52 research outputs found

    Detailed Abundances for 28 Metal-poor Stars: Stellar Relics in the Milky Way

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    We present the results of an abundance analysis for a sample of stars with −4<-4<[Fe/H]<−2<-2. The data were obtained with the HIRES spectrograph at Keck Observatory. The set includes 28 stars, with effective temperature ranging from 4800 to 6600 K. For 13 stars with [Fe/H]<−2.6<-2.6, including nine with [Fe/H]<−3.0<-3.0 and one with [Fe/H]=−4.0=-4.0, these are the first reported detailed abundances. For the most metal-poor star in our sample, CS 30336-049, we measure an abundance pattern that is very similar to stars in the range [Fe/H]∼−3.5\sim-3.5, including a normal C+N abundance. We also find that it has very low but measurable Sr and Ba, indicating some neutron-capture activity even at this low of a metallicity. We explore this issue further by examining other very neutron-capture-deficient stars, and find that at the lowest levels, [Ba/Sr] exhibits the ratio of the main r-process. We also report on a new r-process-enhanced star, CS 31078-018. This star has [Fe/H]=−2.85=-2.85, [Eu/Fe]=1.23=1.23, and [Ba/Eu]=−0.51=-0.51. CS 31078-018 exhibits an ``actinide boost'', i.e. much higher [Th/Eu] than expected and at a similar level to CS 31082-001. Our spectra allow us to further constrain the abundance scatter at low metallicities, which we then use to fit to the zero-metallicity Type II supernova yields of Heger & Woosley (2008). We find that supernovae with progenitor masses between 10 and 20 M⊙_{\odot} provide the best matches to our abundances.Comment: 48 pages, 30 figures, 17 tables. Updated to ApJ version. Multiple typos and errors fixe

    Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster

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    Aims. We aim to provide observational constraints on diffusion models that predict peculiar chemical abundances in the atmospheres of Am stars. We also intend to check if chemical peculiarities and slow rotation can be explained by the presence of a weak magnetic field. Methods. We have obtained high resolution, high signal-to-noise ratio spectra of eight previously-classified Am stars, two normal A-type stars and one Blue Straggler, considered to be members of the Praesepe cluster. For all of these stars we have determined fundamental parameters and photospheric abundances for a large number of chemical elements, with a higher precision than was ever obtained before for this cluster. For seven of these stars we also obtained spectra in circular polarization and applied the LSD technique to constrain the longitudinal magnetic field. Results. No magnetic field was detected in any of the analysed stars. HD 73666, a Blue Straggler previously considered as an Ap (Si) star, turns out to have the abundances of a normal A-type star. Am classification is not confirmed for HD 72942. For HD 73709 we have also calculated synthetic Delta-a photometry that is in good agreement with the observations. There is a generally good agreement between abundance predictions of diffusion models and values that we have obtained for the remaining Am stars. However, the observed Na and S abundances deviate from the predictions by 0.6 dex and >0.25 dex respectively. Li appears to be overabundant in three stars of our sample.Comment: Accepted for publication on A&

    Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor and Sextans

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    We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H] <= -3 and three stars are below [Fe/H] -3.5. This constitutes the first evidence that the classical dSphs Fornax and Sextans join Sculptor in containing extremely metal-poor stars and suggests that all of the classical dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H]=-3.96 +- 0.10 is the most metal-poor star ever observed in an external galaxy. We carried out a detailed analysis of the chemical abundances of the alpha, iron peak, and the heavy elements, and we performed a comparison with the Milky Way halo and the ultra faint dwarf stellar populations. Carbon, barium and strontium show distinct features characterized by the early stages of galaxy formation and can constrain the origin of their nucleosynthesis.Comment: In A&A. This version corrects a few typographical errors in the coordinates of some of our stars (Table 1

    Meteorologisch-lufthygienische Untersuchungen im Raum Stuttgart-Weilimdorf Aug 1982 - Nov 1984

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    TIB: RN 9332 (8) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    Verkehrslaermkartierung Stuttgart

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    With 4 mapsTIB: RN 9332 (6) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    Ventilation requirements of farm animals during air transport Report no. 1; climatic conditions and ventilation systems used in aircraft

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    Translated from German (Tieraertzl. Umsch. 1978 v. 33(3) p. 160-166)Available from British Library Document Supply Centre- DSC:9021.6(AFRC-E-Trans--6)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

    Ventilation requirements of farm animals during air transport Maximum permitted loads according to the ventilation requirements of different types of animals

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    Translated from German (Tieraerzl. Umsch. 1978 v. 33(5) p. 247-252)Available from British Library Document Supply Centre- DSC:9021.6(AFRC-E-Trans--7)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

    Staubniederschlag in Stuttgart 1965-1982

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    SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
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