stars are resolved and can be observed.
Infrared and visual observations of h and χ Persei
Authors: Tapia M. , Roth M. , Costero R. , Navarro S.
Published: June 2019

Near-infrared observations of 82 stars in h and χ Persei (NGC 869 and 884) were obtained with the Mexican National Observatory infrared photometer/spectrometer on the 2.1 m telescope at San Pedro Mártir, Baja California. The JHK photometry covers most of the stars in the upper main sequence of the central parts of the clusters as well as the giants and supergiants in a more extended region, with additional L' and M measurements of the brightest members. In Figure 1 the (J-H) vs (H-K) and (H-K) vs (K-L) diagrams are presented. In order to complement the available good quality UBV photometry, we carried out photoelectric measurements of 23 stars in our sample for which only low quality photographic data has been published. These observations were made with the pulse-counting photometer attached to the newly refurbished 1.5 m telescope at San Pedro Mártir.
Neutrino-pair bremsstrahlung in dense stars
Authors: Itoh Naoki , Kohyama Yasuharu
Published: June 2019

Neutrino-pair bremsstrahlung rate is calculated in the framework of the Weinberg-Salam theory for the dense matter relevant to the interior of white dwarfs and neutron stars. Ionic correlations both in the liquid state and in the bcc lattice state have been taken into account accurately. It is found that the ionic correlation in the liquid state reduces the neutrino-pair bremsstrahlung rate typically by a factor 2–20 depending on the element and temperature. It is also found that accurate inclusion of the Debye-Waller factor reduces the neutrino-pair bremsstrahlung rate in the lattice state typically by a factor 2.
Constraints on stellar evolution theory from precise eclipsing binary data
Authors: Andersen J. , Clausen J.V. , J⊘rgensen H.E. , Nordström B.
Published: June 2019

Previous attempts at a detailed confrontation of eclipsing binary data with theoretical models of main-sequence evolution were faced with the choice between data of inhomogeneous (mostly low) quality for many systems (Kriz, 1969; Lacy, 1979) or accurate values of mass, radius, and temperature (or luminosity) for very few systems only (Popper et al., 1970). In addition, more detailed and homogeneous stellar structure calculations for several compositions were needed. Since 1972, a coordinated photometric and spectroscopic programme at our institute contributes to building a sufficient observational basis for such a test. Among published standard models for the range 1–10 M⊙, Hejlesen's (1980) are the most extensive, agree well with other standard models, and are presented in a format suitable for comparison with binary data. Here we can only outline a few salient new results from this study.
A test of stellar evolution theory by visual binaries
Authors: Corbally Christopher J.
Published: June 2019

When close visual binaries have good and homogeneous data, they can prove to be precision probes of stellar evolution theory.
The evolutionary history of BE/X-ray binaries
Authors: Habets G.M.H.J.
Published: June 2019

A 2.5 M⊙helium star remnant of a Case B mass transfer is evolved to off-centre neon ignition and a second mass transfer phase, Case BB, is explored. The model for the formation of Be/X-ray binaries by mass-transfer dominated evolution in an intermediate mass binary is confirmed.
Cepheid companions and the masses of cepheids
Authors: Böhm-Vitense Erika , Borutzki Susan , Harris Hugh
Published: June 2019

We have observed in the ultraviolet the hot companions of the Cepheids SV Per, RW Cam, SY Nor and KN Cen. The study of the absolute and relative intensities reveals that all, except the companion for KN Cen are evolved stars which should fit on almost the same mass track as the Cepheid. We find however that with generally accepted reddening values the companions of at least SV Per and RW Cam are too faint. Either the Cepheid loops are more luminous than presently calculated or the reddening is larger than presently accepted.
Physical mechanisms of mixing in stellar interiors
Authors: Schatzman Evry
Published: June 2019

The different mechanisms by which mixing can take place in stellar interiors are considered : the classical Rayleigh-Benard instability with penetrative convection and over-shooting, semi-convection, gravitationnal and radiative settling, turbulent mixing. The latter mechanism is thoroughly described, from the driving force of turbulent mixing to its influence on stellar structure, stellar evolution and the analysis of the corresponding observationnal data.

Turbulent mixing has to be considered each time the building up of a concentration gradient takes place, either by gravitationnal or radiative settling or by nuclear reactions. Turbulent mixing, as a first approximation, can be described by an isotropic diffusion coefficient. The process is then governed by a diffusion equation. The behaviour of the solution of the diffusion equation needs some explanation in order to be well understood.

A number of examples concerning surface abundances of chemical elements are given (3He, 7Li, Be, 12C, 13C, 14N), as well as a discussion of the solar neutrinos problem.

The building up of a µ-barrier, which stops the turbulence allows stellar evolution towards the giant branch and explains nitrogen abundance at the surface of giants of the first ascending branch.

Turbulent mixing is also of some importance for the transfer of angular momentum and has to be taken into account for explaining the abundance of the elements in Wolf-Rayet stars.
On the Tassoul approximation scheme for determining the structure of rotating stars
Authors: Roxburgh Ian W.
Published: June 2019

The method used by Tassoul and Tassoul assumes a “turbulent viscosity” which is important in determining the dynamics, but is unimportant in heat transport. This approximation is inconsistent, the argument is as follows:

The rotation is expanded about uniform rotation in a series.
Evolution of the sun with mixing by hydrodynamic instabilities
Authors: Law Wai-Yuen , Knobloch E. , Spruit H.C.
Published: June 2019

Following Schatzman and Maeder (1981) we compute the evolution of the sun with partial mixing by hydrodynamic instabilities. Instead of simply assuming a turbulent diffusion coefficient which is a constant multiple of the viscosity, we incorporate some of the properties of hydrodynamic instabilities. This puts limits on the amount of diffusion that can be obtained, and makes it dependent on time and position in the star.
Stellar evolution with turbulent diffusion mixing in low mass stars and 12C/13C ratio in giants of the first ascending branch
Authors: Bienaymé O. , Maeder A. , Schatzman E.
Published: June 2019

We consider stellar evolution in low mass stars (1–3 Mo) near the main sequence with the hypothesis that mild turbulence is present within the all star. Turbulent transport of the elements is modeled by diffusion equations where the diffusion coefficient is chosen to be D = R✶eν where ν is the kinematical viscosity and R✶e is a Reynolds number. We consider the effects of the growth of the gradient of the mean molecular weight on turbulence. The main consequences of diffusion on stellar evolution are (1) an increase of the life time near the main sequence and (2) a change of the radial distributions of chemical species (12C, 13C, 14N, 160) (figure 1). The inhibition of the turbulence, when the gradient of mean molecular weight reaches a certain critical value, allows the evolution towards the red giant branch. When stars evolve towards the giant branch, chemical species are dredged up to the surface. At this stage models with and without diffusion, predict substantially different surface abundances (in particular the 12C/13C and C/N ratios). Comparison between models and the available data on giants during the first dredge-up show that abundance anomalies can be explained if turbulent mixing is present during the main sequence phase (figure 2).
The relation between stellar evolution and cosmology
Authors: Tayler R. J.
Published: June 2019

Observations of star clusters combined with the theory of stellar evolution enable us to estimate the ages of stars while cosmological observations and theories give us a value for the age of the Universe. This is the most important interaction between cosmology and stellar evolution because it is clearly necessary that stars are younger than the Universe. Stellar evolution also plays an important rôle in relating the present chemical composition of the Universe to its original composition.
Theoretical predictions for the radial distribution of oxygen in spiral galaxies
Authors: Tosi M. , Diaz A.I.
Published: June 2019

To the aim of reproducing the oxygen abundances and gradients observed in the disk of our Galaxy and four nearby spirals (M31, M33, M83, and M101), we have computed numerical models of galactic evolution assuming only two free parameters: the infall of gas from outside the disk and the law of star formation (e.g. proportional to some power of the gas density, decreasing with time, constant, etc.).
Short-Period Nutation from Observation with the Pulkovo Polar Tube
Authors: Bakhrakh N. M.
Published: June 2019

Since 1953 regular observations have been made with the polar photographic tube at Pulkovo, a fixed astrograph (D = 20 cm, F = 600 cm), which can take photographs of a circumpolar zone of 60′ radius (Bakhrakh, 1971). An analysis of measured polar distances of the same 30 stars on each plate gives corrections to the adopted values of the constants of aberration and precession and of the coefficients of nutation. At present the determination of the coefficients of the short-period semi-annual solar and fortnightly nutations is of greatest interest, as they are affected most by the Earth's liquid core.
Elimination de Certains Effets dans les Observations à l'Astrolabe: Application à l'Évaluation de Corrections aux Termes Principaux de la Nutation
Authors: Chollet F.
Published: June 2019

Le travail entrepris ici porte sur les mèmes observations de latitude effectuées à Paris, au moyen d'astrolabes, que celles utilisées dans d'autres études (Capitaine, Chollet et Débarbat, 1977; Capitaine, 1977). Pour des raisons qui apparaitront plus loin nous n'avons pu utiliser que la période comprise entre septembre 1970 et le début de 1977.
A Determination of the Principal Term of Nutation
Authors: Feissel M. , Guinot B.
Published: June 2019

The method for deriving the amplitudes of the principal term of nutation from the z-term of latitude and the corresponding term of UT (here denoted by w) is well known (Yokoyama, 1977).
The Determination of Absolute Phase of a Long Baseline Interferometer and its Application to the Precise Measurement of the Constant of Nutation
Authors: Cannon W. H. , Yen J. L.
Published: June 2019

Long Baseline Interferometry (L.B.I.) refers to a dramatic technical breakthrough in astronomy accomplished almost exactly ten years ago in the spring of 1967 by a group of workers at the National Research Council of Canada and some major Canadian Universities. The Canadian effort was duplicated within a month by an independent American effort and it was realized soon afterward that the new technique of L.B.I. held enormous potential for geodynamical as well as astronomical studies.
On the Equation of Precession and Nutation of the Dynamically Unbalanced Earth
Authors: Erzhanov Zh. S. , Kolybaev A. A. , Egorov Al. K.
Published: June 2019

In contrast to the deduction of the equations of precession and nutation adopted as a standard by the IAU, the authors develop a rigorous theory of the rotation of the Earth taking into account the inequality of the equatorial moments of inertia of the Earth and retaining small terms usually neglected to simplify an approximate solution.

The equation is expressed in terms of the so-called Beletsky-Chernousko's variables used in astrodynamics.
The Period of the Chandler Wobble
Authors: Dahlen F. A.
Published: June 2019

Realistic models of the Earth are known to possess a solid anelastic inner core, mantle and crust, and a fluid core and oceans. How might we go about calculating the theoretical free period of the Chandler wobble of such an Earth model? Let xi be a set of Cartesian axes with an origin at the center of mass, and let ωi be the instantaneous angular velocity of rotation of these axes with respect to inertial space. The net angular momentum is then Cijωj + hi, where Cij is the inertia tensor, and hi is the relative angular momentum. Let us affix the axes xi in the mantle and crust by stipulating that the relative angular momentum is that of the core and oceans alone, i.e., hi (mantle and crust) = 0; hi = hi (core and oceans). For an infinitesimal free oscillation of angular frequency σ, we can write ωi = Ω(δi3 + mi eiσt), Cij = A(δilδjl + δi2δj2) + Cδi3δj3 + cij eiσt, and hi = hi eiσt, where Ω is the mean rate of rotation and A and C are the mean equatorial and polar moments of inertia.
Local Effects on Earth Tide Observations
Authors: Harrison J. C.
Published: June 2019

Cavity, topographic and geologic effects have similar influences on the observed tidal variations of tilt and strain. They cause the locally observed tilts and strains to differ from the “true” or regional values.
Global Plate Tectonics and the Secular Motion of the Pole
Authors: Soler Tomás , Mueller Ivan I.
Published: June 2019

Analysis of astronomical observations recorded during the last 75 years by international services (ILS-IPMS, BIH) in charge of providing the coordinates of the instantaneous pole conclusively proves a persistent drift of the “mean pole” (≡barycenter of the wobble). A study was undertaken with the specific objective of investigating the possibility of a true secular motion of the barycenter, that is, an actual displacement of the Earth's pole of figure. Geophysical hypotheses available to explain the astronomically-observed drift of the “mean pole” suggest changes in the Earth's second-order inertia tensor as a plausible cause.
Report of General Discussions at IAU Symposium No. 78 on Nutation and the Earth's Rotation
Authors: Wilkins G. A.
Published: June 2019

The purpose of this report is to summarize the discussions held on Friday, 1977 May 27, that preceded the adoption by IAU Symposium No. 78 of the four symposium resolutions concerning the theoretical and observational studies of nutation. It was the aim in the first half of the session to clarify the scientific problems and to obtain a broad concensus so that the resolutions committee could finish drafting the resolutions to be put to the symposium after the coffee-break. During the second half-session some new scientific points were made, but they have been incorporated in the report of the discussions during the first half-session; the report for the second half-session contains only a record of the voting and of the discussions on procedure and on the wording of the resolutions.
HI Velocity Fields and Rotation Curves
Authors: Bosma A.
Published: June 2019

Recent results on 21-cm line velocity fields of spiral galaxies are reviewed. Attention is drawn to the sometimes discrepant results on the spatial orientation of galaxies inferred from various methods. Major classes of deviations from circular, planar, motion of the neutral gas are discussed. Some comments are made about HI rotation curves.
A High Resolution HI Survey of M31
Authors: Brinks E.
Published: June 2019

The first results of a new high resolution 21-cm HI line survey of M31 made with the Westerbork Synthesis Radio Telescope are presented. Five areas were mapped, covering the galaxy except for the extreme northern and southern parts, at a resolution of δα × δδ × δV = 24″ × 36″ × 3.2 km s−1. The spatial resolution corresponds to 30 × 120 pc at the distance of M31. This is of the same order as the resolution at the distance of the center or our own galaxy given by a 25-m dish. Consequently the M31 survey is comparable to surveys of the Milky Way galaxy in wealth of detail as well as in amount of data (∼ 1 Gigabyte).
High Velocity HI in the Inner 5 kpc of M31
Authors: Brinks E.
Published: June 2019

New observations made with the Westerbork Synthesis Radio Telescope of M31 in the line of neutral hydrogen (Brinks, this volume) show the presence of high-velocity HI in the inner 4–5 kpc of the galaxy. There were indications from previous 21-cm line studies that HI gas is moving with peculiar velocities (Whitehurst and Roberts, 1972; Unwin, 1979) but the new maps, made with a resolution of δα × δδ × δV = 24″ × 36″ × 8.2 km s−1 and sufficient sensitivity show for the first time the distribution of this material.