bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimated effects of white rice consumption and rice variety selection on incidence of type 2 diabetes in Cambodia
Authors: Sar Seila , Marks Geoffrey C 
Published: January 2015

AbstractObjectiveRice consumption patterns are considered an important risk factor for diabetes in many countries. The present study aimed to model the impact of a shift in consumption of white rice from current to appropriately reduced levels and a shift in rice variety from one with a high glycaemic index to one with a low glycaemic index, on the burden of type 2 diabetes in Cambodia.DesignPrevent Plus software was used to model the impact of selected changes to white rice consumption on the burden of type 2 diabetes. Data used for modelling included: demographic projections, relative risk estimates for white rice consumption and diabetes, diabetes incidence, rice type and quantities consumed. The 10-year projections were based on different scenarios of changes in risk factors.ResultsWith no intervention, 10-year projections showed that total new diabetes cases will increase from 11 315 (9·1 per 10 000 person-years) for the year 2011 to 14 852 new cases (12·4 per 10 000 person-years) in 2020. However, this increase will be reduced by 27 % (average across 10 years) with a change in rice variety from Phka Rumdual to IR66 and by 26 % (average across 10 years) with a 25 % reduction in quantity from current consumption levels.ConclusionsChanging rice consumption patterns has potential for an important impact on diabetes risk, with a change of rice variety having a similar impact on the burden of diabetes in communities consuming rice with a high glycaemic index as a 25 % reduction in the quantity of rice consumed. Similar effects are likely for other countries with rice as a staple food, diversity in rice varieties and high incidence of diabetes.
The Gaia-ESO Survey and Massive Stars
Authors: Blomme Ronny , Frémat Yves , Gosset Eric , Herrero Artemio , Lobel Alex , Apellániz Jesús Maíz , Morel Thierry , Negueruela Ignacio , Semaan Thierry , Simón-Díaz Sergio , Volpi Delia 
Published: January 2015

AbstractAs part of the Gaia-ESO Survey (GES), a number of clusters will be observed that were chosen specifically for their massive-star content. We report on the procedures we followed to determine the stellar parameters from the massive-star spectra of this survey. We intercompare the results from the different techniques used by the nodes of our group to determine these parameters and discuss some of the problems encountered. We present preliminary results for NGC 6705, NGC 3293, and Trumpler 14. We study microturbulence in A-type stars, we use the repeat observation to investigate binarity, and we determine cluster membership from the radial velocity information. The large number of massive-star spectra obtained by the Gaia-ESO Survey will allow us to critically test stellar evolution modelling.
Chemical abundances of fast-rotating OB stars
Authors: Cazorla Constantin , Morel Thierry , Nazé Yaël , Rauw Gregor 
Published: January 2015

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.
Massive star archeology in globular clusters
Authors: Chantereau W. , Charbonnel C. , Meynet G. 
Published: January 2015

AbstractGlobular clusters are among the oldest structures in the Universe and they host today low-mass stars and no gas. However, there has been a time when they formed as gaseous objects hosting a large number of short-lived, massive stars. Many details on this early epoch have been depicted recently through unprecedented dissection of low-mass globular cluster stars via spectroscopy and photometry. In particular, multiple populations have been identified, which bear the nucleosynthetic fingerprints of the massive hot stars disappeared a long time ago. Here we discuss how massive star archeology can be done through the lense of these multiple populations.
Massive OB stars at varying Z
Authors: Herrero A. , Garcia M. , Simón-Díaz S. , Camacho I. , Sabín-Sanjulián C. , Castro N. 
Published: January 2015

AbstractMassive stars play a key role in environments with very different metallicities. To interpret the role of massive stars in these systems we have to know their properties at different metallicities. The Local Group offers an excellent laboratory to this aim.
OHANA: Eta Carinae's Variability in the Near-IR
Authors: Mehner Andrea , de Wit Willem-Jan , Rivinius Thomas ,   the Paranal VLTI group
Published: January 2015

AbstractNear-IR photometry of η Car since 1972 revealed a long-term trend towards hotter temperatures and a cycloidal behavior of its near-IR colors around periastron passages. Both effects are likely triggered by the companion. We used VLTI AMBER observations from 2004–2014 to investigate η Car's variabilities in the near-IR.
The properties of single WO stars
Authors: Tramper F. , Straal S. M. , Gräfener G. , Kaper L. , de Koter A. , Langer N. , Sana H. , Vink J. S. 
Published: January 2015

AbstractThe enigmatic oxygen sequence Wolf-Rayet (WO) stars represent a very late stage in massive star evolution, although their exact nature is still under debate. The spectra of most of the WO stars have never been analysed through detailed modelling with a non-local thermodynamic equilibrium expanding atmosphere code. Here we present preliminary results of the first homogeneous analysis of the (apparently) single WOs.
Massive Star Asteroseismology in Action
Authors: Aerts Conny 
Published: January 2015

AbstractAfter highlighting the principle and power of asteroseismology for stellar physics, we briefly emphasize some recent progress in this research for various types of stars. We give an overview of high-precision high duty-cycle space photometry of OB-type stars. Further, we update the overview of seismic estimates of stellar parameters of OB dwarfs, with specific emphasis on convective core overshoot. We discuss connections between pulsational, rotational, and magnetic variability of massive stars and end with future prospects for asteroseismology of evolved OB stars.
Asteroseismology of red giants to constrain angular momentum transport
Authors: Eggenberger P. 
Published: January 2015

AbstractAsteroseismic data obtained by theKeplerspacecraft have led to the recent detection and characterization of rotational frequency splittings of mixed modes in red-giant stars. This has opened the way to the determination of the core rotation rates for these stars, which is of prime importance to progress in our understanding of internal angular momentum transport. In this contribution, we discuss which constraints can be brought by these asteroseismic measurements on the modelling of angular momentum transport in stellar radiative zones.
Asteroseismic Diagnostics for Semi-Convection in B Stars in the Era of K2
Authors: Moravveji Ehsan 
Published: January 2015

AbstractSemi-convection is a slow mixing process in chemically-inhomogeneous radiative interiors of stars. In massive OB stars, it is important during the main sequence. However, the efficiency of this mixing mechanism is not properly gauged yet. Here, we argue that asteroseismology of β Cep pulsators is capable of distinguishing between models of varying semi-convection efficiencies. We address this in the light of upcoming high-precision space photometry to be obtained with theKeplertwo-wheel mission for massive stars along the ecliptic.
Are the stars of a new class of variability detected in NGC 3766 fast rotating SPB stars?
Authors: Salmon S. J. A. J. , Montalbán J. , Reese D. R. , Dupret M.-A. , Eggenberger P. 
Published: January 2015

AbstractA recent photometric survey in the NGC 3766 cluster led to the detection of stars presenting an unexpected variability. They lie in a region of the Hertzsprung-Russell (HR) diagram where no pulsation are theoretically expected, in between the δ Scuti and slowly pulsating B (SPB) star instability domains. Their variability periods, between ~0.1–0.7 d, are outside the expected domains of these well-known pulsators. The NCG 3766 cluster is known to host fast rotating stars. Rotation can significantly affect the pulsation properties of stars and alter their apparent luminosity through gravity darkening. Therefore we inspect if the new variable stars could correspond to fast rotating SPB stars. We carry out instability and visibility analysis of SPB pulsation modes within the frame of the traditional approximation. The effects of gravity darkening on typical SPB models are next studied. We find that at the red border of the SPB instability strip, prograde sectoral (PS) modes are preferentially excited, with periods shifted in the 0.2–0.5 d range due to the Coriolis effect. These modes are best seen when the star is seen equator-on. For such inclinations, low-mass SPB models can appear fainter due to gravity darkening and as if they were located between the δ Scuti and SPB instability strips.
Tidal interactions in rotating multiple stars and their impact on their evolution
Authors: Auclair-Desrotour P. , Mathis S. , Le Poncin-Lafitte C. 
Published: January 2015

AbstractTidal dissipation in stars is one of the key physical mechanisms that drive the evolution of binary and multiple stars. As in the Earth oceans, it corresponds to the resonant excitation of their eigenmodes of oscillation and their damping. Therefore, it strongly depends on the internal structure, rotation, and dissipative mechanisms in each component. In this work, we present a local analytical modeling of tidal gravito-inertial waves excited in stellar convective and radiative regions respectively. This model allows us to understand in details the properties of the resonant tidal dissipation as a function of the excitation frequencies, the rotation, the stratification, and the viscous and thermal properties of the studied fluid regions. Then, the frequencies, height, width at half-height, and number of resonances as well as the non-resonant equilibrium tide are derived analytically in asymptotic regimes that are relevant in stellar interiors. Finally, we demonstrate how viscous dissipation of tidal waves leads to a strongly erratic orbital evolution in the case of a coplanar binary system. We characterize such a non-regular dynamics as a function of the height and width of resonances, which have been previously characterized thanks to our local fluid model.
Constraints on stellar evolution from white dwarf asteroseismology
Authors: Bischoff-Kim Agnès 
Published: January 2015

AbstractHigh mass and low mass stars follow a similar evolution until the inert core phase that follows the end of the core helium burning stage. In particular, one common phase of stellar evolution is the alpha capture reaction that turns carbon into oxygen in the core. We can obtain constraints on this reaction rate by studying the remnants of low mass stars, as this is the ultimate reaction that occurs in their core. We also present results that allow us to test the time dependent calculations of diffusion in dense interiors.
Radiative Levitation in Massive Stars: A self-consistent approach
Authors: D'souza Durand , Weiss Achim 
Published: January 2015

AbstractIn B stars, the transportation of metals such as iron due to radiative levitation is thought to trigger sub-surface convection, which may lead to significant stellar pulsations through the iron-induced kappa mechanism (Pamyatnykh et al. 2004). The main goal of this work is to model the evolution of these stars by treating radiative levitation in an accurate and efficient manner in order to enable rapid asteroseismic analysis using the Opacity Project data and codes (Seaton 2005) with the GARching STellar Evolution Code (Weiss & Schlattl 2008).
Time Resolved Photometric and Spectroscopic Analysis of Chemically Peculiar Stars
Authors: Joshi Santosh , Joshi Gireesh C. , Joshi Y. C. , Aggrawal Rahul 
Published: January 2015

AbstractHere we present the report on the “Nainital–Cape survey” research project aiming to search for and study the pulsational variability of main-sequence chemically peculiar (CP) stars. For this study, the time-series photometric observations of the sample stars were carried out at the 1.04 m ARIES telescope (India), while the high-resolution spectroscopic and spectro-polarimetric observations were carried out at the the 6.0 m Russian telescope. Under this project, we have recently found clear evidence of photometric variability in the Am star HD 73045, which is likely to be pulsating in nature with a period of about 36 min, hence adding a new member to the family of the δ Scuti pulsating variables that have peculiar abundances.
Stochastic excitation of gravity waves in rapidly rotating massive stars
Authors: Mathis S. , Neiner C. 
Published: January 2015

AbstractStochastic gravity waves have been recently detected and characterised in stars thanks to space asteroseismology and they may play an important role in the evolution of stellar angular momentum. In this context, the observational study of the CoRoT hot Be star HD 51452 suggests a potentially strong impact of rotation on stochastic excitation of gravito-inertial waves in rapidly rotating stars. In this work, we present our results on the action of the Coriolis acceleration on stochastic wave excitation by turbulent convection. We study the change of efficiency of this mechanism as a function of the waves' Rossby number and we demonstrate that the excitation presents two different regimes for super-inertial and sub-inertial frequencies. Consequences for rapidly rotating early-type stars and the transport of angular momentum in their interiors are discussed.
Stability boundaries for massive stars in the sHR diagram
Authors: Saio Hideyuki , Georgy Cyril , Meynet Georges 
Published: January 2015

AbstractStability boundaries of radial pulsations in massive stars are compared with positions of variable and non-variable blue-supergiants in the spectroscopic HR (sHR) diagram (Langer & Kudritzki 2014), whose vertical axis is 4 log Teff - log g(= log L/M). Observational data indicate that variables tend to have higher L/M than non-variables in agreement with the theoretical prediction. However, many variable blue-supergiants are found to have values of L/M below the theoretical stability boundary; i.e., surface gravities seem to be too high by around 0.2-0.3 dex.
Spectral Effects of Pulsations in Blue Supergiants
Authors: Tomić S. , Kraus M. , Oksala M. E. 
Published: January 2015

AbstractWe have been spectroscopically monitoring a number of blue supergiants, focusing on several strategic photospheric and wind lines. Our aim is to detect line profile variability, and to determine its origin. Here, we present preliminary results for ρ Leo and ε Ori. We conduct an asteroseismic analysis of Hei λ6678. We find in each star multiple periods raging from hours to several days. In addition, we observe strong, night to night variability in Hα.
Is λ Cep a pulsating star?
Authors: Uuh-Sonda J.M. , Eenens P. , Rauw G. 
Published: January 2015

AbstractIt has been proposed that the variability seen in absorption lines of the O6Ief star λ Cep is periodical and due to non-radial pulsations (NRP). We have obtained new spectra during six campaigns lasting between five and nine nights. In some datasets we find recurrent spectral variations which move redward in the absorption line profile, consistent with perturbations on the stellar surface of a rotating star. However the periods found are not stable between datasets, at odds with the NRP hypothesis. Moreover, even when no redward trend is found in a full dataset of an observing campaign, it can be present in a subset, suggesting that the phenomenon is short-lived, of the order of a few days, and possibly linked to transient magnetic loops.
An interferometric journey around massive stars
Authors: Meilland Anthony , Stee Philippe 
Published: January 2015

AbstractSince the construction in the late nineties of modern facilities such as the VLTI or CHARA, interferometry became a key technique to probe massive stars and their often-complex circumstellar environments. Over the last decade, the development of a new generation of beam combiners for these facilities enabled major breakthroughs in the understanding of the formation and evolution of massive stars. In this short review, we will present few of these advances concerning young stellar objects, binarity, mass loss, and stellar surfaces.
The photosphere and circumstellar environment of the Be star Achernar
Authors: Faes Daniel M. , de Souza Armando Domiciano , Carciofi Alex C. , Bendjoya Philippe 
Published: January 2015

AbstractAchernar is a key target to investigate high stellar rotation and the Be phenonemon. It is also the hottest star for which detailed photospheric information is available. Here we report our results to determine the photospheric parameters of Achernar and evaluate how the emission of a Viscous Decretion Disk (VDD) around it would be observable. The analysis is based on interferometric data (PIONIER and AMBER at ESO-VLTI), complemented by spectroscopy and polarimetry for the circumstellar emission. For the first time fundamental parameters of a Be photosphere were determined. The presence of a residual disk at the quiescent phase and some characteristics of the new formed disk (2013 activity) are also discussed. This is rare opportunity to precisely determine the stellar brightness distribution and evaluate the evolution of a just formed Be disk.
Evidences for a large hot spot on the disk of Betelgeuse (α Ori)
Authors: Montargès M. , Kervella P. , Perrin G. , Chiavassa A. , Le Bouquin J. B. 
Published: January 2015

AbstractMassive evolved stars contribute to the chemical enrichment of the Galaxy. When they die as supernova but also through their mass loss during the several thousands of years of their red supergiant (RSG) phase. Unfortunately the mass loss mechanism remains poorly understood. Detailed study of the CSE and photosphere of nearby RSGs is required to constrain this scenario.Betelgeuse is the closest RSG (197 pc) and therefore has a large apparent diameter (~ 42 mas) which makes it a very interesting target. For several years, our team has lead a multi-wavelength and multi-scale observing program to characterize its mass loss. We will review here our recent results in near-infrared interferometry.
Angular Diameters of O- and B-type Stars
Authors: Gordon Kathryn , Gies Douglas , Schaefer Gail 
Published: January 2015

AbstractWe are observing a sample of 10 O-type stars and 60 B-type stars to determine angular diameters using the Center for High Angular Resolution Astronomy (CHARA) Array, the foremost optical long baseline interferometer in the world. Our goal is to establish accurate stellar parameters to test modern theories of stellar evolution that include rotation. We will combine our stellar angular diameter measurements with flux and line measurements from spectroscopy, projected rotational velocities, and distances to determine radius, effective temperature, luminosity, equatorial rotational velocity, and evolutionary mass. Knowing these properties will allow us to place the stars in a Hertzsprung-Russell diagram and obtain estimates for the age and evolutionary state.
Binarity of the LBV HR Car
Authors: Rivinius Th. , Boffin H. M. J. , de Wit W. J. , Mehner A. , Martayan Ch. , Guieu S. , Le Bouquin J.-B. 
Published: January 2015

AbstractVLTI/AMBER and VLTI/PIONIER observations of the LBV HR Car show an interferometric signature that could not possibly be explained by an extended wind, more or less symmetrically distributed around a single object. Instead, observations both in the Brγ line and the H-band continuum are best explained by two point sources (or alternatively one point source and one slightly extended source) at about 2 mas separation and a contrast ratio of about 1:5. These observations establish that HR Car is a binary, but further interpretation will only be possible with future observations to constrain the orbit. Under the assumption that the current separation is close to the maximum one, the orbital period can be estimated to be of the order of 5 years, similar as in the η Car system. This would make HR Car the second such LBV binary.
AMBER/VLTI Snapshot Survey on Circumstellar Environments
Authors: Rivinius Th. , de Wit W.J. , Demers Z. , Quirrenbach A. ,   the VLTI Science Operations Team
Published: January 2015

AbstractOHANA is an interferometric snapshot survey of the gaseous circumstellar environments of hot stars, carried out by the VLTI group at the Paranal observatory. It aims to characterize the mass-loss dynamics (winds/disks) at unexplored spatial scales for many stars. The survey employs the unique combination of AMBER's high spectral resolution with the unmatched spatial resolution provided by the VLTI. Because of the spatially unresolved central OBA-type star, with roughly neutral colour terms, their gaseous environments are among the easiest objects to be observed with AMBER, yet the extent and kinematics of the line emission regions are of high astrophysical interest.
Basics of spectropolarimetry
Authors: Landstreet John D. 
Published: January 2015

AbstractMany astronomical sources of radiation emit polarised radiation, for example because of the presence of a disk which produces linear polarisation by scattering some photospheric radiation, or because of the presence of a magnetic field, which leads to circular and sometimes linear polarisation of spectral line profiles. Measuring the wavelength dependence of the polarisation of radiation from such sources can reveal valuable and interesting constraints on the nature of the objects observed. This paper summarises the basic ideas of spectropolarimetry and describes some of the information it can provide.
Magnetic Field - Stellar Winds Interaction
Authors: ud-Doula Asif 
Published: January 2015

AbstractAs per the recent study by the MiMeS collaboration, only about 10% of massive stars possess organized global magnetic fields, typically dipolar in nature. The competition between such magnetic fields and highly non-linear radiative forces that drive the stellar winds leads to a highly complex interaction. Such an interplay can lead to a number of observable phenomena, e.g. X-ray, wind confinement, rapid stellar spindown. However, due to its complexity, such an interaction cannot usually be modeled analytically, instead numerical modeling becomes a necessary tool. In this talk, I will discuss how numerical magnetohydrodynamic (MHD) simulations are employed to understand the nature of such magnetized massive star winds.
Beam me up, Spotty: Toward a new understanding of the physics of massive star photospheres
Authors: David-Uraz Alexandre , Wade Gregg , Owocki Stan 
Published: January 2015

AbstractFor 30 years, cyclical wind variability in OB stars has puzzled the astronomical community. Phenomenological models involving co-rotating bright spots provide a potential explanation for the observed variations, but the underlying physics remains unknown. We present recent results from hydrodynamical simulations constraining bright spot properties and compare them to what can be inferred from space-based photometry. We also explore the possibility that these spots are caused by magnetic fields and discuss the detectability of such fields.