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Abundance Analyses (abundance + analysis)
Selected AbstractsAbundance analysis of the cool extreme helium star LSS 3378MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Gajendra Pandey ABSTRACT Abundance analysis of the cool extreme helium (EHe) star LSS 3378 is presented. The abundance analysis is done using local thermodynamic equilibrium (LTE) line formation and LTE model atmospheres constructed for EHe stars. The atmosphere of LSS 3378 shows evidence of H-burning, He-burning, and s -process nucleosynthesis. The derived abundances of iron peak and ,-elements indicate the absence of selective fractionation or any other processes that can distort chemical composition of these elements. Hence, the Fe abundance [log ,(Fe) = 6.1] is adopted as an initial metallicity indicator. The measured abundances of LSS 3378 are compared with those of R Coronae Borealis (RCB) stars and with rest of the EHe stars as a group. [source] Carbon sequestration under Miscanthus: a study of 13C distribution in soil aggregatesGCB BIOENERGY, Issue 5 2009MARTA DONDINI Abstract The growing of bioenergy crops has been widely suggested as a key strategy in mitigating anthropogenic CO2 emissions. However, the full mitigation potential of these crops cannot be assessed without taking into account their effect on soil carbon (C) dynamics. Therefore, we analyzed the C dynamics through four soil depths under a 14-year-old Miscanthus plantation, established on former arable land. An adjacent arable field was used as a reference site. Combining soil organic matter (SOM) fractionation with 13C natural abundance analyses, we were able to trace the fate of Miscanthus -derived C in various physically protected soil fractions. Integrated through the whole soil profile, the total amount of soil organic carbon (SOC) was higher under Miscanthus than under arable crop, this difference was largely due to the input of new C. The C stock of the macroaggregates (M) under Miscanthus was significantly higher than those in the arable land. Additionally, the C content of the micro-within macroaggregates (mM) were higher in the Miscanthus soil as compared with the arable soil. Analysis of the intramicroaggregates particulate organic matter (POM) suggested that the increase C storage in mM under Miscanthus was caused by a decrease in disturbance of M. Thus, the difference in C content between the two land use systems is largely caused by soil C storage in physically protected SOM fractions. We conclude that when Miscanthus is planted on former arable land, the resulting increase in soil C storage contributes considerably to its CO2 mitigation potential. [source] Parent stars of extrasolar planets , VIII.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007Chemical abundances for 18 elements in 31 stars ABSTRACT We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets (SWPs). The resulting abundances are combined with other similar studies of nearby SWPs and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of SWPs in the SPOCS data base. We encourage continued study of the abundance patterns of SWPs to resolve these discrepancies. [source] Elemental abundance analyses with Coudé Echelle spectrograms from the TÜB,TAK National Observatory of Turkey: I. The HgMn stars 11 Per, HR 2801, and , Cnc,ASTRONOMISCHE NACHRICHTEN, Issue 8 2010S.J. Adelman Abstract Using coadded spectrograms taken with the Coudé Echelle Spectrograph (CES) of the 1.50-m Russian-Turkish Telescope of the TÜB,TAK National Observatory (TUG) near Antalya in Turkey, elemental abundance analyses of three HgMn stars 11 Per, HR 2801, and , Cnc were performed. Comparisons are made with spectra obtained with the long camera of the Dominion Astrophysical Observatory (DAO) coudé spectrograph and its SITe4 CCD. The CES equivalent widths are about 12% larger than that for the DAO long camera. Our first results from TUG data/spectra show that all three stars exhibit the Hg II ,3984 line and somewhat diverse abundance patterns. 11 Per tends to have underabundant light elements with underabundant and overabundant Fe-peak elements. HR 2801 has mostly underabundant elements, with a few elements having solar abundances while N and Mn are overabundant. The coolest star , Cnc has light elements having mostly solar abundances, overabundant iron group abundances, and very overabundant SrYZr and Ba. Comparisons with the abundance patterns of other HgMn stars show that they have a wide diversity of abundance patterns (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Elemental abundance analyses with DAO spectrograms: XXX.ASTRONOMISCHE NACHRICHTEN, Issue 4 20102 Ceti (B9 III), 21 Aquilae (B8 II-III), Aquilae (B5 III), Delphini (A2V), The middle B through early A stars Abstract This series of high quality elemental abundance analyses of mostly main-sequence band normal and peculiar B, A, and F stars defines their properties and provides data for the comparison with the analyses of somewhat similar stars and with theoretical predictions. Most use high dispersion and high S/N (, 200) spectrograms obtained with CCD detectors at the long camera of the Coudé spectrograph of the 1.22-m Dominion Astrophysical Observatory telescope. Here we reanalyze 21 Aql with better quality spectra and increase the number of stars consistently analyzed in the spectral range B5 to A2 by analyzing three new stars for this series. In the early A stars the normal and non-mCP stars have abundances with overlapping ranges. But more stars are needed especially in the B5 to B9 range. ,2 Cet on average has a solar composition with a few abundances outside the solar range while both 21 Aql and , Aql have abundances marginally less than solar. The abundances of , Del are greater than solar with a few elements such as Ca being less than solar. It is an Am star (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Prospects of stellar abundance studies from near-IR spectra observed with the E-ELTASTRONOMISCHE NACHRICHTEN, Issue 4 2010N. Ryde Abstract In 2006 ESO Council authorized a Phase B study of a European AO-telescope with a 42 m segmented primary with a 5-mirror design, the E-ELT. Several reports and working groups have already presented science cases for an E-ELT, specifically exploiting the new capabilities of such a large telescope. One of the aims of the design has been to find a balance in the performances between an E-ELT and the James Webb Space Telescope, JWST. Apart from the larger photon-collecting area, the strengths of the former is the higher attainable spatial and spectral resolutions. The E-ELT AO system will have an optimal performance in the near-IR, which makes it specially advantageous. High-resolution spectroscopy in the near-infrared has, however, not been discussed much. This paper aims at filling that gap, by specifically discussing spectroscopy of stellar (mainly red giant), photospheric abundances. Based on studies in the literature of stellar abundances, at the needed medium to high spectral resolutions in the near-infrared (0.8,2.4 ,m), I will try to extrapolate published results to the performance of the E-ELT and explore what could be done at the E-ELT in this field. A discussion on what instrument characteristics that would be needed for stellar abundance analyses in the near-IR will be given (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Complexity in small-scale dwarf spheroidal galaxies , Ludwig Biermann Award Lecture 2008ASTRONOMISCHE NACHRICHTEN, Issue 7 2009A. KochArticle first published online: 17 JUL 200 Abstract Our knowledge about the dynamics, the chemical abundances and the evolutionary histories of the more luminous dwarf spheroidal (dSph) galaxies is constantly growing. However, very little is known about the enrichment of the ultra-faint systems recently discovered in large numbers in large sky surveys. Current low-resolution spectroscopy and photometric data indicate that these galaxies are highly dark matter dominated and predominantly metal poor. On the other hand, recent high-resolution abundance analyses indicate that some dwarf galaxies experienced highly inhomogeneous chemical enrichment, where star formation proceeds locally on small scales. In this article, I will review the kinematic and chemical abundance information of the Milky Way satellite dSphs that is presently available from low- and high resolution spectroscopy. Moreover, some of the most peculiar element and inhomogeneous enrichment patterns will be discussed and related to the question of to what extent the faintest dSph candidates could have contributed to the Galactic halo, compared to more luminous systems (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Elemental abundance analyses with DAO spectrograms: XXXI.ASTRONOMISCHE NACHRICHTEN, Issue 1 200841 Cyg (F5 Ib-II), Her (F2 II), The early F supergiants Abstract This series of high quality elemental abundance analyses of mostly Main Sequence normal and peculiar B, A, and F stars defines their properties and provides data for the comparison with analyses of somewhat similar stars and with theoretical predictions. Most use high dispersion and high S/N (, 200) spectrograms obtained with CCD detectors at the long camera of the 1.22-m Dominion Astrophysical Observatory telescope's coudé spectrograph. Here we expand the range of stars examined to include two relatively quiescent F supergiants. , Her (F2 II) and 41 Cyg (F5 Ib-II) are analyzed as consistently as possible with previous studies. These LTE fine analyses use the ATLAS9 and the WIDTH9 programs of R. L. Kurucz. High signal-to-noise spectrograms and high quality atomic data were employed. The derived values of these photometrically constant stars are somewhat different with the abundances of , Her being somewhat metal-poor and those of 41 Cyg being crudely solar-like. Our analyses indicate that the basic results of Luck & Wepfer (1995) who also studied , Her and 41 Cyg are not likely to be significantly changed by new studies of all their stars. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fish assemblages as influenced by environmental factors in streams in protected areas of the Czech RepublicECOLOGY OF FRESHWATER FISH, Issue 1 2006M. Humpl Abstract,,, Three streams of comparable size located in different landscape-protected areas were selected for studying the effect of environmental factors on fish assemblages using indirect (detrended correspondence analysis, DCA) and direct (canonical correspondence analysis, CCA) gradient analysis. DCA of species showed well a gradient of assemblage changes in the longitudinal profile. DCA of sites stressed the variability between the fish assemblages of the three streams. This pattern was then confirmed by the highly significant between-stream CCA. In the within-site CCA, environmental factors explained 50.7% variability for presence,absence data and 58.3% for the relative abundance data. The analysis revealed that number of ponds and land use are the most influential factors of the strongest environmental gradient. However, in the partial CCAs, factor substratum type explained the largest proportion of the variability affecting fish in their habitat choice. Generally, presence,absence and relative abundance data of fish gave similar results in both DCA and CCA analyses; the same environmental factors proved to be important in both data type analyses. The environmental factors explain more variability than the regional (between-stream) one. The total proportion of variability explained by the presence,absence data analysis was 71.9% and in the relative abundance analysis even 80.8%. The environmental factors measured during the field survey explain 2.1- and 3.4-times more assemblages' variability than factors measured from a hydrological map. Resumen 1. Tres ríos de tamaño comparable localizados en diferentes áreas de paisaje protegido de la República Checa fueron seleccionados para estudiar el efecto de factores ambientales sobre los ensamblajes de peces. Para ello, utilizando análisis de gradientes indirectos (DCA) y directos (CCA). 2. El DCA para las especies enfatizó la variabilidad entre los ensamblajes de peces de los tres ríos. Este patrón fue confirmado por un CCA altamente significativo. Para la variabilidad dentro de la localidad, un CCA reveló que los factores ambientales explicaron un 50.7% para datos de presencia-ausencia y un 58.3% para las abundancias relativas. 3. Los análisis revelaron que el número de pozas y el uso del suelo fueron los factores de mayor influencia en el gradiente ambiental. Sin embargo, en el CCA parcial, el tipo de sustrato explicó la mayor proporción de la variabilidad que afecta a los peces en la elección de hábitat. 4. Generalmente los datos de presencia-ausencia y abundancia relativa produjeron resultados similares tanto en los análisis DCA como en los CCA; los mismos factores ambientales probaron ser importantes en los análisis de ambos tipos de datos. Los factores ambientales explicaron mas variabilidad que los regionales (entre ríos). La proporción total de variabilidad explicada por el análisis de los datos de presencia-ausencia fue 71.9% mientras que para las abundancias relativas fue de 80.8%. Los factores ambientales medidos durante los muestreos de campo explicaron 2.1 y 3.4 veces mas variabilidad que los factores medidos sobre mapas hidrológicos. [source] Identification and functional analysis of a human homologue of the monkey replication origin ors8JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006Mario Callejo Abstract We previously isolated from African green monkey (CV-1) cells a replication origin, ors8, that is active at the onset of S-phase. Here, its homologous sequence (hors8, accession number: DQ230978) was amplified from human cells, using the monkey-ors8-specific primers. Sequence alignment between the monkey and the human fragment revealed a 92% identity. Nascent DNA abundance analysis, involving quantification by real-time PCR, indicated that hors8 is an active replication origin, as the abundance of nascent DNA from a genomic region containing it was 97-fold higher relative to a non-origin region in the same locus. Furthermore, the data showed that the hors8 fragment is capable of supporting the episomal replication of its plasmid, when cloned into pBlueScript (pBS), as assayed by the DpnI resistance assay after transfection of HeLa cells. A quantitative chromatin immunoprecipitation (ChIP) assay, using antibodies against Ku, Orc2, and Cdc6, showed that these DNA replication initiator proteins were associated in vivo with the human ors8 (hors8). Finally, nascent DNA abundance experiments from human cells synchronized at different phases of the cell cycle revealed that hors8 is a late-firing origin of DNA replication, having the highest activity 8 h after release from late G1. J. Cell. Biochem. 99: 1606,1615, 2006. © 2006 Wiley-Liss, Inc. [source] Magnetic fields and chemical peculiarities of the very young intermediate-mass binary system HD 72106MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008C. P. Folsom ABSTRACT The recently discovered magnetic Herbig Ae and Be stars may provide qualitatively new information about the formation and evolution of magnetic Ap and Bp stars. We have performed a detailed investigation of one particularly interesting binary system with a Herbig Ae secondary and a late B-type primary possessing a strong, globally ordered magnetic field. 20 high-resolution Stokes V spectra of the system were obtained with the ESPaDOnS instrument mounted on the Canada,France,Hawaii Telescope. In these observations we see clear evidence for a magnetic field in the primary, but no evidence for a magnetic field in the secondary. A detailed abundance analysis was performed for both stars, revealing strong chemical peculiarities in the primary and normal chemical abundances in the secondary. The primary is strongly overabundant in Si, Cr and other iron-peak elements, as well as Nd, and underabundant in He. The primary therefore appears to be a very young Bp star. In this context, line profile variations of the primary suggest non-uniform lateral distributions of surface abundances. Interpreting the 0.639 95 ± 0.000 09 d variation period of the Stokes I and V profiles as the rotational period of the star, we have modelled the magnetic field geometry and the surface abundance distributions of Si, Ti, Cr and Fe using magnetic Doppler imaging. We derive a dipolar geometry of the surface magnetic field, with a polar strength Bd= 1230 G and an obliquity ,= 57°. The distributions Ti, Cr and Fe are all qualitatively similar, with an elongated patch of enhanced abundance situated near the positive magnetic pole. The Si distribution is somewhat different, and its relationship to the magnetic field geometry less clear. [source] An asteroseismic study of the , Cephei star , Ophiuchi: constraints on global stellar parameters and core overshootingMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007M. Briquet ABSTRACT We present a seismic study of the , Cephei star , Ophiuchi. Our analysis is based on the observation of one radial mode, one rotationally split ,= 1 triplet and three components of a rotationally split ,= 2 quintuplet for which the m values were well identified by spectroscopy. We identify the radial mode as fundamental, the triplet as p1 and the quintuplet as g1. Our non-local thermodynamic equilibrium abundance analysis results in a metallicity and CNO abundances in full agreement with the most recent updated solar values. With X,[0.71, 0.7211] and Z,[0.009, 0.015], and using the Asplund et al. mixture but with a Ne abundance about 0.3 dex larger, the matching of the three independent modes enables us to deduce constrained ranges for the mass (M= 8.2 ± 0.3 M,) and central hydrogen abundance (Xc= 0.38 ± 0.02) of , Oph and to prove the occurrence of core overshooting (,ov= 0.44 ± 0.07). We also derive an equatorial rotation velocity of 29 ± 7 km s,1. Moreover, we show that the observed non-equidistance of the ,= 1 triplet can be reproduced by the second-order effects of rotation. Finally, we show that the observed rotational splitting of two modes cannot rule out a rigid rotation model. [source] Elemental abundance survey of the Galactic thick discMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Bacham E. Reddy ABSTRACT We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample of 176 nearby (d, 150 pc) thick-disc candidate stars was chosen from the Hipparcos catalogue and subjected to a high-resolution spectroscopic analysis. Using accurate radial velocities combined with the Hipparcos astrometry, kinematics (U, V and W) and Galactic orbital parameters were computed. We estimate the probability for a star to belong to the thin disc, the thick disc or the halo. With a probability P, 70 per cent taken as certain membership, we assigned 95 stars to the thick disc, 13 to the thin disc, and 20 to the halo. The remaining 48 stars in the sample cannot be assigned with reasonable certainty to one of the three components. Abundances of C, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, Ce, Nd and Eu have been obtained. The abundances for the thick-disc stars are compared with those for the thin-disc members from Reddy et al. The ratios of ,-elements (O, Mg, Si, Ca and Ti) to iron for thick-disc stars show a clear enhancement compared to thin-disc members in the range ,0.3 < [Fe/H] < ,1.2. There are also other elements , Al, Sc, V, Co, and possibly Zn , which show enhanced ratios to iron in the thick disc relative to the thin disc. The abundances of Na, Cr, Mn, Ni and Cu (relative to Fe) are very similar for thin- and thick-disc stars. The dispersion in abundance ratios [X/Fe] at given [Fe/H] for thick-disc stars is consistent with the expected scatter due to measurement errors, suggesting a lack of ,cosmic' scatter. A few stars classified as members of the thick disc by our kinematic criteria show thin-disc abundances. These stars, which appear older than most thin-disc stars, are also, on average, younger than the thick-disc population. They may have originated early in the thin-disc history, and been subsequently scattered to hotter orbits by collisions. The thick disc may not include stars with [Fe/H] > ,0.3. The observed compositions of the thin and thick discs seem to be consistent with the models of galaxy formation by hierarchical clustering in a Lambda cold dark matter (,CDM) universe. [source] A comprehensive study of reported high-metallicity giant H ii regions , I. Detailed abundance analysisMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Marcelo Castellanos We present long-slit observations in the optical and near-infrared of 14 H ii regions in the spiral galaxies NGC 628, 925, 1232 and 1637, all of them reported to have solar or oversolar abundances according to empirical calibrations. For seven of the observed regions, ion-weighted temperatures from optical forbidden auroral to nebular line ratios are obtained and, for six of them, the oxygen abundances derived by standard methods turn out to be significantly lower than solar. The other one, named CDT1 in NGC 1232, shows an oxygen abundance of , and constitutes, to the best of our knowledge, the first high-metallicity H ii region for which accurate line temperatures, and hence elemental abundances, have been derived. For the rest of the regions no line temperature measurements could be made, and the metallicity has been determined by means of both detailed photoionization modelling and the sulphur abundance parameter S23. Only one of these regions shows values of O23 and S23 implying a solar or oversolar metallicity. According to our analysis, only two of the observed regions can therefore be considered as of high metallicity. These two fit the trends previously found in other high-metallicity H ii regions, i.e., N/O and S/O abundance ratios seem to be higher and lower than solar respectively. [source] HD 1: The number-one star in the sky,ASTRONOMISCHE NACHRICHTEN, Issue 4 2010K.G. Strassmeier Abstract We present the first ever study of the bright star HD 1. The star was chosen arbitrarily just because of its outstanding Henry Draper number. Surprisingly, almost nothing is known about this bright 7.m4 star. Our observations were performed as part of the commissioning of the robotic telescope facility STELLA and its fiber-fed high-resolution optical echelle spectrograph SES in the years 2007,2010. We found long-term radial velocity variations with a full amplitude of 9 km s,1 with an average velocity of ,29.8 km s,1 and suggest the star to be a hitherto unknown single-lined spectroscopic binary. A preliminary orbit with a period of 6.2 years (2279±69 days) and an eccentricity of 0.50±0.01 is given. Its rms uncertainty is just 73 m s,1. HD 1 appears to be a G9-K0 giant of luminosity class IIIa with Teff = 4850±100 K, logg = 2.0±0.2, L , 155 L,, a mass of 3.0±0.3 M,, a radius of 17.7 R,, and an age of ,350 Myr. A relative abundance analysis led to a metallicity of [Fe/H] = ,0.12 ± 0.09. The , -element silicon may indicate an overabundance of +0.13 though. The low strengths of some s-process lines and a lower limit for the 12C/13C isotope ratio of ,16 indicate that HD 1 is on the first ascend of the RGB. The absorption spectral lines appear rotationally broadened with a v sin i of 5.5±1.2 km s,1 but no chromospheric activity is evident. We also present photometric monitoring BV (RI)C data taken in parallel with STELLA. The star is likely a small-amplitude (<10 mmag) photometric variable although no periodicity was found (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||