bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
The Opacity Driven Pulsators
Authors: Dziembowski Wojciech A.
Published: March 2016

The opacity mechanism is the only well understood excitation mechanism of observed stellar oscillations. The driving effect arises due the a specific form of the opacity perturbation which leads to a conversion of the radiative flux energy into kinetic energy of oscillations. In 1963 Baker and Kippenhan demonstrated that the opacity mechanism acting in the Hell ionization zone is the cause of the Cepheid pulsations. Subsequently it has been shown that the same mechanism works in a large variety of stars. There are three opacity bumps that play a role in pulsation excitation in various types of objects - one connected with the H ionization, one connected with He II ionization zone - and one, discovered quite recently by Iglesias, Rogers & Wilson (1988), caused by a large agglomeration of metal element (mostly Fe) lines.
Horizontal Branch Evolution and RR Lyrae Star Pulsation
Authors: Cox Arthur N.
Published: March 2016

For many years there has been a confrontation between stellar evolution and pulsation theories concerning the masses, luminosities, and compositions of the horizontal branch RR Lyrae variables. Masses obtained by Cox, Hodson & Clancy (CHC, 1983) were very low, but Kovacs (1985) and later Kovacs & Buchler (1988) suggested somewhat larger ones. Even later Simon & Cox (1991) verified CHC results, though still using the Los Alamos opacities. Petersen (1991, 1992) has also discussed this mass problem in some detail. The persistent discrepancy of 0.1 Mʘ or more between the evolution and pulsation masses was mostly ignored because neither theory could find any significant flaw in its analysis. Cox (1991), Kovacs, Buchler & Marom (1991), and Kovacs, Buchler, Marom, Iglesias & Rogers (1992) finally showed that larger double-mode pulsation masses, are consistent with evolution calculations to reproduce color-magnitude diagrams of globular clusters. Evolution tracks by many for years, especially the recent ones by Lee, Demarque & Zinn (1990), did require a much lower primordial helium abundance near the big bang value near Y = 0.23, and now this value, slightly enhanced by deep convection dredge-up in the earlier red giant stage, is also found to be appropriate for pulsation studies.
Impact L Observed at a Wavelength of 892 nm with the Solar Vacuum Telescope on Tenerife
Authors: Schleicher H. , Balthasar H. , Knölker M. , Schmidt W. , Jockers K.
Published: March 2016

During the impact of fragment L filtergrams of high spatial and temporal resolution were obtained in the methane band centered at 892 nm with the solar vacuum tower telescope (VTT) located at Izaña, Tenerife. The VTThas an aperture of 0.70 m and a focal length of 45 m. Images were taken every 20 s in the prime focus with a CCD camera operated in 512 х 512 pixel mode. One pixel corresponds to 0.175 arcsec. The spatial resolution varied between 0.5 and 1.5 arcsec due to seeing effects. The exposure time was 2.5 s. At 22:20:52 UT, four minutes after the impact time based on Galileo images, a first brightening above the dark southeast limb of Jupiter was recognized. A first maximum was reached after five minutes. The subsequent decline of brightness was interrupted at 22:31:52 by a sudden bright flare with a lifetime of 90 s. Within our resolution the two recorded emission features are cospatial. The flux of this flare was (3.4 ± 0.2) х 10-4 of Jupiter’s total flux at this wavelength. The feature became almost invisible 19 minutes after its first detection. At 22:43 UT, 26 minutes after the impact, a new brightness enhancement rotated into view which could be identified with the dark impact signature (debris cloud) observed in the visual wavelength range.
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

Interplanetary 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.
Observations of Gas-Phase Atoms and Molecules
Authors: Lacy John H.
Published: March 2016

Some recent observations of interstellar, circumstellar, and stellar atoms and molecules, with ground-based telescopes and ISO, are discussed. The advantages of observations with SIRTF and SOFIA, and needed laboratory work are mentioned more briefly.
Surface Reactions in Interstellar Space
Authors: Herbst Eric
Published: March 2016

It is impossible to explain the abundances of some gas-phase and most condensed-phase interstellar molecules without the use of grain chemistry. Nevertheless, grain-surface chemistry is relatively poorly understood for a variety of reasons. Our current knowledge of this chemistry and its use in interstellar models is discussed along with specific needs for future research.
The FERRUM Project: Oscillator Strengths of the Iron Group Elements: Fe II
Authors: Johansson Sveneric
Published: March 2016

We 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

The 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

Two 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

We 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.
Obscured Galactic Giant HII Regions; Discovery of Young Clusters
Authors: Conti Peter S. , Blum Robert D.
Published: March 2016

Giant HII (GHII) regions in our Galaxy are typically initially found by radio observations of their optically thin free-free continuum emission. Most of them are partially or totally obscured in the visible by the absorbing effect of intervening and/or local interstellar dust. We (Blum et al. 1999, 2000) have selected a list of the brightest GHII regions in our Galaxy (from Smith et al. 1978) and have begun a program of JHK imaging and K band spectroscopy to identify and classify the exciting stars. We have obtained near IR imaging of eight GHII regions (and data is available for four others). All of these, aside from W49, show the presence of a stellar cluster in the K band at the radio source position. The K,H — K diagrams are used to select the brightest stars. The J — Kvs. H — K diagrams distinguish those stars along the normal reddening line from those with K band excesses. The former group ought to have normal OB star spectra; the latter will have featureless continua in the K band due to emission from localized warm dust arising in a natal disc (Hanson et al. 1997). A disc geometry can also produce CO emission (or absorption) band features.
Evolution of the Edgeworth-Kuiper Belt
Authors: Ipatov S.I.
Published: March 2016

Due 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

Our 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

ω 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.
Mixing and Transport in Stars
Authors: Canuto Vittorio M.
Published: March 2016

Transport and mixing in stars is as important as it is difficult to quantify (Zahn 1992; Schatzman 1996; Maeder 1997; Pinsonneault 1997). A first difficulty is that both transport and mixing are dynamical processes which, given the low viscosities of stellar interiors, usually means that the flow is turbulent giving rise to technical difficulties for turbulence is still an incomplete chapter though recent studies have brought about considerable progress. A second difficulty is that turbulence is not self-sustaining and unless there is a source, dynamical mixing and transport will decay in time and eventually die out. Thus, the question: what is the source of turbulence, let alone how to describe it? In the convective zone, the source is the unstable stratification but the mixing there is so strong that one does not need a sophisticated theory to describe it. Strong turbulence is easier to describe than weak turbulence and yet the latter is when the problems become interesting and our descriptive power is less reliable. For example, below the solar CZ we don’t even know for sure the source of stirring, let alone how to describe it and yet, it is the region where we would like to be confident about models. The transport of Li is the best example of a mixing and transport that cannot be too strong or too weak (Schlattl and Weiss 1999). A third difficulty is the unstated assumption that “transport” (advection) and “mixing” (diffusion) have different origin.
East Asian Astronomical Records
Authors: Stephenson F. Richard
Published: March 2016

Chinese, 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

Because 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

Historical 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

Even 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.
Akademische Sternkarten, Berlin 1830—59
Authors: Jones Derek
Published: March 2016

Bessel proposed to the Berlin Academy that 24 astronomers should collaborate in mapping the sky within 15° of the equator. The projected completion date was 1829. The actual completion date was 1859.
Plasma Theory of Solar Radar Echoes after Thirty Years
Authors: Mel’nik Valentin
Published: March 2016

In 1967 Gordon made the revolutionary assumption that reflection of radar signal from the Sun can be explained by its scattering on microturbulence (Gordon 1973). In his first model it was ion-sound turbulence. Later he considered radar scattering on Langmuir turbulence. The principal opportunity to explain frequency displacements of radar echoes observed in James’ experiments (James 1966, 1970) was shown. However, it turned out (Gerasimova 1979) that the mechanism needed an impermissible high level of isotropic turbulence for the reflection with cross-sections σ = 10πR2ʘ.
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

The 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

Permitted 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

The 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

The 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

We 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

Deep 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

High-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

The 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.
X-Ray Observations of Cluster Mergers Before 2000 AD
Authors: Buote David A.
Published: March 2016

I review the evidence for cluster mergers from X-ray observations with Einstein and ROSAT. Different techniques to study cluster mergers via X-ray imaging and spectral data, and the current implications of measurements of cluster substructure for Ω0, are briefly discussed.
Diffuse Cluster-Wide Radio Halos
Authors: Liang Haida
Published: March 2016

We 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.
The Magnetized Intracluster Plasma
Authors: Eilek Jean
Published: March 2016

We now know that the plasma in clusters of galaxies is magnetized, at strong levels in some regions. It follows that the dynamics of the cluster plasma is more complex than has been thought up to now.
Galileo NIMS Observations of Io
Authors: Davies Ashley Gerard , Douté Sylvain
Published: March 2016

The 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

One 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.
Martian Surface Composition as Determined by the MGS Thermal Emission Spectrometer
Authors: Ruff Steve R. , Christensen Philip R. , Bandfield Joshua L. , Hamilton Victoria E. , Kieffer Hugh H. , Morris Richard V. , Lane Melissa D. , Malin Michael C.
Published: March 2016

The surface composition of Mars has been investigated using the Thermal Emission Spectrometer (TES) instrument during the mapping phase of the Mars Global Surveyor mission. The TES has mapped ~85% of the Martian surface at a resolution of 3-9 km. Separation of the atmospheric dust, water-ice cloud, CO2, water vapor, and surface components has been accomplished using radiative transfer and deconvolution. Two distinct surface compositional units have been mapped; (1) a basalt with plagioclase feldspar, Ca-rich pyroxene, minor sheet silicates; and (2) a basaltic andesite with silica glass, plagioclase, and minor pyroxene. Three large-scale (100’s km) accumulations of hematite have been found in Sinus Meridiani, Aram Chaos and Ophir/Candor Chasms. These regions are interpreted to be formed by aqueous precipitation under either ambient or hydrothermal conditions. No surfaces with detectable abundances of carbonate have been found. The albedo of the surface has been mapped with an absolute accuracy of ~1-2% and significant changes in surface albedo have occurred from the orbital measurements obtained by the Viking IRTM instrument.
Missions to Phobos and Other Minor Bodies
Authors: Avduevsky Vsevolod S. , Akim Efraim L. , Eneev Timur M. , Marov Mikhail Ya. , Kulikov Stanislav D. , Kremnev Roald S. , Popov Garry A.
Published: March 2016

A space mission to Mars’ moon Phobos with a space vehicle of new generation currently developed by the Russian Aerospace Agency is discussed. The vehicle design incorporates innovative SEP technology focused on small propulsion electric engines which significantly improve the mission energetic capability. The project is optimized around a sample return (PSR) from Phobos and also offers an opportunity for rendezvous/sample return missions from several asteroids, comets, and NEO. Scenario, rationale, and basic profile of PSR mission are presented.
Modelling of the Coherent Backscattering Opposition Effect: Comparison to Planetary Phase Curves
Authors: Kaasalainen Sanna , Muinonen Karri , Piironen Jukka
Published: March 2016

We study the opposition effect of icy planetary satellites by means of a Monte Carlo simulation of the coherent backscattering opposition effect for spherical objects covered with locally plane parallel media.
A Classical Cycle of Activity in the North Tropical Region of Jupiter, 1996-1999
Authors: Rogers John , Foulkes Michael , Mettig Hans-Joerg
Published: March 2016

Jupiter’s North Equatorial Belt (NEB) occasionally undergoes cycles of activity that consist of rapid broadening of the dark belt to the north, often accompanied by cyclonic bright “rift” activity, followed by development of large circulations in the expanded northern part (cyclonic dark “barges” and anticyclonic bright “portholes”), and a reddish colour across the belt (Rogers 1995). In 1996 there was a classic NEB broadening event with typical evolution over the following years. The broadening to the north began in 1996 April and spread around the belt by the summer. By 1997 April, there was an array of “barges” and “portholes” (white ovals) all around the broadened NEB, and increased redness of the belt. During 1997 the northern extension gradually reverted towards the normal bright albedo for this latitude, but the barges and ovals persisted. Indeed they still persist in 1999/00. Features in 1998/99/00 have included a rapidly-prograding white oval which destroyed barges ahead of it and had retrograding dark spots created following it; these retrograding spots have circulated as was observed in Voyager maps.
OB Associations, Open Clusters, and the Luminosity Calibration of the Nearer Stars
Authors: Brown Anthony
Published: March 2016

In the context of the luminosity calibration of the nearer stars I discuss the Hipparcos results on distances to nearby OB associations and open clusters. The shortcomings and assumptions in the analyses used to derive these results are pointed out and for the open clusters a comparison is made with results obtained from main sequence fitting. I conclude that given the considerable uncertainties in the latter technique there is no convincing evidence that the Hipparcos based distances to open clusters beyond the Hyades should not be trusted.
Luminosity Calibrations with Hipparcos: Theoretical Point of View
Authors: Lebreton Yveline
Published: March 2016

Hipparcos provided us with valuable observational material that can be used to anchor more firmly the Galactic and extragalactic distance scales. A calibration which is applicable to all stars must allow for differences in chemical composition and other properties, which may require the use of theoretical models. I discuss some difficulties encountered in the calibration procedure that are related (1) to the determinations of stellar temperatures, luminosities and chemical compositions, (2) to remaining weaknesses of theoretical stellar models, and (3) to the transformations of the model outputs from the (Mbol, Teff) plane into any colour-magnitude or colour-colour diagram.
HIPPARCOS and the Calibration of the MK System
Authors: Garrison R.F.
Published: March 2016

The HIPPARCOS satellite has provided astronomy with a wonderful legacy. We now have high-quality parallaxes for some of the yellow and red giants as well as for some of the A and F main sequence standards. It is now possible to compare field giants with those in globular clusters and to resolve some of the discrepancies. Hipparcos luminosities are being compared with various existing MK calibrations and the most glaring (i.e. interesting) inconsistencies will be discussed.
Red Clump Stars – Further Improved Distance Indicator
Authors: Garnavich P.M. , Stanek K.
Published: March 2016

The ideal distance indicator would be a standard candle abundant enough to provide many examples within reach of parallax measurements and sufficiently bright to be seen out to Local Group galaxies. The red clump stars closely match this description. These are the metal rich equivalent of the better known horizontal branch stars, and their brightness dispersion is only 0.2 mag (one sigma) in the Solar neighborhood. Using Hipparcos to calibrate a large, local sample, the red clump method has been used to measure accurate distances to the Galactic center (Paczyński & Stanek 1998), M31 (Stanek & Garnavich 1998), LMC (Udalski et al. 1998; Stanek et al. 1998; Udalski 1999) and some clusters in our Galaxy (e.g. 47Tuc: Kaluzny et al. 1998). As with all the distance indicators, the main worry lies in the possible systematics of the method, in particular, the brightness dependence on the stellar metallicity and age. These dependences have come under close scrutiny and, indeed, the population effects on the red clump brightness appear small and calibratable. Perhaps the most controversial result from the red clump method is the estimation of a “short” distance to the Large Magellanic Cloud (Udalski et al. 1998; Stanek, Zaritsky & Harris 1998; Udalski 2000). This distance to the LMC is shorter by 12% than the “standard” value, and has very important implications for the Cepheid distance scale and the determination of the Hubble constant.
Magnetic Fields in Young Galaxies
Authors: Nordlund Åke , Rögnvaldsson Örnólfur
Published: March 2016

We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using three-dimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching μG levels for reasonable values of the initial ratio of magnetic to thermal energy density.
Recent Results on Magnetic Fields in the Milky Way
Authors: Wielebinski R. , Reich W. , Fürst E.
Published: March 2016

Of all the methods available to observe magnetic fields in the Milky Way, the mapping of linear polarization at cm wavelengths has proven to be most successful. The instruments that have contributed most of the new data are the 100 m Effelsberg telescope and the Parkes 64 m dish. Their Galactic plane surveys gave us a new conception of the linear polarization distribution. A new Effelsberg 1.4 GHz ‘medium latitude polarization survey’ now being made gives us data about large sections of the Galaxy. Polarization maps of selected regions of the Galaxy are now being made at several frequencies up to 32 GHz. Data from Westerbork at ∼ 325 MHz, as well as data from the Canadian Galactic Plane Survey (CGPS) at 1.4 GHz give new exciting information.
Magnetic Fields in the Early Universe
Authors: Rees Martin
Published: March 2016

It is argued that the seed field from the galactic dynamo comes from the first supernovae or stellar winds, or perhaps from early AGNs.
Dark Matter: Astronomical Aspects
Authors: Trimble Virginia
Published: March 2016

The chief evidence for appreciable dark matter in the universe comes from the monotonic increase in mass to light ratios measured for various astronomical systems as one looks on larger and larger length scales. Though the evidence comes from photons, most of the dark matter is non-photonic, and, for that matter, non-baryonic. There remain several questions about the nature and behavior of dark matter to which conventional astronomical observations are (probably) relevant. The most germain to this JD is whether astronomers have seen decay or annihilation products from dark matter particles, to which the current answer seems to be no. We look at a few of the others.
Recent Advances in Ground-Based Observation of Mercury
Authors: Warell J.
Published: March 2016

The last decade has seen an efficient use of ground-based telescopes for remote-sensing studies of Mercury’s surface at optical, infrared and microwave wavelengths. This has resulted in a substantially improved knowledge of its regolith composition, material and light scattering properties and structures on the poorly known hemisphere. This paper summarizes recent observations and results on the regolith properties of Mercury.
The BepiColombo Mission
Authors: Schulz Rita , Falkner Peter , Peacock Anthony , Erd Christian , Rando Nicola , Kraft Stefan
Published: March 2016

BepiColombo is an interdisciplinary mission to the planet Mercury which will provide the detailed information necessary to understand Mercury and its magnetospheric environment. The mission is envisaged to consist of three spacecrafts, the Mercury Planetary Orbiter (MPO), the Mercury Magnetospheric Orbiter (MMO) and the Mercury Surface Element (MSE). The mission went through a re-assessment with the aim of optimizing resources and and advancing the scientific return. Various mission scenarios were investigated and new pay load concepts were adopted. The newly defined mission will be presented focusing on the launch scenario and the MPO reference payload.
Heating the Solar Corona
Authors: Woods L. C.
Published: March 2016

A typical temperature for the quiet solar corona is ~ 1.5 x 106K, whereas the photosphere – the likely source of the thermal energy – has a temperature less than 6 × 103 K. Although many theories have been advanced to explain why the corona is so much hotter than the photosphere, this old problem remains unsolved. However, there is a mechanism based on second-order transport that may provide the answer, or at least part of the answer. This process, described by the author in Thermodynamic inequalities in gases and magnetoplasmas, John Wiley & Sons Ltd, 1996, causes heat to be transported across strong magnetic fields up temperature gradients.
RATAN-600 Observations of Unusual Inversion of Polarization in Sunspot Associated Microwave Sources
Authors: Gizani N. A. B. , Alissandrakis C. , Bogod V. , Garaimov V. , Zheleznyakov V. , Zlotnik E.
Published: March 2016

We have discovered unusual inversion of circular polarization in both components of an active region. We have observed the region for six consecutive days in May 96 using the RATAN-600 radio telescope with high polarization accuracy up to 0.5 %. The observations were taken in the range of 1.7 to 30 cm. At short wavelengths the circular polarization scans revealed a bipolar structure, expected since the magnetic field is bipolar. However, for all six days and while the region was moving from the center of the disk to the west limb, the circular polarization dropped practically to zero at 14.5 cm and at longer wavelengths the sense of the polarization was reversed.
The Current Helicity Parameter Hc is More Sensitive than αbest to Faraday Rotation
Authors: Bao Shudong
Published: March 2016

Observations have indicated that the net helicity sign of active regions is predominantly negative in the northern hemisphere and positive in the southern (see Table 1). From Table 1, we find that the hemispheric sign rule of helicity parameter αbest does not change with another solar cycle; but the helicity parameter Hc seems to show a weak opposite hemispheric preference for Huairou data in the solar cycle 23 and no preference for Mees data. How to explain such a phenomenon? We think one reason may be from the action of Faraday rotation. Faraday rotation will cause a counterclockwise rotation of the azimuth for a positive polarity field and vice versa. During the cycle 22, the polarity of leading sunspots is dominantly negative in the northern hemisphere and positive in the southern. The effect of Faraday rotation, which is determined mostly by a leading polarity sunspot, has a positive contribution to the percentage of current helicity signs in active regions and leads to the increase of the strength of the hemispheric sign rule. In the cycle 23, the polarity of most leading sunspots is positive in the northern hemisphere and Faraday rotation will decrease the percentage of current helicity signs. Consequently, the strength of the hemispheric rule should be weakened. On the other hand, Hc is more susceptible to Faraday rotation than αbest because it is mainly related to the areas where the line-of-sight field is strong. Therefore, if the effect of Faraday rotation is not completely removed in our observations, the hemispheric sign rule showed is weak in the cycle 23 than in the cycle 22 (for αbest), even opposite (for Hc).
Summaries of Papers Presented at Joint Discussion Session 4: Astrophysical Impact of Abundances in Globular Cluster Stars
Authors: Da Costa G. S. , D’Antona F. , Gratton R. G.
Published: March 2016

In this contribution we give summaries of the oral and poster papers presented in Joint Discussion Session 4, Astrophysical Impact of Abundances in Globular Cluster Stars, at the XXVth IAU General Assembly. The full text of the papers can be found in Volume 75, issue 2, of the MEMORIE della Società Astronomica Italiana (Journal of the Italian Astronomical Society; see the web address: ).
From Young to Old: Spectral Models for Star Cluster Systems
Authors: Alvensleben Uta Fritze – v. , Anders Peter , de Grijs Richard
Published: March 2016

Evolutionary synthesis models for star clusters of various metallicities, including gaseous emission during the lifetime of the ionizing stars, are used to model star cluster systems comprising two populations: an old metal-poor globular cluster (GC) population similar to that of the Milky Way halo, and a second GC population of arbitrary metallicity. We investigate the time evolution of color distributions and luminosity functions for the two GC populations and compare with observations of E/SO galaxies. We show that multi-passband data for GC populations give clues to the relative ages and metallicities of the two subpopulations, and help constrain formation scenarios for their parent galaxies.
Formation of Globular Clusters in Galaxy Mergers
Authors: Bekki Kenji , Couch Warrick J. , Forbes Duncan A. , Beasley M. A.
Published: March 2016

Our numerical simulations first demonstrate that the pressure of ISM in a major merger becomes so high (> 105 kB K cm-3) that GMCs in the merger can collapse to form globular clusters (GCs) within a few Myr. The star formation efficiency within a GMC in galaxy mergers can rise up from a few percent to ~ 80 percent, depending on the shapes and the temperature of the GMC. This implosive GC formation due to external high pressure of warm/hot ISM can be more efficient in the tidal tails or the central regions of mergers. The developed clusters have King-like profiles with an effective radius of a few pc. The structural, kinematical, and chemical properties of these GC systems can depend on the orbital and chemical properties of major mergers.