4,211 research outputs found

    Classical Cepheids, what else?

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    We present new and independent estimates of the distances to the Magellanic Clouds (MCs) using near-infrared (NIR) and optical--NIR period--Wesenheit (PW) relations. The slopes of the PW relations are, within the dispersion, linear over the entire period range and independent of metal content. The absolute zero points were fixed using Galactic Cepheids with distances based on the infrared surface-brightness method. The true distance modulus we found for the Large Magellanic Cloud---(mM)0=18.48±0.01±0.10(m-M)_0 = 18.48 \pm 0.01 \pm 0.10 mag---and the Small Magellanic Cloud---(mM)0=18.94±0.01±0.10(m-M)_0 = 18.94 \pm 0.01 \pm 0.10 mag---agree quite well with similar distance determinations based on robust distance indicators. We also briefly discuss the evolutionary and pulsation properties of MC Cepheids

    Massive stellar systems: observational challenges and perspectives in the E-ELT era

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    We introduce the empirical framework concerning optical and near-infrared (NIR) photometry of crowded stellar fields. In particular, we address the impact that linear detectors and analytical PSF played in improving the accuracy and the precision of multi-band color-magnitude diagrams (CMDs). We focus our attention on recent findings based on deep NIR images collected with Adaptive Optics (AO) systems at the 8-10m class telescopes and discuss pros and cons of the different approaches. We also discuss the estimate of the absolute age of globular clusters using a well defined knee along the lower main sequence. We mention the role which the current AO-assisted instruments will have in addressing longstanding astrophysical problems of the Galactic center. Finally, we outline the role of first generation of E-ELT instruments upon photometry and spectroscopy of crowded stellar fields

    A New State Record Involving Nesolathrus (Coleoptera: Mycetophagidae)

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    The genus Nesolathrus (Mycetophagidae) is reported as a new record for the state of Hawaii, however, the species remains undetermined, as it differs from the unique species on which the genus is based. Big Island records include specimens reared from ohia twigs, Metrosideros polymorpha, from trees killed by Ceratocystis infections (Rapid Ohia Death)

    SDW and FISDW transition of (TMTSF)2_2ClO4_4 at high magnetic fields

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    The magnetic field dependence of the SDW transition in (TMTSF)2_2ClO4_4 for various anion cooling rates has been measured, with the field up to 27T parallel to the lowest conductivity direction cc^{\ast}. For quenched (TMTSF)2_2ClO4_4, the SDW transition temperature TSDWT_{\rm {SDW}} increases from 4.5K in zero field up to 8.4K at 27T. A quadratic behavior is observed below 18T, followed by a saturation behavior. These results are consistent with the prediction of the mean-field theory. From these behaviors, TSDWT_{\rm {SDW}} is estimated as TSDW0T_{\rm {SDW_0}}=13.5K for the perfect nesting case. This indicates that the SDW phase in quenched (TMTSF)2_2ClO4_4, where TSDWT_{\rm {SDW}} is less than 6K, is strongly suppressed by the two-dimensionality of the system. In the intermediate cooled state in which the SDW phase does not appear in zero field, the transition temperature for the field-induced SDW shows a quadratic behavior above 12T and there is no saturation behavior even at 27T, in contrast to the FISDW phase in the relaxed state. This behavior can probably be attributed to the difference of the dimerized gap due to anion ordering.Comment: 4pages,5figures(EPS), accepted for publication in PR
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