bluuebunny/crossref_metadata_2025_split huggingface dataset:
The OPAL opacity Code
Authors: Rogers F.J. , Iglesias C.A. 
Published: March 2016

The OPAL opacity effort was undertaken in 1985 in response to speculation that the existing opacity data were not of sufficient accuracy to model observed stellar properties. We have taken the view that a completely new code with improved equation of state, atomic physics and line broadening was required. It was apparent that the most computationally intensive part of the calculations would be to obtain the vast amount of atomic data needed for the bound-bound and bound-free absorption cross-sections. To meet this challenge we developed a parametric potential method, that was fast enough to allow on-line calculations, while achieving accuracy comparable to that of the single-configuration Dirac-Fock method. This on-line capability was also chosen to allow flexibility to study the effect of various coupling and data averaging methods. It also makes it easy to study the effect of adding more elements.The OPAL equation of state is based on the many-body statistical mechanics of partially ionized plasmas in the grand canonical ensemble. This is the so-called “physical picture” method. In this approach one works directly with the electrons and nuclei present in the plasma. The effect of the plasma environment on the internal states is obtained directly from the statistical mechanical analysis. A convergent partition function is a natural consequence of this approach.OPAL includes degeneracy and plasma collective effects in the free-free absorption using a screened form of the parametric potentials. Similar corrections to the Thomson scattering are obtained from the method of Boercker (1987). The spectral line broadening for one, two and three electrons ions are obtained from a suite of codes provided by R.W. Lee (1988) that include linear Stark theory. For all other transitions we use Voigt profiles where the Gaussian width is due to Doppler broadening and the Lorentz width is due to the natural width plus fits to the electron impact collision width (Dimitrievic and Konjevic 1980).
Data for Weak Lines
Authors: Hibbert A. 
Published: March 2016

Weak lines, being unsaturated, are particularly important for the determination of interstellar abundances of elements. From a theoretical point of view, there are several possible causes of an electric dipole transition having a small oscillator strength. In some cases, several contributions to the dipole matrix element substantially cancel (e.g. the 1808 Å line Si II), while in other cases, the oscillator strength would be zero but for the inclusion of small relativistic effects (e.g. the intersystem 1909 Å line in C. II).For weak lines, the interstellar abundances depend on the oscillator strength (calculated or measured) and the equivalent width (observed). The increased resolution of the Goddard High Resolution Spectrograph on board the Hubble Space Telescope provides for many lines equivalent widths of much greater precision than was previously available. This situation presents a challenge to theorists to improve the quality of their calculations of oscillator strengths.Such calculations are difficult for weak transitions, especially when the cause is cancellation. Of course, with larger and more powerful computer a vailable, it is possible to undertake more extensive calculations. But the quality of observational data now makes it imperative for theorists not merely to do a better calculation than before, but to give a considered estimate of the accuracy of the results. Since there are no effective theoretical methods for obtaining rigorous bounds to oscillator strengths which could give a useful guide to accuracy, theoretical estimates of accuracy can be achieved only by undertaking a systematic sequence of calculations of increasing complexity, while ensuring that no significant contributions to the calculations are omitted.
Astronomy in Algeria
Authors: Sadat R. 
Published: March 2016

Astronomy in Algeria is linked to the Algiers Observatory which is the only place where there is any astronomical activity. The Observatory was built in 1889 and was an important contributor to the famous Carte du del project. After independence, because there were so few Algerian astronomers and the site had deteriorated, the activity of the Observatory slowed down significantly.In 1980, the year of the violent El-Ansam earthquake, a decision was taken, on the initiative of the present director (M. Benhallou, Professor of Seismology) to create an Algerian earthquake-surveillance network. This led to the creation of the research centre CRAAG (Centre de Recherche en Astronomie, Astrophysique et Geophysique) in which I’Observatoire d’Alger and the Institut de Physique du Globe have been merged. Thus, the Algiers Observatory has become more and more devoted to geophysical research. Towards the end of the 1980s, a group of Algerian astronomers, educated in foreign universities, joined CRAAG. The most recent recruit came in 1991. Today, the Department of Astronomy and Astrophysics contains ten members—nearly half the total number of Algerian astronomers.
The Question of Presolar Components within Interplanetary Dust Particles (IDPs) Collected in the Stratosphere
Authors: Bradley John P. 
Published: March 2016

AbstractInterplanetary dust particles (IDPs) are from asteroids and comets, and they are the smallest and most fine-grained meteoritic objects available for laboratory investigation. Cometary IDPs are of special significance because they are presently the only samples of comets, and comets are expected to be enriched in preserved solar nebula and presolar components. These components may include not only cosmically rare refractory circumstellar grains(e.g. SiC) that are recovered from meteorites but also cosmically abundant interstellar silicates and carbonaceous grains that were the fundamental building blocks of the Solar System. D/H ratios measured in IDPs are consistent with the survival of interstellar carbonaceous material, and some IDPs contain glassy grains with properties similar to those of interstellar “amorphous silicates”. Submicrometer forsterite and enstatite crystals in IDPs resemble circumstellar silicates detected by the Infrared Space Observatory (ISO). ISO also detected a broad ~ 23 µm feature around several stars, and a similar feature observed in IDP spectra is due to submicrometer FeNi sulfide grains, suggesting that sulfide grains may be a significant constituent of astronomical dust.
The FERRUM Project: Oscillator Strengths of the Iron Group Elements: Fe II
Authors: Johansson Sveneric 
Published: March 2016

AbstractWe report on an international collaboration, the FERRUM Project, which aims at extending the database of experimental oscillator strengths for iron group elements and possibly evaluating theoretical and astrophysical data. The selection of individual projects is made with respect to their relevance for abundance work and plasma diagnostics in astrophysics. In this paper we present recent measurements of gf-values in Fe II. We also report on the first measurements of forbidden lines of the same spectrum, [Fe II].
UV Studies Related to the Physico-Chemistry of Planetary and Cometary Environments
Authors: Gazeau M.-C. , Benilan Y. , Cottin H. , Vuitton V. , Jolly A. , Raulin F. 
Published: March 2016

AbstractThe complex organic chemistry involved in comets and planetary atmospheres can be better understood via comparison between observations and results obtained by models. In this paper, we point out some lacks in chemical schemes used in models that can be responsible for the discrepancies between observational and theoretical data. Then, we propose UV studies (coupling experimental and theoretical approaches) to be developed in order to determine fundamental parameters: absorption cross sections, quantum yields and rate constants which will be used to improve models as well as to better analyse and interpret observations.
New Definition for the Celestial Pole and the Celestial Origin in the ICRS
Authors: Capitaine Nicole 
Published: March 2016

AbstractTwo Resolutions have been submitted to the 24thGeneral Assembly of the IAU concerning the definition and use of the celestial pole of reference and the celestial origin. The aim of both resolutions is to provide new parameters for Earth rotation which are consistent with the properties of the International Celestial Reference System (ICRS), adopted from 1 January 1998 as the IAU celestial reference system. The definition of the parameters have also to be consistent with the precision and the temporal resolution of the current Earth rotation measurements as well as with the theory for nutation and polar motion at the microarcsecond level. This paper explains the basis of the resolutions as well as their practical application. One of the resolutions defines the “Celestial Intermediate Pole” (CIP) in order to replace the “Celestial Ephemeris Pole” (CEP) for the new IAU precession-nutation model; its specifies the way for taking into account the constant offset from the ICRS and the high frequency terms in polar motion and nutation. The other resolution recommends the use of the “non-rotating origin” (Guinot 1979) on the moving equator, for defining Earth rotation and UT1; it also recommends the use of the celestial and terrestrial coordinates of the CIP in the transformation from the celestial to the terrestrial systems.
Massive Star Formation: New Results
Authors: Churchwell Ed 
Published: March 2016

In the past year several new observations with important implications for massive star formation (MSF) have been obtained. Among these were the detection of UC HII region precursor candidates at 350µm and the discovery of many hard X-ray point sources in the Orion and W3 MSF regions. These observations are summarized below.Hunter et al. (1998, 2000) imaged 25 MSF regions at 350µm to search for candidate precursors of UC HII regions (i.e. luminous submm/FIR emission, maser sources, and no HII emission). Of the 28 sources detected, 10 appear to be UC HII precursor candidates.
Formation of Massive Stars by Growing Accretion
Authors: Maeder André 
Published: March 2016

AbstractWe calculate pre-Main Sequence evolutionary tracks with accretion rates growing with the actual stellar masses. We show that accretion rates growing at least as M1.5 are necessary to fit the constraints on the lifetimes and HR diagram. Most interestingly, such accretion rates growing with the stellar mass well correspond to those derived from observations of mass outflows (Churchwell 2000; Henning et al. 2000). These rates also lie in the permitted region of the dynamical models.
Evolution of the Edgeworth-Kuiper Belt
Authors: Ipatov S.I. 
Published: March 2016

AbstractDue to gravitational interactions with large trans-neptunian objects (TNOs) several percent of TNOs can change their semimajor axes by more that 1 AU during last 4 Gyr. Now about 30000 1-km former TNOs can be Jupiter crossers and about 20% of Earth-crossing objects can be former TNOs which now move in Jupiter-crossing orbits.
Resonant Gaps in the Scattered Cometary Population of the Trans-Neptunian Region
Authors: Taidakova Tanya , Ozernoy Leonid M. , Gorkavyi Nick N. 
Published: March 2016

AbstractOur numerical simulations of the Edgeworth-Kuiper Belt objects gravitationally scattered by the four giant planets accounting for mean motion resonances reveal numerous resonant gaps in the distribution of the scattered population.
The Special Case of ω Centauri
Authors: Norris John E. 
Published: March 2016

Abstractω Cen is unique among the Galactic globular clusters. It exhibits not only classical mixing signatures, but also those of primordial chemical enrichment by both massive and intermediate-mass stars: the abundances of all elements vary, not just those of the C, N, O, Na, Mg, and Al. The challenge is to disentangle the roles of mixing and primordial phenomena. We discuss here what sets ω Cen apart from the other clusters.
East Asian Astronomical Records
Authors: Stephenson F. Richard 
Published: March 2016

AbstractChinese, Japanese and Korean celestial observations have made major contributions to Applied Historical Astronomy, especially in the study of supernovae, comets, Earth’s rotation (using eclipses) and solar variability (via sunspots and aurorae). Few original texts now survive; almost all extant records exist only in printed versions, often with the loss of much detail. The earliest Chinese astronomical observations extend back to before 1000 BC. However, fairly systematic records are only available since 200 BC - and even these have suffered losses through wars, etc. By around AD 800, many independent observations are available from Japan and Korea and these provide a valuable supplement to the Chinese data. Throughout East Asia dates were expressed in terms of a luni-solar calendar and conversion to the Julian or Gregorian calendar can be readily effected.
Southern Hemisphere Observations
Authors: Orchiston Wayne 
Published: March 2016

AbstractBecause of insurmountable problems associated with absolute dating, the non-literate cultures of the Southern Hemisphere can contribute little to Applied Historical Astronomy, although Maori traditions document a possible supernova dating to the period 1000-1770AD. In contrast, the abundant nineteenth century solar, planetary, cometary and stellar observational data provided by Southern Hemisphere professional and amateur observatories can serve as an invaluable mine of information for present-day astronomers seeking to incorporate historical data in their investigations.
Historical Supernovae and their Remnants
Authors: Green D.A. 
Published: March 2016

AbstractHistorical records are available for nine supernova explosions seen in our Galaxy over the last two millennia. The observations of these ‘historical’ supernovae are very useful for the modern astrophysical interpretation of the remnants of these supernovae. The ages of the remnants of these historical supernovae are definitively known, which greatly aids understanding of the nature of the remnants. Also, the fact that the parent supernova was seen implies that it was relatively nearby in the Galaxy, giving further constraints on the distance, and hence other properties of their remnants. Here I briefly review the historical supernovae in our Galaxy, in the context of our understanding of their remnants from modern observations.
The Historical Activity of Comet 55P/Tempel-Tuttle and Large Leonid Meteoroids
Authors: Beech Martin 
Published: March 2016

AbstractEven though comet 55P/Tempel-Tuttle has an orbital period of about 33 years it has only been recovered five times in the past 630 years. The earliest clearly documented return is that of 1366, with the others being in 1699, 1865, 1965 and 1998. The comet may have been briefly sighted in 1035 (indicative of a possible outburst) and in 1234 and it was conspicuous by its non-recovery in 901 (possibly indicating very low surface activity during that return). We review the absolute magnitude data for comet 55P /Tempel-Tuttle and find tentative evidence to suggest it underwent an outburst in 1699. If large meteoroids were ejected from the comet during the 1699 outburst numerical integration studies find that they would have been Earth-orbit crossing in 1832 and 1965 - years in which the Leonid shower was rich in bright fireballs. The Earth will also sample 1699 ejected material in November 2001.
Solar Variability Manifestation on Earth-Climate Parameters Registered at a Tropical Location
Authors: Pomares Oscar Alvarez , Doval Jorge Pérez , Pérez Pedro A. Cárdenas , González Raimundo Vega 
Published: March 2016

AbstractThe authors present evidence for a connection between solar activity and mean winter temperatures at Havana, Cuba, in observations covering the past 130 years. The colder-than-average winters tend to follow 2±1 years after years of maximum solar activity.
IPS Observations at Beijing Astronomical Observatory
Authors: Zhang X.Z. , Wu J.H. 
Published: March 2016

The radio wave from distant radio sources will be scattered by the irregular structures of the solar wind plasma when propagating through the interplanetary space, resulting into a randomly fluctuating pattern of the radio wave in observation. This pattern is called interplanetary scintillation (IPS). Observation on IPS can give information of the solar wind speed and irregular structures in solar wind plasma. The IPS observations began at Miyun Station, Beijing Astronomical Observatory from the late half of 1999. The properties of the telescope and description of the data analysis can be found in the papers of Wang (1987) and Wu, Zhang and Zheng (2000) respectively.Table 1 summarizes some observational results using IPS source 3C48 in April and May 2000. The Fresnel knees and the first minima in the IPS spectra were used to estimate solar wind speeds. Comparisons of our results with the unpublished data of Hiraiso Solar Terrestrial Research Center obtained from their web site, have been done and good agreement between the two systems was found. Since the collecting area of Miyun telescope is limited, the system noise is relatively high and dominates the high-frequency parts of the spectra. The Miyun IPS observation and data reduction procedures are still under developing and will soon be completed.
The Oxygen Problem
Authors: Bessell Michael S. 
Published: March 2016

AbstractPermitted OI, forbidden [OI], electronic AΣ − XП UV OH and vib-rot IR OH lines often infer different oxygen abundances for cool stars. Which species should one use to determine the oxygen abundance in cool stars and how does one reconcile the different results for different species? Although there are uncertainties and systematic differences in the molecular gf values used by different authors, the main reason for the different results lies in the 1-D model atmosphere analyses that are used.
NLTE Effects on Oxygen Lines
Authors: Kiselman Dan 
Published: March 2016

AbstractThe NLTE effects affecting oxygen-abundance determinations of solar-type stars are discussed. LTE is safe for the forbidden lines. The permitted triplet at 777 nm is expected to show NLTE effects so that assuming LTE overestimates the abundance, but the magnitude of the effects is dependent on the poorly known cross sections of collisional excitation by collisions with neutral hydrogen atoms. Little is known about the NLTE effects on molecular line formation.
Oxygen Line Formation in 3D Hydrodynamical Model Atmospheres
Authors: Asplund Martin 
Published: March 2016

AbstractThe formation of [Oɪ], Oɪ and OH lines in metal-poor stars has been studied by means of 3D hydrodynamical model atmospheres. For Oɪ detailed 3D non-LTE calculations have been performed. While the influence of 3D model atmospheres is minor for [Oɪ] and Oɪ lines, the very low temperatures encountered at low metallicities have a drastic impact on OH. As a result, the derived O abundances are found to be systematically overestimated in 1D analyses, casting doubts on the recent claims for a monotonic increase in [O/Fe] towards lower metallicities.
The Evolution of the Oxygen Abundance in the Galaxy
Authors: Matteucci Francesca , Chiappini Cristina 
Published: March 2016

AbstractWe discuss the evolution of the [O/Fe] as a function of [Fe/H] in the Galaxy. In particular, we discuss the influence of different stellar yields as well as different SN (II, I) rates on the [O/Fe] ratio. Possible explanations for the steep rise of the [O/Fe] ratio at low metallicities, as indicated by recent observations, are critically discussed.
Submillimeter Surveys at High Redshift
Authors: Barger Amy J. 
Published: March 2016

AbstractDeep submillimeter (submm) surveys offer an unobscured view of dust-enshrouded star formation or AGN activity at high red-shifts. SCUBA observations above 2 mJy have resolved 20 – 30% of the far-infrared (FIR) background into discrete sources and have revealed the existence of a distant population of galaxies with properties similar to those of local ultraluminous infrared galaxies. A large fraction of the submm sources have extremely faint optical/near-infrared (NIR) counterparts and hence are inaccessible to optical spectroscopy. Millimetric redshift estimation places the submm population at z = 1 to 3. While the cumulative surface density of the submm sources is low, they are so luminous that if powered mainly by star formation, they dominate the high redshift star formation history. Recent combined SCUBA submm and Chandra hard X-ray studies suggest that the majority of the submm sources are star formers with only a small admixture of obscured AGN.
Gas and Dust in Ultraluminous Infrared Galaxies: Implications for Sources at High Redshift
Authors: Downes D. 
Published: March 2016

AbstractHigh-z mm and submm dust sources are thought to be similar to ultraluminous infrared galaxies, where merger interactions have driven most of the gas and dust into circumnuclear molecular disks or rings with typical radii of 500 pc. Within these disks, CO and radio data indicate a new class of extreme starbursts, with characteristic sizes of 100 pc, gas masses of 109 M⊙ and IR luminosities of ∼ 3 × 1011L⊙ from OB stars. Some of these regions, however, harbor powerful AGNs, even though the optical IR diagnostics may classify them as starbursts. Trentham (2000) argues that averaged over time, most of the high-z dust sources must be powered by AGNs.
ISOCAM Deep Surveys and the Cosmic Infrared Background
Authors: Elbaz David 
Published: March 2016

AbstractThe steep slope of the ISOCAM 15 μm number counts indicates that infrared galaxies have strongly evolved since z ∼ 1 − 1.5. A nearly complete spectroscopic sample of ISOCAM galaxies in the Hubble Deep Field North (HDFN) shows that their redshift distribution is peaked around z ∼ 0.8. We show that the 7 μm luminosity of local galaxies is correlated with their 8-1000 μm luminosity, and therefore star formation rate (SFR). We use this correlation in the rest-frame of the ISOCAM galaxies to deduce their IR luminosities (∼ 4 × 1011L⊙), SFR (∼ 80 M⊙yr−1) and contribution to the peak of the cosmic IR background (CIRB) at 140 μm. We find that they most probably produce the bulk of the CIRB.
Diffuse Cluster-Wide Radio Halos
Authors: Liang Haida 
Published: March 2016

AbstractWe will discuss the properties and origins of halos and relics including estimates of the cluster magnetic fields, and present results for a few recently discovered halos and relics. The electrons in the suprathermal high energy tail of the thermal gas distribution are likely to provide the seed particles for acceleration through mergers and turbulences to relativistic energies. These relativistic particles are then responsible for the synchrotron emission of the halos.
Galileo NIMS Observations of Io
Authors: Davies Ashley Gerard , Douté Sylvain 
Published: March 2016

AbstractThe Near Infrared Mapping Spectometer (NIMS) on the Galileo spacecraft has been observing the volcanic Jovian satellite Io at regular intervals since June 1996. These infrared observations have allowed detailed mapping of the distribution and grain size of sulfur dioxide on Io’s surface, identification of volcanic centers, mapping of the distribution of hot spots, and investigations into the style and evolution of individual volcanic eruptions.
Hubble Space Telescope Observations of Galilean Satellites
Authors: McGrath Melissa A. 
Published: March 2016

AbstractOne of the premier areas of scientific return from Hubble Space Telescope (HST) observations of Solar System objects has been studies of the Galilean satellites of Jupiter. Because these objects are unresolvable in most ground-based observations, HST’s spatially resolved imaging and spectroscopy of their surfaces, atmospheres, and electrodynamic interactions with the Jovian magnetosphere have provided unique results. This talk will review highlights of the science results from HST observations of the Galilean satellites, including discovery of auroral emissions at the poles of Ganymede, the recent discovery of molecular sulfur in the Pele plume on Io, and the presence of SO2 in the surface of Callisto.