bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ancient Chinese Auroral Records: Interpretation Problems and Methods
Authors: Teboul Michel 
Published: July 2016

AbstractIn recent years a number of auroral catalogues have been compiled from Oriental records, but the auroral identifications given vary greatly from one catalogue to another. This is due to the fact that, up to now, no reliable criteria have been found which could help us discriminate between auroral and non-auroral ancient records. In this paper two new criteria are propounded and their usefulness illustrated by the solution of a few currently much debated questions.
Space Distribution of Red Giants and the Galactic Structure
Authors: Ishida K. 
Published: July 2016

AbstractStellar content contributing to near IR radiation do not show radial differentiation in the Galaxy. Late-type giants and supergiants supply about 70% of the total volume emissivity at the K band, in the solar vicinity within 1 kpc, and also at the distance of several kpc in the Scutum region.
Stellar Population Synthesis and Star Counts to Constrain the Galactic Structure
Authors: Robin Annie , Creze Michel 
Published: July 2016

AbstractOur model of stellar population synthesis allows to derive synthetic star counts and distribution of colors, ages, and spectral types of stars in any given direction of observations. Here we compare results of the model with the distribution of stars in space and in absolute magnitude of stars of Gilmore and Reid. We find a small disagreement between observations of GR and predictions of our model in the space density of stars of 4 < Mv < 5. Ue show that this discrepancy can well be explained by a contamination of their sample of assumed main sequence stars by red giants and subgiants.
Photographic Photometry With Schmidt Plates of Star Clusters in the SMC
Authors: Kontizas M. 
Published: July 2016

The star clusters have always been the most important tools of testing the stellar evolution theories and when these stellar systems belong to other galaxies, then our knowledge on stellar evolution can be extended for different initial conditions than those of our Galaxy. The Magellanic Clouds being our nearest neighbour galaxies offer ideal conditions for such studies.Since the powerful southern telescope came into operation deep plates of these two galaxies revealed a large number of new star clusters. The Schmidt plates are most useful since they have the advantage of large field where many objects can be investigated homogeneously on the same plate.
Objective-Prism Redshifts of Faint Galaxies
Authors: Cooke J.A. , Kelly B.D. , Beard S.M. , Emerson D. 
Published: July 2016

AbstractA large sample of spectra of faint galaxies has been obtained using COSMOS measurements of UKST objective-prism plates. Computer software has been developed to obtain the radial velocities of large numbers of these galaxies automatically over a magnitude range of about B = 16 to 19. Initial tests have been performed on a sample of about 1400 galaxies from an area of about 5 x 4 degrees square.
Faint Galaxy Number Counts
Authors: Shanks T. , Stevenson P.R.F. , Fong R. , Gillivray H.T. Mac 
Published: July 2016

AbstractUsing photographic data obtained from the U.K. Schmidt and Anglo-Australian telescopes we have determined galaxy number counts in the range 17m≤B≤23m and 15mm≤R≤22m. By comparing our observations with models we find that the blue counts show strong evidence for galaxy luminosity evolution. We find that the red counts are better fitted by non-evolving models and that, here, the effects of the cosmological deceleration parameter, qo, and luminosity evolution are comparable. We discuss the implications of these results, with particular reference to the prospects of using the red counts to obtain constraints on qo.
XUV Absorption Spectra of Carbon Ions
Authors: Jannitti E. , Nicolosi P. , Tondello G. 
Published: July 2016

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.
Fine Structure of the 1s2s2p 4P0 and 1s2p2 4P Doubly Excited States of Lithiumlike Si XII
Authors: Buchet J.P. , Buchet-Poulizac M.C. , Denis A. , Désesquelles J. , Druetta M. , Martin S. , Ouerdane Y. 
Published: July 2016

AbstractThe ls2s2p4P0- ls2p24P transitions of Si XII have been investigated using fast ion beam spectroscopy in the far ultraviolet. The results for fine structure intervals and term separation represent the highest Z test of electron correlation effects and relativistic contributions in doubly excited states of lithiumlike ions.
Monochromatic X-ray and XUV Imaging with Multilayer Optics
Authors: Walker A.B.C. , Lindblom J. , Hoover R.B. , Barbee T.W. 
Published: July 2016

AbstractThe development of techniques for the fabrication of multilayer coated mirrors which can function as energy selective X-ray and XUV mirrors at normal incidence has greatly expanded the options available to the astronomical spectroscopist. We have developed a rocket spectroheliograph which utilizes multilayer optics in three configurations: i) As Cassegrain telescopes for imaging at 256 Å (He II) and 173 Å (Fe IX, X); ii) As tertiary mirrors used with a conventional Wolter I telescope for imaging at 44 Å (Si XI, XII), 173 Å, and 256 Å; iii) As off-axis spherical mirrors for imaging at 44 Å and 256 Å. We report on laboratory images and performance measurements obtained with these optical systems, and briefly on Solar Observations.
Euv Emission Line Ratios for Si IV in the Solar Transition Region
Authors: Keenan F.P. , Doyle J.G. 
Published: July 2016

AbstractTheoretical electron temperature sensitive emission line ratios in Si IV involving the 3d2D − 3p2P and 4s2S - 3p2P multiplets at ~1125A and 816A respectively are derived using R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for the ratio that includes the2D3/2, 5/2 −2p3/2 transition at 1128.3A. This is in contrast to the findings of Keenan, Dufton and Kingston, and provides support for the atomic data adopted in the calculations. However the2D3/2 −2pl/2 line at 1122.5A appears to be severely blended, as it leads to electron temperature estimates that differ significantly from that expected in ionisation equilibrium. The fact that the I(1122.5A)/I(1128.3A) intensity ratios determined from several flare spectra are closer to theory than that for the active region indicates that the blending is probably due to species with relatively low ionisation potentials, such as an Fe III transition at 1122.53A, as suggested previously by Burton and Ridgeley, and Feldman and Doschek. Electron temperatures deduced for a sunspot are much lower than that predicted from ionisation balance calculations, in agreement with earlier results, and imply that a cooling flow may be present.
Observed and Theoretical Spectra in the 10–100Å Interval
Authors: Brown W.A. , Bruner M.E. , Acton L.W. 
Published: July 2016

AbstractThe soft x-ray spectra recorded in two sounding rocket flights in 1982 and 1985 are compared with with predicted spectra. The poster presents the processed densitometer trace of the full spectrum together with the new spectrum from the 1985 experiment. This note compares the intensities of the lines with predictions.
Plasma Shifts of Ion Lines
Authors: Griem H.R. 
Published: July 2016

AbstractShifts due to interactions of radiating or absorbing atoms or ions with charged particles in a plasma are generally assumed to be negligible, e.g., in ments of atomic energy levels or in calculations of radiative transfer. However, it has long been known that electron collisions can cause shifts which are a significant fraction of the corresponding widths, and that ion-radiator interactions give rise to shifts and profile asymmetries through quadratic Stark effects and quadrupole corrections to the usual dipole interactions. The interplay between these various effects is particularly interesting for highly charged radiators for which electron effects are enhanced by the strong electron-radiator Coulomb attraction (plasma polarization shift). As examples, calculations for hydrogen- and helium-like ions will be discussed and be compared with measurements.
He-Like Titanium Spectra from Tokamak Plasmas
Authors: Kato T. , Masai K. 
Published: July 2016

AbstractX-ray spectra of titanium He- like ions from JIPPT-IIU, TFTR and DoubletIII tokamak plasmas have been analysed by the same computer code. The disagreements between measurements and theoretical calculations are discussed in terms of atomic processes.
The Two-Mirror Telescope (2MT)
Authors: Bingham Richard G. 
Published: July 2016

SUMMARYTwo eight-metre mirrors on an alt-azimuth mount are considered as a Future Large Telescope. The combined collecting area is ten times that of a four-metre class telescope, and the main modes of use are for optical spectroscopy and infrared imaging. In one square arc second, at 10µm wavelength, the telescope with adaptive auxiliary optics will yield 30 to 100 fully resolved image elements (not speckles). The mechanical arrangement proposed to give path length stability is to link the two tube centre sections along a horizontal axis and to use a total of four altitude bearings. A combined focus is necessary for the highest angular resolution, but other work such as spectroscopy can be carried out either at a combined focus or using separate instrumentation for the two eight-metre apertures. Twin prime and Cassegrain foci and horizontal Nasmyth platforms are intended for such pairs of spectrographs and other instruments, depending on their weight and field requirements. A pair of prime focus spectrographs with f/0.8 cameras is one appropriate system. (The horizontal Nasmyth platforms to accommodate larger spectrographs are a feature of this telescope which is not feasible in other MMT-type configurations). Another significant capability is that for a coud6-type light path from either aperture to the vertical axis. This can be achieved with four reflections (including the primary) for some applications. In addition to the conventional uses of the coudg light path, there is the possibility of using it to produce interferometric links to other telescopes. These links may be important as a future extension of the instrument.
C.F.H.T. Focal Reducer: Image and Multiaperture Spectroscopy
Authors: Fort B. , Lelièvre G. , Picat J.P. , Rio Y. , Vigroux L. 
Published: July 2016

Summary :In this poster paper we shortly present recent developpment and preliminary results obtained with the focal reducer of the Canada French Hawai 3.6 meter telescope with new trends for deep imagery and multiaperture spectroscopy.
The Nature of Galaxies and Clusters of Galaxies at Very Large Distances
Authors: Oke J.B. 
Published: July 2016

The previous speaker, Marie-Helene Ulrich, discussed several problems in extragalactic research which require the use of a very large ground-based telescope. She emphasized studies of relatively nearby objects. In my talk I will discuss problems which have to do with observations of objects at very large distances.Most studies of very distant objects involve studies of distant clusters of galaxies since this is one of the very few ways to pick a galaxy which is almost certainly very distant rather than a low-luminosity nearby object. Two exceptions are studies of radio and X-ray selected galaxies which very often are distant objects. Another exeption is the study of quasars which are almost all at very large distances. Even in these exceptions there is an interest in knowing whether these objects are associated with clusters or not.
Abundance Analysis of Alpha Ursae Minoris
Authors: Giridhar Sunetra 
Published: July 2016

AbstractWe have derived atmospheric abundances of the bright Cepheid a UMi in order to study the abundance anomalies in different elements. The atmospheric abundance of C, 0, Fe-peak elements Ca, Sc, Ti, Cr, Fe and heavier s-process elements Y, Ba, Ce and Sm have been derived using the method of spectrum synthesis. The abundance of carbon is derived using the C I lines in 4700A region, whereas for oxygen, the forbidden line at 6300.311A is employed. Abundances of the Fe-peak elements and s-process elements are obtained by synthesizing selected portions in the wavelength range 4330A - 4650A. The estimates of C/0 derived from the present investigation are compared with other Cepheids of similar period. The evolutionary status of a UMi is discussed in the light of these derived abundances.
Eight PopII Cepheids Recently Identified in Globular Clusters
Authors: Clement C. , Sawyer Hogg H. , Wells T. 
Published: July 2016

The University of Toronto 24-inch telescope at the Las Campanas Observatory of the Carnegie Institution of Washington has beerused for the study of variables in four southern globular clusters: NGC 6273=1119, NGC 6284, NGC 6293 and NGC 6333-M9.The first three of these clusters lie about 2° from one another in the sky at southern declinations ranging from about 24.5° to 26.5°. They were investigated by one of us (Sawyer 1943) using photographs obtained at the Steward Observatory in Arizona in 1939. A number of variables were discovered, but even with additional David Dunlap plates, it was not possible to determine any periods because of the large southern declinations. At Las Campanas (latitude 29°S), they pass close to the zenith and therefore the periods are more readily determined. From our Las Campanas data, we have found that there are four Cepheids in NGC 6273, two in NGC 6284 and one in NGC 6293.
Current Problems in Horizontal-Branch Theory: Some Implications for RR Lyrae Variables
Authors: Demarque Pierre 
Published: July 2016

There are a number of good reasons for wanting to improve our understanding of the structure and evolutionary status of horizontal-branch (HB) stars. To mention a few:1)The HB morphology of globular clusters can be used as a tool for studying the evolution of the galactic halo (Searle and Zinn 1978) and the time scale for halo collapse (Demarque 1980; Zinn 1980).2)HB stars offer an opportunity to evaluate the helium abundance of globular clusters. This can be done either by using the R-method (Cole et al. 1983) or the width of the RR Lyrae instability strip [Deupree 1977; but see also the paper by Stellingwerf (1984) in these preceedings which casts doubt on the validity of previous calculations of the dependence of the blue edge on helium content].3)HB stars may play an important role in understanding the integrated light of old stellar systems. In particular, blue HB stars seem to make a significant contribution to the ultraviolet light of elliptical galaxies. (Ciardullo and Demarque 1978; Gunn, Tinsley and Stryker 1981). At the same time, HB stars are believed to be the direct progenitors of asymptotic giant branch stars which have proved to be powerful tracers of stellar populations in nearby external systems (Blanco et al. 1980)4)The RR Lyrae variables are part of the HB population. One would wish to relate the observable properties of RR Lyrae variables to their chemical compositions and ages so as to use them: a) as distance indicators for galactic globular clusters (Sandage 1982a,b) and in the Magellanic Clouds; b) as tracers of stellar populations. This has been attempted for the galactic halo and disk by Sandage (1982a,b) and for the Magellanic Clouds by Butler et al. (1982).
Fourier Decomposition Parameters for the Halo RR Lyrae Variables U and V Caeli
Authors: Hansen L. , Petersen J. O. 
Published: July 2016

AbstractUBVRI light curves are obtained for the two halo RR Lyrae variables U Caeli with period 0.420 days (73 observations) and V Caeli with period 0.571 days (42 observations). It is shown that their light curve characteristics are very similar to those of field RR Lyrae stars.Fourier decompositions are studied for all five magnitudes and the resulting amplitude ratios and phase differences are discussed. The differences in the Fourier decomposition parameters between the five magnitudes are shown to be relatively small. Comparisons of the Fourier decomposition parameters for the two halo RR Lyrae stars with recently published data for field RR Lyrae stars show no systematic differences.
Cometary Orbital Dynamics and Astrometry
Authors: Yeomans D.K. 
Published: July 2016

AbstractComets are the only large solar system bodies where nongravitational forces directly affect their dynamic motions. Their approach to within a few AU of the Sun initiates the vaporization of nucleus ices, and the resulting rocket-like effects either add to or subtract from the comet’s orbital energy; the sign of the energy change depends upon the comet’s rotation direction and its spin pole orientation. The cometary outgassing phenomena have generally been modeled by assuming a rapidly rotating nucleus of water ice that outgasses symmetrically with respect to perihelion. Although this nongravitational acceleration model has been quite successful in providing accurate orbits and ephemerides, several comets exhibit water production rates and visual light curves that are noticeably asymmetric with respect to perihelion. New asymmetric models are being developed that attempt to represent more closely the cometary outgassing phenomena. For the same comet, derived nongravitational parameters can differ widely, depending upon which model is used to fit the astrometric data. The uncertainties in the data and in the nongravitational acceleration model prevent realistic extrapolations of these objects’ motion beyond a few hundred years, particularly if close planetary encounters are involved. Accurate orbits, ephemerides and efforts to model the nongravitational effects ultimately depend upon the quality of the astrometric data. Using a combination of long-focus telescopes, charge coupled device (CCD) detectors, microdensitometer reductions and modern star catalogs, cometary astrometric data can be generated that are accurate to the sub arcsecond level. While occultation, spacecraft, and radar observations can provide powerful astrometric data when available, it is still the ground-based optical observations that must provide the vast majority of data for cometary astrometry in the foreseeable future.
Infrared Techniques for Comet Observations
Authors: Hanner Martha S. , Tokunaga Alan T. 
Published: July 2016

AbstractThe infrared spectral region (1–1000μm) is important for studies of both molecules and solid grains in comets. Infrared astronomy is in the midst of a technological revolution, with the development of sensitive 2–dimensional arrays leading to infrared cameras and spectrometers with vastly improved sensitivity and resolution. The Halley campaign gave us tantalizing first glimpses of the comet science possible with this new technology, evidenced, for example, by the many new spectral features detected in the infrared. The techniques of photometry, imaging, and spectroscopy are reviewed in this chapter and their status at the time of the Halley observations is described.
Debris from Comets: The Evolution of Meteor Streams
Authors: Mcintosh Bruce A. 
Published: July 2016

AbstractThe evolution of meteor streams is controlled basically by: (a) the initial velocities with which the particles were ejected from the parent body; (b) gravitational perturbations by the planets; (c) radiation forces; and (d) collisions. This review focuses mainly on recent numerical modelling dealing with (b) and (a).Ejection velocities spread the particles around the orbit, closing the ring in a few tens of revolutions. The greater ejection velocities of smaller particles cause more rapid dispersion both around the orbit and in the cross section.A determination of the effects of gravitational perturbations must take into account the distributed properties of the stream. The stream’s evolution is dependent on the short-term impulse nature of planetary perturbations, as well as on long-term secular effects. The combined effects produce complex stream cross-sections as in the ribbon-like form of the Halley stream (Orionid and η Aquarid showers) or as in the changes in the annual position of peak shower activity shown by the Quadrantids. Perturbations may cause the orbit of a parent body to sweep rapidly across the orbit of the Earth. But the associated particle stream may not be lost as a meteor shower because it tends to become dispersed in a manner that ensures a continuing supply of particles in Earth-crossing orbits. The nodes of the observed meteoroid orbits may show very little motion compared with the rapid motion of the nodes of the orbit of the parent object.Radiation effects contribute to size separation of particles. Very small particles are blown out of the stream or spiral in toward the sun because of Poynting–Robertson drag. Older meteor streams usually show a predominance of large particles.
Physical Aging in Comets
Authors: Meech Karen J. 
Published: July 2016

AbstractRecent evidence suggests that comets formed at low temperatures (≤ 25 K) and that, while the interiors have not been considerably altered since formation, the outer layers have undergone substantial modification. Comets exhibit a wide range of physical characteristics, some of which may be attributed to systematic physical differences between comets making their first close approach to the Sun from the Oort cloud (new comets) and those having made many approaches (old comets). These differences may reflect either primordial differences between two populations or the differences may be a manifestation of aging processes. There are many processes that might be responsible for causing aging in comets. These include: (i) radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, (ii) processing from heating and collisions within the Oort cloud, (iii) loss of highly volatile species from the nucleus on the first passage through the inner Solar System, (iv) buildup of a dusty mantle, which can eventually prohibit further sublimation, and (v) a change in the porosity, and hence the thermal properties of the nucleus. Although Oort’s (1950) original work on the comet cloudrequiredthat new comets fade after their first close passage, past searches for evidence of aging in comets have produced conflicting results, partly due to a lack of systematic data sets. An understanding of the evolutionary processes of comet nuclei that give rise to compositional or physical differences between ‘fresh’ Oort cloud comets and thermally processed periodic comets will improve our knowledge of the possibly primordial comet composition and therefore conditions in the early Solar System. Recent observations suggest that there are distinct differences between the two groups with respect to intrinsic brightness and rate of change of activity as a function of distance.