bluuebunny/crossref_metadata_2025 huggingface dataset:
The Problem of Determining Oxygen Abundances in Old, Metal-Poor Stars
Authors: Kraft Robert P.
Published: March 2016

Determination of accurate oxygen abundances in old metal-poor stars is of importance for a variety of astronomical problems ranging from stellar evolution to cosmology. A brief review is given here of the four basic procedures from which values of [O/Fe] can be estimated.
Oxygen in Unevolved Starss
Authors: Boesgaard Ann Merchant
Published: March 2016

We have made observations of 24 unevolved stars of the OH lines in the ultraviolet spectral region at high spectral resolution and high signal-to-noise, typically 60 − 110 with Keck + HIRES. The O abundances have been computed by spectrum synthesis. For these cool, unevolved stars there is a linear relation between [O/H] and [Fe/H] over three orders of magnitude with very little scatter and a slope of +0.66 ±0.02. The relation between [O/Fe] and [Fe/H] is robustly linear with [O/Fe] = −0.35 (±0.03) [Fe/H]. There is no sign of a break at metallicities between −1.0 and −2.0.
Dust Absorption and Emission in Galaxies at High and Low Redshifts
Authors: Fall S. Michael
Published: March 2016

This article reviews three related topics: the extragalactic background light and its sources, evolution models for the dust absorption and emission in galaxies, and empirical constraints on these transfer processes in nearby starburst galaxies. It is intended that the material presented here will serve as an introduction to this Joint Discussion.
Molecular QSO Absorption Line Systems
Authors: Carilli C.L. , Menten K.M.
Published: March 2016

We review observations of molecular absorption line systems at high redshift toward red quasars and gravitational lenses.
Galileo: Close-up Views of Jupiter’s Dynamic Atmosphere
Authors: Vasavada Ashwin R.
Published: March 2016

The Galileo spacecraft’s Solid State Imager (SSI) has been returning mosaics of Jupiter since 1996. The combination of high spatial resolution, broad spectral range, and short mosaic time steps has revealed a dynamic, vertically extended cloud structure not detectable by Voyager. These data have stimulated new analyses of major features such as zonal jets, the Great Red Spot, White Ovals, and the Galileo Probe entry site. Near-infrared images have provided fundamental constraints on the vertical structure of clouds and hazes, including the first imaging of a water cloud. Results from night side imaging include an extensive search for lightning, the first matching of lightning events to day side storm clouds, and the first spectral and spatial measurements of visible-wavelength auroral phenomena (not discussed here, see Vasavada et al. 2000). The identification of several tall, energetic storm systems at specific latitudes has led to new ideas about the role of moist convection in Jupiter’s atmospheric energetics.
Titan’s Atmosphere (Clouds and Composition): New Results
Authors: Griffith Caitlin A.
Published: March 2016

Titan’s atmosphere potentially sports a cycle similar to the hydrologic one on Earth with clouds, rain and seas, but with methane playing the terrestrial role of water. Over the past ten years many independent efforts indicated no strong evidence for cloudiness until some unique spectra were analyzed in 1998 (Griffith et al.). These surprising observations displayed enhanced fluxes of 14-200% on two nights at precisely the wavelengths (windows) that sense Titan’s lower altitude where clouds might reside. The morphology of these enhancements in all 4 windows observed indicate that clouds covered ~6-9% of Titan’s surface and existed at ~15 km altitude.

Here I discuss new observations recorded in 1999 aimed to further characterize Titan's clouds. While we find no evidence for a massive cloud system similar to the one observed previously, 1%-4% fluctuations in flux occur daily. These modulations, similar in wavelength and morphology to the more pronounced ones observed earlier, suggest the presence of clouds covering ≤1% of Titan's disk. The variations are too small to have been detected by most prior measurements. Repeated observations, spaced 30 minutes apart, indicate a temporal variability observable in the time scale of a couple of hours. The cloud heights hint that convection might govern their evolution. Their short lives point to the presence of rain.
High Resolution Spectroscopy As a Tool for Luminosity Calibration
Authors: Peterson Ruth C.
Published: March 2016

Recent results are reviewed for two methods of luminosity calibration based on high-resolution spectroscopy. The first relies on Teff/log g determinations from model-atmosphere analyses based on high-resolution spectra. This method is physically well founded but operationally demanding, and requires advance knowledge of stellar mass. The second, W-B, stems from the empirical relationship between luminosity and the width of chromospheric emission lines first established by Wilson and Bappu. Its physical basis is only partially understood, however, and the calibration depends on stellar metallicity and on the choice of lines.

Both Teff/log g and W-B easily distinguish cool dwarfs from cool giants. Generally reasonable agreement is found between distances derived from Hipparcos parallaxes and those inferred from the log g values derived for nearby dwarfs with relatively well-known Hipparcos parallaxes, σ(π)/π < 0.2. Constraining Hipparcos parallaxes star-by-star is not possible at present. Improvements are suggested for both approaches.
The Luminosity Calibration of the uvby — β Photometry
Authors: Jordi C. , Luri X. , Masana E. , Torra J. , Figueras F. , Domingo A. , Gómez A.E. , Mennessier M.O.
Published: March 2016

The ESA HIPPARCOS satellite has provided astrometry of unprecedented accuracy, allowing us to reassess, improve and refine the pre-Hipparcos luminosity calibrations. We review the “classical” absolute magnitude calibrations with the Strömgren-Crawford intermediate-band photometric system. A small zero point correction of about 2-4% seems necessary, as well as to refine the dependences on metallicity and projected rotational velocity. The need of a rigorous statistical treatment of the extremely precise Hipparcos data to derive definitive dependences of the luminosity on physical parameters is emphasized.
Theoretical Expectations for Clump Red Giants as Distance Indicators
Authors: Girardi Léo
Published: March 2016

Variations of ~ 0.4 mag are expected in the I-band absolute magnitude of red clump giants, , as a function of both stellar age and metallicity. This is the case regardless of some potential theoretical uncertainties. The quite large differences in mean ages and metallicities of clump stars among galaxies result in systematic changes (of up to ~ 0.4 mag) in their . These numbers also indicate a distance to the LMC that is not necessarily “short”.
Synthesis of Small and Large Scale Dynamos
Authors: Subramanian Kandaswamy
Published: March 2016

Using a closure model for the evolution of magnetic correlations, we uncover an interesting plausible saturated state of the small-scale fluctuation dynamo (SSD) and a novel anology between quantum mechanical tunnelling and the generation of large-scale fields. Large scale fields develop via the α-effect, but as magnetic helicity can only change on a resistive timescale, the time it takes to organize the field into large scales increases with magnetic Reynolds number. This is very similar to the results which obtain from simulations using the full MHD equations.
Neutrino Properties from Measurements using Astrophysical and Terrestrial Sources
Authors: McDonald A.B.
Published: March 2016

The current knowledge of neutrino properties has been derived from measurements performed with both astrophysical and terrestrial sources. Observations of neutrino flavor change have been made with neutrinos generated in the solar core, through cosmic ray interactions in the atmosphere and in nuclear reactors. A summary is presented of the current knowledge of neutrino properties and a description is provided for future measurements that could provide more complete information on neutrino properties.
The Surface-Bounded Exosphere of Mercury
Authors: Potter Andrew
Published: March 2016

Almost thirty years ago, the instruments on the Mariner 10 spacecraft detected traces of hydrogen, helium, and possibly oxygen in the atmosphere of Mercury. There the matter rested until the mid-80’s, when emission lines of sodium (Potter & Morgan 1985) and potassium (Potter & Morgan 1986) were found in the spectrum of Mercury, resulting from resonance scattering of sunlight by metal atoms in the atmosphere. Searches for other metals in the Mercury atmosphere were fruitless until recently, when an emission line attributed to calcium has been observed (Bida, Killen & Morgan 2000). The densities of all these species are so low that gas phase collisions are negligible, so that the Mercury atmosphere is an exosphere bounded at its base by the surface of the planet. The fact that the exosphere is bounded by the Mercury surface means that interactions with the surface must occur. Energy exchange, surface absorption and desorption, and ion neutralization can take place, and these must be accounted for in models of the exosphere. None of these atmospheric species can survive long on Mercury, being lost mainly by photoionization followed by trapping in the solar wind and partly by solar radiation acceleration. Consequently, the species that we observe must be in a steady state, being generated as fast as they are lost to space. The metals must originate from the surface of the regolith, with the supply of fresh surface material maintained by gardening of the surface by meteoroid impact. The metals are released from the surface into the exosphere by photon-stimulated desorption (Madey et al. 1998), particle sputtering (McGrath, Johnson & Lanzerotti 1986), and meteoroid impact vaporization (Morgan, Zook & Potter 1988). Thermal evaporation of species condensed on the cold side may be important for determining their distribution over the planet (Hunten & Sprague 2002). The interaction and relative importance of all these processes has been discussed by Killen & Morgan (1993). Much can be said about these processes, but this review is focused primarily on the current status of observations of sodium, potassium, and calcium.
Helicity Generation and Signature in Solar Atmosphere
Authors: Pevtsov A. A.
Published: March 2016

To fully understand the origin, evolution and topology of solar magnetic fields, one should comprehend their magnetic helicity. Observationally, non-zero helicity reveals itself in the patterns of electric currents inside active regions, superpenumbral sunspot whirls, the shape of coronal loops and the fine structure of chromospheric filaments. Some patterns may bear information about deep sub-photospheric processes (e.g., dynamo, turbulent convection). Others may originate at or near the photosphere. This presentation reviews the observations of magnetic and current helicity on the Sun, discusses the possible mechanisms of helicity generation, and compares them with the observations.
Magnetic Helicity in Sigmoids, Coronal Mass Ejections and Magnetic Clouds
Authors: Rust D. M.
Published: March 2016

Sigmoids, coronal mass ejections (CMEs) and magnetic clouds (MCs) all show signatures of twisted and writhing magnetic fields. CMEs are often associated with MCs, whose fields are regularly mapped with sensitive magnetometers. These measurements reveal that MC fields are helical, and each MC carries magnetic helicity away from the sun. It is more difficult to determine the magnetic helicity of the corresponding features on the sun. This presentation surveys recent work on helicity in solar features, focusing especially on the interpretation of sigmoids, which are S-shaped, bright features seen in images from the Yohkoh soft X-ray telescope. Several lines of evidence indicate that sigmoids are twisted and writhing flux ropes that erupt as components of CMEs. CMEs may be initiated by MHD-instable flux ropes. The fact that the ejected flux ropes carry off a large amount of positive helicity from the south and negative helicity from the north each solar cycle implies an equal, compensating flow of helicity through the sun’s equatorial plane.
Prominence Formation Processes
Authors: Welsch B.T. , DeVore C. R. , Antiochos S. K.
Published: March 2016

We summarize our attempts simulate the prominence formation model proposed by Martens & Zwaan (2001, ApJ, 558, 872) in which differential rotation drives reconnection between two initially unconnected bipolar active regions to form helical field lines along the polarity inversion line (PIL) between the flux systems.
New Force-Free Models of Magnetic Clouds
Authors: Vandas M. , Romashets E. P. , Watari S.
Published: March 2016

Magnetic clouds are thought to be large flux ropes propagating through the heliosphere. Their twisted magnetic fields are mostly modeled by a constant-alpha force-free field in a circular cylindrical flux rope (the Lundquist solution). However, the interplanetary flux ropes are three dimensional objects. In reality they possibly have a curved shape and an oblate cross section. Recently we have found two force-free models of flux ropes which takes into account the mentioned features. These are (i) a constant-alpha force-free configuration in an elliptic flux rope (Vandas & Romashets 2003, A&A, 398, 801), and (ii) a non-constant-alpha force-free field in a toroid with arbitrary aspect ratio (Romashets & Vandas 2003, AIP Conf Ser. 679, 180). Two magnetic cloud observations were analyzed. The magnetic cloud of October 18-19, 1995 has been fitted by Lepping et al. (1997, JGR, 102, 14049) with use of the Lundquist solution. The cloud has a very flat magnetic field magnitude profile. We fitted it by the elliptic solution (i). The magnetic cloud of November 17-18, 1975 has been fitted by Marubashi (1997) with use of a toroidally adjusted Lundquist solution. The cloud has a large magnetic field vector rotation and a large magnetic field magnitude increase over the background level. We fitted it by the toroidal solution (ii). The both fits match the rotation of the magnetic field vector in a comparable quality to the former fits, but the description of the magnetic field magnitude profiles is remarkable better. It is possible to incorporate temporal effects (expansion) of magnetic clouds into the new solutions through a time-dependent alpha parameter as in Shimazu & Vandas (2002, EP&S, 54, 783).
Magnetic Helicity Generated together with Evolution of the Large-Scale Magnetic Field
Authors: Ambrož Pavel
Published: March 2016

Text below is an extended abstract of the poster, presented on JD03 session during 25th GA IAU in Sydney.
Of Tilt and Twist
Authors: Holder Zachary A. , Canfield Richard C. , McMullen Rebecca A. , Howard Robert F. , Pevtsov Alexei A.
Published: March 2016

Using Mees Solar Observatory active-region vector magnetograms and Mt. Wilson Observatory full-disk longitudinal magnetograms, we measure both the twist and tilt of the magnetic fields of 368 active regions. This dataset clearly shows two well-known phenomena, Joy’s law and the hemispheric helicity rule, as well as a lesser-known twist-tilt relationship, which is the point of this work. Those regions that closely follow Joy’s law show no twist-tilt relationship, which is a predicted consequence of convective buffeting of initially untwisted and unwrithed flux tubes through the Σ effect. Those regions that strongly depart from Joy’s law show significantly larger than average twist and a very strong twist-tilt relationship. These properties suggest that the twist-tilt relationship in these regions is due to kinking of flux tubes that are highly twisted but not strongly writhed.
The Evolution of NGC 5128: Globular Clusters and Field Stars
Authors: Peng Eric W.
Published: March 2016

As the nearest giant elliptical galaxy, NGC 5128 (Centaurus A) is an excellent place to use globular clusters (GCs) and host galaxy field stars to study galaxy evolution. We have performed a detailed investigation of this galaxy, comparing field star kinematics with the metallicities, ages, and kinematics of GCs. We used our sample of 780 planetary nebulae (PNe) to trace the kinematics of the field star population. Our survey for GCs bring the total number of confirmed GCs to 215. Using spectra of the brightest GCs to determine ages, we find that the metal-rich GCs have a mean age of approximately 4-5 Gyr, and that their kinematics are similar to those of the PNe. The metal-poor GCs have old ages similar to the Galactic GCs, and show a weaker kinematic correlation with the field stars. It is possible that NGC 5128 was formed by the merger of two or more disk galaxies at the time that the metal-rich clusters were formed.
The Dynamical Mass of the Young Cluster W3 in NGC 7252: Heavy-Weight Globular Cluster or Ultra-Compact Dwarf Galaxy?
Authors: Maraston Claudia , Bastian N. , Saglia R. P. , Kissler-Patig Markus , Schweizer François , Goudfrooij Paul
Published: March 2016

We have measured the dynamical mass of the highly luminous star cluster W3 in the young merger remnant galaxy NGC 7252. The value is Mdyn = (8 ± 2) × 107M⊙, and represents the highest dynamically-confirmed mass for an extra-galactic star cluster so far. The dynamical mass is in excellent agreement with the luminous mass (Maraston et al. 2001). This results from the use of stellar population models that include correctly the brightest AGB stellar phase, dominant in young stellar populations. To classify W3, we employ the fundamental plane of stellar systems (Bender, Burstein & Faber 1992), for the first time in these kinds of studies. We find that W3 lies far from typical Milky Way globular clusters, but it is also far from the heavyweights ωCen in the Milky Way and G1 in M31, because it is too extended for its mass, and from dwarf elliptical galaxies because it is much more compact for its mass. Instead W3 lies close to the ultra-compact Fornax objects (Drinkwater et al. 2003) and to the compact elliptical M32, possibly shedding light on the still mysterious nature of these objects. A previously deserted region of the fundamental plane starts to be populated.
Dynamical Evolution of Globular Cluster Systems in Clusters of Galaxies: The Case of NGC 1404 in the Fornax Cluster
Authors: Bekki Kenji , Couch Warrick J. , Forbes Duncan A. , Beasley M. A.
Published: March 2016

We investigate, via numerical simulations, the tidal stripping and accretion of globular clusters (GCs). In particular, we focus on creating models that simulate the situation for the GC systems of NGC 1404 and NGC 1399 in the Fornax cluster, which have poor (specific frequency
SN ~ 2) and rich (SN ~ 10) GC systems respectively. We initially assign NGC 1404 in our simulation a typical SN (~ 5) for cluster ellipticals, and find that its GC system can only be reduced through stripping to the presently observed value, if its orbit is highly eccentric (with orbital eccentricity of > 0.5) and if the initial scale length of the GCs system is about twice as large as the effective radius of NGC 1404 itself. These stripped GCs can be said to have formed a ‘tidal stream’ of intra-cluster globular clusters (ICGCs) orbiting the center of Fornax cluster (many of which would be assigned to NGC 1399 in an imaging study). The physical properties of these GCs (e.g., number, radial distribution, and kinematics) depend on the orbit and initial distribution of GCs in NGC 1404. Our simulations also predict a trend for 5N to rise with increasing cluster-centric distance – a trend for which there is some observational support in the Fornax cluster. We demonstrate that since the kinematical properties of ICGCs formed by tidal stripping in the cluster tidal field depend strongly on the orbits of their previous host galaxies, observations of ICGC kinematics provides a new method for probing galaxy dynamics in a cluster.
The Spectra of Bright Near-IR Clusters in M82
Authors: Lançon A. , Mouhcine M. , Chané E. , Smith L.J. , Gallagher J.S. , Schreiber N. Förster , Vacca W. , de Grijs R. , O’Connell R.W.
Published: March 2016

Based on new spectra spanning wavelengths from 0.8 to 2.4μm, we study the properties of bright near-IR clusters in M82. We focus on age and extinction, which are critical parameters when one uses dynamical masses to constrain the stellar IMF. The modelling of red supergiant evolution by various authors leads to very significant differences in synthetic cluster spectra. Near-IR fluxes alone therefore do not rule out a normal IMF for cluster F, previously found to be deficient in low mass stars. Combined optical and near-IR studies are being undertaken.
Multicolor Photometry and Age Estimates of Globular Clusters in M31
Authors: Ma Jun
Published: March 2016

We present CCD multicolor photometry for 172 globular clusters (GCs), taken from the Bologna catalog (Battistini et al. 1987), in the nearby spiral galaxy M31. The observations were performed by using the National Astronomical Observatories 60/90 cm Schmidt Telescope in 13 intermediate-band filters, which covered a range of wavelength from 3800 to 10000 Å. This provides a multicolor map of M31 in pixels of 1.7 × 1.7 arcminutes. By aperture photometry, we obtain the spectral energy distributions (SEDs) for these GCs. Using the relationship between the Beijing-Arizona-Taiwan-Connecticut (BATC) intermediate-band system used for the observations and the UBVRI broad-band system, the magnitudes in the B and V bands are derived. The computed V and B–V are in agreement with the values given by Battistini et al. (1987) and Barmby et al. (2000). Finally, by comparing the photometry of each GC with theoretical stellar population synthesis models of Bruzual & Chariot (1996, hereafter BC96), we estimate ages of the sample GCs for different metallicities. The BC96 models provide the evolution in time of the spectrophotometric properties of simple stellar populations for a wide range of stellar metallicity. The results show that nearly all our sample GCs have ages more than 109 years, and most of them are around 1010 years old. At the same time, we find that GCs fitted by the metal-poor model are generally older than ones fitted by the metal-rich model.
Young Stellar Clusters in the ULIRG IRAS 17208–0014
Authors: Reddy Naveen A. , Jogee Shardha , Scoville Nick
Published: March 2016

High resolution studies reveal that luminous young stellar clusters and their associations are ubiquitous within 1 kpc of ULIRGs, and could be the precursors to globular clusters. We have undertaken a study of the ages, masses, extinction, and dust properties of the clusters found in the brightest ULIRG in the extended IRAS BGS Sample, IRAS 17208–0014, using it as a unique system in which to study the formation and evolution of clusters in gas-rich mergers. Using NICMOS JHK and WFPC2 I–band images, we have compared the near-IR colors of the clusters with those expected from a Bruzual & Chariot model. There are a few clusters whose colors can be explained by moderate values of extinction (1 – 3 mag), but others require some contribution from hot (400 – 1000 K) dust. We derive ages of a few tens of Myr and masses from 106 to 107 M⊙. These clusters may be supermassive compared to globular clusters, or could be unresolved associations of clusters.
Radio Sources as Probes of Distant Clusters
Authors: Baker Joanne , Barr Jordi , Bremer Malcolm
Published: March 2016

Powerful radio sources are efficient probes of dense regions throughout the universe, including clusters of galaxies. The status of cluster searches around radio sources is reviewed, including new evidence that cluster environments affect radio morphology.
Non-Thermal Activity and Particle Acceleration in Clusters of Galaxies
Authors: Petrosian Vahe’
Published: March 2016

Evidence for non-thermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons, and new windows (in EUV and Hard X-ray ranges) have provided more powerful tools for its investigation. The hard X-ray observations, notably from Coma, are summarized and results of a new RXTE observations of a high red-shift cluster are presented. It is shown that the most likely emission mechanism for these radiations is the inverse Compton scattering of the cosmic microwave background photons by the same electrons responsible for the radio radiation. Various scenarios for acceleration of the electrons are considered and it is shown that the most likely model is episodic acceleration by shocks or turbulence, presumably induced by merger activity, of high energy electrons injected into the inter-cluster medium by galaxies or active galactic nuclei.
MODEST: Modeling Stellar Evolution and (Hydro)dynamics
Authors: Hut Piet
Published: March 2016

Simulations of dense stellar systems currently face two major hurdles, one astrophysical and one computational. The astrophysical problem lies in the fact that several major stages in binary evolution, such as common envelope evolution, are still poorly understood. The best we can do in these cases is to parameterize our ignorance, in a way that is reminiscent of the introduction of a mixing length to describe convection in a single star, or an alpha parameter in modeling an accretion disk. The hope is that by modeling a whole star cluster in great detail, and comparing the results to the wealth of observational data currently available, we will be able to constrain the parameters that capture the unknown physics. The computational problem is one of composition: while we have accurate computer codes for modeling stellar dynamics, stellar hydrodynamics, and stellar evolution, we currently have no good way to put all this knowledge together in a single software environment. A year ago, a loosely-knit organization was founded to address these problems, MODEST for Modeling DEnse STellar systems, with nine working groups and a series of meetings that are held every half year. This report reviews the first year of this initiative. Much more detail can be found on the MODEST web site http://www.manybody.org/modest.html.
Young Star Clusters: Progenitors of Globular Clusters!?
Authors: Anders Peter , Alvensleben Uta Fritze – v. , Grijs Richard de
Published: March 2016

Star cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. Young clusters are observed to form in a variety of such galaxies, a substantial number resembling the progenitors of globular clusters in mass and size, but with significantly enhanced metallicity. From studies of the metal-poor and metal-rich star cluster populations of galaxies, we can therefore learn about the violent star formation history of these galaxies, and eventually about galaxy formation and evolution. We present a new set of evolutionary synthesis models of our GALEV code, with special emphasis on the gaseous emission of presently forming star clusters, and a new tool to compare extensive model grids with multi-color broad-band observations to determine individual cluster masses, metallicities, ages and extinction values independently. First results for young star clusters in the dwarf starburst galaxy NGC 1569 are presented. The mass distributions determined for the young clusters give valuable input to dynamical star cluster system evolution models, regarding survival and destruction of clusters. We plan to investigate an age sequence of galaxy mergers to see dynamical destruction effects in process.
Challenges in Stellar Models from Helioseismology to Asteroseismology
Authors: Turck-Chièze Sylvaine , Nghiem Phu Anh Phi , Piau Laurent
Published: March 2016

Experience in helioseismology provides guidance for modeling challenges in asteroseismology. It guides choices of targets and conditions of observation. The main objectives are the interplay between rotation and convection and the knowledge of the internal magnetic field. Progress on the structure of the outer layers is crucial to avoid mode identification problems.
Seismology of Solar Internal Rotation
Authors: Sekii Takashi
Published: March 2016

Helioseismologists have been highly successful in revealing how the solar interior differentially rotates, through observations of rotationally split eigen p modes of the Sun. What we currently know about the internal rotation of the Sun is reviewed, and outstanding issues are discussed.
Solar Meridional Flows: Recent Findings
Authors: Haber Deborah A. , Hindman Bradley W.
Published: March 2016

We report new measurements of the sun’s global meridional circulation within the near-surface shear layer for the years 1996 to 2003. The flows are obtained using the local helioseismic technique of ring analysis applied to MDI Dynamics Program data. The most recent estimates of the solar p-angle correction to this data have been incorporated. Previously published accounts that the solar meridional circulation possesses multiple cells within the northern hemisphere (Haber et al. 2002) are not contradicted by the new findings. We do find, however, that with the inclusion of the p-angle correction, cross-equator flows have been eliminated.
Observations and Interpretation of Subsurface Magnetic Structures
Authors: Cally P. S. , Crouch A. D.
Published: March 2016

Immediate subsurface local solar structures – flow, magnetic, and thermal – especially those associated with active regions, are of considerable interest, and are potentially accessible using high ℓ helioseismology. In recent years, classical modal seismology has been supplemented with new approaches, such as time-distance helioseismology, Hankel analysis, and acoustic holography. Results from time-distance helioseismology on shallow subsurface wave speed are at odds with those from the other methods. A simple model is presented which yields good agreement with the observed Hankel phase shifts of p modes passing through sunspots.
Review of SN Ia Progenitors
Authors: Schmidt Brian P.
Published: March 2016

Type la Supernovae have taken on a leading role in measuring extra-galactic distances providing key information about the Hubble Constant and providing evidence of an accelerating Universe. Unfortunately these conclusions are based on an empirical relationship between SN brightness and light curve shape rather than any deep physical understanding. A key ingredient to gaining physical understanding lies in understanding what becomes a SN la progenitor. Essentially all models require a binary system to push a white dwarf higher in mass. I will review the current attempts observational and theoretical to pin down the nature of these important astrophysical objects.
Ortho-To-Para Ratio of Cometary Water and Ammonia
Authors: Kawakita Hideyo , Watanabe Jun-ichi , Furusho Reiko , Fuse Tetsuharu
Published: March 2016

Since the time that the ortho-to-para ratio (OPR) of cometary water was first Determined from observations of Comet Halley, the real meaning of OPR has not been discussed in detail. Here we review the OPRs of water and ammonia and discuss the possibilities that the OPRs were modified in the coma or the nucleus. Our conclusion indicates that the OPRs were not altered after comet nucleus formation, i.e., the OPRs reflect the temperatures in the solar nebula or the pre-solar molecular cloud.
Light Scattering as a Clue to Cometary Dust Structure
Authors: Levasseur-Regourd A. Chantal , Hadamcik E. , Lasue J.
Published: March 2016

The linear polarization of comets depends upon the cometary dust physical properties, as well as upon the phase angle and the wavelength. The observed similarities and discrepancies provide drastic constraints on the physical properties of the dust. A series of measurements of light scattering properties on clouds of particles and of the aggregates they form under microgravity conditions should allow the interpretation of the observations in terms of physical properties of the dust.
A Mechanism of Crystallization of Cometary Silicates
Authors: Yamamoto Tetsuo , Chigai Takeshi
Published: March 2016

We propose a new mechanism of crystallization of cometary silicate. The crystallization is due to heat released by chemical reactions in the organic refractory mantle of Greenberg’s model of cometary dust induced by moderate heating by solar radiation. It is shown that the strength of the crystalline feature observed in the comets can be reproduced by the present mechanism of crystallization.
Stellar Abundances in Local Group Galaxies
Authors: Tolstoy Eline , Venn Kim
Published: March 2016

Here we describe some of our latest results from measuring detailed abundances in Local Group dwarf galaxies with the VLT. Combining spectroscopic abundances with Color-Magnitude diagrams allows the effective measurement of detailed chemical evolution with time in these galaxies. Although there are not yet significant numbers of individual stars observed in local group dwarf galaxies, the uniformity of the abundance patterns of the majority of stars in galaxies with very different star formation histories must hint at general properties of all star formation in these small systems.
Summary of IAU Joint Discussion 16, “The International Celestial Reference System, Maintenance and Future Realizations
Authors: McCarthy Dennis D.
Published: March 2016

The IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in July, 2003. Papers related to the maintenance of the International Celestial Reference System were presented in the one-day session, and these were followed by discussion that pointed out the need for standard nomenclature. This issue was addressed by the formation of a Division 1 Working Group on the subject. JD16 also pointed out the requirement for a dynamical expression for precession which was addressed by the creation of a Division 1 Working Group on Precession and the Ecliptic. It also showed that although plans are being implemented to provide reference frames for the future, there is a need for improved coordination of astrometric observations. Finally it should be noted that the discussion pointed out the concern for the future organization of IAU Division 1.
The Iron Project and the RmaX Project
Authors: Pradhan Anil K.
Published: March 2016

Ongoing activities under an international collaboration of atomic physicists and astrophysicists under the Iron Project and the RmaX Project, with applications to X-ray astronomy, are briefly described.
Atomic Physics Calculations for Iron L-line Spectra
Authors: Dubau Jacques , Porquet Delphine , Zabaydullin Oleg
Published: March 2016

Absorption L-lines of iron ions are observed, in spectra of Seyfert 1 galaxies by the new generation of X-ray satellites: Chandra and XMM-Newton. Lines associated to Fe 23+ to Fe16+ have been already observed in emission, in the solar corona and in laboratory. Whereas, those corresponding to Fe 15+ to Fe6+ have not been observed as emission lines, the upper level of the transition decaying preferentially by autoionization. Many atomic data are available for the first ion set. For the second set, some data have been recently published for n=2 to n’=3 transitions. We have recalculated them using another theoretical approach and have extended them to n’=4.
The CHIANTI Database
Authors: Landi E. , Dere K.P. , Young P.R. , Landini M. , Mason H.E. , Zanna G. Del
Published: March 2016

The CHIANTI database contains assessed atomic energy levels, wavelengths, radiative transition probabilities and excitation rates necessary to calculate line emissivities and synthetic spectra of a large number of ions of astrophysical interest. CHIANTI also includes a suite of programs to carry out plasma diagnostics. In the present paper we describe the contents of the CHIANTI database, its main applications and its future developments.
TIPTOPbase
Authors: Palmeri P. , Mendoza C.
Published: March 2016

An overview of the online atomic database referred to as TIPTOPbase is given, in particular its opacity server (OPserver) and current developments regarding online atomic structure calculations. Efforts to include atomic data for X-ray line modeling and to integrate TIPTOPbase within the International Virtual Observatory Alliance (IVOA) are also mentioned.
Distinguishing Models for ACIS Data of Diffuse Emission
Authors: Leahy D.A.
Published: March 2016

Discussed here is the issue of discriminating different spectral models for diffuse emission observations with the Chandra ACIS. First background models are considered. Then standard source models such as non-ionization equilibrium and ionization equilibrium models and models with different metal abundances are considered. The datasets used are from Chandra ACIS observations of diffuse emission, in particular of the Cygnus Loop supernova remnant.
JD18: Quasar Cores and Jets - poster-paper summary
Authors: Wall J V
Published: March 2016

Of the 17 poster papers presented at IAU25 Joint Discussion 18, three (1821, 1824,1834) are essentially theoretical, three (1828,1829,1831) deal with polarization, screens and absorbers, one (1818B) considers galaxy formation and evolution, 7 (1817,1820,1826,1830,1835,1836,1837) describe source structure and spectra, and three (1812,1818,1823) deal with Intra-Day Variability (IDV).
Galileo’s Exploration of Small Bodies
Authors: Johnson Torrence
Published: March 2016

The Galileo mission to the Jupiter system afforded the opportunity to make the first ever flyby observations of main belt asteroids. The first encounter, with 951 Gaspra, revealed an irregular, cratered surface that shows evidence of regolith optical space weathering processes. The second encounter, with 243 Ida, resulted in the discovery of the first confirmed satellite of an asteroid, Dactyl. Measurements of Dactyl’s orbit also allowed a useful determination of mass and density for Ida. In addition to these pioneering asteroid observations, Galileo also made observations of Jupiter’s small inner moons and found that they were the major source for material in Jupiter’s tenuous ring system. During it’s final data taking orbit in 2002, Galileo passed within about 250 km of the irregularly shaped satellite Amalthea. Determination of Amalthea’s mass from tracking data yields a bulk density for this small body of less than 1 gm/cc, suggesting a body of relatively high porosity. This is consistent with the growing body of data on small asteroid densities and estimates of their porosity.
Dawn Discovery Mission: Symbiosis with 1 AU Observations
Authors: Russell C. T.
Published: March 2016

The Dawn mission, the ninth in the series of NASA Discovery missions, is scheduled for launch in late May 2006 on a voyage to both Vesta and Ceres. The mission carries a framing camera, visible and infrared mapping spectrometer, gamma ray and neutron spectrometer, laser altimeter and magnetometer to understand and contrast these two very different bodies. Vesta apparently accreted dry, differentiated, and formed an iron core. Ceres apparently contains much water and ice and has remained relatively cool over its lifetime. The community of 1AU observers can help optimize the Dawn mission by improving the knowledge of Vesta and Ceres rotation axes, thus improving our knowledge of when regions and features will be best illuminated. The detection of any satellites would not just identify a potential hazard, and a secondary target of interest, but would also determine the mass of the primaries, enabling better mission planning. Characterization of the surface in any way, including identifying potential targets for detailed study, is also most welcome.
A Target for Rosetta
Authors: Schulz Rita
Published: March 2016

Comet 67P/Churyumov-Gerasimenko has been chosen as the new target of the Rosetta mission. A concise overview of the basic properties of the new target comet is given.
ISO: Asteroid Results and Thermophysical Modeling
Authors: Müller Thomas G.
Published: March 2016

Through a recently developed thermophysical model, observations from the Infrared Space Observatory (ISO) were combined with visual photometry, lightcurves, close-up observations and direct measurement. In this way, many applications were possible, ranging from simple diameter and albedo determination of serendipitously seen asteroids to sophisticated studies of mineralogic aspects and regolith properties, like emissivity, roughness or thermal inertia for well-known asteroids. The possibility to combine all sources of information in one single model lead also to a better understanding of thermophysical effects, like beaming or the before/after opposition effect. Thus, the mineralogic signatures can be recognized easier and asteroid data from infrared surveys and individual IR photometry can be interpreted more accurately, even in cases where shape or rotational behaviour are not known. Some well-studied asteroids are now even considered as excellent far-infrared calibrators.
Extended Families in the Main Belt and in the Trojan Swarms
Authors: Knezevic Zoran , Milani Andrea
Published: March 2016

The availability of highly accurate synthetic proper elements for a large number of asteroids made possible detailed studies of the structure of asteroid families. The entire region of the Vesta family is dominated by bodies with D < 7 km. The large spread of family members appears to be primarily due to Yarkovsky mobility, a strongly size-dependent. The proper elements of the asteroids the region (except close to mean motion resonances) are stable over very long time spans; thus chaotic diffusion could not play a significant role. The total volume of the family members with diameter less than 7 km amounts approximately to 6 x 104 cubic km, the volume of a crater with 100 km diameter and average depth 7 km. If the albedo feature, visible in the Hubble Space Telescope images, is really a crater its volume could be even larger. Thanks to the recently computed catalogs of proper elements for 1167 trojans, there are now confirmed dynamical families in the trojan swarms. This allows to begin to study the collisional evolution with constraints from observations.
Introducing Joint Discussion 20: Frontiers of High Resolution Spectroscopy
Authors: Linsky Jeffrey L.
Published: March 2016

This paper introduces the rationale and program of Joint Discussion 20, Frontiers of High Resolution Spectroscopy, which took place on 2003 July 23-24 during the IAU General Assembly in Sydney Australia.
High Spatial/Spectral Resolution Studies of Eta Carinae
Authors: Gull Theodore R. ,   Eta Carinae HST Treasury Team
Published: March 2016

We have used the high spatial and high spectral resolution of the Space Telescope Imaging Spectrograph (STIS) to study Eta Carinae and the Homunculus. Since the last minimum in 1998.0, CCD spectral modes have followed changes in the Eta Carinae, and large-scale changes in the Homunculus. Since 2001.7, MAMA echelle-mode observations have followed changes in the Eta Carinae and the very nearby ejecta through the 2003.5 minimum. Very significant changes in the star and nebular occur as the X-Ray drop occurs in the minimum.
Molecular Hydrogen in the High Redshift Damped Ly-α Systems:
Authors: Srianand R. , Petitjean P. , Ledoux C. , Ferland G.
Published: March 2016

This review talk summarizes the main results obtained from the just completed survey of molecular hydrogen in damped Lyman-a systems (DLAs). Preliminary results based on modeling ionization conditions and chemical network is also presented. The presence of H2 and fine-structure lines of C 1 in 13-20% of DLAs allow one to investigate the physical conditions using the techniques that are commonly used in the studies of the Galactic ISM. It is shown that the DLAs with H2 trace regions with higher density, lower temperature, moderate to high dust depletion, and local star-formation. Absence of H2 in DLAs with moderate dust depletion could just be a simple consequence of lower densities in the systems.
Molecular Absorption Lines in Galaxies
Authors: Wiklind Tommy
Published: March 2016

Molecular absorption lines have become an important tool in studying the astrochemistry of the dense and cold interstellar medium in both our own Galaxy and high redshift systems. The sensitivity is to first order only dependent on the observed continuum flux. Apart from a few nearby galaxies, molecular absorption lines have been used to study the molecular ISM in 4 galaxies at redshifts 0.25-0.89. A large number of molecular species and transitions have been observed, allowing a detailed comparison with molecular gas in our own Galaxy. Planned instruments, such as ALMA, will allow studies of a larger number of molecular absorption line systems.
Molecular Line Observations in the Magellanic Clouds
Authors: Rubio Mónica
Published: March 2016

We review the present knowledge of molecular line studies and its relation to interstellar medium properties in the Large and Small Magellanic Clouds. The physical and chemical properties of the molecular gas together with the abundance of different molecular species will be discussed.
Magellanic Diffuse Interstellar Bands and Carbon Chemistry
Authors: Ehrenfreund P. , Cox N. , Cami J. , Foing B.H. , Kaper L. , d’Hendecourt L. , Maier J.P. , Salama F. , Sarre P. , Snow T. , Sonnentrucker P.
Published: March 2016

With the Ultraviolet Visual Echelle Spectrograph mounted at the Very Large Telescope, we have observed at unprecedented spectral resolution the absorption spectrum toward reddened stars in the Magellanic Clouds over the wavelength range of 3500-10500 Å. This range covers the strong transitions associated with neutral and charged large carbon molecules of varying sizes and structures. We report the first detection of diffuse interstellar bands (DIBs) at 5780 and 5797 Å in the Small Magellanic Cloud and the variation of those DIBs toward several targets in the Large Magellanic Cloud. The variation of DIBs in the Magellanic Clouds compared with Galactic targets may be governed by a combination of the different chemical processes prevailing in low-metallicity regions and the local environmental conditions. The analysis of high-resolution absorption spectra allows us to reveal the global effects in the chemistry and recycling of cosmic dust in the Magellanic Clouds which are relevant for the chemical pathways forming large organic molecules in external galaxies.
Cassini/Huygens Mission To Saturn: Results And Prospects
Authors: Matson Dennis L. , Lebreton Jean-Pierre , Spilker Linda
Published: March 2016

The Cassini spacecraft was launched in October, 1997. Since then it has been on an interplanetary trajectory aimed toward Saturn and arriving there on July 1, 2004. En route, Cassini has flown by Venus, the Earth, and Jupiter. Each of these events yielded new scientific results, (e.g., 11 papers in J. Geophys. Res. 106, 30099-30279.) The Cassini flyby of Jupiter, with Galileo already in Jovian orbit, enabled the first-ever simultaneous measurements by two spacecraft at an outer planet. This fortuitous event provided a unique opportunity to investigate the giant planet’s magnetic field and the properties of the Jovian system. It provided a focused period for intensive observations of Jupiter and cooperation with investigators using Galileo, Hubble, Chandra, and ground-based observatories. The results achieved at Jupiter were stunning (e.g., 8 articles in Nature 415, 965-1005, February 28, 2002). Recent results and the current status of the spacecraft and mission will be discussed. Of note are the dates of July 1, 2004 when Cassini goes into orbit about Saturn and January 14, 2005 when Huygens enters the atmosphere of Titan. The Cassini/Huygens mission is a joint undertaking by NASA and ESA, with ASI as a partner via a bilateral agreement with NASA.
Orbital Evolution of the Kuiper Belt
Authors: Morgan Charles , Prentice Andrew
Published: March 2016

The observed distribution of trans-Neptunian objects (TNOs) implies that they originally orbited in a narrow ring of radius 41 AU. The mass of the largest TNO was around 1 — 4 x 1026 g.
Site Testing at Dome C—Cloud Statistics from the ICECAM Experiment
Authors: Ashley Michael C. B. , Burton Michael G. , Calisse Paolo G. , Phillips Andre , Storey John W. V.
Published: March 2016

Analysis of sky images obtained from an automated experiment at Dome C, Antarctica, at 2-hourly intervals from February to November 2001 show cloud-free conditions 74% of the time. This augurs well for the prospects of future astronomical observatories at this site.