Sample records for s-process element abundances

  1. Stellar Abundance Observations and Heavy Element Formation

    NASA Astrophysics Data System (ADS)

    Cowan, J. J.

    2005-05-01

    Abundance observations indicate the presence of rapid-neutron capture (i.e., r-process) elements in old Galactic halo and globular cluster stars. These observations provide insight into the nature of the earliest generations of stars in the Galaxy -- the progenitors of the halo stars -- responsible for neutron-capture synthesis of the heavy elements. Abundance comparisons among the r-process-rich halo stars show that the heaviest neutron-capture elements (i.e., Ba and above) are consistent with a scaled solar system r-process abundance distribution, while the lighter neutron-capture elements do not conform to the solar pattern. These comparisons suggest the possibility of two r-process sites in stars. The large star-to-star scatter observed in the abundances of neutron-capture element/iron ratios at low metallicities -- which disappears with increasing metallicity or [Fe/H] -- suggests the formation of these heavy elements (presumably from certain types of supernovae) was rare in the early Galaxy. The stellar abundances also indicate a change from the r-process to the slow neutron capture (i.e., s-) process at higher metallicities in the Galaxy and provide insight into Galactic chemical evolution. Finally, the detection of thorium and uranium in halo and globular cluster stars offers an independent age-dating technique that can put lower limits on the age of the Galaxy, and hence the Universe. This work has been supported in part by NSF grant AST 03-07279 (J.J.C.) and by STScI grants GO-8111, GO-8342 and GO-9359.

  2. Abundances in the Very Metal Poor s-Process-rich Star CS 22183-015

    NASA Astrophysics Data System (ADS)

    Johnson, Jennifer A.; Bolte, Michael

    2002-11-01

    We report on the abundances for 13 elements in CS 22183-015, the most metal-poor, s-process-rich star yet discovered. We measure [Fe/H]=-3.12 and large overabundances compared to scaled solar values for 11 heavy elements with s-process origin. The low luminosity of the star suggests that it is a CH star, a giant that has accreted s-processed material from an evolved, very metal poor companion. We find a [Pb/Ba] value of 1.1 dex and, more generally, that the ratio of heavy to light s-process elements is larger than seen in the solar system. This result is consistent with theoretical expectations for the s-process in metal-poor stars. [Eu/La] is higher than predicted from the solar system s-process abundance ratios. We argue that the s-process in metal-poor stars is more efficient at producing Eu that in asymptotic giant branch stars of solar metallicity. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  3. COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r -PROCESS GALAXY RETICULUM II

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh

    We present chemical abundances derived from high-resolution Magellan /Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r -process material ([Eu/Fe] ∼ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture elementmore » abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r -process halo stars, but they are ∼0.5 dex lower than the solar r -process pattern. If the universal r -process pattern extends to those elements, the stars in Ret II display the least contaminated known r -process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r -process sites besides the source of r -process elements in Ret II. Galaxies like Ret II may be the original birth sites of r -process enhanced stars now found in the halo.« less

  4. Rare earth element abundances in presolar SiC

    NASA Astrophysics Data System (ADS)

    Ireland, T. R.; Ávila, J. N.; Lugaro, M.; Cristallo, S.; Holden, P.; Lanc, P.; Nittler, L.; Alexander, C. M. O'D.; Gyngard, F.; Amari, S.

    2018-01-01

    Individual isotope abundances of Ba, lanthanides of the rare earth element (REE) group, and Hf have been determined in bulk samples of fine-grained silicon carbide (SiC) from the Murchison CM2 chondrite. The analytical protocol involved secondary ion mass spectrometry with combined high mass resolution and energy filtering to exclude REE oxide isobars and Si-C-O clusters from the peaks of interest. Relative sensitivity factors were determined through analysis of NIST SRM reference glasses (610 and 612) as well as a trace-element enriched SiC ceramic. When normalised to chondrite abundances, the presolar SiC REE pattern shows significant deficits at Eu and Yb, which are the most volatile of the REE. The pattern is very similar to that observed for Group III refractory inclusions. The SiC abundances were also normalised to s-process model predictions for the envelope compositions of low-mass (1.5-3 M⊙) AGB stars with close-to-solar metallicities (Z = 0.014 and 0.02). The overall trace element abundances (excluding Eu and Yb) appear consistent with the predicted s-process patterns. The depletions of Eu and Yb suggest that these elements remained in the gas phase during the condensation of SiC. The lack of depletion in some other moderately refractory elements (like Ba), and the presence of volatile elements (e.g. Xe) indicates that these elements were incorporated into SiC by other mechanisms, most likely ion implantation.

  5. Accurate abundance determinations in S stars

    NASA Astrophysics Data System (ADS)

    Neyskens, P.; Van Eck, S.; Plez, B.; Goriely, S.; Siess, L.; Jorissen, A.

    2011-12-01

    S-type stars are thought to be the first objects, during their evolution on the asymptotic giant branch (AGB), to experience s-process nucleosynthesis and third dredge-ups, and therefore to exhibit s-process signatures in their atmospheres. Until present, the modeling of these processes is subject to large uncertainties. Precise abundance determinations in S stars are of extreme importance for constraining e.g., the depth and the formation of the 13C pocket. In this paper a large grid of MARCS model atmospheres for S stars is used to derive precise abundances of key s-process elements and iron. A first estimation of the atmospheric parameters is obtained using a set of well-chosen photometric and spectroscopic indices for selecting the best model atmosphere of each S star. Abundances are derived from spectral line synthesis, using the selected model atmosphere. Special interest is paid to technetium, an element without stable isotopes. Its detection in stars is considered as the best possible signature that the star effectively populates the thermally-pulsing AGB (TP-AGB) phase of evolution. The derived Tc/Zr abundances are compared, as a function of the derived [Zr/Fe] overabundances, with AGB stellar model predictions. The computed [Zr/Fe] overabundances are in good agreement with the AGB stellar evolution model predictions, while the Tc/Zr abundances are slightly over-predicted. This discrepancy can help to set stronger constraints on nucleosynthesis and mixing mechanisms in AGB stars.

  6. NEUTRON-CAPTURE ELEMENT ABUNDANCES IN MAGELLANIC CLOUD PLANETARY NEBULAE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mashburn, A. L.; Sterling, N. C.; Madonna, S.

    We present near-infrared spectra of 10 planetary nebulae (PNe) in the Large and Small Magellanic Clouds (LMC and SMC), acquired with the FIRE and GNIRS spectrometers on the 6.5 m Baade and 8.1 m Gemini South Telescopes, respectively. We detect Se and/or Kr emission lines in eight of these objects, the first detections of n -capture elements in Magellanic Cloud PNe. Our abundance analysis shows large s -process enrichments of Kr (0.6–1.3 dex) in the six PNe in which it was detected, and Se is enriched by 0.5–0.9 dex in five objects. We also estimate upper limits to Rb andmore » Cd abundances in these objects. Our abundance results for the LMC are consistent with the hypothesis that PNe with 2–3 M {sub ⊙} progenitors dominate the bright end of the PN luminosity function in young gas-rich galaxies. We find no significant correlations between s -process enrichments and other elemental abundances, central star temperature, or progenitor mass, though this is likely due to our small sample size. We determine S abundances from our spectra and find that [S/H] agrees with [Ar/H] to within 0.2 dex for most objects, but is lower than [O/H] by 0.2–0.4 dex in some PNe, possibly due to O enrichment via third dredge-up. Our results demonstrate that n -capture elements can be detected in PNe belonging to nearby galaxies with ground-based telescopes, allowing s -process enrichments to be studied in PN populations with well-determined distances.« less

  7. The AMBRE Project: r-process element abundances in the Milky Way thin and thick discs

    NASA Astrophysics Data System (ADS)

    Guiglion, Guillaume; de Laverny, Patrick; Recio-Blanco, Alejandra; Worley, C. Clare

    2018-04-01

    Chemical evolution of r-process elements in the Milky Way disc is still a matter of debate. We took advantage of high resolution HARPS spectra from the ESO archive in order to derive precise chemical abundances of 3 r-process elements Eu, Dy & Gd for a sample of 4 355 FGK Milky Way stars. The chemical analysis has been performed thanks to the automatic optimization pipeline GAUGUIN. Based on the [α/Fe] ratio, we chemically characterized the thin and the thick discs, and present here results of these 3 r-process element abundances in both discs. We found an unexpected Gadolinium and Dysprosium enrichment in the thick disc stars compared to Europium, while these three elements track well each other in the thin disc.

  8. Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements

    NASA Astrophysics Data System (ADS)

    Prantzos, N.; Abia, C.; Limongi, M.; Chieffi, A.; Cristallo, S.

    2018-05-01

    We present a comprehensive study of the abundance evolution of the elements from H to U in the Milky Way halo and local disc. We use a consistent chemical evolution model, metallicity-dependent isotopic yields from low and intermediate mass stars and yields from massive stars which include, for the first time, the combined effect of metallicity, mass loss, and rotation for a large grid of stellar masses and for all stages of stellar evolution. The yields of massive stars are weighted by a metallicity-dependent function of the rotational velocities, constrained by observations as to obtain a primary-like 14N behaviour at low metallicity and to avoid overproduction of s-elements at intermediate metallicities. We show that the Solar system isotopic composition can be reproduced to better than a factor of 2 for isotopes up to the Fe-peak, and at the 10 per cent level for most pure s-isotopes, both light ones (resulting from the weak s-process in rotating massive stars) and the heavy ones (resulting from the main s-process in low and intermediate mass stars). We conclude that the light element primary process (LEPP), invoked to explain the apparent abundance deficiency of the s-elements with A < 100, is not necessary. We also reproduce the evolution of the heavy to light s-elements abundance ratio ([hs/ls]) - recently observed in unevolved thin disc stars - as a result of the contribution of rotating massive stars at sub-solar metallicities. We find that those stars produce primary F and dominate its solar abundance and we confirm their role in the observed primary behaviour of N. In contrast, we show that their action is insufficient to explain the small observed values of ^{12}C/^{13}C in halo red giants, which is rather due to internal processes in those stars.

  9. Formation of Globular Clusters with Internal Abundance Spreads in r-Process Elements: Strong Evidence for Prolonged Star Formation

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji; Tsujimoto, Takuji

    2017-07-01

    Several globular clusters (GCs) in the Galaxy are observed to show internal abundance spreads in r-process elements (e.g., Eu). We propose a new scenario that explains the origin of these GCs (e.g., M5 and M15). In this scenario, stars with no/little abundance variations first form from a massive molecular cloud (MC). After all of the remaining gas of the MC is expelled by numerous supernovae, gas ejected from asymptotic giant branch stars can be accumulated in the central region of the GC to form a high-density intracluster medium (ICM). Merging of neutron stars then occurs to eject r-process elements, which can be efficiently trapped in and subsequently mixed with the ICM. New stars formed from the ICM can have r-process abundances that are quite different from those of earlier generations of stars within the GC. This scenario can explain both (I) why r-process elements can be trapped within GCs and (II) why GCs with internal abundance spreads in r-process elements do not show [Fe/H] spreads. Our model shows (I) that a large fraction of Eu-rich stars can be seen in Na-enhanced stellar populations of GCs, as observed in M15, and (II) why most of the Galactic GCs do not exhibit such internal abundance spreads. Our model demonstrates that the observed internal spreads of r-process elements in GCs provide strong evidence for prolonged star formation (˜108 yr).

  10. Formation of Globular Clusters with Internal Abundance Spreads in r -Process Elements: Strong Evidence for Prolonged Star Formation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bekki, Kenji; Tsujimoto, Takuji

    Several globular clusters (GCs) in the Galaxy are observed to show internal abundance spreads in r -process elements (e.g., Eu). We propose a new scenario that explains the origin of these GCs (e.g., M5 and M15). In this scenario, stars with no/little abundance variations first form from a massive molecular cloud (MC). After all of the remaining gas of the MC is expelled by numerous supernovae, gas ejected from asymptotic giant branch stars can be accumulated in the central region of the GC to form a high-density intracluster medium (ICM). Merging of neutron stars then occurs to eject r -processmore » elements, which can be efficiently trapped in and subsequently mixed with the ICM. New stars formed from the ICM can have r -process abundances that are quite different from those of earlier generations of stars within the GC. This scenario can explain both (i) why r -process elements can be trapped within GCs and (ii) why GCs with internal abundance spreads in r -process elements do not show [Fe/H] spreads. Our model shows (i) that a large fraction of Eu-rich stars can be seen in Na-enhanced stellar populations of GCs, as observed in M15, and (ii) why most of the Galactic GCs do not exhibit such internal abundance spreads. Our model demonstrates that the observed internal spreads of r -process elements in GCs provide strong evidence for prolonged star formation (∼10{sup 8} yr).« less

  11. The origin and evolution of r- and s-process elements in the Milky Way stellar disk

    NASA Astrophysics Data System (ADS)

    Battistini, Chiara; Bensby, Thomas

    2016-02-01

    Context. Elements heavier than iron are produced through neutron-capture processes in the different phases of stellar evolution. Asymptotic giant branch (AGB) stars are believed to be mainly responsible for elements that form through the slow neutron-capture process, while the elements created in the rapid neutron-capture process have production sites that are less understood. Knowledge of abundance ratios as functions of metallicity can lead to insight into the origin and evolution of our Galaxy and its stellar populations. Aims: We aim to trace the chemical evolution of the neutron-capture elements Sr, Zr, La, Ce, Nd, Sm, and Eu in the Milky Way stellar disk. This will allow us to constrain the formation sites of these elements, as well as to probe the evolution of the Galactic thin and thick disks. Methods: Using spectra of high resolution (42 000 ≲ R ≲ 65 000) and high signal-to-noise (S/N ≳ 200) obtained with the MIKE and the FEROS spectrographs, we determine Sr, Zr, La, Ce, Nd, Sm, and Eu abundances for a sample of 593 F and G dwarf stars in the solar neighborhood. The abundance analysis is based on spectral synthesis using one-dimensional, plane-parallel, local thermodynamic equilibrium (LTE) model stellar atmospheres calculated with the MARCS 2012 code. Results: We present abundance results for Sr (156 stars), Zr (311 stars), La (242 stars), Ce (365 stars), Nd (395 stars), Sm (280 stars), and Eu (378 stars). We find that Nd, Sm, and Eu show trends similar to what is observed for the α elements in the [X/Fe]-[Fe/H] abundance plane. For [Sr/Fe] and [Zr/Fe], we find decreasing abundance ratios for increasing metallicity, reaching sub-solar values at super-solar metallicities. [La/Fe] and [Ce/Fe] do not show any clear trend with metallicity, and they are close to solar values at all [Fe/H]. The trends of abundance ratios [X/Fe] as a function of stellar ages present different slopes before and after 8 Gyr. Conclusions: The rapid neutron-capture process is

  12. New functionalities in abundant element oxides: ubiquitous element strategy

    PubMed Central

    Hosono, Hideo; Hayashi, Katsuro; Kamiya, Toshio; Atou, Toshiyuki; Susaki, Tomofumi

    2011-01-01

    While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth's crust), many advanced materials are based on rare elements. A ‘rare-element crisis’ is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a ‘ubiquitous element strategy’ for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements. PMID:27877391

  13. Elemental abundance anomalies in the late Cenomanian extinction interval: a search for the source(s)

    USGS Publications Warehouse

    Orth, C.J.; Attrep, M.; Quintana, L.R.; Elder, W.P.; Kauffman, E.G.; Diner, R.; Villamil, T.

    1993-01-01

    Elemental abundances have been measured by neutron activation methods across the Cenomanian-Turonian (late Cretaceous) extinction interval in samples collected from sixteen sites in the Western Interior Basin of North America and from twelve widely separated locations around the globe, including six ODP/DSDP sites. In most Western Interior Basin sites, in Colombia, and in western Europe (weaker), two closely spaced elemental abundance peaks occur in the upper Cenomanian (??? 92 m.y.), spanning the ammonite zones of Sciponoceras gracile through Neocardioceras juddii. Elements with anomalously high concentrations include Sc, Ti, V, Cr, Mn, Co, Ni, Ir, Pt and Au. The lower peak coincides with the disappearance (extinction) of the foraminifer Rotalipora cushmani. In North American sections R. greenhornensis also disappears at or just below this horizon, but in Europe it disappears considerably earlier than R. cushmani. A series of molluscan extinction and speciation or migration events also begins near the stratigraphic level of the lower elemental abundance peak. The well-documented positive ?? 13C excursion begins just before the extinctions and the elemental anomalies, and continues into the lower Turonian, well above the upper anomaly. This carbon isotope excursion has been observed in East European sections where we find little or no evidence of the elemental anomalies, suggesting that the two phenomena may not be tightly coupled. Elemental abundance ratios in the anomalies closely resemble those of Mid-Atlantic Ridge basalt or Hawaiian lava (tholeiitic), but not those of C1 chondrite, black shale, average crustal rocks, or lamproite and kimberlite of roughly similar age in southeastern Kansas. The excess Ir and other siderophiles hint at possible large-body impact(s) for the source. However, we have not located microspherules (other than biogenic calcispheres) or shocked mineral grains in any of our samples. Furthermore, Sc, Ti, V and Mn are not enriched in

  14. Elemental abundances via X-ray observations of galaxy clusters and the InFOCmuS hard X-ray telescope

    NASA Astrophysics Data System (ADS)

    Baumgartner, Wayne H.

    2004-08-01

    The first part of this dissertation deals with the oxygen abundance of the Milky Way interstellar medium. Previous measurements had shown that oxygen in the ISM was depleted compared to its abundance in the sun. This dissertation presents new measurements of the ISM oxygen abundance taken in the X-ray band by observing the oxygen 0.6 keV photoionization K-edge in absorption towards 10 galaxy clusters. These measurements show that the ISM oxygen abundance is 0.9 solar, much greater than earlier depleted values. The oxygen abundance is found to be uniform across our 10 lines of sight, showing that it is not dependent on the depth of the hydrogen column. This implies that the galactic oxygen abundance does not depend on density, and that it is the same in dense clouds and in the more diffuse ISM. The next part of the dissertation measures elemental abundances in the galaxy clusters themselves. The abundances of the elements iron, silicon, sulfur, calcium, argon, and nickel are measured using the strong resonance K-shell emission lines in the X-ray band. Over 300 clusters from the ASCA archives are analyzed with a joint fitting procedure to improve the S/N ratio and provide the first average abundance results for clusters as a function of mass. The α elements silicon, sulfur, argon and calcium are not found to have similar abundances as expected from their supposed common origin. Also, no combination of SN Ia and SN II yields can account for the cluster abundance ratios, perhaps necessitating a contribution from a cosmologically early generation of massive population III stars. The last part of this dissertation details the development of the Cadmium Zinc Telluride (CZT) detectors on the InFOCμS hard X-ray telescope. InFOCμS is a balloon-borne imaging spectrometer that incorporates multi-layer coated grazing-incidence optics and CZT detectors. These detectors are well suited for hard X-ray astronomy because their large bandgap and high atomic number allow for

  15. Abundances of Ag and Cu in mantle peridotites and the implications for the behavior of chalcophile elements in the mantle

    NASA Astrophysics Data System (ADS)

    Wang, Zaicong; Becker, Harry

    2015-07-01

    Silver abundances in mantle peridotites and the behavior of Ag during high temperature mantle processes have received little attention and, as a consequence, the abundance of Ag in the bulk silicate Earth (BSE) has been poorly constrained. In order to better understand the processes that fractionate Ag and other chalcophile elements in the mantle, abundances of Ag and Cu in mantle peridotites from different geological settings (n = 68) have been obtained by isotope dilution ICP-MS methods. In peridotite tectonites and in a few suites of peridotite xenoliths which display evidence for variable extents of melt depletion and refertilization by silicate melts, Ag and Cu abundances show positive correlations with moderately incompatible elements such as S, Se, Te and Au. The mean Cu/Ag in fertile peridotites (3500 ± 1200, 1s, n = 38) is indistinguishable from the mean Cu/Ag of mid ocean ridge basalts (MORB, 3600 ± 400, 1s, n = 338) and MORB sulfide droplets. The constant mean Cu/Ag ratios indicate similar behavior of Ag and Cu during partial melting of the mantle, refertilization and magmatic fractionation, and thus should be representative of the Earth's upper mantle. The systematic fractionation of Cu, Ag, Au, S, Se and Te in peridotites and basalts is consistent with sulfide melt-silicate melt partitioning with apparent partition coefficients of platinum group elements (PGE) > Au ⩾ Te > Cu ≈ Ag > Se ⩾ S. Because of the effects of secondary processes, the abundances of chalcophile elements, notably S, Se, but also Cu and the PGE in many peridotite xenoliths are variable and lower than in peridotite massifs. Refertilization of peridotite may change abundances of chalcophile and lithophile elements in peridotite massifs, however, this seems to mostly occur in a systematic way. Correlations with lithophile and chalcophile elements and the overlapping mean Cu/Ag ratios of peridotites and ocean ridge basalts are used to constrain abundances of Ag and Cu in the BSE

  16. Diversity of abundance patterns of neutron-capture elements in very metal-poor stars

    NASA Astrophysics Data System (ADS)

    Aoki, Misa; Aoki, Wako; Ishimaru, Yuhri; Wanajo, Shinya

    2014-05-01

    Observations of Very Metal-Poor stars indicate that there are at least two sites to r-process; "weak r-process" and "main r-process". A question is whether these two are well separated or there exists a variation in the r-process. We present the results of abundance analysis of neutron-capture elements in the two Very Metal-Poor stars HD107752 and HD110184 in the Milky Way halo observed with the Subaru Telescope HDS. The abundance patterns show overabundace at light n-capture elements (e.g. Sr, Y), inferring the element yielding of weak r-process, while heavy neutron-capture elements (e.g. Ba, Eu) are deficient; however, the overabundance of light ones is not as significant as that previously found in stars representing the weak r-process (e.g. HD122563; Honda et al. 2006). Our study show diversity in the abundance patterns from light to heavy neutron-capture elements in VMP stars, suggesting a variation in r-process, which may depend on electron fraction of environment.

  17. Abundances and Depletions of Neutron-capture Elements in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Ritchey, A. M.; Federman, S. R.; Lambert, D. L.

    2018-06-01

    We present an extensive analysis of the gas-phase abundances and depletion behaviors of neutron-capture elements in the interstellar medium (ISM). Column densities (or upper limits to the column densities) of Ga II, Ge II, As II, Kr I, Cd II, Sn II, and Pb II are determined for a sample of 69 sight lines with high- and/or medium-resolution archival spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. An additional 59 sight lines with column density measurements reported in the literature are included in our analysis. Parameters that characterize the depletion trends of the elements are derived according to the methodology developed by Jenkins. (In an appendix, we present similar depletion results for the light element B.) The depletion patterns exhibited by Ga and Ge comport with expectations based on the depletion results obtained for many other elements. Arsenic exhibits much less depletion than expected, and its abundance in low-depletion sight lines may even be supersolar. We confirm a previous finding by Jenkins that the depletion of Kr increases as the overall depletion level increases from one sight line to another. Cadmium shows no such evidence of increasing depletion. We find a significant amount of scatter in the gas-phase abundances of Sn and Pb. For Sn, at least, the scatter may be evidence of real intrinsic abundance variations due to s-process enrichment combined with inefficient mixing in the ISM.

  18. The Abundances of the Fe Group Elements in AV 304, an Abundance Standard in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.; Lanz, Thierry; Bouret, Jean-Claude; Proffitt, Charles R.; Adelman, Saul J.; Hubeny, Ivan

    2018-06-01

    AV 304 is a B0.5 IV field star in the Small Magellanic Cloud with ultra-sharp spectral lines that has emerged as an abundance standard. We have combined recent spectroscopic observations from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope with archival data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and ESO’s VLT/UVES to determine the abundances of the Fe group elements (Ti, V, Cr, Mn, Fe, Co, & Ni). The analysis was carried through using the Hubeny/Lanz NLTE programs TLUSTY/SYNSPEC. The COS observations were secured with the G130M, G160M, G185M, and G225M gratings. Combined with the FUSE data, we have achieved spectral coverage in the UV from 950 to 2400 A. Measurable lines from the Fe group, except for a very few multiplets of Fe II, III are not observed in optical spectra. The following stellar parameters were found: Teff = 27500±500 K, log g = 3.7±0.1 cm/s2, Vturb= 1±1 km/s, and v sin i = 8 ±2 km/s. The Fe abundance appears to be only slightly lower than the mean depletion in the SMC, but the other Fe group elements are underabundant by 0.3 dex or more. This study confirmed the low abundance of nitrogen (-1.25 dex relative to the solar value) that was reported by Peters & Adelman (ASP Conf. Series, 348, p. 136, 2006). Whereas the light elements are delivered to the ISM by core-collapse supernovae (CCSNe), the Fe group elements are believed to come mostly from low/intermediate mass binaries containing white dwarfs that undergo SNe Ia explosions. A single SNe Ia can deliver 0.5 solar masses of pure Fe (and maybe Mn) to the ISM compared with about 0.07 solar masses from a CCSNe. It appears that there is very little processed material from its interior in the atmosphere of AV 304 and that the star did not form from an interstellar cloud that was enriched by material from earlier supernova activity. Support from STScI grants HST-GO-14081.002 and HST-GO-13346.022, and USC’s Women in Science and Engineering (WiSE) program is

  19. The abundances of the elements in sharp-lined early type stars

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.

    1992-01-01

    An International Ultraviolet Explorer (IUE) observing strategy that has yielded co-added spectra with enhanced S/N ratios for several A and B stars was established. New observations by Roby and Adelman using the same technique were added two new Hg-Mn stars into this sample. A long-term study of elemental abundances in this uniform, high-quality set of IUE spectra for 13 stars was begun. The first stages of this project are reported: abundances for N, Cr, Mn, Fe, Co, and Ni. The study of the Fe-peak elements show that our data set can provide accurate abundances and that abundances obtained from UV and optical spectra often are in good agreement. The groundwork for selfconsistent abundance analyses of more exotic elements in our long term project was provided.

  20. Neutron-capture element abundances in the planetary nebula NGC 5315 from deep optical and near-infrared spectrophotometry★†

    NASA Astrophysics Data System (ADS)

    Madonna, S.; García-Rojas, J.; Sterling, N. C.; Delgado-Inglada, G.; Mesa-Delgado, A.; Luridiana, V.; Roederer, I. U.; Mashburn, A. L.

    2017-10-01

    We analyse the chemical composition of the planetary nebula (PN) NGC 5315, through high-resolution (R ˜ 40000) optical spectroscopy with Ultraviolet-Visual Echelle Spectrograph at the Very Large Telescope, and medium-resolution (R ˜ 4800) near-infrared spectroscopy with Folded-port InfraRed Echellette at Magellan Baade Telescope, covering a wide spectral range from 0.31 to 2.50 μm. The main aim of this work is to investigate neutron (n)-capture element abundances to study the operation of the slow n-capture ('s-process') in the asymptotic giant branch (AGB) progenitor of NGC 5315. We detect more than 700 emission lines, including ions of the n-capture elements Se, Kr, Xe and possibly Br. We compute physical conditions from a large number of diagnostic line ratios, and derive ionic abundances for species with available atomic data. The total abundances are computed using recent ionization correction factors (ICFs) or by summing ionic abundances. Total abundances of common elements are in good agreement with previous work on this object. Based on our abundance analysis of NGC 5315, including the lack of s-process enrichment, we speculate that the most probable evolutionary scenario is that the progenitor star is in a binary system as hinted at by radial velocity studies, and interactions with its companion truncated the AGB before s-process enrichment could occur. However there are other two possible scenarios for its evolution, that cannot be ruled out: (I) the progenitor is a low-mass single star that did not undergo third dredge-up; (II) the progenitor star of NGC 5315 had an initial mass of 3-5 M⊙, and any s-process enhancements were heavily diluted by the massive envelope during the AGB phase.

  1. Trace-element abundances in several new ureilites

    NASA Technical Reports Server (NTRS)

    Boynton, William V.; Hill, Dolores H.

    1993-01-01

    Four new ureilites are analyzed for trace-element abundances. Frontier Mountain (FRO) 90054 is an augite-rich ureilite and has high rare earth element (REE) abundances with a pattern expected of augite. FRO 90036 and Acfer 277 have REE patterns similar to the V-shape pattern of other ureilites. Nuevo Mercurio (b) has very high REE abundances, but they look like they are due to terrestrial alteration. The siderophile-element pattern of these ureilites are similar to those of known ureilites.

  2. Sunspots, Starspots, and Elemental Abundances

    NASA Astrophysics Data System (ADS)

    Doschek, George A.; Warren, Harry P.

    2017-08-01

    The composition of plasma in solar and stellar atmospheres is not fixed, but varies from feature to feature. These variations are organized by the First Ionization Potential (FIP) of the element. Solar measurements often indicate that low FIP elements (< 10eV, such as Fe, Si, Mg) are enriched by factors of 3-4 in the corona relative to high FIP elements (>10 eV, such as C, N, O, Ar, He) compared to abundances in the photosphere. Stellar observations have also shown similar enrichments. An inverse FIP effect, where the low FIP elements are depleted, has been observed in stellar coronae of stars believed to have large starspots in their photospheres. The abundances are important for determining radiative loss rates in models, tracing the origin of the slow solar wind, and for understanding wave propagation in the chromosphere and corona. Recently, inverse FIP effects have been discovered in the Sun (Doschek, Warren, & Feldman 2015, ApJ, 808, L7) from spectra obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The inverse FIP regions seem always to be near sunspots and cover only a very small area (characteristic length = a few arcseconds). However, in pursuing the search for inverse FIP regions, we have found that in some sunspot groups the coronal abundance at a temperature of 3-4 MK can be near photospheric over much larger areas of the sun near the sunspots (e.g., 6,000 arcsec2). Also, sometimes the abundances at 3-4 MK are in between coronal and photospheric values. This can occur in small areas of an active region. It is predicted (Laming 2015, Sol. Phys., 12, 2) that the FIP effect should be highly variable in the corona. Several examples of coronal abundance variations are presented. Our work indicates that a comprehensive re-investigation of solar abundances is highly desirable. This work is supported by a NASA Hinode grant.

  3. Abundance Patterns in S-type AGB Stars: Setting Constraints on Nucleosynthesis and Stellar Evolution Models

    NASA Astrophysics Data System (ADS)

    Neyskens, P.; van Eck, S.; Plez, B.; Goriely, S.; Siess, L.; Jorissen, A.

    2011-09-01

    During evolution on the AGB, stars of type S are the first to experience s-process nucleosynthesis and the third dredge-up, and therefore to exhibit s-process signatures in their atmospheres. Their high mass-loss rates (10-7 to 10-6 M⊙/year) make them major contributors to the AGB nucleosynthesis yields at solar metallicity. Precise abundance determinations in S stars are of the utmost importance for constraining e.g. the third dredge-up luminosity and efficiency (which has been only crudely parameterized in current nucleosynthetic models so far). Here, dedicated S-star model atmospheres are used to determine precise abundances of key s-process elements, and to set constraints on nucleosynthesis and stellar evolution models. Special interest is paid to technetium, an element with no stable isotopes. Its detection is considered the best signature that the star effectively populates the thermally-pulsing AGB phase of evolution. The derived Tc/Zr abundances are compared, as a function of the derived [Zr/Fe] overabundances, with AGB stellar model predictions. The [Zr/Fe] overabundances are in good agreement with model predictions, while the Tc/Zr abundances are slightly overpredicted. This discrepancy can help to set better constraints on nucleosynthesis and stellar evolution models of AGB stars.

  4. Coronae of Stars with Supersolar Elemental Abundances

    NASA Technical Reports Server (NTRS)

    Peretz, Uria; Behar, Ehud; Drake, Stephen A.

    2015-01-01

    Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the first ionization potential (FIP). This study focuses on the coronal composition of stars with supersolar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, iota Hor, HR 7291, tau Boo, and alpha Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances we measured were obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra onboard the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and tau Boo no FIP effect is present, while iota Hor, HR 7291, and alpha Cen A and B show a clear FIP trend. These conclusions hold whether the comparison is made with solar abundances or the individual stellar abundances. Unlike the solar corona, where low-FIP elements are enriched, in these stars the FIP effect is consistently due to a depletion of high-FIP elements with respect to actual photospheric abundances. A comparison with solar (instead of stellar) abundances yields the same fractionation trend as on the Sun. In both cases, a similar FIP bias is inferred, but different fractionation mechanisms need to be invoked.

  5. Isotope-abundance variations of selected elements (IUPAC technical report)

    USGS Publications Warehouse

    Coplen, T.B.; Böhlke, J.K.; De Bievre, P.; Ding, T.; Holden, N.E.; Hopple, J.A.; Krouse, H.R.; Lamberty, A.; Peiser, H.S.; Revesz, K.; Rieder, S.E.; Rosman, K.J.R.; Roth, E.; Taylor, P.D.P.; Vocke, R.D.; Xiao, Y.K.

    2002-01-01

    Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

  6. THE ABUNDANCES OF LIGHT NEUTRON-CAPTURE ELEMENTS IN PLANETARY NEBULAE. III. THE IMPACT OF NEW ATOMIC DATA ON NEBULAR SELENIUM AND KRYPTON ABUNDANCE DETERMINATIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sterling, N. C.; Porter, R. L.; Dinerstein, Harriet L., E-mail: nsterlin@westga.edu, E-mail: ryanlporter@gmail.com, E-mail: harriet@astro.as.utexas.edu

    The detection of neutron(n)-capture elements in several planetary nebulae (PNe) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. However, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. Recently, photoionization (PI) and recombination data were determined for Se and Kr, the two most widely detected n-capture elements in nebular spectra. We have incorporated these new data into the photoionization code Cloudy. To test the atomic data, numerical models were computed for 15 PNe that exhibit emission lines from multiple Kr ions. We found systematic discrepancies between the predicted and observedmore » emission lines that are most likely caused by inaccurate PI and recombination data. These discrepancies were removed by adjusting the Kr{sup +}–Kr{sup 3+} PI cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. From grids of models spanning the physical conditions encountered in PNe, we derive new, broadly applicable ionization correction factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs were applied to our previous survey of near-infrared [Kr iii] and [Se iv] emission lines in 120 PNe. The revised Se and Kr abundances are 0.1–0.3 dex lower than former estimates, with average values of [Se/(O, Ar)] = 0.12 ± 0.27 and [Kr/(O, Ar)] = 0.82 ± 0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. We also find a tendency for high-velocity PNe that can be associated with the Galactic thick disk to exhibit larger s-process enrichments than low-velocity PNe belonging to the thin-disk population.« less

  7. s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

    NASA Astrophysics Data System (ADS)

    Palmerini, S.; Trippella, O.; Busso, M.; Vescovi, D.; Petrelli, M.; Zucchini, A.; Frondini, F.

    2018-01-01

    In the past years the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the so-called Asymptotic Giant Branch (or "AGB") could not be explained by self-consistent models, forcing researchers to extensive parameterizations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding the formation of 13C and then the activation of the 13C (α,n)16O reaction. Only recently, attempts to solve this problem started to consider quantitatively physically-based mixing mechanisms. Among them, MHD processes in the plasma were suggested to yield mass transport through magnetic buoyancy. In this framework, we compare results of nucleosynthesis models for Low Mass AGB Stars (M≲ 3M⊙), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the 13C reservoir. We find that n-captures driven by magnetically-induced mixing can indeed account for the SiC data quite well and that this is due to the fact that our 13C distribution fulfils the above constraints rather accurately. We suggest that similar tests should be now performed using different physical models for mixing. Such comparisons would indeed improve decisively our understanding of the formation of the neutron source.

  8. Space-based measurements of elemental abundances and their relation to solar abundances

    NASA Technical Reports Server (NTRS)

    Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.

    1990-01-01

    The Ion Composition Instrument (ICI) aboard the ISEE-3/ICE spacecraft was in the solar wind continuously from August 1978 to December 1982. The results made it possible to establish long-term average solar wind abundance values for helium, oxygen, neon, silicon, and iron. The Charge-Energy-Mass instrument aboard the CCE spacecraft of the AMPTE mission has measured the abundance of these elements in the magnetosheath and has also added carbon, nitrogen, magnesium, and sulfur to the list. There is strong evidence that these magnetosheath abundances are representative of the solar wind. Other sources of solar wind abundances are Solar Energetic Particle experiments and Apollo lunar foils. When comparing the abundances from all of these sources with photospheric abundances, it is clear that helium is depleted in the solar wind while silicon and iron are enhanced. Solar wind abundances for carbon, nitrogen, oxygen, and neon correlate well with the photospheric values. The incorporation of minor ions into the solar wind appears to depend upon both the ionization times for the elements and the Coulomb drag exerted by the outflowing proton flux.

  9. Abundances in very metal-poor stars

    NASA Astrophysics Data System (ADS)

    Johnson, Jennifer Anne

    We measured the abundances of 35 elements in 22 field red giants and a red giant in the globular cluster M92. We found the [Zn/Fe] ratio increases with decreasing [Fe/H], reaching ~0.3 at [Fe/H] = -3.0. While this is a larger [Zn/Fe] than found by previous investigators, it is not sufficient to account for the [Zn/Fe] observed in the damped Lyα systems. We test different models for the production of the s-process elements by comparing our [Y/Zr] values, which have been produced by the r- process, to predictions of what the s-process does not produce. We find that the models of Arlandini et al. (1999), which calculate s-process production in a model AGB star, agree the best. We then look at the r-process abundances across a wide range in mass. The [Y/Ba] values for most of our stars cluster around -0.30, but there are three outliers with [Y/Ba] values up to 1 dex higher. Thus the heavy element abundances do not show the same pattern from Z = 39 to Z = 56. However, our abundances ratios from Pd (Z = 46) to Yb (Z = 70) are consistent with a scaled solar system r- process pattern, arguing that at least the heavy r- process elements are made in a universal pattern. If we assume that this same pattern hold through thorium, we can determine the ages of our stars from the present abundance of radioactive thorium and an initial thorium abundance based on the abundance of stable heavy elements. Our results for five stars are consistent with those stars being the same age. Our mean age is 10.8 +/- 2 Gyr. However that result depends critically on the assumed Th/stable ratio, which we adopt from models of the r-process. For an average age of 15 Gyrs, the initial Th/Eu ratio we would need is 0.590. Finally, the [element/Fe] ratios for elements in the iron group and lower do not show any dispersion, unlike for the r- process elements such as Y and Ba. Therefore the individual contributions of supernovae have been erased for the lighter elements.

  10. Elemental abundances and classification of carbon-enhanced metal-poor stars

    NASA Astrophysics Data System (ADS)

    Allen, D. M.; Ryan, S. G.; Rossi, S.; Beers, T. C.; Tsangarides, S. A.

    2012-12-01

    We present a detailed study of carbon-enhanced metal-poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2 m William Herschel Telescope in 2001 and 2002, using the Utrecht Echelle Spectrograph, at a resolving power R ~ 52 000 and S/N ~ 40, covering the wavelength range λλ3700-5700 Å. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750 K to 7100 K, log g from 1.5 to 4.3, and metallicities -3.0 ≤ [Fe/H] ≤ -1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production. Tables 1, 3, 4, 8-10, A.1, and B.1-B.4 are available in electronic form at http://www.aanda.orgFull Tables 2, 5, and 7 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/548/A34

  11. Transition Element Abundances in MORB Basalts

    NASA Astrophysics Data System (ADS)

    Yang, S.; Humayun, M.; Salters, V. J.; Fields, D.; Jefferson, G.; Perfit, M. R.

    2012-12-01

    The mineralogy of the mantle sources of basalts is an important, but hard to constrain parameter, especially with the basalts as chemical probes of major element mantle composition. Geophysical models imply that the deep mantle may have significant variations in Fe and Si relative to the ambient mantle sampled by MORB. Some petrological models of sub-ridge melting involve both pyroxenite and peridotite, implying that basalts preferentially sample a pyroxenite endmember. The First-Row Transition Elements (FRTE), Ga and Ge are compatible to moderately incompatible during partial melting, and are sensitive to mineralogical variability in the mantle and thus can provide constraints on mantle source mineralogy for MORB. We have analyzed major elements, FRTE, Ga and Ge on 231 basaltic glasses from the Middle Atlantic Ridge (MAR between -23°S to 36.44°N), 30 Mid-Cayman Rise basaltic glasses, 12 glasses from the Siqueiros Fracture Zone (EPR), 9 glasses from the Blanco Trough, Juan de Fuca ridge, and Galapagos Spreading Centers (EPR), and 4 Indian Ocean MORB. Large spots (150 μm) were precisely (±1%) analyzed by a New Wave UP193FX excimer (193 nm) laser ablation system coupled to a high-resolution ICP-MS at the National High Magnetic Field Laboratory using a high ablation rate (50 Hz) to yield blank contributions <1% for all elements, particularly Ge. The data demonstrate that the Ge/Si (6.96 x 10E-6 ± 3%, 1σ) and Fe/Mn (55 ± 2%) ratios for MORB are insensitive to fractional crystallization within the MgO range 6%-10%. MORB have Zn/Fe (9.9 x 10E-4 ± 7%), Ga/Sc (0.37-0.50), Ga/Al (2.2 x 10E-4 ± 11%) ratios, with the variations mostly due to the effects of fractional crystallization. Recent experimental determination of FRTE, Ga and Ge partition coefficients provide a framework within which to interpret these data [1]. Using these new partition coefficients, we have modeled the sensitivity of each element to mineralogical variations in the mantle source. Olivine

  12. Element abundance measurements in gas-rich galaxies at z~5

    NASA Astrophysics Data System (ADS)

    Poudel, Suraj; Kulkarni, Varsha; Morrison, Sean; Peroux, Celine; Som, Debopam; Rahmani, Hadi; Quiret, Samuel

    2018-01-01

    Element abundances in high-redshift galaxies offer key constraints on models of the chemical evolution of galaxies. The chemical composition of galaxies at z>~5 are especially important since they constrain the star formation history in the first ~1 Gyr after the Big Bang and the initial mass function of early stars. Observations of damped Lyman-alpha (DLA) absorbers in quasar spectra enable robust measurements of the element abundances in distant gas-rich galaxies. In particular, abundances of volatile elements such as S, O and refractory elements such as Si, Fe allow determination of the dust-corrected metallicity and the depletion strength in the absorbing galaxies. Unfortunately measurements for volatile (nearly undepleted) elements are very sparse for DLAs at z > 4.5. We present abundance measurements of O, C, Si and Fe for three gas-rich galaxies at z~5 using observations from the Very Large Telescope (VLT) X-shooter spectrograph and the Keck Echellette Spectrograph and Imager. Our study has doubled the existing sample of measurements of undepleted elements at z > 4.5. After combining our measurements with those from the literature, we find that the cosmological mean metallicity of z ˜ 5 absorbers is consistent with the prediction based on z < 4.5 DLAs within < 0.5 σ. Thus, we find no significant evidence of a sudden drop in metallicity at z > 4.7 as reported by prior studies. Some of the absorbers show evidence of depletion of elements on dust grains, e.g. low [Si/O] or [Fe/O]. These absorbers along with other z~5 absorbers from the literature show some peculiarities in the relative abundances, e.g. low [C/O] in several absorbers and high [Si/O] in one absorber. We also find that the metallicity vs. velocity dispersion relation of z~5 absorbers may be different from that of lower-redshift absorbers.We acknowledge support from NASA grant NNX14AG74G and NASA/STScI support for HST programs GO-12536, 13801 to the Univ. of South Carolina.

  13. Trace element abundances in single presolar silicon carbide grains by synchrotron X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Kashiv, Yoav

    2004-12-01

    Synchrotron x-ray fluorescence (SXRF) was applied to the study of presolar grains for the first time in this study. 41 single SiC grains of the KJF size fraction (mass-weighted median size of 1.86 μm) from the Murchison (CM2) Meteorite were analyzed. The absolute abundances of the following elements were determined (not every element in every grain): S, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Sr, Y, Zr, Nb, Mo, Ru, Os, Ir and Pt (underlined elements were detected here for the first time in single grains). There is good agreement between the heavier trace element abundances in the grains and s-process nucleosynthesis calculations. It suggests that smaller 13C pocket sizes are needed in the parent stars, a free parameter in the stellar models, than is deduced from isotopic analyses of s-, and s-mainly, elements, such as Zr and Mo. In addition, the data confirms the radiogenic nature of the Nb in the grains, due to the in situ decay of 93Zr (t 1/2 = 1.5 × 106 year). The data suggest that the trace elements condensed into the host SiC grains by a combination of condensation in solid solution and incorporation of subgrains. It seems that many of the trace elements reside mainly in subgrains of two solid solution: (1)a TiC based solid solution, and (2)a Mo-Ru carbide based solid solution. The presence of subgrains of an Fe-Ni alloy solid solution is suggested as well. Subgrains of all 3 solid solutions were observed previously in presolar graphite grains.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat.

  14. Cosmic-ray abundances of the even charge elements from Sn-50 to Ce-58 measured on HEAO-3

    NASA Technical Reports Server (NTRS)

    Stone, E. C.; Garrard, T. L.; Krombel, K. E.; Binns, W. R.; Israel, M. H.; Klarmann, J.; Brewster, N. R.; Fickle, R. K.; Waddington, C. J.

    1983-01-01

    Elements with even atomic number (Z) in the interval Z = 50-58 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO-3 satellite. The observation that Sn-50 and Ba-56 are more abundant than Te-52 and Xe-54 indicates a substantial s-process contribution to the cosmic ray source. A significant abundance of Ce-58 provides further support for this finding.

  15. Source abundances of ultra heavy elements derived from UHCRE measurements.

    PubMed

    Domingo, C; Font, J; Baixeras, C; Fernandez, F

    1996-11-01

    A total of 205 tracks have been located, measured, and positively identified as originating from Ultra Heavy (Z > or = 65) cosmic ray ions with energies over 2 GeV/amu in the 10 UHCRE plastic track detector (mainly Lexan polycarbonate) stacks studied by our Group. About 40 values of reduced etch rate S have been obtained along each of these tracks. A method based on determining the gradient of S, together with calibration in accelerators, is used to determine the charge of each ion resulting in one of such tracks to obtain the charge spectrum of the recorded Ultra Heavy ions. The abundance ratio of ions with 87 < or = Z < or = 100 to those with 74 < or = Z < or = 86 as well as that of ions with 81 < or = Z < or = 86 to those with 74 < or = Z < or = 80 are calculated at 0.016 and 0.32, respectively, which agree with the values obtained from measurements in the HEAO-3 and Ariel-6 experiments. The abundance ratio of ions with 70 < or = Z < or = 73 to those with 74 < or = Z < or = 86 is also calculated, but its value (0.074) did not seem to be significant because of our detectors' low registration efficiency in the charge range 70 < or = Z < or = 73. A computer program developed by our Group, based on the Leaky Box cosmic ray propagation model, has been used to determine the source abundances of cosmic ray nuclei with Z > or = 65 inferred from the abundances measured in the UHCRE. It appeared that r-process synthesized elements were overabundant compared to the Solar System abundances, as predicted by other authors.

  16. Neutron-capture element abundances in the planetary nebula NGC 5315 from deep high-resolution optical and near-IR spectrophotometry

    NASA Astrophysics Data System (ADS)

    Madonna, S.; García-Rojas, J.; Sterling, N. C.; Luridiana, V.

    2017-03-01

    We have done a spectroscopical analysis of the type I planetary nebula (PN) NGC 5315, through high-resolution (R ˜ 40000) optical spectroscopy with UVES at the 8.2m Very Large Telescope, and medium-resolution (R ˜ 4800) near-IR spectroscopy with FIRE at the 6.5m Magellan Baade telescope, covering a wide spectral range from 0.31 μm to 2.50μm. The main aim of this work is to investigate the slow neutron(n)-capture process (the s-process) in the Asymptotic Giant Branch (AGB) star progenitor of a type I PNe. We detected and identified about 700 features, including lines from the n-capture elements Kr, Se, and possibly Br and Xe. We compute physical conditions using line ratios of common ions. Ionic abundances are computed for the species with available atomic data. We calculate total abundances using recent ionization correction factors (ICFs) or by summing ionic abundances. Our results for common elements are in good agreement with previous works on the same object. We do not find a substantial s-process enrichment in NGC 5315, which is typical for type I PNe.

  17. The abundance and relative volatility of refractory trace elements in Allende Ca,Al-rich inclusions - Implications for chemical and physical processes in the solar nebula

    NASA Technical Reports Server (NTRS)

    Kornacki, Alan S.; Fegley, Bruce, Jr.

    1986-01-01

    The relative volatilities of lithophile refractory trace elements (LRTE) were determined using calculated 50-percent condensation temperatures. Then, the refractory trace-element abundances were measured in about 100 Allende inclusions. The abundance patterns found in Allende Ca,Al-rich inclusions (CAIs) and ultrarefractory inclusions were used to empirically modify the calculated LRTE volatility sequence. In addition, the importance of crystal-chemical effects, diffusion constraints, and grain transport for the origin of the trace-element chemistry of Allende CAIs (which have important implications for chemical and physical processes in the solar nebula) is discussed.

  18. Heavy-Element Abundances in Blue Compact Galaxies

    NASA Astrophysics Data System (ADS)

    Izotov, Yuri I.; Thuan, Trinh X.

    1999-02-01

    We present high-quality ground-based spectroscopic observations of 54 supergiant H II regions in 50 low-metallicity blue compact galaxies with oxygen abundances 12+logO/H between 7.1 and 8.3. We use the data to determine abundances for the elements N, O, Ne, S, Ar, and Fe. We also analyze Hubble Space Telescope (HST) Faint Object Spectrograph archival spectra of 10 supergiant H II regions to derive C and Si abundances in a subsample of seven BCGs. The main result of the present study is that none of the heavy element-to-oxygen abundance ratios studied here (C/O, N/O, Ne/O, Si/O, S/O, Ar/O, Fe/O) depend on oxygen abundance for BCGs with 12+logO/H<=7.6 (Z<=Zsolar/20). This constancy implies that all of these heavy elements have a primary origin and are produced by the same massive (M>=10 Msolar) stars responsible for O production. The dispersion of the ratios C/O and N/O in these galaxies is found to be remarkably small, being only +/-0.03 and +/-0.02 dex, respectively. This very small dispersion is strong evidence against any time-delayed production of C and primary N in the lowest metallicity BCGs (secondary N production is negligible at these low metallicities). The absence of a time-delayed production of C and N is consistent with the scenario that galaxies with 12+logO/H<=7.6 are now undergoing their first burst of star formation, and that they are therefore young, with ages not exceeding 40 Myr. If very low metallicity BCGs are indeed young, this would argue against the commonly held belief that C and N are produced by intermediate-mass (3 Msolar<=M<=9 Msolar) stars at very low metallicities, as these stars would not have yet completed their evolution in these lowest metallicity galaxies. In higher metallicity BCGs (7.6<12+logO/H<8.2), the abundance ratios Ne/O, Si/O, S/O, Ar/O, and Fe/O retain the same constant value they had at lower metallicities. By contrast, there is an increase of C/O and N/O along with their dispersions at a given O. We interpret this

  19. Abundances in 54 Chemical Elements in Przybylski's Star: HD 101065

    NASA Astrophysics Data System (ADS)

    Cowley, Charles R.; et al.

    We report abundances from carbon through uranium, based on ESO observations: SN >= 200, resolution 80,000. Light elements, through the iron group scatter with respect to the standard abundance distribution (SAD). Carbon and oxygen are mildly depleted, as are iron and nickel, while titanium and cobalt are enhanced. Calcium is depleted, but silicon, sulfur, and scandium are solar. The heavier elements including some 4d and REE's are generally enhanced by 3 to 4 dex. This is not extreme for an Ap star. The truly bizarre appearance of the spectrum is an an ionization phenomena. Some hotter Ap stars have comparable lanthanide abundances, but their second spectra are weaker due to double ionization. Our adopted model has a Te of 6600K, and log(g) = 4.2. Because of the high line opacity, the photospheric pressure is low, and convection is ineffective. Chemical separation has distorted the third r-process peak only slightly. The overall coherence of the heavier elements is remarkable. Additional information is available from http://www.astro.lsa.umich.edu/users/cowley/przyb.html. This abstract is based on a paper submitted to MNRAS, by CRC, and coauthors: T. A. Ryabchikova (Moscow & Vienna), F. Kupka (Vienna), D. Bord (Michigan), G. Mathys (ESO), and W. P. Bidelman (Case-Western Reserve).

  20. Abundance of Chemical Elements in RR Lyrae Variables and their Kinematic Parameters

    NASA Astrophysics Data System (ADS)

    Gozha, M. L.; Marsakov, V. A.; Koval', V. V.

    2018-03-01

    A catalog of the chemical and spatial-kinematic parameters of 415 RR Lyrae variables (Lyrids) in the galactic field is compiled. Spectroscopic determinations of the relative abundances of 13 chemical elements in 101 of the RR Lyrae variables are collected from 25 papers published between 1995 and 2017. The data from different sources are reduced to a single solar abundance scale. The mean weighted chemical abundances are calculated with coefficients inversely proportional to the reported errors. An analysis of the deviations in the published relative abundances in each star from the mean square values calculated from them reveals an absence of systematic biases among the results from the various articles. The rectangular coordinates of 407 of the RR Lyrae variables and the components of the three-dimensional (3D) velocities of 401 of the stars are calculated using data from several sources. The collected data on the abundances of chemical elements produced by various nuclear fusion processes for the RR Lyrae variables of the field, as well as the calculated 3D velocities, can be used for studying the evolution of the Galaxy.

  1. Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; White, W. M.; Jochum, K. P.; Hofmann, A. W.

    1986-01-01

    The hypothesis that the mantle Pb isotope ratios reflect continued extraction of Pb into the earth's core over geologic time is evaluated by studying the depeletion of chalcophile and siderophile elements in the mantle. Oceanic basalt samples are analyzed in order to determine the Pb, Sr, and Nd isotropic compositions and the abundances of siderophile and chalcophile elements and incompatible lithophile elements. The data reveal that there is no systematic variation of siderophile or chalcophile element abundances relative to abundances of lithophile elements and the Pb/Ce ratio of the mantle is constant. It is suggested that the crust formation involves nonmagmatic and magmatic processes.

  2. Chemical abundances and kinematics of TYC 5619-109-1

    NASA Astrophysics Data System (ADS)

    Pereira, C. B.; Smith, V. V.; Drake, N. A.; Roig, F.; Hasselquist, S.; Cunha, K.; Jilinski, E.

    2017-07-01

    Previous determinations of chemical abundances of the metal-poor red giant TYC 5619-109-1, derived via high-resolution near-infrared spectra from the Apache Point Observatory Galactic Evolution Experiment survey, indicate that this star is strongly enriched in the elements N and Al. Here, we obtain and analyse high-resolution optical spectra of TYC 5619-109-1 to verify these large N and Al overabundances and to measure abundances of a wider range of chemical elements. Our analysis confirms the N- and Al-rich nature of this star, and shows that the abundances of the s-process elements are also strongly enhanced, particularly in the heavy second s-process peak elements (Ba, La, Ce, Nd). Lighter s-process elements (Y, Zr) show smaller overabundances, and the ratio of the light-to-heavy s-process elements is consistent with the 13C(α, n)16O neutron source operating in a low-metallicity environment. The lack of Tc I lines and the abundance of Nb compared to Zr indicate that this red giant is probably not a thermally pulsing asymptotic giant branch (TP-AGB) star. Mass transfer from a former s-process-rich TP-AGB companion may produce the observed overabundances, but our radial velocity analysis provides no evidence that TYC 5619-109-1 is a binary with a white dwarf companion. We suggest that TYC 5619-109-1 formed from gas already strongly enriched in s-process elements, as found in many dwarf galaxies and globular clusters. A dynamical analysis reveals that there is only a small probability that TYC 5619-109-1 is an escaped member of a globular cluster, and in this case the most likely candidate would be ω Cen.

  3. Explaining the Ba, Y, Sr, and Eu abundance scatter in metal-poor halo stars: constraints to the r-process

    NASA Astrophysics Data System (ADS)

    Cescutti, G.; Chiappini, C.

    2014-05-01

    Context. Thanks to the heroic observational campaigns carried out in recent years we now have large samples of metal-poor stars for which measurements of detailed abundances exist. In particular, large samples of stars with metallicities -5 < [Fe/H] <-1 and measured abundances of Sr, Ba, Y, and Eu are now available. These data hold important clues on the nature of the contribution of the first stellar generations to the enrichment of our Galaxy. Aims: We aim to explain the scatter in Sr, Ba, Y, and Eu abundance ratio diagrams unveiled by the metal-poor halo stars. Methods: We computed inhomogeneous chemical evolution models for the Galactic halo assuming different scenarios for the r-process site: the electron-capture (EC) supernovae and the magnetorotationally driven (MRD) supernovae scenarios. We also considered models with and without the contribution of fast-rotating massive stars (spinstars) to an early enrichment by the s-process. A detailed comparison with the now large sample of stars with measured abundances of Sr, Ba, Y, Eu, and Fe is provided (both in terms of scatter plots and number distributions for several abundance ratios). Results: The scatter observed in these abundance ratios of the very metal-poor stars (with [Fe/H] <-2.5) can be explained by combining the s-process production in spinstars, and the r-process contribution coming from massive stars. For the r-process we have developed models for both the EC and the MRD scenarios that match the observations. Conclusions: With the present observational and theoretical constraints we cannot distinguish between the EC and the MRD scenarios in the Galactic halo. Independently of the r-process scenarios adopted, the production of elements by an s-process in spinstars is needed to reproduce the spread in abundances of the light neutron capture elements (Sr and Y) over heavy neutron capture elements (Ba and Eu). We provide a way to test our suggestions by means of the distribution of the Ba isotopic

  4. Isotope-abundance variations and atomic weights of selected elements: 2016 (IUPAC Technical Report)

    USGS Publications Warehouse

    Coplen, Tyler B.; Shrestha, Yesha

    2016-01-01

    There are 63 chemical elements that have two or more isotopes that are used to determine their standard atomic weights. The isotopic abundances and atomic weights of these elements can vary in normal materials due to physical and chemical fractionation processes (not due to radioactive decay). These variations are well known for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine, and thallium), and the standard atomic weight of each of these elements is given by IUPAC as an interval with lower and upper bounds. Graphical plots of selected materials and compounds of each of these elements have been published previously. Herein and at the URL http://dx.doi.org/10.5066/F7GF0RN2, we provide isotopic abundances, isotope-delta values, and atomic weights for each of the upper and lower bounds of these materials and compounds.

  5. Fossil Signatures Using Elemental Abundance Distributions and Bayesian Probabilistic Classification

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Storrie-Lombardi, Michael C.

    2004-01-01

    Elemental abundances (C6, N7, O8, Na11, Mg12, Al3, P15, S16, Cl17, K19, Ca20, Ti22, Mn25, Fe26, and Ni28) were obtained for a set of terrestrial fossils and the rock matrix surrounding them. Principal Component Analysis extracted five factors accounting for the 92.5% of the data variance, i.e. information content, of the elemental abundance data. Hierarchical Cluster Analysis provided unsupervised sample classification distinguishing fossil from matrix samples on the basis of either raw abundances or PCA input that agreed strongly with visual classification. A stochastic, non-linear Artificial Neural Network produced a Bayesian probability of correct sample classification. The results provide a quantitative probabilistic methodology for discriminating terrestrial fossils from the surrounding rock matrix using chemical information. To demonstrate the applicability of these techniques to the assessment of meteoritic samples or in situ extraterrestrial exploration, we present preliminary data on samples of the Orgueil meteorite. In both systems an elemental signature produces target classification decisions remarkably consistent with morphological classification by a human expert using only structural (visual) information. We discuss the possibility of implementing a complexity analysis metric capable of automating certain image analysis and pattern recognition abilities of the human eye using low magnification optical microscopy images and discuss the extension of this technique across multiple scales.

  6. Chemical Abundances of Hydrostatic and Explosive Alpha-elements in Sagittarius Stream Stars

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sheffield, Allyson A.; Cunha, Katia; Smith, Verne V.

    2018-05-01

    We analyze chemical abundances of stars in the Sagittarius (Sgr) tidal stream using high-resolution Gemini+GRACES spectra of 42 members of the highest surface-brightness portions of both the trailing and leading arms. Targets were chosen using a 2MASS+WISE color–color selection, combined with the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) radial velocities. In this Letter, we analyze [Fe/H] and α-elements produced by both hydrostatic (O, Mg) and explosive (Si, Ca, Ti) nucleosynthetic processes. The average [Fe/H] for our Sgr stream stars is lower than that for stars in the Sgr core, and stars in the trailing and leading arms show systematic differences in [Fe/H]. Both hydrostatic and explosive elements are depleted relative to Milky Way (MW) disk and halo stars, with a larger gap between the MW trend and Sgr stars for the hydrostatic elements. Chemical abundances of Sgr stream stars show similar patterns to those measured in the core of the Sgr dSph. We explore the ratio of hydrostatic to explosive α-elements [α h/ex] (which we refer to as the “HEx ratio”). Our observed HEx ratio trends for Sgr debris are deficient relative to MW stars. Via simple chemical evolution modeling, we show that these HEx ratio patterns are consistent with a Sgr IMF that lacks the most massive stars. This study provides a link between the chemical properties in the intact Sgr core and the significant portion of the Sgr system’s luminosity that is estimated to currently reside in the streams.

  7. Nucleosynthesis: Stellar and Solar Abundances and Atomic Data

    NASA Technical Reports Server (NTRS)

    Cowan, John J.; Lawler, James E.; Sneden, Christopher; DenHartog, E. A.; Collier, Jason; Dodge, Homer L.

    2006-01-01

    Abundance observations indicate the presence of often surprisingly large amounts of neutron capture (i.e., s- and r-process) elements in old Galactic halo and globular cluster stars. These observations provide insight into the nature of the earliest generations of stars in the Galaxy the progenitors of the halo stars responsible for neutron-capture synthesis. Comparisons of abundance trends can be used to understand the chemical evolution of the Galaxy and the nature of heavy element nucleosynthesis. In addition age determinations, based upon long-lived radioactive nuclei abundances, can now be obtained. These stellar abundance determinations depend critically upon atomic data. Improved laboratory transition probabilities have been recently obtained for a number of elements. These new gf values have been used to greatly refine the abundances of neutron-capture elemental abundances in the solar photosphere and in very metal-poor Galactic halo stars. The newly determined stellar abundances are surprisingly consistent with a (relative) Solar System r-process pattern, and are also consistent with abundance predictions expected from such neutron-capture nucleosynthesis.

  8. Platinum group element abundances in the upper continental crust revisited - New constraints from analyses of Chinese loess

    NASA Astrophysics Data System (ADS)

    Park, Jung-Woo; Hu, Zhaochu; Gao, Shan; Campbell, Ian H.; Gong, Hujun

    2012-09-01

    Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lowe than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys.2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir = 0.022 ppb (ng/g), Ru = 0.030 ppb, Rh = 0.018 ppb, Pt = 0.599 ppb, and Pd = 0.526 ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC.

  9. Abundances of neutron-capture elements in stars of the Galactic disk substructures

    NASA Astrophysics Data System (ADS)

    Mishenina, T. V.; Pignatari, M.; Korotin, S. A.; Soubiran, C.; Charbonnel, C.; Thielemann, F.-K.; Gorbaneva, T. I.; Basak, N. Yu.

    2013-04-01

    Aims: The aim of this work is to present and discuss the observations of the iron peak (Fe, Ni) and neutron-capture element (Y, Zr, Ba, La, Ce, Nd, Sm, and Eu) abundances for 276 FGK dwarfs, located in the Galactic disk with metallicity -1 < [Fe/H] < +0.3. Methods: Atmospheric parameters and chemical composition of the studied stars were determined from an high resolution, high signal-to-noise echelle spectra obtained with the echelle spectrograph ELODIE at the Observatoire de Haute-Provence (France). Effective temperatures were estimated by the line depth ratio method and from the Hα line-wing fitting. Surface gravities (log g) were determined by parallaxes and the ionization balance of iron. Abundance determinations were carried out using the LTE approach, taking the hyperfine structure for Eu into account, and the abundance of Ba was computed under the NLTE approximation. Results: We are able to assign most of the stars in our sample to the substructures of the Galaxy thick disk, thin disk, or Hercules stream according to their kinematics. The classification of 27 stars is uncertain. For most of the stars in the sample, the abundances of neutron-capture elements have not been measured earlier. For all of them, we provide the chemical composition and discuss the contribution from different nucleosynthesis processes. Conclusions: The [Ni/Fe] ratio shows a flat value close to the solar one for the whole metallicity range, with a small scatter, pointing to a nearly solar Ni/Fe ratio for the ejecta of both core-collapse SN and SNIa. The increase in the [Ni/Fe] for metallicity higher than solar is confirmed, and it is due to the metallicity dependence of 56Ni ejecta from SNIa. Under large uncertainty in the age determination of observed stars, we verified that there is a large dispersion in the AMR in the thin disk, and no clear trend as in the thick disk. That may be one of the main reasons for the dispersion, observed for the s-process elements in the thin disk (e

  10. Abundance patterns of the light neutron-capture elements in very and extremely metal-poor stars

    NASA Astrophysics Data System (ADS)

    Spite, F.; Spite, M.; Barbuy, B.; Bonifacio, P.; Caffau, E.; François, P.

    2018-03-01

    Aims: The abundance patterns of the neutron-capture elements in metal-poor stars provide a unique record of the nucleosynthesis products of the earlier massive primitive objects. Methods: We measured new abundances of so-called light neutron-capture of first peak elements using local thermodynamic equilibrium (LTE) 1D analysis; this analysis resulted in a sample of 11 very metal-poor stars, from [Fe/H] = -2.5 to [Fe/H] = -3.4, and one carbon-rich star, CS 22949-037 with [Fe/H] = -4.0. The abundances were compared to those observed in two classical metal-poor stars: the typical r-rich star CS 31082-001 ([Eu/Fe] > +1.0) and the r-poor star HD 122563 ([Eu/Fe] < 0.0), which are known to present a strong enrichment of the first peak neutron-capture elements relative to the second peak. Results: Within the first peak, the abundances are well correlated in analogy to the well-known correlation inside the abundances of the second-peak elements. In contrast, there is no correlation between any first peak element with any second peak element. We show that the scatter of the ratio of the first peak abundance over second peak abundance increases when the mean abundance of the second peak elements decreases from r-rich to r-poor stars. We found two new r-poor stars that are very similar to HD 122563. A third r-poor star, CS 22897-008, is even more extreme; this star shows the most extreme example of first peak elements enrichment to date. On the contrary, another r-poor star (BD-18 5550) has a pattern of first peak elements that is similar to the typical r-rich stars CS 31082-001, however this star has some Mo enrichment. Conclusions: The distribution of the neutron-capture elements in our very metal-poor stars can be understood as the combination of at least two mechanisms: one that enriches the forming stars cloud homogeneously through the main r-process and leads to an element pattern similar to the r-rich stars, such as CS 31082-001; and another that forms mainly lighter

  11. Abundances of Elements in Jupiter’s Atmosphere

    NASA Astrophysics Data System (ADS)

    Desch, Steven; Monga, Nikhil

    2014-11-01

    As measured by the Galileo mission, Jupiter’s atmosphere is enriched (relative to H and a protosolar composition) in Ar, Kr, Xe, C, N, S and P, by a similar factor of 3 [1]; it is depleted in He, Ne and O. Fractionation of Ar from H requires temperatures < 35 K [2], but multiple theories exist invoking trapping of species in ices, in principle explaining these enrichments [3-5]. He is depleted by 18%, and Ne by 88% [1]. At the ~1 Mbar level in Jupiter’s atmosphere, where H transitions to a metallic state, He droplets can form that precipitate to Jupiter’s core; Ne, but not Ar, is expected to dissolve into these droplets, explaining the depletion of both He and Ne [6]. The factor-of-2 depletion of O is currently unexplained but is attributed to meteorological effects [7]. The Juno mission en route to Jupiter will measure the global abundance of O [8].We present a model for the enrichments of Ar, Kr, Xe, C, N, S and P. Our model [8] builds on that of [5] in which Jupiter accretes nebular gas depleted in H by photoevaporation. Our model improvements allow enrichments with less mass loss, and explain how water vapor can be produced at T < 35 K, necessary for trapping of Ar and other species. We predict that Jupiter accreted with a factor-of-3 enrichment of O, but was then sequestered into Jupiter’s core along with He and Ne, potentially explaining its factor-of-2 depletion.References:[1] Desch, SJ, Shumway, J, & Monga, N, submitted to Icarus.[2] Bar-Nun, A, Herman, G, Laufer, D, & Rappaport, ML 1985. Icarus 63, 317.[3] Owen, T, et al.1999, Nature 402, 269. [4] Gautier, D, Hersant, F, Mousis, O, & Lunine, JI 2001, Ap.J. 550, L227.[5] Guillot, T & Hueso, R 2006, Mon. Not. Roy. Astron. Soc. 367, L47.[6] Wilson, HF & Militzer, B 2010, Phys Rev Lett.104, 121101.[7] Atreya, SK et al. 1999, Planet. Space Sci. 47, 1243.[7] Janssen, MA et al. 2005, Icarus 173, 447. [8] Monga, N & Desch, SJ, submitted to Ap.J.

  12. Heavy Element Abundances in Planetary Nebulae from Deep Optical Echelle Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mashburn, Amanda; Sterling, Nicholas C.; Dinerstein, Harriet L.; Garofali, Kristen; Jensema, Rachael; Turbyfill, Amanda; Wieser, Hannah-Marie N.; Reed, Evan C.; Redfield, Seth

    2016-01-01

    We present the abundances of neutron(n)-capture elements (atomic number Z > 30) and iron determined from deep optical echelle spectroscopy of 14 Galactic planetary nebulae (PNe). The spectra were obtained with the 2D-coudé spectrograph on the 2.7-m Harlan J. Smith telescope at McDonald Observatory. The abundances of n-capture elements can be enhanced in PNe due to slow n-capture nucleosynthesis in the progenitor asymptotic giant branch (AGB) stars. The high spectral resolution of these data (R = 36,700) allow most n-capture element emission lines to be resolved from other nebular and telluric features. We detect Kr in all of the observed PNe (with multiple ions detected in several objects), while Br, Rb, and Xe were each detected in 4--5 objects. Using the new Kr ionization correction factors (ICFs) of Sterling et al. (2015, ApJS, 218, 25), we find [Kr/O] abundances ranging from 0.05 to 1.1 dex. We utilize approximate ICFs for the other n-capture elements, and find slightly lower enrichments for Br and Rb (-0.1 to 0.7 dex), while Xe is enhanced relative to solar by factors of two to 30. The [Xe/Kr] ratios range from -0.3 to 1.4 dex, indicating a significant range in neutron exposures in PN progenitor stars. Interestingly, the largest [Xe/Kr] ratio is found in the thick-disk PN NGC 6644, which has a lower metallicity than the other observed PNe. We detect iron emission lines in all but one target. Fe can be depleted into dust grains in ionized nebulae, and its abundance thus provides key information regarding dust-to-gas ratios and grain destruction processes. We find that [Fe/O] ranges from -1.3 to -0.7 dex in the observed PNe, a smaller spread of depletion factors than found in recent studies (Delgado-Inglada & Rodriguez 2014, ApJ, 784, 173) though this may be due in part to our smaller sample. These data are part of a larger study of heavy elements in PNe, which will provide more accurate determinations of n-capture element abundances than previous estimates in

  13. The elemental abundances (with uncertainties) of the most Earth-like planet

    NASA Astrophysics Data System (ADS)

    Wang, Haiyang S.; Lineweaver, Charles H.; Ireland, Trevor R.

    2018-01-01

    To first order, the Earth as well as other rocky planets in the Solar System and rocky exoplanets orbiting other stars, are refractory pieces of the stellar nebula out of which they formed. To estimate the chemical composition of rocky exoplanets based on their stellar hosts' elemental abundances, we need a better understanding of the devolatilization that produced the Earth. To quantify the chemical relationships between the Earth, the Sun and other bodies in the Solar System, the elemental abundances of the bulk Earth are required. The key to comparing Earth's composition with those of other objects is to have a determination of the bulk composition with an appropriate estimate of uncertainties. Here we present concordance estimates (with uncertainties) of the elemental abundances of the bulk Earth, which can be used in such studies. First we compile, combine and renormalize a large set of heterogeneous literature values of the primitive mantle (PM) and of the core. We then integrate standard radial density profiles of the Earth and renormalize them to the current best estimate for the mass of the Earth. Using estimates of the uncertainties in i) the density profiles, ii) the core-mantle boundary and iii) the inner core boundary, we employ standard error propagation to obtain a core mass fraction of 32.5 ± 0.3 wt%. Our bulk Earth abundances are the weighted sum of our concordance core abundances and concordance PM abundances. Unlike previous efforts, the uncertainty on the core mass fraction is propagated to the uncertainties on the bulk Earth elemental abundances. Our concordance estimates for the abundances of Mg, Sn, Br, B, Cd and Be are significantly lower than previous estimates of the bulk Earth. Our concordance estimates for the abundances of Na, K, Cl, Zn, Sr, F, Ga, Rb, Nb, Gd, Ta, He, Ar, and Kr are significantly higher. The uncertainties on our elemental abundances usefully calibrate the unresolved discrepancies between standard Earth models under

  14. Low Abundances of Highly Siderophile Elements in the Lunar Mantle: Evidence for Prolonged Late Accretion

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Horan, M. F.; Shearer, C. K.; Papike, J. J.

    2004-01-01

    The highly siderophile elements (HSE: including Re, Au, Ir, Os, Ru, Pt, Pd, Rh) are strongly partitioned into metal relative to silicates. In the terrestrial planets these elements are concentrated in metallic cores. Earth s mantle has sufficiently high abundances of the HSE (0.008 times CI abundances) that it has been hypothesized approximately 0.1-0.5% of the mass of the Earth was added following the last major interaction between the core and mantle [e.g. 1]. The additional material added to the Earth and Moon has been termed a late veneer , and the process has often been termed late accretion [2]. The timing of the dominant late accretionary period of the Earth and Moon is still poorly known. The abundances of HSE in the lunar mantle could provide important constraints on when the late veneer was added. The material that ultimately became the silicate portion of the Moon was likely stripped of most of its HSE prior to and during coalescence of the Moon. Consequently the initial lunar mantle likely had very low concentrations of the HSE. Unlike Earth, the generation of permanent lunar crust by 4.4 Ga prevented subsequent additions of HSE to the lunar mantle via continued accretion. Thus, if a substantial portion of the late veneer was added after 4.4 Ga, the lunar mantle should have retained very low HSE concentrations. Conversely, if the late veneer was mostly added prior to 4.4 Ga, HSE abundances in the lunar mantle may be roughly similar to abundances in the terrestrial mantle.

  15. Heavy-Element Abundances in Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.

    2004-01-01

    We survey the relative abundances of elements with 1 less than or = Z less than or = 82 in solar energetic particle (SEP) events observed at 2 - 10 MeV amu" during nearly 9 years aboard the Wind spacecraft, with special emphasis on enhanced abundances of elements with 2Z greater than or = 34. Abundances of Fe/O again show a bimodal distribution with distinct contributions from impulsive and gradual SEP events as seen in earlier solar cycles. Periods with greatly enhanced abundances of (50 less than or = Z less than or = 56)/O, like those with enhanced He-3/He-4, fall prominently in the Fe-rich population of the impulsive SEP events. In a sample of the 39 largest impulsive events, 25 have measurable enhancements in (50 less than or = Z less than or = 56)/O and (76 less than or = Z less than or = 82)/O, relative to coronal values, ranging from approx. 100 to 10,000. By contrast, in a sample of 45 large gradual events the corresponding enhancements vary from approx. 0.2 to 20. However, the magnitude of the heavy-element enhancements in impulsive events is less striking than their strong correlation with the Fe spectral index and flare size, with the largest enhancements occurring in flares with the steepest Fe spectra, the smallest Fe fluence, and the lowest X-ray intensity, as reported here for the first time Thus it seem that small events with low energy input can produce only steep spectra of the dominant species but accelerate rare heavy elements with great efficiency, probably by selective absorption of resonant waves in the flare plasma. With increased energy input, enhancements diminish, as heavy ions are depleted, and spectra of the dominant species harden.

  16. Heavy-Element Abundances in Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Ng, C. K.

    2004-01-01

    We survey the relative abundances of elements with 1 < or equal to Z < or equal to 82 in solar energetic particle (SEP) events observed at 2-10 MeV/amu during nearly 9 years aboard the Wind spacecraft, with special emphasis on enhanced abundances of elements with Z > or equal to 34. Abundances of Fe/O again show a bimodal distribution with distinct contributions from impulsive and gradual SEP events as seen in earlier solar cycles. Periods with greatly enhanced abundances of (50 < or equal to Z < or equal to 56)/O, like those with enhanced (3)He/(4)He, fall prominently in the Fe-rich population of the impulsive SEP events. In a sample of the 39 largest impulsive events, 25 have measurable enhancements in (50 < or equal to z < or equal to 56)/O and (76 < or equal to Z < or equal to 82)/O, relative to coronal values, ranging from approx. 100 to 10,000. By contrast, in a sample of 45 large gradual events the corresponding enhancements vary from approx. 0.2 to 20. However, the magnitude of the heavy-element enhancements in impulsive events is less striking than their strong correlation with the Fe spectral index and flare size, with the largest enhancements occurring in flares with the steepest Fe spectra, the smallest Fe fluence, and the lowest X-ray intensity, as reported here for the first time. Thus it seems that small events with low energy input can produce only steep spectra of the dominant species but accelerate rare heavy elements with great efficiency, probably by selective absorption of resonant waves in the flare plasma. With increased energy input, enhancements diminish, as heavy ions are depleted, and spectra of the dominant species harden.

  17. S-process studies using single and pulsed neutron exposures

    NASA Astrophysics Data System (ADS)

    Beer, H.

    The formation of heavy elements by slow neutron capture (s-process) is investigated. A pulsed neutron irradiation leading to an exponential exposure distribution is dominant for nuclei from A = 90 to 200. For the isotopes from iron to zirconium an additional 'weak' s-process component must be superimposed. Calculations using a single or another pulsed neutron exposure for this component have been carried out in order to reproduce the abundance pattern of the s-only and s-process dominant isotopes. For the adjustment of these calculations to the empirical values, the inclusion of new capture cross section data on Se76 and Y89 and the consideration of the branchings at Ni63, Se79, and Kr85 was important. The combination of an s-process with a single and a pulsed neutron exposure yielded a better representation of empirical abundances than a two component pulsed s-process.

  18. Evolution of heavy-element abundances in the Galactic halo and disk

    NASA Technical Reports Server (NTRS)

    Mathews, G. J.; Cowan, J. J.; Schramm, D. N.

    1988-01-01

    The constraints on the universal energy density and cosmological constant from cosmochronological ages and the Hubble age are reviewed. Observational evidence for the galactic chemical evolution of the heavy-element chronometers is descirbed in the context of numerical models. The viability of the recently discovered Th/Nd stellar chronometer is discussed, along with the suggestion that high r-process abundances in metal-poor stars may have resulted from a primordial r-process, as may be required by some inhomogeneous cosmologies.

  19. A COMPARISON OF STELLAR ELEMENTAL ABUNDANCE TECHNIQUES AND MEASUREMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hinkel, Natalie R.; Young, Patrick A.; Pagano, Michael D.

    2016-09-01

    Stellar elemental abundances are important for understanding the fundamental properties of a star or stellar group, such as age and evolutionary history, as well as the composition of an orbiting planet. However, as abundance measurement techniques have progressed, there has been little standardization between individual methods and their comparisons. As a result, different stellar abundance procedures determine measurements that vary beyond the quoted error for the same elements within the same stars. The purpose of this paper is to better understand the systematic variations between methods and offer recommendations for producing more accurate results in the future. We invited amore » number of participants from around the world (Australia, Portugal, Sweden, Switzerland, and the United States) to calculate 10 element abundances (C, O, Na, Mg, Al, Si, Fe, Ni, Ba, and Eu) using the same stellar spectra for four stars (HD 361, HD 10700, HD 121504, and HD 202206). Each group produced measurements for each star using (1) their own autonomous techniques, (2) standardized stellar parameters, (3) a standardized line list, and (4) both standardized parameters and a line list. We present the resulting stellar parameters, absolute abundances, and a metric of data similarity that quantifies the homogeneity of the data. We conclude that standardization of some kind, particularly stellar parameters, improves the consistency between methods. However, because results did not converge as more free parameters were standardized, it is clear there are inherent issues within the techniques that need to be reconciled. Therefore, we encourage more conversation and transparency within the community such that stellar abundance determinations can be reproducible as well as accurate and precise.« less

  20. Measuring Elemental Abundances in Impulsive Heating Events with EIS

    NASA Astrophysics Data System (ADS)

    Warren, Harry; Doschek, George A.; Young, Peter

    2015-04-01

    It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have indicated that in the solar corona low FIP elements, such as Fe, Si, and Mg, are enriched relative to high FIP elements, such as H, He, C, N, and O. In this paper we report on measurements of plasma composition made during transient heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O IV, V, and VI emission lines are enhanced relative to emission lines from Mg V, VI, and VII and indicate a composition close to that of the photosphere. Differential emission measure calculations show a broad distribution of temperatures in these events. Long-lived coronal structures, in contrast, show an enrichment of low FIP elements and relatively narrow temperature distributions. We conjecture that plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher frequency heating leading to the accumulation of low-FIP elements in the corona.

  1. Heavy-element yields and abundances of asymptotic giant branch models with a Small Magellanic Cloud metallicity

    NASA Astrophysics Data System (ADS)

    Karakas, Amanda I.; Lugaro, Maria; Carlos, Marília; Cseh, Borbála; Kamath, Devika; García-Hernández, D. A.

    2018-06-01

    We present new theoretical stellar yields and surface abundances for asymptotic giant branch (AGB) models with a metallicity appropriate for stars in the Small Magellanic Cloud (SMC, Z = 0.0028, [Fe/H] ≈ -0.7). New evolutionary sequences and post-processing nucleosynthesis results are presented for initial masses between 1 and 7 M⊙, where the 7 M⊙ is a super-AGB star with an O-Ne core. Models above 1.15 M⊙ become carbon rich during the AGB, and hot bottom burning begins in models M ≥ 3.75 M⊙. We present stellar surface abundances as a function of thermal pulse number for elements between C to Bi and for a selection of isotopic ratios for elements up to Fe and Ni (e.g. 12C/13C), which can be compared to observations. The integrated stellar yields are presented for each model in the grid for hydrogen, helium, and all stable elements from C to Bi. We present evolutionary sequences of intermediate-mass models between 4 and 7 M⊙ and nucleosynthesis results for three masses (M = 3.75, 5, and 7 M⊙) including s-process elements for two widely used AGB mass-loss prescriptions. We discuss our new models in the context of evolved AGB and post-AGB stars in the SMCs, barium stars in our Galaxy, the composition of Galactic globular clusters including Mg isotopes with a similar metallicity to our models, and to pre-solar grains which may have an origin in metal-poor AGB stars.

  2. Elemental Abundances in NGC 3516

    NASA Technical Reports Server (NTRS)

    Turner, T. J.; Kraemer, S. B.; Mushotzky, R. F.; George, I. M.; Gabel, J. R.

    2003-01-01

    We present Reflection Grating Spectrometer data from an XMM-Newton observation of the Seyfert 1 galaxy NGC 3516, taken while the continuum source was in an extremely low flux state. This observation offers a rare opportunity for a detailed study of emission from a Seyfert 1 galaxy as these are usually dominated by high nuclear continuum levels and heavy absorption. The spectrum shows numerous narrow emission lines (FWHM approximately less than 1300 kilometers per second) in the 0.3 - 2 keV range, including the H-like lines of C, N, and O and the He-like lines of N, O and Ne. The emission-line ratios and the narrow width of the radiative recombination continuum of CVI indicate that the gas is photoionized and of fairly low temperature (kT approximately less than 0.01 keV). The availability of emission lines from different elements for two iso-electronic sequences allows us to constrain the element abundances. These data show that the N lines are far stronger than would be expected from gas of solar abundances. Based on our photoionization models we find that nitrogen is overabundant in the central regions of the galaxy, compared to carbon, oxygen and neon by at least a factor of 2.5. We suggest that this is the result of secondary production of nitrogen in intermediate mass stars, and indicative of the history of star formation in NGC 3516.

  3. The Unexplored Domains of the s-Process

    NASA Astrophysics Data System (ADS)

    Roederer, Ian

    2016-10-01

    Understanding the origin of the elements is one of the major challenges of modern astrophysics. Abundance measurements in late-type stars are used to test nucleosynthesis models, and the models in turn reveal the nature of the progenitor star(s) that produced the metals observed today. Elements listed along the bottom two-thirds of the periodic table are produced by neutron-capture reactions, such as the r-process or s-process. Previous studies have expanded the chemical inventory of individual r-process-enhanced stars to >50 elements per star. Here, we propose to do the same for an s-process-enhanced star.We propose new high-resolution STIS/E230H observations (2024-2301 Angstroms) of the star HD 196944, the UV-brightest s-process-enhanced metal-poor star in the sky. Lines of Se I, Mo II, Cd I, Cd II, Sn I, Sb I, Te I, Yb II, W II, Re II, Os II, Pt I, Pb II, and Bi I should be detectable in these observations because of the high spectral resolution and S/N. No star offers the opportunity to simultaneously detect all of these elements, and several of them could be detected for the first time. We will combine these NUV detections with optical detections to test many specific predictions of the s-process nucleosynthesis models in a way that has not been possible until now. This is particularly timely, for example, because s-process models have recently been shown to be uncertain at the termination point around Pb-Bi.

  4. STATISTICAL CHARACTERISTICS OF ELEMENTAL ABUNDANCE RATIOS: OBSERVATIONS FROM THE ACE SPACECRAFT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, L.-L.; Zhang, H.

    We statistically analyze the elemental galactic cosmic ray (GCR) composition measurements of elements 5 ≤ Z ≤ 28 within the energy range 30–500 MeV/nucleon from the CRIS instrument on board the ACE spacecraft in orbit about the L1 Lagrange point during the period from 1997 to 2014. Similarly to the last unusual solar minimum, the elevated elemental intensities of all heavy nuclei during the current weak solar maximum in 2014 are ∼40% higher than that of the previous solar maximum in 2002, which has been attributed to the weak modulation associated with low solar activity levels during the ongoing weakestmore » solar maximum since the dawn of space age. In addition, the abundance ratios of heavy nuclei with respect to elemental oxygen are generally independent of kinetic energy per nucleon in the energy region 60–200 MeV/nuc, in good agreement with previous experiments. Furthermore, the abundance ratios of most relatively abundant species, except carbon, exhibit considerable solar-cycle variation, which are obviously positively correlated with the sunspot numbers with about one-year time lag. We also find that the percentage variation of abundance ratios for most elements are approximately identical. These preliminary results provide valuable insights into the characteristics of elemental heavy nuclei composition and place new and significant constraints on future GCR heavy nuclei propagation and modulation models.« less

  5. Cosmological implications of light element abundances: theory.

    PubMed Central

    Schramm, D N

    1993-01-01

    Primordial nucleosynthesis provides (with the microwave background radiation) one of the two quantitative experimental tests of the hot Big Bang cosmological model (versus alternative explanations for the observed Hubble expansion). The standard homogeneous-isotropic calculation fits the light element abundances ranging from 1H at 76% and 4He at 24% by mass through 2H and 3He at parts in 105 down to 7Li at parts in 1010. It is also noted how the recent Large Electron Positron Collider (and Stanford Linear Collider) results on the number of neutrinos (Nnu) are a positive laboratory test of this standard Big Bang scenario. The possible alternate scenario of quark-hadron-induced inhomogeneities is also discussed. It is shown that when this alternative scenario is made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density (Omegab) remain approximately the same as in the standard homogeneous case, thus adding to the robustness of the standard model and the conclusion that Omegab approximately 0.06. This latter point is the driving force behind the need for nonbaryonic dark matter (assuming total density Omegatotal = 1) and the need for dark baryonic matter, since the density of visible matter Omegavisible < Omegab. The recent Population II B and Be observations are also discussed and shown to be a consequence of cosmic ray spallation processes rather than primordial nucleosynthesis. The light elements and Nnu successfully probe the cosmological model at times as early as 1 sec and a temperature (T) of approximately 10(10) K (approximately 1 MeV). Thus, they provided the first quantitative arguments that led to the connections of cosmology to nuclear and particle physics. Images Fig. 2 PMID:11607387

  6. Cosmological implications of light element abundances: theory.

    PubMed

    Schramm, D N

    1993-06-01

    Primordial nucleosynthesis provides (with the microwave background radiation) one of the two quantitative experimental tests of the hot Big Bang cosmological model (versus alternative explanations for the observed Hubble expansion). The standard homogeneous-isotropic calculation fits the light element abundances ranging from 1H at 76% and 4He at 24% by mass through 2H and 3He at parts in 105 down to 7Li at parts in 1010. It is also noted how the recent Large Electron Positron Collider (and Stanford Linear Collider) results on the number of neutrinos (Nnu) are a positive laboratory test of this standard Big Bang scenario. The possible alternate scenario of quark-hadron-induced inhomogeneities is also discussed. It is shown that when this alternative scenario is made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density (Omegab) remain approximately the same as in the standard homogeneous case, thus adding to the robustness of the standard model and the conclusion that Omegab approximately 0.06. This latter point is the driving force behind the need for nonbaryonic dark matter (assuming total density Omegatotal = 1) and the need for dark baryonic matter, since the density of visible matter Omegavisible < Omegab. The recent Population II B and Be observations are also discussed and shown to be a consequence of cosmic ray spallation processes rather than primordial nucleosynthesis. The light elements and Nnu successfully probe the cosmological model at times as early as 1 sec and a temperature (T) of approximately 10(10) K (approximately 1 MeV). Thus, they provided the first quantitative arguments that led to the connections of cosmology to nuclear and particle physics.

  7. Solar abundance ratios of the iron-peak elements in the Perseus cluster.

    PubMed

    2017-11-23

    The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae. Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode. Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun, suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, high-resolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment.

  8. Solar abundance ratios of the iron-peak elements in the Perseus cluster

    DOE PAGES

    Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie; ...

    2017-11-13

    The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae1. Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode2–6. Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun, suggesting differences between the nature ofmore » type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here in this paper we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment.« less

  9. Solar abundance ratios of the iron-peak elements in the Perseus cluster

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie

    The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae1. Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode2–6. Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun, suggesting differences between the nature ofmore » type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here in this paper we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment.« less

  10. Globular Cluster Abundances from High-resolution, Integrated-light Spectroscopy. IV. The Large Magellanic Cloud: α, Fe-peak, Light, and Heavy Elements

    NASA Astrophysics Data System (ADS)

    Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott A.; McWilliam, Andrew

    2012-02-01

    We present detailed chemical abundances in eight clusters in the Large Magellanic Cloud (LMC). We measure abundances of 22 elements for clusters spanning a range in age of 0.05-12 Gyr, providing a comprehensive picture of the chemical enrichment and star formation history of the LMC. The abundances were obtained from individual absorption lines using a new method for analysis of high-resolution (R ~ 25,000), integrated-light (IL) spectra of star clusters. This method was developed and presented in Papers I, II, and III of this series. In this paper, we develop an additional IL χ2-minimization spectral synthesis technique to facilitate measurement of weak (~15 mÅ) spectral lines and abundances in low signal-to-noise ratio data (S/N ~ 30). Additionally, we supplement the IL abundance measurements with detailed abundances that we measure for individual stars in the youngest clusters (age < 2 Gyr) in our sample. In both the IL and stellar abundances we find evolution of [α/Fe] with [Fe/H] and age. Fe-peak abundance ratios are similar to those in the Milky Way (MW), with the exception of [Cu/Fe] and [Mn/Fe], which are sub-solar at high metallicities. The heavy elements Ba, La, Nd, Sm, and Eu are significantly enhanced in the youngest clusters. Also, the heavy to light s-process ratio is elevated relative to the MW ([Ba/Y] >+0.5) and increases with decreasing age, indicating a strong contribution of low-metallicity asymptotic giant branch star ejecta to the interstellar medium throughout the later history of the LMC. We also find a correlation of IL Na and Al abundances with cluster mass in the sense that more massive, older clusters are enriched in the light elements Na and Al with respect to Fe, which implies that these clusters harbor star-to-star abundance variations as is common in the MW. Lower mass, intermediate-age, and young clusters have Na and Al abundances that are lower and more consistent with LMC field stars. Our results can be used to constrain both

  11. The interstellar abundances of tin and four other heavy elements

    NASA Technical Reports Server (NTRS)

    Hobbs, L. M.; Welty, D. E.; Morton, D. C.; Spitzer, L.; York, D. G.

    1993-01-01

    Spectra recorded at 1150-1600 A with an instrumental resolution near 16 km/s were obtained with the Goddard High-Resolution Spectrograph on board the HST. The gaseous interstellar abundances of five heavy elements along the light paths to 23 Ori, 15 Mon, 1 Sco, Pi Sco, and Pi Aqr were determined from the observations. The 1400.450 A line of Sn II was detected and identified toward three stars; at Z = 50, tin is the first element from the fifth row of the periodic table to be identified in the interstellar medium. One spectral line of each of Cu II (Z = 29) and Ga II (Z = 31), three lines of Ge II (Z = 32), and two lines of Kr I (Z = 36) were also detected toward some or all of the five stars. The depletions of these five heavy elements generally decrease monotonically with increasing atomic number toward each of the six stars, and tin is generally undepleted within the observational errors. The depletions of 26 elements from the interstellar gas in an average dense interstellar cloud appear to correlate with the elemental 'nebular' condensation temperatures more closely than with the first ionization potentials.

  12. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron Capture Abundance Gradients

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia M. L.; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

    2017-01-01

    The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity, and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron-capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

  13. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron CaptureAbundance Gradients

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

    2017-06-01

    The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

  14. On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions

    NASA Technical Reports Server (NTRS)

    Simpson, Janet P.; Rubin, Robert H.; Colgan, Sean W. J.; Erickson, Edwin F.; Haas, Michael R.

    2004-01-01

    Although abundance gradients in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in G333.6-0.2 with the Kuiper Airborne Observatory and reobserved the central position with the Infrared Space Observatory's Long Wavelength Spectrometer in far-infrared lines of S++, N++, N+, and O++. We also added the N+ lines at 122 and 205 microns to the suite of lines measured in W43 by Simpson et al.. The measured electron densities range from approx. 40 to over 4000 per cu cm in a single HII region, indicating that abundance analyses must consider density variations, since the critical densities of the observed lines range from 40 to 9000 per cu cm. We propose a method to handle density variations and make new estimates of the S/H and N/H abundance ratios. We find that our sulfur abundance estimates for G333.6-0.2 and W43 agree with the S/H abundance ratios expected for the gradient previously reported by Simpson et al., with the S/H values revised to be smaller owing to changes in collisional excitation cross sections. The estimated N/H, S/H, and N/S ratios are the most reliable because of their small corrections for unseen ionization states (< or approx. 10%). The estimated N/S ratios for the two sources are smaller than what would be calculated from the N/H and S/H ratios in our previous paper. If all low excitation H II regions had similar changes to their N/S ratios as a result of adding measurements of N+ to previous measurements of N++, there would be no or only a very small gradient in N/S. This is interesting because nitrogen is considered to be a secondary element and sulfur is a primary element in galactic chemical evolution calculations. We compute models of the two H II regions to estimate corrections for the other

  15. Developing ISM Dust Grain Models with Precision Elemental Abundances from IXO

    NASA Technical Reports Server (NTRS)

    Valencic, L. A.; Smith, R. K.; Juet, A.

    2009-01-01

    The exact nature of interstellar dust grains in the Galaxy remains mysterious, despite their ubiquity. Many viable models exist, based on available IR-UV data and assumed elemental abundances. However, the abundances, which are perhaps the most stringent constraint, are not well known: modelers must use proxies in the absence of direct measurements for the diffuse interstellar medium (ISM). Recent revisions of these proxy values have only added to confusion over which is the best representative for the diffuse ISM, and highlighted the need for direct, high signal-to-noise measurements from the ISM itself. The International X-ray Observatory's superior facilities will enable high-precision elemental abundance measurements. We ill show how these results will measure both the overall ISM abundances and challenge dust models, allowing us to construct a more realistic picture of the ISM.

  16. High-resolution abundance analysis of HD 140283

    NASA Astrophysics Data System (ADS)

    Siqueira-Mello, C.; Andrievsky, S. M.; Barbuy, B.; Spite, M.; Spite, F.; Korotin, S. A.

    2015-12-01

    Context. HD 140283 is a reference subgiant that is metal poor and confirmed to be a very old star. The element abundances of this type of old star can constrain the nature and nucleosynthesis processes that occurred in its (even older) progenitors. The present study may shed light on nucleosynthesis processes yielding heavy elements early in the Galaxy. Aims: A detailed analysis of a high-quality spectrum is carried out, with the intent of providing a reference on stellar lines and abundances of a very old, metal-poor subgiant. We aim to derive abundances from most available and measurable spectral lines. Methods: The analysis is carried out using high-resolution (R = 81 000) and high signal-to-noise ratio (800 <S/N/pixel < 3400) spectrum, in the wavelength range 3700 <λ(Å) < 10475, obtained with a seven-hour exposure time, using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) at the Canada-France-Hawaii Telescope (CFHT). The calculations in local thermodynamic equilibrium (LTE) were performed with a OSMARCS 1D atmospheric model and the spectrum synthesis code Turbospectrum, while the analysis in non-LTE (NLTE) is based on the MULTI code. We present LTE abundances for 26 elements, and NLTE calculations for the species C i, O i, Na i, Mg i, Al i, K i, Ca i, Sr ii, and Ba ii lines. Results: The abundance analysis provided an extensive line list suitable for metal-poor subgiant stars. The results for Li, CNO, α-, and iron peak elements are in good agreement with literature. The newly NLTE Ba abundance, along with a NLTE Eu correction and a 3D Ba correction from literature, leads to [Eu/Ba] = + 0.59 ± 0.18. This result confirms a dominant r-process contribution, possibly together with a very small contribution from the main s-process, to the neutron-capture elements in HD 140283. Overabundances of the lighter heavy elements and the high abundances derived for Ba, La, and Ce favour the operation of the weak r-process in HD 140283

  17. Elemental Abundances of Ultra-Heavy Galactic Cosmic Rays from the SuperTIGER Instrument

    NASA Astrophysics Data System (ADS)

    Murphy, Ryan

    2016-07-01

    The SuperTIGER (Trans-Iron Galactic Element Recorder) experiment was launched on a long-duration balloon flight from Williams Field, Antarctica, on December 8, 2012. The instrument measured the relative elemental abundances of Galactic Cosmic Rays (GCR) for charge (Z) Z>10 with excellent charge resolution, displaying well resolved individual element peaks for 10 ≤ Z ≤ 40. During its record-breaking 55-day flight, SuperTIGER collected ˜4.73 x10^{6} Iron nuclei, ˜8 times as many as detected by its predecessor, TIGER, with charge resolution at iron of 0.17 cu. SuperTIGER measures charge (Z) and energy (E) using a combination of three scintillator and two Cherenkov detectors, and employs a scintillating fiber hodoscope for event trajectory determination. The SuperTIGER data have been analyzed to correct for instrument effects and remove events that underwent nuclear interactions within the instrument. The data include more than 600 events in the charge range 30 < Z ≤ 40. SuperTIGER is the first experiment to resolve elemental abundances of every element in this charge range with high statistics and single-element resolution. The relative abundances of the galactic cosmic ray source have been derived from the measured relative elemental abundances using atmospheric and interstellar propagations. The SuperTIGER measured abundances are generally consistent with previous experimental results from TIGER and ACE-CRIS, with improved statistical precision. The SuperTIGER results confirm the earlier results from TIGER, supporting a model of cosmic-ray origin in OB associations, with preferential acceleration of refractory elements over volatile elements ordered by atomic mass (A). A second SuperTIGER Antarctic flight is planned for December 2017. Details of the instrument, flight, data analysis, and ongoing preparations will be presented.

  18. HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance

    NASA Astrophysics Data System (ADS)

    Wakeford, Hannah R.; Sing, David K.; Kataria, Tiffany; Deming, Drake; Nikolov, Nikolay; Lopez, Eric D.; Tremblin, Pascal; Amundsen, David S.; Lewis, Nikole K.; Mandell, Avi M.; Fortney, Jonathan J.; Knutson, Heather; Benneke, Björn; Evans, Thomas M.

    2017-05-01

    A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted a detailed atmospheric study of the transiting Neptune-mass exoplanet HAT-P-26b. We detected prominent H2O absorption bands with a maximum base-to-peak amplitude of 525 parts per million in the transmission spectrum. Using the water abundance as a proxy for metallicity, we measured HAT-P-26b’s atmospheric heavy element content (4.8-4.0+21.5 times solar). This likely indicates that HAT-P-26b’s atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime, with little contamination from metal-rich planetesimals.

  19. Light, alpha, and Fe-peak element abundances in the galactic bulge

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

    2014-10-01

    We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l, b) = (+5.25,–3.02) and (0,–12). The (+5.25,–3.02) field also includes observations of the bulge globular cluster NGC 6553. The results are based on high-resolution (R ∼ 20,000), high signal-to-noise ration (S/N ≳ 70) FLAMES-GIRAFFE spectra obtained through the European Southern Observatory archive. However, we only selected a subset of the original observations that included spectra with both high S/N and that did notmore » show strong TiO absorption bands. This work extends previous analyses of this data set beyond Fe and the α-elements Mg, Si, Ca, and Ti. While we find reasonable agreement with past work, the data presented here indicate that the bulge may exhibit a different chemical composition than the local thick disk, especially at [Fe/H] ≳ –0.5. In particular, the bulge [α/Fe] ratios may remain enhanced to a slightly higher [Fe/H] than the thick disk, and the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe]) trends between the bulge and local disk may be different at low and high metallicity. We also find that the velocity dispersion decreases as a function of increasing [Fe/H] for both fields, and do not detect any significant cold, high-velocity populations. A comparison with chemical enrichment models indicates that a significant fraction of hypernovae may be required to explain the bulge abundance trends, and that initial mass functions that are steep, top-heavy (and do not include strong outflow), or truncated to avoid including contributions from stars >40 M {sub ☉} are ruled out, in particular because of disagreement with the Fe-peak abundance data. For most elements, the NGC 6553 stars exhibit abundance trends nearly identical to comparable metallicity bulge

  20. Ionization ratios and elemental abundances in the atmosphere of 68 Tauri

    NASA Astrophysics Data System (ADS)

    Aouina, A.; Monier, R.

    2017-12-01

    We have derived the ionization ratios of twelve elements in the atmosphere of the star 68 Tauri (HD 27962) using an ATLAS9 model atmosphere with 72 layers computed for the effective temperature and surface gravity of the star. We then computed a grid of synthetic spectra generated by SYNSPEC49 based on an ATLAS9 model atmosphere in order to model one high resolution spectrum secured by one of us (RM) with the échelle spectrograph SOPHIE at Observatoire de Haute Provence. We could determine the abundances of several elements in their dominant ionization stage, including those defining the Am phenomenon. We thus provide new abundance determinations for 68 Tauri using updated accurate atomic data retrieved from the NIST database which extend previous abundance works.

  1. CAMSS: A spectroscopic survey of meteoroid elemental abundances

    NASA Astrophysics Data System (ADS)

    Jenniskens, P.; Gural, P.; Berdeu, A.

    2014-07-01

    The main element abundances (Mg, Fe, Na, ...) of some Near Earth Objects can be measured by meteor spectroscopy. The Cameras for All-sky Meteor Surveillance (CAMS) Spectrograph project aims to scale up meteor spectroscopy in the same way as CAMS scaled up the measurement of precise meteoroid trajectories from multi-station video observations. Spectra are recorded with sixteen low-light video cameras, each equipped with a high 1379 lines/mm objective transmission grating. The cameras are operated in survey mode and have recorded spectra in the San Francisco Bay Area every clear night since March 12, 2013. An interactive software tool is being developed to calibrate the wavelength alignments projected on the focal plane and extract the meteor spectra. Because the meteoroid trajectory and pre-atmospheric orbit are also independently measured, the absolute abundances of elements in the meteoroid plasma can be calculated as a function of altitude, while the orbital information can tie the meteoroid back to its parent object. % 2007AdSpR..39..538A Berezhnoy, A. A., Borovička, J. 2012, ACM 2012, Abstract 6142 1993A&A...279..627B 1994A&AS..103...83B 2005Icar..174...15B 2011pimo.conf...28G Gural, P. S. 2012, M&PS, 47, 1405 1997ApJ...479..441J 2007AdSpR..39..491J 2011Icar..216...40J Gomez, N., Madiedo, J. M., & Trigo-Rodriguez, J. M. 2013, 44th LPSC, Abstract 1239 2007AdSpR..39..513K 2004AJ....128.2564M 2007AdSpR..39..583R 2007AdSpR..39..517T 2011A&A...526A.126W

  2. Probabilisitc Geobiological Classification Using Elemental Abundance Distributions and Lossless Image Compression in Recent and Modern Organisms

    NASA Technical Reports Server (NTRS)

    Storrie-Lombardi, Michael C.; Hoover, Richard B.

    2005-01-01

    Last year we presented techniques for the detection of fossils during robotic missions to Mars using both structural and chemical signatures[Storrie-Lombardi and Hoover, 2004]. Analyses included lossless compression of photographic images to estimate the relative complexity of a putative fossil compared to the rock matrix [Corsetti and Storrie-Lombardi, 2003] and elemental abundance distributions to provide mineralogical classification of the rock matrix [Storrie-Lombardi and Fisk, 2004]. We presented a classification strategy employing two exploratory classification algorithms (Principal Component Analysis and Hierarchical Cluster Analysis) and non-linear stochastic neural network to produce a Bayesian estimate of classification accuracy. We now present an extension of our previous experiments exploring putative fossil forms morphologically resembling cyanobacteria discovered in the Orgueil meteorite. Elemental abundances (C6, N7, O8, Na11, Mg12, Ai13, Si14, P15, S16, Cl17, K19, Ca20, Fe26) obtained for both extant cyanobacteria and fossil trilobites produce signatures readily distinguishing them from meteorite targets. When compared to elemental abundance signatures for extant cyanobacteria Orgueil structures exhibit decreased abundances for C6, N7, Na11, All3, P15, Cl17, K19, Ca20 and increases in Mg12, S16, Fe26. Diatoms and silicified portions of cyanobacterial sheaths exhibiting high levels of silicon and correspondingly low levels of carbon cluster more closely with terrestrial fossils than with extant cyanobacteria. Compression indices verify that variations in random and redundant textural patterns between perceived forms and the background matrix contribute significantly to morphological visual identification. The results provide a quantitative probabilistic methodology for discriminating putatitive fossils from the surrounding rock matrix and &om extant organisms using both structural and chemical information. The techniques described appear applicable

  3. Do s-Process Enhanced Planetary Nebulae Have Unusual Dust Emission Spectra?

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet; Sellgren, Kris; Sterling, Nicholas

    2006-05-01

    We propose to obtain IRS observations of the mid-infrared dust emission of a sample of Galactic planetary nebulae (PNs) which are known to have enrichments of elements produced in the precursor star by slow neutron-capture nucleosynthesis (the "s-process"). These enhanced abundances result from captures of free neutrons by Fe-peak nuclei following by convective mixing during the AGB; this "third dredge-up" is also responsible for increasing the surface abundance of carbon. Since PNs are the descendants of AGB stars and are often C-rich, it is not surprising that we find substantial enrichments of s-process products such as Ge, Se, and Kr in some PNs. Despite their low initial abundances, 1e-9 to 1e-10 times H, modest enrichments of neutron-capture elements can have observable effects. The spectral type S, a transitional class between O-rich and C-rich AGB stars, is characterized by prominent ZrO bands; Zr is produced in the s-process. We have attempted, without success, to detect gas-phase Zr in PNs. However, Zr is highly refractory. It can condense into ZrO2 or be incorporated into high-temperature rocky condensates in O-rich environments, while in C-rich environments it may form metallic carbides (i.e. ZrC, an analog of TiC). Indeed, Zr-Mo carbide inclusions found in some meteoritic presolar grains are thought to originate in the atmospheres of C-rich AGB stars. Other refractory s-process products (e.g. Sr, Ba) may also be incorporated into grains. High-quality Spitzer spectra of the dust emission in a set of PNs with known s-process enhancements - determined by us from gas-phase measurements of undepleted elements - will be valuable for comparison with laboratory spectroscopy of grain analogs. These comparisons will help determine whether the dredge-up of n-capture products affects the dust chemistry of PNs and may offer some new insights into the dust composition.

  4. Uncertainties in s -process nucleosynthesis in low mass stars determined from Monte Carlo variations

    NASA Astrophysics Data System (ADS)

    Cescutti, G.; Hirschi, R.; Nishimura, N.; den Hartogh, J. W.; Rauscher, T.; Murphy, A. St J.; Cristallo, S.

    2018-05-01

    The main s-process taking place in low mass stars produces about half of the elements heavier than iron. It is therefore very important to determine the importance and impact of nuclear physics uncertainties on this process. We have performed extensive nuclear reaction network calculations using individual and temperature-dependent uncertainties for reactions involving elements heavier than iron, within a Monte Carlo framework. Using this technique, we determined the uncertainty in the main s-process abundance predictions due to nuclear uncertainties link to weak interactions and neutron captures on elements heavier than iron. We also identified the key nuclear reactions dominating these uncertainties. We found that β-decay rate uncertainties affect only a few nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are in general small (less than 50%). Three key reactions, nevertheless, stand out because they significantly affect the uncertainties of a large number of nuclides. These are 56Fe(n,γ), 64Ni(n,γ), and 138Ba(n,γ). We discuss the prospect of reducing uncertainties in the key reactions identified in this study with future experiments.

  5. Trace Element Abundance Measurements on Cosmic Dust Particles

    NASA Technical Reports Server (NTRS)

    Flynn, George

    1996-01-01

    The X-Ray Microprobe on beamline X-26A at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory was used to determine the abundances of elements from Cr through Sr in individual interplanetary dust particles (IDPs) collected from the Earth's stratosphere and the Scanning Transmission X-ray Microscope (STXM) on beamline X-1A at the NSLS was used to determine the carbon abundances and spatial distributions in IDPs. In addition, modeling was performed in an attempt to associate particular types of IDPs with specific types of parent bodies, and thus to infer the chemistry, mineralogy, and structural properties of those parent bodies.

  6. Abundances of the light elements from UV (HST) and red (ESO) spectra in the very old star HD 84937

    NASA Astrophysics Data System (ADS)

    Spite, M.; Peterson, R. C.; Gallagher, A. J.; Barbuy, B.; Spite, F.

    2017-04-01

    Aims: In order to provide a better basis for the study of mechanisms of nucleosynthesis of the light elements beyond hydrogen and helium in the oldest stars, the abundances of C, O, Mg, Si, P, S, K, and Ca have been derived from UV-HST and visible-ESO high resolution spectra in the old, very metal-poor star HD 84937, at a metallicity that is 1/200 that of the Sun's. For this halo main-sequence turnoff star, the abundance determination of P and S are the first published determinations. Methods: The LTE profiles of the lines were computed and fitted to the observed spectra. Wherever possible, we compared the abundances derived from the UV spectrum to abundances derived from the visible or near-infrared spectra, and also corrected the derived abundances for non-LTE effects. Three-dimensional (3D) CO5BOLD model atmospheres have been used to determine the abundances of C and O from molecular CH and OH bands. Results: The abundances of these light elements relative to iron in HD 84937 are found to agree well with the abundances of these elements in classical metal-poor stars. Our HD 84937 carbon abundance determination points toward a solar (or mildly enhanced above solar) value of [C/Fe]. The modest overabundance of the α elements of even atomic number Z, typical of halo turnoff stars, is confirmed in this example. The odd-Z element P is found to be somewhat deficient in HD 84937, at [P/Fe] = -0.32, which is again consistent with the handful of existing determinations for turnoff stars of such low metallicity. We show that the abundance of oxygen, deduced from the OH band from 3D computations, is not compatible with the abundance deduced from the red oxygen triplet. This incompatibility is explained by the existence of a chromosphere heating the shallow layers of the atmosphere where the OH band, in 3D computations, is mainly formed. Conclusions: The abundance ratios are compared to the predictions of models of galactic nucleosynthesis and evolution. Based on

  7. Abundance Analysis of 17 Planetary Nebulae from High-Resolution Optical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sherrard, Cameroun G.; Sterling, Nicholas C.; Dinerstein, Harriet L.; Madonna, Simone; Mashburn, Amanda

    2017-06-01

    We present an abundance analysis of 17 planetary nebulae (PNe) observed with the 2D-coudé echelle spectrograph on the 2.7-m Harlan J. Smith telescope at McDonald Observatory. The spectra cover the wavelength range 3600--10,400 Å at a resolution R = 36,700, and are the first high-resolution optical spectra for many objects in our sample. The number of emission lines detected in individual nebulae range from ~125 to over 600. We derive temperatures, densities, and abundances from collisionally-excited lines using the PyNeb package (Luridiana et al. 2015, A&A, 573, A42) and the ionization correction factor scheme of Delgado-Inglada et al. (2014, MNRAS, 440, 536). The abundances of light elements agree with previous estimates for most of the PNe. Several objects exhibit emission lines of refractory elements such as K and Fe, and neutron-capture elements that can be enriched by the s-process. We find that K and Fe are depleted relative to solar by ~0.3--0.7~dex and 1-2 dex, respectively, and find evidence for s-process enrichments in 10 objects. Several objects in our sample exhibit C, N, and O recombination lines that are useful for abundance determinations. These transitions are used to compute abundance discrepancy factors (ADFs), the ratio of ionic abundances derived from permitted lines to those from collisionally-excited transitions. We explore relations among depletion factors, ADFs, s-process enrichment factors, and other nebular stellar and nebular properties. We acknowledge support from NSF awards AST-901432 and AST-0708429.

  8. Trace Element Abundances in an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

    NASA Technical Reports Server (NTRS)

    Mane, Prajkta; Wadhwa, M.; Keller, L. P.

    2013-01-01

    Calcium-aluminum-rich refractory inclusions (CAIs) are thought to be the first-formed solids in the Solar protoplanetary disk and can provide information about the earliest Solar System processes (e.g., [1]). A hibonite-perovskitebearing CAI from the Allende CV3 chondrite (SHAL, [2]) contains a single of 500 micrometers hibonite grain and coarse-grained perovskite. The mineralogy and oxygen isotopic composition of this CAI shows similarities with FUN inclusions, especially HAL [2]. Here we present trace element abundances in SHAL.

  9. THE CURIOUS CASE OF ELEMENTAL ABUNDANCE DIFFERENCES IN THE DUAL HOT JUPITER HOSTS WASP-94A AND B

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Teske, Johanna K.; Khanal, Sandhya; Ramírez, Ivan, E-mail: jteske@carnegiescience.edu

    Binary stars provide an ideal laboratory for investigating the potential effects of planet formation on stellar composition. Assuming that the stars formed in the same environment/from the same material, any compositional anomalies between binary components might indicate differences in how material was sequestered in planets, or accreted by the star in the process of planet formation. We present here a study of the elemental abundance differences between WASP-94A and B, a pair of stars that each host a hot Jupiter exoplanet. The two stars are very similar in spectral type (F8 and F9), and their ∼2700 au separation suggests that their protoplanetarymore » disks were likely not influenced by stellar interactions, but WASP-94Ab’s orbit—misaligned with the host star spin axis and likely retrograde—points toward a dynamically active formation mechanism, perhaps different from that of WASP-94Bb, which is not misaligned and has a nearly circular orbit. Based on our high-quality spectra and strictly relative abundance analysis, we detect a depletion of volatiles (∼−0.02 dex, on average) and enhancement of refractories (∼0.01 dex) in WASP-94A relative to B (standard errors are ∼0.005 dex). This is different from every other published case of binary host star abundances, in which either no significant abundance differences are reported or there is some degree of enhancement in all elements, including volatiles. Several scenarios that may explain the abundance trend are discussed, but none can be definitively accepted or rejected. Additional high-contrast imaging observations to search for companions that may be dynamically affecting the system, as well as a larger sample of binary host star studies, are needed to better understand the curious abundance trends we observe in WASP-94A and B.« less

  10. High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age

    NASA Astrophysics Data System (ADS)

    Nissen, P. E.

    2016-09-01

    Aims: A previous study of correlations between element abundances and ages of solar twin stars in the solar neighborhood is extended to include Sc, Mn, Cu, and Ba to obtain new information on the nucleosynthetic history of these elements. Methods: HARPS spectra with S/N ≳ 600 are used to derive very precise (σ ~ 0.01 dex) differential abundances of Sc, Mn, Cu, and Ba for 21 solar twins and the Sun. The analysis is based on MARCS model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Stellar ages with internal errors less than 1 Gyr are obtained by interpolation in the log g - Teff diagram between isochrones based on the Aarhus Stellar Evolution Code. Results: For stars younger than 6 Gyr, [Sc/Fe], [Mn/Fe], [Cu/Fe], and [Ba/Fe] are tightly correlated with stellar age, which is also the case for the other elements previously studied; linear relations between [X/Fe] and age have χ^2red ˜ 1, and for most stars the residuals do not depend on elemental condensation temperature. For ages between 6 and 9 Gyr, the [X/Fe] - age correlations break down and the stars split up into two groups having respectively high and low [X/Fe] for the odd-Z elements Na, Al, Sc, and Cu. Conclusions: While stars in the solar neighborhood younger than ~ 6 Gyr were formed from interstellar gas with a smooth chemical evolution, older stars seem to have originated from regions enriched by supernovae with different neutron excesses. Correlations between abundance ratios and stellar age suggest that: (I) Sc is made in Type II supernovae along with the α-capture elements; (II) the Type II to Ia yield ratio is about the same for Mn and Fe; (III) Cu is mainly made by the weak s-process in massive stars; (iv) the Ba/Y yield ratio for asymptotic giant branch stars increases with decreasing stellar mass; (v) [Y/Mg] and [Y/Al] can be used as chemical clocks when determining ages of solar metallicity stars. Based on data products from observations made

  11. Elemental Abundances of Blue Compact Dwarfs from Mid-Infrared Spectroscopy with Spitzer

    NASA Astrophysics Data System (ADS)

    Wu, Yanling; Bernard-Salas, J.; Charmandaris, V.; Lebouteiller, V.; Hao, Lei; Brandl, B. R.; Houck, J. R.

    2008-01-01

    We present a study of elemental abundances in a sample of 13 blue compact dwarf (BCD) galaxies, using the ~10-37 μm high-resolution spectra obtained with Spitzer IRS. We derive the abundances of neon and sulfur for our sample using the infrared fine-structure lines probing regions which may be obscured by dust in the optical and compare our results with similar infrared studies of starburst galaxies from ISO. We find a good correlation between the neon and sulfur abundances, although sulfur is underabundant relative to neon with respect to the solar value. A comparison of the elemental abundances (neon and sulfur) measured from the infrared data with those derived from the optical (neon, sulfur, and oxygen) studies reveals a good overall agreement for sulfur, while the infrared-derived neon abundances are slightly higher than the optical values. This indicates either that the metallicities of dust-enshrouded regions in BCDs are similar to the optically accessible regions, or that if they are different they do not contribute substantially to the total infrared emission of the host galaxy.

  12. Element Abundances in Meteorites and the Earth: Implication for the Accretion of Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Mezger, K.; Vollstaedt, H.; Maltese, A.

    2017-12-01

    Essentially all known inner solar system materials show near chondritic relative abundances of refractory elements and depletion in volatile elements. To a first approximation volatile element depletion correlates with the respective condensation temperature (TC) of the elements. Possible mechanisms for this depletion are incomplete condensation and partial loss by evaporation caused by heating prior to or during the planetesimal accretion. The stable isotope compositions of almost all moderately volatile elements in different meteorite classes show only minor, or no evidence for a Rayleigh-type fractionation that could be attributed to partial condensation or evaporation. The different classes of meteorites also show that the degree of depletion in their parent bodies (i.e. mostly planetesimals) is quite variable, but nevertheless systematic. For primitive and least disturbed carbonaceous chondrites the element depletion pattern is a smooth function of TC. The accessible silicate Earth also shows this general depletion pattern, but in detail it is highly complex and requires differentiation processes that are not solely controlled by TC. If only highly lithophile elements are considered the depletion pattern of the silicate Earth reveals a step function that shows that moderately volatile lithophile elements have abundances that are ca. 0.1 times the chondritic value, irrespective of their TC. This element pattern observed for bulk silicate Earth can be modelled as a mixture of two distinct components: ca. 90% of a strongly reduced planetary body that is depleted in highly volatile elements and ca. 10% of a more volatile element rich and oxidized component. This mixture can account for the apparent Pb- paradox observed in melts derived from the silicate Earth and provides a time constraint for the mixing event, which is ca. 70 My after the beginning of the solar system. This event corresponds to the giant impact that also formed the Moon.

  13. Chemical abundances of primary stars in the Sirius-like binary systems

    NASA Astrophysics Data System (ADS)

    Kong, X. M.; Zhao, G.; Zhao, J. K.; Shi, J. R.; Kumar, Y. Bharat; Wang, L.; Zhang, J. B.; Wang, Y.; Zhou, Y. T.

    2018-05-01

    Study of primary stars lying in Sirius-like systems with various masses of white dwarf (WD) companions and orbital separations is one of the key aspects to understand the origin and nature of barium (Ba) stars. In this paper, based on high-resolution and high-S/N spectra, we present systematic analysis of photospheric abundances for 18 FGK primary stars of Sirius-like systems including six giants and 12 dwarfs. Atmospheric parameters, stellar masses, and abundances of 24 elements (C, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, and Nd) are determined homogeneously. The abundance patterns in these sample stars show that most of the elements in our sample follow the behaviour of field stars with similar metallicity. As expected, s-process elements in four known Ba giants show overabundance. A weak correlation was found between anomalies of s-process elemental abundance and orbital separation, suggesting that the orbital separation of the binaries could not be the main constraint to differentiate strong Ba stars from mild Ba stars. Our study shows that the large mass (>0.51 M⊙) of a WD companion in a binary system is not a sufficient condition to form a Ba star, even if the separation between the two components is small. Although not sufficient, it seems to be a necessary condition since Ba stars with lower mass WDs in the observed sample were not found. Our results support that [s/Fe] and [hs/ls] ratios of Ba stars are anti-correlated with the metallicity. However, the different levels of s-process overabundance among Ba stars may not be dominated mainly by the metallicity.

  14. A history of violence: Insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes and water contents

    NASA Astrophysics Data System (ADS)

    Mahan, Brandon; Moynier, Frédéric; Beck, Pierre; Pringle, Emily A.; Siebert, Julien

    2018-01-01

    Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provide vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomitantly, during post-accretionary shock impact(s).

  15. Reverse engineering nuclear properties from rare earth abundances in the r process

    NASA Astrophysics Data System (ADS)

    Mumpower, M. R.; McLaughlin, G. C.; Surman, R.; Steiner, A. W.

    2017-03-01

    The bulk of the rare earth elements are believed to be synthesized in the rapid neutron capture process or r process of nucleosynthesis. The solar r-process residuals show a small peak in the rare earths around A∼ 160, which is proposed to be formed dynamically during the end phase of the r process by a pileup of material. This abundance feature is of particular importance as it is sensitive to both the nuclear physics inputs and the astrophysical conditions of the main r process. We explore the formation of the rare earth peak from the perspective of an inverse problem, using Monte Carlo studies of nuclear masses to investigate the unknown nuclear properties required to best match rare earth abundance sector of the solar isotopic residuals. When nuclear masses are changed, we recalculate the relevant β-decay properties and neutron capture rates in the rare earth region. The feedback provided by this observational constraint allows for the reverse engineering of nuclear properties far from stability where no experimental information exists. We investigate a range of astrophysical conditions with this method and show how these lead to different predictions in the nuclear properties influential to the formation of the rare earth peak. We conclude that targeted experimental campaigns in this region will help to resolve the type of conditions responsible for the production of the rare earth nuclei, and will provide new insights into the longstanding problem of the astrophysical site(s) of the r process.

  16. The Abundances of the Iron Group Elements in Early B Stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Peters, C.

    FUSE observations of four sharp-lined early B main-sequence band stars in the Magellanic Clouds will be carried through to determine the abundances of the heavy elements, especially those of the Fe group. The FUSE spectral region contains numerous Fe III lines, including the resonance multiplet (UV1) near 1130 A that is excellent for abundance determinations and two strong multiplets of V III, an ion that does not produce measurable lines longward of 1200 A in metal-deficient stars. In addition there are several measurable lines from Cr III and Mn III. Although abundances of the Fe-peak elements are of interest because they are important for assessing opacities for stellar evolution calculations and the validity of theoretical calculations of explosive nucleosynthesis, ground-based studies do not yield this information because measurable lines from these species, except for a few Fe III lines, are found only in the UV spectral region. The abundances of heavy elements provide information on the production of such elements in previous generations of stars. From FUSE data obtained in Cycle 3 we are determining the abundances of the Fe group elements in two sharp-lined early B stars in the SMC (AV 304, a field star, and NGC346-637, a star in a mini-starburst cluster). This project will allow one to compare the abundances in AV 304 and NGC346-637 with those in the LMC and other regions in the SMC and look for asymmetry in heavy element production in the Magellanic Clouds.

  17. Disk Evolution, Element Abundances and Cloud Properties of Young Gas Giant Planets

    PubMed Central

    Helling, Christiane; Woitke, Peter; Rimmer, Paul B.; Kamp, Inga; Thi, Wing-Fai; Meijerink, Rowin

    2014-01-01

    We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. ProDiMo protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The Drift cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models. PMID:25370190

  18. Disk evolution, element abundances and cloud properties of young gas giant planets.

    PubMed

    Helling, Christiane; Woitke, Peter; Rimmer, Paul B; Kamp, Inga; Thi, Wing-Fai; Meijerink, Rowin

    2014-04-14

    We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. PRODIMO protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The DRIFT cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models.

  19. Formation of Apollo 16 impactites and the composition of late accreted material: Constraints from Os isotopes, highly siderophile elements and sulfur abundances

    NASA Astrophysics Data System (ADS)

    Gleißner, Philipp; Becker, Harry

    2017-03-01

    Fe-Ni metal-schreibersite-troilite intergrowths in Apollo 16 impact melt rocks and new highly siderophile element (HSE) and S abundance data indicate that millimeter-scale closed-system fractional crystallization processes during cooling of impactor-derived metal melt droplets in impact-melts are the main reason for compositional variations and strong differences in abundances and ratios of HSE in multiple aliquots from Apollo 16 impact melt rocks. Element ratios obtained from linear regression of such data are therefore prone to error, but weighted averages take into account full element budgets in the samples and thus represent a more accurate estimate of their impactor contributions. Modeling of solid metal-liquid metal partitioning in the Fe-Ni-S-P system and HSE patterns in impactites from different landing sites suggest that bulk compositions of ancient lunar impactites should be representative of impact melt compositions and that large-scale fractionation of the HSE by in situ segregation of solid metal or sulfide liquid in impact melt sheets most likely did not occur. The compositional record of lunar impactites indicates accretion of variable amounts of chondritic and non-chondritic impactor material and the mixing of these components during remelting of earlier ejecta deposits. The non-chondritic composition appears most prominently in some Apollo 16 impactites and is characterized by suprachondritic HSE/Ir ratios which increase from refractory to moderately volatile HSE and exhibit a characteristic enrichment of Ru relative to Pt. Large-scale fractional crystallization of solid metal from sulfur and phosphorous rich metallic melt with high P/S in planetesimal or embryo cores is currently the most likely process that may have produced these compositions. Similar materials or processes may have contributed to the HSE signature of the bulk silicate Earth (BSE).

  20. Element abundances at high redshift

    NASA Technical Reports Server (NTRS)

    Meyer, David M.; Welty, D. E.; York, D. G.

    1989-01-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe(_), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value.

  1. Inhomogeneous chemical evolution of r-process elements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wehmeyer, B., E-mail: benjamin.wehmeyer@unibas.ch; Thielemann, F.-K.; Pignatari, M.

    2016-06-21

    We report the results of a galactic chemical evolution (GCE) study for r-process- and alpha elements. For this work, we used the inhomogeneous GCE model ”ICE”, which allows to keep track of the galactic abundances of elements produced by different astrophysical sites. The main input parameters for this study were: a) The Neutron Star Merger (NSM) coalescence time scale, the probability of NSMs, and for the sub-class of ”magneto-rotationally driven Supernovae” (”Jet-SNe”), their occurence rate in comparison to ”standard” Supernovae (SNe).

  2. Elemental and isotopic abundances in the solar wind

    NASA Technical Reports Server (NTRS)

    Geiss, J.

    1972-01-01

    The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

  3. Determination of the calcium elemental abundance for 43 flares from SMM-XRP solar X-ray spectra

    NASA Astrophysics Data System (ADS)

    Lemen, J. R.; Sylwester, J.; Bentley, R. D.

    The helium and lithium-like X-ray transitions of Ca XVIII-XIX have been used to make an absolute measurement of the coronal calcium elemental abundance relative to hydrogen (ACa) in solar flares. Cooling phase spectra of 43 flares obtained in channel 1 of the Bent Crystal Spectrometer on the Solar Maximum Mission have been analyzed. The abundance is determined from the intensity ratio of the Ca XIX resonance line (1S0 - 1P1) and nearby continuum. Attempts to correlate the ACa measurements with other observable features are discussed.

  4. Superheavy elements and r-process

    NASA Astrophysics Data System (ADS)

    Panov, I. V.; Korneev, I. Yu.; Thielemann, F.-K.

    2009-06-01

    The probability for the production of superheavy elements in the astrophysical r-process is discussed. The dependence of the estimated superheavy-element yields on input data is estimated. Preliminary calculations revealed that the superheavy-element yields at the instant of completion of the r-process may be commensurate with the uranium yield, but the former depend strongly on the models used to forecast the properties of beta-delayed, neutron-induced, and spontaneous fission. This study is dedicated to the 80th anniversary of V.S. Imshennik’s birth.

  5. Rhenium-osmium isotope and highly-siderophile-element abundance systematics of angrite meteorites

    NASA Astrophysics Data System (ADS)

    Riches, Amy J. V.; Day, James M. D.; Walker, Richard J.; Simonetti, Antonio; Liu, Yang; Neal, Clive R.; Taylor, Lawrence A.

    2012-11-01

    Coupled 187Os/188Os compositions and highly-siderophile-element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for eight angrite achondrite meteorites that include quenched- and slowly-cooled textural types. These data are combined with new major- and trace-element concentrations determined for bulk-rock powder fractions and constituent mineral phases, to assess angrite petrogenesis. Angrite meteorites span a wide-range of HSE abundances from <0.005 ppb Os (e.g., Northwest Africa [NWA] 1296; Angra dos Reis) to >100 ppb Os (NWA 4931). Chondritic to supra-chondritic 187Os/188Os (0.1201-0.2127) measured for Angra dos Reis and quenched-angrites correspond to inter- and intra-sample heterogeneities in Re/Os and HSE abundances. Quenched-angrites have chondritic-relative rare-earth-element (REE) abundances at 10-15×CI-chondrite, and their Os-isotope and HSE abundance variations represent mixtures of pristine uncontaminated crustal materials that experienced addition (<0.8%) of exogenous chondritic materials during or after crystallization. Slowly-cooled angrites (NWA 4590 and NWA 4801) have fractionated REE-patterns, chondritic to sub-chondritic 187Os/188Os (0.1056-0.1195), as well as low-Re/Os (0.03-0.13), Pd/Os (0.071-0.946), and relatively low-Pt/Os (0.792-2.640). Sub-chondritic 187Os/188Os compositions in NWA 4590 and NWA 4801 are unusual amongst planetary basalts, and their HSE and REE characteristics may be linked to melting of mantle sources that witnessed prior basaltic melt depletion. Angrite HSE-Yb systematics suggest that the HSE behaved moderately-incompatibly during angrite magma crystallization, implying the presence of metal in the crystallizing assemblage. The new HSE abundance and 187Os/188Os compositions indicate that the silicate mantle of the angrite parent body(ies) (APB) had HSE abundances in chondritic-relative proportions but at variable abundances at the time of angrite crystallization. The HSE systematics of angrites are

  6. Elemental Abundance Distributions in Basalt Clays and Meteorites: Is It a Biosignature?

    NASA Technical Reports Server (NTRS)

    Fisk, M. R.; Storrie-Lombardi, M. C.; Joseph, J.

    2005-01-01

    Volcanic glass altered by microorganisms exhibits distinctive textures differing significantly from abiotic alteration [1-4]. We have previously presented morphological evidence of bioweathering in sub-oceanic basalt glass [5] and olivine [6], and noted similar alterations in Nakhla [7]. We have also introduced an autonomous Bayesian probabilistic classification methodology to identify biotic and abiotic alteration in sub-oceanic basalts using elemental abundance data [8]. We now present data from multiple sub-oceanic sites addressing the more general question of utilizing elemental abundance distribution in clays as a valid biosignature for the exploration of putative clay alteration products in meteorites.

  7. Rare earth element abundances in rocks and minerals from the Fiskenaesset Complex, West Greenland. [comparison with lunar anorthosites

    NASA Technical Reports Server (NTRS)

    Henderson, P.; Fishlock, S. J.; Laul, J. C.; Cooper, T. D.; Conard, R. L.; Boynton, W. V.; Schmitt, R. A.

    1976-01-01

    The paper reports activation-analysis determinations of rare-earth-element (REE) and other trace-element concentrations in selected rocks, plagioclase, and mafic separates from the Fiskenaesset Complex. The REE abundances are found to be very low and atypical in comparison with other terrestrial anorthosites. The plagioclases are shown to be characterized by a deficiency in heavy RE elements relative to light ones and a positive Eu anomaly, while the mafic separates are enriched in heavy rare earths and have no Eu anomaly, except in one sample. It is found that the bulk and trace-element abundances of the plagioclases are similar to those observed in some lunar anorthosites, but the degree of Eu anomaly is less in the plagioclases. The data are taken as confirmation of the idea that fractionation processes were involved in the origin of the Complex, and it is concluded that the Complex may have been produced from a magma generated by partial melting of a garnet-bearing source.

  8. Identifying Type Ia Supernova Mechanisms in Dwarf Spheroidal Galaxies through Analysis of Iron-peak Elemental Abundances

    NASA Astrophysics Data System (ADS)

    Guo, Rachel; Xie, Justin Long; Kirby, Evan N.

    2017-01-01

    Through the fusion of nucleons to produce elements heavier than hydrogen and helium, stellar nucleosynthesis produces most of the elements in the universe. Such is the case in a supernova explosion, which creates most of the elements on the periodic table—including iron-peak elements, atomic numbers 21 through 30—through nucleosynthesis and ejects them into the interstellar medium. In this study, we determine the best theoretical supernova model appropriate for the stars in the dwarf spheroidal galaxies Sculptor, Fornax, Ursa Minor, and Leo II by calculating the abundances of iron-peak elements in these stars. To determine iron-peak elemental abundances, we compare synthesized spectra with observed spectra from medium-resolution spectroscopy and determine the best-fitting spectrum by way of a chi-squared minimization. Through inspecting the relationship between the iron-peak element abundances and the abundance of iron itself and by comparing them to previously hypothesized supernova model theories, we discover that the near-Chandrasekhar mass “n1” model, as predicted by Seitenzahl et al., most accurately represents the trends and patterns within our data, presenting new insight into Type Ia supernovae mechanisms within the Milky Way and beyond.

  9. On the differences in element abundances of energetic ions from corotating events and from large solar events

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Richardson, I. G.; Barbier, L. M.

    1991-01-01

    The abundances of energetic ions accelerated from high-speed solar wind streams by shock waves formed at corotating interaction regions (CIRs) where high-speed streams overtake the lower-speed solar wind are examined. The observed element abundances appear to represent those of the high-speed solar wind, unmodified by the shock acceleration. These abundances, relative to those in the solar photosphere, are organized by the first ionization potential (FIP) of the ions in a way that is different from the FIP effect commonly used to describe differences between abundances in the solar photosphere and those in the solar corona, solar energetic particles (SEPs), and the low-speed solar wind. In contrast, the FIP effect of the ion abundances in the CIR events is characterized by a smaller amplitude of the differences between high-FIP and low-FIP ions and by elevated abundances of He, C, and S.

  10. Search for white dwarf companions of cool stars with peculiar element abundances

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, E.

    1984-01-01

    A search for a white dwarf companions of cool stars with peculiar element abundances was undertaken. One additional star the xi Cet, was found with a white dwarf companion. It was found that HR 1016, 56Uma, 16 Ser, have high excitation emission lines which indicate a high temperature object in the system. It is suggested that since these indications for high temperature companions were seen for all nearby Ba stars, it is highly probable that all Ba stars have white dwarf companions, and that the peculiar element abundances seen in the Ba stars are due to mass transfer. Observations, arguments and conclusions are presented. White dwarf companions were not found. Together with the Li and Be abundances and the chromospheric emission line spectra in these stars were studied. No white dwarf companions were seen for subgiant CH stars.

  11. Early chemo-dynamical evolution of dwarf galaxies deduced from enrichment of r-process elements

    NASA Astrophysics Data System (ADS)

    Hirai, Yutaka; Ishimaru, Yuhri; Saitoh, Takayuki R.; Fujii, Michiko S.; Hidaka, Jun; Kajino, Toshitaka

    2017-04-01

    The abundance of elements synthesized by the rapid neutron-capture process (r-process elements) of extremely metal-poor (EMP) stars in the Local Group galaxies gives us clues to clarify the early evolutionary history of the Milky Way halo. The Local Group dwarf galaxies would have similarly evolved with building blocks of the Milky Way halo. However, how the chemo-dynamical evolution of the building blocks affects the abundance of r-process elements is not yet clear. In this paper, we perform a series of simulations using dwarf galaxy models with various dynamical times and total mass, which determine star formation histories. We find that galaxies with dynamical times longer than 100 Myr have star formation rates less than 10-3 M⊙ yr-1 and slowly enrich metals in their early phase. These galaxies can explain the observed large scatters of r-process abundance in EMP stars in the Milky Way halo regardless of their total mass. On the other hand, the first neutron star merger appears at a higher metallicity in galaxies with a dynamical time shorter than typical neutron star merger times. The scatters of r-process elements mainly come from the inhomogeneity of the metals in the interstellar medium whereas the scatters of α-elements are mostly due to the difference in the yield of each supernova. Our results demonstrate that the future observations of r-process elements in EMP stars will be able to constrain the early chemo-dynamical evolution of the Local Group galaxies.

  12. Reverse engineering nuclear properties from rare earth abundances in the r process

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mumpower, Matthew Ryan; McLaughlin, G. C.; Surman, R.

    The bulk of the rare earth elements are believed to be synthesized in the rapid neutron capture process or r process of nucleosynthesis. The solar r-process residuals show a small peak in the rare earths aroundmore » $$A\\sim 160$$, which is proposed to be formed dynamically during the end phase of the r process by a pileup of material. This abundance feature is of particular importance as it is sensitive to both the nuclear physics inputs and the astrophysical conditions of the main r process. Here, we explore the formation of the rare earth peak from the perspective of an inverse problem, using Monte Carlo studies of nuclear masses to investigate the unknown nuclear properties required to best match rare earth abundance sector of the solar isotopic residuals. When nuclear masses are changed, we recalculate the relevant β-decay properties and neutron capture rates in the rare earth region. The feedback provided by this observational constraint allows for the reverse engineering of nuclear properties far from stability where no experimental information exists. We investigate a range of astrophysical conditions with this method and show how these lead to different predictions in the nuclear properties influential to the formation of the rare earth peak. Finally, we conclude that targeted experimental campaigns in this region will help to resolve the type of conditions responsible for the production of the rare earth nuclei, and will provide new insights into the longstanding problem of the astrophysical site(s) of the r process.« less

  13. Reverse engineering nuclear properties from rare earth abundances in the r process

    DOE PAGES

    Mumpower, Matthew Ryan; McLaughlin, G. C.; Surman, R.; ...

    2017-02-01

    The bulk of the rare earth elements are believed to be synthesized in the rapid neutron capture process or r process of nucleosynthesis. The solar r-process residuals show a small peak in the rare earths aroundmore » $$A\\sim 160$$, which is proposed to be formed dynamically during the end phase of the r process by a pileup of material. This abundance feature is of particular importance as it is sensitive to both the nuclear physics inputs and the astrophysical conditions of the main r process. Here, we explore the formation of the rare earth peak from the perspective of an inverse problem, using Monte Carlo studies of nuclear masses to investigate the unknown nuclear properties required to best match rare earth abundance sector of the solar isotopic residuals. When nuclear masses are changed, we recalculate the relevant β-decay properties and neutron capture rates in the rare earth region. The feedback provided by this observational constraint allows for the reverse engineering of nuclear properties far from stability where no experimental information exists. We investigate a range of astrophysical conditions with this method and show how these lead to different predictions in the nuclear properties influential to the formation of the rare earth peak. Finally, we conclude that targeted experimental campaigns in this region will help to resolve the type of conditions responsible for the production of the rare earth nuclei, and will provide new insights into the longstanding problem of the astrophysical site(s) of the r process.« less

  14. DETECTION OF ELEMENTS AT ALL THREE r-PROCESS PEAKS IN THE METAL-POOR STAR HD 160617

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roederer, Ian U.; Lawler, James E., E-mail: iur@obs.carnegiescience.edu, E-mail: jelawler@wisc.edu

    2012-05-01

    We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundancesmore » or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.« less

  15. Elemental abundance analyses with DAO spectrograms: XXXII. HR 6455 (A3 III), δ Aqr (A3 V), η Lep (F2 V), and 1 Boo (A1 V)

    NASA Astrophysics Data System (ADS)

    Yüce, K.; Adelman, S. J.; Gulliver, A. F.; Hill, G.

    2011-08-01

    We examine the sharp-lined stars HR 6455 (A3 III, v sin i = 8.7 km s-1) and η Lep (F2 V, v sin i = 13.5 km s-1) as well as δ Aqr (A3 V, v sin i = 81 km s-1) and 1 Boo (A1 V, v sin i = 59 km s-1) to increase the number consistently analyzed A and F stars using high dispersion and high S/N (≥200) spectrograms obtained with CCD detectors at the long Coudé camera of the 1.22-m telescope of the Dominion Astrophysical Observatory. Such studies contribute to understanding systematic abundance differences between normal and non-magnetic main-sequence band chemically peculiar A and early F stars. LTE fine analyses of HR 6455, δ Aqr, and 1 Boo using Kurucz's ATLAS suite programs show the same general elemental abundance trends with differences in the metal richness. Light and iron-peak element abundances are generally solar or overabundant while heavy element and rare earth element abundances are overabundant. HR 6455 is an evolved Am star while δ Aqr and 1 Boo show the phenomenon to different extents. Most derived abundances of η Lep are solar. Table 3 is available at the CDS via http://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/AN/332/681

  16. Meteoritic Constraints on Models of the Solar Nebula: The Abundances of Moderately Volatile Elements

    NASA Technical Reports Server (NTRS)

    Cassen, Patrick; Cuzzi, Jeff (Technical Monitor)

    1994-01-01

    The "moderately volatile" elements are those which condense (or evaporate) in the temperature range 650 - 1350 K, as a mix of material with solar abundances is cooled (or heated) tinder equilibrium conditions. Their relative abundances in chondritic meteorites are solar (or "cosmic", as defined by the composition of Cl meteorites) to within a factor of several, but vary within that range in a way that correlates remarkably well with condensation temperature, independent of chemical affinity. It has been argued that this correlation reflects a systematically selective process which favored the accretion of refractory material over volatile material from a cooling nebula. Wasson and Chou (Meteoritics 9, 69-94, 1974, and Wasson and co-authors in subsequent papers) suggested that condensation and settling of solids contemporaneously with the cooling and removal of nebular gas could produce the observed abundance patterns, but a quantitative model has been lacking. We show that the abundance patterns of the moderately volatile elements in chondritic meteorites can be produced, in some degree of quantitative detail, by models of the solar nebula that are designed to conform to observations of T Tauri stars and the global conservation laws. For example, even if the local surface density of the nebula is not decreasing, condensation and accretion of solids from radially inflowing gas in a cooling nebula can result in depletions of volatiles, relative to refractories, like those observed, The details of the calculated abundance patterns depend on (but are not especially sensitive to) model parameters, and can exhibit the variations that distinguish the meteorite classes. Thus it appears that nebula characteristics such as cooling rates, radial flow velocities, and particle accumulation rates can be quantitatively constrained by demanding that they conform to meteoritic data; and the models, in turn, can produce testable hypotheses regarding the time and location of the

  17. Stellar abundances and ages for metal-rich Milky Way globular clusters. Stellar parameters and elemental abundances for 9 HB stars in NGC 6352

    NASA Astrophysics Data System (ADS)

    Feltzing, S.; Primas, F.; Johnson, R. A.

    2009-01-01

    Context: Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. Additionally, Rosenberg et al. identified a small group of metal-rich globular clusters that appeared to be about 2 billion years younger than the bulk of the Milky Way globular clusters. However, it is unclear if like is compared with like in this dataset as we do not know the enhancement of α-elements in the clusters and the amount of α-elements is well known to influence the derivation of ages for globular clusters. Aims: We derive elemental abundances for the metal-rich globular cluster NGC 6352 and we present our methods to be used in up-coming studies of other metal-rich globular clusters. Methods: We present a study of elemental abundances for α- and iron-peak elements for nine HB stars in the metal-rich globular cluster NGC 6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with the UVES spectrograph on VLT. The elemental abundances have been derived using standard LTE calculations and stellar parameters have been derived from the spectra themselves by requiring ionizational as well as excitational equilibrium. Results: We find that NGC 6352 has [Fe/H] = -0.55, is enhanced in the α-elements to about +0.2 dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V) = 0.24 and (m-M) ≃ 14.05 better fits the data than the nominal values. An investigation of log gf-values for suitable Fe i lines lead us to the conclusion that the commonly used correction to the May et al. (1974) data should not be

  18. High-resolution mapping of elemental abundances of the lunar regolith

    NASA Astrophysics Data System (ADS)

    Wöhler, Christian; Berezhnoy, Alexey; Evans, Richard

    Many attempts have been made to derive elemental abundances of the lunar surface from mul-tispectral images (cf. e.g. [1]). The gamma ray spectrometer on board the Lunar Prospector spacecraft (LP GRS) provided the first "direct" global measurements of lunar elemental abun-dances including Fe, Th (15 km surface resolution), Ti, K, Sm (60 km), Al, O, Si, Mg, Ca, and U (150 km). In this study we rely on the elemental abundance estimation method intro-duced in [2], which is based on spectral features derived from the Clementine UVVIS+NIR data set and estimates the abundances of Ca, Al, Fe, Mg, Ti, and O by applying a second order polynomial regression model with the corresponding LP GRS abundances as "ground truth". The regarded spectral features are the continuum slope, the FWHM of the ferrous absorption trough near 1000 nm after continuum division, and the absorption wavelengths and relative absorption depths (cf. [2,3] for details). A petrographic analysis is performed based on the abundances of the key elements Al, Fe, and Mg [4]. The relative abundances of the endmem-bers mare basalt, Mg-rich rock, and ferroan anorthosite are estimated using Fe-Mg and Al-Mg diagrams, where the endmember compositions are determined based on the three-endmember plane fitted in Al-Fe-Mg space to the elemental abundances at 150 km resolution obtained with the regression model. The root-mean-square deviation from the three-endmember plane is only 0.3 wt percent. Our petrographic map shows Mg-rich rocks in the Mare Frigoris region, on the edges of large maria, in the South Pole Aitken basin, and in some cryptomaria such as the Schiller-Schickard basin. The presence of Mg-rich rocks in Mare Frigoris explains the Fe and Ti depletion discussed in [5]. Furthermore, our analysis confirms that the basalts of eastern mare Frigoris have an atypically high Al content [6]. The region south of Lichtenberg and around Seleucus and Briggs in northwestern Oceanus Procellarum is characterised by

  19. An elemental abundance analysis of the superficially normal A star Vega

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Gulliver, Austin F.

    1990-01-01

    An elemental abundance analysis of Vega has been performed using high-signal-to-noise 2.4 A/mm Reticon observations of the region 4313-4809 A. Vega is found to be a metal-poor star with a mean underabundance of 0.60 dex. The He/H ratio of 0.03 as derived from He I 4472 A suggests that the superficial helium convection zone has disappeared and that radiative diffusion is producing the photospheric abundance anomalies.

  20. Temperature and Gravity Dependence of Trace Element Abundances in Hot DA White Dwarfs (94-EUVE-094)

    NASA Technical Reports Server (NTRS)

    Finley, David S.

    1998-01-01

    EUV spectroscopy has shown that DA white dwarfs hotter than about 45,000 K may contain trace heavy elements, while those hotter than about 50,000 K almost always have significant abundances of trace heavy elements. One of our continuing challenges is to identify and determine the abundances of these trace constituents, and then to relate the observed abundance patterns to the present conditions and previous evolutionary histories of the hot DA white dwarfs.

  1. Trace elements as quantitative probes of differentiation processes in planetary interiors

    NASA Technical Reports Server (NTRS)

    Drake, M. J.

    1980-01-01

    The characteristic trace element signature that each mineral in the source region imparts on the magma constitutes the conceptual basis for trace element modeling. It is shown that abundances of trace elements in extrusive igneous rocks may be used as petrological and geochemical probes of the source regions of the rocks if differentiation processes, partition coefficients, phase equilibria, and initial concentrations in the source region are known. Although compatible and incompatible trace elements are useful in modeling, the present review focuses primarily on examples involving the rare-earth elements.

  2. CONSTRAINTS ON THE FORMATION OF THE GALACTIC BULGE FROM Na, Al, AND HEAVY-ELEMENT ABUNDANCES IN PLAUT's FIELD

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

    2012-04-20

    We report chemical abundances of Na, Al, Zr, La, Nd, and Eu for 39 red giant branch (RGB) stars and 23 potential inner disk red clump stars located in Plaut's low-extinction window. We also measure lithium for a super Li-rich RGB star. The abundances were determined by spectrum synthesis of high-resolution (R Almost-Equal-To 25,000), high signal-to-noise (S/N {approx} 50-100 pixel{sup -1}) spectra obtained with the Blanco 4 m telescope and Hydra multifiber spectrograph. For the bulge RGB stars, we find a general increase in the [Na/Fe] and [Na/Al] ratios with increasing metallicity, and a similar decrease in [La/Fe] and [Nd/Fe].more » Additionally, the [Al/Fe] and [Eu/Fe] abundance trends almost identically follow those of the {alpha}-elements, and the [Zr/Fe] ratios exhibit relatively little change with [Fe/H]. The consistently low [La/Eu] ratios of the RGB stars indicate that at least a majority of bulge stars formed rapidly ({approx}<1 Gyr) and before the main s-process could become a significant pollution source. In contrast, we find that the potential inner disk clump stars exhibit abundance patterns more similar to those of the thin and thick disks. Comparisons between the abundance trends at different bulge locations suggest that the inner and outer bulges formed on similar timescales. However, we find evidence of some abundance differences between the most metal-poor and metal-rich stars in various bulge fields. The data also indicate that the halo may have had a more significant impact on the outer bulge initial composition than the inner bulge composition. The [Na/Fe], and to a lesser extent [La/Fe], abundances further indicate that the metal-poor bulge, at least at {approx}1 kpc from the Galactic center, and thick disk may not share an identical chemistry.« less

  3. The superTIGER instrument: Measurement of elemental abundances of ultra-heavy galactic cosmic rays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Binns, W. R.; Bose, R. G.; Braun, D. L.

    2014-06-10

    The SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was developed to measure the abundances of galactic cosmic-ray elements from {sub 10}Ne to {sub 40}Zr with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 < Z ≤ 60 and measures the energy spectra of the more abundant elements for Z ≤ 30 from about 0.8 to 10 GeV/nucleon. This instrument is an enlarged and higher resolution version of the earlier TIGER instrument. It was designed to provide the largest geometric acceptance possible andmore » to reach as high an altitude as possible, flying on a standard long-duration 1.11 million m{sup 3} balloon. SuperTIGER was launched from Williams Field, McMurdo Station, Antarctica, on 2012 December 8, and made about 2.7 revolutions around the South Pole in 55 days of flight, returning data on over 50 × 10{sup 6} cosmic-ray nuclei with Z ≥ 10, including ∼1300 with Z > 29 and ∼60 with Z > 49. Here, we describe the instrument, the methods of charge identification employed, the SuperTIGER balloon flight, and the instrument performance.« less

  4. THE SuperTIGER Instrument: Measurement of Elemental Abundances of Ultra-Heavy Galactic Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Bose, R. G.; Braun, D. L.; Brandt, T. J.; Daniels, W. M.; DowKonnt, P. F.; Fitzsimmons, S. P.; Hahne, D. J.; Hams, T.; Israel, M. H.; hide

    2014-01-01

    The SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was developed to measure the abundances of galactic cosmic-ray elements from Ne-10 to Zr-40 with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 < Z < or = 60 and measures the energy spectra of the more abundant elements for Z < or = 30 from about 0.8 to 10 GeV/nucleon. This instrument is an enlarged and higher resolution version of the earlier TIGER instrument. It was designed to provide the largest geometric acceptance possible and to reach as high an altitude as possible, flying on a standard long-duration 1.11 million cu m balloon. SuperTIGER was launched from Williams Field, McMurdo Station, Antarctica, on 2012 December 8, and made about 2.7 revolutions around the South Pole in 55 days of flight, returning data on over 50 x 10(exp 6) cosmic-ray nuclei with Z > or = 10, including approx.1300 with Z > 29 and approx.60 with Z > 49. Here, we describe the instrument, the methods of charge identification employed, the SuperTIGER balloon flight, and the instrument performance.

  5. From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different r-process Sites

    NASA Astrophysics Data System (ADS)

    Ji, Alexander P.; Frebel, Anna

    2018-04-01

    The ultra-faint dwarf galaxy Reticulum II was enriched by a rare and prolific r-process event, such as a neutron star merger (NSM). To investigate the nature of this event, we present high-resolution Magellan/MIKE spectroscopy of the brightest star in this galaxy. The high signal-to-noise allows us to determine the abundances of 41 elements, including the radioactive actinide element Th and first ever detections of third r-process peak elements (Os and Ir) in a star outside the Milky Way. The observed neutron-capture element abundances closely match the solar r-process component, except for the first r-process peak, which is significantly lower than solar but matches other r-process enhanced stars. The ratio of the first peak to heavier r-process elements implies that the r-process site produces roughly equal masses of high and low electron fraction ejecta, within a factor of 2. We compare the detailed abundance pattern to predictions from nucleosynthesis calculations of NSMs and magnetorotationally driven jet supernovae, finding that nuclear physics uncertainties dominate over astrophysical uncertainties. We measure {log}{{Th/Eu}}=-0.84+/- 0.06 ({stat})+/- 0.22 ({sys}), somewhat lower than all previous Th/Eu observations. The youngest age we derive from this ratio is 21.7 ± 2.8 (stat) ± 10.3 (sys) Gyr, indicating that current initial production ratios do not describe the r-process event in Reticulum II. The abundances of light elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. They may eventually provide a way to distinguish between NSMs and magnetorotationally driven jet supernovae, but this would require more detailed knowledge of the chemical evolution of Reticulum II. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  6. The Abundances of the Fe Group Elements in Early B Stars in the Magellanic Clouds and Bridge

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.; Adelman, Saul J.

    2016-01-01

    The abundances of three Fe Group elements (V, Cr, and Fe) in 9 early main-sequence band B stars in the LMC, 7 in the SMC , and two in the Magellanic Bridge have been determined from archival FUSE observations and the Hubeny/Lanz NLTE programs TLUSTY/SYNSPEC. Lines from the Fe group elements, except for a few weak multiplets of Fe III, are not observable in the optical spectral region. The best set of lines in the FUSE spectral region are Fe III (UV1), V III 1150 Å, and Cr III 1137 Å. The abundances of these elements in early B stars are a marker for recent SNe Ia activity, as a single exploding white dwarf can deliver 0.5 solar masses of Ni-56 that decays into Fe to the ISM. The Fe group abundances in an older population of stars primarily reflect SNe II activity, in which a single explosion delivers only 0.07 solar masses of Ni-56 to the ISM (the rest remains trapped in the neutron star). The abundances of the Fe group elements in early B stars not only track SNe Ia activity but are also important for computing evolutionary tracks for massive stars. In general, the Fe abundance relative to the sun's value is comparable to the mean abundances for the lighter elements in the Clouds/Bridge but the values of [V,Cr/Fe]sun are smaller. This presentation will discuss the spatial distribution of the Fe Group elements in the Magellanic Clouds, and compare it with our galaxy in which the abundance of Fe declines with radial distance from the center. Support from NASA grants NAG5-13212, NNX10AD66G, STScI HST-GO-13346.22, and USC's Women in Science and Engineering (WiSE) program is greatly appreciated.

  7. Atomic Data for Nebular Abundance Determinations: Photoionization and Recombination Properties of Xenon Ions

    NASA Astrophysics Data System (ADS)

    Sterling, Nicholas C.; Kerlin, Austin B.

    2016-01-01

    We present preliminary results of a study of the photoionization (PI) and recombination properties of low-charge Xe ions. The abundances of neutron(n)-capture elements (atomic number Z > 30) are of interest in planetary nebulae (PNe) since they can be enriched by slow n-capture nucleosynthesis (the ``s-process'') in the progenitor asymptotic giant branch (AGB) stars. Xe is particularly valuable, because it is the most widely-observed ``heavy-s'' species (Z > 40) in PNe. Its abundance relative to lighter n-capture elements can be used to determine s-process neutron exposures, and constrain s-process enrichment patterns as a function of progenitor metallicity. Using the atomic structure code AUTOSTRUCTURE (Badnell 2011, Comp. Phys. Comm., 182, 1528), we have computed multi-configuration Breit-Pauli distorted-wave PI cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for neutral through six-times ionized Xe, data which are critically needed for accurate Xe abundance determinations in ionized nebulae. We find good agreement between our computed direct PI cross sections and experimental measurements. Internal uncertainties are estimated for our calculations by using three different configuration interaction expansions for each ion, and by testing the sensitivity of our results to the radial orbital scaling parameters. As found for other n-capture elements (Sterling & Witthoeft 2011, A&A, 529, A147; Sterling 2011, A&A, 533, A62), DR is the dominant recombination mechanism for Xe ions at nebular temperatures (~104 K). Following Sterling et al. (2015, ApJS, 218, 25), these data will be added to nebular modeling codes to compute ionization correction factors for unobserved Xe ions in PNe, which will enable elemental Xe abundances to be determined with much higher accuracy than is currently possible. This work is supported by NSF award AST-1412928.

  8. Project VeSElkA: a search for the vertical stratification of element abundances in HD 157087

    NASA Astrophysics Data System (ADS)

    Khalack, V.

    2018-06-01

    The new spectropolarimetric spectra of HD 157087 obtained recently with ESPaDOnS (Echelle SpectroPolarimetric Device for Observations of Stars) at the Canada-France-Hawaii Telescope are analysed to verify the nature of this object. The fundamental stellar parameters Teff = 8882 K, log g = 3.57 were obtained for HD 157087 from the analysis of nine Balmer line profiles in two available spectra. A comparison of the results of our abundance analysis with previously published data shows a variability of the average abundance with time for some chemical species, while the abundances of other elements remain almost constant. The abundance analysis also reveals evidence of a significant abundance increase towards the deeper atmospheric layers for C, S, Ca, Sc, V, Cr, Mn, Co, Ni and Zr. Together with the discovered enhanced abundance of Ca and Sc, this finding contradicts the classification of HD 157087 as a marginal Am star. An analysis of the available measurements of radial velocity revealed long- and short-period variations. The long-period variation supports the idea that HD 157087 is an astrometric binary system with a period longer than 6 yr. The presence of the short-period variation of Vr, as well as the detection of the temporal variation of the average abundance, suggests that HD 157087 may be a triple system, in which a short-period binary rotates around a third star. In this case, the short-period binary may consist of slowly rotating Am and A (or Ap with a weak magnetic field) stars that have similar effective temperatures and surface gravities, but different abundance peculiarities.

  9. Galactic Abundance Patterns via Peimbert Types I & II Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Milingo, J. B.; Barnes, K. L.; Kwitter, K. B.; Souza, S. P.; Henry, R. B. C.; Skinner, J. N.

    2005-12-01

    Planetary Nebulae (PNe) are well known fonts of information about both stellar evolution and galactic chemical evolution. Abundance patterns in PNe are used to note signatures and constraints of nuclear processing, and as tracers of the distribution of metals throughout galaxies. In this poster abundance gradients and heavy element ratios are presented based upon newly acquired spectrophotometry of a sample of Galactic Peimbert Type I PNe. This new data set is extracted from spectra that extend from λ 3600 - 9600Å allowing the use of [S III] features at λ 9069 and 9532Å. Since a significant portion of S in PNe resides in S+2 and higher ionization stages, including these features improves the extrapolation from observed ion abundances to total element abundance. An alternate metallicity tracer, Sulfur is precluded from enhancement and depletion across the range of PNe progenitor masses. Its stability in intermediate mass stars makes it a useful tool to probe the natal conditions as well as the evolution of PNe progenitors. This is a continuation of our Type II PNe work, the impetus being to compile a relatively large set of line strengths and abundances with internally consistent observation, reduction, calibration, and abundance determination, minimizing systematic affects that come from compiling various data sets. This research is supported by the AAS Small Research Grants program, the Franklin & Marshall Committee on Grants, and NSF grant AST-0307118.

  10. Element Abundance Ratios in the Quiet Sun Transition Region

    NASA Astrophysics Data System (ADS)

    Young, P. R.

    2018-03-01

    Element abundance ratios of magnesium to neon (Mg/Ne) and neon to oxygen (Ne/O) in the transition region of the quiet Sun have been derived by re-assessing previously published data from the Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory in the light of new atomic data. The quiet Sun Mg/Ne ratio is important for assessing the effect of magnetic activity on the mechanism of the first ionization potential (FIP) effect, while the Ne/O ratio can be used to infer the solar photospheric abundance of neon, which cannot be measured directly. The average Mg/Ne ratio is found to be 0.52 ± 0.11, which applies over the temperature region 0.2–0.7 MK, and is consistent with the earlier study. The Ne/O ratio is, however, about 40% larger, taking the value 0.24 ± 0.05 that applies to the temperature range 0.08–0.40 MK. The increase is mostly due to changes in ionization and recombination rates that affect the equilibrium ionization balance. If the Ne/O ratio is interpreted as reflecting the photospheric ratio, then the photospheric neon abundance is 8.08 ± 0.09 or 8.15 ± 0.10 (on a logarithmic scale for which hydrogen is 12), according to whether the oxygen abundances of M. Asplund et al. or E. Caffau et al. are used. The updated photospheric neon abundance implies a Mg/Ne FIP bias for the quiet Sun of 1.6 ± 0.6.

  11. Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances.

    PubMed

    Bishop, Janice L; Englert, Peter A J; Patel, Shital; Tirsch, Daniela; Roy, Alex J; Koeberl, Christian; Böttger, Ute; Hanke, Franziska; Jaumann, Ralf

    2014-12-13

    Surface sediments at Lakes Fryxell, Vanda and Brownworth in the Antarctic Dry Valleys (ADV) were investigated as analogues for the cold, dry environment on Mars. Sediments were sampled from regions surrounding the lakes and from the ice cover on top of the lakes. The ADV sediments were studied using Raman spectra of individual grains and reflectance spectra of bulk particulate samples and compared with previous analyses of subsurface and lakebottom sediments. Elemental abundances were coordinated with the spectral data in order to assess trends in sediment alteration. The surface sediments in this study were compared with lakebottom sediments (Bishop JL et al. 2003 Int. J. Astrobiol. 2, 273-287 (doi:10.1017/S1473550403001654)) and samples from soil pits (Englert P et al. 2013 In European Planetary Science Congress, abstract no. 96; Englert P et al. 2014 In 45th Lunar and Planetary Science Conf., abstract no. 1707). Feldspar, quartz and pyroxene are common minerals found in all the sediments. Minor abundances of carbonate, chlorite, actinolite and allophane are also found in the surface sediments, and are similar to minerals found in greater abundance in the lakebottom sediments. Surface sediment formation is dominated by physical processes; a few centimetres below the surface chemical alteration sets in, whereas lakebottom sediments experience biomineralization. Characterizing the mineralogical variations in these samples provides insights into the alteration processes occurring in the ADV and supports understanding alteration in the cold and dry environment on Mars. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  12. X-shooter spectroscopy of young stellar objects in Lupus. Lithium, iron, and barium elemental abundances

    NASA Astrophysics Data System (ADS)

    Biazzo, K.; Frasca, A.; Alcalá, J. M.; Zusi, M.; Covino, E.; Randich, S.; Esposito, M.; Manara, C. F.; Antoniucci, S.; Nisini, B.; Rigliaco, E.; Getman, F.

    2017-09-01

    Aims: With the purpose of performing a homogeneous determination of elemental abundances for members of the Lupus T association, we analyzed three chemical elements: lithium, iron, and barium. The aims were: 1) to derive the lithium abundance for the almost complete sample ( 90%) of known class II stars in the Lupus I, II, III, and IV clouds; 2) to perform chemical tagging of a region where few iron abundance measurements have been obtained in the past, and no determination of the barium content has been done up to now. We also investigated possible barium enhancement at the very young age of the region, as this element has become increasingly interesting in the last few years following the evidence of barium over-abundance in young clusters, the origin of which is still unknown. Methods: Using the X-shooter spectrograph mounted on the Unit 2 (UT2) at the Very Large Telescope (VLT), we analyzed the spectra of 89 cluster members, both class II (82) and class III (7) stars. We measured the strength of the lithium line at λ6707.8 Å and derived the abundance of this element through equivalent width measurements and curves of growth. For six class II stars we also derived the iron and barium abundances using the spectral synthesis method and the code MOOG. The veiling contribution was taken into account in the abundance analysis for all three elements. Results: We find a dispersion in the strength of the lithium line at low effective temperatures and identify three targets with severe Li depletion. The nuclear age inferred for these highly lithium-depleted stars is around 15 Myr, which exceeds by an order of magnitude the isochronal one. We derive a nearly solar metallicity for the members whose spectra could be analyzed. We find that Ba is over-abundant by 0.7 dex with respect to the Sun. Since current theoretical models cannot reproduce this abundance pattern, we investigated whether this unusually large Ba content might be related to effects due to stellar

  13. R-process Element Cosmic Rays from Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Komiya, Yutaka; Shigeyama, Toshikazu

    2017-09-01

    Neutron star mergers (NSMs) are one of the most plausible sources of r-process elements in the universe. Therefore, NSMs can also be a major source of ultra-heavy elements in cosmic rays. In this paper, we first estimate the contribution of r-process elements synthesized in NSMs to the ultra-heavy element cosmic rays (UHCRs) by calculating transport equations that take into account energy loss processes and spallations. We show that the flux of UHCRs accelerated by the NSMs themselves fluctuates by many orders of magnitude on a timescale of several million years and can overwhelm UHCRs accelerated by supernova remnants (SNRs) after an NSM takes place within a few kiloparsec from the solar system. Experiments with very long exposure times using meteorites as UHCR detectors can detect this fluctuation. As a consequence, we show that if NSMs are the primary source of UHCRs, future experiments using meteorites may be able to reveal the event history of NSMs in the solar vicinity. We also describe a possible difference in the abundance pattern and energy spectrum of UHCRs between NSM and SNR accelerations.

  14. THE INTERMEDIATE NEUTRON-CAPTURE PROCESS AND CARBON-ENHANCED METAL-POOR STARS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hampel, Melanie; Stancliffe, Richard J.; Lugaro, Maria

    Carbon-enhanced metal-poor (CEMP) stars in the Galactic Halo display enrichments in heavy elements associated with either the s (slow) or the r (rapid) neutron-capture process (e.g., barium and europium, respectively), and in some cases they display evidence of both. The abundance patterns of these CEMP- s / r stars, which show both Ba and Eu enrichment, are particularly puzzling, since the s and the r processes require neutron densities that are more than ten orders of magnitude apart and, hence, are thought to occur in very different stellar sites with very different physical conditions. We investigate whether the abundance patternsmore » of CEMP- s / r stars can arise from the nucleosynthesis of the intermediate neutron-capture process (the i process), which is characterized by neutron densities between those of the s and the r processes. Using nuclear network calculations, we study neutron capture nucleosynthesis at different constant neutron densities n ranging from 10{sup 7}–10{sup 15} cm{sup -3}. With respect to the classical s process resulting from neutron densities on the lowest side of this range, neutron densities on the highest side result in abundance patterns, which show an increased production of heavy s -process and r -process elements, but similar abundances of the light s -process elements. Such high values of n may occur in the thermal pulses of asymptotic giant branch stars due to proton ingestion episodes. Comparison to the surface abundances of 20 CEMP- s / r stars shows that our modeled i -process abundances successfully reproduce observed abundance patterns, which could not be previously explained by s -process nucleosynthesis. Because the i -process models fit the abundances of CEMP- s / r stars so well, we propose that this class should be renamed as CEMP- i .« less

  15. Genesis of the heaviest elements in the Milky Way Galaxy.

    PubMed

    Sneden, Christopher; Cowan, John J

    2003-01-03

    We review the origin and evolution of the heavy elements, those with atomic numbers greater than 30, in the early history of the Milky Way. There is a large star-to-star bulk scatter in the concentrations of heavy elements with respect to the lighter metals, which suggests an early chemically unmixed and inhomogeneous Galaxy. The relative abundance patterns among the heavy elements are often very different from the solar system mix, revealing the characteristics of the first element donors in the Galaxy. Abundance comparisons among several halo stars show that the heaviest neutron-capture elements (including barium and heavier) are consistent with a scaled solar system rapid neutron-capture abundance distribution, whereas the lighter such elements do not conform to the solar pattern. The stellar abundances indicate an increasing contribution from the slow neutron-capture process (s-process) at higher metallicities in the Galaxy. The detection of thorium in halo and globular cluster stars offers a promising, independent age-dating technique that can put lower limits on the age of the Galaxy.

  16. Application of the Calculating Formula for the Mean Neutron Exposure in CEPM-s and CEPM-r/s Stars %Kstars: AGB and post-AGB, nuclear reactions, nucleosynthesis, abundances, methods: analytical

    NASA Astrophysics Data System (ADS)

    Zhang, F. H.; Zhang, L.; Cui, W. Y.; Zhang, B.

    2017-09-01

    Recent studies have shown that, for the current s-process nucleosynthesis model for the low-mass asymptotic giant branch (AGB) stars with (13C) pocket radiative burning during the interpulse period, the neutron exposure distribution in the nucleosynthesis region can be regarded as an exponential function, and the relation between the mean neutron exposure (τ0) and the model parameters is τ0 = - Δ τ/ln [q/(1 - r + q)]), in which (Δ τ) is the exposure value of each neutron irradiation, (r) is the overlap factor, and (q) is the mass ratio of the (13C) shell to the He intershell. Using the published data resulted from fitting the observed abundances of neutron-capture elements in 20 CEMP (Carbon-Enhanced Metal-Poor)-s and CEMP-s/r stars with the parametric AGB stellar s-process model, the reliability of the derived formula is tested, and further more the application of the formula in the s-process nucleosynthesis study is explored preliminarily. Our results show that, under the radiative s-process nucleosynthesis mechanism, the formula is suitable for CEMP stars experiencing recurrent neutron exposures. Combined with the parametric AGB nucleosynthesis model, the formula could be regarded as an effective tool to screen the CEMP stars with a single neutron exposure or a special type. Considering the uncertainty of the (13C) pocket, the role of this formula in understanding the physical conditions necessary to reproduce the observed s-process abundances in CEMP stars needs further study.

  17. Elemental and Molecular Relative Abundances in the Ejecta of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Kober, G. V.; Gull, T. R.; Nielsen, K.; Bruhweiler, F.; Verner, K.; Stahl, O.; Weis, K.; Bomans, D.

    2006-01-01

    We are measuring relative elemental abundances for the ejecta in the line of sight from Eta Carinae using high dispersion spectroscopy with the HST/STIS and the VLT/UVES. While multiple velocity components have been identified, we focus on the -513 and -146 km/s components originating from the Homunculus and the Little Homunculus. Complicating factors are the complex nebular structures in the immediate vicinity of the bright, massive star: the very bright emission structures, Weigelt blobs B, C and D, the broad, clumpy structures of the extended wind apparently not photoionized by Eta Car B, and general scattered starlight from the extended wind and the dusty core of the circumstellar material. We have used the 3050 to 3160A region of overlap between STIS and UVES to intercompare equivalent widths of absorption lines to estimate the 'contributing factor', namely the amount of light originating from the star compared to nebular structures. While the extracted STIS spectra are from 0.1" wide aperture, the UVES spectra are limited by the 1" seeing conditions. Curiously we find that the scattering contribution in the UVES spectra changes with time, apparently with orbital phase of the 5.54-year period. This indicates that the dust may be modified by changes in the central source with phase. The noticeable drop in scattered light appears to occur about 1.7 years (phase 0.35) after the spectroscopic minimum. Relative abundances of iron peak elements and some molecules will be estimated. Observations in this study were accomplished with HST through STSci and with VLT through ESO and funded under STIS GTO resources.

  18. Probing the Site for r-Process Nucleosynthesis with Abundances of Barium and Magnesium in Extremely Metal-poor Stars.

    PubMed

    Tsujimoto; Shigeyama; Yoshii

    2000-03-01

    We suggest that if the astrophysical site for r-process nucleosynthesis in the early Galaxy is confined to a narrow mass range of Type II supernova (SN II) progenitors, with a lower mass limit of Mms=20 M middle dot in circle, a unique feature in the observed distribution of [Ba/Mg] versus [Mg/H] for extremely metal-poor stars can be adequately reproduced. We associate this feature, a bifurcation of the observed elemental ratios into two branches in the Mg abundance interval -3.7processes. The first branch, which we call the y-branch, is associated with the production of Ba and Mg from individual massive supernovae. The derived mass of Ba synthesized in SNe II is 8.5x10-6 M middle dot in circle for Mms=20 M middle dot in circle and 4.5x10-8 M middle dot in circle for Mms=25 M middle dot in circle. We conclude that SNe II with Mms approximately 20 M middle dot in circle are the dominant source of r-process nucleosynthesis in the early Galaxy. An SN-induced chemical evolution model with this Mms-dependent Ba yield creates the y-branch, reflecting the different nucleosynthesis yields of [Ba/Mg] for each SN II with Mms greater, similar20 M middle dot in circle. The second branch, which we call the i-branch, is associated with the elemental abundance ratios of stars which were formed in the dense shells of the interstellar medium swept up by SNe II with Mms<20 M middle dot in circle that do not synthesize r-process elements, and it applies to stars with observed Mg abundances in the range &sqbl0;Mg&solm0;H&sqbr0;<-2.7. The Ba abundances in these stars reflect those of the interstellar gas at the (later) time of their formation. The existence of a [Ba/Mg] i-branch strongly suggests that SNe II that are associated with stars of progenitor mass Mmsprocess elements. We predict the existence of this i-branch for other r-process elements, such as

  19. s-Process in low metallicity Pb stars.

    NASA Astrophysics Data System (ADS)

    Bisterzo, S.; Gallino, R.; Straniero, O.; Ivans, I. I.; Käppeler, F.; Aoki, W.

    We consider a sample of very metal-poor, C-rich, s-rich and lead-rich stars observed at high-resolution spectroscopy, and some recent spectroscopic data of C+s-rich stars obtained at moderate resolution. The spectroscopic data of these stars are interpreted with AGB theoretical models of different 13C-pocket efficiencies, initial mass and initial r-enrichment. When lead is not measured we give our theoretical prediction. The observed stars are not on the AGB phase, but are main sequence or giant stars. They acquired the C and s enrichments by mass transfer in a close binary system from the more massive companion while on the AGB (now a white dwarf). A considerable fraction of the stars show both high s and r enrichments. To explain the s+r enriched stars we assume a parental cloud already enriched in r-elements. The measurement of Nb is an indicator of an extrinsic AGB in a binary system. The intrinsic indicator [hs/ls] constrains the initial mass, while [Pb/hs] and [Pb/ls] are a measure of the s-process efficiency. The apparent discrepancies of C and N abundances may be reconciled by assuming a strong cool bottom process occurring during the AGB. An important primary production of light elements, from Ne to Si, increasing with the star mass, is predicted for AGB models at very low metallicity, induced by n capture on primary 22Ne and its progenies.

  20. Trace element abundances of high-MgO glasses from Kilauea, Mauna Loa and Haleakala volcanoes, Hawaii

    USGS Publications Warehouse

    Wagner, T.P.; Clague, D.A.; Hauri, E.H.; Grove, T.L.

    1998-01-01

    We performed an ion-microprobe study of eleven high-MgO (6.7-14.8 wt%) tholeiite glasses from the Hawaiian volcanoes Kilauea, Mauna Loa and Haleakala. We determined the rare earth (RE), high field strength, and other selected trace element abundances of these glasses, and used the data to establish their relationship to typical Hawaiian shield tholeiite and to infer characteristics of their source. The glasses have trace element abundance characteristics generally similar to those of typical shield tholeiites, e.g. L(light)REE/H(heavy)REE(C1) > 1. The Kilauea and Mauna Loa glasses, however, display trace and major element characteristics that cross geochemical discriminants observed between Kilauea and Mauna Loa shield lavas. The glasses contain a blend of these discriminating chemical characteristics, and are not exactly like the typical shield lavas from either volcano. The production of these hybrid magmas likely requires a complexly zoned source, rather than two unique sources. When corrected for olivine fractionation, the glass data show correlations between CaO concentration and incompatible trace element abundances, indicating that CaO may behave incompatibly during melting of the tholeiite source. Furthermore, the tholeiite source must contain residual garnet and clinopyroxene to account for the variation in trace element abundances of the Kilauea glasses. Inversion modeling indicates that the Kilauea source is flat relative to C1 chondrites, and has a higher bulk distribution coefficient for the HREE than the LREE.

  1. The Origin of r-process Elements in the Milky Way

    NASA Astrophysics Data System (ADS)

    Côté, Benoit; Fryer, Chris L.; Belczynski, Krzysztof; Korobkin, Oleg; Chruślińska, Martyna; Vassh, Nicole; Mumpower, Matthew R.; Lippuner, Jonas; Sprouse, Trevor M.; Surman, Rebecca; Wollaeger, Ryan

    2018-03-01

    Some of the heavy elements, such as gold and europium (Eu), are almost exclusively formed by the rapid neutron capture process (r-process). However, it is still unclear which astrophysical site between core-collapse supernovae and neutron star–neutron star (NS–NS) mergers produced most of the r-process elements in the universe. Galactic chemical evolution (GCE) models can test these scenarios by quantifying the frequency and yields required to reproduce the amount of europium (Eu) observed in galaxies. Although NS–NS mergers have become popular candidates, their required frequency (or rate) needs to be consistent with that obtained from gravitational wave measurements. Here, we address the first NS–NS merger detected by LIGO/Virgo (GW170817) and its associated gamma-ray burst and analyze their implication for the origin of r-process elements. The range of NS–NS merger rate densities of 320–4740 Gpc‑3 yr‑1 provided by LIGO/Virgo is remarkably consistent with the range required by GCE to explain the Eu abundances in the Milky Way with NS–NS mergers, assuming the solar r-process abundance pattern for the ejecta. Under the same assumption, this event has produced about 1–5 Earth masses of Eu, and 3–13 Earth masses of gold. When using theoretical calculations to derive Eu yields, constraining the role of NS–NS mergers becomes more challenging because of nuclear astrophysics uncertainties. This is the first study that directly combines nuclear physics uncertainties with GCE calculations. If GW170817 is a representative event, NS–NS mergers can produce Eu in sufficient amounts and are likely to be the main r-process site.

  2. R -process Element Cosmic Rays from Neutron Star Mergers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Komiya, Yutaka; Shigeyama, Toshikazu

    Neutron star mergers (NSMs) are one of the most plausible sources of r -process elements in the universe. Therefore, NSMs can also be a major source of ultra-heavy elements in cosmic rays. In this paper, we first estimate the contribution of r -process elements synthesized in NSMs to the ultra-heavy element cosmic rays (UHCRs) by calculating transport equations that take into account energy loss processes and spallations. We show that the flux of UHCRs accelerated by the NSMs themselves fluctuates by many orders of magnitude on a timescale of several million years and can overwhelm UHCRs accelerated by supernova remnantsmore » (SNRs) after an NSM takes place within a few kiloparsec from the solar system. Experiments with very long exposure times using meteorites as UHCR detectors can detect this fluctuation. As a consequence, we show that if NSMs are the primary source of UHCRs, future experiments using meteorites may be able to reveal the event history of NSMs in the solar vicinity. We also describe a possible difference in the abundance pattern and energy spectrum of UHCRs between NSM and SNR accelerations.« less

  3. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Optical Extension for Neutron Capture Elements

    NASA Astrophysics Data System (ADS)

    Melendez, Matthew; O'Connell, Julia; Frinchaboy, Peter M.; Donor, John; Cunha, Katia M. L.; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Pinsonneault, Marc H.; Roman-Lopes, Alexandre; Stassun, Keivan G.; APOGEE Team

    2017-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. However, neutron capture elements are very limited in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we are conducting a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. As part of this effort, we present Ba II, La II, Ce II and Eu II results for a few open clusters without previous abundance measurements using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph.This work is supported by an NSF AAG grant AST-1311835.

  4. Abundances of carbon-enhanced metal-poor stars as constraints on their formation

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Nordström, B.; Hansen, T. T.; Kennedy, C. R.; Placco, V. M.; Beers, T. C.; Andersen, J.; Cescutti, G.; Chiappini, C.

    2016-04-01

    Context. An increasing fraction of carbon-enhanced metal-poor (CEMP) stars is found as their iron abundance, [Fe/H], decreases below [Fe/H] =-2.0. The CEMP-s stars have the highest absolute carbon abundances, [C/H], and are thought to owe their enrichment in carbon and the slow neutron-capture (s-process) elements to mass transfer from a former asymptotic giant branch (AGB) binary companion. The most Fe-poor CEMP stars are normally single, exhibit somewhat lower [C/H] than CEMP-s stars, but show no s-process element enhancement (CEMP-no stars). Abundance determinations of CNO offer clues to their formation sites. Aims: Our aim is to use the medium-resolution spectrograph X-Shooter/VLT to determine stellar parameters and abundances for C, N, Sr, and Ba in several classes of CEMP stars in order to further classify and constrain the astrophysical formation sites of these stars. Methods: Atmospheric parameters for our programme stars were estimated from a combination of V-K photometry, model isochrone fits, and estimates from a modified version of the SDSS/SEGUE spectroscopic pipeline. We then used X-Shooter spectra in conjunction with the 1D local thermodynamic equilibrium spectrum synthesis code MOOG, 1D ATLAS9 atmosphere models to derive stellar abundances, and, where possible, isotopic 12C/13C ratios. Results: Abundances (or limits) of C, N, Sr, and Ba are derived for a sample of 27 faint metal-poor stars for which the X-Shooter spectra have sufficient signal-to-noise ratios (S/N). These moderate resolution, low S/N (~10-40) spectra prove sufficient to perform limited chemical tagging and enable assignment of these stars into the CEMP subclasses (CEMP-s and CEMP-no). According to the derived abundances, 17 of our sample stars are CEMP-s and 3 are CEMP-no, while the remaining 7 are carbon-normal. For four CEMP stars, the subclassification remains uncertain, and two of them may be pulsating AGB stars. Conclusions: The derived stellar abundances trace the formation

  5. Rare-earth abundances in chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Evensen, N. M.; Hamilton, P. J.; Onions, R. K.

    1978-01-01

    Fifteen chondrites, including eight carbonaceous chondrites, were analyzed for rare earth element abundances by isotope dilution. Examination of REE for a large number of individual chondrites shows that only a small proportion of the analyses have flat unfractionated REE patterns within experimental error. While some of the remaining analyses are consistent with magmatic fractionation, many patterns, in particular those with positive Ce anomalies, can not be explained by known magmatic processes. Elemental abundance anomalies are found in all major chondrite classes. The persistence of anomalies in chondritic materials relatively removed from direct condensational processes implies that anomalous components are resistant to equilibrium or were introduced at a late stage of chondrite formation. Large-scale segregation of gas and condensate is implied, and bulk variations in REE abundances between planetary bodies is possible.

  6. The Galactic Chemical Evolution of r-Process Elements by Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Komiya, Yutaka; Shigeyama, Toshikazu

    Neutron star mergers (NSMs) are prime candidate sources of r-process elements in the universe but it have been said that NSMs cannot reproduce r-process elements on extremely metal-poor (EMP) stars. We revisit this problem using a new chemical evolution model with merger trees of galaxies. We consider (1) propagation of NSM ejecta of kilo-parsec scale due to its very large velocity and (2) star formation efficiency depending on the galaxy mass. In our model with these ingredients, NSMs can successfully reproduce the abundance distribution of EMP stars.

  7. Heavy Element Abundances in Two B0-B0.5 Main Sequence Stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.

    We propose FUSE observations of AV304 (B0.5V) and NGC346-637 B0V), two sharp-lined main-sequence stars in the Small Magellanic Cloud, to determine the abundances of heavy elements, especially those of the iron group. The FUSE spectral region contains numerous Fe III lines, including the resonance multiplet (UV 1) near 1130 Angstroms, that is excellent for abundance determinations and two strong multiplets of V III, an ion that does not produce measurable lines longward of 1200 Angstoms, in metal-deficient stars. In addition there are several measurable lines from Cr III and Mn III. A limited analyses of ground-based spectra of these stars by Dufton et al. (1990) and Rolleston et al. (1993) indicated an average underabundance of 0.7-0.8 dex for most light elements and a recent analysis of HSTSTIS data on AV304 by Peters & Grigsby (2001) suggests that the Fe group elements are depleted by the same amount relative to the sun. When combined with the HST-STIS results, this effort will represent the first attempt to measure the abundances of Fe group elements in the photospheres of early B, main sequence stars in an external galaxy. Although abundances of the Fe-peak elements are of interest because they are important for assessing opacities for stellar evolution calculations and the validity of theoretical calculations of explosive nucleosynthesis, the ground-based study did not yield this information because measurable lines from these species are found only in the UV spectral region. Abundances and abundance ratios of both heavy & light elements will be compared with the HST-STIS results from AV304, H II regions, supernova remnants, evolved massive stars in the SMC, and theoretical calculations of nucleosynthesis.

  8. New CNO Elemental Abundances in Planetary Nebulae from Spatially Resolved UV/Optical Emission Lines

    NASA Astrophysics Data System (ADS)

    Shaw, Richard A.; Kwitter, Karen B.; Henry, Richard B. C.; Dufour, Reginald J.; Balick, Bruce; Corradi, Romano

    2015-01-01

    We obtained HST/STIS long-slit spectra spanning 0.11 to 1.1 μm of co-spatial regions in 10 Galactic planetary nebulae (Dufour, et al., this conference), of which six present substantial changes in ionization with position. Under the assumption that elemental abundances are constant within these nebulae (but exterior to the wind of the central star), these spectra present a unique opportunity to examine the applicability of common ionization correction factors (ICFs) for deriving abundances. ICFs are the most common direct method in abundance analysis for accounting for unobserved or undetected ionization stages in nebulae, yet most ICF recipes have not been rigorously examined through modeling nor empirically tested through observation. In this preliminary study, we focussed on the astrophysically important abundances of C and N where strong ionic transitions are scarce in optical band, but plentiful in the satellite UV. We derived physical diagnostics (extinction, Te, Ne) and ionic abundances for the species of interest at various positions along the slit for each PN. We compared the elemental abundances derived from direct summation of the ionic abundances in the UV and optical to those derived using only optical emission, but corrected using standard ICFs. We found that the abundances were usually in good agreement, but there were significant exceptions. We also found that setting upper limits on emission from undetected ions was sometimes helpful in constraining the correction factors. Work is underway to construct photoionization models of these nebulae (see Miller, et al., this conference) to address the question of why ICFs are sometimes inaccurate, and to explore other ICF recipes for those cases.Support for Program number GO-12600 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

  9. The Abundance of Iron-Peak Elements and the Dust Composition in eta Carinae: Manganese

    NASA Technical Reports Server (NTRS)

    Bautista, M. A.; Melendez, M.; Hartman, H.; Gull, T. R.; Lodders, K.

    2010-01-01

    We study the chemical abundances of the Strontium Filament found in the ejecta of (eta) Carinae. In particular, we derive the abundances of iron-peak elements front spectra of their singly ionized ions present in the optical/IR spectra. In this paper we analyze the spectrum of Mn II using a new non-LTE model for this system. In constructing this models we carried out theoretical calculations of radiative transition rates and electron impact excitation rate coefficients. We find that relative to Ni the gas phase abundance ratio of Mn is roughly solar, similar to the Cr abundance but in contrast to the large enhancements in the abundances of Sc and Ti. NVe interpret this result as an indication of non-equilibrium condensation in the ejecta of (eta) Carinae.

  10. Pop III i-process nucleosynthesis and the elemental abundances of SMSS J0313-6708 and the most iron-poor stars

    NASA Astrophysics Data System (ADS)

    Clarkson, O.; Herwig, F.; Pignatari, M.

    2018-02-01

    We have investigated a highly energetic H-ingestion event during shell He burning leading to H-burning luminosities of log (LH/L⊙) ˜ 13 in a 45 M⊙ Pop III massive stellar model. In order to track the nucleosynthesis which may occur in such an event, we run a series of single-zone nucleosynthesis models for typical conditions found in the stellar evolution model. Such nucleosynthesis conditions may lead to i-process neutron densities of up to ˜1013 cm-3. The resulting simulation abundance pattern, where Mg comes from He burning and Ca from the i process, agrees with the general observed pattern of the most iron-poor star currently known, SMSS J031300.36-670839.3. However, Na is also efficiently produced in these i-process conditions, and the prediction exceeds observations by ˜2.5 dex. While this probably rules out this model for SMSS J031300.36-670839.3, the typical i-process signature of combined He burning and i process of higher than solar [Na/Mg], [Mg/Al], and low [Ca/Mg] is reproducing abundance features of the two next most iron-poor stars HE 1017-5240 and HE 1327-2326 very well. The i process does not reach Fe which would have to come from a low level of additional enrichment. i process in hyper-metal-poor or Pop III massive stars may be able to explain certain abundance patterns observed in some of the most metal-poor CEMP-no stars.

  11. Element-abundance inhomogeneity of interstellar matter as it follows from the chemical composition of the O-type supergiants HDE 226868 (Cyg X-1) and *alpha; Cam

    NASA Astrophysics Data System (ADS)

    Bochkarev, N. G.; Karitskaya, E. A.; Shimanskii, V. V.; Galazutdinov, G. A.

    2013-10-01

    By means of synthetic spectrum modeling with non-LTE effects, we determined element abundances in the atmospheres of two O supergiants with similar physical characteristics: HDE 226868 (the optical component of Cyg X-1) and α Cam. These objects are situated at the distance about 2.5 kpc from each other. HDE 226868 has higher abundances compared to α Cam. The differences of Al, S, Zn, and averaged CNO abundances are within 0.15-0.30 dex. This is in a good qualitative agreement with the inhomogeneity of the heavy-element distribution over the Galactic disk derived by Luck et al. (2006) from Cepheids. This finding confirms the inhomogeneity of chemical-element distribution on the scale of 2 kpc and is in agreement with the concept of interstellar-matter superclouds preserving their intrinsic particularities on a time scale in excess of 1 Gyr.

  12. Trace elements in chondritic stratospheric particles - Zinc depletion as a possible indicator of atmospheric entry heating

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.

    1992-01-01

    Major-element abundances in 11 C, C?, and TCA cosmic dust particles have been measured using SEM and TEM energy dispersive X-ray (EDX) systems. The Fe/Ni ratio, when coupled with major element abundances, appears to be a useful discriminator of cosmic particles. Three particles classified as C?, but having Fe/Ni peak height ratios similar to those measured on the powdered Allende meteorite sample in their HSC EDX spectra, exhibit chondritic minor-/trace-element abundance patterns, suggesting they are extraterrestrial. The one particle classified as C-type, but without detectable Ni in its JSC EDX spectrum, exhibits an apparently nonchondritic minor-/trace-element abundance pattern. A class of particles that are chondritic except for large depletions in the volatile elements Zn and S has been identified. It is likely that these particles condensed with a C1 abundance pattern and that Zn and S were removed by some subsequent process.

  13. A sensitivity study of s-process: the impact of uncertainties from nuclear reaction rates

    NASA Astrophysics Data System (ADS)

    Vinyoles, N.; Serenelli, A.

    2016-01-01

    The slow neutron capture process (s-process) is responsible for the production of about half the elements beyond the Fe-peak. The production sites and the conditions under which the different components of s-process occur are relatively well established. A detailed quantitative understanding of s-process nucleosynthesis may yield light in physical processes, e.g. convection and mixing, taking place in the production sites. For this, it is important that the impact of uncertainties in the nuclear physics is well understood. In this work we perform a study of the sensitivity of s-process nucleosynthesis, with particular emphasis in the main component, on the nuclear reaction rates. Our aims are: to quantify the current uncertainties in the production factors of s-process elements originating from nuclear physics and, to identify key nuclear reactions that require more precise experimental determinations. In this work we studied two different production sites in which s-process occurs with very different neutron exposures: 1) a low-mass extremely metal-poor star during the He-core flash (nn reaching up to values of ∼ 1014cm-3); 2) the TP-AGB phase of a M⊙, Z=0.01 model, the typical site of the main s-process component (nn up to 108 — 109cm-3). In the first case, the main variation in the production of s-process elements comes from the neutron poisons and with relative variations around 30%-50%. In the second, the neutron poison are not as important because of the higher metallicity of the star that actually acts as a seed and therefore, the final error of the abundances are much lower around 10%-25%.

  14. Apollo 16 returned lunar samples - Lithophile trace-element abundances

    NASA Technical Reports Server (NTRS)

    Philpotts, J. A.; Schuhmann, S.; Kouns, C. W.; Lum, R. K. L.; Bickel, A. L.; Schnetzler, C. C.

    1973-01-01

    Lithium, K, Rb, Sr, Ba, rare-earth, Zr, and Hf abundances have been determined by mass-spectrometric isotope-dilution for Apollo 16 soils, anorthosite 61016, and 'basalt' 68415 whole-rock and separated pyroxene and plagioclase. Our sample of 61016 is similar to some other lunar anorthosites in lithophile trace-element concentrations but at a slightly lower level. It was probably accumulated from a little differentiated basalt. Basalt 68415 might be a homogeneous mixture of KREEP and anorthosite material; it appears to have crystallized under conditions as reducing as those holding for mare-basalts. The soil fines cover only a limited compositional range. No obvious chemical differences were noted between the Descartes and Cayley formations. Most of the compositional variation of the soils can be accounted for in terms of the addition of plagioclase. The existence of very high alumina basalt as an independent magma-type appears debatable in view of its KREEP-like lithophile trace-element relative concentrations and the observed lunar radioactivity distribution.

  15. The Abundances of the Fe Group Elements in Early B Stars in the Magellanic Clouds and Our Galaxy

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine Joan; Adelman, Saul Joseph

    2015-08-01

    The abundances of the Fe-peak elements (Ti, V, Cr, Mn, Fe, Co, and Ni) are of interest as they are important for assessing opacities for stellar evolution calculations, confirming theoretical calculations of explosive nucleosynthesis, and inferring the past history of supernova activity in a galaxy. FUSE FUV spectra of early B stars in the LMC and SMC and HST/STIS FUV/NUV spectra of nearby B stars in our galaxy are analyzed with the Hubeny/Lanz programs TLUSTY/SYNSPEC to determine abundance for the Fe group elements and produce a map of these abundances in the Magellanic Clouds (MC) and Magellanic Bridge (MB). Except for four weak multiplets of Fe III there are no measurable lines from the Fe group in the optical region. The Fe group species found in the FUV spectra of early B stars are primarily in the second stage of ionization. The best set of lines in the FUSE spectral region are Fe III (UV1), V III 1150 Å, and Cr III 1137 Å. Analysis of the galactic B stars provides a good assessment of the reliability of the atomic parameters that are used for the MC calculations. Twenty-two early B stars in the MC and MB and five in our galaxy were analyzed. In general the Fe group abundances range from solar to slightly below solar in our region of the galaxy. But in the MCs the abundances of V, Cr, and Fe tend to be significantly lower than the mean metal abundances for the galaxy. Maps of the Fe group abundances and their variations in the LMC and SMC, tracers of recent enrichment of the ISM from supernova activity, are shown. Support from NASA grants NAG5-13212, NNX10AD66G, STScI HST-GO-13346.22, and USC’s Women in Science and Engineering (WiSE) program is greatly appreciated.

  16. GALACTIC CHEMICAL EVOLUTION: THE IMPACT OF THE {sup 13}C-POCKET STRUCTURE ON THE s -PROCESS DISTRIBUTION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bisterzo, S.; Travaglio, C.; Wiescher, M.

    2017-01-20

    The solar s -process abundances have been analyzed in the framework of a Galactic Chemical Evolution (GCE) model. The aim of this work is to implement the study by Bisterzo et al., who investigated the effect of one of the major uncertainties of asymptotic giant branch (AGB) yields, the internal structure of the {sup 13}C pocket. We present GCE predictions of s -process elements computed with additional tests in the light of suggestions provided in recent publications. The analysis is extended to different metallicities, by comparing GCE results and updated spectroscopic observations of unevolved field stars. We verify that themore » GCE predictions obtained with different tests may represent, on average, the evolution of selected neutron-capture elements in the Galaxy. The impact of an additional weak s -process contribution from fast-rotating massive stars is also explored.« less

  17. Solar Coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the cosmic ray subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with 3 Z or = 30. It is found that the ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  18. Solar coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H. H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the cosmic ray subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with Z = 6-30. It is found that the ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  19. Solar coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the Cosmic Ray Subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with 3 = or Z or = 30. The ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  20. A Large C+N+O Abundance Spread in Giant Stars of the Globular Cluster NGC 1851

    NASA Astrophysics Data System (ADS)

    Yong, David; Grundahl, Frank; D'Antona, Francesca; Karakas, Amanda I.; Lattanzio, John C.; Norris, John E.

    2009-04-01

    Abundances of C, N, and O are determined in four bright red giants that span the known abundance range for light (Na and Al) and s-process (Zr and La) elements in the globular cluster NGC 1851. The abundance sum C+N+O exhibits a range of 0.6 dex, a factor of 4, in contrast to other clusters in which no significant C+N+O spread is found. Such an abundance range offers support for the Cassisi et al. scenario in which the double subgiant branch populations are coeval but with different mixtures of C+N+O abundances. Further, the Na, Al, Zr, and La abundances are correlated with C+N+O, and therefore NGC 1851 is the first cluster to provide strong support for the scenario in which asymptotic giant branch stars are responsible for the globular cluster light element abundance variations. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

  1. METAL-POOR STARS OBSERVED WITH THE MAGELLAN TELESCOPE. I. CONSTRAINTS ON PROGENITOR MASS AND METALLICITY OF AGB STARS UNDERGOING s-PROCESS NUCLEOSYNTHESIS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Placco, Vinicius M.; Rossi, Silvia; Frebel, Anna

    2013-06-20

    We present a comprehensive abundance analysis of two newly discovered carbon-enhanced metal-poor (CEMP) stars. HE 2138-3336 is a s-process-rich star with [Fe/H] = -2.79, and has the highest [Pb/Fe] abundance ratio measured thus far, if non-local thermodynamic equilibrium corrections are included ([Pb/Fe] = +3.84). HE 2258-6358, with [Fe/H] = -2.67, exhibits enrichments in both s- and r-process elements. These stars were selected from a sample of candidate metal-poor stars from the Hamburg/ESO objective-prism survey, and followed up with medium-resolution (R {approx} 2000) spectroscopy with GEMINI/GMOS. We report here on derived abundances (or limits) for a total of 34 elements inmore » each star, based on high-resolution (R {approx} 30, 000) spectroscopy obtained with Magellan-Clay/MIKE. Our results are compared to predictions from new theoretical asymptotic giant branch (AGB) nucleosynthesis models of 1.3 M{sub Sun} with [Fe/H] = -2.5 and -2.8, as well as to a set of AGB models of 1.0 to 6.0 M{sub Sun} at [Fe/H] = -2.3. The agreement with the model predictions suggests that the neutron-capture material in HE 2138-3336 originated from mass transfer from a binary companion star that previously went through the AGB phase, whereas for HE 2258-6358, an additional process has to be taken into account to explain its abundance pattern. We find that a narrow range of progenitor masses (1.0 {<=} M(M{sub Sun }) {<=} 1.3) and metallicities (-2.8 {<=} [Fe/H] {<=}-2.5) yield the best agreement with our observed elemental abundance patterns.« less

  2. Determination of Trace and Volatile Element Abundance Systematics of Lunar Pyroclastic Glasses 74220 and 15426 Using LA-ICP-MS

    NASA Technical Reports Server (NTRS)

    McIntosh, E. Carrie; Porrachia, Magali; McCubbin, Francis M.; Day, James M. D.

    2017-01-01

    Since their recognition as pyroclastic glasses generated by volcanic fire fountaining on the Moon, 74220 and 15426 have garnered significant scientific interest. Early studies recognized that the glasses were particularly enriched in volatile elements on their surfaces. More recently, detailed analyses of the interiors of the glasses, as well as of melt inclusions within olivine grains associated with the 74220 glass beads, have determined high H2O, F, Cl and S contents. Such elevated volatile contents seem at odds with evidence from moderately volatile elements (MVE), such as Zn and K, for a volatile- depleted Moon. In this study, we present initial results from an analytical campaign to study trace element abundances within the pyroclastic glass beads. We report trace element data determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for 15426 and 74220.

  3. Origin and Evolution of the Elements

    NASA Astrophysics Data System (ADS)

    McWilliam, Andrew; Rauch, Michael

    2004-09-01

    Introduction; List of participants; 1. Mount Wilson Observatory contributions to the study of cosmic abundances of the chemical elements George W. Preston; 2. Synthesis of the elements in stars: B2FH and beyond E. Margaret Burbidge; 3. Stellar nucleosynthesis: a status report 2003 David Arnett; 4. Advances in r-process nucleosynthesis John J. Cowan and Christopher Sneden; 5. Element yields of intermediate-mass stars Richard B. C. Henry; 6. The impact of rotation on chemical abundances in red giant branch stars Corinne Charbonnel; 7. s-processing in AGB stars and the composition of carbon stars Maurizio Busso, Oscar Straniero, Roberto Gallino, and Carlos Abia; 8. Models of chemical evolution Francesca Matteucci; 9. Model atmospheres and stellar abundance analysis Bengt Gustafsson; 10. The light elements: lithium, beryllium, and boron Ann Merchant Boesgaard; 11. Extremely metal-poor stars John E. Norris; 12. Thin and thick galactic disks Poul E. Nissen; 13. Globular clusters and halo field stars Christopher Sneden, Inese I. Ivans and Jon P. Fulbright; 14. Chemical evolution in ω Centauri Verne V. Smith; 15. Chemical composition of the Magellanic Clouds, from young to old stars Vanessa Hill; 16. Detailed composition of stars in dwarf spheroidal galaxies Matthew D. Shetrone; 17. The evolutionary history of Local Group irregular galaxies Eva K. Grebel; 18. Chemical evolution of the old stellar populations of M31 R. Michael Rich; 19. Stellar winds of hot massive stars nearby and beyond the Local Group Fabio Bresolin and Rolf P. Kudritzki; 20. Presolar stardust grains Donald D. Clayton and Larry R. Nittler; 21. Interstellar dust B. T. Draine; 22. Interstellar atomic abundances Edward B. Jenkins; 23. Molecules in the interstellar medium Tommy Wiklind; 24. Metal ejection by galactic winds Crystal L. Martin; 25. Abundances from the integrated light of globular clusters and galaxies Scott C. Trager; 26. Abundances in spiral and irregular galaxies Donald R. Garnett; 27

  4. Elemental abundance analyses with coadded DAO spectrograms. IV - Revision of previous analyses. V - The mercury-manganese stars Phi Herculis, 28 Herculis and HR 7664

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.

    1988-01-01

    Changes in chromium, manganese, and nickel abundances derived from singly ionized lines are incorporated into the elemental abundance of Adelman and Hill (1987) in order to provide more accurate gf values and damping constants for several atomic species. An improved agreement with the values from neutral lines of the same element is found. In the second part, the method is applied to an elemental abundance analysis of three mercury-manganese stars, and correlations are found between the derived abundances and the effective temperature.

  5. SP_Ace: a new code to derive stellar parameters and elemental abundances

    NASA Astrophysics Data System (ADS)

    Boeche, C.; Grebel, E. K.

    2016-03-01

    Context. Ongoing and future massive spectroscopic surveys will collect large numbers (106-107) of stellar spectra that need to be analyzed. Highly automated software is needed to derive stellar parameters and chemical abundances from these spectra. Aims: We developed a new method of estimating the stellar parameters Teff, log g, [M/H], and elemental abundances. This method was implemented in a new code, SP_Ace (Stellar Parameters And Chemical abundances Estimator). This is a highly automated code suitable for analyzing the spectra of large spectroscopic surveys with low or medium spectral resolution (R = 2000-20 000). Methods: After the astrophysical calibration of the oscillator strengths of 4643 absorption lines covering the wavelength ranges 5212-6860 Å and 8400-8924 Å, we constructed a library that contains the equivalent widths (EW) of these lines for a grid of stellar parameters. The EWs of each line are fit by a polynomial function that describes the EW of the line as a function of the stellar parameters. The coefficients of these polynomial functions are stored in a library called the "GCOG library". SP_Ace, a code written in FORTRAN95, uses the GCOG library to compute the EWs of the lines, constructs models of spectra as a function of the stellar parameters and abundances, and searches for the model that minimizes the χ2 deviation when compared to the observed spectrum. The code has been tested on synthetic and real spectra for a wide range of signal-to-noise and spectral resolutions. Results: SP_Ace derives stellar parameters such as Teff, log g, [M/H], and chemical abundances of up to ten elements for low to medium resolution spectra of FGK-type stars with precision comparable to the one usually obtained with spectra of higher resolution. Systematic errors in stellar parameters and chemical abundances are presented and identified with tests on synthetic and real spectra. Stochastic errors are automatically estimated by the code for all the parameters

  6. Docosahexaneoic acid (22:6,n-3) regulates rat hepatocyte SREBP-1 nuclear abundance by Erk- and 26S proteasome-dependent pathways

    PubMed Central

    Botolin, Daniela; Wang, Yun; Christian, Barbara; Jump, Donald B.

    2009-01-01

    Insulin induces and dietary n-3 PUFAs suppress hepatic de novo lipogenesis by controlling sterol-regulatory element binding protein-1 nuclear abundance (nSREBP-1). Our goal was to define the mechanisms involved in this regulatory process. Insulin treatment of rat primary hepatocytes rapidly augments nSREBP-1 and mRNASREBP-1c while suppressing mRNAInsig-2 but not mRNAInsig-1. These events are preceded by rapid but transient increases in Akt and Erk phosphorylation. Removal of insulin from hepatocytes leads to a rapid decline in nSREBP-1 [half-time (T1/2) ~ 10 h] that is abrogated by inhibitors of 26S proteasomal degradation. 22:6,n-3, the major n-3 PUFA accumulating in livers of fish oil-fed rats, suppresses hepatocyte levels of nSREBP-1, mRNASREBP-1c, and mRNAInsig-2 but modestly and transiently induces mRNAInsig-1. More importantly, 22:6,n-3 accelerates the disappearance of hepatocyte nSREBP-1 (T1/2 ~ 4 h) through a 26S proteasome-dependent process. 22:6,n-3 has minimal effects on microsomal SREBP-1 and sterol-regulatory element binding protein cleavage-activating protein or nuclear SREBP-2. 22:6,n-3 transiently inhibits insulin-induced Akt phosphorylation but induces Erk phosphorylation. Inhibitors of Erk phosphorylation, but not overexpressed constitutively active Akt, rapidly attenuate 22:6,n-3 suppression of nSREBP-1. Thus, 22:6,n-3 suppresses hepatocyte nSREBP-1 through 26S proteasome- and Erk-dependent pathways. These studies reveal a novel mechanism for n-3 PUFA regulation of hepatocyte nSREBP-1 and lipid metabolism.—Botolin, D., Y. Wang, B. Christian, and D. B. Jump. Docosahexaneoic acid (22:6,n-3) regulates rat hepatocyte SREBP-1 nuclear abundance by Erk- and 26S proteasome-dependent pathways. PMID:16222032

  7. Abundances, Ionization States, Temperatures, and FIP in Solar Energetic Particles

    NASA Astrophysics Data System (ADS)

    Reames, Donald V.

    2018-04-01

    The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in {}3He/{}4He from resonant wave-particle interactions in the small "impulsive" SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio A/Q, rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in solar jets. In contrast, in the largest SEP events, the "gradual" events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of solar coronal abundances, but A/Q-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states Q show coronal temperatures of 1-2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of Q are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of A/Q, we can use abundances to deduce the probable Q-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs

  8. Trace Element Abundances in Refractory Inclusions from Antarctic Micrometeorites

    NASA Astrophysics Data System (ADS)

    Greshake, A.; Hoppe, P.; Bischoff, A.

    1995-09-01

    Refractory inclusions are charcteristic components in carbonaceous chondrites. Therefore, refractory inclusions found in micrometeorites can give important hints about the relationship between micrometeorites and carbonaceous chondrites. So far, only a few inclusions were found in micrometeorites [1-4]. In this study we report the first trace element analysis of perovskite and fassaite found in micrometeorites. We studied two Antarctic micrometeorites by ASEM, EMP, and SIMS. The first particle is 120 micrometers in size mainly consisting of a fine-grained matrix of dehydrated former phyllosilikates that enclose a 5 micrometers sized perovskite [5]. The perovskite is surrounded by a 1 micrometers thick rim of ilmenite and contains up to 1.3 wt% FeO as determined by EMP. The trace element abundances were determined by SIMS following the procedure described by [6]. The REE pattern of the perovskite is shown in Fig. 1. The pattern is closely related to the Group II pattern with its typical depletion of the more refractory REEs [7]. It is also very similar to the REE abundances of perovskite from Murchison (CM) [8] and CH-chondrites [9]. This may indicate a relationship between this micrometeorite and components in carbonaceous chondrites. The second micrometeorite is 100 micrometers in size consisting of a fine-grained (20 micrometers across) and a coarse-grained (80 micrometers across) area. Both areas contain fassaite with different chemical compositions. The particle was previously analyzed by Lindstrom and Kloeck [1] without knowing the mineralogy. We carried out SIMS analysis of each area of the micrometeorite separately. The TEE patterns of these two areas are similar and show in general a Group III pattern (20-30x CI) in which the more refractory REEs are not fractionated. The negative Eu anomaly is much more apparent in the coarse-grained area and no Yb anomaly is apparent in one of the areas. This is the first CAI of a micrometeorite showing a Group III REE

  9. Abundances of sulfur in the Milky Way Disk from Peimbert Type II planetary nebulae

    NASA Astrophysics Data System (ADS)

    Milingo, Jacquelynne Brenda

    2000-08-01

    Sulfur abundance gradients and heavy element ratios for the Milky Way Disk are constructed based upon newly acquired spectrophotometry of Type II planetary nebulae (PN). These spectra extend from 3600-9600 angstroms allowing us to use the [SIII] 9069 and 9532 angstrom lines to improve upon earlier sulfur abundance estimates. Considering a significant portion of sulfur in PN exists in the S(+2) ionization stage (and higher) this method should allow us to extrapolate more reliable total element abundance from ionic abundances. Given the progenitor mass and location of Type II PN (close to the Galactic disk), this sample of objects is free of nucleosynthetic self-contamination and thus their S abundances in particular are expected to reflect levels of these elements in the interstellar medium at the time of PN progenitor formation. These sulfur abundances provide constraints for studying various aspects of GCE such as massive star yields and the distribution of S across the Milky Way disk.

  10. The Ubiquity of the Rapid Neutron-capture Process

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Cowan, John J.; Karakas, Amanda I.; Kratz, Karl-Ludwig; Lugaro, Maria; Simmerer, Jennifer; Farouqi, Khalil; Sneden, Christopher

    2010-12-01

    To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn, Z= 30), yttrium (Y, Z= 39), lanthanum (La, Z= 57), europium (Eu, Z= 63), and lead (Pb, Z= 82). Our sample of 161 metal-poor stars includes new measurements from 88 high-resolution and high signal-to-noise spectra obtained with the Tull Spectrograph on the 2.7 m Smith Telescope at the McDonald Observatory, and other abundances are adopted from the literature. We use models of the s-process in asymptotic giant branch stars to characterize the high Pb/Eu ratios produced in the s-process at low metallicity, and our new observations then allow us to identify a sample of stars with no detectable s-process material. In these stars, we find no significant increase in the Pb/Eu ratios with increasing metallicity. This suggests that s-process material was not widely dispersed until the overall Galactic metallicity grew considerably, perhaps even as high as [Fe/H] =-1.4, in contrast with earlier studies that suggested a much lower mean metallicity. We identify a dispersion of at least 0.5 dex in [La/Eu] in metal-poor stars with [Eu/Fe] <+0.6 attributable to the r-process, suggesting that there is no unique "pure" r-process elemental ratio among pairs of rare earth elements. We confirm earlier detections of an anti-correlation between Y/Eu and Eu/Fe bookended by stars strongly enriched in the r-process (e.g., CS 22892-052) and those with deficiencies of the heavy elements (e.g., HD 122563). We can reproduce the range of Y/Eu ratios using simulations of high-entropy neutrino winds of core-collapse supernovae that include charged-particle and neutron-capture components of r-process nucleosynthesis. The heavy element abundance patterns in most metal-poor stars do not resemble that of CS 22892-052, but the presence of heavy elements such as Ba in nearly all metal-poor stars without s-process enrichment suggests that the r-process

  11. Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace element geochemistry, isotopic abundances, and trace organic chemistry of several fragments from L2008#5

    NASA Technical Reports Server (NTRS)

    Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.

    1994-01-01

    The topics discussed include the following: noble gas content and release temperatures; trace element abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.

  12. Solar Flare Abundances of Potassium, Argon, and Sulphur

    NASA Technical Reports Server (NTRS)

    Oegerle, William (Technical Monitor); Phillips, K. J. H.; Sylwester, J.; Sylwester, B.; Landi, E.

    2003-01-01

    The absolute coronal abundances of potassium has been determined for the first time from X-ray solar flare line and continuous spectra together with absolute and relative abundances of Ar and S. Potassium is of importance in the continuing debate concerning the nature of the coronal/photospheric element abundance ratios which are widely considered to depend on first ionization potential since it has the lowest FIP of any common element in the Sun. The measurements were obtained with the RESIK crystal spectrometer on the Coronas-F spacecraft. A differential emission measure DEM = const. x exp (-(beta)T(sub e) was found to be the most consistent with the data out of three models considered. We find that the coronal ratio [K/H] = 3.7 x 10(exp - 7), a factor 3 times photospheric, in agreement with other observations using line-to-line ratios. Our measured value for the coronal ratio [Ar/H] = 1.5 x 10(exp -6) is significantly less than photospheric, indicating that there is a slight depletion of this high-FIP element in the corona. For S (an intermediate-FIP element) we obtained [S/H] = 2.2 x 10(exp - 5), approximately the same as in previous work.

  13. r-process enhanched metal-poor stars

    NASA Astrophysics Data System (ADS)

    Cowan, John; Sneden, Christopher; Lawler, James E.; Den Hartog, Elizabeth A.

    Abundance observations indicate the presence of rapid-neutron capture (i.e., r-process) elements in old Galactic halo and globular cluster stars. These observations provide insight into the nature of the earliest generations of stars in the Galaxy - the progenitors of the halo stars - responsible for neutron-capture synthesis of the heavy elements. The large star-to-star scatter observed in the abundances of neutron-capture element/iron ratios at low metallicities - which diminishes with in- creasing metallicity or [Fe/H] - suggests the formation of these heavy elements (presumably from certain types of supernovae) was rare in the early Galaxy. The stellar abundances also indicate a change from the r-process to the slow neutron capture (i.e., s-) process at higher metallicities in the Galaxy and provide insight into Galactic chemical evolution. Finally, the detection of thorium and uranium in halo and globular cluster stars offers an independent age-dating technique that can put lower limits on the age of the Galaxy, and hence the Universe.

  14. Ages and Heavy Element Abundances from Very Metal-poor Stars in the Sagittarius Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Hansen, Camilla Juul; El-Souri, Mariam; Monaco, Lorenzo; Villanova, Sandro; Bonifacio, Piercarlo; Caffau, Elisabetta; Sbordone, Luca

    2018-03-01

    Sagittarius (Sgr) is a massive disrupted dwarf spheroidal galaxy in the Milky Way halo that has undergone several stripping events. Previous chemical studies were restricted mainly to a few, metal-rich ([Fe/H] \\gtrapprox -1) stars that suggested a top-light initial mass function (IMF). Here we present the first high-resolution, very metal-poor ([Fe/H] =‑1 to ‑3) sample of 13 giant stars in the main body of Sgr. We derive abundances of 13 elements, namely C, Ca, Co, Fe, Sr, Ba, La, Ce, Nd, Eu, Dy, Pb, and Th, that challenge the interpretation based on previous studies. Our abundances from Sgr mimic those of the metal-poor halo, and our most metal-poor star ([Fe/H] ∼ -3) indicates a pure r-process pollution. Abundances of Sr, Pb, and Th are presented for the first time in Sgr, allowing for age determination using nuclear cosmochronology. We calculate ages of 9+/- 2.5 {Gyr}. Most of the sample stars have been enriched by a range of asymptotic giant branch (AGB) stars with masses between 1.3 and 5 M ⊙. Sgr J190651.47–320147.23 shows a large overabundance of Pb (2.05 dex) and a peculiar abundance pattern best fit by a 3 M ⊙ AGB star. Based on star-to-star scatter and observed abundance patterns, a mixture of low- and high-mass AGB stars and supernovae (15–25 M ⊙) is necessary to explain these patterns. The high level (0.29 ± 0.05 dex) of Ca indicates that massive supernovae must have existed and polluted the early ISM of Sgr before it lost its gas. This result is in contrast with a top-light IMF with no massive stars polluting Sgr. Based on data obtained UVES/VLT ID: 083.B-0774, 075.B-0127.

  15. Coronal Element Abundances of the Post-Common Envelope Binary V471 Tauri with ASCA

    NASA Technical Reports Server (NTRS)

    Still, Martin; Hussain, Gaitee; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report on ASCA observations of the coronally active companion star in the post-common envelope binary V471 Tau. While it would be prudent to check the following results with grating spectroscopy, we find that a single-temperature plasma model does not fit the data. Two temperature models with variable abundances indicate that Fe is underabundant compared to the Hyades photospheric mean, whereas, the high first ionization potential element Ne is overabundant. This is indicative of the inverse first ionization effect, believed to result from the fractionation of ionized material by the magnetic field in the upper atmosphere of the star. Evolutionary calculations indicate that there should be no peculiar abundances on the companion star resulting from the common envelope epoch. Indeed, we find no evidence for peculiar abundances, although uncertainties are high.

  16. Coronal Elemental Abundances in Solar Emerging Flux Regions

    NASA Astrophysics Data System (ADS)

    Baker, Deborah; Brooks, David H.; van Driel-Gesztelyi, Lidia; James, Alexander W.; Démoulin, Pascal; Long, David M.; Warren, Harry P.; Williams, David R.

    2018-03-01

    The chemical composition of solar and stellar atmospheres differs from the composition of their photospheres. Abundances of elements with low first ionization potential (FIP) are enhanced in the corona relative to high-FIP elements with respect to the photosphere. This is known as the FIP effect and it is important for understanding the flow of mass and energy through solar and stellar atmospheres. We used spectroscopic observations from the Extreme-ultraviolet Imaging Spectrometer on board the Hinode observatory to investigate the spatial distribution and temporal evolution of coronal plasma composition within solar emerging flux regions inside a coronal hole. Plasma evolved to values exceeding those of the quiet-Sun corona during the emergence/early-decay phase at a similar rate for two orders of magnitude in magnetic flux, a rate comparable to that observed in large active regions (ARs) containing an order of magnitude more flux. During the late-decay phase, the rate of change was significantly faster than what is observed in large, decaying ARs. Our results suggest that the rate of increase during the emergence/early-decay phase is linked to the fractionation mechanism that leads to the FIP effect, whereas the rate of decrease during the later decay phase depends on the rate of reconnection with the surrounding magnetic field and its plasma composition.

  17. Gas-phase abundances of refractory elements in planetary nebulae - A hot-wind model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shields, G.A.

    Planetary nebulae (PN) characteristically show large gas-phase depletions of some refractory elements, with Fe/H and Ca/H concentration ratios approximately equal to -1.5. In contrast, the gas-phase abundance of carbon is large, with a C/H concentration ratio greater than approximately +0.3. This pattern is difficult to understand in terms of grain formation and destruction during PN formation. However, these abundances are consistent with a model (Kwok, Purton, and FitzGerald, 1978) in which the PN shell consists of material expelled as a wind during the red-giant phase and subsequently compressed and accelerated by the impact of a hot stellar wind from themore » central star.« less

  18. Taking Another Look: Zr and Y abundances in Halo Stars

    NASA Astrophysics Data System (ADS)

    Burris, Debra L.; Jones, E.

    2007-12-01

    The elements Zirconium and Yttrium are produced via neutron capture (n-capture). These elements reside in the mass range where there is uncertainty about the production mechanism at early time. The rapid n-capture process (r-process) was believed to be responsible for the production, but no study (Burris et al 2000, Gilroy et al 1988 and others) has been able to successfully use the r-process to reproduce the abundance signature for elements in this mass range for metal-poor halo stars. It has been suggested (Sneden and Cowan 2003) that there may be an undiscovered component to the r-process. New abundance calculations for these elements have been conducted for a sample of metal-poor halo stars. Transition probabilities for Zr II from Malcheva et al (2006) and for YII from Hannaford et al (1982) were utilized in these calculations. This work is supported in part by the AAS Small Grant Program, the Arkansas Space Grant Consortium and the UCA Undergraduate Research Council.

  19. The s-Process Nucleosynthesis in Extremely Metal-Poor Stars as the Generating Mechanism of Carbon Enhanced Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Suda, Takuma; Yamada, Shimako; Fujimoto, Masayuki Y.

    The origin of carbon-enhanced metal-poor (CEMP) stars plays a key role in characterising the formation and evolution of the first stars and the Galaxy since the extremely-metal-poor (EMP) stars with [Fe/H] ≤ -2.5 share the common features of carbon enhancement in their surface chemical compositions. The origin of these stars is not yet established due to the controversy of the origin of CEMP stars without the enhancement of s-process element abundances, i.e., so called CEMP-no stars. In this paper, we elaborate the s-process nucleosynthesis in the EMP AGB stars and explore the origin of CEMP stars. We find that the efficiency of the s-process is controlled by O rather than Fe at [Fe/H] ≲ -2. We demonstrate that the relative abundances of Sr, Ba, Pb to C are explained in terms of the wind accretion from AGB stars in binary systems.

  20. Nuclear Reactions and the ν p-Process

    NASA Astrophysics Data System (ADS)

    Fröhlich, Carla; Hatcher, Daniel; Perdikakis, Georgios; Nikas, Stylianos

    In understanding the origin of the heavy elements, the "light heavy elements" pose a particular challenge: The two neutron-capture processes, r- and s-process, cannot explain the abundances patterns seen in very old galactic halo stars. A proposed solution to this problem is the ν p-process, which takes place in the strong neutrino-driven winds of core-collapse supernovae. In the ν p-process, a sequence of (n, p) and (p, γ ) reactions allows for the synthesis of elements with atomic numbers A > 64, which includes Sr, Y, Zr, and others possibly up to Sn. The relevant reaction rates are all based on statistical model predictions and carry some uncertainty. Here, the sensitivity of the final ν p-process abundance pattern on modifications of (n, p), (p, γ ), and (n, γ ) reactions are characterized. Only few reactions affect the final abundance pattern and hence warrant a more detailed study of the reaction rate.

  1. Contribution of fission to heavy-element nucleosynthesis in an astrophysical r-process

    NASA Astrophysics Data System (ADS)

    Korneev, I. Yu.; Panov, I. V.

    2011-12-01

    During the formation of heavy elements in the neutron star merger (NSM) scenario with a fairly long duration of the r-process, most of the seed nuclei rapidly burn out at the initial stage. The nucleosynthesis wave rapidly reaches the region of actinoids, where beta-delayed, neutron-induced, and spontaneous fission are the main reaction channels. The fission products of transuranium elements are again drawn into the r-process as new seed nuclei to form the yields of elements with mass numbers A > 100. The contribution from the various types of fission to the formation of heavy and superheavy nuclei is investigated. The proposed r-process model applied to the NSM scenario describes well the observed abundances of chemical elements, which confirms the formation of the main r-process component in the NSM scenario. Simple extrapolations of the spontaneous fission half-lives are shown to be inapplicable for the region of nuclei with N ˜ 184, because the formulas do not reflect the increase in half-life when the shell structure changes as the number of neutrons approaches 184. The formation of superheavy elements in the r-process is possible, but their survival depends to a large extent on how reliable the predictions of nuclear parameters, including the half-lives of the forming nuclei from the island of long-lived isotopes, are. The contributions from various types of fission—neutron-induced, beta-delayed, and spontaneous one—to the formation of heavy elements in the main r-process have been determined.

  2. Interstellar Abundances Toward X Per, Revisited

    NASA Technical Reports Server (NTRS)

    Valencic, Lynne A.; Smith, Randall K.

    2014-01-01

    The nearby X-ray binary X Per (HD 24534) provides a useful beacon with which to measure elemental abundances in the local ISM. We examine absorption features of 0, Mg, and Si along this line of sight using spectra from the Chandra Observatory's LETG/ ACIS-S and XMM-Newton's RGS instruments. In general, we find that the abundances and their ratios are similar to those of young F and G stars and the most recent solar values. We compare our results with abundances required by dust grain models.

  3. Interstellar Abundances Toward X Per, Revisited

    NASA Technical Reports Server (NTRS)

    Valencic, Lynne A.; Smith, Randall K.

    2012-01-01

    The nearby X-ray binary X Per (HD 24534) provides a useful beacon with which to measure elemental abundances in the local ISM. We examine absorption features of O, Mg, and Si along this line of sight using spectra from the Chandra Observatory's LETG/ACIS-S and XMM-Newton's RGS instruments. In general, we find that the abundances and their ratios are similar to those of young F and G stars and the most recent solar values. We compare our results with abundances required by dust grain models.

  4. Bringing abundance into environmental politics: Constructing a Zionist network of water abundance, immigration, and colonization.

    PubMed

    Alatout, Samer

    2009-06-01

    For more than five decades, resource scarcity has been the lead story in debates over environmental politics. More importantly, and whenever environmental politics implies conflict, resource scarcity is constructed as the culprit. Abundance of resources, if at all visited in the literature, holds less importance. Resource abundance is seen, at best, as the other side of scarcity--maybe the successful conclusion of multiple interventions that may turn scarcity into abundance. This paper reinstates abundance as a politico-environmental category in its own right. Rather than relegating abundance to a second-order environmental actor that matters only on occasion, this paper foregrounds it as a crucial element in modern environmental politics. On the substantive level, and using insights from science and technology studies, especially a slightly modified actor-network framework, I describe the emergence and consolidation of a Zionist network of abundance, immigration, and colonization in Palestine between 1918 and 1948. The essential argument here is that water abundance was constructed as fact, and became a political rallying point around which a techno-political network emerged that included a great number of elements. To name just a few, the following were enrolled in the service of such a network: geologists, geophysicists, Zionist settlement experts, Zionist organizations, political and technical categories of all sorts, Palestinians as the negated others, Palestinian revolts in search of political rights, the British Mandate authorities, the hydrological system of Palestine, and the absorptive capacity of Palestine, among others. The point was to successfully articulate these disparate elements into a network that seeks opening Palestine for Jewish immigration, redefining Palestinian geography and history through Judeo-Christian Biblical narratives, and, in the process, de-legitimizing political Palestinian presence in historic Palestine.

  5. An Abundance Analysis of Two Carbon-Rich Proto-Planetary Nebulae: IRAS Z02229+6208 And IRAS 07430+1115

    NASA Technical Reports Server (NTRS)

    Reddy, Bacham E.; Bakker, Eric J.; Hrivnak, Bruce J.

    1999-01-01

    In this paper, we present an LTE abundance analysis of two new proto-planetary nebulae, IRAS Z02229 + 6208 and IRAS 07430 + 1115, based on high-resolution (R approximately equal 55,000) optical echelle spectra. Results show that both stars are metal-poor ([Fe/H] = -0.5) and overabundant in C, N, and s-process elements. The average elemental abundances are [C/Fe] = +0.8, [N/Fe] = +1.2, and [s-process/Fe] = +1.4 for IRAS Z02229 + 6208, and [C/Fe] = +0.6, [N/Fe] = +0.4, and [s-process/Fe] = +1.6 for IRAS 07430+ 1115. These abundances suggest that the stars have experienced nucleo-synthesis on the asymptotic giant branch (AGB), and the resultant products of CNO, 3alpha, and s-process reactions were brought to the photosphere during shell flashes and deep mixing episodes during the AGB phase of their evolution. Of major significance is the measurement of a high Li abundance in both stars, log epsilon(Li) approximately equal 2.3 and 2.4 for IRAS Z02229 + 6208 and IRAS 07430 + 1115, respectively. This may be the result of hot bottom burning, below the deep convective zone. We also present an analysis of the circumstellar molecular (C2 and CN) and atomic (Na I and K I) absorption spectra of both stars. We derive rotational temperatures, column densities, and envelope expansion velocities using molecular C2 Phillips and CN Red system bands. The values derived for expansion velocities, 8-14 km/s, are typical of the values found for post-AGB stars. IRAS 07430+ 1115 is unusual in that it shows P Cygni-shaped C2 emission profiles in the spectra of the circumstellar envelope. A minimum distance for IRAS Z02229+6208, determined from interstellar Na I lines, suggests that it is evolved from an intermediate-mass star. Including these two stars, the number of post-AGB stars for which clear C, N, and s-process elemental overabundances are found rises to eight. IRAS Z02229 + 6208 is known to possess the 21 micron emission feature in its mid-infrared spectrum; these results support the

  6. Adding the s-Process Element Cerium to the APOGEE Survey: Identification and Characterization of Ce II Lines in the H-band Spectral Window

    NASA Astrophysics Data System (ADS)

    Cunha, Katia; Smith, Verne V.; Hasselquist, Sten; Souto, Diogo; Shetrone, Matthew D.; Allende Prieto, Carlos; Bizyaev, Dmitry; Frinchaboy, Peter; García-Hernández, D. Anibal; Holtzman, Jon; Johnson, Jennifer A.; Jőnsson, Henrik; Majewski, Steven R.; Mészáros, Szabolcs; Nidever, David; Pinsonneault, Mark; Schiavon, Ricardo P.; Sobeck, Jennifer; Skrutskie, Michael F.; Zamora, Olga; Zasowski, Gail; Fernández-Trincado, J. G.

    2017-08-01

    Nine Ce II lines have been identified and characterized within the spectral window observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey (between λ1.51 and 1.69 μm). At solar metallicities, cerium is an element that is produced predominantly as a result of the slow capture of neutrons (the s-process) during asymptotic giant branch stellar evolution. The Ce II lines were identified using a combination of a high-resolution (R=λ /δ λ ={{100,000}}) Fourier Transform Spectrometer (FTS) spectrum of α Boo and an APOGEE spectrum (R = 22,400) of a metal-poor, but s-process enriched, red giant (2M16011638-1201525). Laboratory oscillator strengths are not available for these lines. Astrophysical gf-values were derived using α Boo as a standard star, with the absolute cerium abundance in α Boo set by using optical Ce II lines that have precise published laboratory gf-values. The near-infrared Ce II lines identified here are also analyzed, as consistency checks, in a small number of bright red giants using archival FTS spectra, as well as a small sample of APOGEE red giants, including two members of the open cluster NGC 6819, two field stars, and seven metal-poor N- and Al-rich stars. The conclusion is that this set of Ce II lines can be detected and analyzed in a large fraction of the APOGEE red giant sample and will be useful for probing chemical evolution of the s-process products in various populations of the Milky Way.

  7. The Diverse Origins of Neutron-capture Elements in the Metal-poor Star HD 94028: Possible Detection of Products of I-Process Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Karakas, Amanda I.; Pignatari, Marco; Herwig, Falk

    2016-04-01

    We present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H] = -1.62 ± 0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe] = +0.79 ± 0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe] = +0.22 ± 0.12), including unusually large molybdenum ([Mo/Fe] = +0.97 ± 0.16) and ruthenium ([Ru/Fe] = +0.69 ± 0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe] = -0.06 ± 0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99 ± 0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (I process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the I process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the I process may have been common in the early Galaxy. These data are associated with Program 072.B-0585(A), PI. Silva. Some data presented in this paper were obtained from the Barbara A. Mikulski Archive for Space Telescopes (MAST). The Space Telescope Science Institute is

  8. Are C1 chondrites chemically fractionated - A trace element study

    NASA Technical Reports Server (NTRS)

    Ebihara, M.; Wolf, R.; Anders, E.

    1982-01-01

    Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for a large variety of elements, including rare earths. The sample processing is described, including the irradiation, chemical procedure, rare earths separation, counting techniques, radiochemical purity check, and chemical yields. The results of consistency checks on a number of elements are discussed. Abundances for siderophiles, volatiles, and rare earths are presented and discussed. Tests are presented for fractionation of rare earths and other refractories, compositional uniformity of C1's, and interelement correlations. There is no conclusive evidence for nebular fractionation affecting C1's. Three fractionation-prone rare earths have essentially the same relative abundances in C1's and all other chondrite classes, and hence are apparently not fractionated in C1's.

  9. Spectroscopic Analyses of Neutron Capture Elements in Open Clusters

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia E.

    The evolution of elements as a function or age throughout the Milky Way disk provides strong constraints for galaxy evolution models, and on star formation epochs. In an effort to provide such constraints, we conducted an investigation into r- and s-process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 near infrared survey. To obtain data for neutron capture abundance analysis, we conducted a long-term observing campaign spanning three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-meter telescope and Sandiford Cass Echelle Spectrograph (SES, R(lambda/Deltalambda) ˜60,000). The SES provides a wavelength range of ˜1400 A, making it uniquely suited to investigate a number of other important chemical abundances as well as the neutron capture elements. For this study, we derive abundances for 18 elements covering four nucleosynthetic families- light, iron-peak, neutron capture and alpha-elements- for ˜30 open clusters within 6 kpc of the Sun with ages ranging from ˜80 Myr to ˜10 Gyr. Both equivalent width (EW) measurements and spectral synthesis methods were employed to derive abundances for all elements. Initial estimates for model stellar atmospheres- effective temperature and surface gravity- were provided by the APOGEE data set, and then re-derived for our optical spectra by removing abundance trends as a function of excitation potential and reduced width log(EW/lambda). With the exception of Ba II and Zr I, abundance analyses for all neutron capture elements were performed by generating synthetic spectra from the new stellar parameters. In order to remove molecular contamination, or blending from nearby atomic features, the synthetic spectra were modeled by a best-fit Gaussian to the observed data. Nd II shows a slight enhancement in all cluster stars, while other neutron capture elements follow solar abundance trends. Ba II shows a large cluster-to-cluster abundance spread

  10. The relative abundances of Sn, Te, Xe, Ba and Ce. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Krombel, K. E.

    1983-01-01

    Elements with even atomic number (Z) in the interval 50 or = Z or = 58 were resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO-3 satellite. Their relative abundances were compared with the results expected from pure r-process material, pure s-process material, and solar system material, both with and without a modification due to possible first ionization potential effects. Such effects may be the result of the preferential acceleration, and hence enhancement in the cosmic rays, of those elements having low first ionization potentials. Measurements were found to be inconsistent with pure r-process material at the greater than 98% confidence level whether or not the first ionization potential adjustments are made.

  11. Al-26, Pu-244, Ti-50, REE, and trace element abundances in hibonite grains from CM and CV meteorites

    NASA Technical Reports Server (NTRS)

    Fahey, A. J.; Mckeegan, K. D.; Zinner, E.; Goswami, J. N.

    1987-01-01

    Hibonites from the CM meteorites Murchison, Murray, and Cold Bokkeveld, and hibonites and Ti-rich pyroxene from the CV chondrite Allende are studied. Electron microprobe measurements of major element concentrations and track and ion probe measurements of Mg and Ti isotopic ratios, rare earth elements (REEs), and trace element abundances are analyzed. Correlations between isotopic anomalies in Ti, Al-26, Pu-244, and Mg-26(asterisk) are examined. Ti isotopic anomalies are compared with REE and trace element abundance patterns. Reasons for the lack of Al-26 in the hibonites are investigated and discussed. It is observed that there is no correlation between the Ti isotopic compositions, and the presence of Mg-26(asterisk), Pu-244, and REE and trace element patterns in individual hibonite samples. The data reveal that hibonites are not interstellar dust grains but formed on a short time scale and in localized regions of the early solar system.

  12. Elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, M.; Zhicheng Hu.

    1993-09-07

    An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO[sub 2] in the regenerator off gas stream to elemental sulfur in the presence of a catalyst. 4 figures.

  13. Elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, Maria; Hu, Zhicheng

    1993-01-01

    An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO.sub.2 -containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO.sub.2 to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO.sub.2 in the regenerator off gas stream to elemental sulfur in the presence of a catalyst.

  14. High spatial resolution spectroscopy of Tycho’s SNR with Chandra

    NASA Astrophysics Data System (ADS)

    Guo, Yun-Dong; Yang, Xue-Juan

    2017-02-01

    We present high spatial resolution X-ray spectroscopy of Tycho’s supernova remnant (SNR) using observational data from Chandra. The whole remnant was divided into 26 × 27 regions, with each of them covering 20\\prime\\prime × 20\\prime\\prime. We selected 536 pixels with enough events to generate spectra and fit them with an absorbed two component non-equilibrium ionization model. We obtained maps of absorbing column density, weight-averaged temperature, ionization age and abundances for O, Ne, Mg, Si, S and Fe, with emission used to determine the weight. The abundance maps and the finding that Fe abundance is not correlated with any other element suggest that Fe is located at a smaller radius than other elements, supporting the onion shell model with emission from more massive elements peaking more toward the center. A tight correlation between Si and S abundances support both Si and S coming from explosive O-burning and/or incomplete Si-burning. O and Ne abundances show no correlation with any other element. Considering that O, Ne and Mg are all synthesized in the same process (C/Ne-burning), we suggest that O/Ne/Mg might mix well with other elements during the explosion of the supernova and the expansion of the SNR.

  15. HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance.

    PubMed

    Wakeford, Hannah R; Sing, David K; Kataria, Tiffany; Deming, Drake; Nikolov, Nikolay; Lopez, Eric D; Tremblin, Pascal; Amundsen, David S; Lewis, Nikole K; Mandell, Avi M; Fortney, Jonathan J; Knutson, Heather; Benneke, Björn; Evans, Thomas M

    2017-05-12

    A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted a detailed atmospheric study of the transiting Neptune-mass exoplanet HAT-P-26b. We detected prominent H 2 O absorption bands with a maximum base-to-peak amplitude of 525 parts per million in the transmission spectrum. Using the water abundance as a proxy for metallicity, we measured HAT-P-26b's atmospheric heavy element content ([Formula: see text] times solar). This likely indicates that HAT-P-26b's atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime, with little contamination from metal-rich planetesimals. Copyright © 2017, American Association for the Advancement of Science.

  16. The production of transuranium elements by the r-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Goriely, S.; Martínez Pinedo, G.

    2015-12-01

    The production of super-heavy transuranium elements by stellar nucleosynthesis processes remains an open question. The most promising process that could potentially give rise to the formation of such elements is the so-called rapid neutron-capture process, or r-process, known to be at the origin of approximately half of the A > 60 stable nuclei observed in nature. However, despite important efforts, the astrophysical site of the r-process remains unidentified. Here, we study the r-process nucleosynthesis in material that is dynamically ejected by tidal and pressure forces during the merging of binary neutron stars. Neutron star mergers could potentially be the dominant r-process site in the Galaxy, but also due to the extreme neutron richness found in such environment, could potentially synthesise super-heavy elements. R-process nucleosynthesis during the decompression is known to be largely insensitive to the detailed astrophysical conditions because of efficient fission recycling, producing a composition that closely follows the solar r-abundance distribution for nuclei with mass numbers A > 140. During the neutron irradiation, nuclei up to charge numbers Z ≃ 110 and mass number A ≃ 340 are produced, with a major peak production at the N = 184 shell closure, i.e. around A ≃ 280. Super-heavy nuclei with Z > 110 can hardly be produced due to the efficient fission taking place along those isotopic chains. Long-lived transuranium nuclei are inevitably produced by the r-process. The predictions concerning the production of transuranium nuclei remain however very sensitive to the predictions of fission barrier heights for such super-heavy nuclei. More nuclear predictions within different microscopic approaches are needed.

  17. HAT-P-26b: A Neptune-mass Exoplanet with Primordial Solar Heavy Element Abundance

    NASA Astrophysics Data System (ADS)

    Wakeford, Hannah R.; Sing, David K.; Kataria, Tiffany; Deming, Drake; Nikolov, Nikolay; Lopez, Eric; Tremblin, Pascal; Skalid Amundsen, David; Lewis, Nikole K.; Mandell, Avi; Fortney, Jonathan J.; Knutson, Heather; Benneke, Björn; Evans, Tom M.

    2017-01-01

    A trend in giant planet mass and atmospheric heavy elemental abundance was first noted last century from observations of planets in our own solar system. These four data points from Jupiter, Saturn, Uranus, and Neptune have served as a corner stone of planet formation theory. Here we add another point in the mass-metallicity trend from a detailed observational study of the extrasolar planet HAT-P-26b, which inhabits the critical mass regime near Neptune and Uranus. Neptune-sized worlds are among the most common planets in our galaxy and frequently exist in orbital periods very different from that of our own solar system ice giants. Atmospheric studies are the principal window into these worlds, and thereby into their formation and evolution, beyond those of our own solar system. Using the Hubble Space Telescope and Spitzer, from the optical to the infrared, we conducted a detailed atmospheric study of the Neptune-mass exoplanet HAT-P-26b over 0.5 to 4.5 μm. We detect prominent H2O absorption at 1.4 μm to 525 ppm in the atmospheric transmission spectrum. We determine that HAT-P-26b’s atmosphere is not rich in heavy elements (≈1.8×solar), which goes distinctly against the solar system mass-metallicity trend. This likely indicates that HAT-P-26b’s atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime with little contamination from metal-rich planetesimals.

  18. An upper limit on the sulphur abundance in HE 1327-2326

    NASA Astrophysics Data System (ADS)

    Bonifacio, P.; Caffau, E.; Venn, K. A.; Lambert, D. L.

    2012-08-01

    Context. Star HE 1327-2326 is a unique object, with the lowest measured iron abundance ([Fe/H] ~ -6) and a peculiar chemical composition that includes large overabundances of C, N, and O with respect to iron. One important question is whether the chemical abundances in this star reflect the chemical composition of the gas cloud from which it was formed or if they have been severely affected by other processes, such as dust-gas winnowing. Aims: We measure or provide an upper limit to the abundance of the volatile element sulphur, which can help to discriminate between the two scenarios. Methods: We observed HE 1327-2326 with the high resolution infra-red spectrograph CRIRES at the VLT to observe the S i lines of Multiplet 3 at 1045 nm. Results: We do not detect the S i line. A 3σ upper limit on the equivalent width (EW) of any line in our spectrum is EW < 0.66 pm. Using either one-dimensional static or three-dimensional hydrodynamical model-atmospheres, this translates into a robust upper limit of [S/H] < -2.6. Conclusions: This upper limit does not provide conclusive evidence for or against dust-gas winnowing, and the evidence coming from other elements (e.g., Na and Ti) is also inconclusive or contradictory. The formation of dust in the atmosphere versus an origin of the metals in a metal-poor supernova with extensive "fall-back" are not mutually exclusive. It is possible that dust formation distorts the peculiar abundance pattern created by a supernova with fall-back, thus the abundance ratios in HE 1327-2326 may be used to constrain the properties of the supernova(e) that produced its metals, but with some caution. Based on spectra obtained with CRIRES at the 8.2 m Antu ESO telescope, programme 386.D-0095.

  19. Heavy Element Abundances in NGC 5846

    NASA Technical Reports Server (NTRS)

    Jones, Christine

    2000-01-01

    In this paper we analyze the diffuse X-ray coronae surrounding the elliptical galaxy NGC 5846, combining measurements from two observatories, ROSAT and the Advanced Satellite for Cosmology and Astrophysics. We map the gas temperature distribution and find a central cool region within an approximately isothermal gas halo extending to a radius of about 50 kpc and evidence for a temperature decrease at larger radii. With a radially falling temperature profile, the total mass converges to (9.6 +/- 1.0) x 10(exp 12) solar mass at 230 kpc radius. This corresponds to a total mass to blue light ratio of 53 +/- 5 solar mass/solar luminosity. As in other early type galaxies, the gas mass is only a few percent of the total mass. Using the spectroscopic measurements, we also derive radial distributions for the heavy elements silicon and iron and find that the abundances of both decrease with galaxy radius. The mass ratio of Si to Fe lies between the theoretical predictions for element production in SN Ia and SN II, suggesting an important role for SN Ia, as well as SN II, for gas enrichment in ellipticals. Using the 2 SN la yield of Si, we set an upper limit of 0.012 h(sup 2, sub 50) solar neutrino units (SNU) for the SN Ia rate at radii >50 kpc, which is independent of possible uncertainties in the iron L-shell modeling. We compare our observations with the theoretical predictions for the chemical evolution of ellipticals. We conclude that the metal content in stars, if explained by the star formation duration, requires a significant decline in the duration of star formation with galaxy radius, ranging from 1 Gyr at the center to 0.01 Gyr at 100 kpc radius. Alternatively, the decline in metallicity with galaxy radius may be caused by a similar drop with radius in the efficiency of star formation. Based on the Si and Fe measurements presented in this paper, we conclude that the latter scenario is preferred unless a dependence of the SN Ia rate on stellar metallicity is invoked.

  20. Abundances of sodium, sulfur, and potassium in lunar volcanic glasses: Evidence for volatile loss during eruption

    NASA Technical Reports Server (NTRS)

    Delano, J. W.; Mcguire, J.

    1992-01-01

    Six varieties of lunar volcanic glass are known to occur within the Apollo 17 sample collection. Investigations have shown that 25 volatile elements are known to be concentrated on the exterior surfaces of individual volcanic glass spheres. Since bulk analyses of volcanic glass provide an integrated abundance of an element on and with the glass spherules, other methods must be relied on to determine the interior abundance of an element. The interior abundance of an element with a volcanic glass sphere establishes the abundance of that element in the melt at the time of quench. The current study is part of a comprehensive attempt to measure the abundance of three volatile elements (Na, S, and K) within representative spheres of the 25 varieties of lunar volcanic glass currently known to exist at the Apollo landing sites. Comparison of the measured abundances of these elements within the interiors of individual glasses with bulk analyses and crystalline mare basalts will furnish new constraints on the geochemical behavior of volatile elements during lunar mare volcanism.

  1. Carbon and nitrogen abundances determined from transition layer lines

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika; Mena-Werth, Jose

    1992-01-01

    The possibility of determining relative carbon, nitrogen, and silicon abundances from the emission-line fluxes in the lower transition layers between stellar chromospheres and coronae is explored. Observations for main-sequence and luminosity class IV stars with presumably solar element abundances show that for the lower transition layers Em = BT sup -gamma. For a given carbon abundance the constants gamma and B in this relation can be determined from the C II and C IV emission-line fluxes. From the N V and S IV lines, the abundances of these elements relative to carbon can be determined from their surface emission-line fluxes. Ratios of N/C abundances determined in this way for some giants and supergiants agree within the limits of errors with those determined from molecular bands. For giants, an increase in the ratio of N/C at B-V of about 0.8 is found, as expected theoretically.

  2. Complexity on Small Scales. III. Iron and α Element Abundances in the Carina Dwarf Spheroidal Galaxy

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; Grebel, Eva K.; Gilmore, Gerard F.; Wyse, Rosemary F. G.; Kleyna, Jan T.; Harbeck, Daniel R.; Wilkinson, Mark I.; Wyn Evans, N.

    2008-04-01

    We have obtained high-resolution spectroscopy of ten red giants in the Carina dwarf spheroidal (dSph) galaxy with the ultraviolet and visual echelle spectrograph at the European Southern Observatory Very Large Telescope in order to study the detailed chemical evolution of this Galactic satellite. Here we present the abundances of O, Na, Mg, Si, Ca, Ti, and Fe. By comparison of the derived iron abundances [Fe/H] with metallicities based on the well-established calcium triplet (CaT) calibration, [Fe/H]CaT, we show that the empirical CaT technique yields good agreement with the high-resolution data for [Fe/H] gsim 2 dex, but tends to deviate from these data at lower metallicities. With [Fe/H] ~ 1.7 dex the mean iron abundance of our targets is fully consistent with the peak metallicity of Carina as derived from medium-resolution spectroscopy and previous photometric studies, all calibrated onto iron via Galactic globular cluster scales. We identify two metal-poor stars with iron abundances of 2.72 and 2.50 dex. These stars are found to have enhanced [α/Fe] ratios similar to the elemental ratios of stars in the Milky Way halo. In this context, it is conceivable that the moderately metal-poor halo stars may originate from an early dSph accretion event. The bulk of the Carina red giants exhibit a depletion in the [α/Fe] abundance ratios with respect to the Galactic halo at a given metallicity. One of our targets with a moderately low [Fe/H] of 1.5 dex is considerably depleted in almost all of the α-elements by ~0.5 dex compared to the solar values. Such low values of the ratio of α-elements to iron can be produced by stochastical fluctuations in terms of an incomplete mixing of single type Ia and type II supernova (SN) events into the interstellar medium. Moreover, the system's slow star-formation (SF) rate grants sufficient time for SNe I to occur. Our derived chemical element ratios are consistent with the episodic and extended SF in Carina previously derived from

  3. n-capture elements in the Sculptor dwarf spheroidal galaxy

    NASA Astrophysics Data System (ADS)

    Skúladóttir, Ása

    2018-06-01

    Sculptor is a well studied dwarf galaxy in the Local Group, which is dominated by an old stellar population (>10 Gyr) and is therefore an ideal system to study early chemical evolution. With high-resolution VLT/FLAMES spectra, R~20,000, we are able to get accurate abundances of several n-capture elements in ~100 stars, from both the lighter n-capture elements (Y) as well as the heavier ones, both tracers of the s-process (e.g. Ba) and the r-process (e.g. Eu). I will discuss the similarities and differences in the n-capture elements in Sculptor and the Milky Way, as well as other dwarf galaxies.

  4. Anomalous 13C isotope abundances in C3S and C4H observed toward the cold interstellar cloud, Taurus Molecular Cloud-1.

    PubMed

    Sakai, Nami; Takano, Shuro; Sakai, Takeshi; Shiba, Shoichi; Sumiyoshi, Yoshihiro; Endo, Yasuki; Yamamoto, Satoshi

    2013-10-03

    We have studied the abundances of the (13)C isotopic species of C3S and C4H in the cold molecular cloud, Taurus Molecular Cloud-1 (Cyanopolyyne Peak), by radioastronomical observations of their rotational emission lines. The CCCS/(13)CCCS and CCCS/C(13)CCS ratios are determined to be >206 and 48 ± 15, respectively. The CC(13)CS line is identified with the aid of laboratory microwave spectroscopy, and the range of the CCCS/CC(13)CS ratio is found to be from 30 to 206. The abundances of at least two (13)C isotopic species of C3S are thus found to be different. Similarly, it is found that the abundances of the four (13)C isotopic species of C4H are not equivalent. The CCCCH/(13)CCCCH, CCCCH/C(13)CCCH, CCCCH/CC(13)CCH, and CCCCH/CCC(13)CH ratios are evaluated to be 141 ± 44, 97 ± 27, 82 ± 15, and 118 ± 23, respectively. Here the errors denote 3 times the standard deviation. These results will constrain the formation pathways of C3S and C4H, if the nonequivalence is caused during the formation processes of these molecules. The exchange reactions after the formation of these two molecules may also contribute to the nonequivalence. In addition, we have confirmed that the (12)C/(13)C ratio of some species are significantly higher than the interstellar elemental (12)C/(13)C ratio of 60-70. The observations of the (13)C isotopic species provide us with rich information on chemical processes in cold interstellar clouds.

  5. AKARI observations of brown dwarfs. IV. Effect of elemental abundances on near-infrared spectra between 1.0 and 5.0 μm

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sorahana, S.; Yamamura, I.

    2014-09-20

    The detection of the CO{sub 2} absorption band at 4.2 μm in brown dwarf spectra by AKARI has made it possible to discuss CO{sub 2} molecular abundance in brown dwarf atmospheres. In our previous studies, we found an excess in the 4.2 μm CO{sub 2} absorption band of three brown dwarf spectra, and suggested that these deviations were caused by high C and O elemental abundances in their atmospheres. To validate this hypothesis, we have constructed a set of models of brown dwarf atmospheres with various elemental abundance patterns, and we investigate the variations of the molecular composition and themore » thermal structure, and how they affect the near-infrared spectra between 1.0 and 5.0 μm. The 4.2 μm CO{sub 2} absorption band in some late-L and T dwarfs taken by AKARI is stronger or weaker than predicted by corresponding models with solar abundance. By comparing the CO{sub 2} band in the model spectra to the observed near-infrared spectra, we confirm possible elemental abundance variations among brown dwarfs. We find that the band strength is especially sensitive to O abundance, but C is also needed to reproduce the entire near-infrared spectra. This result indicates that both the C and O abundances should increase and decrease simultaneously for brown dwarfs. We find that a weaker CO{sub 2} absorption band in a spectrum can also be explained by a model with lower 'C and O' abundances.« less

  6. CHEMICAL ABUNDANCES OF MEMBER STARS IN THE OPEN CLUSTER NGC 2632 (PRAESEPE)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, X. L.; Chen, Y. Q.; Zhao, G.

    2015-11-15

    Based on high-resolution, high signal-to-noise ratio spectra, we present abundances of 17 elements (Fe, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Y, Zr, Ba, La) for six stars (one Am star, one F dwarf star, and four GK giant stars) and radial velocities for 18 proper-motion selected member stars in the open cluster NGC 2632. In the Am star, s-process elements Y and Ba are clearly overabundant, which may be considered as an indicator of a peculiar Am star. The average [Fe/H] is 0.16 ± 0.06 from four GK giant member stars, which is similarmore » to that of solar-type stars in the literature. As compared with dwarf stars, significant overabundances are found for Na, Mg, and Ba elements in our giant stars, which can be explained by the evolutionary effect. We also detect a star-to-star scatter of [Na/Fe] ratios among four giants which locate approximately at the same position in the CMD. Finally, we perform an analysis on the possible connection between the abundance and spatial structure of NGC 2632, but we find no inhomogeneous abundance among different clumps of stars in this cluster based on our limited sample.« less

  7. Light element geochemistry of the Apollo 16 site

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.; Kaplan, I. R.; Petrowski, C.; Chang, S.

    1975-01-01

    The abundance and isotopic composition of carbon, sulfur, and nitrogen, the abundance of helium and hydrogen, and the content of metallic iron are reported for lunar surface samples from the Apollo 16 landing site at Cayley-Descartes. The light elements show marked interstation variability at the site. The abundances in soils of C, N, He, and H are apparently controlled mainly by exposure to the solar wind, through implantation or stripping processes. Carbon abundances (but not observed isotopic distributions) are compatible with a model in which equilibrium is established after 10,000-100,000 yr between solar wind input and loss by proton stripping. Sulfur abundances in soils are apparently controlled by abundances in local country rocks, but the lunar S cycle is quite complex. A metallic iron component may have originated by solar wind reduction of lunar Fe(2+).

  8. Alternative Approach to Vehicle Element Processing

    NASA Technical Reports Server (NTRS)

    Huether, Jacob E.; Otto, Albert E.

    1995-01-01

    The National Space Transportation Policy (NSTP), describes the challenge facing today's aerospace industry. 'Assuring reliable and affordable access to space through U.S. space transportation capabilities is a fundamental goal of the U.S. space program'. Experience from the Space Shuttle Program (SSP) tells us that launch and mission operations are responsible for approximately 45 % of the cost of each shuttle mission. Reducing these costs is critical to NSTP goals in the next generation launch vehicle. Based on this, an innovative alternative approach to vehicle element processing was developed with an emphasis on reduced launch costs. State-of-the-art upgrades to the launch processing system (LPS) will enhance vehicle ground operations. To carry this one step further, these upgrade could be implemented at various vehicle element manufacturing sites to ensure system compatibility between the manufacturing facility and the launch site. Design center vehicle stand alone testing will ensure system integrity resulting in minimized checkout and testing at the launch site. This paper will addresses vehicle test requirements, timelines and ground checkout procedures which enable concept implementation.

  9. Evolutionary dynamics of selfish DNA explains the abundance distribution of genomic subsequences

    PubMed Central

    Sheinman, Michael; Ramisch, Anna; Massip, Florian; Arndt, Peter F.

    2016-01-01

    Since the sequencing of large genomes, many statistical features of their sequences have been found. One intriguing feature is that certain subsequences are much more abundant than others. In fact, abundances of subsequences of a given length are distributed with a scale-free power-law tail, resembling properties of human texts, such as Zipf’s law. Despite recent efforts, the understanding of this phenomenon is still lacking. Here we find that selfish DNA elements, such as those belonging to the Alu family of repeats, dominate the power-law tail. Interestingly, for the Alu elements the power-law exponent increases with the length of the considered subsequences. Motivated by these observations, we develop a model of selfish DNA expansion. The predictions of this model qualitatively and quantitatively agree with the empirical observations. This allows us to estimate parameters for the process of selfish DNA spreading in a genome during its evolution. The obtained results shed light on how evolution of selfish DNA elements shapes non-trivial statistical properties of genomes. PMID:27488939

  10. Spectroscopic abundance analyses of the 3He stars HD 185330 and 3 Cen A

    NASA Astrophysics Data System (ADS)

    Sadakane, Kozo; Nishimura, Masayoshi

    2018-04-01

    Abundances of 21 elements in two 3He stars, HD 185330 and 3 Cen A, have been analysed relative to the well-studied sharp-lined B3 V star ι Her. Six elements (P, Ti, Mn, Fe, Ni, and Br) are over-abundant in these two peculiar stars, while six elements (C, O, Mg, Al, S, and Cl) are under-abundant. Absorption lines of the two rarely observed heavy elements Br II and Kr II are detected in both stars and these elements are both over-abundant. The centroid wavelengths of the Ca II infrared triplet lines in these stars are redshifted relative to those lines in ι Her and the presence of heavy isotopes of Ca (mass number 44-46) in these two stars is confirmed. In spite of these similarities, there are several remarkable differences in abundance pattern between these two stars. N is under-abundant in HD 185330, as in many Hg-Mn stars, while it is significantly over-abundant in 3 Cen A. P and Ga are both over-abundant in 3 Cen A, while only P is over-abundant and no trace of absorption line of Ga II can be found in HD 185330. Large over-abundances of Kr and Xe are found in both stars, while the abundance ratio Kr/Xe is significantly different between them (-1.4 dex in HD 185330 and +1.2 dex in 3 Cen A). Some physical explanations are needed to account for these qualitative differences.

  11. Spectroscopic abundance analyses of the 3He stars HD 185330 and 3 Cen A

    NASA Astrophysics Data System (ADS)

    Sadakane, Kozo; Nishimura, Masayoshi

    2018-06-01

    Abundances of 21 elements in two 3He stars, HD 185330 and 3 Cen A, have been analysed relative to the well-studied sharp-lined B3 V star ι Her. Six elements (P, Ti, Mn, Fe, Ni, and Br) are over-abundant in these two peculiar stars, while six elements (C, O, Mg, Al, S, and Cl) are under-abundant. Absorption lines of the two rarely observed heavy elements Br II and Kr II are detected in both stars and these elements are both over-abundant. The centroid wavelengths of the Ca II infrared triplet lines in these stars are redshifted relative to those lines in ι Her and the presence of heavy isotopes of Ca (mass number 44-46) in these two stars is confirmed. In spite of these similarities, there are several remarkable differences in abundance pattern between these two stars. N is under-abundant in HD 185330, as in many Hg-Mn stars, while it is significantly over-abundant in 3 Cen A. P and Ga are both over-abundant in 3 Cen A, while only P is over-abundant and no trace of absorption line of Ga II can be found in HD 185330. Large over-abundances of Kr and Xe are found in both stars, while the abundance ratio Kr/Xe is significantly different between them (-1.4 dex in HD 185330 and +1.2 dex in 3 Cen A). Some physical explanations are needed to account for these qualitative differences.

  12. The Abundances of the Fe Group Elements in Three Early B Stars in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Peters, G. J.; Adelman, S. J.

    2005-12-01

    The photospheric abundances of V, Cr, and Fe have been determined for three sharp-lined early B stars in the Large Magellanic Cloud using FUV spectra obtained from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Kurucz LTE model atmosphere/spectrum synthesis codes ATLAS9/SYNTHE. The program stars include NGC1818/D1, NGC2004/B15, and NGC2004/B30 (star designations are from Robertson 1974, A&AS, 15, 261). The calculations were carried through with model parameters close to those adopted by Korn et al. (2000, A&A, 353, 655). Values of Teff, log g, ξ T, and v sin I are 25000/4.0/0/30, 20000/3.1/6/25, and 23500/3.3/14/30 for NGC1818/D1, NGC2004/B15, and NGC2004/B30, respectively. The abundances quoted below are in sequence for the latter stars. The vanadium abundances, [V/H], determined from V III λ λ 1150,1152 (UV 2), are -0.6, -0.9, and -0.9 dex. Cr was determined from Cr III λ λ 1118,1136. Values of -0.5, -0.8, and -0.7 dex were found. Uncertainties in the V and Cr abundances are ˜0.3 dex. The Fe abundance is primarily from 7 lines of Fe III (UV 1) in the region λ λ 1122-32. Values are -0.8±0.3, ˜-1.1, and -0.4±0.3. Since there is no evidence for N enhancement in the program stars ([N/H] ˜ -0.9, -1.0, and -0.6 from the N III doublet at 1183,1184 Å) the photospheric abundances have probably not been altered by mixing of processed material from the star's interior and the derived abundances represent pristine values for the two young clusters in the LMC. It should be noted that the N and Fe abundances derived for NGC1818/D1 are about 0.5 dex lower than those determined by Korn et al. from much weaker optical lines. We will discuss possible reasons for the discrepancy. The generally low abundances for the Fe group elements in these young cluster B stars imply that supernova activity has been minimal in the regions of the LMC in which the stars were formed. GJP appreciates support from NASA grant NAG5-13212.

  13. (F)UV Spectroscopy of K648: Abundance Determination of Trace Elements

    NASA Astrophysics Data System (ADS)

    Mohamad-Yob, S. J.; Ziegler, M.; Rauch, T.; Werner, K.

    2010-11-01

    We present preliminary results of an ongoing spectral analysis of K 648, the central star of the planetary nebula Ps 1, based on high resolution FUV spectra. K 648, in M 15 is one of only four known PNe in globular clusters. The formation of this post-AGB object in a globular cluster is still unclear. Our aim is to determine Teff, log g, and the abundances of trace elements, in order to improve our understanding of post-AGB evolution of extremely metal-poor stars, especially PN formation in globular clusters. We analyzed FUSE, HST/STIS, and HST/FOS observations. A grid of stellar model atmospheres was calculated using the Tübingen NLTE Model Atmosphere Package (TMAP).

  14. \\Space: A new code to estimate \\temp, \\logg, and elemental abundances

    NASA Astrophysics Data System (ADS)

    Boeche, C.

    2016-09-01

    \\Space is a FORTRAN95 code that derives stellar parameters and elemental abundances from stellar spectra. To derive these parameters, \\Space does not measure equivalent widths of lines nor it uses templates of synthetic spectra, but it employs a new method based on a library of General Curve-Of-Growths. To date \\Space works on the wavelength range 5212-6860 Å and 8400-8921 Å, and at the spectral resolution R=2000-20000. Extensions of these limits are possible. \\Space is a highly automated code suitable for application to large spectroscopic surveys. A web front end to this service is publicly available at http://dc.g-vo.org/SP_ACE together with the library and the binary code.

  15. CNO abundances in the quintuplet cluster M supergiant 5-7

    NASA Technical Reports Server (NTRS)

    Ramirez, S. V.; Sellgren, K.; Blum, R.; Terndrup, D. M.

    2002-01-01

    We present and analyze infrared spectra of the supergiant VR 5-7, in the Quintuplet cluster 30 pc from the Galactic center. Within the uncertainties, the [C/H],[N/H], and [O/H] abundances in this star are equal of Ori, a star which exhibits mixing of CNO processed elements, but distinct from the abundance patterns in IRS 7.

  16. Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.

    1989-01-01

    Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis facility at the National Synchrotron Light Source presently underway should increase the range of detectable elements and permit the analysis of smaller samples. In addition the Advanced Photon Source will be commissioned at Argonne National Laboratory in 1995. This 7 to 8 GeV positron storage ring, specifically designed for high-energy undulator and wiggler insertion devices, will be an ideal source for an x ray microprobe with one micron spatial resolution and better than 100 ppb elemental sensitivity for most elements. Thus trace element analysis of individual micron-sized grains should be possible by the time of the comet nucleus sample return mission.

  17. Heavy Elements and Cool Stars

    NASA Technical Reports Server (NTRS)

    Wahlgren, Glenn M.; Carpenter, Kenneth G.; Norris, Ryan P.

    2008-01-01

    We report on progress in the analysis of high-resolution near-IR spectra of alpha Orionis (M2 Iab) and other cool, luminous stars. Using synthetic spectrum techniques, we search for atomic absorption lines in the stellar spectra and evaluate the available line parameter data for use in our abundance analyses. Our study concentrates on the post iron-group elements copper through zirconium as a means of investigating the slow neutron-capture process of nucleosynthesis in massive stars and the mechanisms that transport recently processed material up into the photospheric region. We discuss problems with the atomic data and model atmospheres that need to be addressed before theoretically derived elemental abundances from pre-supernova nucleosynthesis calculations can be tested by comparison with abundances determined from observations of cool, massive stars.

  18. Revisiting Zirconium: New Abundance Determinations with Improved Oscillator Strengths

    NASA Astrophysics Data System (ADS)

    Burris, Debra L.; Jones, M.; Nichols, R.

    2006-12-01

    The element Zirconium is produced via neutron capture (n-capture). It resides in the mass range where there is uncertainty about the production mechanism at early time. The rapid n-capture process (r-process) was believed to be responsible for the production, but no study (Burris et al 2000, Gilroy et al 1988 and others) has been able to successfully use the r-process to reproduce the abundance signature for elements in this mass range for metal-poor halo stars. It has been suggested (Sneden and Cowan 2003) that there may be an undiscovered component to the r-process. New transition probabilities for Zr II have been reported by Malcheva et al (2006). We utilize these values to make new abundance determinations for Zr in the Sun and the metal-poor halo star BD +17 3248. This work is supported in part by the AAS Small Grant Program, the Arkansas Space Grant Consortium and the UCA Undergraduate Research Council.

  19. Trace element abundances in megacrysts and their host basalts - Constraints on partition coefficients and megacryst genesis

    NASA Technical Reports Server (NTRS)

    Irving, A. J.; Frey, F. A.

    1984-01-01

    Rare earth and other trace element abundances are determined in megacrysts of clinopyroxene, orthopyroxene, amphibole, mica, anorthoclase, apatite and zircon, as well as their host basalts, in an effort to gather data on mineral/melt trace element partitioning during the high pressure petrogenesis of basic rocks. Phase equilibria, major element partitioning and isotopic ratio considerations indicate that while most of the pyroxene and amphibole megacrysts may have been in equilibrium with their host magmas at high pressures, mica, anorthoclase, apatite, and zircon megacrysts are unlikely to have formed in equilibrium with their host basalts. It is instead concluded that they were precipitated from more evolved magmas, and have been mixed into their present hosts.

  20. Interstellar abundances - Gas and dust

    NASA Technical Reports Server (NTRS)

    Field, G. B.

    1974-01-01

    Data on abundances of interstellar atoms, ions and molecules in front of zeta Oph are assembled and analyzed. The gas-phase abundances of at least 11 heavy elements are significantly lower, relative to hydrogen, than in the solar system. The abundance deficiencies of certain elements correlate with the temperatures derived theoretically for particle condensation in stellar atmospheres or nebulae, suggesting that these elements have condensed into dust grains near stars. There is evidence that other elements have accreted onto such grains after their arrival in interstellar space. The extinction spectrum of zeta Oph can be explained qualitatively and, to a degree, quantitatively by dust grains composed of silicates, graphite, silicon carbide, and iron, with mantles composed of complex molecules of H, C, N, and O. This composition is consistent with the observed gas-phase deficiencies.

  1. Column abundance measurements of atmospheric hydroxyl at 45 deg S

    NASA Technical Reports Server (NTRS)

    Wood, S. W.; Keep, D. J.; Burnett, C. R.; Burnett, E. B.

    1994-01-01

    The first Southern Hemisphere measurements of the vertical column abundance of atmospheric hydroxyl (OH) have been obtained at Lauder, New Zealand (45 deg S) with a PEPSIOS instrument measuring the absorption of sunlight at 308 nm. The variation of column OH with solar zenith angle is similar to that measured at other sites. However average annual abundances of OH are about 20% higher than those found by similar measurements at 40 deg N. Minimum OH abundances about 10% less than average levels at 40 deg N, are observed during austral spring. The OH abundance abruptly increases by 30% in early summer and remains at the elevated level until late the following winter.

  2. Solar abundances as derived from solar energetic particles

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1989-01-01

    Recent studies have shown that there are well defined average abundances of heavy (Z above 2) solar energetic particles (SEPs), with variations in the acceleration and propagation producing a systematic flare-to-flare fractionation that depends on the charge per unit mass of the ion. Correcting the average SEP abundances for this fractionation yields SEP-derived coronal abundances for 20 elements. High-resolution SEP studies have also provided isotopic abundances for five elements. SEP-derived abundances indicate that elements with high first ionization potentials (greater than 10 eV) are depleted in the corona relative to the photosphere and provide new information on the solar abundance of C and Ne-22.

  3. Project VeSElkA: results of abundance analysis for HD 53929 and HD 63975

    NASA Astrophysics Data System (ADS)

    Ndiaye, M. L.; LeBlanc, F.; Khalack, V.

    2018-03-01

    Project VeSElkA (Vertical Stratification of Element Abundances) has been initiated with the aim to detect and study the vertical stratification of element abundances in the atmosphere of chemically peculiar stars. Abundance stratification occurs in hydrodynamically stable stellar atmospheres due to the migration of the elements caused by atomic diffusion. Two HgMn stars, HD 53929 and HD 63975 were selected from the VeSElkA sample and analysed with the aim to detect some abundance peculiarities employing the ZEEMAN2 code. We present the results of abundance analysis of HD 53929 and HD 63975 observed recently with the spectropolarimeter ESPaDOnS at Canada-France-Hawaii Telescope. Evidence of phosphorus vertical stratification was detected in the atmosphere of these two stars. In both cases, phosphorus abundance increases strongly towards the superficial layers. The strong overabundance of Mn found in stellar atmosphere of both stars confirms that they are HgMn type stars.

  4. DETECTION OF THE SECOND r-PROCESS PEAK ELEMENT TELLURIUM IN METAL-POOR STARS ,

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roederer, Ian U.; Lawler, James E.; Cowan, John J.

    2012-03-15

    Using near-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, we detect neutral tellurium in three metal-poor stars enriched by products of r-process nucleosynthesis, BD +17 3248, HD 108317, and HD 128279. Tellurium (Te, Z = 52) is found at the second r-process peak (A Almost-Equal-To 130) associated with the N = 82 neutron shell closure, and it has not been detected previously in Galactic halo stars. The derived tellurium abundances match the scaled solar system r-process distribution within the uncertainties, confirming the predicted second peak r-process residuals. These results suggest that tellurium ismore » predominantly produced in the main component of the r-process, along with the rare earth elements.« less

  5. Elemental abundance analyses with Complejo Astronomico. EL Leoncito REOSC echelle spectrograms. I. κ Cancri, HR 7245, and ξ Octantis

    NASA Astrophysics Data System (ADS)

    Pintado, O. I.; Adelman, S. J.

    1996-08-01

    Elemental abundances are derived for three sharp-lined stars κ Cnc, HR 7245, and ξ Oct using REOSC echelle spectrograms obtained at CASLEO. Comparisons are made with published equivalent widths. The derived abundances for κ Cnc and ξ Oct are slightly larger than those obtained with other high dispersion spectrographs. HR 7245 exhibits a pattern of abundance anomalies similar to other Mercury-Manganese stars. The spectra of the two HgMn stars in the λλ4640-5100 region exhibit an interesting and useful variety of lines which can be used to supplement analyses of the photographic region.

  6. Improved Yttrium and Zirconium Abundances in Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Violante, Renata; Biemont, E.; Cowan, J. J.; Sneden, C.

    2012-01-01

    Abstract We present new abundances of the lighter n-capture elements, Yttrium (Z=39) and Zirconium (Z=40) in the very metal poor, r-process rich stars BD+17 3248 and HD 221170. Very accurate abundances were obtained by use of the new transition probabilities for Y II published by Biémont et al. 2011, and Zr II by Malcheva et al. 2006, and by expanding the number of transitions employed for each element. For example, in BD+17 3248, we find log ɛπσιλον=-0.03 +/- 0.03 (σιγμα=0.15, from 23 lines) for Y II. As for Zr II, log ɛπσιλον = 0.65 +/- 0.03 (σɛγμα = 0.1, from 13 lines). The resulting abundance ratio is log ɛπσιλον [Y/Zr] = -0.68 +/- 0.05. The results for HD 221170 are in accord with those of BD+17 3248. The quantity of lines used to form the abundance means has increased significantly since the original studies of these stars, resulting in more trustworthy abundances. These observed abundance ratios are in agreement with an r-process-only value predicted from stellar models, but is under-abundant compared to an empirical model derived from direct analyses of meteoritic material. This ambiguity should stimulate further nucleosynthetic analysis to explain this abundance ratio. We would like to extend our gratitude to NSF grant AST-0908978 and the University of Texas Astronomy Department Rex G. Baker, Jr. Endowment for their financial support in this project.

  7. The new model of chemical evolution of r-process elements based on the hierarchical galaxy formation. I. Ba and Eu

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Komiya, Yutaka; Suda, Takuma; Yamada, Shimako

    2014-03-10

    We investigate the chemical enrichment of r-process elements in the early evolutionary stages of the Milky Way halo within the framework of hierarchical galaxy formation using a semi-analytic merger tree. In this paper, we focus on heavy r-process elements, Ba and Eu, of extremely metal-poor (EMP) stars and give constraints on their astronomical sites. Our models take into account changes of the surface abundances of EMP stars by the accretion of interstellar medium (ISM). We also consider metal-enrichment of intergalactic medium by galactic winds and the resultant pre-enrichment of proto-galaxies. The trend and scatter of the observed r-process abundances aremore » well reproduced by our hierarchical model with ∼10% of core-collapse supernovae in low-mass end (∼10 M {sub ☉}) as a dominant r-process source and the star formation efficiency of ∼10{sup –10} yr{sup –1}. For neutron star mergers as an r-process source, their coalescence timescale has to be ∼10{sup 7} yr, and the event rates ∼100 times larger than currently observed in the Galaxy. We find that the accretion of ISM is a dominant source of r-process elements for stars with [Ba/H] < –3.5. In this model, a majority of stars at [Fe/H] < –3 are formed without r-process elements, but their surfaces are polluted by the ISM accretion. The pre-enrichment affects ∼4% of proto-galaxies, and yet, is surpassed by the ISM accretion in the surface of EMP stars.« less

  8. Synthesis and Characterization of an Earth-Abundant Cu2BaSn(S,Se)4 Chalcogenide for Photoelectrochemical Cell Application.

    PubMed

    Shin, Donghyeop; Ngaboyamahina, Edgard; Zhou, Yihao; Glass, Jeffrey T; Mitzi, David B

    2016-11-17

    Cu 2 BaSnS 4-x Se x films consisting of earth-abundant metals have been examined for photocathode application. Films with different Se contents (i.e., Cu 2 BaSnS 4-x Se x with x ≤ 2.4) were synthesized using a cosputter system with post-deposition sulfurization/selenization annealing treatments. Each film adopts a trigonal P3 1 crystal structure, with progressively larger lattice constants and with band gaps shifting from 2.0 to 1.6 eV, as more Se substitutes for S in the parent compound Cu 2 BaSnS 4 . Given the suitable bandgap and earth-abundant elements, the Cu 2 BaSnS 4-x Se x films were studied as prospective photocathodes for water splitting. Greater than 6 mA/cm 2 was obtained under illumination at -0.4 V versus reversible hydrogen electrode for Pt/Cu 2 BaSnS 4-x Se x films with ∼60% Se content (i.e., x = 2.4), whereas a bare Cu 2 BaSnS 4-x Se x (x = 2.4) film yielded ∼3 mA/cm 2 at -0.4 V/RHE.

  9. Chemo-Dynamical Evolution of r-process Elements in the Local Group Galaxies

    NASA Astrophysics Data System (ADS)

    Hirai, Yutaka; Ishimaru, Yuhri; Saitoh, Takayuki R.; Fujii, Michiko S.; Hidaka, Jun; Kajino, Toshitaka

    The astrophysical site(s) of r-process is not yet identified over half a century. Astronomical high dispersion observations have shown that extremely metal-poor (EMP) stars in the Milky Way (MW) halo have large star-to-star dispersions in the abundance of r-process elements. Binary neutron star mergers (NSMs) are one of the most promising sites of r-process. However, several studies suggested that it is difficult to reproduce the dispersions by NSMs due to their long merger times and low rates. In this study, we performed a series of N-body/smoothed particle hydrodynamic simulations of dwarf galaxies. We show that NSMs can explain the dispersions with long merger times (˜100 Myr). We find that the metallicity of our simulated galaxies does not correlate with time in their early phase due to slow chemical enrichment. This slow chemical enrichment produces [Eu/Fe] distribution which is consistent with the observation. Our results suggest that stars in the MW halo formed with a low star formation rate of less than 10 - 3M ⊙ yr-1, which is common for typical dwarf galaxies in the MW. Our simulations support the scenario that early enrichment of the MW halo occurred in the framework of hierarchical structure formation.

  10. Elemental abundance analyses with Complejo Astronomico El Leoncito REOSC echelle spectrograms. IV. Extensions of nine previous analyses

    NASA Astrophysics Data System (ADS)

    Adelman, S. J.; Pintado, O. I.

    2000-02-01

    Using new CASLEO echelle spectrograms, we extended our elemental abundances of the sharp-lined Mercury-Manganese stars mu Lep, 14 Hya, kappa Cnc, HR 4487, HR 4817, 28 Her, and HR 7245, the closely related star 3 Cen A, and 7 Sex an A0 V star with Population I abundances, but with Population II star space motions. The lambda lambda 4500-6200 region contains a sufficient number of lines to derive high-quality abundances of these stars. For most stars, the new spectra provide additional lines for the analyses which improve their quality as well as help fill in the periodic table. Table~5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strabg.fr/Abstract.html}

  11. Stellar Abundances for Galactic Archaeology Database. IV. Compilation of stars in dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Suda, Takuma; Hidaka, Jun; Aoki, Wako; Katsuta, Yutaka; Yamada, Shimako; Fujimoto, Masayuki Y.; Ohtani, Yukari; Masuyama, Miyu; Noda, Kazuhiro; Wada, Kentaro

    2017-10-01

    We have constructed a database of stars in Local Group galaxies using the extended version of the SAGA (Stellar Abundances for Galactic Archaeology) database that contains stars in 24 dwarf spheroidal galaxies and ultra-faint dwarfs. The new version of the database includes more than 4500 stars in the Milky Way, by removing the previous metallicity criterion of [Fe/H] ≤ -2.5, and more than 6000 stars in the Local Group galaxies. We examined the validity of using a combined data set for elemental abundances. We also checked the consistency between the derived distances to individual stars and those to galaxies as given in the literature. Using the updated database, the characteristics of stars in dwarf galaxies are discussed. Our statistical analyses of α-element abundances show that the change of the slope of the [α/Fe] relative to [Fe/H] (so-called "knee") occurs at [Fe/H] = -1.0 ± 0.1 for the Milky Way. The knee positions for selected galaxies are derived by applying the same method. The star formation history of individual galaxies is explored using the slope of the cumulative metallicity distribution function. Radial gradients along the four directions are inspected in six galaxies where we find no direction-dependence of metallicity gradients along the major and minor axes. The compilation of all the available data shows a lack of CEMP-s population in dwarf galaxies, while there may be some CEMP-no stars at [Fe/H] ≲ -3 even in the very small sample. The inspection of the relationship between Eu and Ba abundances confirms an anomalously Ba-rich population in Fornax, which indicates a pre-enrichment of interstellar gas with r-process elements. We do not find any evidence of anti-correlations in O-Na and Mg-Al abundances, which characterizes the abundance trends in the Galactic globular clusters.

  12. Ring-laser gyroscope system using dispersive element(s)

    NASA Technical Reports Server (NTRS)

    Smith, David D. (Inventor)

    2010-01-01

    A ring-laser gyroscope system includes a ring-laser gyroscope (RLG) and at least one dispersive element optically coupled to the RLG's ring-shaped optical path. Each dispersive element has a resonant frequency that is approximately equal to the RLG's lasing frequency. A group index of refraction defined collectively by the dispersive element(s) has (i) a real portion that is greater than zero and less than one, and (ii) an imaginary portion that is less than zero.

  13. Highly Siderophile Element Abundances in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Jones, J. H.; Neal, C. R.; Ely, J. C.

    2001-01-01

    Critical evaluation of new and literature data for highly siderophile elements (HSE) in Martian (SNC) meteorites allows several first order conclusions to be drawn. (i) Re concentrations in SNC meteorites are nearly constant (within a factor of two) and do not correlate with rock type. Exceptions to this rule are Chassigny and Dar al Gani (DaG) 476, both of which are inferred to have experienced terrestrial Re contamination. (ii) Fractionations between Rh and Pd are small. Excluding Shergotty, the Rh/Pd ratio of the SNC suite is 0.22\\pm0.05. (iii) Os and Ir contents vary by about four orders of magnitude; and positive correlations with MgO, Cr, and Ni suggest that these variations are not controlled by sulfide fractionation. A possible exception is the orthopyroxenite ALH84001, whose HSE's (including Ni, which is compatible in opx) are very low. (iv) Zagami, Shergotty, and Nakhla have nearly identical HSE signatures. Shergotty and Zagami have experienced assimilation-fractional crystallization (AFC) and have "crustal" Sr and Nd isotopic signatures. Conversely, the Nakhla parent was a small degree partial melt of a depleted mantle that interacted little with the Martian crust. These observations suggest that "evolved" HSE signatures can be produced by either fractional crystallization or small degrees of partial melting. (v) Chassigny and other mafic SNC's have HSE signatures that are very distinct from those of Nakhla-Zagami-Shergotty. The HSE elemental ratios of mafic SNC's approach chondritic, implying that the Martian mantle has nearly chondritic relative abundances of the HSE's. (vi) This chondritic HSE signature is observed in SNC's of various ages, suggesting that this is an ancient feature that has not evolved over time. (vii) No correlation is observed between HSE's and signatures of crustal contamination (e.g., Sr isotopes), indicating that the HSE signatures of the SNC suite are not derived from the crust. (vii) The Ru/Pd for the SNC suite ratio is about

  14. Alpha-capture reaction rates for 22 Ne (α , n) via sub-Coulomb alpha-transfer and its effect on final abundances of s-process isotopes

    NASA Astrophysics Data System (ADS)

    Jayatissa, Heshani; Rogachev, Grigory; Koshchiy, Yevgeny; Goldberg, Vladilen; Hooker, Joshua; Hunt, Curtis; Magana, Cordero; Roeder, Brian; Saastamoinen, Antti; Spiridon, Alexandria; Upadhyayula, Sriteja; Trippella, Oscar

    2017-09-01

    The 22 Ne (α , n) reaction is a very important neutron source reaction for the slow neutron capture process (s-process) in asymptotic giant branch stars. These direct measurements are very difficult to carry out at the energy regimes of interest for astrophysics (Gamow energies) due to the extremely small reaction cross section. The large uncertainties introduced when extrapolating direct measurements at high energies down to the Gamow energies can be overcome by measuring the Asymptotic Normalization Coefficients (ANC) of the relevant states using α-transfer reactions at sub-Coulomb energies to reduce the optical model dependence. The study of the 22Ne(6Li,d) and 22Ne(7Li,t) reaction was carried out at the Cyclotron Institute at Texas A&M University. The α-ANC measurements for the near α-threshold resonances of 26Mg provide constraints for the 22Ne(α,n) reaction rate. The effect of this reaction rate on the final abundances of the s-process isotopes will be discussed.

  15. Neutron capture and stellar synthesis of heavy elements.

    PubMed

    Gibbons, J H; Macklin, R L

    1967-05-26

    The neutron buildup processes of heavy-element synthesis in stars have left us a number of tantalizing nuclear clues to the early history of solarsystem material. Considerable illumination of our past history has been achieved through studying the correlations between abundance and neutroncapture cross section. Measurement of these cross sections required the development of new techniques for measuring time of flight of pulsed neutron beams. A clear conclusion is that many of our heavy elements were produced inside stars, which can be thought of as giant fast reactors. Extensions of these capture studies have given a clearer picture of additional. violent processes which produced some heavy elements, particularly thorium and uranium. In addition, the correlations have been used for obtaining an independent measure of the time that has elapsed since the solar-system material was synthesized. Finally, data on capture cross section relative to abundance will enable us to determine rather accurately the solar-system abundances of gaseous, volatile, and highly segregated elements.

  16. Trek and ECCO: Abundance measurements of ultraheavy galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Westphal, Andrew J.

    2000-06-01

    Using the Trek detector, we have measured the abundances of the heaviest elements (with Z>70) in the galactic cosmic rays with sufficient charge resolution to resolve the even-Z elements. We find that the abundance of Pb compared to Pt is ~3 times lower than the value expected from the most widely-held class of models of the origin of galactic cosmic ray nuclei, that is, origination in a partially ionized medium with solar-like composition. The low abundance of Pb is, however, consistent with the interstellar gas and dust model of Meyer, Drury and Ellison, and with a source enriched in r-process material, proposed by Binns et al. A high-resolution, high-statistics measurement of the abundances of the individual actinides would distinguish between these models. This is the goal of ECCO, the Extremely Heavy Cosmic-ray Composition Observer, which we plan to deploy on the International Space Station. .

  17. Chemical Abundance Analysis of Moving Group W11450 (Latham 1)

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia E.; Martens, Kylee; Frinchaboy, Peter M.

    2016-12-01

    We present elemental abundances for all seven stars in Moving Group W11450 (Latham 1) to determine if they may be chemically related. These stars appear to be both spatially and kinematically related, but no spectroscopic abundance analysis exists in literature. Abundances for eight elements were derived via equivalent width analyses of high-resolution (R ˜ 60,000), high-signal-to-noise ratio (< {{S}}/{{N}}> ˜ 100) spectra obtained with the Otto Struve 2.1 m telescope and the Sandiford Echelle Spectrograph at McDonald Observatory. The large star-to-star scatter in metallicity, -0.55 ≤ [Fe/H] ≤slant 0.06 dex (σ = 0.25), implies these stars were not produced from the same chemically homogeneous molecular cloud, and are therefore not part of a remnant or open cluster as previously proposed. Prior to this analysis, it was suggested that two stars in the group, W11449 and W11450, are possible wide binaries. The candidate wide binary pair show similar chemical abundance patterns with not only iron but with other elements analyzed in this study, suggesting the proposed connection between these two stars may be real.

  18. Relationship between the Elemental Abundances and the Kinematics of Galactic-Field RR Lyrae Stars

    NASA Astrophysics Data System (ADS)

    Marsakov, V. A.; Gozha, M. L.; Koval, V. V.

    2018-01-01

    Data of our compiled catalog containing the positions, velocities, and metallicities of 415 RR Lyrae variable stars and the relative abundances [el/Fe] of 12 elements for 101 RR Lyrae stars, including four α elements (Mg, Ca, Si, and Ti), are used to study the relationships between the chemical and spatial-kinematic properties of these stars. In general, the dependences of the relative abundances of α elements on metallicity and velocity for the RR Lyrae stars are approximately the same as those for field dwarfs. Despite the usual claim that these stars are old, among them are representatives of the thin disk, which is the youngest subsystem of the Galaxy. Attention is called to the problem of lowmetallicity RR Lyrae stars. Most RR Lyrae stars that have the kinematic properties of thick disk stars have metallicities [Fe/H] < -1.0 and high ratios [α/Fe] ≈ 0.4, whereas only about 10% of field dwarfs belonging to the so-called "low-metallicity tail" have this chemical composition. At the same time, there is a sharp change in [α/Fe] in RR Lyrae stars belonging just to the thick disk, providing evidence for a long period of formation of this subsystem. The chemical compositions of SDSS J1707+58, V455 Oph, MACHO176.18833.411, V456 Ser, and BPSCS 30339-046 do not correspond to their kinematics.While the first three of these stars belong to the halo, according to their kinematics, the last two belong to the thick disk. It is proposed that they are all most likely extragalactic, but the possible appearance of some of them in the solar neighborhood as a result of the gravitational action of the bar on field stars cannot be ruled out.

  19. Ion processing element with composite media

    DOEpatents

    Mann, Nick R.; Tranter, Troy J.; Todd, Terry A.; Sebesta, Ferdinand

    2003-02-04

    An ion processing element employing composite media disposed in a porous substrate, for facilitating removal of selected chemical species from a fluid stream. The ion processing element includes a porous fibrous glass substrate impregnated by composite media having one or more active components supported by a matrix material of polyacrylonitrile. The active components are effective in removing, by various mechanisms, one or more constituents from a fluid stream passing through the ion processing element. Due to the porosity and large surface area of both the composite medium and the substrate in which it is disposed, a high degree of contact is achieved between the active component and the fluid stream being processed. Further, the porosity of the matrix material and the substrate facilitates use of the ion processing element in high volume applications where it is desired to effectively process a high volume flows.

  20. Ion processing element with composite media

    DOEpatents

    Mann, Nick R [Blackfoot, ID; Tranter, Troy J [Idaho Falls, ID; Todd, Terry A [Aberdeen, ID; Sebesta, Ferdinand [Prague, CZ

    2009-03-24

    An ion processing element employing composite media disposed in a porous substrate, for facilitating removal of selected chemical species from a fluid stream. The ion processing element includes a porous fibrous glass substrate impregnated by composite media having one or more active components supported by a matrix material of polyacrylonitrile. The active components are effective in removing, by various mechanisms, one or more constituents from a fluid stream passing through the ion processing element. Due to the porosity and large surface area of both the composite medium and the substrate in which it is disposed, a high degree of contact is achieved between the active component and the fluid stream being processed. Further, the porosity of the matrix material and the substrate facilitates use of the ion processing element in high volume applications where it is desired to effectively process a high volume flows.

  1. New experimental developments for s- and p-process research

    NASA Astrophysics Data System (ADS)

    Reifarth, R.; Ershova, O.; Glorius, J.; Göbel, K.; Langer, C.; Meusel, O.; Plag, R.; Schmidt, S.; Sonnabend, K.; Heil, M.

    2012-12-01

    Almost all of the heavy elements are produced via neutron-induced processes in a multitude of stellar production sites. The remaining minor part is produced via photon- and proton-induced reactions. The predictive power of the underlying stellar models is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. An important tool to determine such components is the comparison of observed with modeled abundance distributions based on improved nuclear physics input. The FRANZ facility at the Goethe University Frankfurt, which is currently under construction will provide unprecedented neutron fluxes and proton currents available for nuclear astrophysics. It will be possible to investigate important branchpoint nuclei of the s-process nucleosynthesis path and proton-induced reactions important for p-process modeling. At the GSI close to Darmstadt radioactive isotopes can be investigated in inverse kinematics. This allows experiments such as proton-induced cross section measurements using a heavy-ion storage ring or measurements of gamma-induced reactions using the Coulomb dissociation method. The future FAIR facility will allow similar experiments on very exotic nuclei, since orders of magnitude higher radioactive ions beams will be possible.

  2. Elemental abundance analyses with coadded Dominion Astrophysical Observatory spectrograms. II - The mercury-manganese stars 53 Tauri, Mu Leporis and Kappa Cancri

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.

    1987-01-01

    Elemental abundance analyses based on the coaddition of at least 10 2.4 A/mm Ila-O Dominion Astrophysical Observatory spectrograms have been performed for three mercury-manganese stars, 53 Tauri, Mu Leporis, and Kappa Cancri. These fine analyses show a greater degree of internal consistency than previous studies based on lower signal-to-noise data. Lines as weak as of order 3 mA are employed in these studies, and lines of atomic species not previously identified have been discovered. The status of 53 Tau as an anomalous member of this class is confirmed in that it lacks a Hg II 3984 A line even at the 2 mA level. Further, its surface gravity indicates it is less evolved than Mu Lep and Chi Cnc. Violations of the odd-even effect in the photospheric abundances of all three stars suggest that nonnuclear processes have operated in their atmospheres. Some of the values are substantially changed from their presumably initial solar values.

  3. The 20Ne(d,p) 21Ne Transfer Reaction in Relation to the s-Process Abundances

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nsangu, C. T.; Laird, A. M.; Parikh, A.

    2016-01-01

    A study of the Ne-20(d,p)Ne-21 transfer reaction was performed using the Quadrupole Dipole Dipole Dipole (Q3D) magnetic spectrograph in Garching, Germany. The experiment probed excitation energies in Ne-21 ranging from 6.9 MeV to 8.5 MeV. The aim was to investigate the spectroscopic information of Ne-21 within the Gamow window of core helium burning in massive stars. Further information in this region will help reduce the uncertainties on the extrapolation down to Gamow window cross sections of the O-17(alpha,gamma)Ne-21 reaction. In low metallicity stars, this reaction has a direct impact on s-process abundances by determining the fate of O-16 as eithermore » a neutron poison or a neutron absorber. The experiment used a 22-MeV deuteron beam, with intensities varying from 0.5-1 mu A, and an implanted target of Ne-20 of 7 mu g/cm(2) in 40 mu g/cm(2) carbon foils. Sixteen Ne-21 peaks have been identified in the E-x = 6.9-8.5 MeV range, of which only thirteen peaks correspond to known states. Only the previously-known E-x = 7.960 MeV state was observed within the Gamow window.« less

  4. UH cosmic rays and solar system material - The elements just beyond iron

    NASA Technical Reports Server (NTRS)

    Wefel, J. P.; Schramm, D. N.; Blake, J. B.

    1977-01-01

    The nucleosynthesis of cosmic-ray elements between the iron peak and the rare-earth region is examined, and compositional changes introduced by propagation in interstellar space are calculated. Theories on the origin of elements heavier than iron are reviewed, a supernova model of explosive nucleosynthesis is adopted for the ultraheavy (UH) cosmic rays, and computational results for different source distributions are compared with experimental data. It is shown that both the cosmic-ray data and the nucleosynthesis calculations are not yet of sufficient precision to pinpoint the processes occurring in cosmic-ray source regions, that the available data do provide boundary conditions for cosmic-ray nucleosynthesis, and that these limits may apply to the origin of elements in the solar system. Specifically, it is concluded that solar-system abundances appear to be consistent with a superposition of the massive-star core-helium-burning s-process plus explosive-carbon-burning synthesis for the elements from Cu to As and are explained adequately by the s- and r-processes for heavier elements.

  5. The Chelyabinsk Fall Highly Siderophile Element Abundance and 187Os/188Os Composition and Comparison with Ordinary and Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Day, J. M. D.; Corder, C. A.; Dhaliwal, J. K.; Liu, Y.; Taylor, L. A.

    2014-09-01

    New osmium isotope and highly siderophile element abundance data are presented for the Chelyabinsk ordinary chondrite fall (February 2013) and placed into context with new data for ordinary and carbonaceous chondrites.

  6. The origin of diverse α-element abundances in galaxy discs

    NASA Astrophysics Data System (ADS)

    Mackereth, J. Ted; Crain, Robert A.; Schiavon, Ricardo P.; Schaye, Joop; Theuns, Tom; Schaller, Matthieu

    2018-04-01

    Spectroscopic surveys of the Galaxy reveal that its disc stars exhibit a spread in [α/Fe] at fixed [Fe/H], manifest at some locations as a bimodality. The origin of these diverse, and possibly distinct, stellar populations in the Galactic disc is not well understood. We examine the Fe and α-element evolution of 133 Milky Way-like galaxies from the EAGLE simulation, to investigate the origin and diversity of their [α/Fe]-[Fe/H] distributions. We find that bimodal [α/Fe] distributions arise in galaxies whose gas accretion histories exhibit episodes of significant infall at both early and late times, with the former fostering more intense star formation than the latter. The shorter characteristic consumption timescale of gas accreted in the earlier episode suppresses its enrichment with iron synthesised by Type Ia SNe, resulting in the formation of a high-[α/Fe] sequence. We find that bimodality in [α/Fe] similar to that seen in the Galaxy is rare, appearing in approximately 5 percent of galaxies in our sample. We posit that this is a consequence of an early gas accretion episode requiring the mass accretion history of a galaxy's dark matter halo to exhibit a phase of atypically-rapid growth at early epochs. The scarcity of EAGLE galaxies exhibiting distinct sequences in the [α/Fe]-[Fe/H] plane may therefore indicate that the Milky Way's elemental abundance patterns, and its accretion history, are not representative of the broader population of ˜L⋆ disc galaxies.

  7. Carbon and sulfur distributions and abundances in lunar fines

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Moore, G. W.

    1973-01-01

    Total sulfur abundances have been determined for 20 Apollo 14, 15, and 16 soil samples and one Apollo 14 breccia. Sulfur concentrations range from 474 to 844 microg S/g. Volatilization experiments on selected samples have been carried out using step-wise heating. Sample residues have been analyzed for their total carbon and sulfur abundances to establish the material balance in lunar fines for these two elements. Volatilization experiments have established that between 31 to 54 microg C/g remains in soils which have been heated at 1100 C for 24 hours under vacuum. The residual carbon is believed to be indigenous lunar carbon whereas all forms of carbon lost from samples below 1100 C is extralunar carbon. Total carbon and sulfur abundances taken from the literature have been used to show the depletion of volatile elements with increasing grade for the Apollo 14 breccias.

  8. Implications of Barium Abundances for the Chemical Enrichment of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Duggan, Gina; Kirby, Evan N.

    2018-06-01

    There are many candidate sites of the r-process: core-collapse supernovae (including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies—specifically dwarf galaxies—helps distinguish between these sources based on the continual build-up of r-process elements. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We will present the largest sample of barium abundances (more than 200 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [alpha/Fe] measurements. We have found that a large contribution of barium needs to occur at timescales similar to Type Ia supernovae in order to recreate our observed abundances, namely the flat or slightly rising trend of [Ba/Fe] vs. [Fe/H]. We conclude that neutron star mergers are the main contribution of r-process enrichment in dwarf galaxies.

  9. HOW MANY NUCLEOSYNTHESIS PROCESSES EXIST AT LOW METALLICITY?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hansen, C. J.; Montes, F.; Arcones, A., E-mail: cjhansen@lsw.uni-heidelberg.de, E-mail: cjhansen@dark-cosmology.dk, E-mail: montes@nscl.msu.edu, E-mail: almudena.arcones@physik.tu-darmstadt.de

    Abundances of low-metallicity stars offer a unique opportunity to understand the contribution and conditions of the different processes that synthesize heavy elements. Many old, metal-poor stars show a robust abundance pattern for elements heavier than Ba, and a less robust pattern between Sr and Ag. Here we probe if two nucleosynthesis processes are sufficient to explain the stellar abundances at low metallicity, and we carry out a site independent approach to separate the contribution from these two processes or components to the total observationally derived abundances. Our approach provides a method to determine the contribution of each process to themore » production of elements such as Sr, Zr, Ba, and Eu. We explore the observed star-to-star abundance scatter as a function of metallicity that each process leads to. Moreover, we use the deduced abundance pattern of one of the nucleosynthesis components to constrain the astrophysical conditions of neutrino-driven winds from core-collapse supernovae.« less

  10. Sensitivity of trace element pyritization to pyrite oxidation processes

    NASA Astrophysics Data System (ADS)

    Moreira, Manuel; Díaz, Rut; Mendoza, Ursula; Capilla, Ramses; Böttcher, Michael; Luiza Albuquerque, Ana; Machado, Wilson

    2014-05-01

    Total trace elements concentration variability in marine sediments has been widely used as a proxy for redox conditions and marine paleoprodutivity. However, partial extraction procedures reduce influences of detrital sedimentary fractions, and information on trace element geochemical partitioning can contribute to provide comprehensive evidences on elemental sensitivity to particular processes. The potential effect of sedimentary pyrite re-oxidative cycling on the degree of trace metal pyritization (DTMP) has not been previously evaluated. This study investigates this effect in 4 sediment cores from the continental shelf under the influence of a tropical upwelling system (Cabo Frio, Brazil). The relation of DTMP with stable isotope signals (δ34SCRS) of chromium reducible sulfur, which becomes lighter in response to intense pyrite re-oxidative cycling in the study area, suggests high (As, Cd and Mn), low (Cu and Zn) or negligible (Cr and Ni) re-oxidation influences. The oldest, pyrite-richer sediments provide an apparent threshold for intense pyrite re-oxidation, after which most trace elements (As, Cd, Zn and Mn) presented more accentuated pyritization. A middle shelf core presented negative correlations of reactive (HCl-soluble) Mn, Cu and Ni with pyrite iron, suggesting Mn oxide (and associated metals) depletion in reaction with pyrite. Results provided evidences for coupled influences from both aerobic and anaerobic oxidative processes on trace elements incorporation into pyrite. Pyrite δ34S signatures under the oxic bottom water from the study area were similar to those from euxinic sedimentary environments, suggesting that pyrite re-oxidative cycling can affect trace element susceptibility to be incorporated and preserved into pyrite in a wide range of sedimentary conditions. The evaluation of trace elements sensitivity to these processes can contribute to improve the use of multiple DTMP data (e.g., as paleoredox proxies). Considering that S re

  11. The GAPS programme with HARPS-N at TNG. X. Differential abundances in the XO-2 planet-hosting binary

    NASA Astrophysics Data System (ADS)

    Biazzo, K.; Gratton, R.; Desidera, S.; Lucatello, S.; Sozzetti, A.; Bonomo, A. S.; Damasso, M.; Gandolfi, D.; Affer, L.; Boccato, C.; Borsa, F.; Claudi, R.; Cosentino, R.; Covino, E.; Knapic, C.; Lanza, A. F.; Maldonado, J.; Marzari, F.; Micela, G.; Molaro, P.; Pagano, I.; Pedani, M.; Pillitteri, I.; Piotto, G.; Poretti, E.; Rainer, M.; Santos, N. C.; Scandariato, G.; Zanmar Sanchez, R.

    2015-11-01

    Binary stars hosting exoplanets are a unique laboratory where chemical tagging can be performed to measure the elemental abundances of both stellar components with high accuracy, with the aim to investigate the formation of planets and their subsequent evolution. Here, we present a high-precision differential abundance analysis of the XO-2 wide stellar binary based on high-resolution HARPS-N at TNG spectra. Both components are very similar K-dwarfs and host planets. Since they formed presumably within the same molecular cloud, we expect that they possess the same initial elemental abundances. We investigated whether planets can cause some chemical imprints in the stellar atmospheric abundances. We measure abundances of 25 elements for both stars with a range of condensation temperature TC = 40-1741 K, achieving typical precisions of ~0.07 dex. The northern component shows abundances in all elements higher by +0.067 ± 0.032 dex on average, with a mean difference of +0.078 dex for elements with TC > 800 K. The significance of the XO-2N abundance difference relative to XO-2S is at the 2σ level for almost all elements. We discuss that this result might be interpreted as the signature of the ingestion of material by XO-2N or depletion in XO-2S that is due to locking of heavy elements by the planetary companions. We estimate a mass of several tens of M⊕ in heavy elements. The difference in abundances between XO-2N and XO-2S shows a positive correlation with the condensation temperatures of the elements, with a slope of (4.7 ± 0.9) × 10-5 dex K-1, which could mean that both components have not formed terrestrial planets, but first experienced the accretion of rocky core interior to the subsequent giant planets. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF - Fundación Galileo Galilei at the Roche de los Muchachos Observatory of the Instituto de Astrofísica de Canarias (IAC) in the

  12. Elemental abundance analyses with coadded DAO spectrograms. VI - The mercury-manganese stars Nu Cancri, Iota Coronae Borealis and HR 8349

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.

    1989-01-01

    The elemental abundances of three mercury-manganese stars, Nu Cancri, Iota Coronae Borealis, and HR 8349, were found to be consistent with previous analyses of this series. As Iota CrB is a double-lined spectroscopic binary with a small velocity amplitude for most of its period, its study required determining whether the observed lines were produced in the primary or secondary or both. The derived abundances and effective termperatures were used along with those of mercury-manganese stars previously analyzed in order to extend the study of probable correlations between abundances, with the effective temperature and surface gravity in accordance with radiative diffusion explanations.

  13. Relationships between protein-encoding gene abundance and corresponding process are commonly assumed yet rarely observed

    USGS Publications Warehouse

    Rocca, Jennifer D.; Hall, Edward K.; Lennon, Jay T.; Evans, Sarah E.; Waldrop, Mark P.; Cotner, James B.; Nemergut, Diana R.; Graham, Emily B.; Wallenstein, Matthew D.

    2015-01-01

    For any enzyme-catalyzed reaction to occur, the corresponding protein-encoding genes and transcripts are necessary prerequisites. Thus, a positive relationship between the abundance of gene or transcripts and corresponding process rates is often assumed. To test this assumption, we conducted a meta-analysis of the relationships between gene and/or transcript abundances and corresponding process rates. We identified 415 studies that quantified the abundance of genes or transcripts for enzymes involved in carbon or nitrogen cycling. However, in only 59 of these manuscripts did the authors report both gene or transcript abundance and rates of the appropriate process. We found that within studies there was a significant but weak positive relationship between gene abundance and the corresponding process. Correlations were not strengthened by accounting for habitat type, differences among genes or reaction products versus reactants, suggesting that other ecological and methodological factors may affect the strength of this relationship. Our findings highlight the need for fundamental research on the factors that control transcription, translation and enzyme function in natural systems to better link genomic and transcriptomic data to ecosystem processes.

  14. Fractionation of highly siderophile and chalcogen elements in components of EH3 chondrites

    NASA Astrophysics Data System (ADS)

    Kadlag, Yogita; Becker, Harry

    2015-07-01

    Abundances of highly siderophile elements (HSE: Re, platinum group elements and Au), chalcogens (Te, Se and S), 187Os/188Os and the major and minor elements Mg, Ca, Mn, Fe, Ni and Co were determined in the components of Sahara 97072 (EH3, find) and Kota Kota (EH3, find) in order to understand the element fractionation processes. In a 187Re-187Os isochron diagram, most magnetic components lie close to the 4.56 Ga IIIA iron meteorite isochron, whereas most other components show deviations from the isochron caused by late redistribution of Re, presumably during terrestrial weathering. Metal- and sulfide rich magnetic fractions and metal-sulfide nodules are responsible for the higher 187Os/188Os in bulk rocks of EH chondrites compared to CI chondrites. The HSE and chalcogens are enriched in magnetic fractions relative to slightly magnetic and nonmagnetic fractions and bulk compositions, indicating that Fe-Ni metal is the main host phase of the HSE in enstatite chondrites. HSE abundance patterns indicate mixing of two components, a CI chondrite like end member and an Au-enriched end member. Because of the decoupled variations of Au from those of Pd or the chalcogens, the enrichment of Au in EH metal cannot be due to metal-sulfide-silicate partitioning processes. Metal and sulfide rich nodules may have formed by melting and reaction of pre-existing refractory element rich material with volatile rich gas. A complex condensation and evaporation history is required to account for the depletion of elements having very different volatility than Au in EH chondrites. The depletions of Te relative to HSE, Se and S in bulk EH chondrites are mainly caused by the depletion of Te in metal. S/Se and S/Mn are lower than in CI chondrites in almost all components and predominantly reflect volatility-controlled loss of sulfur. The latter most likely occurred during thermal processing of dust in the solar nebula (e.g., during chondrule formation), followed by the non-systematic loss of S

  15. Abundance of live 244Pu in deep-sea reservoirs on Earth points to rarity of actinide nucleosynthesis

    PubMed Central

    Wallner, A.; Faestermann, T.; Feige, J.; Feldstein, C.; Knie, K.; Korschinek, G.; Kutschera, W.; Ofan, A.; Paul, M.; Quinto, F.; Rugel, G.; Steier, P.

    2015-01-01

    Half of the heavy elements including all actinides are produced in r-process nucleosynthesis, whose sites and history remain a mystery. If continuously produced, the Interstellar Medium is expected to build-up a quasi-steady state of abundances of short-lived nuclides (with half-lives ≤100 My), including actinides produced in r-process nucleosynthesis. Their existence in today’s interstellar medium would serve as a radioactive clock and would establish that their production was recent. In particular 244Pu, a radioactive actinide nuclide (half-life=81 My), can place strong constraints on recent r-process frequency and production yield. Here we report the detection of live interstellar 244Pu, archived in Earth’s deep-sea floor during the last 25 My, at abundances lower than expected from continuous production in the Galaxy by about 2 orders of magnitude. This large discrepancy may signal a rarity of actinide r-process nucleosynthesis sites, compatible with neutron-star mergers or with a small subset of actinide-producing supernovae. PMID:25601158

  16. Production of light elements and 98Tc through the ν-process with the neutrino oscillation in supernova explosion

    NASA Astrophysics Data System (ADS)

    Ko, Heamin; Kusakabe, Motohiko; Cheoun, Myung-Ki; Kwak, Kyujin; Kim, Kyungsik

    2018-04-01

    Stars ending with core collapse supernovae (SNe) emit a tremendous number of neutrinos during their explosions. While these neutrinos pass through each layer of the stars, they react with the nuclides in the progenitor. Although the neutrino cross sections are very small, its huge flux is high enough to react with nuclides to change their abundances. We consider this ν-process, by which abundances of some elements may be explained exclusively by this neutrino process. One of the candidates is 98Tc. In this study, we check the ν-process contributions due to the neutrino reactions. In this calculation we also include the neutrino oscillation effect in the matter with varying density, so called MSW effect, not only for 98Tc production but also 4He and 12C destruction, which occurs at first in the He/C layer in the present model.

  17. Neutron-Capture Elements in Very Metal-Poor Halo Stars

    NASA Astrophysics Data System (ADS)

    French, R. S.; Sneden, C.; Cowan, J. J.; Lawler, J. E.; Primas, F.; Beers, T. C.; Truran, J. W.

    2000-05-01

    Abundances of the most massive stable elements (Os -> Pb or 76 <= Z <= 82) in metal-poor stars can provide crucial information about the so-called ``third neutron-capture peak,'' and are critical to the radioactive-dating technique that uses unstable thorium and uranium as chronometers. As the relevant transitions occur in the UV and are inaccessable to ground-based telescopes, we have obtained high resolution (R ~= 30,000) UV spectra of 10 very metal-poor (--3.0 <= [Fe/H] <= --1.4) halo giants using the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope. Using iterative spectrum synthesis techniques, we derive abundances for some of these heavy elements. We compare our abundances to those predicted for very metal-poor stars based on a scaled solar system rapid-process (production in rapid neutron-capture synthesis events, such as occurs during supernovae explosions). This research is supported by NASA STScI grant GO-08342 and NSF grants AST-9618364 to C.S. and AST-9618332 to J.J.C.

  18. Improved Precision and Accuracy of Quantification of Rare Earth Element Abundances via Medium-Resolution LA-ICP-MS.

    PubMed

    Funderburg, Rebecca; Arevalo, Ricardo; Locmelis, Marek; Adachi, Tomoko

    2017-11-01

    Laser ablation ICP-MS enables streamlined, high-sensitivity measurements of rare earth element (REE) abundances in geological materials. However, many REE isotope mass stations are plagued by isobaric interferences, particularly from diatomic oxides and argides. In this study, we compare REE abundances quantitated from mass spectra collected with low-resolution (m/Δm = 300 at 5% peak height) and medium-resolution (m/Δm = 2500) mass discrimination. A wide array of geological samples was analyzed, including USGS and NIST glasses ranging from mafic to felsic in composition, with NIST 610 employed as the bracketing calibrating reference material. The medium-resolution REE analyses are shown to be significantly more accurate and precise (at the 95% confidence level) than low-resolution analyses, particularly in samples characterized by low (<μg/g levels) REE abundances. A list of preferred mass stations that are least susceptible to isobaric interferences is reported. These findings impact the reliability of REE abundances derived from LA-ICP-MS methods, particularly those relying on mass analyzers that do not offer tuneable mass-resolution and/or collision cell technologies that can reduce oxide and/or argide formation. Graphical Abstract ᅟ.

  19. Improved Precision and Accuracy of Quantification of Rare Earth Element Abundances via Medium-Resolution LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Funderburg, Rebecca; Arevalo, Ricardo; Locmelis, Marek; Adachi, Tomoko

    2017-07-01

    Laser ablation ICP-MS enables streamlined, high-sensitivity measurements of rare earth element (REE) abundances in geological materials. However, many REE isotope mass stations are plagued by isobaric interferences, particularly from diatomic oxides and argides. In this study, we compare REE abundances quantitated from mass spectra collected with low-resolution (m/Δm = 300 at 5% peak height) and medium-resolution (m/Δm = 2500) mass discrimination. A wide array of geological samples was analyzed, including USGS and NIST glasses ranging from mafic to felsic in composition, with NIST 610 employed as the bracketing calibrating reference material. The medium-resolution REE analyses are shown to be significantly more accurate and precise (at the 95% confidence level) than low-resolution analyses, particularly in samples characterized by low (<μg/g levels) REE abundances. A list of preferred mass stations that are least susceptible to isobaric interferences is reported. These findings impact the reliability of REE abundances derived from LA-ICP-MS methods, particularly those relying on mass analyzers that do not offer tuneable mass-resolution and/or collision cell technologies that can reduce oxide and/or argide formation.

  20. Modeling unobserved sources of heterogeneity in animal abundance using a Dirichlet process prior

    USGS Publications Warehouse

    Dorazio, R.M.; Mukherjee, B.; Zhang, L.; Ghosh, M.; Jelks, H.L.; Jordan, F.

    2008-01-01

    In surveys of natural populations of animals, a sampling protocol is often spatially replicated to collect a representative sample of the population. In these surveys, differences in abundance of animals among sample locations may induce spatial heterogeneity in the counts associated with a particular sampling protocol. For some species, the sources of heterogeneity in abundance may be unknown or unmeasurable, leading one to specify the variation in abundance among sample locations stochastically. However, choosing a parametric model for the distribution of unmeasured heterogeneity is potentially subject to error and can have profound effects on predictions of abundance at unsampled locations. In this article, we develop an alternative approach wherein a Dirichlet process prior is assumed for the distribution of latent abundances. This approach allows for uncertainty in model specification and for natural clustering in the distribution of abundances in a data-adaptive way. We apply this approach in an analysis of counts based on removal samples of an endangered fish species, the Okaloosa darter. Results of our data analysis and simulation studies suggest that our implementation of the Dirichlet process prior has several attractive features not shared by conventional, fully parametric alternatives. ?? 2008, The International Biometric Society.

  1. Uncertainties in s-process nucleosynthesis in massive stars determined by Monte Carlo variations

    NASA Astrophysics Data System (ADS)

    Nishimura, N.; Hirschi, R.; Rauscher, T.; St. J. Murphy, A.; Cescutti, G.

    2017-08-01

    The s-process in massive stars produces the weak component of the s-process (nuclei up to A ˜ 90), in amounts that match solar abundances. For heavier isotopes, such as barium, production through neutron capture is significantly enhanced in very metal-poor stars with fast rotation. However, detailed theoretical predictions for the resulting final s-process abundances have important uncertainties caused both by the underlying uncertainties in the nuclear physics (principally neutron-capture reaction and β-decay rates) as well as by the stellar evolution modelling. In this work, we investigated the impact of nuclear-physics uncertainties relevant to the s-process in massive stars. Using a Monte Carlo based approach, we performed extensive nuclear reaction network calculations that include newly evaluated upper and lower limits for the individual temperature-dependent reaction rates. We found that most of the uncertainty in the final abundances is caused by uncertainties in the neutron-capture rates, while β-decay rate uncertainties affect only a few nuclei near s-process branchings. The s-process in rotating metal-poor stars shows quantitatively different uncertainties and key reactions, although the qualitative characteristics are similar. We confirmed that our results do not significantly change at different metallicities for fast rotating massive stars in the very low metallicity regime. We highlight which of the identified key reactions are realistic candidates for improved measurement by future experiments.

  2. CubeX: The CubeSAT X-ray Telescope for Elemental Abundance Mapping of Airless Bodies and X-ray Pulsar Navigation

    NASA Astrophysics Data System (ADS)

    Nittler, L. R.; Hong, J.; Kenter, A.; Romaine, S.; Allen, B.; Kraft, R.; Masterson, R.; Elvis, M.; Gendreau, K.; Crawford, I.; Binzel, R.; Boynton, W. V.; Grindlay, J.; Ramsey, B.

    2017-12-01

    The surface elemental composition of a planetary body provides crucial information about its origin, geological evolution, and surface processing, all of which can in turn provide information about solar system evolution as a whole. Remote sensing X-ray fluorescence (XRF) spectroscopy has been used successfully to probe the major-element compositions of airless bodies in the inner solar system, including the Moon, near-Earth asteroids, and Mercury. The CubeSAT X-ray Telescope (CubeX) is a concept for a 6U planetary X-ray telescope (36U with S/C), which utilizes Miniature Wolter-I X-ray optics (MiXO), monolithic CMOS and SDD X-ray sensors for the focal plane, and a Solar X-ray Monitor (heritage from the REXIS XRF instrument on NASA's OSIRIS-REx mission). CubeX will map the surface elemental composition of diverse airless bodies by spectral measurement of XRF excited by solar X-rays. The lightweight ( 1 kg) MiXO optics provide sub-arcminute resolution with low background, while the inherently rad-hard CMOS detectors provide improved spectral resolution ( 150 eV) at 0 °C. CubeX will also demonstrate X-ray pulsar timing based deep space navigation (XNAV). Successful XNAV will enable autonomous deep navigation with little to no support from the Deep Space Network, hence lowering the operation cost for many more planetary missions. Recently selected by NASA Planetary Science Deep Space SmallSat Studies, the first CubeX concept, designed to rideshare to the Moon as a secondary spacecraft on a primary mission, is under study in collaboration with the Mission Design Center at NASA Ames Research Center. From high altitude ( 6,000 km) frozen polar circular orbits, CubeX will study > 8 regions ( 110 km) of geological interest on the Moon over one year to produce a high resolution ( 2-3 km) elemental abundance map of each region. The novel focal plane design of CubeX also allows us to evaluate the performance of absolute navigation by sequential observations of several

  3. Carbon and nitrogen biogeochemistry in the ocean: A study using stable isotope natural abundance

    NASA Technical Reports Server (NTRS)

    Rau, G. H.; Desmarais, David J.

    1985-01-01

    Determining the biogeochemical pathways traveled by carbon and nitrogen in the ocean is fundamental to the understanding of how the ocean participates in the cycling of these elements within the biosphere. Because biological production, metabolism, and respiration can significantly alter the natural abundance of C-13 and N-15, these abundances can provide important information about the nature of these biological processes and their variability in the marine environment. The research initially seeks to characterize the spatial and temporal patterns of stable isotope abundances in organic matter, and to relate these abundances to C and N biogeochemical processes within selected areas of the northeastern Pacific Ocean.

  4. The origin of diverse α-element abundances in galaxy discs

    NASA Astrophysics Data System (ADS)

    Mackereth, J. Ted; Crain, Robert A.; Schiavon, Ricardo P.; Schaye, Joop; Theuns, Tom; Schaller, Matthieu

    2018-07-01

    Spectroscopic surveys of the Galaxy reveal that its disc stars exhibit a spread in [α/Fe] at fixed [Fe/H], manifest at some locations as a bimodality. The origin of these diverse, and possibly distinct, stellar populations in the Galactic disc is not well understood. We examine the Fe and α-element evolution of 133 Milky Way-like galaxies from the EAGLE simulation, to investigate the origin and diversity of their [α/Fe]-[Fe/H] distributions. We find that bimodal [α/Fe] distributions arise in galaxies whose gas accretion histories exhibit episodes of significant infall at both early and late times, with the former fostering more intense star formation than the latter. The shorter characteristic consumption time-scale of gas accreted in the earlier episode suppresses its enrichment with iron synthesized by Type Ia SNe, resulting in the formation of a high-[α/Fe] sequence. We find that bimodality in [α/Fe] similar to that seen in the Galaxy is rare, appearing in approximately 5 per cent of galaxies in our sample. We posit that this is a consequence of an early gas accretion episode requiring the mass accretion history of a galaxy's dark matter halo to exhibit a phase of atypically rapid growth at early epochs. The scarcity of EAGLE galaxies exhibiting distinct sequences in the [α/Fe]-[Fe/H] plane may therefore indicate that the Milky Way's elemental abundance patterns, and its accretion history, are not representative of the broader population of ˜L⋆ disc galaxies.

  5. Germanium, Arsenic, and Selenium Abundances in Metal-poor Stars

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.

    2012-09-01

    The elements germanium (Ge, Z = 32), arsenic (As, Z = 33), and selenium (Se, Z = 34) span the transition from charged-particle or explosive synthesis of the iron-group elements to neutron-capture synthesis of heavier elements. Among these three elements, only the chemical evolution of germanium has been studied previously. Here we use archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and observations from several ground-based facilities to study the chemical enrichment histories of seven stars with metallicities -2.6 <= [Fe/H] <= -0.4. We perform a standard abundance analysis of germanium, arsenic, selenium, and several other elements produced by neutron-capture reactions. When combined with previous derivations of germanium abundances in metal-poor stars, our sample reveals an increase in the [Ge/Fe] ratios at higher metallicities. This could mark the onset of the weak s-process contribution to germanium. In contrast, the [As/Fe] and [Se/Fe] ratios remain roughly constant. These data do not directly indicate the origin of germanium, arsenic, and selenium at low metallicity, but they suggest that the weak and main components of the s-process are not likely sources. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research made use of StarCAT, hosted by the Mikulski Archive at the Space Telescope Science Institute (MAST). These data are associated with Programs GO-7348, GO-7433, GO-8197, GO-9048, GO-9455, and GO-9804.Based on data obtained from the European Southern Observatory (ESO) Science Archive Facility. These data are associated with Programs 67.D-0439(A), 074.C-0364(A), 076.B-0055(A), and 080.D-0347(A).This research has made use of the Keck Observatory Archive (KOA), which is operated by

  6. The predominantly selfing plant Arabidopsis thaliana experienced a recent reduction in transposable element abundance compared to its outcrossing relative Arabidopsis lyrata

    PubMed Central

    2012-01-01

    Background Transposable elements (TEs) are major contributors to genome evolution. One factor that influences their evolutionary dynamics is whether their host reproduces through selfing or through outcrossing. According to the recombinational spreading hypothesis, for instance, TEs can spread more easily in outcrossing species through recombination, and should thus be less abundant in selfing species. We here studied the distribution and evolutionary dynamics of TE families in the predominantly selfing plant Arabidopsis thaliana and its close outcrossing relative Arabidopsis lyrata on a genome-wide scale. We characterized differences in TE abundance between them and asked which, if any, existing hypotheses about TE abundances may explain these differences. Results We identified 1,819 TE families representing all known classes of TEs in both species, and found three times more copies in the outcrossing A. lyrata than in the predominantly selfing A. thaliana, as well as ten times more TE families unique to A. lyrata. On average, elements in A. lyrata are younger than elements in A. thaliana. In particular, A. thaliana shows a marked decrease in element number that occurred during the most recent 10% of the time interval since A. thaliana split from A. lyrata. This most recent period in the evolution of A. thaliana started approximately 500,000 years ago, assuming a splitting time of 5 million years ago, and coincides with the time at which predominant selfing originated. Conclusions Our results indicate that the mating system may be important for determining TE copy number, and that selfing species are likely to have fewer TEs. PMID:22313744

  7. Relative elemental abundance and heating constraints determined for the solar corona from SERTS measurements

    NASA Technical Reports Server (NTRS)

    Falconer, David A.

    1994-01-01

    Intensities of EUV spectral lines were measured as a function of radius off the solar limb by two flights of Goddard's Solar EUV Rocket Telescope and Spectrograph (SERTS) for three quiet sun regions. The density scale height, line-ratio densities, line-ratio temperatures, and emission measures were determined. The line-ratio temperature determined from the ionization balances of Arnaud and Rothenflug (1985) were more self-consistent than the line-ratio temperatures obtained from the values of Arnaud and Raymond (1992). Limits on the filling factor were determined from the emission measure and the line-ratio densities for all three regions. The relative abundances of silicon, aluminum, and chromium to iron were determined. Results did agree with standard coronal relative elemental abundances for one observation, but did not agree for another. Aluminum was overabundant while silicon was underabundant. Heating was required above 1.15 solar radii for all three regions studied. For two regions, local nonconductive heating is needed for any filling factor, and in all three regions for filling factor of 0.1.

  8. Detailed chemical abundance analysis of the thick disk star cluster Gaia 1

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; Hansen, Terese T.; Kunder, Andrea

    2018-01-01

    Star clusters, particularly those objects in the disk-bulge-halo interface are as yet poorly charted, despite the fact that they carry important information about the formation and the structure of the Milky Way. Here, we present a detailed chemical abundance study of the recently discovered object Gaia 1. Photometry has previously suggested it as an intermediate-age, moderately metal-rich system, although the exact values for its age and metallicity remained ambiguous in the literature. We measured detailed chemical abundances of 14 elements in four red giant members, from high-resolution (R = 25 000) spectra that firmly establish Gaia 1 as an object associated with the thick disk. The resulting mean Fe abundance is -0.62 ± 0.03(stat.)± 0.10(sys.) dex, which is more metal-poor than indicated by previous spectroscopy from the literature, but it is fully in line with values from isochrone fitting. We find that Gaia 1 is moderately enhanced in the α-elements, which allowed us to consolidate its membership with the thick disk via chemical tagging. The cluster's Fe-peak and neutron-capture elements are similar to those found across the metal-rich disks, where the latter indicate some level of s-process activity. No significant spread in iron nor in other heavy elements was detected, whereas we find evidence of light-element variations in Na, Mg, and Al. Nonetheless, the traditional Na-O and Mg-Al (anti-)correlations, typically seen in old globular clusters, are not seen in our data. This confirms that Gaia 1 is rather a massive and luminous open cluster than a low-mass globular cluster. Finally, orbital computations of the target stars bolster our chemical findings of Gaia 1's present-day membership with the thick disk, even though it remains unclear which mechanisms put it in that place. This paper includes data gathered with the 2.5 meter du Pont Telescope located at Las Campanas Observatory, Chile.Full Table 2 is available at the CDS via anonymous ftp to http

  9. Recent approaches for the direct use of elemental sulfur in the synthesis and processing of advanced materials.

    PubMed

    Lim, Jeewoo; Pyun, Jeffrey; Char, Kookheon

    2015-03-09

    Elemental sulfur is an abundant and inexpensive material obtained as a by-product of natural-gas and petroleum refining operations. Recently, the need for the development of new energy-storage systems brought into light the potential of sulfur as a high-capacity cathode material in secondary batteries. Sulfur-containing materials were also shown to have useful IR optical properties. These developments coupled with growing environmental concerns related to the global production of excess elemental sulfur have led to a keen interest in its utilization as a feedstock in materials applications. This Minireview focuses on the recent developments on physical and chemical methods for directly processing elemental sulfur to produce functional composites and polymers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Chempy: A flexible chemical evolution model for abundance fitting. Do the Sun's abundances alone constrain chemical evolution models?

    NASA Astrophysics Data System (ADS)

    Rybizki, Jan; Just, Andreas; Rix, Hans-Walter

    2017-09-01

    Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of five to ten parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: for example, the star-formation history (SFH), the feedback efficiency, the stellar initial mass function (IMF), and the incidence of supernova of type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. It is essentially a chemical evolution fitting tool. We straightforwardly extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of the Sun, Arcturus, and the present-day interstellar medium (ISM). For the first time, we use such information to infer the IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that 11.6+ 2.1-1.6% of the IMF explodes as core-collapse supernova (CC-SN), compatible with Salpeter (1955, ApJ, 121, 161). We also constrain the incidence of SN Ia per 103M⊙ to 0.5-1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication of missing nucleosynthetic channels. Chempy could be a powerful tool to confront predictions from stellar

  11. Coronal Abundances and Their Variation

    NASA Technical Reports Server (NTRS)

    Saba, Julia L. R.

    1996-01-01

    This contract supported the investigation of elemental abundances in the solar corona, principally through analysis of high-resolution soft X-ray spectra from the Flat Crystal Spectrometer on NASA's Solar Maximum Mission. The goals of the study were a characterization of the mean values of relative abundances of elements accessible in the FCS data, and information on the extent and circumstances of their variability. This is the Final Report, summarizing the data analysis and reporting activities which occurred during the period of performance, June 1993 - December 1996.

  12. Central Elemental Abundance Ratios In the Perseus Cluster: Resonant Scattering or SN Ia Enrichment?

    NASA Technical Reports Server (NTRS)

    Dupke, Renato A.; Arnaud, Keith; White, Nicholas E. (Technical Monitor)

    2001-01-01

    We have determined abundance ratios in the core of the Perseus Cluster for several elements. These ratios indicate a central dominance of Type 1a supernova (SN Ia) ejects similar to that found for A496, A2199 and A3571. Simultaneous analysis of ASCA spectra from SIS1, GIS2, and GIS3 shows that the ratio of Ni to Fe abundances is approx. 3.4 +/- 1.1 times solar within the central 4'. This ratio is consistent with (and more precise than) that observed in other clusters whose central regions are dominated by SN Ia ejecta. Such a large Ni overabundance is predicted by "convective deflagration" explosion models for SNe Ia such as W7 but is inconsistent with delayed detonation models. We note that with current instrumentation the Ni K(alpha) line is confused with Fe K(beta) and that the Ni overabundance we observe has been interpreted by others as an anomalously large ratio of Fe K(beta) to Fe K(alpha) caused by resonant scattering in the Fe K(alpha) line. We argue that a central enhancement of SN Ia ejecta and hence a high ratio of Ni to Fe abundances are naturally explained by scenarios that include the generation of chemical gradients by suppressed SN Ia winds or ram pressure stripping of cluster galaxies. It is not necessary to suppose that the intracluster gas is optically thick to resonant scattering of the Fe K(alpha) line.

  13. Metal-silicate partitioning and the light element in the core (Invited)

    NASA Astrophysics Data System (ADS)

    Wood, B. J.; Wade, J.; Tuff, J.

    2009-12-01

    Most attempts to constrain the concentrations of “light” elements in the Earth’s core rely either on cosmochemical arguments or on arguments based on the densities and equations of state of Fe-alloys containing the element of concern. Despite its utility, the latter approach yields a wide range of permissible compositions and hence weak constraints. The major problem with the cosmochemical approach is that the abundances in the bulk Earth of all the candidate “light” elements- H, C, O, Si and S are highly uncertain because of their volatile behavior during planetary accretion. In contrast, refractory elements appear to be in approximately CI chondritic relative abundances in the Earth. This leads to the potential for using the partitioning of refractory siderophile elements between the mantle and core to constrain the concentrations of light elements in the core. Recent experimental metal-silicate partitioning data, coupled with mantle abundances of refractory siderophile elements (e.g. Wade and Wood, EPSL v.236, 78—95,2005; Kegler et. al. EPSL v.268, 28-40,2008) have shown that the core segregated from the mantle under high pressure conditions (~40 GPa). If a wide range of elements, from very siderophile, (e.g. Mo) through moderately (Ni, Co, W) to weakly siderophile (V, Cr, Nb, Si) are considered, the Earth also appears to have become more oxidized during accretion. Metal-silicate partitioning of some elements is also sensitive to the light element content of the metal. For example, Nb and W partitioning depend strongly on carbon, Mo on silicon and Cr on sulfur. Given the measured mantle abundances of the refractory elements, these observations enable the Si and C contents of the core to be constrained at ~5% and <2% respectively while partitioning is consistent with a cosmochemically-estimated S content of ~2%.

  14. Linking Soil Moisture Variation and Abundance of Plants to Geomorphic Processes: A Generalized Model for Erosion-Uplifting Landscapes

    NASA Astrophysics Data System (ADS)

    Ding, Junyan; Johnson, Edward A.; Martin, Yvonne E.

    2018-03-01

    The diffusive and advective erosion-created landscapes have similar structure (hillslopes and channels) across different scales regardless of variations in drivers and controls. The relative magnitude of diffusive erosion to advective erosion (D/K ratio) in a landscape development model controls hillslope length, shape, and drainage density, which regulate soil moisture variation, one of the critical resources of plants, through the contributing area (A) and local slope (S) represented by a topographic index (TI). Here we explore the theoretical relation between geomorphic processes, TI, and the abundance and distribution of plants. We derived an analytical model that expresses the TI with D, K, and A. This gives us the relation between soil moisture variation and geomorphic processes. Plant tolerance curves are used to link plant performance to soil moisture. Using the hypothetical tolerance curves of three plants, we show that the abundance and distribution of xeric, mesic, and hydric plants on the landscape are regulated by the D/K ratio. Where diffusive erosion is the major erosion process (large D/K ratio), mesic plants have higher abundance relative to xeric and hydric plants and the landscape has longer and convex-upward hillslope and low channel density. Increasing the dominance of advective erosion increases relative abundance of xeric and hydric plants dominance, and the landscape has short and concave hillslope and high channel density.

  15. Understanding r-process nucleosynthesis with dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Ji, Alexander P.

    2018-06-01

    The Milky Way's faintest dwarf galaxy satellites each sample short, independent bursts of star formation from the first 1-2 Gyr of the universe. Their simple formation history makes them ideal systems to understand how rare events like neutron star mergers contribute to early enrichment of r-process elements. I will focus on the ultra-faint galaxy Reticulum II, which experienced a single prolific r-process event that left ~80% of its stars extremely enriched in r-process elements. I will present abundances of ~40 elements derived from the highest signal-to-noise high-resolution spectrum ever taken for an ultra-faint dwarf galaxy star. Precise measurements of elements from all three r-process peaks reaffirm the universal nature of the r-process abundance pattern from Ba to Ir. The first r-process peak is significantly lower than solar but matches other r-process enhanced stars. This constrains the neutron-richness of r-process ejecta in neutron star mergers. The radioactive element thorium is detected with a somewhat low abundance. Naive application of currently predicted initial production ratios could imply an age >20 Gyr, but more likely indicates that the initial production ratios require revision. The abundance of lighter elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. These elements may eventually provide a way to test for other hypothesized r-process sites, but only after a more detailed understanding of the chemical evolution in this galaxy. Reticulum II provides a clean view of early r-process enrichment that can be used to understand the increasing number of r-process measurements in other dwarf galaxies.

  16. A Simplified Finite Element Simulation for Straightening Process of Thin-Walled Tube

    NASA Astrophysics Data System (ADS)

    Zhang, Ziqian; Yang, Huilin

    2017-12-01

    The finite element simulation is an effective way for the study of thin-walled tube in the two cross rolls straightening process. To determine the accurate radius of curvature of the roll profile more efficiently, a simplified finite element model based on the technical parameters of an actual two cross roll straightening machine, was developed to simulate the complex straightening process. Then a dynamic simulation was carried out using ANSYS LS-DYNA program. The result implied that the simplified finite element model was reasonable for simulate the two cross rolls straightening process, and can be obtained the radius of curvature of the roll profile with the tube’s straightness 2 mm/m.

  17. Elemental, isotopic and molecular abundances in comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1986-01-01

    The chemical composition of comet nuclei and the factors affecting it are discussed, summarizing the results of recent theoretical, experimental, and observational investigations. Consideration is given to the evidence supporting the view that the nucleus is radially differentiation (except for a thin outer layer), surface differentiation by heat processing and outgassing, and mantle buildup on an undifferentiated core. The nature of the refractory and volatile components is examined, and the elemental and isotopic compositions are given in tables and characterized. The uncertain (except for H2O) molecular composition of the volatile fraction is considered, and it is suggested that some oxides or aldehydes (such as CO, CO2, and H2CO), but no large amounts of fully hydrogenated compounds (such as CH4 and NH3) are included.

  18. Elemental abundance analyses with Complejo Astronomico EL Leoncito REOSC echelle spectrograms. III. HR 4487, 14 Hydrae, and 3 Centauri A

    NASA Astrophysics Data System (ADS)

    Pintado, O. I.; Adelman, S. J.; Gulliver, A. F.

    1998-05-01

    Using CASLEO echelle spectrograms, elemental abundances are derived for the sharp-lined non-magnetic CP stars HR 4487, 14 Hya, and 3 Cen A. The first two stars are members of the Mercury-Manganese subgroup and have abundances which are similar to other such peculiar stars. The third is a hotter related star. The detection of Mn II lines in its spectrum adds to this relationship. Table 3 is avaible electronically vit the CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html.

  19. Behavior of Abundances in Chemically Peculiar Dwarf and Subgiant A-Type Stars: HD 23193 and HD 170920

    NASA Astrophysics Data System (ADS)

    Kılıçoğlu, Tolgahan; Çalışkan, Şeyma; Ünal, Kübraözge

    2018-01-01

    To understand the origin of the abundance peculiarities of non-magnetic A-type stars, we present the first detailed chemical abundance analysis of a metallic line star HD 23193 (A2m) and an A-type subgiant HD 170920 (A5), which could have been a HgMn star on the main sequence. Our analysis is based on medium (R ∼ 14,000) and high (R ∼ 40,000) resolution spectroscopic data of the stars. The abundances of 18 elements are derived: C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, and Ba. The masses of HD 23193 and HD 170920 are estimated from evolutionary tracks as 2.3 ± 0.1 M ⊙ and 2.9 ± 0.1 M ⊙. The ages are found to be 635 ± 33 Myr for HD 23193 and 480 ± 50 Myr for HD 170920 using isochrones. The abundance pattern of HD 23193 shows deviations from solar values in the iron-peak elements and indicates remarkable overabundances of Sr (1.16), Y (1.03), and Ba (1.24) with respect to the solar abundances. We compare the derived abundances of this moderately rotating (v\\sin i =37.5 km s‑1) Am star to the theoretical chemical evolution models including rotational mixing. The theoretically predicted abundances resemble our derived abundance pattern, except for a few elements (Si and Cr). For HD 170920, we find nearly solar abundances, except for C (‑0.43), S (0.16), Ti (0.15), Ni (0.16), Zn (0.41), Y (0.57), and Ba (0.97). Its low rotational velocity (v\\sin i=14.5 km s‑1), reduced carbon abundance, and enhanced heavy element abundances suggest that the star is most likely an evolved HgMn star. Based on observations made at the TÜBITAK National Observatory (Program ID 14BRTT150–671), and the Ankara University Observatory, Turkey.

  20. Deep Optical Spectroscopy of Planetary Nebulae: The Search for Neutron-Capture Elements

    NASA Astrophysics Data System (ADS)

    Sterling, Nicholas C.; Garofali, K.; Dinerstein, H. L.; Hwang, S.; Redfield, S.

    2013-01-01

    We present deep, high-resolution (R=36,700) optical spectra of five planetary nebulae (PNe), taken with the 2D-coude echelle spectrograph on the 2.7-m Harlan J. Smith Telescope at McDonald Observatory. These observations are part of a larger optical survey of PNe, designed to unambiguously detect emission lines from neutron(n)-capture elements (atomic number Z>30). The abundances of these elements are of particular interest in PNe, since they can be produced by slow n-capture nucleosynthesis (the ``s-process'') during the asymptotic giant branch (AGB) stage of evolution of PN progenitor stars. The first large-scale investigation of n-capture element abundances in PNe (Sterling & Dinerstein 2008, ApJS, 174, 157) surveyed [Kr III] and [Se IV] transitions in the K band spectra of more than 80 PNe. However, the abundances derived from these data relied on ionization corrections that were often large and uncertain due to the detection of only one ion per element. Transitions of other Se and Kr ions, as well as many other trans-iron species, reside at optical wavelengths. High-resolution spectra are essential to unequivocally identify these lines and resolve potential blends with other species. The spectra we present are rich in emission features, with between 125 and 600 distinct lines detected in each PN. Emission from at least one Kr ion is detected in all five objects, and two (Hb 12 and J 900) exhibit emission from multiple Kr ions. We detected multiple Xe ions in J 900, as well as Se, Br, and Rb lines. Hb 12 also exhibits Xe emission, and the first detection of [Se II] in a PN to our knowledge. The spectra display a wealth of other emission lines, including permitted features of second-row elements and forbidden transitions of several iron-peak elements (e.g., Cr, Mn, Fe, Co, Ni, and Cu). Our survey makes it possible to derive more accurate Se and Kr abundances in PNe, and reveals the enrichment of other trans-iron elements. This enables more accurate s-process

  1. Neutron Capture Rates and the r-Process Abundance Pattern in Shocked Neutrino-Driven Winds

    NASA Astrophysics Data System (ADS)

    Barringer, Daniel; Surman, Rebecca

    2009-10-01

    The r-process is an important process in nucleosynthesis in which nuclei will undergo rapid neutron captures. Models of the r-process require nuclear data such as neutron capture rates for thousands of individual nuclei, many of which lie far from stability. Among the potential sites for the r-process, and the one that we investigate, is the shocked neutrino-driven wind in core-collapse supernovae. Here we examine the importance of the neutron capture rates of specific, individual nuclei in the second r-process abundance peak occurring at A ˜ 130 for a range of parameterized neutrino-driven wind trajectories. Of specific interest are the nuclei whose capture rates affect the abundances of nuclei outside of the A ˜ 130 peak. We found that increasing the neutron capture rate for a number of nuclei including ^135In, ^132Sn, ^133Sb, ^137Sb, and ^136Te can produce changes in the resulting abundance pattern of up to 13%.

  2. The impact of the Tekay chromoviral elements on genome organisation and evolution of Anemone s.l. (Ranunculaceae).

    PubMed

    Mlinarec, J; Franjević, D; Harapin, J; Besendorfer, V

    2016-03-01

    We studied the highly abundant chromoviral Tekay clade in species from three sister genera - Anemone, Pulsatilla and Hepatica (Ranunculaceae). With this clade, we performed a concomitant survey of its phylogenetic diversity, chromosomal organisation and transcriptional activity in Anemone s.l. in order to investigate dynamics of the Tekay elements at a finer scale than previously achieved in this or any other flowering clade. The phylogenetic tree built from Tekay sequences conformed to expected evolutionary relationships of the species; exceptions being A. nemorosa and A. sylvestris, which appeared more closely related that expected, and we invoke hybridisation events to explain the observed topology. The separation of elements into six clusters could be explained by episodic bursts of activity since divergence from a common ancestor at different points in their respective evolutionary histories. In Anemone s.l. the Tekay elements do not have a preferential position on chromosomes, i.e. they can have a: (i) centromeric/pericentromeric position; (ii) interstitial position in DAPI-positive AT-rich heterochromatic regions; can be (iii) dispersed throughout chromosomes; or even (iv) be absent from large heterochromatic blocks. Widespread transcriptional activity of the Tekay elements in Anemone s.l. taxa indicate that some copies of Tekay elements could still be active in this plant group, contributing to genome evolution and speciation within Anemone s.l. Identification of Tekay elements in Anemone s.l. provides valuable information for understanding how different localisation patterns might help to facilitate plant genome organisation in a structural and functional manner. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

  3. Origin of central abundances in the hot intra-cluster medium. I. Individual and average abundance ratios from XMM-Newton EPIC

    NASA Astrophysics Data System (ADS)

    Mernier, F.; de Plaa, J.; Pinto, C.; Kaastra, J. S.; Kosec, P.; Zhang, Y.-Y.; Mao, J.; Werner, N.

    2016-08-01

    The hot intra-cluster medium (ICM) is rich in metals, which are synthesised by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ~ 2-3). In this study, we use the EPIC and RGS instruments on board XMM-Newton to measure the abundances of nine elements (O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (~20-40%) over the sample, within 0.2r500 and especially 0.05r500. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are uniform over the considered temperature range (~0.6-8 keV) and with a limited scatter. In addition to an unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe which we firmly detected (>4σ with MOS and pn independently). We find that Cr/Fe, Mn/Fe, and Ni/Fe differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (~4.5 Ms) of our dataset, no line emission feature is seen around ~3.5 keV.

  4. Platinum Group Element (PGE) Abundances in Lava Flows Generated by the Hawaiian Plume: Insights into Plume Evolution

    NASA Astrophysics Data System (ADS)

    Shafer, J. T.; Neal, C. R.

    2003-12-01

    Picritic and high-MgO (7.7-24 wt.%) basalt samples from Detroit (/sim81-76 Ma) and Koko (/sim48 Ma) Seamounts along the ESC have been analyzed for PGEs (Ru, Rh, Pd, Ir, and Pt) allowing an examination of how the PGEs in lavas from the Hawaiian plume have changed over time. Major and trace element (including the PGEs) concentrations were quantified by ICP methods at the University of Notre Dame. See Ely et al. (1999, Chem. Geol. 157:219) for the PGE analytical method. Bennett et al. (2000) analyzed Hawaiian picrites and found PGE abundances slightly greater than average MORB and comparable to the low-PGE basaltic komatiites. These authors modeled the PGE abundances of these picrites by using variable amounts of residual sulfide during melting, such that Koolau (low PGE contents) formed from a relatively sulfide-rich source and Loihi (high PGEs) from a sulfide-poor source. Our PGE data from Detroit Seamount show slightly higher PGE abundances than Loihi and Kilauea, suggesting these picrites formed from a source lacking residual sulfide. These results suggest that, if the model of Bennett et al. (2000) is correct, the dilution of plume lava with MORB source, as hypothesized on the basis of depleted isotope ratios and lower trace element abundances than modern Hawaii (Keller et al., 2000, Nature 405:603; Kinman & Neal, 2002, Eos 83:F1282; Regelous et al., 2003, JPet 44:113), was not the controlling factor in PGE abundances. However, since MORB PGE concentrations are not substantially different than low-PGE Hawaiian picrites, incorporation of MORB material within the Hawaiian plume at Detroit Seamount would not have drastically reduced the PGE abundances. Koko Seamount has relatively high PGE concentrations (/sim3-12 times greater than those from Detroit lavas). This may be the result of a lack of residual sulfide facilitated by higher degrees of partial melting. Although our initial data are consistent with variable degrees of partial melting and/or source

  5. Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229

    NASA Astrophysics Data System (ADS)

    Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael; Walker, Matthew G.

    2017-10-01

    NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectroscopic data on this cluster, we present a detailed chemical composition analysis of 11 red giant branch members based on high resolution (R ≈ 38,000), high S/N (>100) spectra obtained with the MMT-Hectochelle instrument. We find the cluster to have a mean heliocentric radial velocity of -{138.1}-1.0+1.0 {km} {{{s}}}-1, a small dispersion of {3.8}-0.7+1.0 {km} {{{s}}}-1, and a relatively low {(M/{L}{{V}})}⊙ ={0.82}-0.28+0.49. The cluster is moderately metal-poor with < [{Fe}/{{H}}]> =-1.13 dex and a modest dispersion of 0.06 dex. However, 18% (2/11) of the stars in our sample have strongly enhanced [La, Nd/Fe] ratios that are correlated with a small (˜0.05 dex) increase in [Fe/H]. NGC 6229 shares several chemical signatures with M75, NGC 1851, and the intermediate metallicity populations of ω Cen, which lead us to conclude that NGC 6229 is a lower mass iron-complex cluster. The light elements exhibit the classical (anti-)correlations that extend up to Si, but the cluster possesses a large gap in the O-Na plane that separates first and second generation stars. NGC 6229 also has unusually low [Na, Al/Fe] abundances that are consistent with an accretion origin. A comparison with M54 and other Sagittarius clusters suggests that NGC 6229 could also be the remnant core of a former dwarf spheroidal galaxy.

  6. Renal cell carcinoma containing abundant non-calcified fat.

    PubMed

    Wasser, Elliot J; Shyn, Paul B; Riveros-Angel, Marcela; Sadow, Cheryl A; Steele, Graeme S; Silverman, Stuart G

    2013-06-01

    Renal masses found to contain macroscopic fatty elements on CT or MRI imaging can generally be classified as benign angiomyolipomas. Rarely, renal cell carcinomas may also contain evidence of macroscopic fat. When true adipocytic elements are present, this is generally due to a process of osseous metaplasia in which both fat cells and calcification are co-localized within the mass. We present a patient with a large papillary renal cell carcinoma containing abundant fat with sparse, punctate calcification remote from the fatty elements on imaging. This report highlights the need for radiologists to maintain caution when diagnosing renal angiomyolipomas on the basis of macroscopic fat and reviews the current literature on fat-containing renal masses.

  7. Higher Signal-to-Noise Measurements of Alpha-element Abundances in the M31 System

    NASA Astrophysics Data System (ADS)

    Escala, Ivanna; Kirby, Evan N.

    2018-06-01

    The stellar halo and tidal streams of M31 provide an essential counterpoint to the same structures around the Milky Way (MW). While measurements of [Fe/H] and [$\\alpha$/Fe] have been made in the MW, little is known about the detailed chemical abundances of the M31 system. To make progress with existing telescopes, we expand upon the technique first presented by Kirby et al., applying spectral synthesis to medium-resolution spectroscopy at lower spectral resolution (R $\\sim$ 1800) across an optical range (4100~\\AA \\ $<$ $\\lambda$ $<$ 9100~\\AA) that extends down the blue. We have obtained deep spectra of red giants in the tidal streams, smooth halo, and disk of M31 using the DEIMOS 600ZD grating, resulting in higher signal-to-noise per spectral resolution element (S/N $\\sim$ 30 \\AA$^{-1}$). By applying our technique to red giant stars in MW globular clusters with higher-resolution ($R$ $\\sim$ 6000) spectra in the blue (4100 - 6300 \\AA), we demonstrate that our technique reproduces previous measurements derived from the red side of the optical (6300 - 9100 \\AA). For the first time, we present measurements of [Fe/H] and [$\\alpha$/Fe] of sufficient quality and sample size to construct quantitative models of galactic chemical evolution in the M31 system.

  8. CHEMICAL ABUNDANCES IN THE EXTERNALLY POLLUTED WHITE DWARF GD 40: EVIDENCE OF A ROCKY EXTRASOLAR MINOR PLANET

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Klein, B.; Jura, M.; Zuckerman, B.

    2010-02-01

    We present Keck/High Resolution Echelle Spectrometer data with model atmosphere analysis of the helium-dominated polluted white dwarf GD 40, in which we measure atmospheric abundances relative to helium of nine elements: H, O, Mg, Si, Ca, Ti, Cr, Mn, and Fe. Apart from hydrogen, whose association with the other contaminants is uncertain, this material most likely accreted from GD 40's circumstellar dust disk whose existence is demonstrated by excess infrared emission. The data are best explained by accretion of rocky planetary material, in which heavy elements are largely contained within oxides, derived from a tidally disrupted minor planet at leastmore » the mass of Juno, and probably as massive as Vesta. The relatively low hydrogen abundance sets an upper limit of 10% water by mass in the inferred parent body, and the relatively high abundances of refractory elements, Ca and Ti, may indicate high-temperature processing. While the overall constitution of the parent body is similar to the bulk Earth being over 85% by mass composed of oxygen, magnesium, silicon, and iron, we find n(Si)/n(Mg) = 0.30 +- 0.11, significantly smaller than the ratio near unity for the bulk Earth, chondrites, the Sun, and nearby stars. This result suggests that differentiation occurred within the parent body.« less

  9. Niobium in R And (S6, 6e) and HR 1105 (S5, 3). [S star abundance

    NASA Technical Reports Server (NTRS)

    Davis, D. N.

    1985-01-01

    Lines of the first multiplet of niobium are strong in R And and HR 1105. These lines are also present in other S stars: HR 8714, R Cam, V Cnc, R CMi, and T Sgr. They are also visible in the M stars, Beta-Peg and Mu-UMa. An approximation to the abundance ratio, Nb/Fe, has been deduced from pairs of lines having nearly equal intensity. In R And, the ratio is about 200 times the solar value. It is hoped that good plates will soon be obtained for the near infrared region, so that the significant Nb/Rb abundance ratio may be determined.

  10. Contribution of Massive Stars to the Production of Neutron Capture Elements

    NASA Astrophysics Data System (ADS)

    Federman, Steven

    2010-09-01

    Elements beyond the Fe-peak must be synthesized through neutron-capture processes. With the aim of understanding the contribution of massive stars to the synthesis of neutron-capture elements during the current epoch, we propose an archival survey of interstellar arsenic, cadmium, tin, and lead. Nucleosynthesis via the weak slow process and the rapid process are the routes involving massive stars, while the main slow process arises from the evolution of low-mass stars. Ultraviolet lines for the dominant ions for each element will be used to extract interstellar abundances. The survey involves about forty sight lines, many of which are associated with regions of massive star formation shaped by core-collapse supernovae {SNe II}. The sample will increase the number of published determinations by factors of 2 to 5. HST spectra are the only means for determining the elemental abundances for this set of species in diffuse interstellar clouds. The survey contains directions that are both molecule poor and molecule rich, thereby enabling us to examine the overall level of depletion onto grains as a function of gas density. Complementary laboratory determinations of oscillator strengths will place the interstellar measurements on an absolute scale. The results from the proposed study will be combined with published interstellar abundances for other neutron capture elements and the suite of measurements will be compared to results from stars throughout the history of the Galaxy.

  11. Cosmological quantum chromodynamics, neutron diffusion, and the production of primordial heavy elements

    NASA Technical Reports Server (NTRS)

    Applegate, J. H.; Hogan, Craig J.; Scherrer, R. J.

    1988-01-01

    A simple one-dimensional model is used to describe the evolution of neutron density before and during nucleosynthesis in a high-entropy bubble left over from the cosmic quark-hadron phase transition. It is shown why cosmic nucleosynthesis in such a neutron-rich environment produces a surfeit of elements heavier than lithium. Analytical and numerical techniques are used to estimate the abundances of carbon, nitrogen, and heavier elements up to Ne-22. A high-density neutron-rich region produces enough primordial N-14 to be observed in stellar atmospheres. It shown that very heavy elements may be created in a cosmological r-process; the neutron exposure in the neutron-rich regions is large enough for the Ne-22 to trigger a catastrophic r-process runaway in which the quantity of heavy elements doubles in much less than an expansion time due to fission cycling. A primordial abundance of r-process elements is predicted to appear as an excess of rare earth elements in extremely metal-poor stars.

  12. Abundance, distribution and bioavailability of major and trace elements in surface sediments from the Cai River estuary and Nha Trang Bay (South China Sea, Vietnam)

    NASA Astrophysics Data System (ADS)

    Koukina, S. E.; Lobus, N. V.; Peresypkin, V. I.; Dara, O. M.; Smurov, A. V.

    2017-11-01

    Major (Si, Al, Fe, Ti, Mg, Ca, Na, K, S, P), minor (Mn) and trace (Li, V, Cr, Co, Ni, Cu, Zn, As, Sr, Zr, Mo, Cd, Ag, Sn, Sb, Cs, Ba, Hg, Pb, Bi and U) elements, their chemical forms and the mineral composition, organic matter (TOC) and carbonates (TIC) in surface sediments from the Cai River estuary and Nha Trang Bay were first determined along the salinity gradient. The abundance and ratio of major and trace elements in surface sediments are discussed in relation to the mineralogy, grain size, depositional conditions, reference background and SQG values. Most trace-element contents are at natural levels and are derived from the composition of rocks and soils in the watershed. A severe enrichment of Ag is most likely derived from metal-rich detrital heavy minerals such as Ag-sulfosalts. Along the salinity gradient, several zones of metal enrichment occur in surface sediments because of the geochemical fractionation of the riverine material. The parts of actually and potentially bioavailable forms (isolated by four single chemical reagent extractions) are most elevated for Mn and Pb (up to 36% and 32% of total content, respectively). The possible anthropogenic input of Pb in the region requires further study. Overall, the most bioavailable parts of trace elements are associated with easily soluble amorphous Fe and Mn oxyhydroxides. The sediments are primarily enriched with bioavailable metal forms in the riverine part of the estuary. Natural (such as turbidities) and human-generated (such as urban and industrial activities) pressures are shown to influence the abundance and speciation of potential contaminants and therefore change their bioavailability in this estuarine system.

  13. What Factors Control Platinum-Group Element (PGE) Abundances in Basalts From the Ontong Java Plateau?

    NASA Astrophysics Data System (ADS)

    Chazey, W. J.; Neal, C. R.

    2002-12-01

    Eleven samples encompassing four sites drilled by Ocean Drilling Program Leg 192 to the Ontong Java Plateau (OJP) were analyzed for major, trace and platinum-group (PGEs: Ir, Ru, Rh, Pt, and Pd) elements. Based on major and trace element chemistry, these are divided into two groups: a primitive group, which was newly discovered on Leg 192, and Kwaimbaita-type basalts, which are ubiquitous on the OJP (cf. Tejada et al., 2002, J. Pet. 43:449). The primitive group is relatively enriched in MgO, Ni, and Cr and relatively depleted in incompatible elements compared to the Kwaimbaita-type basalts. Petrography indicates that the fractionating phases during emplacement of both types of basalts were olivine and Cr-spinel +/- plagioclase +/- cpx. Normalized PGE profiles are fractionated, but exhibit a flattening between Ru and Ir and occasionally an enrichment in Ir. It has been shown that chromite can preferentially incorporate Os and Ru (Kd ?150) over Ir (Kd ?100), which may account for the Ir and Ru systematics. We do not consider sulfide to be a factor in fractionating the PGEs because it is either absent or present as a trace phase in these basalts and the OJP basalts are sulfur undersaturated (Michael and Cornell, 1996, EOS 77:714). Additionally, the primitive samples from the OJP also have Cu/Pd ratios (4500-8000) that are roughly similar to primitive mantle (7300), and have a generally flat transition from Pd to Y on a primitive mantle-normalized plot. It is unlikely that these samples reached sulfur saturation. The Kwaimbaita-type basalts have slightly elevated Cu/Pd ratios (9000-14000). While there are subtle differences between the PGE profiles of basalts from the Leg 192 drill cores compared to OJP basalts from subaerial outcrops in the Solomon Islands (e.g., the former have general lower Pt/Rh and higher Rh/Ru ratios), it is apparent that silicate and oxide phases are controlling the PGE profiles and abundances. For example, the six samples analyzed from Site

  14. Clustering in the stellar abundance space

    NASA Astrophysics Data System (ADS)

    Boesso, R.; Rocha-Pinto, H. J.

    2018-03-01

    We have studied the chemical enrichment history of the interstellar medium through an analysis of the n-dimensional stellar abundance space. This work is a non-parametric analysis of the stellar chemical abundance space. The main goal is to study the stars from their organization within this abundance space. Within this space, we seek to find clusters (in a statistical sense), that is, stars likely to share similar chemo-evolutionary history, using two methods: the hierarchical clustering and the principal component analysis. We analysed some selected abundance surveys available in the literature. For each sample, we labelled the group of stars according to its average abundance curve. In all samples, we identify the existence of a main enrichment pattern of the stars, which we call chemical enrichment flow. This flow is set by the structured and well-defined mean rate at which the abundances of the interstellar medium increase, resulting from the mixture of the material ejected from the stars and stellar mass-loss and interstellar medium gas. One of the main results of our analysis is the identification of subgroups of stars with peculiar chemistry. These stars are situated in regions outside of the enrichment flow in the abundance space. These peculiar stars show a mismatch in the enrichment rate of a few elements, such as Mg, Si, Sc and V, when compared to the mean enrichment rate of the other elements of the same stars. We believe that the existence of these groups of stars with peculiar chemistry may be related to the accretion of planetary material on to stellar surfaces or may be due to production of the same chemical element by different nucleosynthetic sites.

  15. Spatial Models of Abundance and Habitat Preferences of Commerson’s and Peale’s Dolphin in Southern Patagonian Waters

    PubMed Central

    Dellabianca, Natalia A.; Pierce, Graham J.; Raya Rey, Andrea; Scioscia, Gabriela; Miller, David L.; Torres, Mónica A.; Paso Viola, M. Natalia; Schiavini, Adrián C. M.

    2016-01-01

    Commerson’s dolphins (Cephalorhynchus c. commersonii) and Peale’s dolphins (Lagenorhynchus australis) are two of the most common species of cetaceans in the coastal waters of southwest South Atlantic Ocean. Both species are listed as Data Deficient by the IUCN, mainly due to the lack of information about population sizes and trends. The goal of this study was to build spatially explicit models for the abundance of both species in relation to environmental variables using data collected during eight scientific cruises along the Patagonian shelf. Spatial models were constructed using generalized additive models. In total, 88 schools (212 individuals) of Commerson’s dolphin and 134 schools (465 individuals) of Peale’s dolphin were recorded in 8,535 km surveyed. Commerson’s dolphin was found less than 60 km from shore; whereas Peale’s dolphins occurred over a wider range of distances from the coast, the number of animals sighted usually being larger near or far from the coast. Fitted models indicate overall abundances of approximately 22,000 Commerson’s dolphins and 20,000 Peale’s dolphins in the total area studied. This work provides the first large-scale abundance estimate for Peale’s dolphin in the Atlantic Ocean and an update of population size for Commerson’s dolphin. Additionally, our results contribute to baseline data on suitable habitat conditions for both species in southern Patagonia, which is essential for the implementation of adequate conservation measures. PMID:27783627

  16. R-process enrichment from a single event in an ancient dwarf galaxy.

    PubMed

    Ji, Alexander P; Frebel, Anna; Chiti, Anirudh; Simon, Joshua D

    2016-03-31

    Elements heavier than zinc are synthesized through the rapid (r) and slow (s) neutron-capture processes. The main site of production of the r-process elements (such as europium) has been debated for nearly 60 years. Initial studies of trends in chemical abundances in old Milky Way halo stars suggested that these elements are produced continually, in sites such as core-collapse supernovae. But evidence from the local Universe favours the idea that r-process production occurs mainly during rare events, such as neutron star mergers. The appearance of a plateau of europium abundance in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early Universe, but only under the assumption that no gas accretes into those dwarf galaxies; gas accretion favours continual r-process enrichment in these systems. Furthermore, the universal r-process pattern has not been cleanly identified in dwarf spheroidals. The smaller, chemically simpler, and more ancient ultrafaint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process. Reticulum II is one such galaxy. The abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those in other old stars. Here, we report that seven of the nine brightest stars in Reticulum II, observed with high-resolution spectroscopy, show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern beyond barium. The enhancement seen in this 'r-process galaxy' is two to three orders of magnitude higher than that detected in any other ultrafaint dwarf galaxy. This implies that a single, rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with the source being ordinary core-collapse supernovae, but consistent with other possible sources, such as neutron star mergers.

  17. Multi-Temperature Emission and Abundances in the Hot Gaseous Halo

    NASA Technical Reports Server (NTRS)

    Kim, Dong-Woo; Mushotzky, Richard F. (Technical Monitor)

    2003-01-01

    We present the results of XMM-Newton observations of NGC 507, a dominant elliptical galaxy in a small group of galaxies. After carefully considering various systematic effects on abundance measurements, we report 'super-solar' metal abundances (both Fe and a-elements) present in the hot ISM: ZFe = 2-3 times solar with an observational limit of as high as 4 times solar inside the D25 ellipse of NGC 507. This is the highest ZFe reported so far, and fully consistent with those expected by the stellar evolution models where heavy elements are enriched by both type II and Ia supernovae ejecta. No unusual constraint either on the SNe rate or IMF is required. Among various factors affecting the accurate abundance measurement, we find that selecting a proper emission model is most important. As opposed to the X-ray spectral data with limited s/n and poor spatial/spectral resolution obtained in the previous missions, the spatially resolved XMM spectra provide enough statistics to untie the model-Z degeneracy and statistically require at least 3 emission components in each concentric shell (2 thermal components representing a finite range of kT in the hot ISM + 1 hard LMXB component). We show that a simpler model (such as a two-component model) produce a much lower best-fit ZFe. The abundances of a-elements (most accurately determined by Si) is also found to be super-solar and its radio to Fe is close to the solar ratio, suggesting a considerably contribution of heavy elements from Type Ia SNe. We estimate approx. 70% of MFe in the hot ISM originate from Type Ia.

  18. Abundance analysis of the supergiant stars HD 80057 and HD 80404 based on their UVES Spectra

    NASA Astrophysics Data System (ADS)

    Tanrıverdi, T.; Baştürk, Ö.

    2016-08-01

    This study presents elemental abundances of the early A-type supergiant HD 80057 and the late A-type supergiant HD 80404. High resolution and high signal-to-noise ratio spectra published by the UVES Paranal Observatory Project (Bagnulo et al., 2003) were analyzed to compute their elemental abundances using ATLAS9 (Kurucz, 1993; 2005; Sbordone et al., 2004). In our analysis we assumed local thermodynamic equilibrium. The atmospheric parameters of HD 80057 used in this study are from Firnstein and Przybilla (2012), and that of HD 80404 are derived from spectral energy distribution, ionization equilibria of Cr I/II and Fe I/II, the fits to the wings of Balmer and Paschen lines as Teff = 7700 ± 150 K and log g = 1.60 ± 0.15 (in cgs). The microturbulent velocities of HD 80057 and HD 80404 have been determined as 4.3 ± 0.1 and 2.2 ± 0.0 km s^-1, respectively. The rotational velocities are 15 ± 1 and 7 ± 2 km s^-1 and their macroturbulence velocities are 24 ± 2 and 2 ± 1 km s^1. We have given the abundances of 25 ions of 19 elements for HD 80057 and 36 ions of 25 elements for HD 80404. The abundances are close to solar values, except for some elements (Na, Sc, Ti, V, Ba, and Sr). We have found the metallicities [M/H] for HD 80057 and HD 80404 as -0.16 ± 0.24 and -0.04 ± 0.16 dex, respectively. The evolutionary status of these stars are discussed and their nitrogen-to-carbon (N/C) and nitrogen-to-oxygen (N/O) ratios show that they are in their blue supergiant phase before the red supergiant region.

  19. RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guennou, C.; Hahn, M.; Savin, D. W., E-mail: cguennou@iac.es

    2015-07-10

    We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) <10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for elements with a high-FIP (>10 eV). We have used Extreme Ultraviolet Imaging Spectrometer observations made on 2007 March 13 and 14 over a ≈24 hr period tomore » characterize abundance variations in plumes and interplumes. To assess their elemental composition, we used a differential emission measure analysis, which accounts for the thermal structure of the observed plasma. We used lines from ions of iron, silicon, and sulfur. From these we estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provide constraints on the formation and heating mechanisms of plumes.« less

  20. Boron Abundances in A and B-type Stars

    NASA Technical Reports Server (NTRS)

    Lambert, David L.

    1997-01-01

    Boron abundances in A- and B-type stars may be a successful way to track evolutionary effects in these hot stars. The light elements - Li, Be, and B - are tracers of exposure to temperatures more moderate than those in which the H-burning CN-cycle operates. Thus, any exposure of surface stellar layers to deeper layers will affect these light element abundances. Li and Be are used in this role in investigations of evolutionary processes in cool stars, but are not observable in hotter stars. An investigation of boron, however, is possible through the B II 1362 A resonance line. We have gathered high resolution spectra from the IUE database of A- and B-type stars near 10 solar mass for which nitrogen abundances have been determined. The B II 1362 A line is blended throughout; the temperature range of this program, requiring spectrum syntheses to recover the boron abundances. For no star could we synthesize the 1362 A region using the meteoritic/solar boron abundance of log e (B) = 2.88; a lower boron abundance was necessary which may reflect evolutionary effects (e.g., mass loss or mixing near the main-sequence), the natal composition of the star forming regions, or a systematic error in the analyses (e.g., non-LTE effects). Regardless of the initial boron abundance, and despite the possibility of non-LTE effects, it seems clear that boron is severely depleted in some stars. It may be that the nitrogen and boron abundances are anticorrelated, as would be expected from mixing between the H-burning and outer stellar layers. If, as we suspect, a residue of boron is present in the A-type supergiants, we may exclude a scenario in which mixing occurs continuously between the surface and the deep layers operating the CN-cycle. Further exploitation of the B II 1362 A line as an indicator of the evolutionary status of A- and B-type stars will require a larger stellar sample to be observed with higher signal-to-noise as attainable with the Hubble Space Telescope.

  1. New Fission Fragment Distributions and r-Process Origin of the Rare-Earth Elements

    NASA Astrophysics Data System (ADS)

    Goriely, S.; Sida, J.-L.; Lemaître, J.-F.; Panebianco, S.; Dubray, N.; Hilaire, S.; Bauswein, A.; Janka, H.-T.

    2013-12-01

    Neutron star (NS) merger ejecta offer a viable site for the production of heavy r-process elements with nuclear mass numbers A≳140. The crucial role of fission recycling is responsible for the robustness of this site against many astrophysical uncertainties, but calculations sensitively depend on nuclear physics. In particular, the fission fragment yields determine the creation of 110≲A≲170 nuclei. Here, we apply a new scission-point model, called SPY, to derive the fission fragment distribution (FFD) of all relevant neutron-rich, fissioning nuclei. The model predicts a doubly asymmetric FFD in the abundant A≃278 mass region that is responsible for the final recycling of the fissioning material. Using ejecta conditions based on relativistic NS merger calculations, we show that this specific FFD leads to a production of the A≃165 rare-earth peak that is nicely compatible with the abundance patterns in the Sun and metal-poor stars. This new finding further strengthens the case of NS mergers as possible dominant origin of r nuclei with A≳140.

  2. Do stellar and nebular abundances in the Cocoon nebula agree?

    NASA Astrophysics Data System (ADS)

    García-Rojas, J.; Simón-Díaz, S.; Esteban, C.

    2015-05-01

    The Cocoon nebula is an apparently spherical Galactic HII region ionized by a single star (BD+46 3474). This nebula seems to be appropriate to investigate the chemical behavior of oxygen and other heavy elements from two different points of view: a detailed analysis of the chemical content of the ionized gas through nebular spectrophotometry and a detailed spectroscopic analysis of the spectrum of the ionizing star using the state-of-the-art stellar atmosphere modelling. In this poster we present the results from a set of high-quality observations, from 2m-4m class telescopes, including the optical spectrum of the ionizing star BD+46 3474, along with long-slit spatially resolved spectroscopy of the nebula. We have used state-of-the-art stellar atmosphere codes to determine stellar parameters and the chemical content of several heavy elements. Traditional nebular techniques along with updated atomic data have been used to compute gaseous abundances of O, N and S in the Cocoon nebula. Thanks to the low ionization degree of the nebula, we could determine total abundances directly from observable ions (no ionization correction factors were needed) for three of the analyzed elements (O, S, and N). The derived stellar and nebular abundances are compared and the influence of the possible presence of the so-called temperature fluctuations on the nebula is discussed. The results of this study are presented in more detail in García-Rojas, Simón-Díaz & Esteban 2014, A&A, 571, A93.

  3. Cosmic-ray abundances of Sn, Te, Xe, and Ba nuclei measured on HEAO 3

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Israel, M. H.; Klarmann, J.; Fickle, R. K.; Waddington, C. J.; Garrard, T. L.; Krombel, K. E.; Stone, E. C.

    1983-01-01

    The results of an analysis of HEAO 3 Heavy Nuclei Experimental data covering 440 days of observations of Sn-Ba nuclei in cosmic rays are reported. The particles were detected by a Cernkov counter, and a Z-squared ceiling was calculated to normalize the histograms produced. The observed large abundance of Sn and Ba relative to other elements in the region of interest indicated a predominance of the s-process in the source of the particles. When account was taken of first ionization potential effects, the data indicated that the material could be solar system in origin. A source dominated by the r-process nucleosynthesis was ruled out at the 0.93 confidence level.

  4. Beryllium and Boron abundances in population II stars

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The scientific focus of this program was to undertake UV spectroscopic abundance analyses of extremely metal poor stars with attention to determining abundances of light elements such as beryllium and boron. The abundances are likely to reflect primordial abundances within the early galaxy and help to constrain models for early galactic nucleosynthesis. The general metal abundances of these stars are also important for understanding stellar evolution.

  5. Studies of hot B subdwarfs. III - Carbon, nitrogen, and silicon abundances in three sdB stars

    NASA Technical Reports Server (NTRS)

    Lamontagne, R.; Wesemael, F.; Fontaine, G.; Sion, E. M.

    1985-01-01

    Optical and high-dispersion IUE observations of three hot B subdwarfs (UV 1758 + 36, Ton S-227, and Feige 65) are presented. These data are analyzed with model atmosphere techniques, and element abundances for C, N, and Si are derived. The abundances are either near (N) or below (C, Si) the solar value; large variations (1) in the extent of underabundances of carbon and silicon among the objects, as well as (2) in the abundances (with respect to the solar values) characterizing each star are observed. A preliminary interpretation of the observed variations in these and other hot subdwarfs in terms of radiative forces disrupting the downward diffusion of heavy elements is presented.

  6. Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program. II. Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu

    NASA Astrophysics Data System (ADS)

    Delgado Mena, E.; Tsantaki, M.; Adibekyan, V. Zh.; Sousa, S. G.; Santos, N. C.; González Hernández, J. I.; Israelian, G.

    2017-10-01

    Aims: To understand the formation and evolution of the different stellar populations within our Galaxy it is essential to combine detailed kinematical and chemical information for large samples of stars. The aim of this work is to explore the chemical abundances of neutron capture elements which are a product of different nucleosynthesis processes taking place in diverse objects in the Galaxy, such as massive stars, asymptotic giant branch (AGB) stars and supernovae (SNe) explosions. Methods: We derive chemical abundances of Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu for a large sample of more than 1000 FGK dwarf stars with high-resolution (R 115 000) and high-quality spectra from the HARPS-GTO program. The abundances are derived by a standard local thermodynamic equilibrium (LTE) analysis using measured equivalent widths (EWs) injected to the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Results: We find that thick disc stars are chemically disjunct for Zn and Eu and also show on average higher Zr but lower Ba and Y than the thin disc stars. We also discovered that the previously identified high-α metal-rich population is also enhanced in Cu, Zn, Nd, and Eu with respect to the thin disc but presents lower Ba and Y abundances on average, following the trend of thick disc stars towards higher metallities and further supporting the different chemical composition of this population. By making a qualitative comparison of O (pure α), Mg, Eu (pure r-process), and s-process elements we can distinguish between the contribution of the more massive stars (SNe II for α and r-process elements) and the lower mass stars (AGBs) whose contribution to the enrichment of the Galaxy is delayed, due to their longer lifetimes. The ratio of heavy-s to light-s elements of thin disc stars presents the expected behaviour (increasing towards lower metallicities) and can be explained by a major contribution of low-mass AGB stars for s-process production at disc metallicities. However, the

  7. Origin of the main r-process elements

    NASA Astrophysics Data System (ADS)

    Otsuki, K.; Truran, J.; Wiescher, M.; Gorres, J.; Mathews, G.; Frekers, D.; Mengoni, A.; Bartlett, A.; Tostevin, J.

    2006-07-01

    The r-process is supposed to be a primary process which assembles heavy nuclei from a photo-dissociated nucleon gas. Hence, the reaction flow through light elements can be important as a constraint on the conditions for the r-process. We have studied the impact of di-neutron capture and the neutron-capture of light (Z<10) elements on r-process nucleosynthesis in three different environments: neutrino-driven winds in Type II supernovae; the prompt explosion of low mass supernovae; and neutron star mergers. Although the effect of di-neutron capture is not significant for the neutrino-driven wind model or low-mass supernovae, it becomes significant in the neutron-star merger model. The neutron-capture of light elements, which has been studied extensively for neutrino-driven wind models, also impacts the other two models. We show that it may be possible to identify the astrophysical site for the main r-process if the nuclear physics uncertainties in current r-process calculations could be reduced.

  8. Finite-element simulation of ceramic drying processes

    NASA Astrophysics Data System (ADS)

    Keum, Y. T.; Jeong, J. H.; Auh, K. H.

    2000-07-01

    A finite-element simulation for the drying process of ceramics is performed. The heat and moisture movements in green ceramics caused by the temperature gradient, moisture gradient, conduction, convection and evaporation are considered. The finite-element formulation for solving the temperature and moisture distributions, which not only change the volume but also induce the hygro-thermal stress, is carried out. Employing the internally discontinuous interface elements, the numerical divergence problem arising from sudden changes in heat capacity in the phase zone is solved. In order to verify the reliability of the formulation, the drying process of a coal and the wetting process of a graphite epoxy are simulated and the results are compared with the analytical solution and another investigator's result. Finally, the drying process of a ceramic electric insulator is simulated.

  9. CORDIC-based digital signal processing (DSP) element for adaptive signal processing

    NASA Astrophysics Data System (ADS)

    Bolstad, Gregory D.; Neeld, Kenneth B.

    1995-04-01

    The High Performance Adaptive Weight Computation (HAWC) processing element is a CORDIC based application specific DSP element that, when connected in a linear array, can perform extremely high throughput (100s of GFLOPS) matrix arithmetic operations on linear systems of equations in real time. In particular, it very efficiently performs the numerically intense computation of optimal least squares solutions for large, over-determined linear systems. Most techniques for computing solutions to these types of problems have used either a hard-wired, non-programmable systolic array approach, or more commonly, programmable DSP or microprocessor approaches. The custom logic methods can be efficient, but are generally inflexible. Approaches using multiple programmable generic DSP devices are very flexible, but suffer from poor efficiency and high computation latencies, primarily due to the large number of DSP devices that must be utilized to achieve the necessary arithmetic throughput. The HAWC processor is implemented as a highly optimized systolic array, yet retains some of the flexibility of a programmable data-flow system, allowing efficient implementation of algorithm variations. This provides flexible matrix processing capabilities that are one to three orders of magnitude less expensive and more dense than the current state of the art, and more importantly, allows a realizable solution to matrix processing problems that were previously considered impractical to physically implement. HAWC has direct applications in RADAR, SONAR, communications, and image processing, as well as in many other types of systems.

  10. Abundances in metal-rich stars. Detailed abundance analysis of 47 G and K dwarf stars with [Me/H] > 0.10 dex

    NASA Astrophysics Data System (ADS)

    Feltzing, S.; Gustafsson, B.

    1998-04-01

    We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni as well as for a number of s-elements for 47 G and K dwarf, with [Me/H]>0.1 dex. The selection of stars was based on their kinematics as well as on their uvby-beta photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the evolution around the solar orbit. A few Extreme Population I stars were included in the latter sample. The stars have -0.1 dex < [Fe/H] < 0.42 dex. The spectroscopic [Fe/H] correlate well with the [Me/H] derived from uvby-beta photometry. We find that the elemental abundances of Mg, Al, Si, Ca, Ti, Cr and Ni all follow [Fe/H]. Our data put further constraints on models of galactic chemical evolution, in particular of Cr, Mn and Co which have not previously been studied for dwarf stars with [Me/H] >0.1 dex. The increase in [Na/Fe] and [Al/Fe] as a function of [Fe/H] found previously by \\cite[Edvardsson et al. (1993a)]{Edv93} has been confirmed for [Na/Fe]. This upturning relation, and the scatter around it, are shown not to be due to a mixture of populations with different mean distances to the galactic centre. We do not confirm the same trend for aluminium, which is somewhat surprising since both these elements are thought to be produced in the same environments in the pre-supernova stars. Nor have we been able to trace any tendency for relative abundances of O, Si, and Ti relative to Fe to vary with the stellar velocities, i.e. the stars present mean distance to the galactic centre. These results imply that there is no significant difference in the chemical evolution of the different stellar populations for stars with [Me/H]>0.1 dex. We find that [O/Fe] continue to decline with increasing [Fe/H] and that oxygen and europium correlate well. However [Si/Fe] and [Ca/Fe] seem to stay constant. A real (``cosmic'') scatter in [Ti/Fe] at given [Fe/H] is suggested as well as

  11. The abundances of major elements in Cas A and Tycho supernova remnants

    NASA Technical Reports Server (NTRS)

    Gorenstein, P.

    1995-01-01

    The objective of this program was to map the abundances of major elements such as O, Si, S, and Fe in the supernova remnants, Tycho and Cas A. The approach was based upon using archival cosmic X-ray data from several space missions, notably, the Einstein Observatory, EXOSAT, ROSAT, BBSRT, and ASCA. Two of the missions, Einstein and ROSAT, had high resolution telescopes that provided excellent images, but no spectral information. Two missions with much poorer resolution telescopes, BBXRT and ASCA, gave good spectral information through pulse height of signals in their cooled solid state detector, but rather crude spatial information. Our goal was to extract spectral information from the combined analysis of the Einstein and ROSAT images of Cas A and Tycho and to verify or refine the spectral map by checking its agreement with the BBSRT or ASCA spectra results for larger regions. In particular, we note that the Einstein and ROSAT telescopes have different spectral responses. The Einstein bandwidth includes the 2-4 keV region which is absent from ROSAT. Hence, by forming linear combinations of the Einstein and ROSAT images, we are able to resolve the contributions of the 0.5-2 keV band from the 2-4 keV band. The former contains lines of O and Fe while the latter is dominated by Si and S. We correct for the expansion that has taken place in the remnants during the ten-year interval between the Einstein and ROSAT measurements, but we must assume that no significant spectral changes have occurred during that time. The analysis of the Tycho SNR was completed and the results have been published. A copy of the paper is included. The analysis of Cas A has proved to be more complicated. It is continuing with support from another program. Part of the problem may be due to difficulties in the aspect information which is needed to precisely register the ROSAT and Einstein images.

  12. Carbon abundances, major element chemistry, and mineralogy of hydrated interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Thomas, K. L.; Mckay, D. S.

    1993-01-01

    Hydrated interplanetary dust particles (IDP's) comprise a major fraction of the interplanetary dust particles collected in the stratosphere. While much is known about the mineralogy and chemistry of hydrated IDP's, little is known about the C abundance in this class of IDP's, the nature of the C-bearing phases, and how the C abundance is related to other physical properties of hydrated IDP's. Bulk compositional data (including C and O) for 11 hydrated IDP's that were subsequently examined by the transition electron microscopy (TEM) to determine their mineralogy and mineral chemistry are reported. Our analysis indicates that these hydrated IDP's are strongly enriched in C relative to the most C-rich meteorites. The average abundance of C in these hydrated IDP's is 4X CI chondrite values. The bulk compositions (including C and O) of 11 hydrated IDP's were determined by thin-window, energy-dispersive x ray (EDX) spectroscopy of the uncoated IDP's on Be substrates in the scanning electron microscopy (SEM). As a check on our C measurements, one of the IDP's (L2006H5) was embedded in glassy S, and microtome thin sections were prepared and placed onto Be substrates. Thin-film EDX analyses of multiple thin sections of L2006H5 show good agreement with the bulk value determined in the SEM. Following EDX analysis, the mineralogy and mineral chemistry of each IDP was determined by analyzing ultramicrotome thin sections in a TEM equipped with an EDX spectrometer.

  13. NETL’s Rare Earth Elements Research

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None

    The National Energy Technology Laboratory has established a Rare Earth Elements (REE) program. REEs are a series of 17 chemical elements found in the Earth’s crust. They are an essential component to technology, health care, transportation and national defense.

  14. Evolutionary transitions in the Asteraceae coincide with marked shifts in transposable element abundance.

    PubMed

    Staton, S Evan; Burke, John M

    2015-08-20

    The transposable element (TE) content of the genomes of plant species varies from near zero in the genome of Utricularia gibba to more than 80% in many species. It is not well understood whether this variation in genome composition results from common mechanisms or stochastic variation. The major obstacles to investigating mechanisms of TE evolution have been a lack of comparative genomic data sets and efficient computational methods for measuring differences in TE composition between species. In this study, we describe patterns of TE evolution in 14 species in the flowering plant family Asteraceae and 1 outgroup species in the Calyceraceae to investigate phylogenetic patterns of TE dynamics in this important group of plants. Our findings indicate that TE families in the Asteraceae exhibit distinct patterns of non-neutral evolution, and that there has been a directional increase in copy number of Gypsy retrotransposons since the origin of the Asteraceae. Specifically, there is marked increase in Gypsy abundance at the origin of the Asteraceae and at the base of the tribe Heliantheae. This latter shift in genome composition has had a significant impact on the diversity and abundance distribution of TEs in a lineage-specific manner. We show that the TE-driven expansion of plant genomes can be facilitated by just a few TE families, and is likely accompanied by the modification and/or replacement of the TE community. Importantly, large shifts in TE composition may be correlated with major of phylogenetic transitions.

  15. Abundance analysis of a CEMP-no star in the Carina dwarf spheroidal galaxy

    NASA Astrophysics Data System (ADS)

    Susmitha, A.; Koch, A.; Sivarani, T.

    2017-10-01

    Carbon-enhanced metal-poor (CEMP) stars bear important imprints of the early chemical enrichment of any stellar system. While these stars are known to exist in copious amounts in the Milky Way halo, detailed chemical abundance data from the faint dwarf spheroidal (dSph) satellites are still sparse, although the relative fraction of these stars increases with decreasing metallicity. Here, we report the abundance analysis of a metal-poor ([ Fe / H ] = - 2.5 dex), carbon-rich ([C/Fe] = 1.4 dex) star, ALW-8, in the Carina dSph using high-resolution spectroscopy obtained with the ESO/UVES instrument. Its spectrum does not indicate any over-enhancements of neutron capture elements. Thus classified as a CEMP-no star, this is the first detection of this kind of star in Carina. Another of our sample stars, ALW-1, is shown to be a CEMP-s star, but its immediate binarity prompted us to discard it from a detailed analysis. The majority of the 18 chemical elements we measured are typical of Carina's field star population and also agree with CEMP stars in other dSph galaxies. Similar to the only known CEMP-no star in the Sculptor dSph and the weak-r-process star HD 122563, the lack of any strong barium-enhancement is accompanied by a moderate overabundance in yttrium, indicating a weak r-process activity. The overall abundance pattern confirms that, also in Carina, the formation site for CEMP-no stars has been affected by both faint supernovae and by standard core collapse supernovae. Whichever process was responsible for the heavy element production in ALW-8 must be a ubiquitous source to pollute the CEMP-no stars, acting independently of the environment such as in the Galactic halo or in dSphs. Based on observations collected at the European Southern Observatory at Paranal, Chile; Large Programme proposal 171.B- 0520.Table A.1 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http

  16. Abundance Analysis of the Helium Weak Star 20-TAURI

    NASA Astrophysics Data System (ADS)

    Mon, M.; Hirata, R.; Sadakane, K.

    An abundance analysis of the helium-weak star 20 Tauri is performed with a fully line-blanketed model atmosphere. The adopted atmospheric parameters are Teff =12600 K and log g=3.2. These values are lower by about 1000 K in Teff and 0.3 in log g than those used in previous investigations, and 20 Tau is the coolest star among the group of helium-weak star. A value of log N(He)/N(H)=-1.7 is found from the average of six He I lines. Mg, Si, Ca, and Ni are underabundant, while P and Mn are overabundant. The abundances of C, Ti, Cr, and Fe coincide with the solar values within ±0.3 dex. Upper limits of the abundances of S, Sc, and Sr are estimated and these elements are not overabundant. The observed abundance pattern in 20 Tau is quite different from those in other helium-weak stars, while it shows a mild characteristic of Mn-Hg stars.

  17. Abundances of Local Group Globular Clusters Using High Resolution Integrated Light Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakari, Charli; McWilliam, A.; Venn, K.; Shetrone, M. D.; Dotter, A. L.; Mackey, D.

    2014-01-01

    Abundances and kinematics of extragalactic globular clusters provide valuable clues about galaxy and globular cluster formation in a wide variety of environments. In order to obtain such information about distant, unresolved systems, specific observational techniques are required. An Integrated Light Spectrum (ILS) provides a single spectrum from an entire stellar population, and can therefore be used to determine integrated cluster abundances. This dissertation investigates the accuracy of high resolution ILS analysis methods, using ILS (taken with the Hobby-Eberly Telescope) of globular clusters associated with the Milky Way (47 Tuc, M3, M13, NGC 7006, and M15) and then applies the method to globular clusters in the outer halo of M31 (from the Pan-Andromeda Archaeological Survey, or PAndAS). Results show that: a) as expected, the high resolution method reproduces individual stellar abundances for elements that do not vary within a cluster; b) the presence of multiple populations does affect the abundances of elements that vary within the cluster; c) certain abundance ratios are very sensitive to systematic effects, while others are not; and d) certain abundance ratios (e.g. [Ca/Fe]) can be accurately obtained from unresolved systems. Applications of ILABUNDS to the PAndAS clusters reveal that accretion may have played an important role in the formation of M31's outer halo.

  18. Parallel processing in finite element structural analysis

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.

    1987-01-01

    A brief review is made of the fundamental concepts and basic issues of parallel processing. Discussion focuses on parallel numerical algorithms, performance evaluation of machines and algorithms, and parallelism in finite element computations. A computational strategy is proposed for maximizing the degree of parallelism at different levels of the finite element analysis process including: 1) formulation level (through the use of mixed finite element models); 2) analysis level (through additive decomposition of the different arrays in the governing equations into the contributions to a symmetrized response plus correction terms); 3) numerical algorithm level (through the use of operator splitting techniques and application of iterative processes); and 4) implementation level (through the effective combination of vectorization, multitasking and microtasking, whenever available).

  19. Discrepancy between mRNA and protein abundance: Insight from information retrieval process in computers

    PubMed Central

    Wang, Degeng

    2008-01-01

    Discrepancy between the abundance of cognate protein and RNA molecules is frequently observed. A theoretical understanding of this discrepancy remains elusive, and it is frequently described as surprises and/or technical difficulties in the literature. Protein and RNA represent different steps of the multi-stepped cellular genetic information flow process, in which they are dynamically produced and degraded. This paper explores a comparison with a similar process in computers - multi-step information flow from storage level to the execution level. Functional similarities can be found in almost every facet of the retrieval process. Firstly, common architecture is shared, as the ribonome (RNA space) and the proteome (protein space) are functionally similar to the computer primary memory and the computer cache memory respectively. Secondly, the retrieval process functions, in both systems, to support the operation of dynamic networks – biochemical regulatory networks in cells and, in computers, the virtual networks (of CPU instructions) that the CPU travels through while executing computer programs. Moreover, many regulatory techniques are implemented in computers at each step of the information retrieval process, with a goal of optimizing system performance. Cellular counterparts can be easily identified for these regulatory techniques. In other words, this comparative study attempted to utilize theoretical insight from computer system design principles as catalysis to sketch an integrative view of the gene expression process, that is, how it functions to ensure efficient operation of the overall cellular regulatory network. In context of this bird’s-eye view, discrepancy between protein and RNA abundance became a logical observation one would expect. It was suggested that this discrepancy, when interpreted in the context of system operation, serves as a potential source of information to decipher regulatory logics underneath biochemical network operation. PMID

  20. Catalyst for elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, M.; Liu, W.

    1995-01-24

    A catalytic reduction process is described for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides high activity and selectivity, as well as stability in the reaction atmosphere, for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over a metal oxide composite catalyst having one of the following empirical formulas: [(FO[sub 2])[sub 1[minus]n](RO)[sub n

  1. Impact of individual nuclear masses on r -process abundances

    DOE PAGES

    Mumpower, M. R.; Surman, R.; Fang, D. -L.; ...

    2015-09-15

    We have performed for the first time a comprehensive study of the sensitivity of r-process nucleosynthesis to individual nuclear masses across the chart of nuclides. Using the latest version (2012) of the Finite-Range Droplet Model, we consider mass variations of ±0.5 MeV and propagate each mass change to all affected quantities, including Q values, reaction rates, and branching ratios. We find such mass variations can result in up to an order of magnitude local change in the final abundance pattern produced in an r-process simulation. As a result, we identify key nuclei whose masses have a substantial impact on abundancemore » predictions for hot, cold, and neutron star merger r-process scenarios and could be measured at future radioactive beam facilities.« less

  2. The Chemical Abundances of Stars in the Halo (CASH) Project. II. New Extremely Metal-poor Stars

    NASA Astrophysics Data System (ADS)

    Krugler, Julie A.; Frebel, A.; Roederer, I. U.; Sneden, C.; Shetrone, M.; Beers, T.; Christlieb, N.

    2011-01-01

    We present new abundance results from the Chemical Abundances of Stars in the Halo (CASH) project. The 500 CASH spectra were observed using the Hobby-Eberly Telescope in "snapshot" mode and are analyzed using an automated stellar parameter and abundance pipeline called CASHCODE. For the 20 most metal-poor stars of the CASH sample we have obtained high resolution spectra using the Magellan Telescope in order to test the uncertainties and systematic errors associated with the snapshot quality (i.e., R 15,000 and S/N 65) HET spectra and to calibrate the newly developed CASHCODE by making a detailed comparison between the stellar parameters and abundances determined from the high resolution and snapshot spectra. We find that the CASHCODE stellar parameters (effective temperature, surface gravity, metallicity, and microturbulence) agree well with the results of the manual analysis of the high resolution spectra. We present the abundances of three newly discovered stars with [Fe/H] < -3.5. For the entire pilot sample, we find typical halo abundance ratios with alpha-enhancement and Fe-peak depletion and a range of n-capture elements. The full CASH sample will be used to derive statistically robust abundance trends and frequencies (e.g. carbon and n-capture), as well as placing constraints on nucleosynthetic processes that occurred in the early universe.

  3. The Alpha Centauri binary system. Atmospheric parameters and element abundances

    NASA Astrophysics Data System (ADS)

    Porto de Mello, G. F.; Lyra, W.; Keller, G. R.

    2008-09-01

    Context: The α Centauri binary system, owing to its duplicity, proximity and brightness, and its components' likeness to the Sun, is a fundamental calibrating object for the theory of stellar structure and evolution and the determination of stellar atmospheric parameters. This role, however, is hindered by a considerable disagreement in the published analyses of its atmospheric parameters and abundances. Aims: We report a new spectroscopic analysis of both components of the α Centauri system, compare published analyses of the system, and attempt to quantify the discrepancies still extant in the determinations of the atmospheric parameters and abundances of these stars. Methods: The analysis is differential with respect to the Sun, based on spectra with R = 35 000 and signal-to-noise ratio ≥1000, and employed spectroscopic and photometric methods to obtain as many independent T_eff determinations as possible. We also check the atmospheric parameters for consistency against the results of the dynamical analysis and the positions of the components in a theoretical HR diagram. Results: The spectroscopic atmospheric parameters of the system are found to be T_eff = (5847 ± 27) K, [Fe/H] = +0.24 ± 0.03, log g = 4.34 ± 0.12, and ξt = 1.46 ± 0.03 km s-1, for α Cen A, and T_eff = (5316 ± 28) K, [Fe/H] = +0.25 ± 0.04, log g = 4.44 ± 0.15, and ξt = 1.28 ± 0.15 km s^-1 for α Cen B. The parameters were derived from the simultaneous excitation & ionization equilibria of Fe I and Fe II lines. T_effs were also obtained by fitting theoretical profiles to the Hα line and from photometric calibrations. Conclusions: We reached good agreement between the three criteria for α Cen A. For α Cen B the spectroscopic T_eff is ~140 K higher than the other two determinations. We discuss possible origins of this inconsistency, concluding that the presence of non-local thermodynamic equilibrium effects is a probable candidate, but we note that there is as yet no consensus on

  4. Isotopic Compositions of the Elements, 2001

    NASA Astrophysics Data System (ADS)

    Böhlke, J. K.; de Laeter, J. R.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P.

    2005-03-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

  5. Solution-Processed Cu2ZnSn(S,Se) 4 Thin-Film Solar Cells Using Elemental Cu, Zn, Sn, S, and Se Powders as Source.

    PubMed

    Guo, Jing; Pei, Yingli; Zhou, Zhengji; Zhou, Wenhui; Kou, Dongxing; Wu, Sixin

    2015-12-01

    Solution-processed approach for the deposition of Cu2ZnSn (S,Se)4 (CZTSSe) absorbing layer offers a route for fabricating thin film solar cell that is appealing because of simplified and low-cost manufacturing, large-area coverage, and better compatibility with flexible substrates. In this work, we present a simple solution-based approach for simultaneously dissolving the low-cost elemental Cu, Zn, Sn, S, and Se powder, forming a homogeneous CZTSSe precursor solution in a short time. Dense and compact kesterite CZTSSe thin film with high crystallinity and uniform composition was obtained by selenizing the low-temperature annealed spin-coated precursor film. Standard CZTSSe thin film solar cell based on the selenized CZTSSe thin film was fabricated and an efficiency of 6.4 % was achieved.

  6. Empirical relationships between gas abundances and UV selective extinction

    NASA Technical Reports Server (NTRS)

    Joseph, Charles L.

    1990-01-01

    Several studies of gas-phase abundances in lines of sight through the outer edges of dense clouds are summarized. These lines of sight have 0.4 less than E(B-V) less than 1.1 and have inferred spatial densities of a few hundred cm(-3). The primary thrust of these studies has been to compare gaseous abundances in interstellar clouds that have various types of peculiar selective extinction. To date, the most notable result has been an empirical relationship between the CN/Fe I abundance ratio and the depth of the 2200 A extinction bump. It is not clear at the present time, however, whether these two parameters are linearly correlated or the data are organized into two discrete ensembles. Based on 19 samples and assuming the clouds form discrete ensembles, lines of sight that have a CN/Fe I abundance ratio greater than 0.3 (dex) appear to have a shallow 2.57 plus or minus 0.55 bump compared to 3.60 plus or minus 0.36 for other dense clouds and compared to the 3.6 Seaton (1979) average. The difference in the strength of the extinction bump between these two ensembles is 1.03 plus or minus 0.23. Although a high-resolution IUE survey of dense clouds is far from complete, the few lines of sight with shallow extinction bumps all show preferential depletion of certain elements, while those lines of sight with normal 2200 A bumps do not. Ca II, Cr II, and Mn II appear to exhibit the strongest preferential depletion compared to S II, P II, and Mg II. Fe II and Si II depletions also appear to be enhanced somewhat in the shallow-bump lines of sight. It should be noted that Copernicus data suggest all elements, including the so-called nondepletors, deplete in diffuse clouds (Snow and Jenkins 1980, Joseph 1988). Those lines of sight through dense clouds that have normal 2200 A extinction bumps appear to be extensions of the depletions found in the diffuse interstellar medium. That is, the overall level of depletion is enhanced, but the element-to-element abundances are similar to

  7. Confirmation of Element Abundance Inhomogeneity in Interstellar Matter from a Study of the O-type Supergiants HDE 226868 (Cyg X-1) and α Cam

    NASA Astrophysics Data System (ADS)

    Karitskaya, E. A.; Bochkarev, N. G.; Shimansky, V. V.; Galazutdinov, G. A.

    2011-09-01

    Chemical abundances derived for two O-type supergiants with similar parameters confirm the inhomogeneity of heavy-element distribution on a scale of 2 kpc and a lifetime of ISM superclouds exceeding 1 Gyr.

  8. Effects of superabsorbent polymers on the abundances of antibiotic resistance genes, mobile genetic elements, and the bacterial community during swine manure composting.

    PubMed

    Guo, Aiyun; Gu, Jie; Wang, Xiaojuan; Zhang, Ranran; Yin, Yanan; Sun, Wei; Tuo, Xiaxia; Zhang, Li

    2017-11-01

    Superabsorbent polymers (SAPs) are considered suitable amendments for reducing the selection pressure due to heavy metals and the abundances of antibiotic resistance genes (ARGs) during composting. In this study, three SAP (sodium polyacrylate) levels (0, 5, and 15mgkg -1 of compost) were applied and their effects on the abundances of ARGs, mobile genetic elements (MGEs), and the bacterial community were investigated. After composting, the abundances of ARGs and MGEs decreased to different extent, where the removal efficiencies for tetW, dfrA7, ermX, aac(6')-ib-cr and MGEs exceeded 90%. The high SAP concentration significantly reduced the abundances of ARGs and MGEs, and changed the microbial community. Redundancy analysis indicated that the moisture content mainly explained the changes in ARGs and MGEs. Network analysis determined the potential hosts of ARGs and MGEs, and their co-occurrence. The results suggested that applying 15mgkg -1 SAP is appropriate for reducing ARGs in compost. Copyright © 2017. Published by Elsevier Ltd.

  9. Distinct patterns and processes of abundant and rare eukaryotic plankton communities following a reservoir cyanobacterial bloom.

    PubMed

    Xue, Yuanyuan; Chen, Huihuang; Yang, Jun R; Liu, Min; Huang, Bangqin; Yang, Jun

    2018-06-13

    Plankton communities normally consist of few abundant and many rare species, yet little is known about the ecological role of rare planktonic eukaryotes. Here we used a 18S ribosomal DNA sequencing approach to investigate the dynamics of rare planktonic eukaryotes, and to explore the co-occurrence patterns of abundant and rare eukaryotic plankton in a subtropical reservoir following a cyanobacterial bloom event. Our results showed that the bloom event significantly altered the eukaryotic plankton community composition and rare plankton diversity without affecting the diversity of abundant plankton. The similarities of both abundant and rare eukaryotic plankton subcommunities significantly declined with the increase in time-lag, but stronger temporal turnover was observed in rare taxa. Further, species turnover of both subcommunities explained a higher percentage of the community variation than species richness. Both deterministic and stochastic processes significantly influenced eukaryotic plankton community assembly, and the stochastic pattern (e.g., ecological drift) was particularly pronounced for rare taxa. Co-occurrence network analysis revealed that keystone taxa mainly belonged to rare species, which may play fundamental roles in network persistence. Importantly, covariations between rare and non-rare taxa were predominantly positive, implying multispecies cooperation might contribute to the stability and resilience of the microbial community. Overall, these findings expand current understanding of the ecological mechanisms and microbial interactions underlying plankton dynamics in changing aquatic ecosystems.

  10. Solar photospheric and coronal abundances from solar energetic particle measurements. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Breneman, H.

    1985-01-01

    Observations of solar energetic particles (SEP) from 22 solar flares in the 1977 to 1982 time period are reported. SEP abundances were obtained for all elements with 3 approximately less than Z approximately less than 30 except Li, Be, B, F, Sc, v, Co and Cu for which upper limits were obtained. Statistically meaningful abundances of several rare elements (P, Cl, K, Ti, and Mn) were determined for the first time, and the average abundance of the more abundant elements were determined with improved precision.

  11. Lab Astro and the Origins of the Chemical Elements

    NASA Astrophysics Data System (ADS)

    Lawler, James E.

    2010-03-01

    Interpretation of the spectra of metal-poor Galactic halo stars is dependent on AMO laboratory data [1,2]. Metal-poor Galactic halo stars were born when the Milky Way was young and they provide a record of the chemical evolution of the Galaxy. Elements heavier than iron are produced via r(apid)-process and s(low)-process n(eutron)-capture mechanisms. The s-process mechanism, which occurs in certain AGB stars, is relatively well understood. The explosive r-process is not well understood. The r-process n-capture mechanism was dominant early in the Galaxy's history [3]. New large aperture telescopes make it possible to record high-resolution spectra with high signal-to-noise ratios on a growing number of metal-poor stars. In addition to mapping the chemical evolution of the Galaxy, these studies are yielding an increasingly well-defined r-process elemental abundance pattern which constrains models of r-process nucleosynthesis [1]. The next phase of this ongoing research will address challenges in modeling stellar photospheres. Peculiar trends in abundances of specific Fe-group elements as a function of stellar age or metallicity may be due to limitations in traditional one dimensional (1d) local thermodynamic equilibrium (LTE) models of stellar photospheres or may be due to poorly understood nucleosynthesis [4]. Efforts are now underway to test the Saha or ionization equilibrium in a variety of stellar atmospheres for several Fe-group elements using the best available spectroscopic data for selected transitions. More comprehensive spectroscopic data of improved accuracy and accurate collisional data, especially for inelastic collisions of H atoms with metal atoms and ions, will be needed to fully develop 3d/non-LTE models of photospheres [e.g. 5]. [4pt] [1] C. Sneden, J. E. Lawler, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J. Suppl. Ser. 182, 80-96 (2009). [0pt] [2] J. E. Lawler, C. Sneden, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J

  12. AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hansen, T.; Christlieb, N.; Hansen, C. J.

    2015-07-10

    We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor ([Fe/H] < −2.0) stars, 12 of which are extremely metal-poor ([Fe/H] < −3.0), and 4 of which are ultra-metal-poor ([Fe/H] < −4.0). These stars were targeted to explore differences in the abundance ratios for elements that constrain the possible astrophysical sites of element production, including Li, C, N, O, the α-elements, the iron-peak elements, and a number of neutron-capture elements. This sample substantially increases the number of known carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars—our program stars include eight that are considered “normal” metal-poor stars, sixmore » CEMP-no stars, five CEMP-s stars, two CEMP-r stars, and two CEMP-r/s stars. One of the CEMP-r stars and one of the CEMP-r/s stars are possible NEMP stars. We detect lithium for three of the six CEMP-no stars, all of which are Li depleted with respect to the Spite plateau. The majority of the CEMP stars have [C/N] > 0. The stars with [C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit this signature are only found at [Fe/H] < −3.4, a metallicity below which we also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We confirm the existence of two plateaus in the absolute carbon abundances of CEMP stars, as suggested by Spite et al. We also present evidence for a “floor” in the absolute Ba abundances of CEMP-no stars at A(Ba) ∼ −2.0.« less

  13. Development of low-cost technology for the next generation of high efficiency solar cells composed of earth abundant elements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Agrawal, Rakesh

    2014-09-28

    The development of renewable, affordable, and environmentally conscious means of generating energy on a global scale represents a grand challenge of our time. Due to the “permanence” of radiation from the sun, solar energy promises to remain a viable and sustainable power source far into the future. Established single-junction photovoltaic technologies achieve high power conversion efficiencies (pce) near 20% but require complicated manufacturing processes that prohibit the marriage of large-scale throughput (e.g. on the GW scale), profitability, and quality control. Our approach to this problem begins with the synthesis of nanocrystals of semiconductor materials comprising earth abundant elements and characterizedmore » by material and optoelectronic properties ideal for photovoltaic applications, namely Cu2ZnSn(S,Se)4 (CZTSSe). Once synthesized, such nanocrystals are formulated into an ink, coated onto substrates, and processed into completed solar cells in such a way that enables scale-up to high throughput, roll-to-roll manufacturing processes. This project aimed to address the major limitation to CZTSSe solar cell pce’s – the low open-circuit voltage (Voc) reported throughout literature for devices comprised of this material. Throughout the project significant advancements have been made in fundamental understanding of the CZTSSe material and device limitations associated with this material system. Additionally, notable improvements have been made to our nanocrystal based processing technique to alleviate performance limitations due to the identified device limitations. Notably, (1) significant improvements have been made in reducing intra- and inter-nanoparticle heterogeneity, (2) improvements in device performance have been realized with novel cation substitution in Ge-alloyed CZTGeSSe absorbers, (3) systematic analysis of absorber sintering has been conducted to optimize the selenization process for large grain CZTSSe absorbers, (4) novel

  14. Probabilistic Classification Using Elemental Abundance Distributions and Lossless Image Compression in Apollo 17 Lunar Dust Samples from Mare Serenitatis

    NASA Technical Reports Server (NTRS)

    Storrie-Lombardi, Michael C.; Hoover, Richard B.; Abbas, Mian; Jerman, Gregory; Coston, James; Fisk, Martin

    2006-01-01

    We have previously outlined a strategy for the detection of fossils [Storrie-Lombardi and Hoover, 2004] and extant microbial life [Storrie-Lombaudi and Hoover, 20051 during robotic missions to Mars using co-registered structural and chemical signatures. Data inputs included image lossless compression indices to estimate relative textural complexity and elemental abundance distributions. Two exploratory classification algorithms (principal component analysis and hierarchical cluster analysis) provide an initial tentative classification of all targets. Nonlinear stochastic neural networks are then trained to produce a Bayesian estimate of algorithm classification accuracy. The strategy previously has been successful in distinguishing regions of biotic and abiotic alteration of basalt glass from unaltered samples. [Storrie-Lombardi and Fisk, 2004; Storrie-Lombardi and Fisk, 2004] Such investigations of abiotic versus biotic alteration of terrestrial mineralogy on Earth are compromised by .the difficulty finding mineralogy completely unaffected by the ubiquitous presence of microbial life on the planet. The renewed interest in lunar exploration offers an opportunity to investigate geological materials that may exhibit signs of aqueous alteration, but are highly unlikely to contain contaminating biological weathering signatures. We here present an extension of our earlier data set to include lunar dust samples obtained during the Apollo 17 mission. Apollo 17 landed in the Taurus-Littrow Valley in Mare Serenitatis. Most of the rock samples from this region of the lunar highlands are basalts comprised primarily of plagioclase and pyroxene and selected examples of orange and black volcanic glass. SEM images and elemental abundances (C6, N7, O8, Na11, Mg12, Al13, Si14, P15, S16, Cll7, K19, Ca20, Fe26) for a series of targets in the lunar dust samples are compared to the extant cyanobacteria, fossil trilobites, Orgueil meteorite, and terrestrial basalt targets previously

  15. Sulphur abundances in halo giants from the [S I] line at 1082 nm and the [S I] triplet around 1045 nm

    NASA Astrophysics Data System (ADS)

    Jönsson, H.; Ryde, N.; Nissen, P. E.; Collet, R.; Eriksson, K.; Asplund, M.; Gustafsson, B.

    2011-06-01

    Context. It is still debated whether or not the Galactic chemical evolution of sulphur in the halo follows the flat trend with [Fe/H] that is ascribed to the result of explosive nucleosynthesis in type II SNe. It has been suggested that the disagreement between different investigations of sulphur abundances in halo stars might be owing to problems with the diagnostics used, that a new production source of sulphur might be needed in the early Universe, like hypernovae, or that the deposition of supernova ejecta into the interstellar medium is time-delayed. Aims: The aim of this study is to try to clarify this situation by measuring the sulphur abundance in a sample of halo giants using two diagnostics: the S i triplet around 1045 nm and the [S i] line at 1082 nm. The latter of the two is not believed to be sensitive to non-LTE effects. We can thereby minimize the uncertainties in the diagnostic used and estimate the usefulness of the triplet for the sulphur determination in halo K giants. We will also be able to compare our sulphur abundance differences from the two diagnostics with the expected non-LTE effects in the 1045 nm triplet previously calculated by others. Methods: High-resolution near-infrared spectra of ten K giants were recorded using the spectrometer CRIRES mounted at VLT. Two standard settings were used, one covering the S i triplet and one covering the [S i] line. The sulphur abundances were individually determined with equivalent widths and synthetic spectra for the two diagnostics using tailored 1D model atmospheres and relying on non-LTE corrections from the litterature. Effects of convective inhomogeneities in the stellar atmospheres are investigated. Results: The sulphur abundances derived from both the [S i] line and the non-LTE corrected 1045 nm triplet favor a flat trend for the evolution of sulphur. In contrast to some previous studies, we saw no "high" values of [S/Fe] in our sample. Conclusions: We corroborate the flat trend in the [S

  16. Determination of Li abundance in Solar type stars of intermediate brightness

    NASA Astrophysics Data System (ADS)

    Amazo-Gómez, E. M.; Hernandez-Águila, B.; Dagostino, M. C.; Bertone, E.; de la Luz, V.

    2014-10-01

    The determination of the lithium abundance in stellar atmospheres is of fundamental importance in multiple contexts of contemporary astrophysics. On the one hand, the lithium present in stars with global sub-solar metal abundances provides a strong restriction on the abundance of this element as a result of primordial nucleo-synthesis. On the other hand, Li can be an age indicator for stars with convective envelopes. Additionally, Li abundance appears to be correlated with the presence of sub-stellar companions. We present preliminary results of a project aimed at determining the Li abundance in an extended sample of solar-like stars (spectral type G and luminosity class V) of intermediate brightness. High resolution spectroscopic data (R=65000) were obtained with the CanHiS echelle spectrograph on the 2.11m telescope of the Guillermo Haro Observatory in Cananea, Sonora, Mexico. We report the equivalent widths of a first sub-sample of 33 stars.

  17. APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Hasselquist, Sten; Shetrone, Matthew; Smith, Verne; Holtzman, Jon; McWilliam, Andrew; Fernández-Trincado, J. G.; Beers, Timothy C.; Majewski, Steven R.; Nidever, David L.; Tang, Baitian; Tissera, Patricia B.; Fernández Alvar, Emma; Allende Prieto, Carlos; Almeida, Andres; Anguiano, Borja; Battaglia, Giuseppina; Carigi, Leticia; Delgado Inglada, Gloria; Frinchaboy, Peter; García-Hernández, D. A.; Geisler, Doug; Minniti, Dante; Placco, Vinicius M.; Schultheis, Mathias; Sobeck, Jennifer; Villanova, Sandro

    2017-08-01

    The Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze thechemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances, and it is the first time that C, N, P, K, V, Cr, Co, and Ni have been studied at high resolution in this galaxy. We find that the Sgr stars with [Fe/H] ≳ -0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that the Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light initial mass function, one lacking the most massive stars that would normally pollute the interstellar medium with the hydrostatic elements. We use a simple chemical-evolution model, flexCE, to further support our claim and conclude that recent stellar generations of Fornax and the Large Magellanic Cloud could also have formed according to a top-light initial mass function.

  18. Improved Cr II log(gf)s and Cr Abundances in the Photospheres of the Sun and Metal-Poor Star HD 84937

    NASA Astrophysics Data System (ADS)

    Lawler, James E.; Sneden, Chris; Nave, Gillian; Den Hartog, Elizabeth; Emrahoglu, Nuri; Cowan, John J.

    2017-01-01

    New laser induced fluorescence (LIF) data for eight levels of singly ionized chromium (Cr) and emission branching fraction (BF) measurements for 183 lines of the second spectrum of chromium (Cr II) are reported. A goal of this study is to reconcile Solar and stellar Cr abundance values based on Cr I and Cr II lines. Analyses of eighteen spectra from three Fourier Transform Spectrometers supplemented with ultraviolet spectra from a high resolution echelle spectrometer yield the BF measurements. Radiative lifetimes from LIF measurements are used to convert the BFs to absolute transition probabilities. These new laboratory data are applied to determine the Cr abundance log eps in the Sun and metal-poor star HD 84937. The mean result in the Sun is = 5.624 ± 0.009 compared to = 5.644 ± 0.006 on a scale with the H abundance log eps(H) = 12. Similarily the photosphere of HD 84937 is found to be in Saha balance with = 3.417 ± 0.006 and 0 eV) > = 3.374 ± 0.011 for this dwarf star. The resonance (E.P. = 0 eV) lines of Cr I reveal overionization of the ground level of neutral Cr. We find a correlation of Cr with the iron-peak element Ti, suggesting an associated or related nucleosynthetic production. Four iron-peak elements (Cr along with Ti, V and Sc) appear to have a similar (or correlated) production history - other iron-peak elements appear not to be associated with Cr.This work is supported in part by NASA grant NNX16AE96G (J.E.L.), by NSF grant AST-1516182 (J.E.L. & E.D.H.), by NASA interagency agreement NNH10AN381 (G.N.), and NSF grant AST-1211585 (C.S.). Postdoctoral research support for N. E. is from the Technological and Scientific Research Council of Turkey (TUBITAK).

  19. Rb-Sr systematics and REE abundances in Shalka and several other diogenites

    NASA Astrophysics Data System (ADS)

    Takahashi, K.; Yabuki, S.; Kagi, H.; Masuda, A.

    1994-07-01

    The diogenites have been regarded as igneous products in the early solar system and they have been considered to have genetically close relationship with eucrites. Depsite their simple mineralogical compositions and narrow range for major-element compositions, diogenites have been known to show wide Rare Earth Elements (REE) variations in absolute concentration and in mutual abundance ratios. Furthermore, some diogenites have peculiar Rb-Sr isotope systematics (ages younger than 4.5 b.y.). The Shalka meteorite belongs to the diogenites, and a unique REE abundance pattern has been reported. We performed Rb-Sr isotopic analyses and measured REE abundances in the Shalka diogenite with several other diogenites to discuss their genesis. Roughly speaking, REE patterns in diogenites are characterized by the negative Eu anomaly and the depletion of light REE. For Shalka, some heterogeneity in REE abundance patterns have been observed. While one sample chip shows the REE pattern with a large negative Eu anomaly and depleted light REE, particularly characterized by the concave curvature for the La-Nd span, other samples show the pattern nearly flat or the pattern enriched in light REE. These variations could not be explained easily by the simple mixing process of LREE-depleted components and LREE-enriched melt, but they imply some metamorphism process. The Rb-Sr isotopic data for Shalka are shown with the data for other several diogenites. These observations indicate that Shalka would undergo a significant extent of metamorphism followed by redistribution of REE and the disturbance of the Rb-Sr systematics. We are going to do further studies on Shalka to discuss the metamorphic process and compare it with other diogenites.

  20. Elemental abundance analyses with DAO spectrograms: XXX. The middle B through early A stars ξ2 Ceti (B9 III), 21 Aquilae (B8 II-III), ι Aquilae (B5 III), and ι Delphini (A2V)

    NASA Astrophysics Data System (ADS)

    Adelman, S. J.; Westbrook, P. C.; Gulliver, A. F.

    2010-04-01

    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. ξ2 Cet on average has a solar composition with a few abundances outside the solar range while both 21 Aql and ι Aql have abundances marginally less than solar. The abundances of ι Del are greater than solar with a few elements such as Ca being less than solar. It is an Am star. Table 3 is only available in electronic form at the CDS via http://cdsarc.u-strasbg.fr/ftp/cats/J/other/AN/331/378

  1. Coronal abundances and their variation

    NASA Technical Reports Server (NTRS)

    Saba, Julia L. R.

    1994-01-01

    This contract supports the investigation of elemental abundances in the solar corona, principally through analysis of high-resolution software X-ray spectra from the Flat Crystal Spectrometer on NASA's Solar Maximum Mission. The goals of the study are a characterization of the mean values of relative abundances of elements accessible in the FCS data, and information on the extent and circumstances of their variability. This report is a summation of the data analysis and reporting activities which occurred since the last report, submitted two months early, in April 1994, to facilitate evaluation of the first year's progress for contract renewal. Hence this report covers the period 15 April 1994 - 15 December 1994. A list of publications resulting from this research is included.

  2. Exo-geneology: Stellar Abundances in Solar-like Stars with Planets

    NASA Astrophysics Data System (ADS)

    Teske, Johanna; SDSS-IV APOGEE-2

    2018-01-01

    Through the process of star and planet formation, we think that the chemical abundances, or ``genes’’, of host stars are passed on to their orbiting planets. One prominent example of this is the giant planet-metallicity (iron abundance) correlation, but could other stellar ``genes’’ help explain the growing menagerie of exoplanets? Particularly interesting is the relative importance of C, O, Mg, and Si – for instance, are giant planet cores dominated by ice-forming or rock-forming elements? The ratios of these elements in terrestrial planets also control their interior structure and mineralogy, and can thus affect their similarity (or not) to Earth. In this talk I will discuss how high resolution spectroscopic studies of host stars have been and are being used to investigate how/to what extent planet properties are dependent on host star properties, focusing on solar-like (FGK) stars. I will also highlight the role that upcoming facilities can play in understanding the diversity of planets in the Galaxy.

  3. p-capture reaction cycles in rotating massive stars and their impact on elemental abundances in globular cluster stars: A case study of O, Na and Al

    NASA Astrophysics Data System (ADS)

    Mahanta, Upakul; Goswami, Aruna; Duorah, Hiralal; Duorah, Kalpana

    2017-08-01

    Elemental abundance patterns of globular cluster stars can provide important clues for understanding cluster formation and early chemical evolution. The origin of the abundance patterns, however, still remains poorly understood. We have studied the impact of p-capture reaction cycles on the abundances of oxygen, sodium and aluminium considering nuclear reaction cycles of carbon-nitrogen-oxygen-fluorine, neon-sodium and magnesium-aluminium in massive stars in stellar conditions of temperature range 2×107 to 10×107 K and typical density of 102 gm cc-1. We have estimated abundances of oxygen, sodium and aluminium with respect to Fe, which are then assumed to be ejected from those stars because of rotation reaching a critical limit. These ejected abundances of elements are then compared with their counterparts that have been observed in some metal-poor evolved stars, mainly giants and red giants, of globular clusters M3, M4, M13 and NGC 6752. We observe an excellent agreement with [O/Fe] between the estimated and observed abundance values for globular clusters M3 and M4 with a correlation coefficient above 0.9 and a strong linear correlation for the remaining two clusters with a correlation coefficient above 0.7. The estimated [Na/Fe] is found to have a correlation coefficient above 0.7, thus implying a strong correlation for all four globular clusters. As far as [Al/Fe] is concerned, it also shows a strong correlation between the estimated abundance and the observed abundance for globular clusters M13 and NGC 6752, since here also the correlation coefficient is above 0.7 whereas for globular cluster M4 there is a moderate correlation found with a correlation coefficient above 0.6. Possible sources of these discrepancies are discussed.

  4. Experimental and theoretical oscillator strengths of Mg I for accurate abundance analysis

    NASA Astrophysics Data System (ADS)

    Pehlivan Rhodin, A.; Hartman, H.; Nilsson, H.; Jönsson, P.

    2017-02-01

    Context. With the aid of stellar abundance analysis, it is possible to study the galactic formation and evolution. Magnesium is an important element to trace the α-element evolution in our Galaxy. For chemical abundance analysis, such as magnesium abundance, accurate and complete atomic data are essential. Inaccurate atomic data lead to uncertain abundances and prevent discrimination between different evolution models. Aims: We study the spectrum of neutral magnesium from laboratory measurements and theoretical calculations. Our aim is to improve the oscillator strengths (f-values) of Mg I lines and to create a complete set of accurate atomic data, particularly for the near-IR region. Methods: We derived oscillator strengths by combining the experimental branching fractions with radiative lifetimes reported in the literature and computed in this work. A hollow cathode discharge lamp was used to produce free atoms in the plasma and a Fourier transform spectrometer recorded the intensity-calibrated high-resolution spectra. In addition, we performed theoretical calculations using the multiconfiguration Hartree-Fock program ATSP2K. Results: This project provides a set of experimental and theoretical oscillator strengths. We derived 34 experimental oscillator strengths. Except from the Mg I optical triplet lines (3p 3P°0,1,2-4s 3S1), these oscillator strengths are measured for the first time. The theoretical oscillator strengths are in very good agreement with the experimental data and complement the missing transitions of the experimental data up to n = 7 from even and odd parity terms. We present an evaluated set of oscillator strengths, gf, with uncertainties as small as 5%. The new values of the Mg I optical triplet line (3p 3P°0,1,2-4s 3S1) oscillator strength values are 0.08 dex larger than the previous measurements.

  5. Isotopic compositions of the elements, 2001

    USGS Publications Warehouse

    Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

    2005-01-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E)">Ar(E)Ar(E) and its uncertainty U[Ar(E)]">U[Ar(E)]U[Ar(E)] recommended by CAWIA in 2001.

  6. VizieR Online Data Catalog: Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+, 2016)

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Beers, T. C.; Placco, V. M.; Rasmussen, K. C.; Carollo, D.; He, S.; Hansen, T. T.; Roederer, I. U.; Zeanah, J.

    2017-03-01

    We have endeavored to compile a list that is as complete as possible of carbon-enhanced metal-poor (CEMP); CEMP-s (and CEMP-r/s) and CEMP-no stars having [Fe/H]<-1.0 and [C/Fe]>=+0.7 with available high-resolution spectroscopic abundance information. We have only considered stars with claimed detections or lower limits for carbon, along with several critical elemental-abundance ratios, such as [Ba/Fe] and [Eu/Fe]. The great majority of our sample comes from the literature compilation of Placco+ (2014, J/ApJ/797/21). See section 2 for further details. (2 data files).

  7. Data-processing strategies for nano-tomography with elemental specification

    NASA Astrophysics Data System (ADS)

    Liu, Yijin; Cats, Korneel H.; Nelson Weker, Johanna; Andrews, Joy C.; Weckhuysen, Bert M.; Pianetta, Piero

    2013-10-01

    Combining the energy tunability provided by synchrotron X-ray sources with transmission X-ray microscopy, the morphology of materials can be resolved in 3D at spatial resolution down to 30 nm with elemental/chemical specification. In order to study the energy dependence of the absorption coefficient over the investigated volume, the tomographic reconstruction and image registration (before and/or after the tomographic reconstruction) are critical. We show in this paper the comparison of two different data processing strategies and conclude that the signal to noise ratio (S/N) in the final result can be improved via performing tomographic reconstruction prior to the evaluation of energy dependence. Our result echoes the dose fractionation theorem, and is particularly helpful when the element of interest has low concentration.

  8. The Origin and Distribution of Heavy Elements in HCG 62

    NASA Technical Reports Server (NTRS)

    Vrtilek, Jan; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    We present recent data on the compact group HCG 62 taken with AXAF CCD Imaging Spectrometer-S (ACIS-S) on Chandra. The sparseness of groups and their relatively simple dynamical history allow the properties of the Intergalatic Medium (IGM) to be more directly related to galaxy evolution than may be possible in clusters, and their lower gas temperatures produce strong lines from a broader range of elements than is the case in hotter clusters. This observation exploits the high X-ray brightness of HCG 62 to determine accurately the abundances of heavy elements as a function of position in the group, to test whether abundance variations are associated with individual galaxies, and to trace the origin of the enrichment.

  9. Geochemistry of trace elements in coals from the Zhuji Mine, Huainan Coalfield, Anhui, China

    USGS Publications Warehouse

    Sun, R.; Liu, Gaisheng; Zheng, Lingyun; Chou, C.-L.

    2010-01-01

    The abundances of nine major elements and thirty-eight trace elements in 520 samples of low sulfur coals from the Zhuji Mine, Huainan Coalfield, Anhui, China, were determined. Samples were mainly collected from 10 minable coal seams of 29 boreholes during exploration. The B content in coals shows that the influence of brackish water decreased toward the top of coal seams; marine transgression and regression occurred frequently in the Lower Shihezi Formation. A wide range of elemental abundances is found. Weighted means of Na, K, Fe, P, Be, B, Co, Ni, Cr, Se, Sb, Ba, and Bi abundances in Zhuji coals are higher, and the remainder elements are either lower or equal to the average values of elements in coals of northern China. Compared to the Chinese coals, the Zhuji coals are higher in Na, K, Be, B, Cr, Co, Se, Sn, Sb, and Bi, but lower in Ti, P, Li, V and Zn. The Zhuji coals are lower only in S, P, V and Zn than average U.S. and world coals. Potassium, Mg, Ca, Mn, Sr, As, Se, Sb and light rare earth elements (LREE) had a tendency to be enriched in thicker coal seams, whereas Fe, Ti, P, V, Co, Ni, Y, Mo, Pb and heavy rare earth elements (HREE) were inclined to concentrate in thinner coal seams. The enrichment of some elements in the Shanxi or Upper Shihezi Formations is related to their depositional environments. The elements are classified into three groups based on their stratigraphic distributions from coal seams 3 to 11-2, and the characteristics of each group are discussed. Lateral distributions of selected elements are also investigated. The correlation coefficients of elemental abundances with ash content show that the elements may be classified into four groups related to modes of occurrence of these elements. ?? 2009 Elsevier B.V. All rights reserved.

  10. Trace Elements in River Waters

    NASA Astrophysics Data System (ADS)

    Gaillardet, J.; Viers, J.; Dupré, B.

    2003-12-01

    Trace elements are characterized by concentrations lower than 1 mg L-1 in natural waters. This means that trace elements are not considered when "total dissolved solids" are calculated in rivers, lakes, or groundwaters, because their combined mass is not significant compared to the sum of Na+, K+, Ca2+, Mg2+, H4SiO4, HCO3-, CO32-, SO42-, Cl-, and NO3-. Therefore, most of the elements, except about ten of them, occur at trace levels in natural waters. Being trace elements in natural waters does not necessarily qualify them as trace elements in rocks. For example, aluminum, iron, and titanium are major elements in rocks, but they occur as trace elements in waters, due to their low mobility at the Earth's surface. Conversely, trace elements in rocks such as chlorine and carbon are major elements in waters.The geochemistry of trace elements in river waters, like that of groundwater and seawater, is receiving increasing attention. This growing interest is clearly triggered by the technical advances made in the determination of concentrations at lower levels in water. In particular, the development of inductively coupled plasma mass spectrometry (ICP-MS) has considerably improved our knowledge of trace-element levels in waters since the early 1990s. ICP-MS provides the capability of determining trace elements having isotopes of interest for geochemical dating or tracing, even where their dissolved concentrations are extremely low.The determination of trace elements in natural waters is motivated by a number of issues. Although rare, trace elements in natural systems can play a major role in hydrosystems. This is particularly evident for toxic elements such as aluminum, whose concentrations are related to the abundance of fish in rivers. Many trace elements have been exploited from natural accumulation sites and used over thousands of years by human activities. Trace elements are therefore highly sensitive indexes of human impact from local to global scale. Pollution

  11. Geochemical maps showing the distribution and abundance of selected elements in stream-sediment samples, Solomon and Bendeleben 1 degree by 3 degree quadrangles, Seward Peninsula, Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, S.C.; King, H.D.; O'Leary, R.M.

    Geochemical maps showing the distribution and abundance of selected elements in stream-sediment samples, Solomon and Bendeleben 1{degree} by 3{degree} quadrangles, Seward Peninsula, Alaska is presented.

  12. Bulk and rare earth abundances in the Luna 16 soil levels A and D.

    NASA Technical Reports Server (NTRS)

    Gillum, D. E.; Ehmann, W. D.; Wakita, H.; Schmitt, R. A.

    1972-01-01

    Determination of the abundances of major, minor, and trace elements by means of sequential INAA (instrumental neutron activation analysis) in two Luna 16 soils, at levels A (about 7 cm depth) and D (about 30 cm depth). Abundances of the bulk elements in Luna 16 soils generally agree with the values reported by Vinogradov (1971). Elemental abundances of both bulk and trace elements are nearly the same for the two A and D soil levels. Overall, the chemical compositions of the two Luna 16 soils are more closely related to Apollo 11 soil 10084 than to Apollo 12 and 14 soils, with the exception of TiO2 abundances.-

  13. Optimization of low cost, non toxic, earth abundant p-type Cu2SnS3 thin film for Photovoltaic application

    NASA Astrophysics Data System (ADS)

    Chaudhari, J. J.; Patel, S.; Joshi, U. S.

    2016-09-01

    Cu2SnS3 (CTS) is one of promising candidate as an absorber material for thin film solar cell. Because of relatively higher prize of Indium and hazardous environmental impact of processing of Gallium, CTS is suitable alternative candidate to Cu2SnS3 (CIGS) based solar cell as its constituent elements such as copper, tin and sulphur are abundantly available in earth's crust. CTS is ternary semiconductor and its energy band gap is 1.5eV, which is perfectly matched with solar energy spectrum for maximum transfer of solar energy into electrical energy through photovoltaic action. The primary methods for the synthesis of CTS are Thermal evaporation, electrochemical, sputtering and wet chemical methods. Here in this paper we have optimized a low cost non-vacuum solution process method for the synthesis of CTS without any external sulfurization. The X-ray diffraction studies showed the formation of phase with the peaks corresponding to (112), (220) and (312) planes. Chemical Solution Deposition (CSD) for the synthesis of CTS is suitable for large area deposition and it includes several routes like solvothermal methods, direct liquid coating and nano ink based technique. The metal Chloride salts and thiourea is used as a source of sulphur to synthesize CTS solution and homogeneous thin films of CTS deposited on glass substrate using spin coating method. Use of abrasive solvent like hydrazine and hydrogen sulphide gas which are used to synthesize CTS thin film have detrimental effect on environment, we report eco friendly solvent based approach to synthesize CTS at low temperature 200 °C.

  14. Absolute Single Photoionization Cross Sections of Se^3+ For the Determination of Elemental Abundances in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Esteves, David; Sterling, Nicholas; Aguilar, Alex; Kilcoyne, A. L. David; Phaneuf, Ronald; Bilodeau, Rene; Red, Eddie; McLaughlin, Brendan; Norrington, Patrick; Balance, Connor

    2009-05-01

    Numerical simulations show that derived elemental abundances in astrophysical nebulae can be uncertain by factors of two or more due to atomic data uncertainties alone, and of these uncertainties, absolute photoionization cross sections are the most important. Absolute single photoionization cross sections for Se^3+ ions have been measured from 42 eV to 56 eV at the ALS using the merged beams photo-ion technique. Theoretical photoionization cross section calculations were also performed for these ions using the state-of-the-art fully relativistic Dirac R-matrix code (DARC). The calculations show encouraging agreement with the experimental measurements.

  15. A low initial abundance of 247Cm in the early solar system and implications for r-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Stirling, Claudine H.; Halliday, Alex N.; Potter, Emma-Kate; Andersen, Morten B.; Zanda, Brigitte

    2006-11-01

    the solar system. As such it is difficult to reconcile with a model of actinide production in the same r-process forming event as 182Hf with a half-life of 8.9 My [G.J. Wasserburg, M. Busso, R. Gallino, Abundances of actinides and short-lived nonactinides in the interstellar medium: Diverse supernova sources for the r-processes, Astrophys. J. 466 (1996) L109-L113]. The alternative models of 182Hf production via a neutron-rich fast s-process, occurring, for example, in the helium burning shell in a 25 solar mass star during explosive nucleosynthesis [G.J. Wasserburg, M. Busso, R. Gallino, Abundances of actinides and short-lived nonactinides in the interstellar medium: Diverse supernova sources for the r-processes, Astrophys. J. 466 (1996) L109-L113], or via a distinct r-process event that is separate from actinide production [G.J. Wasserburg, M. Busso, R. Gallino, K.M. Nollet, Short-lived nuclei in the early solar system: Possible AGB sources, Nucl. Phys. A (in press)], may provide a viable explanation. However, further studies are also required to assess the veracity of Cm-U systematics, which are critically dependent on the suitability of using Nd and the light rare earth elements (LREEs) as a chemical proxy for Cm.

  16. Detailed Abundances in a Metal-Poor Stellar Stream

    NASA Astrophysics Data System (ADS)

    Roederer, I. U.; Sneden, C.; Thompson, I. B.; Preston, G. W.; Shectman, S. A.

    2010-10-01

    We present the results of a detailed abundance analysis of one of the confirmed building blocks of the Milky Way stellar halo, a kinematically-coherent metal-poor stellar stream. We have obtained high resolution and high S/N spectra of 8 confirmed and 4 rejected stream members using the MIKE spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory and the 2dCoude spectrograph on the Smith Telescope at McDonald Observatory. We have derived abundances or upper limits for nearly 50 species of more than 40 elements in each of these stars. The stream members show a range of metallicity (-2.5 < [Fe/H] < -1.5) but are otherwise chemically homogeneous, with the same star-to-star chemical dispersion in [X/Fe] as halo stars. They show no evolution in the α or Fe-group elements over the range of metallicity. The stream does not resemble a globular cluster in that its members show a range of metallicities, and the small chemical dispersion and lack of chemical evolution demonstrate that it is also unlike the classical Milky Way dwarf spheroidal galaxies. Our results support the notion that a significant fraction of the Milky Way stellar halo was formed from accreted systems, and these systems likely did not resemble the present-day globular clusters or luminous dwarf galaxies. This stream is mildly enriched (in, e.g., [Eu/Fe]) by material produced by the main and weak components of the rapid neutron-capture process and shows no evidence for enrichment by the slow neutron-capture process. Except for the observed metallicity range of the stream stars, the enrichment pattern of the stream is nearly identical to that of the massive metal-poor globular cluster M15. The kinematics of M15 and the stream are also similar. It is possible that both systems may have originated from a common progenitor but not likely that the stream originated from M15.

  17. Heterogeneity and loss of soil nutrient elements under aeolian processes in the Otindag Desert, China

    NASA Astrophysics Data System (ADS)

    Li, Danfeng; Wang, Xunming; Lou, Junpeng; Liu, Wenbin; Li, Hui; Ma, Wenyong; Jiao, Linlin

    2018-02-01

    The heterogeneity of the composition of surface soils that are affected by aeolian processes plays important roles in ecological evolution and the occurrence of aeolian desertification in fragile ecological zones, but the associated mechanisms are poorly understood. Using field investigation, wind tunnel experiments, and particle size and element analyses, we discuss the variation in the nutrient elements of surface soils that forms in the presence of aeolian processes of four vegetation species (Caragana microphylla Lam, Artemisia frigida Willd. Sp. Pl., Leymus chinensis (Trin.) Tzvel. and Stipa grandis P. Smirn) growing in the Otindag Desert, China. These four vegetation communities correspond to increasing degrees of degradation. A total of 40 macro elements, trace elements, and oxides were measured in the surface soil and in wind-transported samples. The results showed that under the different degradation stages, the compositions and concentrations of nutrients in surface soils differed for the four vegetation species. Aeolian processes may cause higher heterogeneity and higher loss of soil nutrient elements for the communities of Artemisia frigida Willd. Sp. Pl., Leymus chinensis (Trin.) Tzvel, and Stipa grandis P. Smirn than for the Caragana microphylla Lam community. There was remarkable variation in the loss of nutrients under different aeolian transportation processes. Over the past several decades, the highest loss of soil elements occurred in the 1970s, whereas the loss from 2011 to the present was generally 4.0% of that in the 1970s. These results indicate that the evident decrease in nutrient loss has played an important role in the rehabilitation that has occurred in the region recently.

  18. APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hasselquist, Sten; Holtzman, Jon; Shetrone, Matthew

    The Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze thechemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances, and it is the first time that C, N, P, K, V, Cr, Co, and Ni have been studied at high resolution in this galaxy. We find that the Sgr stars withmore » [Fe/H] ≳ −0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that the Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light initial mass function, one lacking the most massive stars that would normally pollute the interstellar medium with the hydrostatic elements. We use a simple chemical-evolution model, flexCE, to further support our claim and conclude that recent stellar generations of Fornax and the Large Magellanic Cloud could also have formed according to a top-light initial mass function.« less

  19. Abundance estimation and conservation biology

    USGS Publications Warehouse

    Nichols, J.D.; MacKenzie, D.I.

    2004-01-01

    Abundance is the state variable of interest in most population–level ecological research and in most programs involving management and conservation of animal populations. Abundance is the single parameter of interest in capture–recapture models for closed populations (e.g., Darroch, 1958; Otis et al., 1978; Chao, 2001). The initial capture–recapture models developed for partially (Darroch, 1959) and completely (Jolly, 1965; Seber, 1965) open populations represented efforts to relax the restrictive assumption of population closure for the purpose of estimating abundance. Subsequent emphases in capture–recapture work were on survival rate estimation in the 1970’s and 1980’s (e.g., Burnham et al., 1987; Lebreton et al.,1992), and on movement estimation in the 1990’s (Brownie et al., 1993; Schwarz et al., 1993). However, from the mid–1990’s until the present time, capture–recapture investigators have expressed a renewed interest in abundance and related parameters (Pradel, 1996; Schwarz & Arnason, 1996; Schwarz, 2001). The focus of this session was abundance, and presentations covered topics ranging from estimation of abundance and rate of change in abundance, to inferences about the demographic processes underlying changes in abundance, to occupancy as a surrogate of abundance. The plenary paper by Link & Barker (2004) is provocative and very interesting, and it contains a number of important messages and suggestions. Link & Barker (2004) emphasize that the increasing complexity of capture–recapture models has resulted in large numbers of parameters and that a challenge to ecologists is to extract ecological signals from this complexity. They offer hierarchical models as a natural approach to inference in which traditional parameters are viewed as realizations of stochastic processes. These processes are governed by hyperparameters, and the inferential approach focuses on these hyperparameters. Link & Barker (2004) also suggest that our attention

  20. Precision Measurements of Solar Energetic Particle Elemental Composition

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Data from the Cosmic Ray Subsystem (CRS) aboard the Voyager 1 and 2 spaceraft were used to determined, solar energetic particle abundances or upper limits for all elements with Z 30 from a combined set of 10 solar flares during the 1977 to 1982 time period. Statistically meaningful abundances were determined for several rare elements including P, C1, K, Ti and Mn, while the precision of the mean abundances for the more abundant elements was proved. When compared to solar photospheric spectroscopic abundances, these new SEP abundances more clearly exhibit the step-function dependence on first ionization potential previously reported.

  1. APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy System

    NASA Astrophysics Data System (ADS)

    Hasselquist, Sten; Shetrone, Matthew D.; Smith, Verne V.; Holtzman, Jon A.; McWilliam, Andrew; APOGEE Team

    2018-06-01

    The Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze the chemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances, and it is the first time that C, N, P, K, V, Cr, Co, and Ni have been studied at high resolution in this galaxy. We find that the Sgr stars with [Fe/H] > -0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that the Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light initial mass function, one lacking the most massive stars that would normally pollute the interstellar medium with the hydrostatic elements. We use a simple chemical-evolution model, flexCE, to further support our claim and conclude that recent stellar generations of Fornax and the Large Magellanic Cloud could also have formed according to a top-light initial mass function. We then exploit the unique chemical abundance patters of the Sgr core to trace stars belonging to the Sgr tidal streams elsewhere in the Milky Way.

  2. The R-process Alliance: First Release from the Southern Search for R-process-enhanced Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Hansen, Terese T.; Holmbeck, Erika M.; Beers, Timothy C.; Placco, Vinicius M.; Roederer, Ian U.; Frebel, Anna; Sakari, Charli M.; Simon, Joshua D.; Thompson, Ian B.

    2018-05-01

    The recent detection of a binary neutron star merger and the clear evidence of the decay of radioactive material observed in this event have, after 60 years of effort, provided an astrophysical site for the rapid neutron-capture (r-) process which is responsible for the production of the heaviest elements in our universe. However, observations of metal-poor stars with highly enhanced r-process elements have revealed abundance patterns suggesting that multiple sites may be involved. To address this issue, and to advance our understanding of the r-process, we have initiated an extensive search for bright (V < 13.5), very metal-poor ([Fe/H] < ‑2) stars in the Milky Way halo exhibiting strongly enhanced r-process signatures. This paper presents the first sample collected in the southern hemisphere using the echelle spectrograph on du Pont 2.5 m telescope at Las Campanas Observatory. We have observed and analyzed 107 stars with ‑3.13 < [Fe/H] < ‑0.79. Of those, 12 stars are strongly enhanced in heavy r-process elements (r-II), 42 stars show moderate enhancements of heavy r-process material (r-I), and 20 stars exhibit low abundances of the heavy r-process elements and higher abundances of the light r-process elements relative to the heavy ones (limited-r). This search is more successful at finding r-process-enhanced stars compared to previous searches, primarily due to a refined target selection procedure that focuses on red giants. This paper includes data gathered with the 2.5 m du Pont telescope located at Las Campanas Observatory, Chile.

  3. Process to separate transuranic elements from nuclear waste

    DOEpatents

    Johnson, T.R.; Ackerman, J.P.; Tomczuk, Z.; Fischer, D.F.

    1988-07-12

    A process for removing transuranic elements from a waste chloride electrolytic salt containing transuranic elements in addition to rare earth and other fission product elements so the salt waste may be disposed of more easily and the valuable transuranic elements may be recovered for reuse. The salt is contacted with a cadmium-uranium alloy which selectively extracts the transuranic elements from the salt. The waste salt is generated during the reprocessing of nuclear fuel associated with the Integral Fast Reactor (IFR). 2 figs.

  4. Process to separate transuranic elements from nuclear waste

    DOEpatents

    Johnson, Terry R.; Ackerman, John P.; Tomczuk, Zygmunt; Fischer, Donald F.

    1989-01-01

    A process for removing transuranic elements from a waste chloride electrolytic salt containing transuranic elements in addition to rare earth and other fission product elements so the salt waste may be disposed of more easily and the valuable transuranic elements may be recovered for reuse. The salt is contacted with a cadmium-uranium alloy which selectively extracts the transuranic elements from the salt. The waste salt is generated during the reprocessing of nuclear fuel associated with the Integral Fast Reactor (IFR).

  5. Rolling Process Modeling Report: Finite-Element Prediction of Roll Separating Force and Rolling Defects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soulami, Ayoub; Lavender, Curt A.; Paxton, Dean M.

    2014-04-23

    Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum (U-10Mo) alloy plate-type fuel for the U.S. high-performance research reactors. This work supports the Convert Program of the U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) Global Threat Reduction Initiative. This report documents modeling results of PNNL’s efforts to perform finite-element simulations to predict roll separating forces and rolling defects. Simulations were performed using a finite-element model developed using the commercial code LS-Dyna. Simulations of the hot rolling of U-10Mo coupons encapsulated in low-carbon steel have been conducted following two different schedules. Model predictions ofmore » the roll-separation force and roll-pack thicknesses at different stages of the rolling process were compared with experimental measurements. This report discusses various attributes of the rolled coupons revealed by the model (e.g., dog-boning and thickness non-uniformity).« less

  6. nirS-Encoding denitrifier community composition, distribution, and abundance along the coastal wetlands of China.

    PubMed

    Gao, Juan; Hou, Lijun; Zheng, Yanling; Liu, Min; Yin, Guoyu; Li, Xiaofei; Lin, Xianbiao; Yu, Chendi; Wang, Rong; Jiang, Xiaofen; Sun, Xiuru

    2016-10-01

    For the past few decades, human activities have intensively increased the reactive nitrogen enrichment in China's coastal wetlands. Although denitrification is a critical pathway of nitrogen removal, the understanding of denitrifier community dynamics driving denitrification remains limited in the coastal wetlands. In this study, the diversity, abundance, and community composition of nirS-encoding denitrifiers were analyzed to reveal their variations in China's coastal wetlands. Diverse nirS sequences were obtained and more than 98 % of them shared considerable phylogenetic similarity with sequences obtained from aquatic systems (marine/estuarine/coastal sediments and hypoxia sea water). Clone library analysis revealed that the distribution and composition of nirS-harboring denitrifiers had a significant latitudinal differentiation, but without a seasonal shift. Canonical correspondence analysis showed that the community structure of nirS-encoding denitrifiers was significantly related to temperature and ammonium concentration. The nirS gene abundance ranged from 4.3 × 10(5) to 3.7 × 10(7) copies g(-1) dry sediment, with a significant spatial heterogeneity. Among all detected environmental factors, temperature was a key factor affecting not only the nirS gene abundance but also the community structure of nirS-type denitrifiers. Overall, this study significantly enhances our understanding of the structure and dynamics of denitrifying communities in the coastal wetlands of China.

  7. [Effect of short-time drought process on denitrifying bacteria abundance and N2O emission in paddy soil].

    PubMed

    Lu, Jing; Liu, Jin-Bo; Sheng, Rong; Liu, Yi; Chen, An-Lei; Wei, Wen-Xue

    2014-10-01

    In order to investigate the impact of drying process on greenhouse gas emissions and denitrifying microorganisms in paddy soil, wetting-drying process was simulated in laboratory conditions. N2O flux, redox potential (Eh) were monitored and narG- and nosZ-containing denitrifiers abundances were determined by real-time PCR. N2O emission was significantly increased only 4 h after drying process began, and it was more than 6 times of continuous flooding (CF) at 24 h. In addition, narG and nosZ gene abundances were increased rapidly with the drying process, and N2O emission flux was significantly correlated with narG gene abundance (P < 0.01). Our results indicated that the narG-containing deniteifiers were the main driving microorganisms which caused the N2O emission in the short-time drought process in paddy soil.

  8. Process to separate transuranic elements from nuclear waste

    DOEpatents

    Johnson, T.R.; Ackerman, J.P.; Tomczuk, Z.; Fischer, D.F.

    1989-03-21

    A process is described for removing transuranic elements from a waste chloride electrolytic salt containing transuranic elements in addition to rare earth and other fission product elements so the salt waste may be disposed of more easily and the valuable transuranic elements may be recovered for reuse. The salt is contacted with a cadmium-uranium alloy which selectively extracts the transuranic elements from the salt. The waste salt is generated during the reprocessing of nuclear fuel associated with the Integral Fast Reactor (IFR). 2 figs.

  9. Highly siderophile elements were stripped from Earth’s mantle by iron sulfide segregation

    NASA Astrophysics Data System (ADS)

    Rubie, David C.; Laurenz, Vera; Jacobson, Seth A.; Morbidelli, Alessandro; Palme, Herbert; Vogel, Antje K.; Frost, Daniel J.

    2016-09-01

    Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth’s core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the “Hadean matte”) stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios.

  10. High-resolution abundance analysis of the metallic-line star HR 7250

    NASA Astrophysics Data System (ADS)

    Elmaslı, Aslı; Ünal, Kübraözge; Çalışkan, Şeyma

    2018-07-01

    We estimated the stellar parameters and chemical abundances of the highly neglected A-type star HR 7250. The star's high resolution spectrum, spanning a wavelength range from 3900 to 7900 Å, was obtained at the TÜBİTAK National Observatory. We derived the abundances of 14 elements (O, Na, Mg, Si, S, Ca, Sc, Ti, Cr, Fe, Ni, Sr, Y, and Ba) for HR 7250 from the unblended lines of the star's spectrum. Our analysis shows that HR 7250 is a chemically peculiar Am star. We also estimated its age and mass as 400 ± 70 Myr and 3.25 ± 0.17 M⊙ from evolutionary tracks and isochrones.

  11. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A.

    2012-03-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 ± 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  12. Metal abundances in hot white dwarfs with signatures of a superionized wind

    NASA Astrophysics Data System (ADS)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2018-01-01

    About a dozen hot white dwarfs with effective temperatures Teff = 65 000-120 000 K exhibit unusual absorption features in their optical spectra. These objects were tentatively identified as Rydberg lines of ultra-high excited metals in ionization stages v-x, indicating line formation in a dense environment with temperatures near 106 K. Since some features show blueward extensions, it was argued that they stem from a superionized wind. A unique assignment of the lines to particular elements is not possible, although they probably stem from C, N, O, and Ne. To further investigate this phenomenon, we analyzed the ultraviolet spectra available from only three stars of this group; that is, two helium-rich white dwarfs, HE 0504-2408 and HS 0713+3958 with spectral type DO, and a hydrogen-rich white dwarf, HS 2115+1148 with spectral type DAO. We identified light metals (C, N, O, Si, P, and S) with generally subsolar abundances and heavy elements from the iron group (Cr, Mn, Fe, Co, Ni) with solar or oversolar abundance. The abundance patterns are not unusual for hot WDs and can be interpreted as the result of gravitational settling and radiative levitation of elements. As to the origin of the ultra-high ionized metals lines, we discuss the possible presence of a multicomponent radiatively driven wind that is frictionally heated.

  13. Hyperfine Structure and Abundances of Heavy Elements in 68 Tauri (HD 27962)

    NASA Astrophysics Data System (ADS)

    Martinet, S.; Monier, R.

    2017-12-01

    HD 27962, also known as 68 Tauri, is a Chemically Peculiar Am star member of the Hyades Open Cluster in the local arm of the Galaxy. We have modeled the high resolution SOPHIE (R=75000) spectrum of 68 Tauri using updated model atmosphere and spectrum synthesis to derive chemical abundances in its atmosphere. In particular, we have studied the effect of the inclusion of Hyperfine Structure of various Baryum isotopes on the determination of the Baryum abundance in 68 Tauri. We have also derived new abundances using updated accurate atomic parameters retrieved from the NIST database.

  14. Elemental abundance differences between nuclei acclerated in CIR shocks and solar flares

    NASA Technical Reports Server (NTRS)

    Dietrich, W. F.; Simpson, J. A.

    1985-01-01

    Measurement of the ratios of nuclear abundances H/He, CNO/Fe-group and the Fe-group/HE for 51 passages of Corotating Interaction Regions (CIRs) at 1 AU, and measurement of these ratios from 620 solar flares in the energy range 0.6 to 4 MeV per nucleon, show that CIR shock acceleration alone does not change significantly these ratios from the values they have for solar system abundances or the solar wind. The solar flare ratios continue to reflect strong biases in the abundances, consistent with requirements for multistage acceleration rpocesses at the Sun.

  15. Automated spectroscopic abundances of A and F-type stars using echelle spectrographs. II. Abundances of 140 A-F stars from ELODIE

    NASA Astrophysics Data System (ADS)

    Erspamer, D.; North, P.

    2003-02-01

    Using the method presented in Erspamer & North (\\cite{erspamer}, hereafter Paper I), detailed abundances of 140 stars are presented. The uncertainties characteristic of this method are presented and discussed. In particular, we show that for a S/N ratio higher than 200, the method is applicable to stars with a rotational velocity as high as 200 km s-1. There is no correlation between abundances and Vsin i, except a spurious one for Sr, Sc and Na which we explain by the small number of lines of these elements combined with a locally biased continuum. Metallic giants (Hauck \\cite{hauck}) show larger abundances than normal giants for at least 8 elements: Al, Ca, Ti, Cr, Mn, Fe, Ni and Ba. The anticorrelation for Na, Mg, Si, Ca, Fe and Ni with Vsin i suggested by Varenne & Monier (\\cite{varenne99}) is not confirmed. The predictions of the Montréal models (e.g. Richard et al. \\cite{richard01}) are not fulfilled in general. However, a correlation between left [(Fe)/(H)right ] and log g is found for stars of 1.8 to 2.0 M_sun. Various possible causes are discussed, but the physical reality of this correlation seems inescapable. Based on observations collected at the 1.93 m telescope at the Observatoire de Haute-Provence (St-Michel l'Observatoire, France) and CORALIE. Based on observations collected at the Swiss 1.2 m Leonard Euler telescopes at the European Southern Observatory (La Silla, Chile). Tables 5 and 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u.strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/1121

  16. The TGAS HR diagram of S-type stars

    NASA Astrophysics Data System (ADS)

    Shetye, Shreeya; van Eck, Sophie; Jorissen, Alain; van Winckel, Hans; Siess, Lionel

    2018-04-01

    S-type stars are late-type giants enhanced with s-process elements originating either from nucleosynthesis during the Asymptotic Giant Branch (AGB) or from a pollution by a binary companion. The former are called intrinsic S stars, and the latter extrinsic S stars. The atmospheric parameters of S stars are more numerous than those of M-type giants (C/O ratio and s-process abundances affect the thermal structure and spectral synthesis), and hence they are more difficult to derive. Nevertheless, high-resolution spectroscopic data of S stars combined with the TGAS (Tycho-Gaia Astrometric solution) parallaxes were used to derive effective temperatures, surface gravities, and luminosities. These parameters allow to locate the intrinsic and extrinsic S stars in the Hertzsprung-Russell diagram.

  17. Determinations of rare earth element abundance and U-Pb age of zircons using multispot laser ablation-inductively coupled plasma mass spectrometry.

    PubMed

    Yokoyama, Takaomi D; Suzuki, Toshihiro; Kon, Yoshiaki; Hirata, Takafumi

    2011-12-01

    We have developed a new calibration technique for multielement determination and U-Pb dating of zircon samples using laser ablation-inductively coupled plasma mass spectrometry (ICPMS) coupled with galvanometric optics. With the galvanometric optics, laser ablation of two or more sample materials could be achieved in very short time intervals (~10 ms). The resulting sample aerosols released from different ablation pits or different solid samples were mixed and homogenized within the sample cell and then transported into the ICP ion source. Multiple spot laser ablation enables spiking of analytes or internal standard elements directly into the solid samples, and therefore the standard addition calibration method can be applied for the determination of trace elements in solid samples. In this study, we have measured the rare earth element (REE) abundances of two zircon samples (Nancy 91500 and Prešovice) based on the standard addition technique, using a direct spiking of analytes through a multispot laser ablation of the glass standard material (NIST SRM612). The resulting REE abundance data show good agreement with previously reported values within analytical uncertainties achieved in this study (10% for most elements). Our experiments demonstrated that nonspectroscopic interferences on 14 REEs could be significantly reduced by the standard addition technique employed here. Another advantage of galvanometric devices is the accumulation of sample aerosol released from multiple spots. In this study we have measured the U-Pb age of a zircon sample (LMR) using an accumulation of sample aerosols released from 10 separate ablation pits of low diameters (~8 μm). The resulting (238)U-(206)Pb age data for the LMR zircons was 369 ± 64 Ma, which is in good agreement with previously reported age data (367.6 ± 1.5 Ma). (1) The data obtained here clearly demonstrate that the multiple spot laser ablation-ICPMS technique can become a powerful approach for elemental and isotopic

  18. Transition Region Abundance Measurements During Impulsive Heating Events

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Brooks, David H.; Doschek, George A.; Feldman, Uri

    2016-06-01

    It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O IV, v, and VI emission lines are enhanced relative to emission lines from Mg v, VI, and vii and Si VI and vii, and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher-frequency heating leading to long-lived structures and the accumulation of low-FIP elements in the corona.

  19. NEW NEUTRON-CAPTURE MEASUREMENTS IN 23 OPEN CLUSTERS. I. THE r -PROCESS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Overbeek, Jamie C.; Friel, Eileen D.; Jacobson, Heather R., E-mail: joverbee@indiana.edu

    2016-06-20

    Neutron-capture elements, those with Z > 35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r -process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s -process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with clustermore » age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3–10) lines for each element. We find that the pure r -process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r - and s -process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ∼0.04 dex kpc{sup −1}. The mixed elements also appear to have nonlinear relationships with R {sub GC}.« less

  20. A novel abundant family of retroposed elements (DAS-SINEs) in the nine-banded armadillo (Dasypus novemcinctus).

    PubMed

    Churakov, Gennady; Smit, Arian F A; Brosius, Jürgen; Schmitz, Jürgen

    2005-04-01

    About half of the mammalian genome is composed of retroposons. Long interspersed elements (LINEs) and short interspersed elements (SINEs) are the most abundant repetitive elements and account for about 21% and 13% of the human genome, respectively. SINEs have been detected in all major mammalian lineages, except for the South American order Xenarthra, also termed Edentata (armadillos, anteaters, and sloths). Investigating this order, we discovered a novel high-copy-number family of tRNA derived SINEs in the nine-banded armadillo Dasypus novemcinctus, a species that successfully crossed the Central American land bridge to North America in the Pliocene. A specific computer algorithm was developed, and we detected and extracted 687 specific SINEs from databases. Termed DAS-SINEs, we further divided them into six distinct subfamilies. We extracted tRNA(Ala)-derived monomers, two types of dimers, and three subfamilies of chimeric fusion products of a tRNA(Ala) domain and an approximately 180-nt sequence of thus far unidentified origin. Comparisons of secondary structures of the DAS-SINEs' tRNA domains suggest selective pressure to maintain a tRNA-like D-arm structure in the respective founder RNAs, as shown by compensatory mutations. By analysis of subfamily-specific genetic variability, comparison of the proportion of direct repeats, and analysis of self-integrations as well as key events of dimerization and deletions or insertions, we were able to delineate the evolutionary history of the DAS-SINE subfamilies.

  1. PROCESS OF DISSOLVING FUEL ELEMENTS OF NUCLEAR REACTORS

    DOEpatents

    Wall, E.M.V.; Bauer, D.T.; Hahn, H.T.

    1963-09-01

    A process is described for dissolving stainless-steelor zirconium-clad uranium dioxide fuel elements by immersing the elements in molten lead chloride, adding copper, cuprous chloride, or cupric chloride as a catalyst and passing chlorine through the salt mixture. (AEC)

  2. Modelling element distributions in the atmospheres of magnetic Ap stars

    NASA Astrophysics Data System (ADS)

    Alecian, G.; Stift, M. J.

    2007-11-01

    Context: In recent papers convincing evidence has been presented for chemical stratification in Ap star atmospheres, and surface abundance maps have been shown to correlate with the magnetic field direction. Radiatively driven diffusion, which is known to be sensitive to the magnetic field strength and direction, is among the processes responsible for these inhomogeneities. Aims: Here we explore the hypothesis that equilibrium stratifications - such that the diffusive particle flux is close to zero throughout the atmosphere - can, in a number of cases, explain the observed abundance maps and vertical distributions of the various elements. Methods: An iterative scheme adjusts the abundances in such a way as to achieve either zero particle flux or zero effective acceleration throughout the atmosphere, taking strength and direction of the magnetic field into account. Results: The investigation of equilibrium stratifications in stellar atmospheres with temperatures from 8500 to 12 000 K and fields up to 10 kG reveals considerable variations in the vertical distribution of the 5 elements studied (Mg, Si, Ca, Ti, Fe), often with zones of large over- or under-abundances and with indications of other competing processes (such as mass loss). Horizontal magnetic fields can be very efficient in helping the accumulation of elements in higher layers. Conclusions: A comparison between our calculations and the vertical abundance profiles and surface maps derived by magnetic Doppler imaging reveals that equilibrium stratifications are in a number of cases consistent with the main trends inferred from observed spectra. However, it is not clear whether such equilibrium solutions will ever be reached during the evolution of an Ap star.

  3. HAT-P-26b: A Neptune-mass Exoplanet with Primordial Solar Heavy Element Abundance

    NASA Astrophysics Data System (ADS)

    Wakeford, Hannah; Sing, David; Deming, Drake; Kataria, Tiffany; Lopez, Eric

    2016-10-01

    A trend in giant planet mass and atmospheric heavy elemental abundance was first noted last century from observations of planets in our own solar system. These four data points from Jupiter, Saturn, Uranus, and Neptune have served as a corner stone of planet formation theory. Here we add another point in the mass-metallicity trend from a detailed observational study of the extrasolar planet HAT-P-26b, which inhabits the critical mass regime near Neptune and Uranus. Neptune-sized worlds are among the most common planets in our galaxy and frequently exist in orbital periods very different from that of our own solar system ice giants. Atmospheric studies are the principal window into these worlds, and thereby into their formation and evolution, beyond those of our own solar system. Using the Hubble Space Telescope and Spitzer, from the optical to the infrared, we conducted a detailed atmospheric study of the Neptune-mass exoplanet HAT-P-26b over 0.5 to 4.5 μm. We detect prominent H2O absorption at 1.4 μm to 525 ppm in the atmospheric transmission spectrum. We determine that HAT-P-26b's atmosphere is not rich in heavy elements (≈1.8×solar), which goes distinctly against the solar system mass-metallicity trend. This likely indicates that HAT-P-26b's atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime with little contamination from metal-rich planetesimals.

  4. Precision measurements of solar energetic particle elemental composition

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Using data from the Cosmic Ray Subsystem (CRS) aboard the Voyager 1 and 2 spacecraft, solar energetic particle abundances or upper limits for all elements with 3 = Z = 30 from a combined set of 10 solar flares during the 1977 to 1982 time period were determined. Statistically meaningful abundances have been determined for the first time for several rare elements including P, Cl, K, Ti and Mn, while the precision of the mean abundances for the more abundant elements has been improved by typically a factor of approximately 3 over previously reported values.

  5. Isotopic Abundances as Tracers of the Processes of Lunar Formation

    NASA Astrophysics Data System (ADS)

    Pahlevan, K.

    2011-12-01

    Ever since Apollo, isotopic abundances have been used as tracers to study lunar formation, in particular, to study the sources of the lunar material. In the last decade, however, a number of isotopic similarities have been observed between the lunar samples and the Earth's mantle such that these two reservoirs are now known to be indistinguishable from one another to high precision for a variety of isotopic tracers. This occurs against the backdrop of a Solar System that exhibits widespread heterogeneity with respect to these tracers, a situation that strongly argues that the source of the lunar material is the silicate Earth. To reconcile this observation with the fact that the Moon is thought to result from the collision of two isotopically distinct planetary bodies, a scenario has emerged in which the material from the Moon-forming impactor and the proto-Earth are homogenized in the aftermath of the giant impact. This takes place via turbulent mixing in the time after the giant impact but before lunar accretion while the Earth-Moon system exists in the form of a continuous, high-temperature fluid. Importantly, this high-temperature phase of the evolution occurs in the presence of at least two phases (liquid + vapor) making possible chemical and isotopic fractionation. While equilibrium isotopic fractionation tends to zero at high temperatures, and the post giant impact environment experiences some of the highest temperatures encountered in the Earth sciences, there are several factors that nevertheless make equilibrium isotope effects important probes of this early evolution. (1) Because the vaporization of silicates involves decomposition reactions, the bonding environment for elements in the liquid is often very different from that in the vapor. This difference makes the magnitude of isotopic fractionation intrinsically large, even at the relevant temperatures. (2) Since the isotopic composition of a silicate liquid and co-existing vapor are distinctly

  6. A Differential Chemical Abundance Scale for the Globular Cluster M5

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; McWilliam, Andrew

    2010-06-01

    We present LTE chemical abundances for five red giants and one AGB star in the Galactic globular cluster (GC) M5 based on high-resolution spectroscopy using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan 6.5 m Clay telescope. Our results are based on a line-by-line differential abundance analysis relative to the well-studied red giant Arcturus. The stars in our sample that overlap with existing studies in the literature are consistent with published values for [Fe/H] and agree to within typically 0.04 dex for the α-elements. Most deviations can be assigned to varying analysis techniques in the literature. This strengthens our newly established differential GC abundance scale and advocates future use of this method. In particular, we confirm a mean [Fe I/H] of -1.33 ± 0.03 (stat.) ±0.03 (sys.) dex and also reproduce M5's enhancement in the α-elements (O, Mg, Si, Ca, Ti) at +0.4 dex, rendering M5 a typical representative of the Galactic halo. Over-ionization of Fe I in the atmospheres of these stars by non-LTE effects is found to be less than 0.07 dex. Five of our six stars show O-Na-Al-Mg abundance patterns consistent with pollution by proton-capture nucleosynthesis products. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  7. Short interspersed element (SINE) depletion and long interspersed element (LINE) abundance are not features universally required for imprinting.

    PubMed

    Cowley, Michael; de Burca, Anna; McCole, Ruth B; Chahal, Mandeep; Saadat, Ghazal; Oakey, Rebecca J; Schulz, Reiner

    2011-04-20

    Genomic imprinting is a form of gene dosage regulation in which a gene is expressed from only one of the alleles, in a manner dependent on the parent of origin. The mechanisms governing imprinted gene expression have been investigated in detail and have greatly contributed to our understanding of genome regulation in general. Both DNA sequence features, such as CpG islands, and epigenetic features, such as DNA methylation and non-coding RNAs, play important roles in achieving imprinted expression. However, the relative importance of these factors varies depending on the locus in question. Defining the minimal features that are absolutely required for imprinting would help us to understand how imprinting has evolved mechanistically. Imprinted retrogenes are a subset of imprinted loci that are relatively simple in their genomic organisation, being distinct from large imprinting clusters, and have the potential to be used as tools to address this question. Here, we compare the repeat element content of imprinted retrogene loci with non-imprinted controls that have a similar locus organisation. We observe no significant differences that are conserved between mouse and human, suggesting that the paucity of SINEs and relative abundance of LINEs at imprinted loci reported by others is not a sequence feature universally required for imprinting.

  8. Ecological evaluation of the abundance and effects of elk herbivory in Rocky Mountain National Park, Colorado, 1994-1999

    USGS Publications Warehouse

    Singer, Francis J.; Zeigenfuss, Linda C.

    2002-01-01

    Several National Park Service units in the Intermountain region possess a number of closely related management needs relative to the abundance of wild ungulates and their herbivory effects on plants and ecosystem processes. In 1993, the then National Biological Service (NBS) - now U.S. Geological Survey, Biological Resources Discipline (USGS, BRD)­ initiated a series of research studies in four park units in the Intermountain West., into the abundance and effects of ungulates on park ecosystems. Each of these parks received a number of similar research study elements including: (a) a number of new ungulate grazing exclosures (n = 12-21 exclosures per park); (b) aerial survey sightability models to estimate population sizes of ungulates; (e) measures of biomass production and consumption rates near the exclosures and across the landscape; (d) studies of the effects of the grazing on plant abundance, species diversity, and ecosystem effects; and (e) computer model simulations (SAVANNA) of the effects on the ecosystem and plant resources of different ungulate management scenarios. One park unit, Rocky Mountain National Park, Colorado, received funding from the U.S. Geological Survey (USGS, BRD) and parallel funding from NPS for an intensive research study of the effects of elk on the park ecosystems.

  9. Abundance analysis of roAp stars. IV. HD24712

    NASA Astrophysics Data System (ADS)

    Ryabchikova, T. A.; Landstreet, J. D.; Gelbmann, M. J.; Bolgova, G. T.; Tsymbal, V. V.; Weiss, W. W.

    1997-11-01

    We present the first abundance analysis of the rapidly oscillating chemically peculiar star HD24712, and determine a T_eff,=7250K, log {g},=4.3, and xi_t ,=1kms(-1) . Microturbulence seems to be entirely simulated by a magnetic field with a polar field strength of 4.4kG and of dipolar structure, both of which are supported by our polarimetric observations. Rotation of HD24712 and a spotty surface distribution of the elements result in different mean abundances for different (magnetic) phases. Our results do not support the hypothesis of a monotonic correlation between the amplitude of abundance variations and the atomic number Z, and we present arguments in favour of one of the rotation periods (Prot=12\\fd 4610) discussed in the literature. Rare earth elements are the most overabundant elements relative to the sun, and they have the largest abundance amplitude during a rotation cycle; only Mg has a larger amplitude. For HD24712 we find a clear overabundance of Co while most of the other iron peak elements are underabundant. A comparison of the abundance pattern with the other three roAp stars analyzed so far by us concludes the paper. A systematic difference between surface gravities obtained from spectroscopy and from both asteroseismology and evolutionary tracks is found for the roAp stars HD 24712, alpha Cir, and gamma Equ. Based on observations obtained with the Canada-France-Hawaii telescope, operated by the National Research Council of Canada, the Centre Centre National de la Recherche Scientifique de France, and the University of Hawaii, and on observations obtained at CARSO, Las Campanas, Chile

  10. Manufacturing processes for fabricating graphite/PMR 15 polyimide structural elements

    NASA Technical Reports Server (NTRS)

    Sheppard, C. H.; Hoggatt, J. T.; Symonds, W. A.

    1979-01-01

    Investigations were conducted to obtain commercially available graphite/PMR-15 polyimide prepreg, develop an autoclave manufacturing process, and demonstrate the process by manufacturing structural elements. Controls were established on polymer, prepreg, composite fabrication, and quality assurance, Successful material quality control and processes were demonstrated by fabricating major structural elements including flat laminates, hat sections, I beam sections, honeycomb sandwich structures, and molded graphite reinforced fittings. Successful fabrication of structural elements and simulated section of the space shuttle aft body flap shows that the graphite/PMR-15 polyimide system and the developed processes are ready for further evaluation in flight test hardware.

  11. SXT/R391 integrative and conjugative elements in Proteus species reveal abundant genetic diversity and multidrug resistance

    PubMed Central

    Li, Xinyue; Du, Yu; Du, Pengcheng; Dai, Hang; Fang, Yujie; Li, Zhenpeng; Lv, Na; Zhu, Baoli; Kan, Biao; Wang, Duochun

    2016-01-01

    SXT/R391 integrative and conjugative elements (ICEs) are self-transmissible mobile genetic elements that are found in most members of Enterobacteriaceae. Here, we determined fifteen SXT/R391 ICEs carried by Proteus isolates from food (4.2%) and diarrhoea patients (17.3%). BLASTn searches against GenBank showed that the fifteen SXT/R391 ICEs were closely related to that from different Enterobacteriaceae species, including Proteus mirabilis. Using core gene phylogenetic analysis, the fifteen SXT/R391 ICEs were grouped into six distinct clusters, including a dominant cluster and three clusters that have not been previously reported in Proteus isolates. The SXT/R391 ICEs shared a common structure with a set of conserved genes, five hotspots and two variable regions, which contained more foreign genes, including drug-resistance genes. Notably, a class A β-lactamase gene was identified in nine SXT/R391 ICEs. Collectively, the ICE-carrying isolates carried resistance genes for 20 tested drugs. Six isolates were resistant to chloramphenicol, kanamycin, streptomycin, trimethoprim-sulfamethoxazole, sulfisoxazole and tetracycline, which are drug resistances commonly encoded by ICEs. Our results demonstrate abundant genetic diversity and multidrug resistance of the SXT/R391 ICEs carried by Proteus isolates, which may have significance for public health. It is therefore necessary to continuously monitor the antimicrobial resistance and related mobile elements among Proteus isolates. PMID:27892525

  12. Interstellar Dust Models Consistent with Extinction, Emission, and Abundance Constraints

    NASA Technical Reports Server (NTRS)

    Zubko, Viktor; Dwek, Eli; Arendt, Richard G.

    2004-01-01

    We present new interstellar dust models which have been derived by simultaneously fitting the far ultraviolet to near infrared extinction, the diffuse infrared emission, and, unlike previous models, the elemental abundances in dust for the diffuse interstellar medium. We found that dust models consisting of a mixture of spherical graphite and silicate grains, polycyclic aromatic hydrocarbon (PAH) molecules, in addition to porous composite particles containing silicate, organic refractory, and water ice, provide an improved .t to the UV-to-infrared extinction and infrared emission measurements, while consuming the amounts of elements well within the uncertainties of adopted interstellar abundances, including B star abundances. These models are a signi.cant improvement over the recent Li & Draine (2001, ApJ, 554, 778) model which requires an excessive amount of silicon to be locked up in dust: 48 ppm (atoms per million of H atoms), considerably more than the solar abundance of 34 ppm or the B star abundance of 19 ppm.

  13. The r-, s-, and p-Processes in Nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Meyer, Bradley S.

    1994-01-01

    A goal of this paper is to review the recent progress astrophysicists, astronomers, and physicists have made in the r-, s-, and p-processes in nucleosynthesis and to point out the problems that remain in our understanding of the formation of the heavy nuclei. Another, perhaps deeper, goal is to to seek some understanding of why there are three major processes available to nature for synthesis of heavy elements.

  14. Element Abundances in the Galactic Cosmic Rays with Atomic Number (Z) in the Interval 30 is less than or equal to Z is less than or equal to 40

    NASA Technical Reports Server (NTRS)

    Barbier, Louis; Binns, W. R.; Christian, E.; deNolfo, G.; Geier, S.; Israel, M. H.; Link, J. T.; Mewaldt, R. A.; Mitchell, J.; Rauch, B. F.

    2004-01-01

    We present new results on the elemental abundances of galactic cosmic rays with atomic number, Z, greater than 30, and comparison of these observations with abundances expected from galactic propagation of various suggested models of the cosmic-ray source. We combine preliminary results from the 2003-04 flight of the Trans-Iron Galactic Element Recorder (TIGER) cosmic-ray detector with previously reported results from the 2001-02 flight. This instrument flew over Antarctica for nearly 32 days at a mean atmospheric depth of 5.2 mb in December 2001 - January 2002. At the time of submission of this abstract, January 8, 2004, TIGER was again in the air over Antarctica having completed 22 days of an expected 30day flight at a mean atmospheric depth of about 4 nb, Data from the first flight demonstrated excellent resolution of individual elements, and we expect similar resolution from the second flight.

  15. Abundances in the Uranium-rich Star CS 31082-001

    NASA Astrophysics Data System (ADS)

    Qian, Y.-Z.; Wasserburg, G. J.

    2001-05-01

    The recent discovery by Cayrel et al. of U in CS 31082-001 along with Os and Ir at greatly enhanced abundances but with [Fe/H]=-2.9 strongly reinforces the argument that there are at least two kinds of Type II supernova (SN II) sources for r-nuclei. One source is the high-frequency H events responsible for heavy r-nuclei (A>135) but not Fe. The H-yields calculated from data on other ultra-metal-poor stars and the Sun provide a template for quantitatively predicting the abundances of all other r-elements. In CS 31082-001 these should show a significant deficiency at A<135 relative to the solar r-pattern. It is proposed that CS 31082-001 should have had a companion that exploded as an SN II H event. If the binary survived the explosion, this star should now have a compact companion, most likely a stellar-mass black hole. Comparison of abundance data with predicted values and a search for a compact companion should provide a stringent test of the proposed r-process model. The U-Th age determined by Cayrel et al. for CS 31082-001 is, to within substantial uncertainties, in accord with the r-process age determined from solar system data. The time gap between the big bang and the onset of normal star formation allows r-process chronometers to provide only a lower limit on the age of the universe.

  16. Detection of the Second r-process Peak Element Tellurium in Metal-poor Stars

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Lawler, James E.; Cowan, John J.; Beers, Timothy C.; Frebel, Anna; Ivans, Inese I.; Schatz, Hendrik; Sobeck, Jennifer S.; Sneden, Christopher

    2012-03-01

    Using near-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, we detect neutral tellurium in three metal-poor stars enriched by products of r-process nucleosynthesis, BD +17 3248, HD 108317, and HD 128279. Tellurium (Te, Z = 52) is found at the second r-process peak (A ≈ 130) associated with the N = 82 neutron shell closure, and it has not been detected previously in Galactic halo stars. The derived tellurium abundances match the scaled solar system r-process distribution within the uncertainties, confirming the predicted second peak r-process residuals. These results suggest that tellurium is predominantly produced in the main component of the r-process, along with the rare earth elements. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-8342 and GO-12268. Some of the data presented in this Letter were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These data are associated with programs GO-7348, GO-7402, GO-8197, and GO-9455.

  17. Volatile Element Geochemistry in the Lower Atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Schaefer, L.; Fegley, B., Jr.

    2004-01-01

    We computed equilibrium abundances of volatile element compounds as a function of altitude in Venus lower atmosphere. The elements included are generally found in volcanic gases and sublimates on Earth and may be emitted in volcanic gases on Venus or volatilized from its hot surface. We predict: 1) PbS, Bi2S3, or possibly a Pb-Bi sulfosalt are the radar bright heavy metal frost in the Venusian highlands; 2) It should be possible to determine Venus' age by Pb-Pb dating of PbS condensed in the Venusian highlands, which should be a representative sample of Venusian lead; 3) The gases HBr, PbCl2, PbBr2, As4O6, As4S4, Sb4O6, BiSe, InBr, InCl, Hg, TlCl, TlBr, SeS, Se2-7, HI, I, I2, ZnCl2, and S2O have abundances greater than 0.1 ppbv in our nominal model and may be spectroscopically observable; 4) Cu, Ag, Au, Zn, Cd, Ge, and Sn are approx. 100 % condensed at the 740 K (0 km) level on Venus.

  18. Abundance patterns of evolved stars with Hipparcos parallaxes and ages based on the APOGEE data base

    NASA Astrophysics Data System (ADS)

    Jia, Y. P.; Chen, Y. Q.; Zhao, G.; Bari, M. A.; Zhao, J. K.; Tan, K. F.

    2018-01-01

    We investigate the abundance patterns for four groups of stars at evolutionary phases from sub-giant to red clump (RC) and trace the chemical evolution of the disc by taking 21 individual elemental abundances from APOGEE and ages from evolutionary models with the aid of Hipparcos distances. We find that the abundances of six elements (Si, S, K, Ca, Mn and Ni) are similar from the sub-giant phase to the RC phase. In particular, we find that a group of stars with low [C/N] ratios, mainly from the second sequence of RC stars, show that there is a difference in the transfer efficiency of the C-N-O cycle between the main and the secondary RC sequences. We also compare the abundance patterns of C-N, Mg-Al and Na-O with giant stars in globular clusters from APOGEE and find that field stars follow similar patterns as M107, a metal-rich globular cluster with [M/H] ∼- 1.0, which shows that the self-enrichment mechanism represented by strong C-N, Mg-Al and Na-O anti-correlations may not be important as the metallicity reaches [M/H] > -1.0 dex. Based on the abundances of above-mentioned six elements and [Fe/H], we investigate age versus abundance relations and find some old super-metal-rich stars in our sample. Their properties of old age and being rich in metal are evidence for stellar migration. The age versus metallicity relations in low-[α/M] bins show unexpectedly positive slopes. We propose that the fresh metal-poor gas infalling on to the Galactic disc may be the precursor for this unexpected finding.

  19. The influence of doping element on structural and luminescent characteristics of ZnS thin films

    NASA Astrophysics Data System (ADS)

    Kryshtab, T.; Khomchenko, V. S.; Andraca-Adame, J. A.; Rodionov, V. E.; Khachatryan, V. B.; Tzyrkunov, Yu. A.

    2006-10-01

    For the fabrication of green and blue emitting ZnS structures the elements of I, III, and VII groups (Cu, Al, Ga, Cl) are used as dopants. The influence of type of impurity, doping technique, and type of substrate on crystalline structure and surface morphology together with luminescent properties was investigated. The doping of thin films was realized during the growth process and/or post-deposition thermal treatment. ZnS thin films were deposited by physical (EBE) and chemical (MOCVD) methods onto glass or ceramic (BaTiO 3) substrates. Closed spaced evaporation and thermodiffusion methods were used for the post-deposition doping of ZnS films. X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and measurements of photoluminescent (PL) spectra were used for the investigations. It was shown that the doping by the elements of I (Cu) and III (Al, Ga) groups does not change the crystal structure during the thermal treatment up to 1000 ∘C, whereas simultaneous use of the elements of I (Cu) and VII (Cl) groups leads to decrease of the phase transition temperature to 800 ∘C. The presence of impurities in the growth process leads to a grain size increase. At post-deposition treatment Ga and Cl act as activators of recrystallization process. The transition of ZnS sphalerite lattice to wurtzite one leads to the displacement of the blue emission band position towards the short-wavelength range by 10 nm.

  20. Transposable element-associated microRNA hairpins produce 21-nt sRNAs integrated into typical microRNA pathways in rice

    PubMed Central

    Ou-Yang, Fangqian; Luo, Qing-Jun; Zhang, Yue; Richardson, Casey R.; Jiang, Yingwen; Rock, Christopher D.

    2013-01-01

    microRNAs (miRNAs) are a class of small RNAs (sRNAs) of ~21 nucleotides (nt) in length processed from foldback hairpins by DICER-LIKE1 (DCL1) or DCL4. They regulate the expression of target mRNAs by base pairing through RNA-Induced Silencing Complex (RISC). In the RISC, ARGONAUTE1 (AGO1) is the key protein that cleaves miRNA targets at position ten of a miRNA:target duplex. The authenticity of many annotated rice miRNA hairpins is under debate because of their homology to repeat sequences. Some of them, like miR1884b, have been removed from the current release of miRBase based on incomplete information. In this study, we investigated the association of transposable element (TE)-derived miRNAs with typical miRNA pathways (DCL1/4- and AGO1-dependent) using publicly available deep sequencing datasets. Seven miRNA hairpins with 13 unique sRNAs were specifically enriched in AGO1 immunoprecipitation samples and relatively reduced in DCL1/4 knockdown genotypes. Interestingly, these species are ~21-nt long, instead of 24-nt as annotated in miRBase and the literature. Their expression profiles meet current criteria for functional annotation of miRNAs. In addition, diagnostic cleavage tags were found in degradome datasets for predicted target mRNAs. Most of these miRNA hairpins share significant homology with miniature inverted-repeat transposable elements (MITEs), one type of abundant DNA transposons in rice. Finally, the root-specific production of a 24 nt miRNA-like sRNA was confirmed by RNA blot for a novel EST that maps to the 3'-UTR of a candidate pseudogene showing extensive sequence homology to miR1884b hairpin. Our data are consistent with the hypothesis that TEs can serve as a driving force for the evolution of some MIRNAs, where co-opting of DICER-LIKE1/4 processing and integration into AGO1 could exapt transcribed TE-associated hairpins into typical miRNA pathways. PMID:23420033

  1. Rapid Determination of Mineral Abundance by X-ray Microfluorescence Mapping and Multispectral Image Analysis

    NASA Astrophysics Data System (ADS)

    Moscati, R. J.; Marshall, B. D.

    2005-12-01

    X-ray microfluorescence (XRMF) spectrometry is a rapid, accurate technique to map element abundances of rock surfaces (such as thin-section billets, the block remaining when a thin section is prepared). Scanning a specimen with a collimated primary X-ray beam (100 μm diameter) generates characteristic secondary X-rays that yield the relative chemical abundances for the major rock-/mineral-forming analytes (such as Si, Al, K, Ca, and Fe). When Cu-rich epoxy is used to impregnate billets, XRMF also can determine porosity from the Cu abundance. Common billet scan size is 30 x 15 mm and the typical mapping time rarely exceeds 2.5 hrs (much faster than traditional point-counting). No polishing or coating is required for the billets, although removing coarse striations or gross irregularities on billet surfaces should improve the spatial accuracy of the maps. Background counts, spectral artifacts, and diffraction peaks typically are inconsequential for maps of major elements. An operational check is performed after every 10 analyses on a standard that contains precisely measured areas of Mn and Mo. Reproducibility of the calculated area ratio of Mn:Mo is consistently within 5% of the known value. For each billet, the single element maps (TIFF files) generated by XRMF are imported into MultiSpec© (a program developed at Purdue University for analysis of multispectral image data, available from http://dynamo.ecn.purdue.edu/~biehl/MultiSpec/) where mineral phases can be spectrally identified and their relative abundances quantified. The element maps for each billet are layered to produce a multi-element file for mineral classification and statistical processing, including modal estimates of mineral abundance. Although mineral identification is possible even if the mineralogy is unknown, prior petrographic examination of the corresponding thin section yields more accurate maps because the software can be set to identify all similar pixels. Caution is needed when using

  2. Relative coronal abundances derived from X-ray observations 3: The effect of cascades on the relative intensity of Fe (XVII) line fluxes, and a revised iron abundance

    NASA Technical Reports Server (NTRS)

    Walker, A. B. C., Jr.; Rugge, H. R.; Weiss, K.

    1974-01-01

    Permitted lines in the optically thin coronal X-ray spectrum were analyzed to find the distribution of coronal material, as a function of temperature, without special assumptions concerning coronal conditions. The resonance lines of N, O, Ne, Na, Mg, Al, Si, S, and Ar which dominate the quiet coronal spectrum below 25A were observed. Coronal models were constructed and the relative abundances of these elements were determined. The intensity in the lines of the 2p-3d transitions near 15A was used in conjunction with these coronal models, with the assumption of coronal excitation, to determine the Fe XVII abundance. The relative intensities of the 2p-3d Fe XVII lines observed in the corona agreed with theoretical prediction. Using a more complete theoretical model, and higher resolution observations, a revised calculation of iron abundance relative to hydrogen of 0.000026 was made.

  3. Non-standard s-process in low metallicity massive rotating stars

    NASA Astrophysics Data System (ADS)

    Frischknecht, U.; Hirschi, R.; Thielemann, F.-K.

    2012-02-01

    Context. Rotation is known to have a strong impact on the nucleosynthesis of light elements in massive stars, mainly by inducing mixing in radiative zones. In particular, rotation boosts the primary nitrogen production, and models of rotating stars are able to reproduce the nitrogen observed in low-metallicity halo stars. Aims: Here we present the first grid of stellar models for rotating massive stars at low metallicity, where a full s-process network is used to study the impact of rotation-induced mixing on the neutron capture nucleosynthesis of heavy elements. Methods: We used the Geneva stellar evolution code that includes an enlarged reaction network with nuclear species up to bismuth to calculate 25 M⊙ models at three different metallicities (Z = 10-3,10-5, and 10-7) and with different initial rotation rates. Results: First, we confirm that rotation-induced mixing (shear) between the convective H-shell and He-core leads to a large production of primary 22Ne (0.1 to 1% in mass fraction), which is the main neutron source for the s-process in massive stars. Therefore rotation boosts the s-process in massive stars at all metallicities. Second, the neutron-to-seed ratio increases with decreasing Z in models including rotation, which leads to the complete consumption of all iron seeds at metallicities below Z = 10-3 by the end of core He-burning. Thus at low Z, the iron seeds are the main limitation for this boosted s-process. Third, as the metallicity decreases, the production of elements up to the Ba peak increases at the expense of the elements of the Sr peak. We studied the impact of the initial rotation rate and of the highly uncertain 17O(α,γ) rate (which strongly affects the strength of 16O as a neutron poison) on our results. This study shows that rotating models can produce significant amounts of elements up to Ba over a wide range of Z, which has important consequences for our understanding of the formation of these elements in low

  4. Chemical Compositions and Abundance Anomalies in Stellar Coronae ADP 99

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy; Oliversen, Ronald J. (Technical Monitor)

    2003-01-01

    Progress has been made using both EUVE (Extreme Ultraviolet Explorer) and ASCA (Advanced Satellite for Cosmology and Astrophysics) data and a new postdoctoral scientist has now been hired. Stars studied to date include YY Gem (dMe binary), xi Boo A (intermediate activity G8 V), xi UMa (more active G quadruple system) HR1099 (K1 IV + G5 V) RS CVn-like, AU Mic (dMe). In addition to a paper that concentrated on abundancies in HR1099, a paper was recently submitted on the coronal abundances of AR(tilde)Lac that revealed an interesting pattern of overabundances of very low FIP elements (Al and Ca) compared to the low FIP elements Si, Mg and Fe. Two papers are nearing completion on methods of analysis and on the abundances in the corona of AU(tilde)Mic. Additionally, two invited conference proceedings papers are being published on this work. The main conclusion of the study to date is that our existing ideas of coronal abundance anomalies need complete revision. The solar-like FIP effect is replaced by a pattern than appears to enhance high FIP elements rather than low FIP elements in very active stars. The archival studies we are undertaking now are revealing some key details of these patterns, and are beginning to map out the anomalies as a function of spectral type, a key goal of this study.

  5. When Can Species Abundance Data Reveal Non-neutrality?

    PubMed Central

    Al Hammal, Omar; Alonso, David; Etienne, Rampal S.; Cornell, Stephen J.

    2015-01-01

    Species abundance distributions (SAD) are probably ecology’s most well-known empirical pattern, and over the last decades many models have been proposed to explain their shape. There is no consensus over which model is correct, because the degree to which different processes can be discerned from SAD patterns has not yet been rigorously quantified. We present a power calculation to quantify our ability to detect deviations from neutrality using species abundance data. We study non-neutral stochastic community models, and show that the presence of non-neutral processes is detectable if sample size is large enough and/or the amplitude of the effect is strong enough. Our framework can be used for any candidate community model that can be simulated on a computer, and determines both the sampling effort required to distinguish between alternative processes, and a range for the strength of non-neutral processes in communities whose patterns are statistically consistent with neutral theory. We find that even data sets of the scale of the 50 Ha forest plot on Barro Colorado Island, Panama, are unlikely to be large enough to detect deviations from neutrality caused by competitive interactions alone, though the presence of multiple non-neutral processes with contrasting effects on abundance distributions may be detectable. PMID:25793889

  6. Serial processing of biological reactions using flow-through microfluidic devices: coupled PCR/LDR for the detection of low-abundant DNA point mutations.

    PubMed

    Hashimoto, Masahiko; Barany, Francis; Xu, Feng; Soper, Steven A

    2007-09-01

    We have fabricated a flow-through biochip consisting of passive elements for the analysis of single base mutations in genomic DNA using polycarbonate (PC) as the substrate. The biochip was configured to carry out two processing steps on the input sample, a primary polymerase chain reaction (PCR) followed by an allele-specific ligation detection reaction (LDR) for scoring the presence of low abundant point mutations in genomic DNA. The operation of the device was demonstrated by detecting single nucleotide polymorphisms in gene fragments (K-ras) that carry high diagnostic value for colorectal cancers. The effect of carryover from the primary PCR on the subsequent LDR was investigated in terms of LDR yield and fidelity. We found that a post-PCR treatment step prior to the LDR phase of the assay was not essential. As a consequence, a thermal cycling microchip was used for a sequential PCR/LDR in a simple continuous-flow format, in which the following three steps were carried out: (1) exponential amplification of the gene fragments from genomic DNA; (2) mixing of the resultant PCR product(s) with an LDR cocktail via a Y-shaped passive micromixer; and (3) ligation of two primers (discriminating primer that carried the complement base to the mutation locus being interrogated and a common primer) only when the particular mutation was present in the genomic DNA. We successfully demonstrated the ability to detect one mutant DNA in 1000 normal sequences with the integrated microfluidic system. The PCR/LDR assay using the microchip performed the entire assay at a relatively fast processing speed: 18.7 min for 30 rounds of PCR, 4.1 min for 13 rounds of LDR (total processing time = ca. 22.8 min) and could screen multiple mutations simultaneously in a multiplexed format. In addition, the low cost of the biochip due to the fact that it was fabricated from polymers using replication technologies and consisted of passive elements makes the platform amenable to clinical diagnostics

  7. Siderophile-element Anomalies in CK Carbonaceous Chondrites: Implications for Parent-body Aqueous Alteration and Terrestrial Weathering of Sulfides

    NASA Technical Reports Server (NTRS)

    Huber, Heinz; Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

    2006-01-01

    CK chondrites constitute the most oxidized anhydrous carbonaceous chondrite group; most of the Fe occurs in magnetite and in FeO-rich mafic silicates. The two observed CK falls (Karoonda and Kobe), along with thirteen relatively unweathered CK finds, have unfractionated siderophile-element abundance patterns. In contrast, a sizable fraction of CK finds (9 of 24 investigated) shows fractionated siderophile abundance patterns including low abundances of Ni, Co, Se and Au; the most extreme depletions are in Ni (0.24 of normal CK) and Au (0.14 of normal CK). This depletion pattern has not been found in other chondrite groups. Out of the 74 CK chondrites listed in the Meteoritical Bulletin Database (2006; excluded considerably paired specimens; see http://tin.er.usgs.gov/meteor/ metbull.php) we analyzed 24 and subclassified the CK chondrites in terms of their chemical composition and sulfide mineralogy: sL (siderophiles low; six samples) for large depletions in Ni, Co, Se and Au (>50% of sulfides lost); sM (siderophiles medium; two CKs) for moderately low Ni and Co abundances (sulfides are highly altered or partly lost); sH (siderophiles high; one specimen) for enrichments in Ni, Co, Se and Au; 'normal' for unfractionated samples (13 samples). The sole sH sample may have obtained additional sulfide from impact redistribution in the parent asteroid. We infer that these elements became incorporated into sulfides after asteroidal aqueous processes oxidized nebular metal; thermal metamorphism probably also played a role in their mineral siting. The siderophile losses in the SL and sM samples are mainly the result of oxidation of pentlandite, pyrite and violarite by terrestrial alteration followed by leaching of the resulting phases. Some Antarctic CK chondrites have lost most of their sulfides but retained Ni, Co, Se and Au, presumably as insoluble weathering products.

  8. Distinctive Pattern of Serum Elements During the Progression of Alzheimer’s Disease

    PubMed Central

    Paglia, Giuseppe; Miedico, Oto; Cristofano, Adriana; Vitale, Michela; Angiolillo, Antonella; Chiaravalle, Antonio Eugenio; Corso, Gaetano; Di Costanzo, Alfonso

    2016-01-01

    Element profiling is an interesting approach for understanding neurodegenerative processes, considering that compelling evidences show that element toxicity might play a crucial role in the onset and progression of Alzheimer’s disease (AD). Aim of this study was to profile 22 serum elements in subjects with or at risk of AD. Thirtyfour patients with probable AD, 20 with mild cognitive impairment (MCI), 24 with subjective memory complaint (SMC) and 40 healthy subjects (HS) were included in the study. Manganese, iron, copper, zinc, selenium, thallium, antimony, mercury, vanadium and molybdenum changed significantly among the 4 groups. Several essential elements, such as manganese, selenium, zinc and iron tended to increase in SMC and then progressively to decrease in MCI and AD. Toxic elements show a variable behavior, since some elements tended to increase, while others tended to decrease in AD. A multivariate model, built using a panel of six essential elements (manganese, iron, copper, zinc, selenium and calcium) and their ratios, discriminated AD patients from HS with over 90% accuracy. These findings suggest that essential and toxic elements contribute to generate a distinctive signature during the progression of AD, and their monitoring in elderly might help to detect preclinical stages of AD. PMID:26957294

  9. Reverse transcriptase genes are highly abundant and transcriptionally active in marine plankton assemblages

    PubMed Central

    Lescot, Magali; Hingamp, Pascal; Kojima, Kenji K; Villar, Emilie; Romac, Sarah; Veluchamy, Alaguraj; Boccara, Martine; Jaillon, Olivier; Iudicone, Daniele; Bowler, Chris; Wincker, Patrick; Claverie, Jean-Michel; Ogata, Hiroyuki

    2016-01-01

    Genes encoding reverse transcriptases (RTs) are found in most eukaryotes, often as a component of retrotransposons, as well as in retroviruses and in prokaryotic retroelements. We investigated the abundance, classification and transcriptional status of RTs based on Tara Oceans marine metagenomes and metatranscriptomes encompassing a wide organism size range. Our analyses revealed that RTs predominate large-size fraction metagenomes (>5 μm), where they reached a maximum of 13.5% of the total gene abundance. Metagenomic RTs were widely distributed across the phylogeny of known RTs, but many belonged to previously uncharacterized clades. Metatranscriptomic RTs showed distinct abundance patterns across samples compared with metagenomic RTs. The relative abundances of viral and bacterial RTs among identified RT sequences were higher in metatranscriptomes than in metagenomes and these sequences were detected in all metatranscriptome size fractions. Overall, these observations suggest an active proliferation of various RT-assisted elements, which could be involved in genome evolution or adaptive processes of plankton assemblage. PMID:26613339

  10. The chemical abundance analysis of normal early A- and late B-type stars

    NASA Astrophysics Data System (ADS)

    Fossati, L.; Ryabchikova, T.; Bagnulo, S.; Alecian, E.; Grunhut, J.; Kochukhov, O.; Wade, G.

    2009-09-01

    Context: Modern spectroscopy of early-type stars often aims at studying complex physical phenomena such as stellar pulsation, the peculiarity of the composition of the photosphere, chemical stratification, the presence of a magnetic field, and its interplay with the stellar atmosphere and the circumstellar environment. Comparatively less attention is paid to identifying and studying the “normal” A- and B-type stars and testing how the basic atomic parameters and standard spectral analysis allow one to fit the observations. By contrast, this kind of study is paramount for eventually allowing one to correctly quantify the impact of the various physical processes that occur inside the atmospheres of A- and B-type stars. Aims: We wish to establish whether the chemical composition of the solar photosphere can be regarded as a reference for early A- and late B-type stars. Methods: We have obtained optical high-resolution, high signal-to-noise ratio spectra of three slowly rotating early-type stars (HD 145788, 21 Peg and π Cet) that show no obvious sign of chemical peculiarity, and performed a very accurate LTE abundance analysis of up to 38 ions of 26 elements (for 21 Peg), using a vast amount of spectral lines visible in the spectral region covered by our spectra. Results: We provide an exhaustive description of the abundance characteristics of the three analysed stars with a critical review of the line parameters used to derive the abundances. We compiled a table of atomic data for more than 1100 measured lines that may be used in the future as a reference. The abundances we obtained for He, C, Al, S, V, Cr, Mn, Fe, Ni, Sr, Y, and Zr are compatible with the solar ones derived with recent 3D radiative-hydrodynamical simulations of the solar photosphere. The abundances of the remaining studied elements show some degree of discrepancy compared to the solar photosphere. Those of N, Na, Mg, Si, Ca, Ti, and Nd may well be ascribed to non-LTE effects; for P, Cl, Sc and

  11. Messages from the Reversing Layer: Clues to Planet Formation in Spectral Abundances

    NASA Astrophysics Data System (ADS)

    Brewer, John Michael; Fischer, Debra; Basu, Sarbani

    2017-01-01

    The abundances of elements in the protoplanetary disk evolve over time, but stellar abundances will reflect the initial chemical composition of the disk and this can provide constraints on the range of possible outcomes for planet interiors. Rocky planet habitability depends not just on the availability of liquid water, but also on volcansim and plate tectonics that can stabilize the climate on long timescales. The slow evolution of abundances in stellar photospheres, particularly abundance ratios between elements, makes them ideal laboratories to study primordial disk compositions.In my thesis work, I developed a new spectroscopic analysis procedure that derives gravities consistent with asteroseismology to within 0.05 dex as well as abundances for 15 elements. Using this procedure, we analyzed and published a catalog of accurate stellar parameters and precise abundances for more than 1600 stars and used those to investigate questions of planet formation. The C/O and Mg/Si ratios in the solar neighborhood could affect rocky planet habitability. For lucky cases where planet atmosphereic abundances can be measured, the stellar host C/O and [O/H] ratios carry information about the formation site and migration of hot Jupiters. I will present results on both rocky planet compositions and hot Jupiter migration and discuss how they can help us identify potentially habitable systems and discriminate between different planet formation models.

  12. TEA: A Code Calculating Thermochemical Equilibrium Abundances

    NASA Astrophysics Data System (ADS)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

    2016-07-01

    We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature-pressure pairs. We tested the code against the method of Burrows & Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows & Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

  13. Growing three-dimensional biomorphic graphene powders using naturally abundant diatomite templates towards high solution processability

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Li, Cong; Shi, Liurong; Gao, Teng; Song, Xiuju; Bachmatiuk, Alicja; Zou, Zhiyu; Deng, Bing; Ji, Qingqing; Ma, Donglin; Peng, Hailin; Du, Zuliang; Rümmeli, Mark Hermann; Zhang, Yanfeng; Liu, Zhongfan

    2016-11-01

    Mass production of high-quality graphene with low cost is the footstone for its widespread practical applications. We present herein a self-limited growth approach for producing graphene powders by a small-methane-flow chemical vapour deposition process on naturally abundant and industrially widely used diatomite (biosilica) substrates. Distinct from the chemically exfoliated graphene, thus-produced biomorphic graphene is highly crystallized with atomic layer-thickness controllability, structural designability and less noncarbon impurities. In particular, the individual graphene microarchitectures preserve a three-dimensional naturally curved surface morphology of original diatom frustules, effectively overcoming the interlayer stacking and hence giving excellent dispersion performance in fabricating solution-processible electrodes. The graphene films derived from as-made graphene powders, compatible with either rod-coating, or inkjet and roll-to-roll printing techniques, exhibit much higher electrical conductivity (~110,700 S m-1 at 80% transmittance) than previously reported solution-based counterparts. This work thus puts forward a practical route for low-cost mass production of various powdery two-dimensional materials.

  14. Nutritional assessment of processing effects on major and trace element content in sea buckthorn juice (Hippophaë rhamnoides L. ssp. rhamnoides).

    PubMed

    Gutzeit, D; Winterhalter, P; Jerz, G

    2008-08-01

    Processing effects on the mineral content were investigated during juice production from sea buckthorn (Hippophaë rhamnoides L. ssp. rhamnoides, Elaeagnaceae) using berries from 2 different growing areas. The major and trace elements of sea buckthorn berries and juices were determined by atomic absorption spectroscopy (AAS)--(calcium, iron, magnesium, potassium, sodium) and inductively coupled plasma-mass spectrometry (ICP-MS)--(arsenic, boron, chromium, copper, manganese, molybdenum, nickel, selenium, zinc). Potassium is the most abundant major element in sea buckthorn berries and juices. The production process increased the potassium content in the juice by about 20%. Moreover, the processing of juice increased the value of manganese up to 32% compared to the content in berries. During industrial juice production, the technological steps caused a loss of about 53% to 77% of the chromium concentration, 50% of the copper content, 64% to 75% of the molybdenum amount, and up to 45% of the iron concentration in the final juice product. Consumption of sea buckthorn juice represents a beneficial source of chromium, copper, manganese, molybdenum, iron, and potassium for the achievement of the respective dietary requirements.

  15. Using Elemental Abundances and Petrophysical Properties to Trace Sediment Transport in the Hudson River

    NASA Astrophysics Data System (ADS)

    Chang, C.; Kenna, T. C.; Nitsche, F. O.

    2016-12-01

    The IPCC predicts that the frequency and severity of storms worldwide will increase due to climate change, a growing concern for the highly populated coastal areas near the Hudson River estuary. Storms have the potential to change the river's sediment budget, and it is necessary to update the current understanding of the effect of storms on sediment dynamics. In 2011, Tropical Storm Lee and Hurricane Irene delivered over 2.7 million tons of sediment to the Hudson River including over 1.5 million tons from the Mohawk River, a freshwater tributary, in addition to record amounts contributed from other major tributaries. The goals of this project are to use sediment elemental compositions to trace the major tributaries contributing to this storm-deposited sediment and to determine where sediment is accumulating as a result of storm activity. Chemical analysis of over 800 archived sediment samples are compiled to provide a pre-storm background level. These samples are compared to newly deposited sediment and material from specific tributaries. Elemental abundances (K, Ca, Ti, Cr, Mn, Fe, Co, Cu, Zn, Rb, Sr, Zr, Pb, and U) are measured using a field portable X-Ray Fluorescence (XRF) unit and core scanning XRF unit. Bulk matrix density is measured using a pycnometer. The measurements are used to identify elemental signatures from tributary sediment and to trace the influence of specific tributaries on deposition through the river. Our results suggests measureable signatures in sediment from individual tributaries. The Mohawk River contributes high concentrations of Ca due to the calcite deposits in its watershed. XRF measurements also show the effect of human activity on sediment deposition; variations in Rb and Zr indicate changes in deposition due to dredging in Haverstraw Bay. The salt wedge front, where ocean and fresh water meets is evident in areas of below average matrix density. This project shows significant geochemical variability between sediment from different

  16. Major and Trace Element Analysis of Natural and Experimental Igneous Systems using LA-ICP-MS

    NASA Technical Reports Server (NTRS)

    Jenner, Frances E.; Arevalo, Ricardo D., Jr.

    2016-01-01

    Major- and trace-element compositions of minerals provide valuable information on a variety of global Earth-system processes, including melting of distinct mantle reservoirs, the growth and evolution of the Earths crust and the formation of economically viable ore deposits. In the mid-1980s and early 1990s, attempts were made to couple laser ablation (LA) systems to inductively coupled plasma mass spectrometry (ICPMS) instruments (e.g. Fryer et al. 1995; Jackson et al. 1992). The goal was to develop a rapid, highly sensitive in situ analytical technique to measure abundances and spatial distributions of trace elements in minerals and other geological samples. Elemental analysis using LAICPMS was envisaged as a quicker and less destructive means of chemical analysis (requiring only g quantities) than labour-intensive sample digestion and solution analysis (requiring mg-levels of material); and it would be a more cost-effective method than secondary ion mass spectrometry (SIMS) for the routine analysis of trace elements from solid samples. Furthermore, it would have lower limits-of-detection than electron probe microanalysis (EPMA) (e.g. Jackson et al. 1992; Eggins 2003).

  17. Galactic interstellar abundance surveys with IUE and IRAS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Van Steenberg, M.E.

    1987-01-01

    This thesis is a survey of interstellar densities, abundances, and cloud structure in the Galaxy, using two NASA satellites: the International Ultraviolet Explorer (IUE) and Infrared Astronomical Satellite (IRAS). From IUE high-resolution spectra, the author measured equivalent widths of 18 ultraviolet resonance transitions and derived column densities for Si/sup +/, Mn/sup +/, Fe/sup +/, S/sup +/, and Zn/sup +/ toward 261 early-type stars. From the IRAS all-sky survey he also measured the infrared cirrus flux. He examined the variations of the measured parameters with spectral type, E(B-V), galactic longitude and latitude, distance from the Sun, and mean density. The hydrogen-columnmore » densities, metal-column densities, and gas-to-dust ratio are in good agreement with Copernicus surveys. The derived interstellar abundances yield mean logarithmic depletions. These depletions correlate with mean density but not with the physical density derived from Copernicus H/sub 2/ rotational states. Abundance ratios indicate a larger Fe halo abundance compared to Si, Mn, S, or Zn, which may result from selective grain processing in shocks or from Type I supernovae.« less

  18. The Design Process of Physical Security as Applied to a U.S. Border Point of Entry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wagner, G.G.

    1998-10-26

    This paper describes the design process of physical security as applied to a U.S. Border Port of Entry (PoE). Included in this paper are descriptions of the elements that compose U.S. border security. The physical security design will describe the various elements that make up the process as well as the considerations that must be taken into account when dealing with system integration of those elements. The distinctions between preventing unlawful entry and exit of illegal contraband will be emphasized.

  19. Element Abundances in a Gas-rich Galaxy at z = 5: Clues to the Early Chemical Enrichment of Galaxies

    NASA Astrophysics Data System (ADS)

    Morrison, Sean; Kulkarni, Varsha P.; Som, Debopam; DeMarcy, Bryan; Quiret, Samuel; Péroux, Celine

    2016-10-01

    Element abundances in high-redshift quasar absorbers offer excellent probes of the chemical enrichment of distant galaxies, and can constrain models for population III and early population II stars. Recent observations indicate that the sub-damped Lyα (sub-DLA) absorbers are more metal-rich than DLA absorbers at redshifts 0 < z < 3. It has also been suggested that DLA metallicity drops suddenly at z > 4.7. However, only three DLAs at z > 4.5 and no sub-DLAs at z > 3.5 have “dust-free” metallicity measurements of undepleted elements. We report the first quasar sub-DLA metallicity measurement at z > 3.5, from detections of undepleted elements in high-resolution data for a sub-DLA at z = 5.0. We obtain fairly robust abundances of C, O, Si, and Fe, using lines outside the Lyα forest. This absorber is metal-poor, with [O/H] = -2.00 ± 0.12, which is ≳4σ below the level expected from extrapolation of the trend for z < 3.5 sub-DLAs. The C/O ratio is {1.8}-0.3+0.4 times lower than in the Sun. More strikingly, Si/O is {3.2}-0.5+0.6 times lower than in the Sun, whereas Si/Fe is nearly (1.2{}-0.3+0.4 times) solar. This absorber does not display a clear alpha/Fe enhancement. Dust depletion may have removed more Si from the gas phase than is common in the Milky Way interstellar medium, which may be expected if high-redshift supernovae form more silicate-rich dust. C/O and Si/O vary substantially between different velocity components, indicating spatial variations in dust depletion and/or early stellar nucleosynthesis (e.g., population III star initial mass function). The higher velocity gas may trace an outflow enriched by early stars. Based on observations obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  20. The Coronal Abundance Anomalies of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

    2012-07-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an "inverse FIP effect" is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  1. Catalyst for elemental sulfur recovery process

    DOEpatents

    Flytzani-Stephanopoulos, Maria; Liu, Wei

    1995-01-01

    A catalytic reduction process for the direct recovery of elemental sulfur from various SO.sub.2 -containing industrial gas streams. The catalytic process provides high activity and selectivity, as well as stability in the reaction atmosphere, for the reduction of SO.sub.2 to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over a metal oxide composite catalyst having one of the following empirical formulas: [(OF.sub.2).sub.1-n (RO.sub.1)n].sub.1-k M.sub.k, [(FO.sub.2).sub.1-n (RO.sub.1.5).sub.n ].sub.1-k M.sub.k, or [Ln.sub.x Zr.sub.1-x O.sub.2-0.5x ].sub.1-k M.sub.k wherein FO.sub.2 is a fluorite-type oxide; RO represents an alkaline earth oxide; RO.sub.1.5 is a Group IIIB or rare earth oxide; Ln is a rare earth element having an atomic number from 57 to 65 or mixtures thereof; M is a transition metal or a mixture of transition metals; n is a number having a value from 0.0 to 0.35; k is a number having a value from 0.0 to about 0.5; and x is a number having a value from about 0.45 to about 0.55.

  2. Environmental implications of element emissions from phosphate-processing operations in southeastern Idaho

    USGS Publications Warehouse

    Severson, R.C.; Gough, L.P.

    1979-01-01

    In order to assess the contribution to plants and soils of certain elements emitted by phosphate processing, we sampled sagebrush, grasses, and A- and C-horizon soils along upwind and downwind transects at Pocatello and Soda Springs, Idaho. Analyses for 70 elements in plants showed that, statistically, the concentration of 7 environmentally important elements, cadmium, chromium, fluorine, selenium, uranium, vanadium, and zinc, were related to emissions from phosphate-processing operations. Two additional elements, lithium and nickel, show probable relationships. The literature on the effects of these elements on plant and animal health is briefly surveyed. Relations between element content in plants and distance from the phosphate-processing operations were stronger at Soda Springs than at Pocatello and, in general, stronger in sagebrush than in the grasses. Analyses for 58 elements in soils showed that, statistically, beryllium, fluorine, iron, lead, lithium, potassium, rubidium, thorium, and zinc were related to emissions only at Pocatello and only in the A horizon. Moreover, six additional elements, copper, mercury, nickel, titanium, uranium, and vanadium, probably are similarly related along the same transect. The approximate amounts of elements added to the soils by the emissions are estimated. In C-horizon soils, no statistically significant relations were observed between element concentrations and distance from the processing sites. At Soda Springs, the nonuniformity of soils at the sampling locations may have obscured the relationship between soil-element content and emissions from phosphate processing.

  3. Processes entangling interactions in communities: forbidden links are more important than abundance in a hummingbird-plant network.

    PubMed

    Vizentin-Bugoni, Jeferson; Maruyama, Pietro Kiyoshi; Sazima, Marlies

    2014-04-07

    Understanding the relative importance of multiple processes on structuring species interactions within communities is one of the major challenges in ecology. Here, we evaluated the relative importance of species abundance and forbidden links in structuring a hummingbird-plant interaction network from the Atlantic rainforest in Brazil. Our results show that models incorporating phenological overlapping and morphological matches were more accurate in predicting the observed interactions than models considering species abundance. This means that forbidden links, by imposing constraints on species interactions, play a greater role than species abundance in structuring the ecological network. We also show that using the frequency of interaction as a proxy for species abundance and network metrics to describe the detailed network structure might lead to biased conclusions regarding mechanisms generating network structure. Together, our findings suggest that species abundance can be a less important driver of species interactions in communities than previously thought.

  4. Processes entangling interactions in communities: forbidden links are more important than abundance in a hummingbird–plant network

    PubMed Central

    Vizentin-Bugoni, Jeferson; Maruyama, Pietro Kiyoshi; Sazima, Marlies

    2014-01-01

    Understanding the relative importance of multiple processes on structuring species interactions within communities is one of the major challenges in ecology. Here, we evaluated the relative importance of species abundance and forbidden links in structuring a hummingbird–plant interaction network from the Atlantic rainforest in Brazil. Our results show that models incorporating phenological overlapping and morphological matches were more accurate in predicting the observed interactions than models considering species abundance. This means that forbidden links, by imposing constraints on species interactions, play a greater role than species abundance in structuring the ecological network. We also show that using the frequency of interaction as a proxy for species abundance and network metrics to describe the detailed network structure might lead to biased conclusions regarding mechanisms generating network structure. Together, our findings suggest that species abundance can be a less important driver of species interactions in communities than previously thought. PMID:24552835

  5. Combinatorial development of Cu2SnS3 as an earth abundant photovoltaic absorber

    NASA Astrophysics Data System (ADS)

    Baranowski, Lauryn L.

    The development of high efficiency, earth abundant photovoltaic absorbers is critical if photovoltaics are to be implemented on the TW scale. Although traditional thin films absorbers such as Cu(In,Ga)Se2 and CdTe have achieved over 20% device efficiencies, the ultimately scalability of these devices may be limited by elemental scarcity and toxicity issues. To date, the most successful earth abundant thin film absorber is Cu2ZnSn(S,Se) 4, which has achieved 12.6% efficiency as of 2014. However, chemical complexity and disorder issues with this material have made the path to higher efficiency CZTSSe devices unclear. As a result, many researchers are now exploring alternative earth abundant absorber materials. In this thesis, we apply our "rapid development" methodology to the exploration of alternative photovoltaic absorbers. The rapid development (RD) methodology, consisting of exploration, research, and development stages, uses complementary theory and experiment to assess candidate materials and down-select in each stage. The overall result is that, in the time span of ~2-3 years, we are able to rapidly go from tens of possible absorber materials to 1-2 working PV device prototypes. Here, we demonstrate the RD approach as applied to the Cu-Sn-S system. We begin our investigation of the Cu-Sn-S system by evaluating the thermodynamic stability, electrical transport, electronic structure, and optical and defect properties of candidate materials using complementary theory and experiment. We find that Cu2SnS3 is the most promising absorber candidate because of its strong optical absorption, tunable doping, and wide stability range. Our other candidate compounds suffer from serious flaws that preclude them from being successful photovoltaic absorbers, including too high experimental conductivity (Cu4SnS4), or poor hole transport and low absorption coefficient (Cu4Sn7S16). Next, we investigate the doping and defect physics of Cu2SnS 3. We identify the origins of the

  6. Elemental Abundances and their Implications for the Chemical Enrichment of the Boötes I Ultrafaint Galaxy

    NASA Astrophysics Data System (ADS)

    Gilmore, Gerard; Norris, John E.; Monaco, Lorenzo; Yong, David; Wyse, Rosemary F. G.; Geisler, D.

    2013-01-01

    We present a double-blind analysis of high-dispersion spectra of seven red giant members of the Boötes I ultrafaint dwarf spheroidal galaxy, complemented with re-analysis of a similar spectrum of an eighth-member star. The stars cover [Fe/H] from -3.7 to -1.9 and include a CEMP-no star with [Fe/H] = -3.33. We conclude from our chemical abundance data that Boötes I has evolved as a self-enriching star-forming system, from essentially primordial initial abundances. This allows us uniquely to investigate the place of CEMP-no stars in a chemically evolving system, in addition to limiting the timescale of star formation. The elemental abundances are formally consistent with a halo-like distribution, with enhanced mean [α/Fe] and small scatter about the mean. This is in accord with the high-mass stellar initial mass function in this low-stellar-density, low-metallicity system being indistinguishable from the present-day solar neighborhood value. There is a non-significant hint of a decline in [α/Fe] with [Fe/H]; together with the low scatter, this requires low star formation rates, allowing time for supernova ejecta to be mixed over the large spatial scales of interest. One star has very high [Ti/Fe], but we do not confirm a previously published high value of [Mg/Fe] for another star. We discuss the existence of CEMP-no stars, and the absence of any stars with lower CEMP-no enhancements at higher [Fe/H], a situation that is consistent with knowledge of CEMP-no stars in the Galactic field. We show that this observation requires there be two enrichment paths at very low metallicities: CEMP-no and "carbon-normal." Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal P82.182.B-0372, PI: G. Gilmore).

  7. On the e-process - Its components and their neutron excesses. [solar abundance calculations in gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Hainebach, K. L.; Clayton, D. D.; Arnett, W. D.; Woosley, S. E.

    1974-01-01

    The pattern of abundances within the iron-abundance peak of the solar system is analyzed for various Cr, Fe, and Ni abundances, and a method is developed for finding the best fit to a given set of abundances with a chosen number of zones, i.e., mass contributions characterized by differing values of eta. This material can be synthesized by a superposition of e-process compositions in a low-eta region (eta = 0.003) and a high-eta region (eta = 0.065 -0.080) with at least 85% coming from the low-eta region. Addition of a third eta zone is unproductive. The applicability of the particle-poor freeze out is discussed in the light of these abundances, and the results of employing different numbers and types of zones are interpreted as an indication of the relative abundances themselves. Ejection of the low-eta zones is of great interest in gamma-ray astronomy and for empirical testing of theories of nucleosynthesis. The distribution of high zones should give important information about the formation of collapsed remnants.

  8. The solar wind neon abundance observed with ACE/SWICS and ULYSSES/SWICS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shearer, Paul; Raines, Jim M.; Lepri, Susan T.

    Using in situ ion spectrometry data from ACE/SWICS, we determine the solar wind Ne/O elemental abundance ratio and examine its dependence on wind speed and evolution with the solar cycle. We find that Ne/O is inversely correlated with wind speed, is nearly constant in the fast wind, and correlates strongly with solar activity in the slow wind. In fast wind streams with speeds above 600 km s{sup –1}, we find Ne/O = 0.10 ± 0.02, in good agreement with the extensive polar observations by Ulysses/SWICS. In slow wind streams with speeds below 400 km s{sup –1}, Ne/O ranges from amore » low of 0.12 ± 0.02 at solar maximum to a high of 0.17 ± 0.03 at solar minimum. These measurements place new and significant empirical constraints on the fractionation mechanisms governing solar wind composition and have implications for the coronal and photospheric abundances of neon and oxygen. The results are made possible by a new data analysis method that robustly identifies rare elements in the measured ion spectra. The method is also applied to Ulysses/SWICS data, which confirms the ACE observations and extends our view of solar wind neon into the three-dimensional heliosphere.« less

  9. Abundances and Kinematics of OB Stars in the Leading Arm of the Magellanic System

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Moni Bidin, C.; Casetti-Dinescu, D. I.; Mendez, R. A.; Girard, T. M.; Korchagin, V. I.; Vieira, K.; van Altena, W. F.; Zhao, G.

    2018-01-01

    We determined seven element abundances (He, C, N, O, Mg, Si, and S) and kinematics for eight O-/B- type stars which is selected from 42 candidates (Casetti-Dinescu et al. 2014) of membership in the Leading Arm (LA) of the Magellanic System. The high resolution spectra were taken with the MIKE instrument on the Magellan 6.5m Clay telescope.

  10. Experimental constraints on light elements in the Earth’s outer core

    PubMed Central

    Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian

    2016-01-01

    Earth’s outer core is liquid and dominantly composed of iron and nickel (~5–10 wt%). Its density, however, is ~8% lower than that of liquid iron, and requires the presence of a significant amount of light element(s). A good way to specify the light element(s) is a direct comparison of density and sound velocity measurements between seismological data and those of possible candidate compositions at the core conditions. We report the sound velocity measurements of a model core composition in the Fe-Ni-Si system at the outer core conditions by shock-wave experiments. Combining with the previous studies, we found that the best estimate for the outer core’s light elements is ~6 wt% Si, ~2 wt% S, and possible ~1–2.5 wt% O. This composition satisfies the requirements imposed by seismology, geochemistry, and some models of the early core formation. This finding may help us to further constrain the thermal structure of the Earth and the models of Earth’s core formation. PMID:26932596

  11. ATMOSPHERIC COMPOSITION OF WEAK G BAND STARS: CNO AND Li ABUNDANCES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Adamczak, Jens; Lambert, David L., E-mail: adamczak@astro.as.utexas.edu

    We determined the chemical composition of a large sample of weak G band stars-a rare class of G and K giants of intermediate mass with unusual abundances of C, N, and Li. We have observed 24 weak G band stars with the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory and derived spectroscopic abundances for C, N, O, and Li, as well as for selected elements from Na-Eu. The results show that the atmospheres of weak G band stars are highly contaminated with CN-cycle products. The C underabundance is about a factor of 20 larger than for normalmore » giants and the {sup 12}C/{sup 13}C ratio approaches the CN-cycle equilibrium value. In addition to the striking CN-cycle signature the strong N overabundance may indicate the presence of partially ON-cycled material in the atmospheres of the weak G band stars. The exact mechanism responsible for the transport of the elements to the surface has yet to be identified but could be induced by rapid rotation of the main sequence progenitors of the stars. The unusually high Li abundances in some of the stars are an indicator for Li production by the Cameron-Fowler mechanism. A quantitative prediction of a weak G band star's Li abundance is complicated by the strong temperature sensitivity of the mechanism and its participants. In addition to the unusual abundances of CN-cycle elements and Li, we find an overabundance of Na that is in accordance with the NeNa chain running in parallel with the CN cycle. Apart from these peculiarities, the element abundances in a weak G band star's atmosphere are consistent with those of normal giants.« less

  12. Atmospheric Composition of Weak G Band Stars: CNO and Li Abundances

    NASA Astrophysics Data System (ADS)

    Adamczak, Jens; Lambert, David L.

    2013-03-01

    We determined the chemical composition of a large sample of weak G band stars—a rare class of G and K giants of intermediate mass with unusual abundances of C, N, and Li. We have observed 24 weak G band stars with the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory and derived spectroscopic abundances for C, N, O, and Li, as well as for selected elements from Na-Eu. The results show that the atmospheres of weak G band stars are highly contaminated with CN-cycle products. The C underabundance is about a factor of 20 larger than for normal giants and the 12C/13C ratio approaches the CN-cycle equilibrium value. In addition to the striking CN-cycle signature the strong N overabundance may indicate the presence of partially ON-cycled material in the atmospheres of the weak G band stars. The exact mechanism responsible for the transport of the elements to the surface has yet to be identified but could be induced by rapid rotation of the main sequence progenitors of the stars. The unusually high Li abundances in some of the stars are an indicator for Li production by the Cameron-Fowler mechanism. A quantitative prediction of a weak G band star's Li abundance is complicated by the strong temperature sensitivity of the mechanism and its participants. In addition to the unusual abundances of CN-cycle elements and Li, we find an overabundance of Na that is in accordance with the NeNa chain running in parallel with the CN cycle. Apart from these peculiarities, the element abundances in a weak G band star's atmosphere are consistent with those of normal giants.

  13. Oxygen Abundances in the Rings of Polar-Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Radtke, I. R.; Eskridge, P. B.; Pogge, R. W.

    2003-05-01

    Polar ring galaxies (PRGs) are typically early-type (S0 or E) galaxies surrounded by rings of gas, dust, and stars orbiting nearly perpendicular to the principle plane of the host galaxy (Whitmore et al. 1990 AJ 100 1489). Given that PRGs have two separate, perpendicular axes of rotation, it is clear on dynamical grounds that PRGs are the products of merger events between two galaxies, but are observed in a state where two distinct kinematic and morphological structures are still apparent. As such, they present a unique opportunity to study merger events in systems where the debris is not confused with material from the host. Our understanding of the relative importance of polar ring systems in the overall process of galaxy evolution is confounded by our lack of knowledge regarding the typical lifetimes and evolutionary histories of polar rings. A crucial factor for understanding the formation and evolution of PRGs is information regarding the elemental abundances of the ring material. Polar rings are typically rich in {\\protectH 2} regions. Optical spectroscopy of these {\\protectH 2} regions can tell us their density, temperature, and oxygen abundance. Our earlier work (Eskridge & Pogge 1997 ApJ 486 259) revealed roughly Solar oxygen abundances for {\\protectH 2} regions in the polar ring of NGC 2685. We have extended this project, and now have spectra for six PRGs. Analysis of the data for II Zw 73 and UGC 7576 reveal the polar rings of these galaxies to have {\\protectH 2} region oxygen abundances in the range 0.3 to 0.6 Solar, substantially less than found for NGC 2685. Abundances in this range are much easier to explain with conventional models of chemical enrichment and polar ring formation. We shall present results for our full sample. Taken as a whole, this sample will provide a clear foundation for the typical chemical enrichment patterns in polar rings, and thus provide a clearer understanding of the formation and evolution of these curious objects. We

  14. Fate and abundance of classical and heteroatomic naphthenic acid species after advanced oxidation processes: Insights and indicators of transformation and degradation.

    PubMed

    Meshref, Mohamed N A; Chelme-Ayala, Pamela; Gamal El-Din, Mohamed

    2017-11-15

    The toxicological effects from all components in oil sands process-affected water (OSPW) are not known. Alternatively, monitoring the variations and abundance of different classes and compounds after treatments might be a useful approach in OSPW remediation. In this study, the variations in the compositions of classical and heteroatomic naphthenic acids (NAs) after treatment using advanced oxidation processes (AOPs), mainly ozone and peroxone, and two different mass spectrometry methods; ultra-performance liquid chromatography time-of-flight (UPLC-TOFMS) and Fourier transform ion cyclotron resonance (FTICR-MS), were examined. Two markers (O 2 S:O 3 S:O 4 S and O 2 :O 4 ratios) were used to reveal changes and similarities of the treated water characteristics with those in natural waters. Both ratios decreased after all treatments, from 2.7:4.8:2.1 and 3.59 in raw OSPW to 0:1.4:0.5 and 0.7, respectively, in peroxone (1:2), becoming close to the reported ratios in natural waters. Toxicity toward Vibrio fischeri showed residual toxic effects after AOPs, suggesting that part of OSPW toxicity may be caused by specific compounds of NAs (i.e., similar reduction (50%) was achieved in both toxicity and abundance in O 2 species with carbon 15-26) and/or generated by-products (e.g., O 3 S classes at double bond equivalent (DBE) = 4 and C 9 H 12 O 2 at DBE = 4). Although by-products were generated, the best biodegradability enhancement and chemical oxygen demand reduction were achieved in peroxone (1:2) compared to ozone, suggesting the possibility of using combined OSPW remediation approaches (i.e., peroxone coupled with biological process). The recommended indicators can assist in evaluating the treatments' performance and in examining the best removal levels to accomplish significant toxicity reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Transposable elements as genetic regulatory substrates in early development.

    PubMed

    Gifford, Wesley D; Pfaff, Samuel L; Macfarlan, Todd S

    2013-05-01

    The abundance and ancient origins of transposable elements (TEs) in eukaryotic genomes has spawned research into the potential symbiotic relationship between these elements and their hosts. In this review, we introduce the diversity of TEs, discuss how distinct classes are uniquely regulated in development, and describe how they appear to have been coopted for the purposes of gene regulation and the orchestration of a number of processes during early embryonic development. Although young, active TEs play an important role in somatic tissues and evolution, we focus mostly on the contributions of the older, fixed elements in mammalian genomes. We also discuss major challenges inherent in the study of TEs and contemplate future experimental approaches to further investigate how they coordinate developmental processes. Published by Elsevier Ltd.

  16. Transposable elements as genetic regulatory substrates in early development

    PubMed Central

    Gifford, Wesley D.; Pfaff, Samuel L.; Macfarlan, Todd S.

    2014-01-01

    The abundance and ancient origins of transposable elements (TEs) in eukaryotic genomes has spawned research into the potential symbiotic relationship between these elements and their hosts. In this review, we introduce the diversity of TEs, discuss how distinct classes are uniquely regulated in development, and describe how they appear to have been coopted for the purposes of gene regulation and the orchestration of a number of processes during early embryonic development. Although young, active TEs play an important role in somatic tissues and evolution, we focus mostly on the contributions of the older, fixed elements in mammalian genomes. We also discuss major challenges inherent in the study of TEs and contemplate future experimental approaches to further investigate how they coordinate developmental processes. PMID:23411159

  17. Spatial Attention Enhances Perceptual Processing of Single-Element Displays

    NASA Technical Reports Server (NTRS)

    Bacon, William; Johnston, James C.; Remington, Roger W.; Null, Cynthia H. (Technical Monitor)

    1994-01-01

    Shiu and Pashler (1993) reported that precueing masked, single-element displays had negligible effects on identification accuracy. They argued that spatial attention does not actually enhance stimulus perceptibility, but only reduces decision noise. Alternatively, such negative results may arise if cues are sub-optimal, or if masks place an insufficient premium on timely deployment of attention. We report results showing that valid cueing enhances processing of even single-element displays. Spatial attention does indeed enhance perceptual processes.

  18. NEON AND OXYGEN ABUNDANCES AND ABUNDANCE RATIO IN THE SOLAR CORONA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Landi, E.; Testa, P., E-mail: elandi@umich.edu

    2015-02-20

    In this work we determine the Ne/O abundance ratio from Solar and Heliospheric Observatory (SOHO)/Solar Ultraviolet Measurement of Emitted Radiation (SUMER) off-disk observations of quiescent streamers over the 1996-2008 period. We find that the Ne/O ratio is approximately constant over solar cycle 23 from 1996 to 2005, at a value of 0.099 ± 0.017; this value is lower than the transition region determinations from the quiet Sun used to infer the neon photospheric abundance from the oxygen photospheric abundance. Also, the Ne/O ratio we determined from SUMER is in excellent agreement with in situ determinations from ACE/SWICS. In 2005-2008, the Ne/O abundancemore » ratio increased with time and reached 0.25 ± 0.05, following the same trend found in the slowest wind analyzed by ACE/SWICS. Further, we measure the absolute abundance in the corona for both oxygen and neon from the data set of 1996 November 22, obtaining A {sub o} = 8.99 ± 0.04 and A {sub Ne} = 7.92 ± 0.03, and we find that both elements are affected by the first ionization potential (FIP) effect, with oxygen being enhanced by a factor of 1.4-2.1 over its photospheric abundance, and neon being changed by a factor of 0.75-1.20. We conclude that the Ne/O ratio is not constant in the solar atmosphere, both in time and at different heights, and that it cannot be reliably used to infer the neon abundance in the photosphere. Also, we argue that the FIP effect was less effective during the minimum of solar cycle 24, and that the Ne/O = 0.25 ± 0.05 value measured at that time is closer to the true photospheric value, leading to a neon photospheric abundance larger than assumed by ≈40%. We discuss the implications of these results for the solar abundance problem, for the FIP effect, and for the identification of the source regions of the solar wind.« less

  19. TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver, E-mail: jasmina@physics.ucf.edu

    2016-07-01

    We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but withmore » higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.« less

  20. DETAILED ABUNDANCES OF THE SOLAR TWINS 16 CYGNI A AND B: CONSTRAINING PLANET FORMATION MODELS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schuler, Simon C.; Cunha, Katia; Smith, Verne V.

    2011-08-20

    Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16 Cyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16 Cyg B is known to host a giant planet while no planets have yet been detected around 16 Cyg A. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with {Delta}T{sub eff} = +43 K, {Delta}log g = -0.02 dex, and {Delta}{xi} = +0.10 km s{sup -1} (in the sense of A - B), consistent with previous findings. Abundances of 15 elements aremore » derived and are found to be indistinguishable between the two stars. The abundances of each element differ by {<=}0.026 dex, and the mean difference is +0.003 {+-} 0.015 ({sigma}) dex. Aside from Li, which has been previously shown to be depleted by a factor of at least 4.5 in 16 Cyg B relative to 16 Cyg A, the two stars appear to be chemically identical. The abundances of each star demonstrate a positive correlation with the condensation temperature of the elements (T{sub c}); the slopes of the trends are also indistinguishable. In accordance with recent suggestions, the positive slopes of the [m/H]-T{sub c} relations may imply that terrestrial planets have not formed around either 16 Cyg A or 16 Cyg B. The physical characteristics of the 16 Cyg system are discussed in terms of planet formation models, and plausible mechanisms that can account for the lack of detected planets around 16 Cyg A, the disparate Li abundances of 16 Cyg A and B, and the eccentricity of the planet 16 Cyg B b are suggested.« less

  1. VizieR Online Data Catalog: Neutron-capture elements abundances in Cepheids (da Silva+ 2016)

    NASA Astrophysics Data System (ADS)

    da Silva, R.; Lemasle, B.; Bono, G.; Genovali, K.; McWilliam, A.; Cristallo, S.; Bergemann, M.; Buonanno, R.; Fabrizio, M.; Ferraro, I.; Francois, P.; Iannicola, G.; Inno, L.; Laney, C. D.; Kudritzki, R.-P.; Matsunaga, N.; Nonino, M.; Primas, F.; Przybilla, N.; Romaniello, M.; Thevenin, F.; Urbaneja, M. A.

    2015-11-01

    The abundances of Fe, Y, La, Ce, Nd, and Eu for our sample of 73 Cepheids plus data available in the literature for other 362 Cepheids are shown. We first show the abundances derived based on individual spectra for the 73 stars, then the averaged values, and finally the data from the literature. The original abundances available in the literature were rescaled according to the zero-point differences listed in Table 5. The priority was given in the following order: we first adopt the abundances provided by our group, this study (TS) and Lemasle et al. (2013A&A...558A..31L, LEM), and then those provided by the other studies, Luck & Lambert (2011AJ....142..136L, LIII), and Luck et al. (2011AJ....142...51L, LII). (4 data files).

  2. The Odd Isotope Fractions of Barium in the Strongly r-process-enhanced (r-II) Stars

    NASA Astrophysics Data System (ADS)

    Wenyuan, Cui; Xiaohua, Jiang; Jianrong, Shi; Gang, Zhao; Bo, Zhang

    2018-02-01

    We determined the f odd,Ba values, 0.46 ± 0.08, 0.51 ± 0.09, 0.50 ± 0.13, and 0.48 ± 0.12, that correspond to the r-contribution 100% for four r-II stars, CS 29491-069, HE 1219-0312, HE 2327-5642, and HE 2252-4225, respectively. Our results suggest that almost all of the heavy elements (in the range from Ba to Pb) in r-II stars have a common origin, that is, from a single r-process (the main r-process). We found that the f odd,Ba has an intrinsic nature, and should keep a constant value of about 0.46 in the main r-process yields, which is responsible for the heavy element enhancement of r-II stars and of our Galaxy chemical enhancement. In addition, except for the abundance ratio [Ba/Eu] the f odd,Ba is also an important indicator, which can be used to study the relative contributions of the r- and s-processes during the chemical evolution history of the Milky Way and the enhancement mechanism in stars with peculiar abundances of heavy elements. Based on observations carried out at the European Southern Observatory, Paranal, Chile (Proposal number 170.D-0010 and 280.D-5011).

  3. Core-Mantle Partitioning of Volatile Siderophile Elements and the Origin of Volatile Elements in the Earth

    NASA Technical Reports Server (NTRS)

    Nickodem, K.; Righter, K.; Danielson, L.; Pando, K.; Lee, C.

    2012-01-01

    There are currently several hypotheses on the origin of volatile siderophile elements in the Earth. One hypothesis is that they were added during Earth s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile elements are depleted in Earth s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The Earth s core is composed of Fe and some lighter constituents, although the abundances of these lighter elements are unknown [4]. Si is one of these potential light elements [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile elements. As, In, Ge, and Sb are trace volatile siderophile elements which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these elements will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile elements found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these elements in or-der to gain a greater understanding of the core-mantle separation which occurred during the Earth s early stages. The data can then be applied to the origin of volatile elements in the Earth.

  4. SP_Ace: Stellar Parameters And Chemical abundances Estimator

    NASA Astrophysics Data System (ADS)

    Boeche, C.; Grebel, E. K.

    2018-05-01

    SP_Ace (Stellar Parameters And Chemical abundances Estimator) estimates the stellar parameters Teff, log g, [M/H], and elemental abundances. It employs 1D stellar atmosphere models in Local Thermodynamic Equilibrium (LTE). The code is highly automated and suitable for analyzing the spectra of large spectroscopic surveys with low or medium spectral resolution (R = 2000-20 000). A web service for calculating these values with the software is also available.

  5. Rolling Process Modeling Report. Finite-Element Model Validation and Parametric Study on various Rolling Process parameters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soulami, Ayoub; Lavender, Curt A.; Paxton, Dean M.

    2015-06-15

    Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum alloy plate-type fuel for high-performance research reactors in the United States. This work supports the U.S. Department of Energy National Nuclear Security Administration’s Office of Material Management and Minimization Reactor Conversion Program. This report documents modeling results of PNNL’s efforts to perform finite-element simulations to predict roll-separating forces for various rolling mill geometries for PNNL, Babcock & Wilcox Co., Y-12 National Security Complex, Los Alamos National Laboratory, and Idaho National Laboratory. The model developed and presented in a previous report has been subjected to further validationmore » study using new sets of experimental data generated from a rolling mill at PNNL. Simulation results of both hot rolling and cold rolling of uranium-10% molybdenum coupons have been compared with experimental results. The model was used to predict roll-separating forces at different temperatures and reductions for five rolling mills within the National Nuclear Security Administration Fuel Fabrication Capability project. This report also presents initial results of a finite-element model microstructure-based approach to study the surface roughness at the interface between zirconium and uranium-10% molybdenum.« less

  6. U.S. Geological Survey Trace Elements and related reports through 1953

    USGS Publications Warehouse

    Wallace, Jane H.; Blatcher, Virginia K.; Smith, Harriet B.

    1954-01-01

    This report combines and brings up-to-date the information previously given in Trace Elements Investigations Report 325, "Numerical list of U.S. Geological Survey Trace Elements Reports to April 30, 1953," and Trace Elements Investigations Report 301, "Topical index and bibliography of U.S. Geological Survey Trace Elements and related reports." Part I is a numerical list of U.S. Geological Survey Trace Elements Investigations and Memorandum reports. It supersedes TEI-325. This part lists not only reports (followed by a date) that have been transmitted to the U.S. Atomic Energy Commission, but also reports in preparation (followed by an asterisk) for which tentative titles were available on December 31, 1953. Reports that have been published are indicated by the abbreviation of the medium of publication. (See also part II.) Part II is a reference guide to Trace Elements and related reports that are available to the public; this part supersedes Part 2 of the TEI-301 (published as Geological survey Circular 281). These reports are grouped according to the type of publication or release. Abstracts published in Nuclear Science Abstracts are not included in Part II, although certain TEI and TEM reports, the abstracts of which have been published in NSA, are so indicated in Part I. Publications in process on December 31, 1953, are designated by an asterisk. Part III is a finding list of states, areas, and subjects. It is based on information derived mostly from the titles of reports and, where titles are of a general nature, from a cursory review of the reports. This list is not a complete index of the information given in Trace Elements and related reports, but is designed to find subjects of major interest. Because of the numerous entries for Colorado and Utah, information has been listed by counties and, where possible, by subject under these states. Other states have county listings only if a county is included in the title of a report; otherwise, areas may be listed

  7. The solar system/interstellar medium connection - Gas phase abundances

    NASA Technical Reports Server (NTRS)

    Lutz, Barry L.

    1987-01-01

    Gas-phase abundances in the outer solar system are presented as diagnostics of the interstellar medium at the time of the solar system formation, some 4.55 billion years ago. Possible influences of the thermal and chemical histories of the primitive solar nebula and of the processes which led to the formation and evolution of the outer planets and comets on the elemental and molecular composition of the primordial matter are outlined. The major components of the atmospheres of the outer planets and of the comae of comets are identified, and the cosmogonical and cosmological implications are discussed.

  8. Selfish genetic elements and the gene’s-eye view of evolution

    PubMed Central

    2016-01-01

    During the last few decades, we have seen an explosion in the influx of details about the biology of selfish genetic elements. Ever since the early days of the field, the gene’s-eye view of Richard Dawkins, George Williams, and others, has been instrumental to make sense of new empirical observations and to the generation of new hypotheses. However, the close association between selfish genetic elements and the gene’s-eye view has not been without critics and several other conceptual frameworks have been suggested. In particular, proponents of multilevel selection models have used selfish genetic elements to criticize the gene’s-eye view. In this paper, I first trace the intertwined histories of the study of selfish genetic elements and the gene’s-eye view and then discuss how their association holds up when compared with other proposed frameworks. Next, using examples from transposable elements and the major transitions, I argue that different models highlight separate aspects of the evolution of selfish genetic elements and that the productive way forward is to maintain a plurality of perspectives. Finally, I discuss how the empirical study of selfish genetic elements has implications for other conceptual issues associated with the gene’s-eye view, such as agential thinking, adaptationism, and the role of fitness maximizing models in evolution. PMID:29491953

  9. Near-Ultraviolet Observations of CS 29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes

    NASA Astrophysics Data System (ADS)

    Ivans, Inese I.; Sneden, Christopher; Gallino, Roberto; Cowan, John J.; Preston, George W.

    2005-07-01

    Employing spectra obtained with the new Keck I HIRES near-UV-sensitive detector, we have performed a comprehensive chemical composition analysis of the binary blue metal-poor star CS 29497-030. Abundances for 29 elements and upper limits for an additional seven have been derived, concentrating on elements largely produced by means of neutron-capture nucleosynthesis. Included in our analysis are the two elements that define the termination point of the slow neutron-capture process, lead and bismuth. We determine an extremely high value of [Pb/Fe]=+3.65+/-0.07 (σ=0.13) from three features, supporting the single-feature result obtained in previous studies. We detect Bi for the first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with those predicted from the most recent FRANEC calculations of the slow neutron-capture process in low-mass asymptotic giant branch (AGB) stars. We find that the neutron-capture elemental abundances of CS 29497-030 are best explained by an AGB model that also includes very significant amounts of pre-enrichment of rapid neutron-capture process material in the protostellar cloud out of which the CS 29497-030 binary system formed. Mass transfer is consistent with the observed [Nb/Zr]~0. Thus, CS 29497-030 is both an r+s and ``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can be further constrained by the abundance of the light odd-element Na. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  10. Dust formation in a galaxy with primitive abundances.

    PubMed

    Sloan, G C; Matsuura, M; Zijlstra, A A; Lagadec, E; Groenewegen, M A T; Wood, P R; Szyszka, C; Bernard-Salas, J; van Loon, J Th

    2009-01-16

    Interstellar dust plays a crucial role in the evolution of galaxies. It governs the chemistry and physics of the interstellar medium. In the local universe, dust forms primarily in the ejecta from stars, but its composition and origin in galaxies at very early times remain controversial. We report observational evidence of dust forming around a carbon star in a nearby galaxy with a low abundance of heavy elements, 25 times lower than the solar abundance. The production of dust by a carbon star in a galaxy with such primitive abundances raises the possibility that carbon stars contributed carbonaceous dust in the early universe.

  11. Highly siderophile elements in chondrites

    USGS Publications Warehouse

    Horan, M.F.; Walker, R.J.; Morgan, J.W.; Grossman, J.N.; Rubin, A.E.

    2003-01-01

    The abundances of the highly siderophile elements (HSE), Re, Os, Ir, Ru, Pt and Pd, were determined by isotope dilution mass spectrometry for bulk samples of 13 carbonaceous chondrites, 13 ordinary chondrites and 9 enstatite chondrites. These data are coupled with corresponding 187Re-187Os isotopic data reported by Walker et al. [Geochim. Cosmochim. Acta, 2002] in order to constrain the nature and timing of chemical fractionation relating to these elements in the early solar system. The suite of chondrites examined displays considerable variations in absolute abundances of the HSE, and in the ratios of certain HSE. Absolute abundances of the HSE vary by nearly a factor of 80 among the chondrite groups, although most vary within a factor of only 2. Variations in concentration largely reflect heterogeneities in the sample aliquants. Different aliquants of the same chondrite may contain variable proportions of metal and/or refractory inclusions that are HSE-rich, and sulfides that are HSE-poor. The relatively low concentrations of the HSE in CI1 chondrites likely reflect dilution by the presence of volatile components. Carbonaceous chondrites have Re/Os ratios that are, on average, approximately 8% lower than ratios for ordinary and enstatite chondrites. This is also reflected in 187Os/188Os ratios that are approximately 3% lower for carbonaceous chondrites than for ordinary and enstatite chondrites. Given the similarly refractory natures of Re and Os, this fractionation may have occurred within a narrow range of high temperatures, during condensation of these elements from the solar nebula. Superimposed on this major fractionation are more modest movements of Re or Os that occurred within the last 0-2 Ga, as indicated by minor open-system behavior of the Re-Os isotope systematics of some chondrites. The relative abundances of other HSE can also be used to discriminate among the major classes of chondrites. For example, in comparison to the enstatite chondrites

  12. Sensitivity of the s-process nucleosynthesis in AGB stars to the overshoot model

    NASA Astrophysics Data System (ADS)

    Goriely, S.; Siess, L.

    2018-01-01

    Context. S-process elements are observed at the surface of low- and intermediate-mass stars. These observations can be explained empirically by the so-called partial mixing of protons scenario leading to the incomplete operation of the CN cycle and a significant primary production of the neutron source. This scenario has been successful in qualitatively explaining the s-process enrichment in AGB stars. Even so, it remains difficult to describe both physically and numerically the mixing mechanisms taking place at the time of the third dredged-up between the convective envelope and the underlying C-rich radiative layer Aims: We aim to present new calculations of the s-process nucleosynthesis in AGB stars testing two different numerical implementations of chemical transport. These are based on a diffusion equation which depends on the second derivative of the composition and on a numerical algorithm where the transport of species depends linearly on the chemical gradient. Methods: The s-process nucleosynthesis resulting from these different mixing schemes is calculated with our stellar evolution code STAREVOL which has been upgraded to include an extended s-process network of 411 nuclei. Our investigation focuses on a fiducial 2 M⊙, [Fe/H] = -0.5 model star, but also includes four additional stars of different masses and metallicities. Results: We show that for the same set of parameters, the linear mixing approach produces a much larger 13C-pocket and consequently a substantially higher surface s-process enrichment compared to the diffusive prescription. Within the diffusive model, a quite extreme choice of parameters is required to account for surface s-process enrichment of 1-2 dex. These extreme conditions can not, however, be excluded at this stage. Conclusions: Both the diffusive and linear prescriptions of the overshoot mixing are suited to describe the s-process nucleosynthesis in AGB stars provided the profile of the diffusion coefficient below the

  13. Light element production in the big bang and the synthesis of heavy elements in 3D MHD jets from core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Winteler, Christian

    2014-02-01

    In this dissertation we present the main features of a new nuclear reaction network evolution code. This new code allows nucleosynthesis calculations for large numbers of nuclides. The main results in this dissertation are all obtained using this new code. The strength of standard big bang nucleosynthesis is, that all primordial abundances are determined by only one free parameter, the baryon-to-photon ratio η. We perform self consistent nucleosynthesis calculations for the latest WMAP value η = (6.16±0.15)×10^-10 . We predict primordial light element abundances: D/H = (2.84 ± 0.23)×10^-5, 3He/H = (1.07 ± 0.09)×10^-5, Yp = 0.2490±0.0005 and 7Li/H = (4.57 ± 0.55)×10^-10, in agreement with current observations and other predictions. We investigate the influence of the main production rate on the 6 Li abundance, but find no significant increase of the predicted value, which is known to be orders of magnitude lower than the observed. The r-process is responsible for the formation of about half of the elements heavier than iron in our solar system. This neutron capture process requires explosive environments with large neutron densities. The exact astrophysical site where the r-process occurs has not yet been identified. We explore jets from magnetorotational core collapse supernovae (MHD jets) as possible r-process site. In a parametric study, assuming adiabatic expansion, we find good agreement with solar system abundances for a superposition of components with different electron fraction (Ye ), ranging from Ye = 0.1 to Ye = 0.3. Fission is found to be important only for Ye ≤ 0.17. The first postprocessing calculations with data from 3D MHD core collapse supernova simulations are performed for two different simulations. Calculations are based on two different methods to extract data from the simulation: tracer particles and a two dimensional, mass weighted histogram. Both results yield almost identical results. We find that both simulations can

  14. Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

    USGS Publications Warehouse

    Coplen, T.B.; Hopple, J.A.; Böhlke, J.K.; Peiser, H.S.; Rieder, S.E.; Krouse, H.R.; Rosman, K.J.R.; Ding, T.; Vocke, R.D.; Revesz, K.M.; Lamberty, A.; Taylor, P.; De Bievre, P.

    2002-01-01

    Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope abundance variations potentially are large enough to result in future expansion of their atomic weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope-abundance variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio. There are no internationally distributed isotopic reference materials for the elements zinc, selenium, molybdenum, palladium, and tellurium. Preparation of such materials will help to make isotope ratio measurements among

  15. Distribution, movement, and evolution of the volatile elements in the lunar regolith

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.

    1975-01-01

    The abundances and distributions of carbon, nitrogen, and sulfur in lunar soils are reviewed. Carbon and nitrogen have a predominantly extra-lunar origin in lunar soils and breccias, while sulfur is mostly indigeneous to the moon. The lunar processes which effect the movement, distribution, and evolution of carbon, nitrogen, and sulfur, along with the volatile alkali elements sodium, potassium, and rubidium during regolith processes are discussed. Possible mechanisms which may result in the addition to or loss from the moon of these volatile elements are considered.

  16. A Review of Stellar Abundance Databases and the Hypatia Catalog Database

    NASA Astrophysics Data System (ADS)

    Hinkel, Natalie Rose

    2018-01-01

    The astronomical community is interested in elements from lithium to thorium, from solar twins to peculiarities of stellar evolution, because they give insight into different regimes of star formation and evolution. However, while some trends between elements and other stellar or planetary properties are well known, many other trends are not as obvious and are a point of conflict. For example, stars that host giant planets are found to be consistently enriched in iron, but the same cannot be definitively said for any other element. Therefore, it is time to take advantage of large stellar abundance databases in order to better understand not only the large-scale patterns, but also the more subtle, small-scale trends within the data.In this overview to the special session, I will present a review of large stellar abundance databases that are both currently available (i.e. RAVE, APOGEE) and those that will soon be online (i.e. Gaia-ESO, GALAH). Additionally, I will discuss the Hypatia Catalog Database (www.hypatiacatalog.com) -- which includes abundances from individual literature sources that observed stars within 150pc. The Hypatia Catalog currently contains 72 elements as measured within ~6000 stars, with a total of ~240,000 unique abundance determinations. The online database offers a variety of solar normalizations, stellar properties, and planetary properties (where applicable) that can all be viewed through multiple interactive plotting interfaces as well as in a tabular format. By analyzing stellar abundances for large populations of stars and from a variety of different perspectives, a wealth of information can be revealed on both large and small scales.

  17. Dust, Abundances, and the Evolution of Novae

    NASA Astrophysics Data System (ADS)

    Woodward, Charles; Bode, Michael; Evans, Anuerin; Geballe, Thomas; Gehrz, Robert; Helton, Andrew; Krautter, Joachim; Lynch, David; Ness, Jan-Uwe; Rudy, Richard; Schwarz, Greg; Shore, Steve; Starrfield, Sumner; Truran, James; Vanlandingham, Karen; Wagner, R. Mark

    2008-03-01

    Evolved stars are the engines of energy production and chemical evolution in our Universe. They deposit radiative and mechanical energy into their environments. They enrich the ambient ISM with elements synthesized in their interiors and dust grains condensed in their atmospheres. Classical novae (CNe) contribute to this cycle of chemical enrichment through explosive nucleosynthesis and the violent ejection of material dredged from the white dwarf progenitor and mixed with the accreted surface layers. Our capstone study of 10 CNe will provide an ensemble of objects, well-populated in CNe parameter space (fast, slow, 'coronal', dusty) for detailed photoionization modeling and analysis. CNe are laboratories in which several poorly-understood astrophysical processes (e.g., mass transfer, thermonuclear runaway, optically thick winds, common envelope evolution, molecule and grain formation, coronal emission) may be observed. With Spitzer's unique wavelength coverage and point-source sensitivity we can: (i) investigate the in situ formation, astromineralogy, and processing of nova dust, (ii) determine the ejecta elemental abundances resulting from thermonuclear runaway, (iii) constrain the correlation of ejecta mass with progenitor type, (iv) measure the bolometric luminosity of the outburst, and (v) characterize the kinematics and structure of the ejected envelopes. Extensive ground-based and space-based (Chandra, Swift, XMM-Newton) programs led by team CoIs will complement Spitzer CNe observations.

  18. Geochemistry of rare earth elements in Permian coals from the Huaibei Coalfield, China

    USGS Publications Warehouse

    Zheng, Lingyun; Liu, Gaisheng; Chou, C.-L.; Qi, C.; Zhang, Y.

    2007-01-01

    The rare earth elements (REEs) in coals are important because of: (a) REE patterns can be an indicator of the nature of source rocks of the mineral matter as well as sedimentary environments; (b) REEs abundance in coal may have industrial-significance. In this study, a total of thirty-four samples of Permian coal, partings, roof, and floor were collected from the Huaibei Coalfield, Anhui Province, China. Abundances of rare earth elements (REEs) and other elements in the samples were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and inductively coupled-plasma atomic emission spectrometry (ICP-AES). The results show that the REEs are enriched in coals in the Huaibei Coalfield as compared with Chinese and U.S. coals and the world coal average. Coals in the Lower Shihezi Formation (No. 7, 5, and 4 Coals) and Upper Shihezi Formation (No. 3) have higher REE abundances than the coals in Shanxi Formation (No. 10). Magmatic intrusion resulted in high enrichment of REEs concentrations in No. 5 and 7 Coals. The REE abundances are positively correlated with the ash content. The mineral matter in these coals is mainly made up of clay minerals and carbonates. The REEs are positively correlated with lithophile elements including Si, Al, Ti, Fe, and Na, which are mainly distributed in clay minerals, indicating that REEs are contained mainly in clay minerals. The REE abundances in coals normalized by the ash are higher than that in partings. REEs abundances of coals cannot be accounted for by the REE content in the mineral matter, and some REEs associated with organic matter in coals. ?? 2007 Elsevier Ltd. All rights reserved.

  19. Spiral stellar density waves and the flattening of abundance gradients in the warm gas component of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Vorobyov, E. I.

    2006-08-01

    Motivated by recent observations of plateaus and minima in the radial abundance distributions of heavy elements in the Milky Way and some other spiral galaxies, we propose a dynamical mechanism for the formation of such features around corotation. Our numerical simulations show that the non-axisymmetric gravitational field of spiral density waves generates cyclone and anticylone gas flows in the vicinity of corotation. The anticyclones flatten the pre-existing negative abundance gradients by exporting many more atoms of heavy elements outside corotation than importing inside it. This process is very efficient and forms plateaus of several kiloparsec in size around corotation after two revolution periods of a galaxy. The strength of anticyclones and, consequently, the sizes of plateaus depend on the pitch angle of spiral arms and are expected to increase along the Hubble sequence.

  20. Monitoring Butterfly Abundance: Beyond Pollard Walks

    PubMed Central

    Pellet, Jérôme; Bried, Jason T.; Parietti, David; Gander, Antoine; Heer, Patrick O.; Cherix, Daniel; Arlettaz, Raphaël

    2012-01-01

    Most butterfly monitoring protocols rely on counts along transects (Pollard walks) to generate species abundance indices and track population trends. It is still too often ignored that a population count results from two processes: the biological process (true abundance) and the statistical process (our ability to properly quantify abundance). Because individual detectability tends to vary in space (e.g., among sites) and time (e.g., among years), it remains unclear whether index counts truly reflect population sizes and trends. This study compares capture-mark-recapture (absolute abundance) and count-index (relative abundance) monitoring methods in three species (Maculinea nausithous and Iolana iolas: Lycaenidae; Minois dryas: Satyridae) in contrasted habitat types. We demonstrate that intraspecific variability in individual detectability under standard monitoring conditions is probably the rule rather than the exception, which questions the reliability of count-based indices to estimate and compare specific population abundance. Our results suggest that the accuracy of count-based methods depends heavily on the ecology and behavior of the target species, as well as on the type of habitat in which surveys take place. Monitoring programs designed to assess the abundance and trends in butterfly populations should incorporate a measure of detectability. We discuss the relative advantages and inconveniences of current monitoring methods and analytical approaches with respect to the characteristics of the species under scrutiny and resources availability. PMID:22859980

  1. Whole body-element composition of Atlantic salmon Salmo salar influenced by migration direction and life stage in three distinct populations.

    PubMed

    Ebel, J D; Leroux, S J; Robertson, M J; Dempson, J B

    2016-11-01

    Body-element content was measured for three life stages of wild Atlantic salmon Salmo salar from three distinct Newfoundland populations as individuals crossed between freshwater and marine ecosystems. Life stage explained most of the variation in observed body-element concentration whereas river of capture explained very little variation. Element composition of downstream migrating post-spawn adults (i.e. kelts) and juvenile smolts were similar and the composition of these two life stages strongly differed from adults migrating upstream to spawn. Low variation within life stages and across populations suggests that S. salar may exert rheostatic control of their body-element composition. Additionally, observed differences in trace element concentration between adults and other life stages were probably driven by the high carbon concentration in adults because abundant elements, such as carbon, can strongly influence the observed concentrations of less abundant elements. Thus, understanding variation among individuals in trace elements composition requires the measurement of more abundant elements. Changes in element concentration with ontogeny have important consequences the role of fishes in ecosystem nutrient cycling and should receive further attention. © 2016 The Fisheries Society of the British Isles.

  2. IUE/IRAS studies of metal abundances and infrared cirrus

    NASA Technical Reports Server (NTRS)

    Vansteenberg, M. E.; Shull, J. M.

    1986-01-01

    A survey is reported of interstellar densities, abundances, and cloud structure in the Galaxy, using the IUE and IRAS satellites. Heavy element depletions are discussed along with their correlations with mean density, reddening, and galactic location. Interesting correlations between the Fe/Si abundance ratio and the infrared diffuse cirrus is also reported, which may provide information on the history and formation of grains in the galactic halo.

  3. Roadside Accumulation of Pt, Pd, Rh and Other Trace Elements From Automobiles: Catalytic Converter Attrition and Platinum-Group Element Mobility in the Roadside Environment.

    NASA Astrophysics Data System (ADS)

    Ely, J. C.; Dahlheimer, S. R.; Neal, C. R.

    2003-12-01

    Elemental abundances of Pt, Pd and Rh have been documented across the industrialized world in roadside environments due to attrition of automotive catalytic converters (Zereini and Alt, 2000, Anthropogenic PGE Emissions, Springer, 308pp; Ely et al., 2001, EnvSci&Tech, 35:3816-3822; Whiteley and Murray, 2003, SciTotEnv, in press). In our ongoing study, the highest reported roadside Pt abundance 1.8 ppm has been found immediately adjacent to the road at a field site in South Bend, IN, USA. Furthermore, initial studies show positive correlations of Pt, Pd and Rh with some trace elements (Ni, Cu, Zn and Pb), which has been confirmed by further analysis for these and other elements (Ce, Cr). It has been demonstrated that elements such as Ce are present in catalytic converters at concentrations of 100's ppm to 3-wt.%. These elements are also being attrited with Pt, Pd and Rh and aerially transported and deposited. Our field site was established next to US-933 adjacent to the Notre Dame campus. Areas were cleared of the top 2-4 cm of soil (removing surficial Pt, Pd and Rh) at 1, 5, 10 and 50 meters from the roadside. Within 3 months the 1-meter site contained 67% of the initial Rh and Pt concentrations and 100% of the initial Pd concentration. The sites at 5, 10 and 50 meters showed similar results, in some cases exceeding the initial concentrations. After 6 months the concentrations of Pt, Pd and Rh were all within error of the initial concentrations, indicating steady state abundances had probably been reached. Grass samples from each site showed that washed vs. unwashed samples were within error of each other, and there may be a slight enrichment (approx. 1 ppb) in the grasses of Pd and Pt, but this enrichment was independent of distance from the road. The steady-state situation suggests that the PGEs are being removed from the immediate roadside environment, which requires that the metals are being oxidized and/or complexed in such a way to facilitate transport. The

  4. An r-process enhanced star in the dwarf galaxy Tucana III

    DOE PAGES

    Hansen, T. T.; Simon, J. D.; Marshall, J. L.; ...

    2017-03-20

    Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66–593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-Imore » star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. Furthermore, we explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.« less

  5. An r-process enhanced star in the dwarf galaxy Tucana III

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hansen, T. T.; Simon, J. D.; Marshall, J. L.

    Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66–593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-Imore » star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. Furthermore, we explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.« less

  6. Processing of metal and oxygen from lunar deposits

    NASA Technical Reports Server (NTRS)

    Acton, Constance F.

    1992-01-01

    On the moon, some whole rocks may be ores for abundant elements, such as oxygen, but beneficiation will be important if metallic elements are sought from raw lunar dirt. In the extraction process, a beneficiated metallic ore, such as an oxide, sulfide, carbonate, or silicate mineral, is converted to reduced metal. A variety of plausible processing technologies, which includes recovery of meteoritic iron, and processing of lunar ilmenite, are described in this report.

  7. Process for synthesizing compounds from elemental powders and product

    DOEpatents

    Rabin, Barry H.; Wright, Richard N.

    1993-01-01

    A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe.sub.3 Al and FeAl.

  8. Energetic-particle abundances in impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Cane, H. V.; Von Rosenvinge, T. T.

    1990-01-01

    The abundances of elements and of He-3 in 90 solar electron events have been examined. It is found that the events fall into two distinct groups based upon their F/C ratio. Events in the F-rich group frequently have high He-3/He-4 ratios and are associated with type III and type V radio bursts in the parent flare. The F-poor events are associated with type IV bursts. These results on individual events support the conclusions of earlier work done with daily-averaged abundances.

  9. Elemental fingerprints of isotopic contamination of hebridean Palaeocene mantle-derived magmas by archaean sial

    NASA Astrophysics Data System (ADS)

    Thompson, R. N.; Dickin, A. P.; Gibson, I. L.; Morrison, M. A.

    1982-06-01

    One of the major puzzles presented by the geochemistry of the Palaeocene plateau lavas of Skye and Mull (N.W. Scotland) is that, although a very strong case can be made that the magmas are variably isotopically contaminated by Archaean Lewisian continental crust, little evidence has been gleaned to date from their major- and trace-element compositions to illuminate this hypothetical process. The combined results of published Sr-, Nd- and Pb-isotope studies of these lavas allow the basalts and hawaiites to be divided into three broad groups: essentially uncontaminated; contaminated with granulite-facies Archaean crust; contaminated with amphibolite-facies Archaean crust. Members of each group show distinctive chondrite-normalised incompatible-element patterns. The processes which gave rise to isotopic contamination of these lavas also affected the abundances and ratios of Ba, Rb, Th, K, Sr and light REE in the magmas, whilst having negligible effects on their abundances and ratios of Nb, Ta, P, Zr, Hf, Ti, Y and middle-heavy REE. Because such a wide range of elements were affected by the contamination process, it is postulated that the contaminant was a silicate melt of one or more distinctive crustal rock types, rather than an aqueous or similar fluid causing selective elemental movements from wall rocks into the magmas. As previous experimental and isotopic studies have shown that the Skye and Mull basic magmas were not constrained by cotectic equilibria at the time when they interacted with sial, the compositions of the contaminated lavas have been modelled in terms of simple magma-crust mixtures. Very close approximations to both the abundances and ratios of incompatible elements in the two groups of contaminated basalts may be obtained by adding 15% to 20% of Lewisian leucogneisses to uncontaminated Palaeocene basalt. Nevertheless, major-element constraints suggest that the maximum amount of granitic contaminant which has been added to these magmas lies between

  10. A mobile element in mutS drives hypermutation in a marine Vibrio

    DOE PAGES

    Chu, Nathaniel D.; Clarke, Sean A.; Timberlake, Sonia; ...

    2017-02-07

    Bacteria face a trade-off between genetic fidelity, which reduces deleterious mistakes in the genome, and genetic innovation, which allows organisms to adapt. Evidence suggests that many bacteria balance this trade-off by modulating their mutation rates, but few mechanisms have been described for such modulation. Following experimental evolution and whole-genome resequencing of the marine bacterium Vibrio splendidus 12B01, we discovered one such mechanism, which allows this bacterium to switch to an elevated mutation rate. This switch is driven by the excision of a mobile element residing in mutS, which encodes a DNA mismatch repair protein. When integrated within the bacterial genome,more » the mobile element provides independent promoter and translation start sequences for mutS—different from the bacterium’s original mutS promoter region—which allow the bacterium to make a functional mutS gene product. Excision of this mobile element rejoins the mutS gene with host promoter and translation start sequences but leaves a 2-bp deletion in the mutS sequence, resulting in a frameshift and a hypermutator phenotype. We further identified hundreds of clinical and environmental bacteria across Betaproteobacteria and Gammaproteobacteria that possess putative mobile elements within the same amino acid motif in mutS. In a subset of these bacteria, we detected excision of the element but not a frameshift mutation; the mobile elements leave an intact mutS coding sequence after excision. Finally, our findings reveal a novel mechanism by which one bacterium alters its mutation rate and hint at a possible evolutionary role for mobile elements within mutS in other bacteria.« less

  11. A Mobile Element in mutS Drives Hypermutation in a Marine Vibrio

    PubMed Central

    Chu, Nathaniel D.; Clarke, Sean A.; Timberlake, Sonia; Polz, Martin F.; Grossman, Alan D.

    2017-01-01

    ABSTRACT Bacteria face a trade-off between genetic fidelity, which reduces deleterious mistakes in the genome, and genetic innovation, which allows organisms to adapt. Evidence suggests that many bacteria balance this trade-off by modulating their mutation rates, but few mechanisms have been described for such modulation. Following experimental evolution and whole-genome resequencing of the marine bacterium Vibrio splendidus 12B01, we discovered one such mechanism, which allows this bacterium to switch to an elevated mutation rate. This switch is driven by the excision of a mobile element residing in mutS, which encodes a DNA mismatch repair protein. When integrated within the bacterial genome, the mobile element provides independent promoter and translation start sequences for mutS—different from the bacterium’s original mutS promoter region—which allow the bacterium to make a functional mutS gene product. Excision of this mobile element rejoins the mutS gene with host promoter and translation start sequences but leaves a 2-bp deletion in the mutS sequence, resulting in a frameshift and a hypermutator phenotype. We further identified hundreds of clinical and environmental bacteria across Betaproteobacteria and Gammaproteobacteria that possess putative mobile elements within the same amino acid motif in mutS. In a subset of these bacteria, we detected excision of the element but not a frameshift mutation; the mobile elements leave an intact mutS coding sequence after excision. Our findings reveal a novel mechanism by which one bacterium alters its mutation rate and hint at a possible evolutionary role for mobile elements within mutS in other bacteria. PMID:28174306

  12. A mobile element in mutS drives hypermutation in a marine Vibrio

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chu, Nathaniel D.; Clarke, Sean A.; Timberlake, Sonia

    Bacteria face a trade-off between genetic fidelity, which reduces deleterious mistakes in the genome, and genetic innovation, which allows organisms to adapt. Evidence suggests that many bacteria balance this trade-off by modulating their mutation rates, but few mechanisms have been described for such modulation. Following experimental evolution and whole-genome resequencing of the marine bacterium Vibrio splendidus 12B01, we discovered one such mechanism, which allows this bacterium to switch to an elevated mutation rate. This switch is driven by the excision of a mobile element residing in mutS, which encodes a DNA mismatch repair protein. When integrated within the bacterial genome,more » the mobile element provides independent promoter and translation start sequences for mutS—different from the bacterium’s original mutS promoter region—which allow the bacterium to make a functional mutS gene product. Excision of this mobile element rejoins the mutS gene with host promoter and translation start sequences but leaves a 2-bp deletion in the mutS sequence, resulting in a frameshift and a hypermutator phenotype. We further identified hundreds of clinical and environmental bacteria across Betaproteobacteria and Gammaproteobacteria that possess putative mobile elements within the same amino acid motif in mutS. In a subset of these bacteria, we detected excision of the element but not a frameshift mutation; the mobile elements leave an intact mutS coding sequence after excision. Finally, our findings reveal a novel mechanism by which one bacterium alters its mutation rate and hint at a possible evolutionary role for mobile elements within mutS in other bacteria.« less

  13. Geochemical maps showing the distribution and abundance of selected elements in nonmagnetic heavy-mineral-concentrate samples from stream sediment, Solomon and Bendelehen 1 degree by 3 degree Quadrangles , Seward Peninsula, Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    King, H.D.; Smith, S.C.; Sutley, S.J.

    Geochemical maps showing the distribution and abundance of selected elements in nonmagnetic heavy-mineral-concentrate samples from stream sediment, Solomon and Bendelehen 1{degree} by 3{degree} Quadrangles , Seward Peninsula, Alaska is presented.

  14. Cell abundance and microbial community composition along a complete oil sand mining and reclamation process

    NASA Astrophysics Data System (ADS)

    Lappé, M.; Schneider, B.; Kallmeyer, J.

    2012-12-01

    Hydrocarbons constitute an important energy source for microbes but can also be of environmental concern. Microbial activity causes hydrocarbon degradation and thereby loss of economical value, but also helps to remove hydrocarbons from the environment. The present study characterizes the abundance of microbes along the oil sand mining process in Alberta, Canada, as a first approach to assess the impact of mining and oil extraction on the microbial population. After mining the oil is extracted from the sediment by a hot-water extraction (50-60°C), resulting in three major fractions: crude oil, tailings sand and fine tailings. The tailings sand is used as substratum for newly developing soils on the reclamation areas. The very liquid fine tailings still have a TOC content of about 4.3% and are pumped into tailings ponds, where they need up to three decades to settle and solidify. After deposition, these mature fine tailings (MFTs) are enriched in organics (TOC content between 9.6 and 16.8%) and dredged out of the ponds and put on dumps for several years for dewatering. Finally they are brought out onto the reclamation sites and deposited below the sand layer. Cells were extracted from oily sediments according to the protocol of Lappé and Kallmeyer (2011), stained with SYBR Green I and counted by fluorescence microscopy. Cell abundance in the unprocessed oil sand is around 1.6 x 107 cells cm-3. After processing the fresh fine tailings still contain around 1.6 x 107 cells cm-3. Cell counts in the processed MFTs are 5.8 x 107 cells cm-3, whereas in the sand used as substratum for newly developing soils, they are twice as high (1.4 x 108). In root-bearing horizons, cell counts reach 1.1 x 109 cell cm-3. Cell numbers calculated from cultivation experiments are in the same range. Higher cell counts in the tailings sand are probably due to a higher nitrogen supply through the addition of a 35 cm top layer of a peat-mineral mix. In the sand nitrate concentrations are high

  15. Elemental gas-phase abundances of intermediate redshift type Ia supernova star-forming host galaxies

    NASA Astrophysics Data System (ADS)

    Moreno-Raya, M. E.; Galbany, L.; López-Sánchez, Á. R.; Mollá, M.; González-Gaitán, S.; Vílchez, J. M.; Carnero, A.

    2018-05-01

    The maximum luminosity of type Ia supernovae (SNe Ia) depends on the oxygen abundance of the regions of the host galaxies, where they explode. This metallicity dependence reduces the dispersion in the Hubble diagram (HD) when included with the traditional two-parameter calibration of SN Ia light-curve parameters and absolute magnitude. In this work, we use empirical calibrations to carefully estimate the oxygen abundance of galaxies hosting SNe Ia from the SDSS-II/SN (Sloan Digital Sky Survey-II Supernova) survey at intermediate redshift by measuring their emission-line intensities. We also derive electronic temperature with the direct method for a small fraction of objects for consistency. We find a trend of decreasing oxygen abundance with increasing redshift for the most massive galaxies. Moreover, we study the dependence of the HD residuals (HR) with galaxy oxygen abundance obtaining a correlation in line with those found in other works. In particular, the HR versus oxygen abundance shows a slope of -0.186 ± 0.123 mag dex-1 (1.52σ) in good agreement with theoretical expectations. This implies smaller distance modulii after corrections for SNe Ia in metal-rich galaxies. Based on our previous results on local SNe Ia, we propose this dependence to be due to the lower luminosity of the SNe Ia produced in more metal-rich environments.

  16. Deconfounding the effects of local element spatial heterogeneity and sparsity on processing dominance.

    PubMed

    Montoro, Pedro R; Luna, Dolores

    2009-10-01

    Previous studies on the processing of hierarchical patterns (Luna & Montoro, 2008) have shown that altering the spatial relationships between the local elements affected processing dominance by decreasing global advantage. In the present article, the authors examine whether heterogeneity or a sparse distribution of the local elements was the responsible factor for this effect. In Experiments 1 and 2, the distance between the local elements was increased in a similar way, but between-element distance was homogeneous in Experiment 1 and heterogeneous in Experiment 2. In Experiment 3, local elements' size was varied by presenting global patterns composed of similar large or small local elements and of different large and small sizes. The results of the present research showed that, instead of element sparsity, spatial heterogeneity that could change the appearance of the global form as well as the salience of the local elements was the main determiner of impairing global processing.

  17. The abundance of interstellar sulphur and zinc in high density sight-lines

    NASA Technical Reports Server (NTRS)

    Harris, A. W.; Mashesse, J. M.

    1986-01-01

    On the basis of early absorption line studies of individual lines of sight with the Copernicus satellite, chlorine, sulphur and zinc were classed together as elements which showed little or no depletion, relative to hydrogen, in the interstellar medium. The abundances of other less volatile elements, such as Fe and Mg were found to vary widely from one sight-line to another with gas-phase abundances in some cases being orders of magnitude below their solar counterparts. Detailed studies are reported of the depletion/density behavior of two other volatile elements which were previously considered to be virtually undepleted, S and Zn, using equivalent width data from both Copernicus and IUE observations. The results provide further evidence that the established dependence of depletion on n bar (H) extends to volatile elements and show that their use as tracers of metallicity, or for estimating hydrogen column densities, may lead to large errors in sight-lines through dense regions. It now appears that such elements may take part in the surface chemistry of grains and be important constituents of grain mantle material, although they probably do not contribute significantly to the bulk mass of grains. Due to the very similar atomic masses and ionization potentials of sulphur and phosphorous, the thermal velocity distributions of the singly ionized species of these elements in interstellar clouds should be very similar. However, a comparison of Doppler widths (b-values) derived for SIT and PIT in the same sight-lines from the Bohlin et al Copernicus equivalent width measurements has revealed an unexpected systematic discrepancy of a factor of approx. 1.7. This Discrepancy indicates that the normally adopted oscillators strengths of the PII lambda lambda 1153 and 1302 A lines may require revision.

  18. Rare earth element scavenging in seawater

    NASA Astrophysics Data System (ADS)

    Byrne, Robert H.; Kim, Ki-Hyun

    1990-10-01

    Examinations of rare earth element (REE) adsorption in seawater, using a variety of surface-types, indicated that, for most surfaces, light rare earth elements (LREEs) are preferentially adsorbed compared to the heavy rare earths (HREEs). Exceptions to this behavior were observed only for silica phases (glass surfaces, acid-cleaned diatomaceous earth, and synthetic SiO 2). The affinity of the rare earths for surfaces can be strongly affected by thin organic coatings. Glass surfaces which acquired an organic coating through immersion in Tampa Bay exhibited adsorptive behavior typical of organic-rich, rather than glass, surfaces. Models of rare earth distributions between seawater and carboxylate-rich surfaces indicate that scavenging processes which involve such surfaces should exhibit a strong dependence on pH and carbonate complexation. Scavenging models involving carboxylate surfaces produce relative REE abundance patterns in good general agreement with observed shale-normalized REE abundances in seawater. Scavenging by carboxylate-rich surfaces should produce HREE enrichments in seawater relative to the LREEs and may produce enrichments of lanthanum relative to its immediate trivalent neighbors. Due to the origin of distribution coefficients as a difference between REE solution complexation (which increases strongly with atomic number) and surface complexation (which apparently also increases with atomic number) the relative solution abundance patterns of the REEs produced by scavenging reactions can be quite complex.

  19. Statistical γ -decay properties of 64Ni and deduced (n ,γ ) cross section of the s -process branch-point nucleus 63Ni

    NASA Astrophysics Data System (ADS)

    Crespo Campo, L.; Bello Garrote, F. L.; Eriksen, T. K.; Görgen, A.; Guttormsen, M.; Hadynska-Klek, K.; Klintefjord, M.; Larsen, A. C.; Renstrøm, T.; Sahin, E.; Siem, S.; Springer, A.; Tornyi, T. G.; Tveten, G. M.

    2016-10-01

    Particle-γ coincidence data have been analyzed to obtain the nuclear level density and the γ -strength function of 64Ni by means of the Oslo method. The level density found in this work is in very good agreement with known energy levels at low excitation energies as well as with data deduced from particle-evaporation measurements at excitation energies above Ex≈5.5 MeV. The experimental γ -strength function presents an enhancement at γ energies below Eγ≈3 MeV and possibly a resonancelike structure centered at Eγ≈9.2 MeV. The obtained nuclear level density and γ -strength function have been used to estimate the (n ,γ ) cross section for the s -process branch-point nucleus 63Ni, of particular interest for astrophysical calculations of elemental abundances.

  20. Photoelectric absorption cross sections with variable abundances

    NASA Technical Reports Server (NTRS)

    Balucinska-Church, Monika; Mccammon, Dan

    1992-01-01

    Polynomial fit coefficients have been obtained for the energy dependences of the photoelectric absorption cross sections of 17 astrophysically important elements. These results allow the calculation of X-ray absorption in the energy range 0.03-10 keV in material with noncosmic abundances.

  1. 47 CFR 69.119 - Basic service element expedited approval process.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Basic service element expedited approval process. 69.119 Section 69.119 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Computation of Charges § 69.119 Basic service element...

  2. Evidence of enrichment by individual SN from elemental abundance ratios in the very metal-poor dSph galaxy Boötes I

    NASA Astrophysics Data System (ADS)

    Feltzing, S.; Eriksson, K.; Kleyna, J.; Wilkinson, M. I.

    2009-12-01

    Aims. We establish the mean metallicity from high-resolution spectroscopy for the recently found dwarf spheroidal galaxy Boötes I and test whether it is a common feature for ultra-faint dwarf spheroidal galaxies to show signs of inhomogeneous chemical evolution (e.g. as found in the Hercules dwarf spheroidal galaxy). Methods: We analyse high-resolution, moderate signal-to-noise spectra for seven red giant stars in the Boötes I dSph galaxy using standard abundance analysis techniques. In particular, we assume local thermodynamic equilibrium and employ spherical model atmospheres and codes that take the sphericity of the star into account when calculating the elemental abundances. Results: We confirm previous determinations of the mean metallicity of the Boötes I dwarf spheroidal galaxy to be -2.3 dex. Whilst five stars are clustered around this metallicity, one is significantly more metal-poor, at -2.9 dex, and one is more metal-rich at, -1.9 dex. Additionally, we find that one of the stars, Boo-127, shows an atypically high [Mg/Ca] ratio, indicative of stochastic enrichment processes within the dSph galaxy. Similar results have previously only been found in the Hercules and Draco dSph galaxies and appear, so far, to be unique to this type of galaxy. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  3. Finite Element Modelling and Analysis of Conventional Pultrusion Processes

    NASA Astrophysics Data System (ADS)

    Akishin, P.; Barkanov, E.; Bondarchuk, A.

    2015-11-01

    Pultrusion is one of many composite manufacturing techniques and one of the most efficient methods for producing fiber reinforced polymer composite parts with a constant cross-section. Numerical simulation is helpful for understanding the manufacturing process and developing scientific means for the pultrusion tooling design. Numerical technique based on the finite element method has been developed for the simulation of pultrusion processes. It uses the general purpose finite element software ANSYS Mechanical. It is shown that the developed technique predicts the temperature and cure profiles, which are in good agreement with those published in the open literature.

  4. PHOTOSPHERIC ABUNDANCES OF POLAR JETS ON THE SUN OBSERVED BY HINODE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Kyoung-Sun; Brooks, David H.; Imada, Shinsuke, E-mail: lksun@solar.isas.jaxa.jp

    2015-08-20

    Many jets are detected at X-ray wavelengths in the Sun's polar regions, and the ejected plasma along the jets has been suggested to contribute mass to the fast solar wind. From in situ measurements in the magnetosphere, it has been found that the fast solar wind has photospheric abundances while the slow solar wind has coronal abundances. Therefore, we investigated the abundances of polar jets to determine whether they are the same as that of the fast solar wind. For this study, we selected 22 jets in the polar region observed by Hinode/EUV Imaging Spectroscopy (EIS) and X-ray Telescope (XRT)more » simultaneously on 2007 November 1–3. We calculated the First Ionization Potential (FIP) bias factor from the ratio of the intensity between high (S) and low (Si, Fe) FIP elements using the EIS spectra. The values of the FIP bias factors for the polar jets are around 0.7–1.9, and 75% of the values are in the range of 0.7–1.5, which indicates that they have photospheric abundances similar to the fast solar wind. The results are consistent with the reconnection jet model where photospheric plasma emerges and is rapidly ejected into the fast wind.« less

  5. Planetary Nebula Abundances and Morphology: Probing the Chemical Evolution of the Milky Way

    NASA Astrophysics Data System (ADS)

    Stanghellini, Letizia; Guerrero, Martín Antonio; Cunha, Katia; Manchado, Arturo; Villaver, Eva

    2006-11-01

    This paper presents a homogeneous study of abundances in a sample of 79 northern Galactic planetary nebulae (PNe) whose morphological classes have been uniformly determined. Ionic abundances and plasma diagnostics were derived from selected optical line strengths in the literature, and elemental abundances were estimated with the ionization correction factor developed by Kingsbourgh & Barlow in 1994. We compare the elemental abundances to the final yields obtained from stellar evolution models of low- and intermediate-mass stars, and we confirm that most bipolar PNe have high nitrogen and helium abundance and are the likely progeny of stars with main-sequence mass greater than 3 Msolar. We derive =0.27 and discuss the implication of such a high ratio in connection with the solar neon abundance. We determine the Galactic gradients of oxygen and neon and found Δlog(O/H)/ΔR=-0.01 dex kpc-1 and Δlog(Ne/H)/ΔR=-0.01 dex kpc-1. These flat PN gradients are irreconcilable with Galactic metallicity gradients flattening with time.

  6. FAMA: An automatic code for stellar parameter and abundance determination

    NASA Astrophysics Data System (ADS)

    Magrini, Laura; Randich, Sofia; Friel, Eileen; Spina, Lorenzo; Jacobson, Heather; Cantat-Gaudin, Tristan; Donati, Paolo; Baglioni, Roberto; Maiorca, Enrico; Bragaglia, Angela; Sordo, Rosanna; Vallenari, Antonella

    2013-10-01

    Context. The large amount of spectra obtained during the epoch of extensive spectroscopic surveys of Galactic stars needs the development of automatic procedures to derive their atmospheric parameters and individual element abundances. Aims: Starting from the widely-used code MOOG by C. Sneden, we have developed a new procedure to determine atmospheric parameters and abundances in a fully automatic way. The code FAMA (Fast Automatic MOOG Analysis) is presented describing its approach to derive atmospheric stellar parameters and element abundances. The code, freely distributed, is written in Perl and can be used on different platforms. Methods: The aim of FAMA is to render the computation of the atmospheric parameters and abundances of a large number of stars using measurements of equivalent widths (EWs) as automatic and as independent of any subjective approach as possible. It is based on the simultaneous search for three equilibria: excitation equilibrium, ionization balance, and the relationship between log n(Fe i) and the reduced EWs. FAMA also evaluates the statistical errors on individual element abundances and errors due to the uncertainties in the stellar parameters. The convergence criteria are not fixed "a priori" but are based on the quality of the spectra. Results: In this paper we present tests performed on the solar spectrum EWs that assess the method's dependency on the initial parameters and we analyze a sample of stars observed in Galactic open and globular clusters. The current version of FAMA is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A38

  7. Ultra-Heavy Galactic Cosmic Ray Abundances from the SuperTIGER Instrument: evidence for an OB association origin of GCR

    NASA Astrophysics Data System (ADS)

    Murphy, Ryan; Supertiger Collaboration

    2017-01-01

    We report Galactic Cosmic Ray (GCR) abundances of elements from 26Fe to 40Zr measured by the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument during 55 days of exposure on a long-duration balloon flight over Antarctica. SuperTIGER measures charge (Z) and energy (E) using a combination of three scintillator and two Cherenkov detectors, and employs a scintillating fiber hodoscope for event trajectory determination. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. We also derived GCR source abundances, which support a model of cosmic-ray origin in which the source material consists of a mixture of 19-6+ 11 % material from massive stars and 81% normal interstellar medium (ISM) material with solar system abundances. The results also show a preferential acceleration, ordered by atomic mass (A), of refractory elements over volatile elements by a factor of 4. Both the refractory and volatile elements show a mass-dependent enhancement with similar mass dependence. (now AIP Congressional Science Fellow).

  8. HIGH PRECISION ABUNDANCES OF THE OLD SOLAR TWIN HIP 102152: INSIGHTS ON Li DEPLETION FROM THE OLDEST SUN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Monroe, TalaWanda R.; Melendez, Jorge; Tucci Maia, Marcelo

    2013-09-10

    We present the first detailed chemical abundance analysis of the old 8.2 Gyr solar twin, HIP 102152. We derive differential abundances of 21 elements relative to the Sun with precisions as high as 0.004 dex ({approx}<1%), using ultra high-resolution (R = 110,000), high S/N UVES spectra obtained on the 8.2 m Very Large Telescope. Our determined metallicity of HIP 102152 is [Fe/H] = -0.013 {+-} 0.004. The atmospheric parameters of the star were determined to be 54 K cooler than the Sun, 0.09 dex lower in surface gravity, and a microturbulence identical to our derived solar value. Elemental abundance ratiosmore » examined versus dust condensation temperature reveal a solar abundance pattern for this star, in contrast to most solar twins. The abundance pattern of HIP 102152 appears to be the most similar to solar of any known solar twin. Abundances of the younger, 2.9 Gyr solar twin, 18 Sco, were also determined from UVES spectra to serve as a comparison for HIP 102152. The solar chemical pattern of HIP 102152 makes it a potential candidate to host terrestrial planets, which is reinforced by the lack of giant planets in its terrestrial planet region. The following non-local thermodynamic equilibrium Li abundances were obtained for HIP 102152, 18 Sco, and the Sun: log {epsilon} (Li) = 0.48 {+-} 0.07, 1.62 {+-} 0.02, and 1.07 {+-} 0.02, respectively. The Li abundance of HIP 102152 is the lowest reported to date for a solar twin, and allows us to consider an emerging, tightly constrained Li-age trend for solar twin stars.« less

  9. Silicon to iron abundances in solar cosmic rays and in the sun

    NASA Technical Reports Server (NTRS)

    Vahia, M. N.; Biswas, S.; Durgaprasad, N.

    1985-01-01

    Differential spectra of even charged nuclei between Si and Fe in the August 4, 1972 event were made in the energy region of 10 to 40 MeV/n-1 using rocket borne plastic detectors. The resulting relative abundances of elements and low energy enhancements are obtained and compared with spectroscopically determined photospheric abundances. The implications of the relative abundances on the acceleration mechanisms is discussed.

  10. Process for synthesizing compounds from elemental powders and product

    DOEpatents

    Rabin, B.H.; Wright, R.N.

    1993-12-14

    A process for synthesizing intermetallic compounds from elemental powders is described. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe[sub 3] Al and FeAl. 25 figures.

  11. The Universality of the Rapid Neutron-capture Process Revealed by a Possible Disrupted Dwarf Galaxy Star

    NASA Astrophysics Data System (ADS)

    Casey, Andrew R.; Schlaufman, Kevin C.

    2017-12-01

    The rapid neutron-capture or r-process is thought to produce the majority of the heavy elements (Z> 30) in extremely metal-poor stars. The same process is also responsible for a significant fraction of the heavy elements in the Sun. This universality of the r-process is one of its characteristic features, as well as one of the most important clues to its astrophysical origin. We report the discovery of an extremely metal-poor field giant with [{Sr},{Ba}/{{H}}]≈ -6.0 and [{Sr},{Ba}/{Fe}]≈ -3.0, the lowest abundances of strontium and barium relative to iron ever observed. Despite its low abundances, the star 2MASS J151113.24-213003.0 has [{Sr}/{Ba}]=-0.11+/- 0.14, therefore its neutron-capture abundances are consistent with the main solar r-process pattern that has [{Sr}/{Ba}]=-0.25. It has been suggested that extremely low neutron-capture abundances are a characteristic of dwarf galaxies, and we find that this star is on a highly eccentric orbit with an apocenter ≳100 kpc that lies in the disk of satellites in the halo of the Milky Way. We show that other extremely metal-poor stars with low [Sr, Ba/H] and [Sr, Ba/Fe] plus solar [Sr/Ba] tend to have orbits with large apocenters, consistent with a dwarf galaxy origin for this class of object. The nucleosynthesis event that produced the neutron-capture elements in 2MASS J151113.24-213003.0 must produce both strontium and barium together in the solar ratio. We exclude contributions from the s-process in intermediate-mass asymptotic giant branch or fast-rotating massive metal-poor stars, pair-instability supernovae, the weak r-process, and neutron-star mergers. We argue that the event was a Pop III or extreme Pop II core-collapse supernova explosion. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  12. The isotope composition of selenium in chondrites constrains the depletion mechanism of volatile elements in solar system materials

    NASA Astrophysics Data System (ADS)

    Vollstaedt, Hauke; Mezger, Klaus; Leya, Ingo

    2016-09-01

    Solar nebula processes led to a depletion of volatile elements in different chondrite groups when compared to the bulk chemical composition of the solar system deduced from the Sun's photosphere. For moderately-volatile elements, this depletion primarily correlates with the element condensation temperature and is possibly caused by incomplete condensation from a hot solar nebula, evaporative loss from the precursor dust, and/or inherited from the interstellar medium. Element concentrations and interelement ratios of volatile elements do not provide a clear picture about responsible mechanisms. Here, the abundance and stable isotope composition of the moderately- to highly-volatile element Se are investigated in carbonaceous, ordinary, and enstatite chondrites to constrain the mechanism responsible for the depletion of volatile elements in planetary bodies of the inner solar system and to define a δ 82 / 78 Se value for the bulk solar system. The δ 82 / 78 Se of the studied chondrite falls are identical within their measurement uncertainties with a mean of - 0.20 ± 0.26 ‰ (2 s.d., n = 14, relative to NIST SRM 3149) despite Se abundance depletions of up to a factor of 2.5 with respect to the CI group. The absence of resolvable Se isotope fractionation rules out a kinetic Rayleigh-type incomplete condensation of Se from the hot solar nebula or partial kinetic evaporative loss on the precursor material and/or the parent bodies. The Se depletion, if acquired during partial condensation or evaporative loss, therefore must have occurred under near equilibrium conditions to prevent measurable isotope fractionation. Alternatively, the depletion and cooling of the nebula could have occurred simultaneously due to the continuous removal of gas and fine particles by the solar wind accompanied by the quantitative condensation of elements from the pre-depleted gas. In this scenario the condensation of elements does not require equilibrium conditions to avoid isotope

  13. REVIEWS OF TOPICAL PROBLEMS: The theory of nucleosynthesis in stars: the slow neutron capture process

    NASA Astrophysics Data System (ADS)

    Chechev, Valerii P.; Kramarovskiĭ, Ya M.

    1981-07-01

    The theory of the s process of nucleosynthesis has received considerable development during recent years, mainly as the result of more detailed physical and mathematical treatments and also as a result of the accumulation of new observational data on stellar evolution and the abundance of the elements in the solar system, and accumulation of experimental data on neutron-capture cross sections. The exact solution of the s process equations obtained recently by Newman (1978) is discussed. It confirms the correctness of the initial s process theory (Clayton, Fowler, Hull, and Zimmerman, 1961). At the same time for small neutron exposures the exact and initial solutions differ. The influence of branching of the s-process due to competition between β decay and neutron capture is analyzed; it is noted that at a temperature ~3·108 K and a density of free neutrons 1.6·107 cm-3 the s process theory is in good agreement with observational data on the yields of the various nuclides. Models are discussed for the pulsed neutron s process, which leads to formation of heavy elements in the interior of a star as the result of periodic flares of the helium shell and subsequent remixing of the material.

  14. Search for trans-iron elements in hot, helium-rich white dwarfs with the HST Cosmic Origins Spectrograph

    NASA Astrophysics Data System (ADS)

    Hoyer, D.; Rauch, T.; Werner, K.; Kruk, J. W.

    2018-04-01

    The metal abundances in the atmospheres of hot white dwarfs (WDs) entering the cooling sequence are determined by the preceding Asymptotic Giant Branch (AGB) evolutionary phase and, subsequently, by the onset of gravitational settling and radiative levitation. In this paper, we investigate three hot He-rich WDs, which are believed to result from a late He-shell flash. During such a flash, the He-rich intershell matter is dredged up and dominates the surface chemistry. Hence, in contrast to the usual H-rich WDs, their spectra allow direct access to s-process element abundances in the intershell that were synthesized during the AGB stage. In order to look for trans-iron group elements (atomic number Z > 29), we performed a non-local thermodynamic equilibrium model atmosphere analysis of new ultraviolet spectra taken with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. One of our program stars is of PG 1159 spectral type; this star, PG 1707+427, has effective temperature Teff = 85 000 K, and surface gravity logg = 7.5. The two other stars are DO white dwarfs: WD 0111+002 has Teff = 58 000 K and log g = 7.7, and PG 0109+111 has Teff = 70 000 K and log g = 8.0. These stars trace the onset of element diffusion during early WD evolution. While zinc is the only trans-iron element we could detect in the PG 1159 star, both DOs exhibit lines from Zn, Ga, Ge, Se; one additionally exhibits lines from Sr, Sn, Te, and I and the other from As. Generally, the trans-iron elements are very abundant in the DOs, meaning that radiative levitation must be acting. Most extreme is the almost six orders of magnitude oversolar abundance of tellurium in PG 0109+111. In terms of mass fraction, it is the most abundant metal in the atmosphere. The two DOs join the hitherto unique hot DO RE 0503-289, in which 14 trans-iron elements had even been identified. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which

  15. Geothermal chemical elements in lichens of Yellowstone National Park

    USGS Publications Warehouse

    Bennett, J.P.; Wetmore, C.M.

    1999-01-01

    Geothermal features (e.g. geysers, fumaroles, vents, and springs) emit gaseous mercury, sulfur and heavy metals and therefore, are natural sources of these elements in the atmosphere. Field studies of heavy metals in lichens in Italy have detected elevated concentrations near geothermal power plants, and have determined that the origin of mercury is from soil degassing, not soil particles. We studied this phenomenon in a geothermal area without power plants to determine the natural levels of mercury and other elements. Two common and abundant species of epiphytic Lichens, Bryoria fremontii and Letharia vulpina, were collected at six localities in Yellowstone National Park, USA in 1998 and analyzed for 22 chemical elements. Thirteen elements differed significantly between species. Some elements were significantly higher in the southern part of the park, while others were higher in the north. Levels of most elements were comparable with those in other national parks and wilderness areas in the region, except Hg, which was unusually high. The most likely sources of this element are the geothermal features, which are known emitters of Hg. Multivariate analyses revealed strong positive associations of Hg with S, and negative associations with soil elements, providing strong evidence that the Hg in the lichens is the result of soil degassing of elemental Hg rather than particulate Hg directly from soils. Average Hg levels in the lichens were 140 p.p.b. in Bryoria and 110 p.p.b. in Letharia, but maxima were 291 and 243 p.p.b., respectively. In spite of this, both species were healthy and abundant throughout the park.

  16. Role of Oxygen as Surface-Active Element in Linear GTA Welding Process

    NASA Astrophysics Data System (ADS)

    Yadaiah, Nirsanametla; Bag, Swarup

    2013-11-01

    Although the surface-active elements such as oxygen and sulfur have an adverse effect on momentum transport in liquid metals during fusion welding, such elements can be used beneficially up to a certain limit to increase the weld penetration in the gas tungsten arc (GTA) welding process. The fluid flow pattern and consequently the weld penetration and width change due to a change in coefficient of surface tension from a negative value to a positive value. The present work is focused on the analysis of possible effects of surface-active elements to change the weld pool dimensions in linear GTA welding. A 3D finite element-based heat transfer and fluid flow model is developed to study the effect of surface-active elements on stainless steel plates. A velocity in the order of 180 mm/s due to surface tension force is estimated at an optimum concentration of surface-active elements. Further, the differential evolution-based global optimization algorithm is integrated with the numerical model to estimate uncertain model parameters such as arc efficiency, effective arc radius, and effective values of material properties at high temperatures. The effective values of thermal conductivity and viscosity are estimated to be enhanced nine and seven times, respectively, over corresponding room temperature values. An error analysis is also performed to find out the overall reliability of the computed results, and a maximum reliability of 0.94 is achieved.

  17. Distribution, abundance, and biology of the alewife in U.S. waters of Lake Superior

    USGS Publications Warehouse

    Bronte, Charles R.; Selgeby, James H.; Curtis, Gary L.

    1991-01-01

    Alewives (Alosa pseudoharengus) were first reported in Lake Superior in 1954 and gradually increased in abundance in the late 1950s. In the 1960s and early 1970s, the fish were widespread in the lake but scarce. We determined the more recent abundance and distribution of alewives by cross-contour trawling in the spring in 1978–1988. Alewives were scarce lake-wide; the mean catch rate was only 23 fish per 100 h of trawling and represented a density of 0.003 kg per hectare in the area swept by the trawls. Fish of six age groups were caught in trawls in spring and gill nets in fall in 1983–1987. Total annual mortality was 64%, a high natural rate in the absence of fishing. Alewives in Lake Superior were small at the end of their first growing season but later grew faster than those in the other Great Lakes. Fecundity, estimated to be 64,000 eggs (mean total length = 187 mm) was higher than in other freshwater stocks. Zooplankton was the major food of alewives < 100 mm long and Mysis was the main food of larger fish. Exposure to water temperatures below lethal minimums for overwintering fish and for developing eggs limits the success of this species in Lake Superior.

  18. Elemental abundance analyses with DAO spectrograms. VII - The late normal B stars Pi Ceti, 134 Tauri, 21 Aquilae, and Nu Capricorni and the use of RETICON spectra

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.

    1991-09-01

    This paper presents elemental abundance analyses of sharp-lined normal late B stars. These stars exhibit mostly near-solar abundances, but each star also shows a few abundances which are a factor of 2 less than solar. The coadded photographic spectrograms are supplemented with Reticon data. A comparison of 261 equivalent widths on 2.4 A/mm spectra of sharp-lined B and A stars shows that the Reticon equivalent widths are about 95 percent of the coadded equivalent mean. The H-gamma profiles of the coadded and Reticon spectra for eight sharp-lined stars show generally good agreement. The generally high quality of the coadded data produced from 10 or more spectrograms is confirmed using the REDUCE graphics-oriented computed reduction code. For five stars, metal lines which fall in the gap between the U and V plates are analyzed using Reticon data.

  19. Elemental abundance analyses with DAO spectrograms. VII - The late normal B stars Pi Ceti, 134 Tauri, 21 Aquilae, and Nu Capricorni and the use of Reticon spectra

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.

    1991-01-01

    This paper presents elemental abundance analyses of sharp-lined normal late B stars. These stars exhibit mostly near-solar abundances, but each star also shows a few abundances which are a factor of 2 less than solar. The coadded photographic spectrograms are supplemented with Reticon data. A comparison of 261 equivalent widths on 2.4 A/mm spectra of sharp-lined B and A stars shows that the Reticon equivalent widths are about 95 percent of the coadded equivalent mean. The H-gamma profiles of the coadded and Reticon spectra for eight sharp-lined stars show generally good agreement. The generally high quality of the coadded data produced from 10 or more spectrograms is confirmed using the REDUCE graphics-oriented computed reduction code. For five stars, metal lines which fall in the gap between the U and V plates are analyzed using Reticon data.

  20. Atomic weights of the elements--Review 2000 (IUPAC Technical Report)

    USGS Publications Warehouse

    de Laeter, John R.; Böhlke, John Karl; De Bièvre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

    2003-01-01

    A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 ×10−7 . Isotope abundances for an increasing number of elements can be measured to better than 1 ×10−3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample