bluuebunny/crossref_metadata_2025 huggingface dataset:
Shifting dominance of Shigella species in men who have sex with men
Authors: RATNAYAKE R. , ALLARD R. , PILON P. A.
Published: April 2012

Historically, Shigella sonnei has dominated other Shigella species infection in men who have sex with men (MSM) in Montréal. In early 2010, Toronto reported increased proportions of the more pathogenic S. flexneri, HIV co-infection and MSM in shigellosis cases since 2009. Analytical methods were used to assess whether S. flexneri had dominated Montréal's MSM cases since 2009 and whether changes had occurred in notifications in MSM and HIV-co-infected MSM. S. flexneri increased by 6·7% per month since 2007 and predominated in MSM since 2009 without changes in HIV co-infection or similar shifts in the general population. The results suggest that the surveillance of Shigella species in order to detect species shifts is beneficial for surveillance, given the potential for increased transmission and severity of S. flexneri in HIV-positive MSM.
The Use of Virtual Observatory Databases in Binary Star Research
Authors: Peters Geraldine J.
Published: April 2012

The rapidly-accumulating archives of ground-based and spacecraft data worldwide that are being linked together through the International Virtual Observatory Alliance (IVOA) provide the binary star community with unparalleled opportunities for research. The main databases that are available to the astronomical community through the IVOA are discussed. Data from long-lasting spacecraft missions such as IUE are especially valuable for studying long-term variability. Some examples of current research on close binary stars that is being carried through with UV spectra from the IUE archive are presented. Included are the search for O-subdwarf companions to bright Be stars and some results from an ongoing investigation of the Double Periodic Variable phenomenon in Algol binaries.
Multi-Technique Study of the X-Ray Binary Cygnus X-1
Authors: Karitskaya E. A.
Published: April 2012

Short review of our 36-year Cyg X-1 study using multi-technique methods and based on our optical photometric, high-resolution spectral and spectropolarimetrical observations.
Light Curve and Orbital Period Analysis of the Eclipsing Binary AT Peg
Authors: Liakos Alexios , Niarchos Panagiotis , Budding Edwin
Published: April 2012

CCD photometric observations of the Algol-type eclipsing binary AT Peg have been obtained. The light curves are analyzed with modern techniques and new geometric and photometric elements are derived. A new orbital period analysis of the system, based on the most reliable timings of minima found in the literature, is presented and apparent period modulations are discussed with respect to the Light-Time effect (LITE) and secular changes in the system. The results of these analyses are compared and interpreted in order to obtain a coherent view of the system's behaviour.
The Third Body in the Eclipsing Binary AV CMi: Hot Jupiter or Brown Dwarf?
Authors: Liakos Alexios , Mislis Dimitris , Niarchos Panagiotis
Published: April 2012

New transit light curves of the third body in the system AV CMi have been obtained. The eclipsing pair's light curves were re-analysed with the W-D code and new absolute elements were derived for the two components. Moreover the new light curves (together with those given by Liakos & Niarchos 2010) of the third body transiting one of the components were analysed with the Photometric Software for Transits (PhoS-T). The results from both analyses are combined with the aim to study the nature of the third component.
Multiwavelength Photometry of the Young Intermediate Mass Eclipsing Binary TY CrA
Authors: Ammler-von Eiff M. , Vaňko M. , Pribulla T. , Covino E. , Neuhäuser R. , Joergens V.
Published: April 2012

One of the handful of known PMS eclipsing binaries is a component of the spectroscopic triple TY CrA. Its secondary component is particularly interesting since it is a star of relatively high mass (1.64 M⊙) which is still on the pre-main sequence. The eclipsing binary was analyzed in the optical wavelength range ~10 years ago, however, the crucial secondary eclipse minimum is very shallow. Therefore, we are obtaining new photometry in both optical and near-IR bands. We present first observations in (BVRI) which show that the secondary eclipse depth increases to about 0.1 mag in the I band. The increased eclipse depth with respect to other bands will help to better determine the colours and dimensions of the system. Furthermore, we show and discuss first near-IR observations of the primary eclipse. In addition to the light curves we are obtaining radial velocities in order to pin down the orbital parameters of the triple. Our first observations agree with the orbital parameters derived ~10 years ago.
Some Developments of the Weak Stellar Magnetic Field Determination Method for the Example of Cygnus X-1
Authors: Bochkarev N. G. , Karitskaya E. A.
Published: April 2012

Some developments of measurements of the weak stellar magnetic fields by the least square technique applied to spectropolarimetric data are proposed and used for the X-ray binary Cyg X-1 = HDE 226868 (the optical counterpart is an O 9.7 supergiant).
O-C Analysis of Selected 3-Body Systems
Authors: Ogłoza W. , Kreiner J. M. , Stachowski G. , Winiarski M. , Zakrzewski B. , Doğru S. , Aliçavuş F. , Demircan O. , Erdem A.
Published: April 2012

This paper presents the results of the analysis of (O-C) diagrams of four eclipsing variables. The diagrams are based on times of minima collected in the Cracow database, which contains times of minima found in the literature, from observations at Mt. Suhora and Ulupinar Observatories, or determined using publicly-available photometric surveys (NSVS, ASAS etc).
Is EQ Boo a Quadruple System?
Authors: Volkov Igor M. , Chochol Drahomír , Volkova Natalia S. , Nikolenko Igor V.
Published: April 2012

We present the precise multicolour photometry of the eclipsing variable EQ Boo (P = 5d.43, V = 8m.8), which is component “A” of the visual double star ADS 9422 (F7 V+G0 V, ρ = 1.3”, Δmag = 0.7). From the analysis of these data, we can propose the existence of the fourth component with a late spectral type.
Long-Term Monitoring of Polars
Authors: Kalomeni B.
Published: April 2012

We present long-term observations of magnetic cataclysmic variables AM Her, AN UMa, AR UMa, DP Leo, and V1309 Ori obtained with the ROTSEIIId telescope. All data have been analysed and preliminary results indicate periods of 170 days, 217 days, and 180 days for AM Her, AN UMa, and AR UMa, respectively.
The Apsidal Motion of the Eclipsing Binary Systems GSC 4487 0347 and GSC 4513 2537
Authors: Kozyreva V. S. , Kusakin A. V. , Krajci T. , Menke J. , Tsvetkova T. M.
Published: April 2012

The eclipsing variable stars GSC 44870347 and GSC 4513 2537 are recently discovered binary systems (Otero et al., 2006) with orbital periods 1d.99 and 6d.33 days. We carried out the photometric observations of these eclipsing binaries from 2009-2010 using a CCD-array at the Tien-Shan Observatory in Kazakstan, at the Crimea Station of the Sternberg Astronomical Institute, at the Astrokolkhoz Observatory in New Mexico (AAVSO), while the spectrophotometric observations were obtained at the Starlight Farm Observatory in Barnesville, USA.
Challenges to Observations of Low Mass Binaries
Authors: Kafka Stella
Published: April 2012

Low mass stars in binaries are frequently used as unique tools to determine and establish fundamental stellar parameters. The need for their study and understanding has led to developing new instruments, new observational techniques and improved theoretical models. The relatively recent discovery of exoplanets and their study as the low-mass constituents around other stars is now opening new horizons in binary research. Here, I examine the most common observational challenges in studying low mass binaries across the electromagnetic spectrum.
The Impact of Red Noise in Radial Velocity Planet Searches
Authors: Baluev Roman V.
Published: April 2012

We demonstrate that moderate exoplanet radial velocity searches are often subject to the effect of the correlated (red) radial velocity noise. When disregarded, this effect may induce strong distortions in the results of the time series analysis and, ultimately, can even lead to false planet detections. We construct a maximum-likelihood algorithm, which is able to manage this issue rather efficiently.
Multiband Transit Light Curve Modeling of WASP-4
Authors: Nikolov N. , Koppenhoefer J. , Lendl M. , Henning T. , Greiner J.
Published: April 2012

We report on the simultaneous g′,r′,i′,z′ multiband, high time sampling (18-24s) ground-based photometric observations, which we use to measure the planetary radius and orbital inclination of the extrasolar transiting hot Jupiter WASP-4b. We recorded 987 images during three complete transits with the GROND instrument, mounted on the MPG/ESO-2.2m telescope at La Silla Observatory. Assuming a quadratic law for the stellar limb darkening we derive system parameters by fitting a composite transit light curve over all bandpasses simultaneously. To compute uncertainties of the fitted parameters we employ the Bootstrap Monte Carlo Method. The three central transit times are measured with precision down to 6 s. We find a planetary radius Rp = 1.413 ± 0.020RJup, an orbital inclination i = 88.°57 ± 0.45° and calculate new ephemeris, a period P = 1.33823144 ± 0.00000032 days and reference transit epoch T0 = 2454697.798311 ± 0.000046 (BJD). The analysis of the new transit mid-times in combination with previous measurements imply a constant orbital period and no compelling evidence for TTVs due to additional bodies in the system.
Panel Discussion I
Authors: Allard F. , Batten A. , Budding E. , Devinney E. , Eggleton P. , Hatzes A. , Hubeny I. , Kley W. , Lammer H. , Linnell A. , Trimble V. , Wilson R. E.
Published: April 2012

M. Richards: Several talks today have expressed fuzzy boundaries to describe the objects called “stars.” Is the following classification correct? Are stars restricted to objects that have masses greater than 0.089 solar masses and begin making energy with hydrogen burning? Do we include the stellar remnants: the white dwarfs and neturon stars? Do we include the brown dwarfs because they burn lithium or deuterium. We know that planets are not in this group since they have no energy production.
Binaries and Multiple Systems Observed with the CHARA, NPOI, SUSI and VLTI Interferometric Eyes
Authors: Stee Philippe
Published: April 2012

In this review I will present recent results between 2007 and 2011 based on interferometric observations of binaries and multiple systems with the VLTI, NPOI, SUSI and CHARA instruments. I will also explain the kind of constraints an interferometer can provide in order to better understand the physics of multiple systems.
Observing Faint Companions Close to Bright Stars
Authors: Serabyn Eugene
Published: April 2012

Progress in a number of technical areas is enabling imaging and interferometric observations at both smaller angular separations from bright stars and at deeper relative contrast levels. Here we discuss recent progress in several ongoing projects at the Jet Propulsion Laboratory. First, extreme adaptive optics wavefront correction has recently enabled the use of very short (i.e., blue) wavelengths to resolve close binaries. Second, phase-based coronagraphy has recently allowed observations of faint companions to within nearly one diffraction beam width of bright stars. Finally, rotating interferometers that can observe inside the diffraction beam of single aperture telescopes are being developed to detect close-in companions and bright exozodiacal dust. This paper presents a very brief summary of the techniques involved, along with some illustrative results.
Adaptive Optics Observations of Exoplanets, Brown Dwarfs, and Binary Stars
Authors: Hinkley Sasha
Published: April 2012

The current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Further, the prevalence of aperture masking interferometry in the field of high contrast imaging is also allowing observers to sense massive, young planets at solar system scales (~3–30 AU)— separations out of reach to conventional direct imaging techniques. Such observations can provide snapshots at the earliest phases of planet formation—information essential for constraining formation mechanisms as well as evolutionary models of planetary mass companions. As a demonstration of the power of this technique, I briefly review recent aperture masking observations of the HR 8799 system. Moreover, all of the aforementioned techniques are already extremely adept at detecting low-mass stellar companions to their target stars, and I present some recent highlights.
Modelling of an Eclipsing RS CVn Binary: V405 And
Authors: Vida Krisztián , Oláh Katalin , Kővári Zsolt
Published: April 2012

V405 And is an ultrafast-rotating (Prot ≈ 0.46 days) eclipsing binary. The system consists of a primary star with radiative core and convective envelope, and a fully convective secondary. Theories have shown that stellar structure can depend on magnetic activity, i.e., magnetically active M-dwarfs should have larger radii. Earlier light curve modelling of V405 And indeed showed this behaviour: we found that the radius of the primary is significantly larger than the theoretically predicted value for inactive main sequence stars (the discrepancy is the largest of all known objects), while the secondary fits well to the mass-radius relation. By modelling our recently obtained light curves, which show significant changes of the spotted surface of the primary, we can find further proof for this phenomenon.
Doppler Tomography in 2D and 3D of the X-ray Binary Cyg X-1 for June 2007
Authors: Sharova O. I. , Agafonov M. I. , Karitskaya E. A. , Bochkarev N. G. , Zharikov S. V. , Butenko G. Z. , Bondar A. V.
Published: April 2012

The 2D and 3D Doppler tomograms of X-ray binary system Cyg X-1 (V1357 Cyg) were reconstructed from spectral data for the line HeII 4686Å obtained with 2-m telescope of the Peak Terskol Observatory (Russia) and 2.1-m telescope of the Mexican National Observatory in June, 2007. Information about gas motions outside the orbital plane, using all of the three velocity components Vx, Vy, Vz, was obtained for the first time. The tomographic reconstruction was carried out for the system inclination angle of 45°. The equal resolution (50 × 50 × 50 km/s) is realized in this case, in the orbital plane (Vx, Vy) and also in the perpendicular direction Vz. The checkout tomograms were realized also for the inclination angle of 40° because of the angle uncertainty. Two versions of the result showed no qualitative discrepancy. Details of the structures revealed by the 3D Doppler tomogram were analyzed.
PTPS Candidate Exoplanet Host Star Radii Determination with CHARA Array
Authors: Zieliński Paweł , Vaňko Martin , Baines Ellyn , Niedzielski Andrzej , Wolszczan Aleksander
Published: April 2012

We propose to measure the radii of the Penn State - Toruń Planet Search (PTPS) exoplanet host star candidates using the CHARA Array. Stellar radii estimated from spectroscopic analysis are usually inaccurate due to indirect nature of the method and strong evolutionary model dependency. Also, the so-called degeneracy of stellar evolutionary tracks due to convergence of many tracks in the giant branch decreases the precision of such estimates. However, the radius of a star is a critical parameter for the calculation of stellar luminosity and mass, which are often not well known especially for giants. With well determined effective temperature (from spectroscopy) and radius, the luminosity may be calculated precisely. In turn also stellar mass may be estimated much more precisely. Therefore, direct radii measurements increase precision in the determination of planetary candidates masses and the surface temperatures of the planets.
The MUNI Photometric Archive
Authors: Chrastina Marek , Zejda Miloslav , Mikulášek Zdeněk
Published: April 2012

In the 1990s of the last century, CCD cameras became more reachable. Due to many advantages of CCD cameras, astronomers began using them as the primary detector for photometry of stellar objects. A typical observatory, which operates one telescope at a time, obtained 0.5 TB of raw data during two decades, that means one million about 500 kB-sized files. There are several observatories in the Czech Republic and Slovakia (taking into account all scientific, public as well as private ones). A rough estimate of the total amount of this photometric data is 10 TB, which could be a very interesting source of observational data. Unfortunately, these data are not available online. These data are stored in observatory archives in arbitrary format. Often it is not even possible to find requested data. We have decided to change this state by establishing a common archive of raw photometric data, which would be available online together with tools for searching, listing etc. We already defined the data format, file and directory structure of our archive. We developed sophisticated tools for archive maintenance as well. Our goal is to provide data storage with simple and straightforward access and we are ready to interconnect with the VO right after the IVOA Photometry Data Model will be released.
Stellar to Substellar Model Atmospheres
Authors: Allard France , Homeier Derek , Freytag Bernd
Published: April 2012

The spectral transition from Very Low Mass stars (VLMs) to brown dwarfs (BDs) and planetary mass objects (Planemos) requires model atmospheres that can treat line, molecule, and dust-cloud formation with completeness and accuracy. One of the essential problems is the determination of the surface velocity field throughout the main sequence down to the BD and planemo mass regimes. We present local 2D and 3D radiation hydrodynamic simulations using the CO5BOLD code with binned Phoenix gas opacities, forsterite dust formation (and opacities) and rotation. The resulting velocity field vs depth and Teff has been used in the general purpose model atmosphere code Phoenix, adapted in static 1D spherical symmetry for these cool atmospheres. The result is a better understanding of the spectral transition from the stellar to substellar regimes. However, problems remain in reproducing the colors of the dustiest brown dwarfs. The global properties of rotation can change the averaged spectral properties of these objects. Our project for the period 2011-2015 is therefore to develop scaled down global 3D simulations of convection, cloud formation and rotation thanks to funding by the Agence Nationale de la Recherche in France.
Chemical History of Algol and its Components
Authors: Kolbas V. , Pavlovski K. , Southworth J. , Lee C.-U. , Lee J. W. , Kim S.-L. , Kim H.-I.
Published: April 2012

We present a new observational project to study the hierarchical triple stellar system Algol, concentrating on the semidetached eclipsing binary at the heart of the system. Over 140 high-resolution and high-S/N spectra have been secured, of which 80 are from FIES at the Nordic Optical Telescope, La Palma, and the remainder were obtained with BOES at the Bohyunsan Optical Astronomy Observatory in Korea. All three components were successfully detected by the method of spectral disentangling, which yields the individual spectra of the three stars and also high-quality spectroscopic elements for both the inner and outer orbits. We present a detailed abundance study for the mass-accreting component in the inner orbit, which holds information on the history of mass transfer in the close inner binary system. We also reveal the atmospheric parameters and chemical composition of the tertiary component in the outer orbit.
Applying the Steepest Descent Method with BINSYN on RY Per Photometry
Authors: Sudar D. , Božić H. , Ruždjak D.
Published: April 2012

Recent studies of the Algol-type binary RY Per presented strong evidence that there is an accretion disk around the primary in the system. We used new UBV photometry from Hvar Observatory and the BINSYN software package in order to determine the basic parameters of the disk. The search for the best parameter set was performed with a fully automated steepest descent method. The resulting disk is large and visible at all orbital phases. Somewhat surprising is the large mass transfer rate which should be tied with, currently unreported, secular period changes.
Quantitative Spectroscopy of Close Binary Stars
Authors: Pavlovski K. , Southworth J.
Published: April 2012

The method of spectral disentangling has now created the opportunity for studying the chemical composition in previously inaccessible components of binary and multiple stars. This in turn makes it possible to trace their chemical evolution, a vital aspect in understanding the evolution of stellar systems. We review different ways to reconstruct individual spectra from eclipsing and non-eclipsing systems, and then concentrate on some recent applications to detached binaries with high-mass and intermediate-mass stars, and Algol-type mass-transfer systems.
The Broadening Functions Technique
Authors: Rucinski Slavek M.
Published: April 2012

Essential assumptions and features of the Broadening Function (BF) technique are presented. A distinction between BF determination and the BF concept and utilization is made. The BF's can be determined in various ways. The approach based on linear deconvolution involving stellar templates, as used during the DDO program (1999 – 2008) is described, but the LSD technique would also give excellent results. The BF concept to prove and/or verify photometric light-curve solutions has so far been very limited to only a few W UMa-type binaries, with AW UMa giving particularly unexpected results.
Constrained Genetic Disentangling of Close Binary Spectra
Authors: Kolbas V. , Pavlovski K.
Published: April 2012

The spectral disentangling technique makes possible separation of individual component spectra in binary or multiple systems, and determination of the orbital elements in a self-consistent way. Since its introduction, a number of variants of their basic idea have been implemented. We present yet another ‘direct’ approach using optimization by genetic algorithm. Starting with an initial random flux distribution representing individual spectra, genetic optimization returns both individual component spectra and an optimal set of orbital parameters only constrained by time-series of the observed composite spectra of the binary system. Benchmark tests on V453 Cyg, which is an eclipsing binary with total eclipse, as well as tests on the artificial time-series spectra, have proven that ‘constrained genetic disentangling’ is performing correctly and efficiently, albeit with high demand on CPU time. Since genetic optimization can be easily parallelized, we expect our second release to run on cluster in a less time-consuming way.
T Tauri Binaries in Orion: Evidence for Accelerated and Synchronized Disk Evolution
Authors: Daemgen Sebastian , Petr-Gotzens Monika G. , Correia Serge
Published: April 2012

In order to trace the role of binarity for disk evolution and hence planet formation, we started the currently largest spatially resolved near-infrared photometric and spectroscopic study of the inner dust and accretion disks of the individual components of 27 visual, 100–400 AU binaries in the Orion Nebula Cluster (ONC). We study the frequency of Brackett-γ (2.165μm) emitters to assess the frequency of accretion disk-bearing stars among the binaries of the ONC: only 34±9% of the binary components show signs of accretion and, hence, the presence of gaseous inner disks—less than the fraction of gas accretion disks among single stars of the ONC of ~50%. Additionally, we find a significant difference between binaries above and below 200 AU separation: no close systems with only one accreting component are found. The results suggest shortened disk lifetimes as well as synchronized disk evolution.
The AstraLux Binary M Dwarfs Survey
Authors: Bergfors Carolina , Brandner Wolfgang , Hippler Stefan , Henning Thomas , Janson Markus , Hormuth Felix
Published: April 2012

Binary/multiple properties provide clues to the formation of stars. In the AstraLux binary survey, we use the Lucky Imaging technique to search for companions to a large sample of young, nearby M dwarfs. We present results from observations of the first sub-sample, consisting of 124 M dwarfs in the southern sky.
New Approach for Solution of the Planet Transit Problem
Authors: Kjurkchieva Diana P. , Dimitrov Dinko P.
Published: April 2012

We propose a new approach for a solution of the planet transit problem that is based on numerical calculation of integrals. The paper presents our method for the case of linear limb-darkening law and orbital inclination i = 90°, and illustrates the work of the code PTS written on the basis of our approach.
Searching for the Signatures of Terrestrial Planets in “Hot” Analogs
Authors: González Hernández J. I. , Delgado Mena E. , Israelian G. , Sousa S. G. , Santos N. C. , Udry S.
Published: April 2012

The Sun has been suggested to have a slightly low refractory-to-volatile abundance ratio when compared with field solar twins. This result may be interpreted as due to the fact that the refractory elements were trapped in rocky planets at the formation of the Solar System.

A detailed and differential chemical abundance study was already performed in order to investigate this hypothesis in solar analogs with and without detected planets using high-resolution and high-S/N HARPS and UVES spectra of a relatively large sample of solar analogs with and without planets. We obtained very similar behaviours for both samples of stars with and without planets, even for two stars with super-Earth-like planets, which may indicate that this solar trend may not be related to the presence of terrestrial planets.

The depletion signature should be imprinted once the convection zone reaches the current size. This suggests that stars hotter than the Sun should show this effect enhanced, due to their narrower convective zone. However, to avoid non-LTE, 3D, and other effects, we need to identify “hot” analogs with a Teff ~ 6100 K, to perform a differential analysis.

Here, we present the preliminary results of our analysis using HARPS and UVES high-resolution and high-S/N spectra of a sample of ~ 60 “hot”analogs with and without planets, trying to search for some “hot” reference analogs.
Calibrating Ultracool Atmospheres with Benchmark Companions from WISE+2MASS
Authors: Gomes Joana I. , Pinfield David , Day-Jones Avril , Jones Hugh , Burningham Ben , Marocco Federico , Zhang ZengHuan , van Spaandonk Lieke
Published: April 2012

The complexities of ultracool atmospheres are best confronted by observations of ultracool dwarfs (UCDs) with well known physical properties (luminosity, mass, Teff, log(g), [M/H]), so-called “benchmark objects.” We present two discoveries from a new WISE+2MASS search for benchmark wide companions to Hipparcos and Gliese stars. This survey combination provides a powerful tool to confirm new companions using color-magnitude and common proper motion selections, and also yield full NIR-MIR measurements of the ultracool emission. These primary companions are providing important constraints on the age and composition of the benchmark brown dwarf, and the new discoveries add to our growing population of benchmarks that is providing crucial tests of ultracool physics.
NSVS 01031772 Cam: A New Low-Mass Triple?
Authors: Wolf M. , Zasche P. , Hornoch K. , Chrastina M. , Janík J. , Zejda M.
Published: April 2012

We present a photometric study of the newly discovered low-mass eclipsing binary NSVS 01031772 Cam based on observations obtained at Ondřejov observatory from 2007 – 2011.
CCD Photometric Study of the Puzzling W UMa-type Binary TZ Boo
Authors: Christopoulou P.-E. , Papageorgiou A. , Chrysopoulos I.
Published: April 2012

The puzzling W-UMa type binary TZ Boo has been monitored at the University of Patras, Observatory from March to July 2010. Photometric solutions were determined through an analysis of the complete BVRI light curves with PHOEBE (Wilson-Devinney code) and published spectroscopic data. This low mass ratio binary turns out to be a deep overcontact system with f = 52.5% of A-subtype. A conservative spot model has been applied to fit the particular features of light curves. Based on our 7 new light minimum times and all others compiled from the literature over 70 years, we studied the orbital period from the O-C curve.
Modeling Fluid Flow Effects in Close Binary and Protoplanetary Systems
Authors: Montgomery M. M.
Published: April 2012

Accretion disks around some white dwarfs in Cataclysmic Variables are thought to tilt around the line of nodes by the lift force acting at the disk's center of pressure. We investigate whether protoplanetary disks can also experience disk tilt. We find that lift may be possible by an asymmetric, net uni-directional, in-falling gas/dust stream overflowing a bluff body (e.g., Class I sources) or inner annuli of young Class II sources if gas/dust is still in-falling and the aspect ratio and disk surface area are large enough. However, inner disks of Class II sources LkCa 15, UX Tau A, and Rox 44 are not large enough, and therefore disk tilt is not likely.
Closing Remarks
Authors: Richards Mercedes T.
Published: April 2012

The conference organizers are grateful to everyone who came, from all parts of the world, to share this experience with us. There were one hundred and seventy-seven participants from thirty-one countries. We thank the speakers, session chairs, distinguished panelists, the SOC members, the LOC members led by Theo Pribulla and Laco Hric, and Aleš Kucera, Director of the Astronomical Institute of the Slovak Academy of Sciences. Special thanks go to Richard Komžík for ensuring the smooth operation of the computer and audio-visual support for the conference.
Arguing Global Environmental Constitutionalism
Authors: Kotzé Louis J.
Published: April 2012

The current global environmental law and governance regime has been designed primarily to attend to the worsening ecological crisis. Evidence, however, suggests that the regime is far from achieving its goal and it is failing in its efforts to solve what people perceive to be pervasive global environmental problems. There is little doubt that this regime is in need of urgent reforms and/or re-situation in a decidedly different paradigm. This article proposes that global constitutionalism, while no panacea, could contribute to these paradigm-shifting reforms by providing a new perspective through which to view the current deficient global environmental law and governance regime and, in real terms, ameliorating some of the deficiencies of the regime through a normative process of constitutionalization.
The observed evolution of oceanic pCO2 and its drivers over the last two decades
Authors: Lenton Andrew , Metzl Nicolas , Takahashi Taro , Kuchinke Mareva , Matear Richard J. , Roy Tilla , Sutherland Stewart C. , Sweeney Colm , Tilbrook Bronte
Published: April 2012

We use a database of more than 4.4 million observations of ocean pCO2 to investigate oceanic pCO2 growth rates. We use pCO2 measurements, with corresponding sea surface temperature and salinity measurements, to reconstruct alkalinity and dissolved inorganic carbon to understand what is driving these growth rates in different ocean regions. If the oceanic pCO2 growth rate is faster (slower) than the atmospheric CO2 growth rate, the region can be interpreted as having a decreasing (increasing) atmospheric CO2 uptake. Only the Western subpolar and subtropical North Pacific, and the Southern Ocean are found to have sufficient spatial and temporal observations to calculate the growth rates of oceanic pCO2 in different seasons. Based on these regions, we find the strength of the ocean carbon sink has declined over the last two decades due to a combination of regional drivers (physical and biological). In the subpolar North Pacific reduced atmospheric CO2 uptake in the summer is associated with changes in the biological production, while in the subtropical North Pacific enhanced uptake in winter is associated with enhanced biological production. In the Indian and Pacific sectors of the Southern Ocean a reduced winter atmospheric CO2 uptake is associated with a positive SAM response. Conversely in the more stratified Atlantic Ocean sector enhanced summer uptake is associated with increased biological production and reduced vertical supply. We are not able to separate climate variability and change as the calculated growth rates are at the limit of detection and are associated with large uncertainties. Ongoing sustained observations of global oceanic pCO2 and its drivers, including dissolved inorganic carbon and alkalinity, are key to detecting and understanding how the ocean carbon sink will evolve in future and what processes are driving this change.
Atmospheric CO2 over the last 1000 years: A high‐resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core
Authors: Ahn Jinho , Brook Edward J. , Mitchell Logan , Rosen Julia , McConnell Joseph R. , Taylor Kendrick , Etheridge David , Rubino Mauro
Published: April 2012

We report a decadally resolved record of atmospheric CO2 concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre‐industrial period is a rapid ∼7 ppm decrease of CO2 in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO2 decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO2 records, but the true magnitude of the decrease remains unclear. Atmospheric CO2 variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo‐Pacific sea surface temperature. However, the exact relationship between CO2 and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high‐precision CO2 records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO2 change on centennial to multicentennial time scales, and clearly show that atmospheric CO2 has been increasing above preindustrial levels since ∼1850 A.D.
P‐V‐T equation of state of MgSiO3 perovskite based on the MgO pressure scale: A comprehensive reference for mineralogy of the lower mantle
Authors: Tange Yoshinori , Kuwayama Yasuhiro , Irifune Tetsuo , Funakoshi Ken‐ichi , Ohishi Yasuo
Published: April 2012

In situ P‐V‐T measurements of MgSiO3 perovskite were carried out up to 110 GPa and 2500 K, using a sintered‐diamond multianvil apparatus and a laser‐heated diamond anvil cell together with synchrotron radiation. The P‐V‐T data sets obtained by multianvil experiments (28–63 GPa and 300–1500 K) and diamond anvil cell experiments (52–108 GPa and 300, 1500–2430 K) are consistent with each other. The equation of state of MgSiO3 perovskite was subsequently represented by a Mie‐Grüneisen‐Debye model, using the equation of state of MgO as reference for pressure determination. In this study, we provide mutually consistent and precise P‐V‐T equations of state of MgSiO3 perovskite and MgO applicable to the bottom of the Earth's lower mantle. These P‐V‐T equations of state and derivative thermodynamic and elastic properties are essential for mineralogy of the lower mantle as a comprehensive reference.
The role of turbulence stress divergence in decelerating a river plume
Authors: Kilcher Levi F. , Nash Jonathan D. , Moum James N.
Published: April 2012

Turbulence controls the composition of river plumes through mixing and alters the plume's trajectory by diffusing its momentum. While believed to play a crucial role in decelerating river‐source waters, the turbulence stress in a near‐field river plume has not previously been observationally quantified. In this study, finely resolved density, velocity, and turbulence observations are combined with a control‐volume technique to describe the momentum balance in the Columbia River's near‐field plume during 10 tidal cycles that encompass both large and small river flow. Turbulence stress varies by 2–3 orders of magnitude, both within a given ebb and between ebbs with different tidal or river forcing; its magnitude scales with the strength of the instantaneous ebb outflow, i.e., high stresses occur during peak flow of strong ebbs. During these periods, the momentum equation is represented by a balance between stress divergence and plume deceleration. As the flow relaxes, the stress divergence weakens and other terms (pressure gradient and Coriolis) may become appreciable and influence plume deceleration. While the momentum balance could not be closed during these weaker flow periods, during strong tidal pulses the time scale for decay based on observed stress is significantly less than a tidal half‐period, indicating that stress divergence plays a fundamental role in the initial deceleration of the plume.
Interpreting LISST‐100X measurements of particles with complex shape using digital in‐line holography
Authors: Graham G. W. , Davies E. J. , Nimmo‐Smith W. A. M. , Bowers D. G. , Braithwaite K. M.
Published: April 2012

Measurements of suspended sediment volume concentrations, particle size and number density are routinely collected in marine and fresh‐water environments with LISST‐100X instruments to understand sediment transport, biological processes and fundamental opto‐acoustic problems. A LISST‐100X was simultaneously deployed with a novel holographic camera (holocam) in UK coastal waters to assess the performance of the laser diffraction technique when measuring natural suspensions. Volume distributions from the LISST‐100X, truncated to exclude non‐overlapping size bins with the holocam, exhibit an increase in small particles and median particle size is elevated in comparison to the holocam by 20–40%. We observe positive offsets between LISST‐100X and holocam number distributions of up to 2 orders of magnitude for particle sizes between 58–218μm, with discrepancies rising to 4 orders of magnitude for finer and coarser sizes. To explain these differences, a novel multiscale representation of particle size is used. The method quantifies individual dimensions that make up any two‐dimensional geometrical structure, it can be used as a metric for particle complexity, and offers a plausible explanation for an apparent increase in small particles (<58μm) reported by the LISST‐100X. The results suggest that for non‐spherical natural suspensions the LISST‐100X may be sensitive to optical scattering from sub‐scales within larger particles, reporting them as individual particles regardless of the way in which they may be packaged into particles of larger overall size. We urge caution in over interpretation of LISST size distributions obtained in natural suspensions without verification with independent particle imaging.
Climatology 2011: An MLS and sonde derived ozone climatology for satellite retrieval algorithms
Authors: McPeters Richard D. , Labow Gordon J.
Published: April 2012

The ozone climatology used as the a priori for the version 8 Solar Backscatter Ultraviolet (SBUV) retrieval algorithms has been updated. The climatology was formed by combining data from Aura MLS (2004–2010) with data from balloon sondes (1988–2010). The Microwave Limb Sounder (MLS) instrument on Aura has excellent latitude coverage and measures ozone daily from the upper troposphere to the lower mesosphere. The new climatology consists of monthly average ozone profiles for ten degree latitude zones covering pressure altitudes from 0 to 65 km. Ozone below 8 km (below 12 km at high latitudes) is based on balloons sondes, while ozone above 16 km (21 km at high latitudes) is based on MLS measurements. Sonde and MLS data are blended in the transition region. Ozone accuracy in the upper troposphere is greatly improved because of the near uniform coverage by Aura MLS, while the addition of a large number of balloon sonde measurements improves the accuracy in the lower troposphere, in the tropics and southern hemisphere in particular. The addition of MLS data also improves the accuracy of the climatology in the upper stratosphere and lower mesosphere. The revised climatology has been used for the latest reprocessing of SBUV and TOMS satellite ozone data.
A paleomagnetic study of Permian and Triassic rocks from the Toulon‐Cuers Basin, SE France: Evidence for intra‐Pangea block rotations in the Permian
Authors: Aubele K. , Bachtadse V. , Muttoni G. , Ronchi A. , Durand M.
Published: April 2012

The identification of a massive shear zone separating Gondwana from Laurasia during late Palaeozoic times is one of the prerequisites for the controversial Pangea B to A transition. Here we present new paleomagnetic data from Permian and Triassic sediments and volcanic rocks from the Toulon‐Cuers basin, SE France, likely to be situated within this intra‐Pangea shear zone. A total of 150 samples from 14 sites were collected in the field; 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690°C. After removal of an initial viscous magnetic component from room temperature up to 200°C, a second component of reverse polarity, oriented to the south‐and‐up, was identified in almost all samples of Permian age. The Triassic samples behave similarly, with the notable difference that here, two polarities of magnetization are present. Positive field tests suggest the primary character of this characteristic magnetization. The latitudes of the resulting Early to Mid Permian paleopoles agree well with the corresponding segment of the apparent polar wander path (APWP) for Europe, whereas the longitudes are strung out along a small circle segment, indicating relative rotations between the sampled regions and stable Europe. The Triassic poles, instead, plot close to the Triassic segment of the European APWP and provide an upper time limit for the observed rotations. These results suggest a wrench faulting event associated with intra‐Pangea crustal instability and transformation during the Permian.
Sea level rise and the ongoing Battle of Tarawa
Authors: Donner Simon
Published: April 2012

At dawn on 20 November 1943, U.S. marines launched an assault on Tarawa, a Japanese‐held atoll in the British Protectorate of the Gilbert and Ellice Islands. The water in the lagoon was only 3 feet deep that morning, less than the 4–5 feet required by a fully loaded personnel carrier to navigate the waters. As a result, marines saddled with equipment were forced to wade almost a mile across the lagoon under heavy Japanese fire. The United States won the Battle of Tarawa, but it proved to be one of the bloodiest battles of the war; almost 6000 Japanese, Americans, and Gilbertese were killed in just 3 days of fighting. Of the American fatalities, almost half occurred because U.S. military planners ignored warnings about the local tides on the morning of the assault [e.g., Wright, 2000].
Relating global precipitation to atmospheric fronts
Authors: Catto J. L. , Jakob C. , Berry G. , Nicholls N.
Published: April 2012

Atmospheric fronts are important for the day‐to‐day variability of weather in the midlatitudes, particularly during winter when extratropical storm‐tracks are at their maximum intensity. Fronts are often associated with heavy rain, and strongly affect the local space‐time distribution of rainfall. A recently developed objective front identification method that distinguishes between cold, warm and quasi‐stationary fronts, is applied to reanalysis data and combined with a daily global gridded data set to investigate how precipitation around the globe is associated with atmospheric fronts. A large proportion (up to 90%) of rainfall in the major storm‐track regions is associated with fronts, particularly cold and warm fronts. Precipitation over the oceanic storm‐tracks is mostly associated with cold fronts, while over the Northern Hemisphere continents precipitation is mainly associated with warm fronts. There are seasonal and regional variations in the proportion of precipitation associated with fronts.
Bending stress and dissipation in subducted lithosphere
Authors: Buffett B. A. , Becker T. W.
Published: April 2012

Oceanic lithosphere undergoes permanent deformation during subduction once the stresses exceed the elastic limit. Departures from elastic behavior occur by brittle failure in the shallow lithosphere and by a combination of low‐ and high‐temperature creep at greater depths. We combine laboratory‐based rheological models with estimates of slab shape from earthquake hypocenters to quantify the bending stress and dissipation in subduction zones. The peak stress occurs at the depth of the brittle‐ductile transition, which is controlled mainly by lithospheric age. Integrals of the stress over the thickness of the plate are used to evaluate the resistive bending force and the bending moment. A representative value for the resistive force on old oceanic lithosphere is 3 × 1012 N m−1, which is comparable in magnitude to ridge push but opposite in direction. Both the bending force and moment are remarkably insensitive to the rate of subduction. In fact, the bending moment can be approximated using a simple power law rheology and a stress exponent of n ≈ 14. Such a large exponent implies that the lithosphere behaves like a perfectly plastic solid. For most subduction zones the bending moment saturates along the entire plate. As a consequence, the bending stress does not influence the development of curvature during subduction. This behavior may explain why the curvature of subducted lithosphere is nearly independent of age.