bluuebunny/crossref_metadata_2025 huggingface dataset:
Beams in Magnetised Pair Plasmas
Authors: Rowe E. T.
Published: July 2016

The radiative instability was considered in the context of pulsar radio emission by Goldreich & Keeley (1971) and rederived and extended by Asséo, Pellat, & Sol (1983) and by Asséo (1995). Their results can be generalised and reproduced by replacing the thin cylindrical ring of charged particles by an infinitesimally thin current carrying sheet in either planar or cylindrical geometry, suggesting that the local ring geometry may not be essential for the instability. It may be useful to further investigate the generalised dispersion equation given below.
A Ray-Tracing Model of the Vela Magnetosphere
Authors: Hirano C. , Gwinn C. R.
Published: July 2016

In the relativistic plasma surrounding a pulsar, a subluminal ordinary-mode electromagnetic wave will propagate along a magnetic field line. After some distance, it can break free of the field line and escape the magnetosphere to reach an observer. We apply a simple model of pulsar radio emission based on this scenario to the case of the Vela pulsar and find it reproduces some qualitative characteristics of the observed Vela pulse profile.
Probing pulsar winds using inverse Compton scattering
Authors: Ball Lewis , Kirk J. G.
Published: July 2016

We investigate the modifications to the calculations of inverse Compton scattering by the wind of pulsar B1259–63 due to the inclusion of a realistic spectrum for the target photons from the pulsar’s Be-star companion.
How well are Neutron Stars understood?
Authors: Kundt Wolfgang
Published: July 2016

Alternative ways are discussed in which pulsars may (1) drive their winds, (2) avoid net electric currents, (3) emit coherent radio pulses, (4) acquire high spin rates, and (5) deal with moderate surface magnetic fields: 1011<B/G≲ 1014.
Deconfinement signals from pulsar timing
Authors: Grigorian Hovik , Poghosyan Gevorg , Chubarian Edvard , Blaschke David
Published: July 2016

The occurence of a quark matter core in rotating compact stars has been investigated within general relativity as a function of both the rotational frequency and the total baryon number. We demonstrate that the deviation of the braking index fromn= 3 signals not only the occurence but also the size of a quark matter core in a pulsar. We suggest that in systems with mass accretion onto a rapidly rotating compact star a spin-down to spin-up transition might signal a deconfinement transition in its interior.
Magnetic field of pulsars with superconducting quark core
Authors: Blaschke David , Sedrakian David M. , Shahabasyan Karen M.
Published: July 2016

Within recent nonperturbative approaches to the effective quark interaction the diquark condensate forms a superconductor of second kind. Therefore the magnetic field will not be expelled from the superconducting quark core in accordance with observational data which indicate that life times of pulsar magnetic fields exceed 107years.
About the Magnetic Field Generation in Crab Nebula
Authors: Nanobashvili Irakli S.
Published: July 2016

The new plasma mechanism for the magnetic field generation in Crab Nebula is suggested. The mechanism is based on the development of two-stream instability after the supernova explosion.
Recycling in progress: RXTE discovery of the first accretion-powered millisecond pulsar
Authors: van der Klis M.
Published: July 2016

The discovery is reported of the first accretion-powered millisecond pulsar, SAX J 1808.4–3658. This 2.5 millisecond pulsar has a magnetic field strength of 1–10108Gauss and has all the characteristics of the long-predicted millisecond radio pulsar progenitor, a neutron star in an X-ray binary system where the process of recycling is taking place at this time.
Low Frequency Radio Emission of Pulsar PSR J1907+0919 Associated with the Magnetar SGR1900+14
Authors: Shitov Yu. P. , Pugachev V. D. , Kutuzov S. M.
Published: July 2016

The soft gamma repeater SGR 1900+14 was observed in Pushchino observatory since 1988 December using BSA radio telescope operating at 111 MHz. We have detected the pulsed radio emission (Shitov 1999) with the same 5.16 s period that was reported earlier for this object (Hurley et al. 1998). The timing analysis has shown that this new radio pulsar PSR J1907+0919 associated with SGR 1900+14 has a superstrong magnetic field, which is 8.1 · 1014G, thereby confirming that it is a ”magnetar” (Duncan & Thompson 1992; Kouveliotou et al. 1999). The dispersion measure of PSR J1907+0919 is 281.4(9)pc·cm−3which gives an estimate of the pulsar’s distance as about 5.8 kpc.
The Period of Organization of the International Latitude Service: 1889–1899
Authors: Proverbio E.
Published: July 2016

Around 1880, and for some time after that, the possibility of revealing a variation in latitude as a consequence of a separation of the instantaneous rotation axis from the Earth’s axis of inertia gave rise to much perplexity due to the complexity of the problem and the existence of non-negligible and hard-to-find systematic errors in observations of a personal and instrumental nature. These errors also depended on effects of refraction and imprecise knowledge of star declinations.

To this must be added the fact that the very idea that the rotational axis and the axis of inertia were distinct and in relative motions raised difficult problems of a physical and theoretical nature. At that time the idea of the Earth’s rigidity was still generally accepted and, even admitting the hypothesis of an Earth endowed with sufficient elasticity and plasticity, the theory of which had been partly examined by G.H. Darwin, it was then almost impossible, just as it still is today, to create a model of the movements of mass inside the Earth which could offer an explanation of possible aperiodic and secular variations. In reality, more than on the existence of periodic variations, the attention and interest of geodesists and astronomers was in those years focused on the problem of the existence or non-existence of secular variations in the Earth’s principal axis.
History of the International Polar Motion Service/International Latitude Service
Authors: Yokoyama Koichi , Manabe Seiji , Sakai Satoshi
Published: July 2016

The history of the International Latitude Service and the International Polar Motion Service is described, with an emphasis on the evolution of the international cooperation for monitoring the Earth’s rotation. Also given is a brief description of the history of the Japanese geodetic and astronomical activities, as well as the future prospects.
History of the Bureau International de l’Heure
Authors: Guinot B.
Published: July 2016

At the beginning of the 20th century, the development of radio time signals offered the possibility of unifying the measurements of Universal Time (UT). A new service, the Bureau International de l’Heure, hosted by the Paris Observatory, was entrusted with this task. The BIH began its operation in 1912, although its statutes were officially settled only in 1919. This paper recalls the activities of the BIH on time determination and various connected fields: Earth rotation, reference frames, atomic time. With the importance of atomic time and the emergence of new techniques for the measurement of Earth rotation, a new organization was required. It was prepared by the MERIT and COTES programs (1978) and by the bodies of the Metre Convention, with the active participation of the BIH. The BIH was dissolved at the end of 1987, its work being shared between the Bureau International des Poids et Mesures and the new International Earth Rotation Service.
E. P. Fedorov as President of Commission 19 of IAU During the Period of the Reorganization of ILS
Authors: Korsuń A.O.
Published: July 2016

Evgeniy Pavlovich Fedorov (1909–1986) was President of Commission 19 of the IAU in 1955–1961. In this period the future of the ILS was discussed very actively and the plan for future study of the polar motion was elaborated. E. Fedorov was the organizer and the leader of these preparatory works.

He was editor of the collection of papers “On the present state and the future of latitude investigations” (1960, Moscow). In this collection well-known scientists discussed their opinions on the state latitude observations and their improvement. Among them where: H. Spencer Jones, P. Melchior, T. Hattori, I. Fleckenstein, N. Sekiguchi, W. Munk, R. Vicente, A. Young, E. Fedorov, M. Torao, N. Stoyko. In that time Fedorov wrote on the problem of the ILS. The inception of the ILS was preceded by a period of thorough discussion of various aspects of latitude work. By the end of the 19th century polar motion had become a problem of vital importance in astronomy and geophysics. Many efforts were made at that time to find the best means for obtaining the most accurate polar coordinates. As a result a plan of international cooperation for the study of polar motion was worked out.
Determination of EOP from VLBI in IAA
Authors: Skurihkina E.
Published: July 2016

Results of Earth orientation parameter (EOP) determinations from NEOS-A and CORE programs reduced using the package OCCAM version 3.5 at the Institute of Applied Astronomy of Russian Academy of Science (IAA) are presented. Results of EOP determination using different reference stations, relativistic models, the IERS Standards (1992) and IERS Conventions (1996) are also presented.
SLR Contribution to Investigation of Polar Motion
Authors: Malkin Zinovy
Published: July 2016

The Satellite Laser Ranging (SLR) technique has been used to determine Earth Rotation Parameters (ERP) for over twenty years. Most of results contributed to the International Earth Rotation Service (IERS) are based on analysis of observations of Lageos 1 & 2 satellites collected by the global tracking network of about 40 stations. Now five analysis centers submit operational (with 2–15 days delay) solutions and about ten analysis centers contribute yearly final (up to 23 years) ERP series. Some statistics related to SLR observations and analysis are presented and analyzed. Possible problems in SLR observations and analysis and ways of its solution are discussed.
Anomalous Roughness of the Pole Path at the Time of the 1994 Bolivia and Kurile Islands Earthquakes
Authors: Spada G. , Alfonsi L. , Soldati G.
Published: July 2016

We report anomalies in the roughness of the path of the pole of rotation at the time of the Bolivia earthquake of June 9, 1994 (Mω = 8.2) and of the Kurile Islands earthquake of October, 4, 1994 (Mω = 8.3). This finding reinforces the results of previous studies, which have indicated changes in the polar motion curvature at the time of major earthquakes.
Excitation of Polar Motion
Authors: Wilson Clark R.
Published: July 2016

Conceptual models of polar motion have evolved over the past century, as improved data revealed signals over progressively wider frequency bands. In the 1890s, Chandler represented polar motion as a sum of discrete components, 14 month and annual terms, and this component model effectively summarized the observations, but did not provide a physical explanation for them. Over time both the search for a physical understanding of polar motion, and the ability to observe the broad band continuum outside the Chandler and annual bands have led to an understanding of polar motion as a continuum of variations, not adequately described by a few discrete components. The continuum concept is now the working model in most studies of polar motion. The transition from component to continuum conceptual models preceded the arrival of high quality data by several decades, and reflected significant contributions from Harold Jeffreys. With modern space geodetic observations and good global numerical models of the atmosphere, oceans, and other climate processes, it is clear that air and water motion and redistribution are the dominant contributors to the excitation continuum.
Study of the Regime of the Polar Motion by Means of Numerical Method
Authors: Rykhlova L. , Kurbasova G.
Published: July 2016

Analysis of the spectral power-density function and the Poincaré method are used to identify the type of motion exhibited by the Earth’s pole from 1900–1990. The former method allows identification of a quasi-periodic regime with two main frequencies — annual and Chandler. The existence of combinational frequencies in this spectrum and the broadening of the spectral peaks suggest a quasi-periodic regime making a transition to chaos. It is concluded that the identification of the polar motion regime over the time interval considered is insufficient to predict the further evolution of the system over arbitrarily long times.
Nonlinear Dynamics Method for Excitation and Attenuation of Chandler Wobble
Authors: jun Wang Wen
Published: July 2016

In this paper, we introduce a nonlinear dynamical model for Chandler wobble including resonance excitation, bifurcation dissipation, frequency modulation, parameter resonance and visco-elastic long-time attenuation.
Short-Period Oscillations of Earth Rotation
Authors: Kołaczek B. , Kosek W. , Schuh H.
Published: July 2016

Sub-seasonal variations and especially sub-seasonal oscillations with periods of about 120, 60, 50, 40 days in polar motion and of about 120, 60–90, and 50 days in LOD are presented. Variations of amplitudes of these sub-seasonal oscillations of polar motion are shown. Maxima of these amplitudes are of the order of 2–4 mas. These oscillations are elliptical ones. The correlation coefficients between geodetic and atmospheric excitation functions in this range of the spectrum are variable and have annual variations. Maxima of correlation coefficients are of the order of 0.6–0.8.

Modern geodetic VLBI experiments provide very accurate results in polar motion and UT1–UTC with a temporal resolution of 3–7 minutes. Several irregular, quasi-periodic variations were found. In many UT1–UTC data sets, oscillations with periods around 8 hours and between 5 and 7 hours can be seen.
Comparison of the Short Period Rigid Earth Nutation Series
Authors: Bizouard Ch. , Folgueira M. , Souchay J.
Published: July 2016

We present a comparison of the diurnal and subdiurnal nutations of the three last theories of rigid Earth nutation: SMART97, RDAN97 and REN 2000. For a better interpretation of the observations, we characterize their contribution to the polar motion and we estimate the nonrigid effects.
Advanced Observations of Lunar Physical Librations and Gravitational Fields in Japanese Lunar Missions in the Near Future
Authors: Hanada Hideo , Heki Kosuke , Kawano Nobuyuki , Ooe Masatugu , Tsubokawa Tsuneya , Tsuruta Seiitsu , Ishikawa Toshiaki , Araki Hiroshi , Matsumoto Koji , Takanezawa Takashi , Kono Yusuke , Karoji Hiroshi , Iwata Takahiro , Kaneko Yutaka , Yokoyama Takaaki
Published: July 2016

In the SELenological and ENgineering Explorer (SELENE) project which is the Japanese lunar program to be launched in 2003 by the Institute of Space and Astronautical Science (ISAS) and National Space Development Agency of Japan (NASDA), we measure angular distance between a radio transmitter on a relay satellite, that on the Moon and quasars by differential VLBI and determine amplitudes of the physical librations, gravitational harmonic coefficients of the Moon and lunar ephemeris with an accuracy one or two orders higher than before in cooperation with 4-way Doppler measurements and two-way Doppler and ranging measurements using the lunar orbiter and the relay satellite. We are proposing another selenodetic mission, In situ Lunar Orientation Measurement (ILOM) to study lunar rotational dynamics by direct observations of the lunar physical libration from the lunar surface with an accuracy of 1 milliarcsecond in a post-SELENE project which will be launched about three years after SELENE. Year-long trajectories of the stars provide information on various components of the physical librations and we will also try to detect the lunar free librations in order to investigate the lunar mantle and the liquid core.
Observational Aspects of Multiperiodicity in the β Canis Majoris Stars
Authors: Lesh Janet Rountree , Aizenman Morris L.
Published: July 2016

Multiperiodicity has been recognized as an important aspect of β Canis Majoris-type variability ever since the intensive observations of the “classical” members of this group by Struve and his coworkers in the early 1950’s. About half the stars observed by Struve exhibited a radial-velocity variation whose period was several hours, but whose amplitude was modulated with a period of the order of days. This quickly became known as the “beat phenomenon,” and was interpreted as an interference between two nearly equal short periods.
Red Variables
Authors: Wood P. R.
Published: July 2016

This paper will be concerned with those variables lying on the cool side of the cepheid strip in the region of the HR diagram occupied by the red giant and supergiant stars. The blue edge of the red variable region for old disk population stars has been found by Eggen (1973b) to be at (R-I)K˜ 0.9 (log Teff˜ 3.53). According to Eggen (1973a, 1973b), all giant stars cooler than this vary, although the amplitude is very small (ΔV~0.2 mag) near the blue edge. In the halo population the blue edge is considerably hotter at (R-I)K˜ 0.5 (log Teff˜ 3.62). On the other hand, some small amplitude red variables (eg. R Dor, AK Hya, IQ Her) have been found at the low temperatures (RK-RK > 1.6) where large amplitude red (Mira) variables exist. From these results, it appears that the position of the blue edge deoends on some unknown stellar parameter(s). Auman (1971) has suggested that the helium abundance may be involved.
Multiple Periodicities in Cataclysmic Variable and White Dwarf Stars
Authors: Warner Brian
Published: July 2016

The normal dwarf nova (DN) outburst is characterized by a rapid rise, a brief stay near maximum and a slower decline to minimum light; the whole sequence lasts in general for 4 to 6 days, but can take as long as 10 or 12 days in some stars. While not strictly periodic, the DN outbursts are quasi-periodic in the sense that the mean periods derived from intervals sufficient to contain at least 50 outbursts (i.e. a few years for the shortest period systems, up to 30 years for longer period systems) remain sensibly constant. It should be added, however, that in the case of U Gem there is evidence for an increase in its recurrence period which may indicate some evolutionary change: for the first 50 years of observation of U Gem the mean period was 96. 5 days and for the second 50 years it was 107.6 days (Mayall, 1957); during the past four years the mean interval has been 291 days (with only one outburst in 1974).
Non-Radial Oscillations of Degenerate Dwarfs: A Theoretical Review
Authors: Van Horn H.M.
Published: July 2016

The current status of the theory of non-radial oscillations of white dwarfs and hydrogen shel1-burning degenerate stars, in the linear, quasi-adiabatic approximation, is reviewed. Relevant aspects of the thermal structure of such stars are summarized, and several problem areas requiring further investigation are identified. Among the most interesting and important of these are the question of the existence of g modes in white dwarfs; the nature of the excitation mechanisms for non-radial oscillations; the possibility of tidal excitation; the problem of mode-coupling between pulsations and convection; and the question of the effects of a solid, crystallizing core.
Planetary Theories and Observational Data
Authors: Duncombe R. L. , Seidelmann P. K.
Published: July 2016

A brief review is given of planetary theories from Leverrier to Newcomb to the age of computers. The presently used planetary theories are discussed and the process of replacing these theories with new ones is described. Some difficulties in preparing new planetary theories and the observational discrepancies which have been encountered previously are discussed.
Qualitative Dynamics of the Sun-Jupiter-Saturn System
Authors: Szebehely V.
Published: July 2016

The stability of the three-body problem formed by the Sun, Jupiter and Saturn is investigated using surfaces of zero velocity. The results obtained with the models of the restricted and general problems of three bodies are compared with numerical integration. The system is found to be stable in the sense that Saturn will neither interrupt the (perturbed) binary orbit of Jupiter around the Sun, nor will it escape from the system. It is shown that the known classical triple stellar systems are “more stable” than the solar system, which in turn is “more stable” than the Earth-Moon system.
A New Approach for the Construction of Long-Periodic Perturbations
Authors: Dvorak Rudolf
Published: July 2016

The aim of this work is to study perturbations of planets of a period of some thousands of years. The use of an analytical method allows us to separate all different influences, e.g. near resonances and is combined with the very precise method of the numerical integration. The truncation to low orders can be avoided which is made by analytical methods in using developments with respect to the small parameters inclinations and eccentricities. For this purpose a special form of the Lagrange Equations is used where the terms containing the inverse distancefrom the planet to the perturbing one are separated as it is the most difficult to compute. To develop this a specific formulation has been found where the short periodic terms can precisely be determined. Although the development seems to be of a certain complexity the small numbers of quantities used can be tabulated once and for all in a specific problem. It should be possible to integrate the new form of the Lagrange Equations within a reasonable computer-time to determine the long periodic perturbations.
Relation of a Contracting Earth to the Apparent Accelerations of the Sun and Moon
Authors: Lyttleton R.A.
Published: July 2016

The tidal theory of the evolution of the lunar orbit has remained inconsistent with the observational values of the apparent secular accelerations of the Sun and Moon since it was first developed by Jeffreys in 1920. Allowance for a changing moment of inertia of the Earth enables the discrepancy to be completely removed if a decrease is occurring at a rate of just about the amount already required by the phase-change theory of the nature of the terrestrial core. The agreement of the resulting theory with the latest determinations of the lunar acceleration increases confidence in the phase-change hypothesis. On the other hand the theory renders it most unlikely that a changing constant of gravitation will prove necessary to account for the observations. On the present theory of itself the Moon would have been extremely close to the Earth only about 109 years ago which suggests that some additional process may at times have influenced the lunar orbit.
Comets and the Missing Planet
Authors: Ovenden Michael W. , Byl John
Published: July 2016

Integrating backwards in time in the circular restricted three-body problem Galaxy-Sun-Comet, for both the real long-period comets and fictitious random sets of orbital elements, we have confirmed van Flandern’s conclusion that there is a statistically-significant clustering of the orbits of real long-period comets, in heliocentric direction, some 5×106 years ago. The clustering is also significant in heliocentric distance, and is more marked if it is assumed that the comets have gone round the Sun more than once since the epoch of maximum clustering. We suggest that the “event” discovered by van Flandern is not the explosive disruption of a planet formerly in the asteroid belt, but the latest in a series of minor catastrophies, such as the collisional break-up of a pair of large asteroids.
Hamiltonian Theory of the Libration of the Moon
Authors: Henrard Jacques , Moons Michèle
Published: July 2016

The feasibility of applying the Lie transform method to the problem of the physical libration of the Moon is investigated. By a succession of canonical transformations, the Hamiltonian of the problem is brought under a form suitable for perturbation technique. The mean value of the inclination of the angular momentum upon the ecliptic and the frequencies of the free libration are computed.
Numerical Integration of Nearly-Hamiltonian Systems
Authors: Bond Victor R.
Published: July 2016

Consideration is given to the solution by numerical integration of systems of differential equations that are derived from a Hamiltonian function in the extended phase space plus additional forces not included in the Hamiltonian (that is, nearly-Hamiltonian systems). An extended phase space Hamiltonian which vanishes initially will vanish on any solution of the system differential equations. Furthermore, it vanishes in spite of the additional forces, and defines a surface in the extended phase space upon which the solution is constrained.
An Application of the Stroboscopic Method
Authors: Roth E. A.
Published: July 2016

In this paper the motion of an orbiter of a satellite of one of the major planets is considered. The orbiter undergoes various perturbing effects. It is shown that the semi-analytical stroboscopic method is well suited to take into account all perturbations.
Theory of Motion of Jupiter’s Galilean Satellites
Authors: Lieske J.H.
Published: July 2016

The final results for the theory enabling one to calculate the positions of the Galilean satellites and their partial derivatives are presented, following the techniques outlined in earlier papers. Extensive use of algebraic manipulation software on a digital computer is employed to generate the final expressions. The new theory is, in effect, a revitalization of Sampson’s theory in which we (a) remove algebraic and mathematical errors existing in Sampson’s work, (b) introduce some neglected effects due to solar interactions and the 3-7 commensurability, (c) allow for non-zero amplitude and phase of the free libration, (d) express the final results as analytic functions of variations in 49 arbitrary constants of integration and physical parameters, (e) construct the theory in a manner which readily allows for future revision, and (f) provide analytic expressions for the partial derivatives with respect to the 49 parameters.
Perturbations of Critical Mass in the Restricted Three-Body Problem
Authors: Sharma R.K. , Subba Rao P.V.
Published: July 2016

Based upon the authors’ result (Astron. Astrophys. 43, 331-3, 1975) that oblateness of the more massive primary decreases the value of the critical mass, this note is concerned primarily with a few observations on Szebehely’s result (Astron. J. 72, 7-9, 1967) that the Coriolis force is a stabilizing force. It has been deduced that a small change ε in the Coriolis force from unity results in a perturbation of the critical mass by a factor of -8ε/81.
A Deep Visual-Red and Near Infrared Objective Prism Spectral Survey of the Milky Way
Authors: Kurtanidze O.M. , Nikolashvili M.G.
Published: July 2016

The deep visual-red and near infrared low dispersion (1250 Å/mm at Hɤ and 7000 A/mm at Å band) objective prism spectral survey of the Milky Way equatorial ten degree belt has been done by 70 cm meniscus telescope equipped with 2° prism (30° < 1 < 115° infrared).
Evolution of a 10MΘ Star With LMC Metallicities
Authors: Sree N. Rathna , Ray A.
Published: July 2016

Why stars become red giants has been a subject of investigation in many contexts, most recently in the discovery of the progenitor of the Supernova 1987A. Sanduleak 69°202 was found to be a blue supergiant star although it was generally presumed that type II SNe arise from red supergiants. Immediately after SN1987A, it was suggested that the blue spectral nature was due to lower metallicity in the LMC (Z = ZΘ/3 - ZΘ/4) although the existence of many red supergiants in the 30 Doradus region where SN1987A took place and in particular the observation of low-velocity nitrogen-rich gas presumed to be a circumstellar shell indicates that mass loss may also have played a significant role in bringing SK 69°202 from red to blue. We report here work in progress on the evolution of massive stars in the LMC with and without mass loss which can ultimately produce type II SNe.
Model Atmospheres with Periodic Shocks
Authors: Bowen G. H.
Published: July 2016

The pulsation of a long-period variable star generates shock waves which dramatically affect the structure of the star's atmosphere and produce conditions that lead to rapid mass loss. Numerical modeling of atmospheres with periodic shocks is being pursued to increase our understanding of the processes involved and of the evolutionary consequences for the stars. It is characteristic of these complex dynamical systems that most effects result from the interaction of various time-dependent processes. For example, rapid mass loss in the models is a joint consequence of the enormous extension of the atmosphere caused by shocks, and of radiation pressure on grains formed in the cool outer region; it is also affected by thermal relaxation processes, which determine the temperature distribution. The progress and significance of these modeling calculations will be reviewed.
Evolution of Oxygen-rich and Carbon Stars on the Asymptotic Giant Branch
Authors: Kwok Sun , Volk Kevin M. , Chan S. Josephine
Published: July 2016

For many years, it has been commonly believed that oxygen-rich (M) stars evolve first to S stars and then to carbon (C) stars. However, the details of the transition are not understood. It is now accepted that the overabundance of carbon ([C/O] > 1) in some asymptotic giant branch (AGB) stars is due to the dredge up of products of a capture and s-process elements after a number of thermal pulses (Iben 1975). Effects of convective overshooting and semiconvection in the dredge up process have also been considered (Castellani et al. 1985, Lattanzio 1986). The dredge up of carbon into the photosphere leads to the formation of carbon-based molecules, which absorption bands become the basis of spectral classification.

During the past decade, it is recognized that the carbon-richness of a star not only manifests itself in the photospheric spectrum, but also in the circumstellar environment as well. Probes of the circumstellar envelopes in the infrared and radio regions provide new means to characterize the chemical properties of the star. These methods are particularly useful in cases where the photosphere is heavily obscured by circumstellar absorption. Table 1 summarizes the photospheric and circumstellar spectral characteristics of M and C stars.
IRAS Infrared Fluxes of RV Tauri Stars
Authors: Bidelman William P.
Published: July 2016

Data resulting from the IRAS survey relating to the stars of the RV Tauri class have been examined. Of a total of 78 objects definitely assigned to this class in the 4th edition of the GCVS, 33 are to be found in the Point-Source Catalogue, and for six of these spectral data are available in the low-resolution Spectral Atlas (to 22.6 μm published by the IRAS Science Team (A & A Suppl. 65, 607, 1986). In the latter the pronounced difference in infrared emission between the carbon-rich star AC Her and most other RV Tauri stars, first noted by Gehrz in 1972, is striking, taking the form of a very marked continuation of that star's emission to at least 22 μm.
Carbon Stars With Oxygen-Rich Circumstellar Chemistry
Authors: Vardya M.S.
Published: July 2016

Ten new carbon stars with oxygen-rich circumstellar shells have been discovered using IRAS LRS spectral class. The origin of these objects have been briefly discussed. It is likely that they may be a consequence of release of oxygen due to carbon condensation, though other scenarios cannot be ruled out.
The Violet Flux Deficiency of Cool Carbon Stars
Authors: Luttermoser Donald G. , Johnson Hoilis R.
Published: July 2016

A characteristic feature of carbon star spectra is the dramatic decrease in energy flux toward the violet. This flux decreases faster toward shorter wavelengths in N-type carbon stars than in either M giants or blackbodies of the same usual color temperatures, and an unknown violet opacity source in these carbon stars has consequently been the subject of speculation for the past 60 years. We investigate this longstanding problem of the violet flux falloff in cool carbon stars by directly testing, through synthetic spectra, the effects of many new and previously suggested opacity sources, based on currently available model atmospheres for carbon stars and M-giant stars. While several bound-free edges of neutral metals are important opacities, those of Na I at 2413 Å, Mg I at 2514 Å, and Ca I at 2940 Å are especially significant. Collectively, thousands of atomic lines, and in particular, the neutral metal resonance lines are the primary cause of the violet flux falloff. The severe violet flux decrease begins in cool carbon stars shortward of 4500 Å, roughly coincident with the redward wing of the extremely strong Ca I resonance line 4227 Å. The enormous line of Mg I at 2852 Å is one of the largest opacity sources in the near-ultraviolet region of these stars and influences the spectrum well into the visible. The pseudo-continuum of C3 and the photodissociation continuum of CH both play noticeable but secondary roles. Other opacities that may affect the violet flux include the photodissociation of other hydrides, particularly NH and SiH, which have dissociation energies similar to CH. Synthetic spectra from the carbon-star models computed both with and without polyatomic molecules fit nicely to the collected observations of the well-observed carbon star TX Pse.
Pulsation and its rôle for circumstellar features
Authors: Heske A.
Published: July 2016

Circumstellar envelopes of cool giants and supergiants contain atomic and molecular gas, and dust. The charateristic spectral features of these different components can be observed at optical (atoms), at radio (molecules) and at infrared wavelengths (dust). Since the detection of circumstellar matter around giants and supergiants most studies concentrated on detemining mass loss rates from observations of a single component assuming steady mass loss during late stellar evolution. Nevertheless, the IRAS colour colour diagramme and evolutionary models rather point to a non steady evolution during the mass loss phase of the star.
A Unified Formula For Mass Loss Rate of 0 to M Stars and its Effect on Stellar Evolution
Authors: Tarafdar S.P.
Published: July 2016

A formula for stellar mass-loss rate has been derived using conservation equations of mass and momentum for coronal and continuous radiation driven wind. The derived mass-loss rate formula has been found to be consistent with the observed mass-loss rates for stars from 0 to M spectral type. Two constant parameters appearing in the mass-loss rate formula have been found to have values for special groups of stars like Be-stars and Wolf-Rayet stars different from each other and from the majority of stars. The effect of mass-loss according to the formula for the majority of stars on stellar evolution has been examined.
Report of the IAU Working Group on the Theory of Nutation
Authors: McCarthy Dennis D.
Published: July 2016

Modern observations of celestial pole offsets indicate that small but significant corrections to the current IAU theories of nutation and precession can be detected. These corrections are of the order of a few milliseconds of arc. To meet the needs of those who require millisecond of arc accuracy in reference frame applications, the International Earth Rotation Service (IERS) publishes in weekly and monthly bulletins the most recent observations, along with predictions of these corrections. These appear to meet the needs of users. In view of the fact that the geophysical community has not adopted a model which describes the nutation and precession theory and that the current procedure of the IERS meets the need of high-accuracy users, there does not appear to be a need to identify a new IAU nutation theory at this time.
The Celestial System and Frame of IERS
Authors: Arias E.F. , Feissel M.
Published: July 2016

The celestial system maintained by the International Earth Rotation Service is described in terms of physical properties of the fiducial objects, internal consistency of the frame, and agreement with the FK5 and dynamical systems.
Observations of the Planetary Satellites Europa and Titan by Hipparcos
Authors: Arlot J.-E. , Bec-Borsenberger A. , Dourneau G.
Published: July 2016

Observations of the satellites Europa and Titan will be obtained from the European Astrometric Satellite HIPPARCOS. These observations will be used to obtain “observed” positions of the planets Jupiter and Saturn; these positions have the advantages, first to be given in the reference frame defined by the Hipparcos system, and second, the accuracy on these positions is better than the accuracy of the ground-based observations of these planets. To obtain the positions of the planets from those of their satellites, we have to take the calculated positions of these satellites by means of their ephemerides. The accuracy of the computed positions of Europa and Titan relatively to their primary is of the order of 0ʺ.l, better than the one of the direct observation of Jupiter and Saturn. An efficient comparison of the different ephemerides of these planets will be possible that way.
Photographic Catalogue of 200000 Southern Stars – FOCAT–S
Authors: Bystrov N.F. , Polojentsev D.D. , Potter H.I. , Yagudin L.I. , Zalles R.F. , Zelaya J.A.
Published: July 2016

The catalogue of about 200000 stars in the zone from equator to southern pole was complied from photographic observations carried out during 1982 – 1969 years in USSR and Bolivia by Pulkovo astrograph (D=23 sm, F=230 sm, working field 4° × 4° ). The plates were measured by Zeiss Ascoreoord measuring mashines in Pulkovo, Tarija, and others observatories. The process of measurement and compilation of catalogue were carried out in Pulkovo by ES–1033 computer. The observations were made with a four–fold overlap of the sky. Reference oatalogue is SRS catalogue (FK5 system). The differencial refraction, differencial aberration and objective distortion were taken into account. The mean accuracy of catalogue FOCAT-S positions is ±0.123″.
Internal Precision in CCD Astrometry of QSO Optical Counterparts
Authors: Chiumiento G. , Lanteri L. , Lattanzio M.G. , Massone G.
Published: July 2016

The main purpose of this contribution is twofold. First, we report on a preliminary assessment of the astrometric properties of the CCD system we are presently using to extend the magnitude limit of the Torino program on optical positions of QSO’s. This assessment is based on the internal consistency of the positions derived from different CCD frames of the same objects. Then, we give a first evaluation of the precision of CCD derived QSO positions after extending a plate based reference frame (secondary frame) onto the CCD images (tertiary frame).

Special emphasis is given to comparisons with plate positions of the same faint objects. It is shown that use of the CCD camera promises a factor of five (or larger) improvement in the precision of QSO positions.
Influence of Systematic Differences of FK4 on Determining Earth Orientation Parameters
Authors: Wenjing Jin , Tongqi Xu , Peizhen Lu , Dechun Liao
Published: July 2016

In this paper the corrections of positions and proper motions (J2000) of FK4 were obtained. For different kinds of observational methods the formulae of calculating the influence of systematic differences of FK4 on time and latitude determinations were derived. The influence of systematic differences on the universal time and polar coordinates (1980–1988) of Chinese Joint System (CJS) and the global optical solution of earth orientation parameters (1987–1988) were calculated and their external precisions referred to BIH or IERS were also re–estimated.
Observations of Luni-Solar and Free Core Nutation
Authors: McCarthy Dennis D. , Luzum Brian J.
Published: July 2016

An analysis of the differences between observed nutation angles and the 1980 IAU Nutation Theory shows the existence of currently unmodeled effects. An empirical set of corrections to the 1980 IAU Nutation Theory is presented and compared with current geophysical models. A prograde periodic variation (period ≈ 420 days), which may be related to the theoretical free core nutation, is apparently seen.
The Extragalactic Reference Frame
Authors: McCarthy Dennis D. , Russell Jane , Archinal Brent , Carter Merri Sue , Florkowsi Dave , Holdenried Ellis , Johnston Ken , Yao Zhen-Guo
Published: July 2016

A cooperative program has been established to produce a reference frame of at least 400 suitable extragalactic sources. This is an extension of collaborative efforts (Johnston et al., Russell et al., Ma et al., and Reynolds et al.) reported at this meeting. In Phase One, a catalog of radio source positions will be constructed using original VLBI observations already obtained by NASA, NGS, NRL, JPL and USNO. Observations will be re-reduced in a consistent system to avoid some of the more serious problems associated with the formation of compilation catalogs. In Phase Two, the USNO will maintain the system, including the monitoring of source structure and/or variation. During both phases cooperation among the various agencies will continue. A list of sources will be made available to optical observers so that the frame will have benchmarks in both the optical and radio regimes.
Analysis and Synthesis of Catalogues of Extragalactic Radio Sources
Authors: Walter H.G.
Published: July 2016

Recent observation catalogues of extragalactic radio sources obtained by Very Long Baseline Interferometry agree in the mean to a few milliarcseconds (mas). Within this range the position differences show constant, linear and periodic offsets. To cast light on these offsets the differences between some of the representative observation catalogues are plotted. Especially, the periodic variations of declination differences of observation catalogues having significantly different epochs are tentatively explained by an uncertainty of the general precession in declination. In terms of the luni-solar precession this uncertainty is estimated to be of the order of −1to −2 mas per year.
Note on the Determination of the Neaely Diurnal Free Nutation (Core Nutation) and the Principal Term of Nutation Based on the Astrometric Data
Authors: Yatskiv Ya.S. , Kovbasyuk L.D.
Published: July 2016

Due to the highly accurate determination of the corrections to the nutation terms (the IAU-1980 nutation theory) by VLBI observations, the proposal for adoption of the new nutation theory or standard model of nutation is being discussed. At this point there are two unsolved problems:

(a)

VLBI observations can’t provide reliable estimates of the principal nutation term. The reason is that the correlation between this term and the precession constant is high due to the insufficient time span of these observations (about 10 years).

(b)

period of free core nutation (FCN) which depends on the ellipticity of the mantle-core boundary has not been, so far, reliably determined from direct observations.

In the present paper, we would like to draw attention to the results of the analysis of astrometric latitude and time observations which could be useful for resolving these problems.
Progress in First Tokyo PMC Program, 1985-1991
Authors: Yoshizawa M. , Suzuki S. , Miyamoto M.
Published: July 2016

Presented is a brief introduction to advances in the first Tokyo PMC program which began in 1985 and is to end in 1991.
New Initiatives for Synoptic Observations
Authors: Keller C. U.
Published: July 2016

Several new synoptic facilities for long-term studies of the Sun will become operational within the next few years. This paper summarizes information on some of these projects, in particular GONG+, ISOON, GOES/SXI, and SOUS. SOUS, the Synoptic Optical Long-Term Investigations of the Sun, is currently being built by the National Solar Observatory and will become operational in 2001. It consists of a 50-cm vector spectromagnetograph, a 14-cm full-disk patrol, and an 8-mm sun-as-a-star spectrometer.
Introduction to the Solar Space Telescope
Authors: Ai G. , Jin S. , Wang S. , Ye B. , Yang S.
Published: July 2016

The design of the space solar telescope (SST) (phase B) has been completed. The manufacturing is under development. At the end of 2000, it will be assembled. The basic aspect will be introduced in this paper.
The Large-Scale Magnetic Field and Sunspot Cycles
Authors: Makarov V. I. , Tlatov A. G.
Published: July 2016

Extended abstract

We report on the correlation between the large scale magnetic field and sunspot cycles during the last 80 years that was found by Makarovet al. (1999) and Makarov & Tlatov (2000) in H-αspherical harmonics of the large scale magnetic field for 1915–1999. The sum of intensities of the low modes 1 = 1 and 3, A(t), was used for comparison with the Wolf number, W(t). It was shown that the large scale magnetic field cycles, A(t), precede the sunspot cycles, W(t), by 5.5 years.

Let us consider the behaviour in time of the harmonics with low numbers 1 = 1 and 1 = 3. The radial component B(r) of the magnetic field may be expanded in terms of the spherical harmonics

whereθandϕare the latitude and longitude,are Legendre polynomials andandare coefficients of expansion on the spherical functions.

The magnetic moments of a dipole (1 = 1) and an octopole (1 = 3) are determined by the following equations:

Let us enter the parameter describing their intensity,
Cyclic Evolution of Sunspots: Gleaning New Results from Old Data
Authors: Solanki S. K. , Fligge M. , Pulkkinen P. , Hoyng P.
Published: July 2016

The records of sunspot number, sunspot areas and sunspot locations gathered over the centuries by various observatories are reanalysed with the aim of finding as yet undiscovered connections between the different parameters of the sunspot cycle and the butterfly diagram. Preliminary results of such interrelationships are presented.
Vector Magnetic Fields, Sub-surface Stresses and Evolution of Magnetic Helicity
Authors: Canfield Richard , Pevtsov Alexei
Published: July 2016

Observations of the strength and spatial distribution of vector magnetic fields in active regions have revealed several fundamental properties of the twist of their magnetic fields. First, the handedness of this twist obeys a hemispheric rule: left-handed in the northern hemisphere, right-handed in the southern. Second, the rule is weak; active regions often disobey it. It is statistically valid only in a large ensemble. Third, the rule itself, and the amplitude of the scatter about the rule, are quantitatively consistent with twisting of fields by turbulence as flux tubes buoy up through the convection zone. Fourth, there is considerable spatial variation of twist within active regions. However, relaxation to a linear force-free state, which has been documented amply in laboratory plasmas, is not observed.
Stokes Polarimetry at the Kodaikanal Tower Tunnel Telescope
Authors: Sankarasubramanian K. , Srinivasulu G. , Ananth A. V. , Venkatakrishnan P.
Published: July 2016

A Stokes polarimeter has been developed using a masked CCD arrangement for the measurement of the vector magnetic field of sunspots. Charge shifting within the CCD is used to record near simultaneous orthogonal polarisation. The testing of the Stokes polarimeter and the behavior of the integrated system combined with the Kodaikanal tower tunnel telescope will be discussed.
An Operator Perturbation Method of Polarized Line Transfer V. Diagnosis of Solar Weak Magnetic Fields
Authors: Nagendra K. N. , Frisch H. , Faurobert-Scholl M. , Paletou F.
Published: July 2016

We present an application of the PALI (Polarized Approximate Lambda Iteration) method to the resonance scattering in spectral lines formed in the presence of weak magnetic fields. The method is based on an operator perturbation approach, and can efficiently give solutions for oriented vector magnetic fields in the solar atmosphere.