202 research outputs found
Photometric Solutions for Detached Eclipsing Binaries: selection of ideal distance indicators in the SMC
Detached eclipsing binary stars provide a robust one-step distance
determination to nearby galaxies. As a by-product of Galactic microlensing
searches, catalogs of thousands of variable stars including eclipsing binaries
have been produced by the OGLE, MACHO and EROS collaborations. We present
photometric solutions for detached eclipsing binaries in the Small Magellanic
Cloud (SMC) discovered by the OGLE collaboration. The solutions were obtained
with an automated version of the Wilson-Devinney program. By fitting mock
catalogs of eclipsing binaries we find that the normalized stellar radii
(particularly their sum) and the surface brightness ratio are accurately
described by the fitted parameters and estimated standard errors, despite
various systematic uncertainties. In many cases these parameters are well
constrained. In addition we find that systems exhibiting complete eclipses can
be reliably identified where the fractional standard errors in the radii are
small. We present two quantitatively selected sub-samples of eclipsing binaries
that will be excellent distance indicators. These can be used both for
computation of the distance to the SMC and to probe its structure. One
particularly interesting binary has a very well determined solution, exhibits
complete eclipses, and is comprised of well detached G-type, class giants.Comment: 29 pages, 12 figures. To be published in Ap
The Optical Gravitational Lensing Experiment. Short Distance Scale to the LMC
We present {\it UBVI} photometry of the eclipsing binary HV2274 - the system
which has been recently used for distance determination to the LMC by Guinan et
al. (1998). We determine the interstellar reddening to the star,
E(B-V)=0.149+/-0.015 mag, based on observed colors of the star. This value is
in excellent agreement with the mean reddening towards HV2274 obtained from
photometry of the red clump stars in the surrounding field. The reddening is
almost twice as large as determined by Guinan et al. (1998).
We discuss the consequences of reddening underestimate. Most likely HV2274 is
located much closer with the distance modulus to the star and the LMC: m-M =
18.22+/-0.13 mag supporting the short distance scale to the LMC. Such a
distance modulus is in excellent agreement with the recent distance
determinations with RR Lyr and red clump stars.Comment: 11 pages, Latex, 2 Figures. Accepted for publication in Astrophysical
Journal Letters. New version - trimmed to fit ApJL. Additional determination
of the reddening towards HV2274 with OB star
Matter wave pulses characteristics
We study the properties of quantum single-particle wave pulses created by
sharp-edged or apodized shutters with single or periodic openings. In
particular, we examine the visibility of diffraction fringes depending on
evolution time and temperature; the purity of the state depending on the
opening-time window; the accuracy of a simplified description which uses
``source'' boundary conditions instead of solving an initial value problem; and
the effects of apodization on the energy width.Comment: 11 pages, 11 figure
Polarization dependence of four-wave mixing in a degenerate two-level system
Nearly degenerate four-wave mixing (NDFWM) within a closed degenerate
two-level atomic transition is theoretically and experimentally examined. Using
the model presented by A. Lezama et al [Phys. Rev. A 61, 013801 (2000)] the
NDFWM spectra corresponding to different pump and probe polarization cases are
calculated and discussed. The calculated spectra are compared to the
observation of NDFWM within the transition of
cesium in a phase conjugation experiment using magneto optically cooled atomsComment: 10 pages, 13 figures; submitted to Phys. Rev.
Opto-mechanical measurement of micro-trap via nonlinear cavity enhanced Raman scattering spectrum
High-gain resonant nonlinear Raman scattering on trapped cold atoms within a
high-fineness ring optical cavity is simply explained under a nonlinear
opto-mechanical mechanism, and a proposal using it to detect frequency of
micro-trap on atom chip is presented. The enhancement of scattering spectrum is
due to a coherent Raman conversion between two different cavity modes mediated
by collective vibrations of atoms through nonlinear opto-mechanical couplings.
The physical conditions of this technique are roughly estimated on Rubidium
atoms, and a simple quantum analysis as well as a multi-body semiclassical
simulation on this nonlinear Raman process is conducted.Comment: 7 pages, 2 figure
Assessment of the Central Effects of Natural Uranium via Behavioural Performances and the Cerebrospinal Fluid Metabolome
International audienceNatural uranium (NU), a component of the earth's crust, is not only a heavy metal but also an alpha particle emitter, with chemical and radiological toxicity. Populations may therefore be chronically exposed to NU through drinking water and food. Since the central nervous system is known to be sensitive to pollutants during its development, we assessed the effects on the behaviour and the cerebrospinal fluid (CSF) metabolome of rats exposed for 9 months from birth to NU via lactation and drinking water (1.5, 10, or 40 mgâ
L â1 for male rats and 40 mgâ
L â1 for female rats). Medium-term memory decreased in comparison to controls in male rats exposed to 1.5, 10, or 40 mgâ
L â1 NU. In male rats, spatial working memory and anxiety-and depressive-like behaviour were only altered by exposure to 40 mgâ
L â1 NU and any significant effect was observed on locomotor activity. In female rats exposed to NU, only locomotor activity was significantly increased in comparison with controls. LC-MS metabolomics of CSF discriminated the fingerprints of the male and/or female NU-exposed and control groups. This study suggests that exposure to environmental doses of NU from development to adulthood can have an impact on rat brain function
Integrated Water Resources Management in Cities in the World: Global Challenges
This is the final version. Available on open access from Springer via the DOI in this recordData Availability:
The authors declare that all the data supporting the findings of this study are included in its Supplementary Information.Water scarcity and accessibility remain persistently amongst the most prominent global challenges. Although there is a wide agreement among international organizations that Integrated Water Resources Management (IWRM) and water governance are key to overcome water-related challenges, global assessments of the progress made by cities is lacking. This paper for the first time analyses the challenges of water, wastewater, municipal solid waste and climate change in cities. We used empirical studies (125 cities) based on the City Blueprint Approach and developed a statistical estimation model to estimate IWRM performances of another 75 cities. These 200 cities in total represent more than 95% of the global urban population. This comprehensive global picture enables us to evaluate the existing gaps in achieving water-related Sustainable Development Goals (SDGs), in particular SDG 6 (clean water and sanitation) and SDG 11 (sustainable cities and communities). The best performing cities were Amsterdam and Singapore. Unfortunately, most cities do not yet manage their water resources wisely and are far from achieving the SDGs. For instance, targets regarding drinking water supply are still a challenge for many cities in Africa and Asia and challenges regarding sanitation are high in cities in Africa, Asia and Latin America. The same holds for solid waste management, climate adaptation, and people living in informal settlements. In another paper we will address the solution pathways to these global challenges
Post Main Sequence Orbital Circularization of Binary Stars in the Large and Small Magellanic Clouds
We present results from a study of the orbits of eclipsing binary stars (EBs)
in the Magellanic Clouds. The samples comprise 4510 EBs found in the Large
Magellanic Cloud (LMC) by the MACHO project, 2474 LMC EBs found by the OGLE-II
project (of which 1182 are also in the MACHO sample), 1380 in the Small
Magellanic Cloud (SMC) found by the MACHO project, and 1317 SMC EBs found by
the OGLE-II project (of which 677 are also in the MACHO sample); we also
consider the EROS sample of 79 EBs in the bar of the LMC. Statistics of the
phase differences between primary and secondary minima allow us to infer the
statistics of orbital eccentricities within these samples. We confirm the
well-known absence of eccentric orbit in close binary stars. We also find
evidence for rapid circularization in longer period systems when one member
evolves beyond the main sequence, as also found by previous studies.Comment: 37 pages, 16 figures, accepted for publication in ApJ. Added a new
reference and updated information on on line materia
Virtual Planetary Space Weather Service offered by the Europlant H2O2O Research Infrastructure
Under Horizon 2020, the Europlanet 2020 Research Infrastructure (EPN2020-RI) will include an entirely new Virtual Access Service, ?Planetary Space Weather Services? (PSWS) that will extend the concepts of space weather and space situational awareness to other planets in our Solar System and in particular to spacecraft that voyage through it. PSWS will make twelve new services accessible to the research community, space agencies, and industrial partners planning for space missions. These services will in particular be dedicated to the following key planetary environments: Mars (in support of the NASA MAVEN and European Space Agency (ESA) Mars Express and ExoMars missions), comets (building on the outstanding success of the ESA Rosetta mission), and outer planets (in preparation for the ESA JUpiter ICy moon Explorer mission), and one of these services will aim at predicting and detecting planetary events like meteor showers and impacts in the Solar System. This will give the European planetary science community new methods, interfaces, functionalities and/or plugins dedicated to planetary space weather as well as to space situational awareness in the tools and models available within the partner institutes. A variety of tools (in the form of web applications, standalone software, or numerical models in various degrees of implementation) are available for tracing propagation of planetary and/or solar events through the Solar System and modelling the response of the planetary environment (surfaces, atmospheres, ionospheres, and magnetospheres) to those events. But these tools were not originally designed for planetary event prediction and space weather applications. PSWS will provide the additional research and tailoring required to apply them for these purposes. PSWS will be to review, test, improve and adapt methods and tools available within the partner institutes in order to make prototype planetary event and space weather services operational in Europe at the end of 2017. To achieve its objectives PSWS will use a few tools and standards developed for the Astronomy Virtual Observatory (VO). This paper gives an overview of the project together with a few illustrations of prototype services based on VO standards and protocolsauthorsversionPeer reviewe
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