3,136 research outputs found

    A taxonomic note concerning a dicynodont (Synapsida: Anomodontia) from the Middle Triassic of East Africa

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    Main articleThe complicated histories of the Indian dicynodont Rechnisaurus and the East African dicynodont Kannemeyeria cristarhynchus has led to the incorrect use of the name ‘cristarhynchus’ for the latter taxon. This paper therefore proposes a new species name and diagnosis.The National Research Foundation and University Research Committee of the University of the Witwatersran

    Gaia-ESO Survey: Gas dynamics in the Carina nebula through optical emission lines

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    Aims. We present observations from the Gaia-ESO Survey in the lines of Hα, [N II], [S II], and He I of nebular emission in the central part of the Carina nebula. Methods. We investigate the properties of the two already known kinematic components (approaching and receding), which account for the bulk of emission. Moreover, we investigate the features of the much less known low-intensity high-velocity (absolute RV >50 km s) gas emission. Results. We show that gas giving rise to Hα and He I emission is dynamically well correlated with but not identical to gas seen through forbidden-line emission. Gas temperatures are derived from line-width ratios, and densities from [S II] doublet ratios. The spatial variation of N ionization is also studied, and found to differ between the approaching and receding components. The main result is that the bulk of the emission lines in the central part of Carina arise from several distinct shell-like expanding regions, the most evident found around η Car, the Trumpler 14 core, and the star WR25. These >shells> are non-spherical and show distortions probably caused by collisions with other shells or colder, higher-density gas. Some of them are also partially obscured by foreground dust lanes, while very little dust is found in their interior. Preferential directions, parallel to the dark dust lanes, are found in the shell geometries and physical properties, probably related to strong density gradients in the studied region. We also find evidence that the ionizing flux emerging from η Car and the surrounding Homunculus nebula varies with polar angle. The high-velocity components in the wings of Hα are found to arise from expanding dust reflecting the η Car spectrum. © ESO, 2016.This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541Peer Reviewe

    AE Aurigae: first detection of non-thermal X-ray emission from a bow shock produced by a runaway star

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    Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace by the encounter of two massive binary systems and now is passing through the dense nebula IC 405. The X-ray emission from the bow shock is detected at 30" to the northeast of the star, coinciding with an enhancement in the density of the nebula. From the analysis of the observed X-ray spectrum of the source and our theoretical emission model, we confirm that the X-ray emission is produced mainly by inverse Compton upscattering of infrared photons from dust in the shock front.Comment: Accepted for publication in the Astrophysical Journal with number ApJ, 757, L6. Four figure

    SOPHIE velocimetry of Kepler transit candidates VI. An additional companion in the KOI-13 system

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    We report the discovery of a new stellar companion in the KOI-13 system. KOI-13 is composed by two fast-rotating A-type stars of similar magnitude. One of these two stars hosts a transiting planet discovered by Kepler. We obtained new radial velocity measurements using the SOPHIE spectrograph at the Observatoire de Haute-Provence that revealed an additional companion in this system. This companion has a mass between 0.4 and 1 Msun and orbits one of the two main stars with a period of 65.831 \pm 0.029 days and an eccentricity of 0.52 \pm 0.02. The radial velocities of the two stars were derived using a model of two fast-rotating line profiles. From the residuals, we found a hint of the stellar variations seen in the Kepler light curve with an amplitude of about 1.41 km/s and a period close to the rotational period. This signal appears to be about three order of magnitude larger than expected for stellar activity. From the analysis of the residuals, we also put a 3-sigma upper-limit on the mass of the transiting planet KOI-13.01 of 14.8 Mjup and 9.4 Mjup, depending on which star hosts the transit. We found that this new companion has no significant impact on the photometric determination of the mass of KOI-13.01 but is expected to affect precise infrared photometry. Finally, using dynamical simulations, we infer that the new companion is orbiting around KOI-13B while the transiting planet candidate is expected to orbit KOI-13A. Thus, the transiting planet candidate KOI-13.01 is orbiting the main component of a hierarchical triple system.Comment: Accepted in A&A Letters. 4 pages including 4 figures and the RV tabl

    SOPHIE velocimetry of Kepler transit candidates XIV. A joint photometric, spectroscopic, and dynamical analysis of the Kepler-117 system

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    As part of our follow-up campaign of Kepler planets, we observed Kepler-117 with the SOPHIE spectrograph at the Observatoire de Haute-Provence. This F8-type star hosts two transiting planets in non-resonant orbits. The planets, Kepler-117 b and c, have orbital periods ≃18.8\simeq 18.8 and ≃50.8\simeq 50.8 days, and show transit-timing variations (TTVs) of several minutes. We performed a combined Markov chain Monte Carlo (MCMC) fit on transits, radial velocities, and stellar parameters to constrain the characteristics of the system. We included the fit of the TTVs in the MCMC by modeling them with dynamical simulations. In this way, consistent posterior distributions were drawn for the system parameters. According to our analysis, planets b and c have notably different masses (0.094±0.0330.094 \pm 0.033 and 1.84±0.181.84 \pm 0.18 MJ_{\rm J}) and low orbital eccentricities (0.0493±0.00620.0493 \pm 0.0062 and 0.0323±0.00330.0323 \pm 0.0033). The uncertainties on the derived parameters are strongly reduced if the fit of the TTVs is included in the combined MCMC. The TTVs allow measuring the mass of planet b, although its radial velocity amplitude is poorly constrained. Finally, we checked that the best solution is dynamically stable.Comment: 16 pages, of whom 5 of online material.12 figures, of whom 2 in the online material. 7 tables, of whom 4 in the online material. Published in A&

    Patterns of amenable child mortality over time in 34 member countries of the Organisation for Economic Co-operation and Development (OECD): Evidence from a 15-year time trend analysis (2001-2015)

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    Objectives To analyse the trends of amenable mortality rates (AMRs) in children over the period 2001-2015. Design Time trend analysis. Setting Thirty-four member countries of the Organisation for Economic Co-operation and Development (OECD). Participants Midyear estimates of the resident population aged 6414 years. Primary and secondary outcome measures Using data from the WHO Mortality Database and Nolte and McKee's list, AMRs were calculated as the annual number of deaths over the population/100 000 inhabitants. The rates were stratified by age groups (<1, 1-4, 5-9 and 10-14 years). All data were summarised by presenting the average rates for the years 2001/2005, 2006/2010 and 2011/2015. Results There was a significant decline in children's AMRs in the <1 year group in all 34 OECD countries from 2001/2005 to 2006/2010 (332.78 to 295.17/100 000; %\u394-11.30%; 95% CI -18.75% to -3.85%) and from 2006/2010 to 2011/2015 (295.17 to 240.22/100 000; %\u394-18.62%; 95% CI -26.53% to -10.70%) and a slow decline in the other age classes. The only cause of death that was significantly reduced was conditions originating in the early neonatal period for the <1 year group. The age-specific distribution of causes of death did not vary significantly over the study period. Conclusions The low decline in amenable mortality rates for children aged 651 year, the large variation in amenable mortality rates across countries and the insufficient success in reducing mortality from all causes suggest that the heath system should increase its efforts to enhance child survival. Promoting models of comanagement between primary care and subspecialty services, encouraging high-quality healthcare and knowledge, financing universal access to healthcare and adopting best practice guidelines might help reduce amenable child mortality

    SOPHIE velocimetry of Kepler transit candidates. XV. KOI-614b, KOI-206b, and KOI-680b: a massive warm Jupiter orbiting a G0 metallic dwarf and two highly inflated planets with a distant companion around evolved F-type stars

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    We report the validation and characterization of three new transiting exoplanets using SOPHIE radial velocities: KOI-614b, KOI-206b, and KOI-680b. KOI-614b has a mass of 2.86±0.35 MJup2.86\pm0.35~{\rm M_{Jup}} and a radius of 1.13−0.18+0.26 RJup1.13^{+0.26}_{-0.18}~{\rm R_{Jup}}, and it orbits a G0, metallic ([Fe/H]=0.35±0.150.35\pm0.15) dwarf in 12.9 days. Its mass and radius are familiar and compatible with standard planetary evolution models, so it is one of the few known transiting planets in this mass range to have an orbital period over ten days. With an equilibrium temperature of Teq=1000±45T_{eq}=1000 \pm 45 K, this places KOI-614b at the transition between what is usually referred to as "hot" and "warm" Jupiters. KOI-206b has a mass of 2.82±0.52 MJup2.82\pm 0.52~{\rm M_{Jup}} and a radius of 1.45±0.16 RJup1.45\pm0.16~{\rm R_{Jup}}, and it orbits a slightly evolved F7-type star in a 5.3-day orbit. It is a massive inflated hot Jupiter that is particularly challenging for planetary models because it requires unusually large amounts of additional dissipated energy in the planet. On the other hand, KOI-680b has a much lower mass of 0.84±0.15 MJup0.84\pm0.15~{\rm M_{Jup}} and requires less extra-dissipation to explain its uncommonly large radius of 1.99±0.18 RJup1.99\pm0.18~{\rm R_{Jup}}. It is one of the biggest transiting planets characterized so far, and it orbits a subgiant F9-star well on its way to the red giant stage, with an orbital period of 8.6 days. With host stars of masses of 1.46±0.17 M⊙1.46\pm0.17~M_{\odot} and 1.54±0.09 M⊙1.54 \pm 0.09~M_{\odot}, respectively, KOI-206b, and KOI-680b are interesting objects for theories of formation and survival of short-period planets around stars more massive than the Sun. For those two targets, we also find signs of a possible distant additional companion in the system
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