bluuebunny/crossref_metadata_2025_split huggingface dataset:
Meridian Observations at Santiago, Chile
Authors: Anguita C. , Carrasco G. , Loyola P. , Šiškina V.N. , Zverev M.S. 
Published: March 2016

Observations of the Southern Reference Star (SRS) and Bright Star (BS) programmes were started in January 1963 with the Repsold meridian circle of the Santiago Observatory. Up to July 1, 1967, a total of 86725 star observations arranged in 1520 series had been observed.In order to investigate the instrumental system, series of fundamental stars between +41° and −69° SP were included in the observing programme. A total of 214 such series were observed, 123 being with ‘clamp East’ and 91 with ‘clamp West’. The number of individual star observations in these 214 series was 7344. These observations were reduced using Bessel’s formulaα = T + (u + m) + n tan δ + c′ sec δ,where u denotes the clock correction and c′ includes the collimation error, diurnal aberration and the contact width.
Theories Proposed to Explain Quasi-Stellar Objects and Radio Galaxies
Authors: Burbidge Geoffrey 
Published: March 2016

In this paper I shall consider briefly two major questions. The first is concerned with whether the QSO’s are at cosmological distances or not. The second is concerned with the theoretical models proposed to explain the observed properties of radio galaxies and quasi-stellar objects.In the Invited Discourses Dr. Sandage and Sir Martin Ryle gave arguments which lead them to believe that the QSO’s lie at cosmological distances. They both have strong convictions in this matter. However, Dr. Sandage did remark that he was only giving one side of a ‘great debate’. It is presumably up to me to give the other side of this argument. I have no strong beliefs in this matter but it appears that on the basis of the evidence as it is today we cannot reasonably assert that the QSO’s are at cosmological distances.
High Resolution Interferometry of Cool Stars
Authors: Lambert D. L. 
Published: March 2016

AbstractThis paper reviews results obtained in a program of high resolution infrared spectroscopy of K and M giants. The reported results include (i) a preliminary analysis of the C, N and O abundances for α Ori, (ii) determinations of the 12C/13C and 16O/18O ratios for α Ori (12C/13C ~ 6 and 16O/18 ~ 500), (iii) the derivation of a lower limit, 16O/18O≳ 300, for the 160/18O ratio in α Boo, (iv) a discussion of observations of the SiO first-overtone vibration-rotation bands in M stars, and (v) a search for the fundamental quadrupole vibration-rotation lines of H2.
Spectrophotometry of Supernovae
Authors: Kirshner R. P. 
Published: March 2016

AbstractAbsolute spectral energy distributions for supernovae of both types I and II have been obtained. These observations demonstrate three facets of supernova spectra. First, both SN I’s and SN II’s have a continuum that varies slowly and uniformly with time, and which carries the bulk of the radiated flux at early epochs. Second, some lines in both SN I’s and SN II’s have P Cygni profiles: broad emissions flanked on their violet edges by broad absorptions. Third, some lines are common to SN I’s and SN II’s and persist throughout the evolution of the spectrum. The continuum temperatures for both SN I’s and SN II’s are about 10000 K at the earliest times of observation and drop in one month’s time to about 6000 K for SN II’s and about 7000 K for SN I’s. After several months, the continuum may cease to carry the bulk of the flux, which might be in emission lines, but continues to exist, as shown by the presence of absorption lines. The P Cygni line profiles indicate expansion velocities of 15000 km s-1 in SN II’s and 20000 km s-11 in the SN I 1972e in NGC 5253. Line identifications for SN II’s include Hα, Hβ, H and K of Ca II, the Ca II infrared triplet at λ8600, the Na I D-lines, the Mg I b-lines at λ5174, and perhaps Fe II. The [O I] lines λλ6300, 6363 and [Ca II] lines λλ7291, 7323 appear after eight months. For SN I’s, the lines identified are H and K of Ca II, the infrared Ca II lines, the Na I D-lines, and the Mg I b-lines. There is some evidence that Balmer lines are present two weeks after maximum. The strong and puzzling λ4600 features drifts with time from λ4600 near maximum light to λ4750 after 400 days.
On the Magnetospheres of Jupiter, Saturn, and Uranus
Authors: van Allen James A. 
Published: March 2016

A brief descriptive summary of Jupiter’s magnetosphere is based on in situ observations with the spacecraft Pioneer 10 and Pioneer 11 in November-December 1973 and November-December 1974, respectively. Current interpretative work emphasizes particle acceleration and loss mechanisms, the determination of diffusion coefficients by satellite effects, the topology of the outer magnetosphere, the possible recirculation of energetic particles, and the controversial evidence for an extended magnetotail.Available evidence on non-thermal radio emissions of the planet and on the solar wind flow at 10 AU is invoked to suggest that Saturn very likely has a large, well developed magnetosphere resembling that of Jupiter but with the important difference that a radiation belt can not exist interior to the outer edge of the A ring of particulate matter. The first in situ observations will be made by Pioneer 11 in August-September 1979.
Small Magnetostatic Flux Tubes
Authors: Spruit H. C. 
Published: March 2016

In an attempt to interpret the observed properties of small scale magnetic fields at the solar surface, a set of models has been calculated based on the assumption of a magnetostatic equilibrium. The basic assumptions made are:
i.The observed magnetic elements are magnetostatic flux tubes.ii.The efficiency of convective heat transport inside the tube is reduced with respect to that in the normal convection zone; the horizontal convective heat transport in the tube is suppressed completely by the magnetic field.iii.Close to the tube, horizontal convective heat transport is reduced due to the proximity of the magnetic field.
Ultraviolet Observations of Normal Galaxies
Authors: Bertola Francesco 
Published: March 2016

AbstractThe UV spectrum of galaxies provide us with the unique chance to detect those hot stellar components, which normally do not appear in the visible spectrum. Such components, interpreted as possibly due to horizontal-branch stars, have been found in spectra of early-type galaxies. All these spectra exhibit an UV excess shortward of 3000 A with respect to the energy distribution of a K-type star. UV excess is present in different amount also in spectra of late-type galaxies, but the data are fragmentary.There is hope to define a standard UV spectrum of nearby elliptical galaxies to compare with that observed in the visible region in distant galaxies. This would allow the determination of the evolutionary effect.The emission lines in elliptical galaxies are found much stronger than one would expect if the physical conditions are similar to those of HII regions.Direct images of galaxies allow to trace the spiral structure defined by hot stars and to study the UV luminosity profile in the nuclear region.
Stellar Wind Theories
Authors: Hearn A. G. 
Published: March 2016

The term stellar wind is used nowadays to describe any more or less continuous mass loss from a star. With the observations made with satellites in recent years it is becoming clear that most stars are undergoing this form of mass loss, though its magnitude can be very different from one star to another. The term stellar wind does not include the more eruptive forms of mass loss such as novae, the ejection of mass in shells or mass loss as a result of flares.Stellar winds are maintained by energy and momentum deposited in the outer layers of a stellar atmosphere. The deposition of energy causes the heating of a chromosphere and corona, so that the theory of stellar winds cannot really be separated from the theory of coronal heating. Energy and momentum can both be deposited by the same mechanism. For example if a corona is heated by the dissipation of a wave which deposits energy, the same wave can change the momentum of the mean flow through wave pressure and this can happen even in the extreme case of no dissipation of the wave.The foundation of the theory of stellar winds was laid by Parker (1958) in his theory of the solar wind. A useful review of this work has been given by Parker (1965). The theory of the solar wind in its simplest form is deduced from the equation of motion combined with the equations of continuity and state.
Mass-Loss From Spinning Stars
Authors: Sreenivasan S. R. 
Published: March 2016

AbstractThe effects of mass-loss and angular momentum loss on the evolution of massive stars are discussed bringing out the main results as well as the limitations of recent studies. It is pointed out that an acceptable theory of stellar winds in early as well as late type stars is needed as well as a satisfactory assessment of a number of instabilities in these contexts for an adequate understanding of the evolutionary consequences for a wide variety of population I and polulation II stars, which are affected by mass-loss.
By Draconis and RS Canum Venaticorum Stars: The Discoveries of Classical Photometry and Spectroscopy
Authors: Bopp Bernard W. 
Published: March 2016

Physically quite dissimilar, the BY Dra and RS CVn stars have the common characteristic of extraordinarily high levels of stellar surface activity.The RS CVn group, as defined by Hall, consists of detached binaries both components of types F, G, or K. The orbital periods are from a few days to a few weeks, and the mass ratios are generally near unity. Spectroscopically, the stars are remarkable in that they show very strong Ca II H and K emission outside eclipse. Masses and radii are known for many of these systems; physical parameters indicate these systems contain a moderately evolved subgiant, with mass slightly greater than 1 M⊚. The ages (which may be verified by data on visual companions) are a few 10 years.In contrast, the BY Dra variables are late-type dwarfs, with spectral types ranging from dK5e to dM4e. The e designation indicates the presence of Balmer emission, which is generally visible in moderate strength at Ha and only very weakly present in the blue. The BY Dra stars do exhibit strong emission at H and K, however, and also show UV Ceti-type flares. Approximately 75% of the BY Dra variables are known as double-line spectroscopic binaries.
Star Formation in Disks
Authors: Larson Richard B. 
Published: March 2016

The basic characteristics of the stellar populations in galaxies are determined by the history of star formation and by the initial mass spectrum with which the stars are formed. Many attempts have been made to model the history of star formation in galaxies using various quasi-theoretical descriptions of star formation, but star formation remains a very poorly understood process and no theoretical understanding with any real predictive power has yet been attained. However, recent work suggests the importance for star formation of some mechanisms that have so far not been very extensively studied, and I shall mention some of these possible processes here, undeveloped though these ideas still are at present.First, I shall review briefly the observational evidence concerning the history of star formation in galaxies of different Hubble type. Most of the information we have for galaxies other than our own comes from their colors, which can be compared with the predictions of models constructed with various assumed histories of star formation. Ever since the work of Tinsley (1968), it has been clear that most of the observed variation of color with Hubble type can be understood in terms of differing time scales for star formation, the reddest galaxies (E and SO) having formed the bulk of their stars at a relatively early stage, while the much bluer Sc galaxies have formed their stars much more gradually and at a rate that has remained nearly constant up to the present time. Recent studies of normal elliptical galaxies, reviewed by Faber in this volume, confirm that they have no detectable present star formation.
Asteroids: Spins and Shapes
Authors: Lagerkvist Claes-lngvar 
Published: March 2016

AbstractThere is a difference in rotational properties between asteroids of various taxonomic types. The M and CMEU asteroids increase their spin with diameter and rotate much faster than asteroids of types C and S of the same diameter do. There is a difference in spin between the C and S types but the faster spin for the S asteroids larger than 150 km in diameter is probably not statistically significant. For both C and S asteroids the spin increases with diameter, but in a much less pronounced fashion than for types M and CMEU. The curve for the S asteroids is remarkably flat for asteroids smaller than 100 km.The CMEU asteroids are more irregular than other types of asteroids. Both C and S asteroids have larger amplitudes for diameters about 100 km.The family asteroids smaller than 100 km in diameter have a faster spin than non-family main-belt asteroids of the same size. Family asteroids show an increase of spin and lightcurve amplitude with decreasing diameter.
Radio Active Nuclei
Authors: Kellermann K. I. 
Published: March 2016

For the purpose of this survey we shall use the term radio active nucleus to refer to compact radio sources which are found in galactic nuclei and which show activity either in the form of flux density variations or outward flow of material from the nucleus. There is great similarity between the observed properties of radio active nuclei with those of radio active quasars, and it is widely supposed that the quasar phenomena represents an extreme case of an active galaxy. In this paper however, we shall concentrate on compact radio sources found in the nuclei of identifiable galaxies, and quasars are discussed only to the extent that they help to understand the origin and evolution of radio active galactic nuclei.Since radio active nuclei are typically in extent, they can be mapped only with VLBI techniques. Detailed maps are available for only a few of the strongest nuclei, but a much larger number can be identified from conventional interferometry with a resolution ~ 1”. In the few radio galaxies where most of the observed radio flux comes from the active nucleus, activity is observed directly on a time scale of months or even weeks. In others, it may be inferred from arguments based on synchrotron lifetime.
High Velocity Gas in the Galactic Halo and Disk
Authors: de Boer Klaas S. 
Published: March 2016

The progress in the understanding of the high velocity component of the interstellar medium is reviewed. Emphasis is on the velocities seen outside the plane of the Milky Way, of gas in the galactic halo.The extensive measurements of interstellar absorption lines in the late 1930’s demonstrated that the “stationary” lines in stellar spectra were extremely narrow and in many cases showed fine structure at the 10 km/s level. The quantisation of these data had to wait until about 1950. Adams (1949) presented data on Ca II lines toward some 300 stars and his compilation, supplemented with Na I data, led Routly and Spitzer (1952) to investigate the systematics of the Ca and Na abundances. Contrary to the non-solar abundance ratio of the majority of the interstellar clouds, the “high velocity” absorptions, defined by Routly and Spitzer as differing in velocity by more than 20 km/s from the local standard of rest, showed a near solar Ca/Na abundance ratio.
Earth Rotation Variations from Hours to Centuries
Authors: Dickey Jean O. 
Published: March 2016

AbstractThe study of Earth rotation encompasses the complex nature of orientation changes, the excitation of these changes and their geophysical implications in a broad variety of areas. Studies have embarked on a new era with the advent of highly accurate space geodetic techniques and the increasing availability of complementary geophysical data sets. This paper provides an overview of Earth rotation variations from hours to centuries with a brief discussion of polar motion and nutation results.
Precise Observations of Luni-Solar and Free Core Nutation
Authors: McCarthy D.D. , Luzum B.J. 
Published: March 2016

AbstractThe previous analysis of McCarthy and Luzum (1991b) is repeated using an additional three years of VLBI observations. A new set of empirical corrections to the 1980 IAU Nutation Theory is determined and compared to current geophysical models.
The Effective Temperature Determination
Authors: Cayrel Roger 
Published: March 2016

The content of my oral contribution has been reduced here to a guide to the recent litterature on the subject.The effective temperature of a star can be obtained directly by measuring the total flux received on earth from it, and its angular diameter. In principle interferometrie methods could determine both the limb-darkening law of the stellar disk and the angular diameter of the disk. In practice, in order to obtain a decent accuracy on the angular diameter, interferometrie methods have so far borrowed the limb-darkening law from stellar atmosphere theory, in order to concentrate all the observational information on a single parameter. The total number of stellar diameters and effective temperatures obtained by this basic method remains very small (about 30 stars) and concerns exclusively giant or subgiant stars. The reader is invited to look at the following references and those therein (Di Benedetto 1993, Mozurkewich et al. 1991, Alonso et al. 1994). Smalley and Dworetsky (A&A in press) have reinvestigated the old Code et al. (1976) calibration with more recent spatial UV data, for B, A, and F stars, and have found no significant changes. The accuracy of the basic method is at the best of the order of 1.5 %, and there is a deep need for more data, and for doubling the current accuracy. Actually there is a strong effort for developping interferometry both from the ground (ESO VLTI, USNO astrometric interferometer) andfrom space (OSI project, Colavita et al. 1993; GAIA project at ESA). So there is hope for a not to far future.
Status of Agn Unification Models
Authors: Barthel P.D. 
Published: March 2016

Unification of Active Galactic Nuclei is obviously multidimensional. Dimensions include the mass and angular momentum of the postulated central black hole, the mass accretion rate through the accretion disk surrounding the black hole, and the orientation of this central engine plus associated dust with respect to the line of sight (e.g., Blandford 1990). As for orientation related unification, considerable progress has been made over the past decade. This review will deal with this geometric unification.Mechanisms in AGN include:1.relativistic beaming in radio jets (as manifested by rapid variability from radio to ϒ-rays, superluminal motion, synchrotron self-Compton2.emission by an optically thick, non-spherical body (e.g., hot accretion disk);3.external collimation and shadowing by an anisotropic dust distribution (as manifested by the existence of hidden continua, observed through polarization or photon deficit in extended emission line regions, and hidden broad line regions, observed through polarization or in the less opaque near infrared part of the spectrum).These anisotropic mechanisms introduce selection biases, they lead to incorrect inferred luminosities and make us overestimate the AGN diversity. They furthermore imply unification at some level.
The FUSE Mission: Atomic Data Needs in the 900–1200 Å Spectral Region
Authors: Sembach Kenneth R. 
Published: March 2016

AbstractThe Far Ultraviolet Spectroscopic Explorer (FUSE) is presently producing high resolution (R ∼ 20,000) absorption-line spectra of astronomical objects ranging from Solar System planets to quasars. The 900-1200 Å spectral region observed by FUSE is exceedingly rich in atomic and molecular transitions arising out of the ground state. It is already clear from early FUSE observations that the atomic data (e.g., oscillator strengths) for some transitions are considerably different than those predicted by theoretical calculations. I briefly describe the most pressing oscillator strength needs in this wavelength range for studies of the interstellar medium.
Comparison of Nutation Theories
Authors: McCarthy Dennis D. 
Published: March 2016

AbstractAnalyses of residuals between VLBI observations and combinations of nutation series show that the MHB 2000 nonrigid-Earth nutation model applied to the REN 2000 rigid-Earth model results in the best fit, and that amplitudes of any possible periodic terms remaining in the observed corrections to the MHB2000 theory could be expected to be less than 0.1 mas.
Astrometry of Outer Solar System Bodies with Small Telescopes
Authors: Tichá J. , Tichý M. 
Published: March 2016

AbstractAstrometry for an accurate orbit determination of distant objects is usually made with large telescopes ranging from 2 to 10 meters. In selected cases the bright(er) part of their population has been effectively observed with small 0.6 to 1 meter class telescopes. We point out here methods and techniques used at the Kle Observatory including our results. The extension of this programme using a new larger telescope is in preparation. We also mention a possibility of using some web tools for call for follow-up.
On a Physical Mechanism for Extra-Mixing in Globular Cluster Red Giants
Authors: Denissenkov Pavel A. , Tout Christopher A. 
Published: March 2016

AbstractFor the first time we propose a real physical mechanism for extra-mixing in red giants which can quantitatively interpret all the known star-to-star abundance variations in globular clusters. This is Zahn’s mechanism (Zahn 1992; Maeder & Zahn 1998). It considers extra-mixing in a radiative zone of a rotating star as a result of joint operation of meridional circulation and turbulent diffusion.
Earth Orientation since AD 1600
Authors: McCarthy Dennis D. 
Published: March 2016

AbstractPast endeavors in the field of Earth orientation have provided both service to astronomical users of the data and insight into the physical processes of the planet Earth. Since the study of Earth orientation has required a wide geographic distribution of astronomical observing sites, it has been an area of research that has depended heavily on international cooperation over long intervals of time. Recently, IAU Colloquium 178 pointed out that the need exists to find and collect observations that may have been made before the establishment of the current operational services. Reanalysis of such data could be important in our understanding of the physical processes affecting the Earth. All of these observations need to be analyzed in one system consistent with current definitions and conventions. The history of available observations is reviewed along with the contributions that have been made possible using these data. Possible sources for additional data are suggested.
Io’s Volcanos: Latest Results from Galileo and from the Earth
Authors: Spencer John 
Published: March 2016

AbstractThree recent close flybys of Io by the Galileo spacecraft, and new observations from the Hubble Space Telescope and ground-based telescopes, have greatly advanced our understanding of Jupiter’s volcanic moon Io. Io’s volcanos are much hotter than previously suspected, perhaps requiring exotic silicate magma compositions. Despite much new data, Io’s largest volcano, Loki, is still poorly understood. New data on Io’s plumes suggest the existence of two types of plumes: primary plumes, relatively rich in S2 gas, which are emitted where magma first reaches the surface, and secondary plumes, more SO2 rich, which result from interaction of lava flows with a volatile-rich substrate.