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Sample records for tepid supergiants chemical

  1. A Spectroscopic Study of Blue Supergiant Stars in the Sculptor Galaxy NGC 55: Chemical Evolution and Distance

    NASA Astrophysics Data System (ADS)

    Kudritzki, R. P.; Castro, N.; Urbaneja, M. A.; Ho, I.-T.; Bresolin, F.; Gieren, W.; Pietrzyński, G.; Przybilla, N.

    2016-10-01

    Low-resolution (4.5-5 Å) spectra of 58 blue supergiant stars distributed over the disk of the Magellanic spiral galaxy NGC 55 in the Sculptor group are analyzed by means of non-LTE techniques to determine stellar temperatures, gravities, and metallicities (from iron peak and α-elements). A metallicity gradient of -0.22 ± 0.06 dex/R 25 is detected. The central metallicity on a logarithmic scale relative to the Sun is [Z] = -0.37 ± 0.03. A chemical evolution model using the observed distribution of column densities of the stellar and interstellar medium gas mass reproduces the observed metallicity distribution well and reveals a recent history of strong galactic mass accretion and wind outflows with accretion and mass-loss rates of the order of the star formation rate. There is an indication of spatial inhomogeneity in metallicity. In addition, the relatively high central metallicity of the disk confirms that two extraplanar metal-poor H ii regions detected in previous work 1.13 to 2.22 kpc above the galactic plane are ionized by massive stars formed in situ outside the disk. For a subsample of supergiants, for which Hubble Space Telescope photometry is available, the flux-weighted gravity-luminosity relationship is used to determine a distance modulus of 26.85 ± 0.10 mag.

  2. Chemical abundances for A-and F-type supergiant stars

    NASA Astrophysics Data System (ADS)

    Molina, R. E.; Rivera, H.

    2016-10-01

    We present the stellar parameters and elemental abundances of a set of A-F-type supergiant stars HD 45674, HD 180028, HD 194951 and HD 224893 using high resolution (R≈ 42,000) spectra taken from ELODIE library. We present the first results of the abundance analysis for HD 45674 and HD 224893. We reaffirm the abundances for HD 180028 and HD 194951 studied previously by Luck. Alpha-elements indicate that the objects belong to the thin disc population. Their abundances and their location on the Hertzsprung-Russell diagram seem to indicate that HD 45675, HD 194951 and HD 224893 are in the post-first dredge-up (post-1DUP) phase, and that they are moving in the red-blue loop region. HD 180028, on the contary, shows typical abundances of Population I, but its evolutionary status cannot be satisfactorily defined.

  3. CHEMICAL ABUNDANCE PATTERNS IN THE INNER GALAXY: THE SCUTUM RED SUPERGIANT CLUSTERS

    SciTech Connect

    Davies, Ben; Origlia, Livia; Kudritzki, Rolf-Peter; Figer, Don F.; Rich, R. Michael; Najarro, Francisco; Negueruela, Ignacio; Clark, J. Simon

    2009-05-10

    The location of the Scutum Red Supergiant (RSG) clusters at the end of the Galactic Bar makes them an excellent probe of the Galaxy's secular evolution, while the clusters themselves are ideal testbeds in which to study the predictions of stellar evolutionary theory. To this end, we present a study of the RSG's surface abundances using a combination of high-resolution Keck/NIRSPEC H-band spectroscopy and spectral synthesis analysis. We provide abundance measurements for elements C, O, Si, Mg, Ti, and Fe. We find that the surface abundances of the stars studied are consistent with CNO burning and deep, rotationally enhanced mixing. The average {alpha}/Fe ratios of the clusters are solar, consistent with a thin-disk population. However, we find significantly subsolar Fe/H ratios for each cluster, a result which strongly contradicts a simple extrapolation of the Galactic metallicity gradient to lower Galactocentric distances. We suggest that a simple one-dimensional parameterization of the Galaxy's abundance patterns is insufficient at low Galactocentric distances, as large azimuthal variations may be present. Indeed, we show that the abundances of O, Si, and Mg are consistent with independent measurements of objects in similar locations in the Galaxy. In combining our results with other data in the literature, we present evidence for large-scale ({approx} kpc) azimuthal variations in abundances at Galactocentric distances of 3-5 kpc. While we cannot rule out that this observed behavior is due to systematic offsets between different measurement techniques, we do find evidence for similar behavior in a study of the barred spiral galaxy NGC 4736 which uses homogeneous methodology. We suggest that these azimuthal abundance variations could result from the intense but patchy star formation driven by the potential of the central bar.

  4. Secular resonant dressed orbital diffusion - I. Method and WKB limit for tepid discs

    NASA Astrophysics Data System (ADS)

    Fouvry, Jean-Baptiste; Pichon, Christophe; Prunet, Simon

    2015-05-01

    The equation describing the secular diffusion of a self-gravitating collisionless system induced by an exterior perturbation is derived while assuming that the time-scale corresponding to secular evolution is much larger than that corresponding to the natural frequencies of the system. Its two-dimensional formulation for a tepid galactic disc is also derived using the epicyclic approximation. Its Wentzel-Kramers-Brillouin (WKB) limit is found while assuming that only tightly wound transient spirals are sustained by the disc. It yields a simple quadrature for the diffusion coefficients which provides a straightforward understanding of the loci of maximal diffusion within the disc.

  5. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Fullerton, A. W.; Massa, D. L.; Prinja, R. K.; Owocki, S. P.; Cranmer, S. R.

    1998-01-01

    This report summarizes the progress of the work conducted under the program "The Winds of B Supergiants," conducted by Raytheon STX Corporation. The report consists of a journal article "Wind variability in B supergiants III. Corotating spiral structures in the stellar wind of HD 64760." The first step in the project was the analysis of the 1996 time series of 2 B supergiants and an O star. These data were analyzed and reported on at the ESO workshop, "Cyclical Variability in Stellar Winds."

  6. Secular resonant dressed orbital diffusion - II. Application to an isolated self-similar tepid galactic disc

    NASA Astrophysics Data System (ADS)

    Fouvry, Jean-Baptiste; Pichon, Christophe

    2015-05-01

    The main orbital signatures of the secular evolution of an isolated self-gravitating stellar Mestel disc are recovered using a dressed Fokker-Planck formalism in angle-action variables. The shot-noise-driven formation of narrow ridges of resonant orbits is recovered in the WKB limit of tightly wound transient spirals, for a tepid Toomre-stable tapered disc. The relative effect of the bulge, the halo, the disc temperature and the spectral properties of the shot noise are investigated in turn. For such galactic discs all elements seem to impact the locus and direction of the ridge. For instance, when the halo mass is decreased, we observe a transition between a regime of heating in the inner regions of the disc through the inner Lindblad resonance to a regime of radial migration of quasi-circular orbits via the corotation resonance in the outer part of the disc. The dressed secular formalism captures both the nature of collisionless systems (via their natural frequencies and susceptibility), and their nurture via the structure of the external perturbing power spectrum. Hence it provides the ideal framework in which to study their long-term evolution.

  7. Clusters rich in red supergiants

    NASA Astrophysics Data System (ADS)

    Negueruela, Ignacio

    In the past few years, several clusters containing large numbers of red supergiants have been discovered. These clusters are amongst the most massive young clusters known in the Milky Way, with stellar masses reaching a few 104 M ⊙. They have provided us, for the first time, with large homogeneous samples of red supergiants of a given age. These large populations make them, despite heavy extinction along their sightlines, powerful laboratories to understand the evolutionary status of red supergiants. While some of the clusters, such as the eponymous RSGC1, are so obscured that their members are only observable in the near-IR, some of them are easily accessible, allowing for an excellent characterisation of cluster and stellar properties. The information gleaned so far from these clusters gives strong support to the idea that late-M type supergiants represent a separate class, characterised by very heavy mass loss. It also shows that the spectral-type distribution of red supergiants in the Milky Way is very strongly peaked towards M1, while suggesting a correlation between spectral type and evolutionary stage.

  8. Supergiants and the Galactic metallicity gradient. II - Spectroscopic abundances for 64 distant F- to M-type supergiants

    NASA Astrophysics Data System (ADS)

    Luck, R. Earle; Bond, Howard E.

    1989-11-01

    The metallicity gradient in the Galactic disk from in situ stars with visual magnitude ranging from 6 to 10 is analyzed. Atmospheric parameters and detailed chemical abundances for 64 Population I supergiants of spectral types F through M and luminosity classes Ia through II have been determined. The derived Fe/H ratios ranging from -0.5 to + 0.7 show a mean value of +0.13 with an estimated uncertainty of + or - 0.2. A subset of 25 supergiants fainter than 7th magnitude lying in the direction of the Galactic center shows a Fe/H mean of +0.18 + or - 0.04, while a similar sample of 15 faint supergiants lying in the direction of the Galactic anticenter shows a lower Fe/H mean of +0.07 + or - 0.06. For a sample of bright supergiants analyzed by Luck and Lambert (1985), the mean abundance pattern for all 64 stars showed the following: deficient C and O along with enhancement of N, indicating mixing of CNO-cycled material to the stellar surfaces; an apparent Sr enhancement attributed to departures from LTE; and an essentially solar pattern of other chemical elements.

  9. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, D.; Fullerton, A. W.; Prinja, R. K.

    1998-01-01

    This quarterly report is comprised of a paper, "Rotational Modulation of B Supergiant Winds" presented at the ESO workshop "Cyclical Variability in Stellar Winds." Presented is a 30-day IUE time series of the BO Ia HD 91969, a member of the Carina open cluster NGC 3293, which showed, among other things, that wind lines that probe more deeply into the wind vary more regularly.

  10. Open clusters rich in red supergiants

    NASA Astrophysics Data System (ADS)

    Negueruela, Ignacio

    2015-08-01

    In the past few years, several clusters containing large numbers of red supergiants have been discovered. These clusters are amongst the most massive young clusters known in the Milky Way, with stellar masses reaching a few tens of thousands of solar masses. They have provided us, for the first time, with large homogeneous samples of red supergiants of a given age. These large populations make them, despite heavy extinction along their sightlines, powerful laboratories to understand the evolutionary status of red supergiants. While some of the clusters, such as the eponymous RSGC1, are so obscured that their members are only observable in the near-IR, at least van der Bergh-Hagen 222 is observable even in the U band, allowing for an excellent characterisation of cluster and stellar properties. The information gleaned so far from these clusters gives strong support to the idea that late-M type supergiants represent a separate class, characterised by very heavy mass loss. It also shows that the spectral-type distribution of red supergiants in the Milky Way is very strongly peaked towards M1, while providing strong hints about the possible evolutionary sequence of red supergiants. In addition, the clusters of red supergiants represent ideal tools to study metallicity in the inner regions of the Milky Way.

  11. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, Derck; West, D. (Technical Monitor)

    2002-01-01

    We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasizes the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M qi) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a

  12. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, D.; Oliversen, R. (Technical Monitor)

    2002-01-01

    We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters, but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M (dot) q(sub i)) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can

  13. New perspectives on red supergiants

    NASA Astrophysics Data System (ADS)

    Dorda, R.; Negueruela, I.; González-Fernández, C.; Tabernero H. M.

    2017-03-01

    There is a high interest in cool supergiants (CSGs), because they play a key role in the understanding of the evolution and death of massive stars: most high-mass stars pass through this phase at some point of their evolution, and the physical conditions during it will determine their subsequent evolution. In addition, these stars are a powerful high-mass stellar formation tracers and also the main progenitors of core-collapse supernovae (SNe). Despite this, they are poorly characterized in some aspects: their extreme sizes and peculiar conditions defy the predictions of present-day atmospheric and evolutionary models. To bring perspective to this topic, we investigate the behaviour of CSGs as a population. For this, we studied the largest homogeneous multiepoch spectroscopic sample of CSGs (from the SMC and LMC) to date (>500). Our results give a new global view about the physical conditions of CSGs and their evolution

  14. Red supergiants as type II supernova progenitors

    NASA Astrophysics Data System (ADS)

    Negueruela, Ignacio; Dorda, Ricardo; González-Fernández, Carlos; Marco, Amparo

    2015-08-01

    Recent searches for supernova IIp progenitors in external galaxies have led to the identification of red objects with magnitudes and colours indicative of red supergiants, in most cases implying quite low luminosities and hence masses well below 10Msol. Stellar models, on the other hand, do not predict explosions from objects below 9 Msol. What does our knowledge of local red supergiants tells us about the expected properties of such objects?We have carried out a comprehensive spectroscopic and photometric study of a sample of hundreds of red supergiants in the Milky Way and both Magellanic Clouds. We have explored correlations between different parameters and the position of stars in the HR diagrams of open clusters. At solar metallicty, there is strong evidence for a phase of very heavy mass loss at the end of the red supergiant phase, but the existence of such a phase is still not confirmed at SMC metallicities. Objects of ~ 7Msol, on the other hand, become very dusty in the SMC, and appear as very luminous Miras.Among Milky Way clusters, we find a surprising lack of objects readily identifiable as the expected 7 to 10 Msol red supergiants or AGB stars. We are carrying out an open cluster survey aimed at filling this region of the HR diagram with reliable data. Finally, we will discuss the implications of all this findings for the expected properties of supernova progenitors, as it looks unlikely that typical red supergiants may explode without undergoing further evolution.

  15. B supergiants in open clusters and associations

    NASA Astrophysics Data System (ADS)

    Garmany, C. D.

    The final report on project NAG5-78, 'IUE Observations of B Supergiants in the Large Magellanic Cloud', a collaborative effort between Garmany (U. of Colorado), Sonneborn (Goddard Space Flight Center) and Fitzpatrick (Princeton Univ.) is presented. Over 90 B supergiants in the Large Magellanic Cloud with the IUE satellite, using the low dispersion mode were observed. These stars were chosen because they resemble the precursor star to SN 1987a, and a data base in the continuing effort to understand why the precursor star was a blue, not a red supergiant was needed. The observations were all reduced and made into an atlas, and efforts to understand the evolutionary history of stars of the H-R diagram are underway.

  16. A homogeneous survey of red supergiants

    NASA Astrophysics Data System (ADS)

    Marco, Amparo; Dorda, Ricardo; González-Fernández, Carlos; Negueruela, Ignacio

    2015-08-01

    We have carried out a comprehensive homogeneous spectroscopic and photometric study of a sample of a few hundred red supergiants in the Milky Way, the Large Magellanic Cloud and the Small Magellanic Cloud. Our results show that global trends can be derived for many spectroscopic features independently of metallicity. The intensity of atomic Ti lines is directly correlated to spectral type, suggesting a real temperature change in the photospheric temperature. We find that the shape of the spectral energy distribution stops being directly related to surface temperature around mid-K spectral types, and becomes strongly correlated to mass loss. The distribution of spectral types is markedly different for the subset of red supergiants above a given luminosity cut, giving very strong hints of a separate evolutionary phase.

  17. Mass loss in red giants and supergiants

    NASA Technical Reports Server (NTRS)

    Sanner, F.

    1975-01-01

    The circumstellar envelopes surrounding late-type giants and supergiants were studied using high resolution, photoelectric scans of strong optical resonance lines. A method for extracting the circumstellar from the stellar components of the lines allowed a quantitative determination of the physical conditions in the envelopes and the rates of mass loss at various positions in the red giant region of the HR diagram. The observed strengthening of the circumstellar spectrum with increasing luminosity and later spectral type is probably caused by an increase in the mass of the envelopes. The mass loss rate for individual stars is proportional to the visual luminosity; high rates for the supergiants suggest that mass loss is important in their evolution. The bulk of the mass return to the interstellar medium in the red giant region comes from the normal giants, at a rate comparable to that of planetary nebulae.

  18. Fossil dust shells around luminous supergiants

    NASA Technical Reports Server (NTRS)

    Stothers, R.

    1975-01-01

    The observed frequency with which infrared excesses appear in F, G, and K supergiants of luminosity class Ia supports the idea that these excesses arise in a 'fossil' circumstellar dust shell that was formed during a prior M-super-giant phase of evolution. The required leftward evolution of the star on the H-R diagram would then imply that the Ledoux, rather than the Schwarzschild, criterion for convective mixing is the correct criterion to use in stellar evolution calculations.

  19. The Red Supergiant Content of M31*

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Evans, Kate Anne

    2016-08-01

    We investigate the red supergiant (RSG) population of M31, obtaining the radial velocities of 255 stars. These data substantiate membership of our photometrically selected sample, demonstrating that Galactic foreground stars and extragalactic RSGs can be distinguished on the basis of B - V, V - R two-color diagrams. In addition, we use these spectra to measure effective temperatures and assign spectral types, deriving physical properties for 192 RSGs. Comparison with the solar metallicity Geneva evolutionary tracks indicates astonishingly good agreement. The most luminous RSGs in M31 are likely evolved from 25-30 M ⊙ stars, while the vast majority evolved from stars with initial masses of 20 M ⊙ or less. There is an interesting bifurcation in the distribution of RSGs with effective temperatures that increases with higher luminosities, with one sequence consisting of early K-type supergiants, and with the other consisting of M-type supergiants that become later (cooler) with increasing luminosities. This separation is only partially reflected in the evolutionary tracks, although that might be due to the mis-match in metallicities between the solar Geneva models and the higher-than-solar metallicity of M31. As the luminosities increase the median spectral type also increases; i.e., the higher mass RSGs spend more time at cooler temperatures than do those of lower luminosities, a result which is new to this study. Finally we discuss what would be needed observationally to successfully build a luminosity function that could be used to constrain the mass-loss rates of RSGs as our Geneva colleagues have suggested. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.

  20. Postexplosion hydrodynamics of supernovae in red supergiants

    NASA Technical Reports Server (NTRS)

    Herant, Marc; Woosley, S. E.

    1994-01-01

    Shock propagation, mixing, and clumping are studied in the explosion of red supergiants as Type II supernovae using a two-dimensional smooth particle hydrodynamic (SPH) code. We show that extensive Rayleigh-Talor instabilities develop in the ejecta in the wake of the reverse shock wave. In all cases, the shell structure of the progenitor is obliterated to leave a clumpy, well-mixed supernova remnant. However, the occurrence of mass loss during the lifetime of the progenitor can significantly reduce the amount of mixing. These results are independent of the Type II supernova explosion mechanism.

  1. Stellar Parameters and Winds of Red Supergiants in Binaries

    NASA Astrophysics Data System (ADS)

    Bennett, K.

    The proposed target stars (zeta Aur, 31 Cyg) are eclipsing binary systems with K supergiant primaries and B-type main sequence companions. From these binaries, we will determine key information about fundamental stellar parameters and outer atmospheric structure that can not be obtained from observations of single red supergiants. The proposed observations are directed towards understanding the mass loss process driving the massive winds of red supergiants. In particular, the proposed FUSE observations will support the following analyses: -- detailed model atmosphere analyses of the B-stars' continua -- determining accurate radial velocities of the B-type secondaries -- analyses of the wind absorption features of the red supergiant primaries. From these FUSE observations, we will determine improved fundamental stellar parameters of red supergiants (effective temperatures, radii, masses and luminosities) and wind properties (velocity laws and mass loss rates).

  2. RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES. II. NLTE EFFECTS IN J-BAND SILICON LINES

    SciTech Connect

    Bergemann, Maria; Kudritzki, Rolf-Peter; Wuerl, Matthias; Plez, Bertrand; Davies, Ben; Gazak, Zach E-mail: Matthias.Wuerl@physik.uni-muenchen.de E-mail: zgazak@ifa.hawaii.edu E-mail: bdavies@ast.cam.ac.uk

    2013-02-20

    Medium-resolution J-band spectroscopy of individual red supergiant stars is a promising tool to investigate the chemical composition of the young stellar population in star-forming galaxies. As a continuation of recent work on iron and titanium, detailed non-LTE (NLTE) calculations are presented to investigate the influence of NLTE on the formation of silicon lines in the J-band spectra of red supergiants. Substantial effects are found resulting in significantly stronger absorption lines of neutral silicon in NLTE. As a consequence, silicon abundances determined in NLTE are significantly smaller than in local thermodynamic equilibrium (LTE) with the NLTE abundance corrections varying smoothly between -0.4 dex and -0.1 dex for effective temperatures between 3400 K and 4400 K. The effects are largest at low metallicity. The physical reasons behind the NLTE effects and the consequences for extragalactic J-band abundance studies are discussed.

  3. Probing the structure and dynamics of B[e] supergiant stars' disks

    NASA Astrophysics Data System (ADS)

    Kraus, M.

    2016-08-01

    B[e] supergiants are a group of evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulates in a circumstellar ring or disk-like structure, revolving around the star on Keplerian orbits. In most objects, the disks seem to be stable over many decades. This guarantees these disks as ideal chemical laboratories to study molecule formation and dust condensation. Combining high-resolution optical and infrared spectroscopic data allows to search for emission features that trace the disk structure, kinematics, and chemical composition at different distances from the star. Certain forbidden emission lines of singly ionized or neutral metals, such as [Caii] and [Oi], are ideal tracers for the innermost gaseous (atomic) regions. Farther out, molecules form. While first-overtone bands of carbon monoxide (CO) mark the hot, inner rim of the molecular disk, more molecules are expected to form and to fill the space between the CO emitting region and the dust condensation zone. Observing campaigns have been initiated to search for these molecules and their emission features, in order to construct a global picture of the properties of the disks around B[e] supergiants. This paper presents an overview of the status of our knowledge about the structure and kinematics of B[e] supergiant stars' disks, based on currently available information from different observational tracers.

  4. Long term variability of B supergiant winds

    NASA Technical Reports Server (NTRS)

    Massa, Derck L.

    1995-01-01

    The object of this observing proposal was to sample wind variability in B supergiants on a daily basis over a period of several days in order to determine the time scale with which density variability occurs in their winds. Three stars were selected for this project: 69 Cyg (B0 Ib), HD 164402 (B0 Ib), and HD 47240 (B1 Ib). Three grey scale representations of the Si IV lambda lambda 1400 doublet in each star are attached. In these figures, time (in days) increases upward, and the wavelength (in terms of velocity relative to the rest wavelength of the violet component of the doublet) is the abscissa. The spectra are normalized by a minimum absorption (maximum flux) template, so that all changes appear as absorptions. As a result of these observations, we can now state with some certainty that typical B supergiants develop significant wind inhomogeneities with recurrence times of a few days, and that some of these events show signs of strong temporal coherence.

  5. UV chromospheric and circumstellar diagnostic features among F supergiant stars

    NASA Technical Reports Server (NTRS)

    Stencel, R. E.; Worden, S. P.; Giampapa, M. S.

    1981-01-01

    A survey of F supergiant stars to evaluate the extension of chromospheric and circumstellar characteristics commonly observed in the slightly cooler G, K, and M supergiant is discussed. An ultraviolet survey was elected since UV features of Mg II and Fe II might persist in revealing outer atmosphere phenomena even among F supergiants. The encompassed spectral types F0 to G0, and luminosity classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission line width-to-luminosity correlation for the G-M stars in both the Ca II and Mg II lines is examined.

  6. RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES. III. NLTE EFFECTS IN J-BAND MAGNESIUM LINES

    SciTech Connect

    Bergemann, Maria; Kudritzki, Rolf-Peter; Gazak, Zach; Davies, Ben; Plez, Bertrand E-mail: kud@ifa.hawaii.edu E-mail: bdavies@ast.cam.ac.uk

    2015-05-10

    Non-local thermodynamic equilibrium (NLTE) calculations for Mg i in red supergiant stellar atmospheres are presented to investigate the importance of NLTE for the formation of Mg i lines in the NIR J-band. Recent work using medium resolution spectroscopy of atomic lines in the J-band of individual red supergiant stars has demonstrated this technique is a very promising tool for investigating the chemical composition of the young stellar population in star forming galaxies. As in previous work, where NLTE effects were studied for iron, titanium, and silicon, substantial effects are found resulting in significantly stronger Mg i absorption lines. For the quantitative spectral analysis the NLTE effects lead to magnesium abundances significantly smaller than in local thermodynamic equilibrium with the NLTE abundance corrections varying smoothly between −0.4 dex and −0.1 dex for effective temperatures between 3400 and 4400 K. We discuss the physical reasons of the NLTE effects and the consequences for extragalactic J-band abundance studies using individual red supergiants in the young massive galactic double cluster h and χ Persei.

  7. Supernova shock breakout from a red supergiant.

    PubMed

    Schawinski, Kevin; Justham, Stephen; Wolf, Christian; Podsiadlowski, Philipp; Sullivan, Mark; Steenbrugge, Katrien C; Bell, Tony; Röser, Hermann-Josef; Walker, Emma S; Astier, Pierre; Balam, Dave; Balland, Christophe; Carlberg, Ray; Conley, Alex; Fouchez, Dominique; Guy, Julien; Hardin, Delphine; Hook, Isobel; Howell, D Andrew; Pain, Reynald; Perrett, Kathy; Pritchet, Chris; Regnault, Nicolas; Yi, Sukyoung K

    2008-07-11

    Massive stars undergo a violent death when the supply of nuclear fuel in their cores is exhausted, resulting in a catastrophic "core-collapse" supernova. Such events are usually only detected at least a few days after the star has exploded. Observations of the supernova SNLS-04D2dc with the Galaxy Evolution Explorer space telescope reveal a radiative precursor from the supernova shock before the shock reached the surface of the star and show the initial expansion of the star at the beginning of the explosion. Theoretical models of the ultraviolet light curve confirm that the progenitor was a red supergiant, as expected for this type of supernova. These observations provide a way to probe the physics of core-collapse supernovae and the internal structures of their progenitor stars.

  8. X-ray Variability in the Hot Supergiant zgr Orionis.

    PubMed

    Berghöfer, T W; Schmitt, J H

    1994-09-16

    Hot massive stars represent only a small fraction of the stellar population of the galaxy, but their enormous luminosities make them visible over large distances. Therefore, they are ideal standard candles, used to determine distances of near galaxies. Their mass loss due to supersonic winds driven by radiation pressure contributes significantly to the interstellar medium and thus to the chemical evolution of galaxies. All hot stars are soft x-ray sources; in contrast to the sun with its highly variable x-ray flux, long time scale x-ray variability is not common among hot stars. An analysis is presented here of an unusual increase in x-ray flux observed with the roentgen observatory satellite during a period of 2 days for the hot supergiant zeta Orionis, the only episode of x-ray variability that has been found in a hot star. These observations provide the most direct evidence so far for the scenario of shock-heated gas in the winds of hot stars.

  9. A Runaway Red Supergiant in M31

    NASA Astrophysics Data System (ADS)

    Evans, Kate Anne; Massey, Philip

    2015-11-01

    A significant percentage of OB stars are runaways, so we can expect a similar percentage of their evolved descendants to also be runaways. However, recognizing such stars presents its own set of challenges, as these older, more evolved stars will have drifted farther from their birthplace, and thus their velocities might not be obviously peculiar. Several Galactic red supergiants (RSGs) have been described as likely runaways based on the existence of bow shocks, including Betelgeuse. Here we announce the discovery of a runaway RSG in M31 based on a 300 km s-1 discrepancy with M31's kinematics. The star is found about 21‧ (4.6 kpc) from the plane of the disk, but this separation is consistent with its velocity and likely age (˜10 Myr). The star, J004330.06+405258.4, is an M2 I, with MV = -5.7, {log}L/{L}⊙ = 4.76, an effective temperature of 3700 K, and an inferred mass of 12-15M⊙. The star may be a high-mass analog of the hypervelocity stars, given that its peculiar space velocity is probably 400-450 km s-1, comparable to the escape speed from M31's disk. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.

  10. A Runaway Red Supergiant in M31

    NASA Astrophysics Data System (ADS)

    Evans, Kate Anne; Massey, Philip

    2016-01-01

    A significant percentage of OB stars are runaways, so we should expect a similar percentage of their evolved descendants to also be runaways. However, recognizing such stars presents its own set of challenges, as these older, more evolved stars will have drifted further from their birthplace, and thus their velocities might not be obviously peculiar. Several Galactic red supergiants (RSGs) have been described as likely runaways, based upon the existence of bow shocks, including Betelgeuse. Here we announce the discovery of a runaway RSG in M31, based upon a 300 km s-1 discrepancy with M31's kinematics. The star is found about 21‧ (4.6 kpc) from the plane of the disk, but this separation is consistent with its velocity and likely age (˜10 Myr). The star, J004330.06+405258.4, is an M2 I, with MV=-5.7, log L/L⊙=4.76, an effective temperature of 3700 K, and an inferred mass of 12-15 M⊙. The star may be a high-mass analog of the hypervelocity stars, given that its peculiar space velocity is probably 400-450 km s-1, comparable to the escape speed from M31's disk. K. A. E.'s work was supported by the NSF's Research Experience for Undergraduates program through AST-1461200, and P. M.'s was partially supported by the NSF through AST-1008020 and through Lowell Observatory.

  11. Wind Variability in Intermediate Luminosity B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, Derck

    1996-01-01

    This study used the unique spectroscopic diagnostics of intermediate luminosity B supergiants to determine the ubiquity and nature of wind variability. Specifically, (1) A detailed analysis of HD 64760 demonstrated massive ejections into its wind, provided the first clear demonstration of a 'photospheric connection' and ionization shifts in a stellar wind; (2) The international 'IUE MEGA campaign' obtained unprecedented temporal coverage of wind variability in rapidly rotating stars and demonstrated regularly repeating wind features originating in the photosphere; (3) A detailed analysis of wind variability in the rapidly rotating B1 Ib, gamma Ara demonstrated a two component wind with distinctly different mean states at different epochs; (4) A follow-on campaign to the MEGA project to study slowly rotating stars was organized and deemed a key project by ESA/NASA, and will obtain 30 days of IUE observations in May-June 1996; and (5) A global survey of archival IUE time series identified recurring spectroscopic signatures, identified with different physical phenomena. Items 4 and 5 above are still in progress and will be completed this summer in collaboration with Raman Prinja at University College, London.

  12. Absolute energy curves from late B-type supergiants

    NASA Technical Reports Server (NTRS)

    Underhill, A. B.

    1981-01-01

    Energy curves were determined for six late B and early A type supergiants using IUE data and other ultraviolet and ground based photometry. Effective temperatures and angular diameters are presented as well as estimates of the outflow velocity of the wind. All six stars show a strong Balmer continuum in emission; the Ia supergiants also show an infrared excess which reaches into the visible range. Evidence is found for the presence of a warm mantle as well as for wind from the Ia stars.

  13. Spectral type, temperature, and evolutionary stage in cool supergiants

    NASA Astrophysics Data System (ADS)

    Dorda, Ricardo; Negueruela, Ignacio; González-Fernández, Carlos; Tabernero, Hugo M.

    2016-07-01

    Context. In recent years, our understanding of red supergiants has been questioned by strong disagreements between stellar atmospheric parameters derived with different techniques. Temperature scales have been disputed, and the possibility that spectral types do not depend primarily on temperature has been raised. Aims: We explore the relations between different observed parameters, and we explore the ability to derive accurate intrinsic stellar parameters from these relations through the analysis of the largest spectroscopic sample of red supergiants to date. Methods: We obtained intermediate-resolution spectra of a sample of about 500 red supergiants in the Large and the Small Magellanic Cloud. From these spectra, we derive spectral types and measure a large set of photospheric atomic lines. We explore possible correlations between different observational parameters, also making use of near- and mid-infrared colours and literature on photometric variability. Results: Direct comparison between the behaviour of atomic lines (Fe i, Ti i, and Ca ii) in the observed spectra and a comprehensive set of synthetic atmospheric models provides compelling evidence that effective temperature is the prime underlying variable driving the spectral-type sequence between early G and M2 for supergiants. In spite of this, there is a clear correlation between spectral type and luminosity, with later spectral types tending to correspond to more luminous stars with heavier mass loss. This trend is much more marked in the LMC than in the SMC. The population of red supergiants in the SMC is characterised by a higher degree of spectral variability, early spectral types (centred on type K1) and low mass-loss rates (as measured by dust-sensitive mid-infrared colours). The population in the LMC displays less spectroscopic variability and later spectral types. The distribution of spectral types is not single-peaked. Instead, the brightest supergiants have a significantly different

  14. The 13Carbon footprint of B[e] supergiants

    NASA Astrophysics Data System (ADS)

    Liermann, A.; Kraus, M.; Schnurr, O.; Fernandes, M. Borges

    2010-10-01

    We report on the first detection of 13C enhancement in two B[e] supergiants (B[e]SGs) in the Large Magellanic Cloud. Stellar evolution models predict the surface abundance in 13C to strongly increase during main-sequence and post-main-sequence evolution of massive stars. However, direct identification of chemically processed material on the surface of B[e]SGs is hampered by their dense, disc-forming winds, hiding the stars. Recent theoretical computations predict the detectability of enhanced 13C via the molecular emission in 13CO arising in the circumstellar discs of B[e]SGs. To test this potential method and to unambiguously identify a post-main-sequence B[e] SG by its 13CO emission, we have obtained high-quality K-band spectra of two known B[e] SGs in the Large Magellanic Cloud, using the Very Large Telescope's Spectrograph for INtegral Field Observation in the Near-Infrared (VLT/SINFONI). Both stars clearly show the 13CO band emission, whose strength implies a strong enhancement of 13C, in agreement with theoretical predictions. This first ever direct confirmation of the evolved nature of B[e]SGs thus paves the way to the first identification of a Galactic B[e]SG. Based on observations collected with the ESO VLT Paranal Observatory under programme 384.D-1078(A). E-mail: liermann@mpifr-bonn.mpg.de (AL); kraus@sunstel.asu.cas.cz (MK); oschnurr@aip.de (OS); borges@on.br (MBF)

  15. Direct imaging with a hypertelescope of red supergiant stellar surfaces

    NASA Astrophysics Data System (ADS)

    Patru, F.; Chiavassa, A.; Mourard, D.; Tarmoul, N.

    2010-07-01

    High angular resolution images obtained with a hypertelescope can strongly constrain the radiative-hydrodynamics simulations of red supergiant (RSG) stars, in terms of intensity contrast, granulation size and temporal variations of the convective motions that are visible on their surface. The characterization of the convective pattern in RSGs is crucial to solve the mass-loss mechanism which contributes heavily to the chemical enrichment of the Galaxy. We show here how the astrophysical objectives and the array configuration are highly dependent to design a hypertelescope. For a given field of view and a given resolution, there is a trade-off between the array geometry and the number of required telescopes to optimize either the (u,v) coverage (to recover the intensity distribution) or the dynamic range (to recover the intensity contrast). To obtain direct snapshot images of Betelgeuse with a hypertelescope, a regular and uniform layout of telescopes is the best array configuration to recover the intensity contrast and the distribution of both large and small granulation cells, but it requires a huge number of telescopes (several hundreds or thousands). An annular configuration allows a reasonable number of telescopes (lower than one hundred) to recover the spatial structures but it provides a low-contrast image. Concerning the design of a pupil densifier to combine all the beams, the photometric fluctuations are not critical (Delta photometry < 50%) contrary to the residual piston requirements (OPD < λ/8) which requires the development of an efficient cophasing system to fully exploit the imaging capability of a hypertelecope.

  16. Magnetic braking of stellar cores in red giants and supergiants

    SciTech Connect

    Maeder, André; Meynet, Georges E-mail: georges.meynet@unige.ch

    2014-10-01

    Magnetic configurations, stable on the long term, appear to exist in various evolutionary phases, from main-sequence stars to white dwarfs and neutron stars. The large-scale ordered nature of these fields, often approximately dipolar, and their scaling according to the flux conservation scenario favor a fossil field model. We make some first estimates of the magnetic coupling between the stellar cores and the outer layers in red giants and supergiants. Analytical expressions of the truncation radius of the field coupling are established for a convective envelope and for a rotating radiative zone with horizontal turbulence. The timescales of the internal exchanges of angular momentum are considered. Numerical estimates are made on the basis of recent model grids. The direct magnetic coupling of the core to the extended convective envelope of red giants and supergiants appears unlikely. However, we find that the intermediate radiative zone is fully coupled to the core during the He-burning and later phases. This coupling is able to produce a strong spin down of the core of red giants and supergiants, also leading to relatively slowly rotating stellar remnants such as white dwarfs and pulsars. Some angular momentum is also transferred to the outer convective envelope of red giants and supergiants during the He-burning phase and later.

  17. Characterisation of red supergiants in the Gaia spectral range

    NASA Astrophysics Data System (ADS)

    Dorda, Ricardo; González-Fernández, Carlos; Negueruela, Ignacio

    2016-11-01

    Context. The infrared calcium triplet and its nearby spectral region have been used for spectral and luminosity classification of late-type stars, but the samples of cool supergiants (CSGs) used have been very limited (in size, metallicity range, and spectral types covered). The spectral range of the Gaia Radial Velocity Spectrograph (RVS) covers most of this region but does not reach the main TiO bands in this region, whose depths define the M sequence. Aims: We study the behaviour of spectral features around the calcium triplet and develop effective criteria to identify and classify CSGs, comparing their efficiency with other methods previously proposed. Methods: We measure the main spectral features in a large sample (almost 600) of red supergiants (RSGs) from three different galaxies, and we analyse their behaviour through a principal component analysis. Using the principal components, we develop an automatised method to differentiate CSGs from other bright late-type stars, and to classify them. Results: The proposed method identifies a high fraction (0.98 ± 0.04) of the supergiants in our test sample, which cover a wide metallicity range (supergiants from the Magellanic Clouds and the Milky Way) and with spectral types from G0 up to late-M. In addition, it is capable to separate most of the non-supergiants in the sample, identifying as supergiants only a very small fraction of them (0.02 ± 0.04). A comparison of this method with other previously proposed shows that it is more efficient and selects less interlopers. A way to automatically assign a spectral type to the supergiants is also developed. We apply this study to spectra at the resolution and spectral range of the Gaia RVS, with a similar success rate. Conclusions: The method developed identifies and classifies CSGs in large samples, with high efficiency and low contamination, even in conditions of wide metallicity and spectral-type ranges. As this method uses the infrared calcium triplet spectral

  18. Models for circumstellar nebulae around red and blue supergiants

    NASA Astrophysics Data System (ADS)

    Chita, S. M.

    2011-10-01

    In this thesis, we model the circumstellar medium of stars with initial masses of 8, 12, 18 and 20 solar masses, over their entire life from the main sequence until their supernova explosion. During the post-main-sequence stages, stars can evolve through several blue and red supergiant stages depending on their initial mass, composition and rotation rate. The models considered in the second Chapter have long-lasting RSG stages starting after the MS. In this phase, they develop shells of RSG wind material at the location where the free streaming RSG wind is stalled by the thermal pressure of the hot MS bubble, close to the central star. The RSG shells develop violent Rayleigh-Taylor instabilities. Once these start to grow non-linear, the RSG shell becomes highly structured as clumps form, and shell material mixes with material in the hot bubble. Later, the stars evolve to the BSG stage, during which the RSG shells are completely destroyed. These models return to the RSG stage, and build new RSG shells, which are more massive than those formed earlier. RSG shells are essential for our understanding of bipolar emission nebulae around BSGs. In the third Chapter are shown the results of the wind-wind interaction model of single star with 12 solar masses. On a time scale of a few 10000 yr, a BSG hour-glas shaped nebula expands into the sphere defined by the RSG shell. The faster polar parts of the hour glass hit the inner edge of the RSG shell first. The collision creates a pair of hot and dense polar caps. As time passes, the collision zone moves to lower latitudes of the RSG shell and becomes more confined in latitude. At the same time, the interaction of the BSG wind with the equatorial disk defines a second, ring shaped collision zone in the equatorial plane. These structures are reminiscent of the observed nebulae around the blue supergiant Sher 25. In the Chapter 3 we present calculations that predict the properties of the circumstellar medium for rapidly rotating

  19. Unveiling the evolutionary phase of B[e] supergiants

    NASA Astrophysics Data System (ADS)

    Muratore, M. F.; Kraus, M.; Liermann, A.; Schnurr, O.; Cidale, L. S.; Arias, M. L.

    We obtained medium resolution K-band spectra for two B[e] supergiants and one yellow hypergiant (YHG) in the Large Magellanic Cloud (LMC) and found that the spectra of all three stars show enhanced 13CO band emis- sion, in agreement with theoretical predictions for evolved massive stars. Our preliminary results for the two B[e]SGs seem to indicate that one is a pre-RSG star while the other is in a post-RSG phase.

  20. RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES: KMOS OBSERVATIONS IN NGC 6822

    SciTech Connect

    Patrick, L. R.; Evans, C. J.; Ferguson, A. M. N.; Davies, B.; Kudritzki, R-P.; Gazak, J. Z.; Bergemann, M.; Plez, B.

    2015-04-10

    We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new K-band Multi-Object Spectrograph Very Large Telescope, Chile. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = −0.52 ± 0.21, which agrees well with previous abundance studies of young stars and H ii regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast to recent evolutionary models.

  1. GIANO-TNG spectroscopy of red supergiants in the young star cluster RSGC3

    NASA Astrophysics Data System (ADS)

    Origlia, L.; Oliva, E.; Sanna, N.; Mucciarelli, A.; Dalessandro, E.; Scuderi, S.; Baffa, C.; Biliotti, V.; Carbonaro, L.; Falcini, G.; Giani, E.; Iuzzolino, M.; Massi, F.; Sozzi, M.; Tozzi, A.; Ghedina, A.; Ghinassi, F.; Lodi, M.; Harutyunyan, A.; Pedani, M.

    2016-01-01

    Aims: The Scutum complex in the inner disk of the Galaxy has a number of young star clusters dominated by red supergiants that are heavily obscured by dust extinction and observable only at infrared wavelengths. These clusters are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Methods: During the technical commissioning and as a first science verification of the GIANO spectrograph at the Telescopio Nazionale Galileo, we secured high-resolution (R ≃ 50 000) near-infrared spectra of five red supergiants in the young Scutum cluster RSGC3. Results: Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to measure several tens of atomic and molecular lines that were suitable for determining chemical abundances. By means of spectral synthesis and line equivalent width measurements, we obtained abundances of Fe and iron-peak elements such as Ni, Cr, and Cu, alpha (O, Mg, Si, Ca, Ti), other light elements (C, N, F, Na, Al, and Sc), and some s-process elements (Y, Sr). We found average half-solar iron abundances and solar-scaled [X/Fe] abundance patterns for most of the elements, consistent with a thin-disk chemistry. We found depletion of [C/Fe] and enhancement of [N/Fe], consistent with standard CN burning, and low 12C /13C abundance ratios (between 9 and 11), which require extra-mixing processes in the stellar interiors during the post-main sequence evolution. We also found local standard of rest VLSR = 106 km s-1 and heliocentric Vhel = 90 km s-1 radial velocities with a dispersion of 2.3 km s-1. Conclusions: The inferred radial velocities, abundances, and abundance patterns of RSGC3 are very similar to those previously measured in the other two young clusters of the Scutum complex, RSGC1 and RSGC2, suggesting a common kinematics and chemistry within the Scutum complex.

  2. GIANO-TNG spectroscopy of red supergiants in the young star cluster RSGC2

    NASA Astrophysics Data System (ADS)

    Origlia, L.; Oliva, E.; Maiolino, R.; Mucciarelli, A.; Baffa, C.; Biliotti, V.; Bruno, P.; Falcini, G.; Gavriousev, V.; Ghinassi, F.; Giani, E.; Gonzalez, M.; Leone, F.; Lodi, M.; Massi, F.; Montegriffo, P.; Mochi, I.; Pedani, M.; Rossetti, E.; Scuderi, S.; Sozzi, M.; Tozzi, A.

    2013-12-01

    Aims: The inner disk of the Galaxy has a number of young star clusters dominated by red supergiants that are heavily obscured by dust extinction and observable only at infrared wavelengths. These clusters are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Methods: During the technical commissioning and as a first science verification of the GIANO spectrograph at the Telescopio Nazionale Galileo, we secured high-resolution (R ≃ 50 000) near-infrared spectra of three red supergiants in the young Scutum cluster RSGC2. Results: Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to identify several tens of atomic and molecular lines suitable for chemical abundance determinations. By means of spectral synthesis and line equivalent width measurements, we obtained abundances of Fe and other iron-peak elements such as V, Cr, Ni, of alpha (O, Mg, Si, Ca and Ti) and other light elements (C, N, Na, Al, K, Sc), and of some s-process elements (Y, Sr). We found iron abundances between half and one third solar and solar-scaled [X/Fe] abundance patterns of iron-peak, alpha and most of the light elements, consistent with a thin-disk chemistry. We found a depletion of [C/Fe] and enhancement of [N/Fe], consistent with CN burning, and low 12C/13C abundance ratios (between 9 and 11), requiring extra-mixing processes in the stellar interiors during the post-main-sequence evolution. Finally, we found a slight [Sr/Fe] enhancement and a slight [Y/Fe] depletion (by a factor of ≤2), with respect to solar. Table 3 is available in electronic form at http://www.aanda.org

  3. Model atmospheres for cool supergiant stars.

    NASA Technical Reports Server (NTRS)

    Alexander, D. R.; Johnson, H. R.

    1972-01-01

    The results of an exploratory grid of model atmospheres for cool giant stars are used to illustrate the effect of varying the chemical composition of the atmosphere. The effects of composition changes (depletion of C and O, enrichment of N, and increase in the ratio C/O), which might be expected from processing of the original material of a star through the CNO cycle of nuclear burning, are studied. The models also include the important CN opacity. They are illustrated by giving several representative T-P and T-tau diagrams, spectral energy curves, and column density tables of molecules.

  4. The blue supergiant MN18 and its bipolar circumstellar nebula

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Bestenlehner, J. M.; Bodensteiner, J.; Langer, N.; Greiner, J.; Grebel, E. K.; Berdnikov, L. N.; Beletsky, Y.

    2015-11-01

    We report the results of spectrophotometric observations of the massive star MN18 revealed via discovery of a bipolar nebula around it with the Spitzer Space Telescope. Using the optical spectrum obtained with the Southern African Large Telescope, we classify this star as B1 Ia. The evolved status of MN18 is supported by the detection of nitrogen overabundance in the nebula, which implies that it is composed of processed material ejected by the star. We analysed the spectrum of MN18 by using the code CMFGEN, obtaining a stellar effective temperature of ≈21 kK. The star is highly reddened, E(B - V) ≈ 2 mag. Adopting an absolute visual magnitude of MV = -6.8 ± 0.5 (typical of B1 supergiants), MN18 has a luminosity of log L/L⊙ ≈ 5.42 ± 0.30, a mass-loss rate of ≈(2.8-4.5) × 10- 7 M⊙ yr- 1, and resides at a distance of ≈5.6^{+1.5} _{-1.2} kpc. We discuss the origin of the nebula around MN18 and compare it with similar nebulae produced by other blue supergiants in the Galaxy (Sher 25, HD 168625, [SBW2007] 1) and the Large Magellanic Cloud (Sk-69°202). The nitrogen abundances in these nebulae imply that blue supergiants can produce them from the main-sequence stage up to the pre-supernova stage. We also present a K-band spectrum of the candidate luminous blue variable MN56 (encircled by a ring-like nebula) and report the discovery of an OB star at ≈17 arcsec from MN18. The possible membership of MN18 and the OB star of the star cluster Lynga 3 is discussed.

  5. THE YELLOW AND RED SUPERGIANTS OF M33

    SciTech Connect

    Drout, Maria R.; Massey, Philip; Meynet, Georges E-mail: phil.massey@lowell.edu

    2012-05-10

    Yellow and red supergiants are evolved massive stars whose numbers and locations on the Hertzsprung-Russell (H-R) diagram can provide a stringent test for models of massive star evolution. Previous studies have found large discrepancies between the relative number of yellow supergiants (YSGs) observed as a function of mass and those predicted by evolutionary models, while a disagreement between the predicted and observed locations of red supergiants (RSGs) on the H-R diagram was only recently resolved. Here, we extend these studies by examining the YSG and RSG populations of M33. Unfortunately, identifying these stars is difficult as this portion of the color-magnitude diagram is heavily contaminated by foreground dwarfs. We identify the RSGs through a combination of radial velocities and a two-color surface gravity discriminant, and after re-characterizing the rotation curve of M33 with our newly selected RSGs, we identify the YSGs through a combination of radial velocities and the strength of the O I {lambda}7774 triplet. We examine {approx}1300 spectra in total and identify 121 YSGs (a sample that is unbiased in luminosity above log (L/L{sub Sun }) {approx} 4.8) and 189 RSGs. After placing these objects on the H-R diagram, we find that the latest generation of Geneva evolutionary tracks shows excellent agreement with the observed locations of our RSGs and YSGs, the observed relative number of YSGs with mass, and the observed RSG upper mass limit. These models therefore represent a drastic improvement over previous generations.

  6. The Red Supergiant Content of the LMC and SMC

    NASA Astrophysics Data System (ADS)

    Evans, Kate Anne; Massey, Philip

    2017-01-01

    We have investigated the red supergiant (RSG) population of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) through a radial velocity survey of 309 candidate RSGs in the LMC and 356 in the SMC, confirming the presence of 304 RSG in the LMC and 316 in the SMC. Using these spectra, we have measured effective temperatures and spectral types for each confirmed RSG. These data allow us to compare our sample of stars with the Geneva model evolutionary tracks. This work has been partially supported by the National Science Foundation AST-1612874.

  7. Magnetic main sequence stars as progenitors of blue supergiants

    NASA Astrophysics Data System (ADS)

    Petermann, I.; Castro, N.; Langer, N.

    2015-01-01

    Blue supergiants (BSGs) to the right the main sequence band in the HR diagram can not be reproduced by standard stellar evolution calculations. We investigate whether a reduced convective core mass due to strong internal magnetic fields during the main sequence might be able to recover this population of stars. We perform calculations with a reduced mass of the hydrogen burning convective core of stars in the mass range 3-30 M ⊙ in a parametric way, which indeed lead to BSGs. It is expected that these BSGs would still show large scale magnetic fields in the order of 10 G.

  8. On the atmospheric structure and fundamental parameters of red supergiants

    NASA Astrophysics Data System (ADS)

    Wittkowski, M.; Arroyo-Torres, B.; Marcaide, J. M.; Abellan, F. J.; Chiavassa, A.; Freytag, B.; Scholz, M.; Wood, P. R.; Hauschildt, P. H.

    2015-01-01

    We present near-infrared spectro-interferometric studies of red supergiant (RSG) stars using the VLTI/AMBER instrument, which are compared to previously obtained similar observations of AGB stars. Our observations indicate spatially extended atmospheric molecular layers of water vapor and CO, similar as previously observed for Mira stars. Data of VY~CMa indicate that the molecular layers are asymmetric, possibly clumpy. Thanks to the spectro-interferometric capabilities of the VLTI/AMBER instrument, we can isolate continuum bandpasses, estimate fundamental parameters of our sources, locate them in the HR diagram, and compare their positions to recent evolutionary tracks. For the example of VY CMa, this puts it close to evolutionary tracks of initial mass 25-32 M ⊙. Comparisons of our data to hydrostatic model atmospheres, 3d simulations of convection, and 1d dynamic model atmospheres based on self-excited pulsation models indicate that none of these models can presently explain the observed atmospheric extensions for RSGs. The mechanism that levitates the atmospheres of red supergiant is thus a currently unsolved problem.

  9. The ultraviolet variability of early-type supergiants

    NASA Technical Reports Server (NTRS)

    Underhill, A. B.

    1984-01-01

    Four early-type supergiants - HD 79186 (B5 Ia), HD 96919 (B9 Ia), HD 105056 (ON9.7 Iae), and HD 148379 (B2 Iae) - have been observed with the low-resolution spectrographs of IUE in the large aperture on 14 days. The behavior of the ultraviolet fluxes with time is studied. The light from all four stars seems to vary. Typically the dispersion about the mean magnitude at any wavelength corresponds to + or - 0.085, + or - 0.080, + or - 0.101, and + or - 0.106 mag, respectively. These amplitudes exceed the typical uncertainty in an IUE measurement of flux by about a factor of 3; they are somewhat larger than the variations known in the visible wavelength range. There are insufficient data to investigate periodicity in the observed light changes. The effective temperatures and angular diameters of the stars have been estimated using the present ultraviolet photometry, published UBV and uvby photometry, and the model-atmosphere fluxes reported by Kurucz in 1979. The program stars have dimensions typical for their spectral types. A brief discussion is given of possible causes of the variability of hot supergiants.

  10. B[e] Supergiants' Circumstellar Environment: Disks or Rings?

    NASA Astrophysics Data System (ADS)

    Maravelias, G.; Kraus, M.; Aret, A.; Cidale, L.; Arias, M. L.; Borges Fernandes, M.

    2017-02-01

    B[e] supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dust regions usually found in rings or disk-like structures. However, the detailed structure and the formation of the circumstellar environment are not well-understood, requiring further investigation. To address that we initiated an observing campaign to obtain a homogeneous set of high-resolution spectra in both the optical and NIR (using MPG-ESO/FEROS, GEMINI /Phoenix and VLT/CRIRES, respectively). We monitor a number of Galactic B[e] supergiants, for which we examined the [O I] and [Ca II] emission lines and the bandheads of the CO and SiO molecules to probe the structure and the kinematics of their formation regions. We find that the emission from each tracer forms either in a single or multiple equatorial rings.

  11. The Red Supergiants of M33: Determining Physical Properties

    NASA Astrophysics Data System (ADS)

    Beck, Madeleine; Massey, Philip

    2017-01-01

    We investigate a sample of red supergiants in the nearby unbarred spiral galaxy M33 with the goals of (1) determining the physical properties of these stars, (2) understanding the effects of metallicity on massive star evolution, and (3) comparing results to current models proposed by the Geneva group. M33 provides an ideal environment in which to conduct this examination because of a gradient of metallicity within its disk as well as its proximity to the Milky Way, which allows us to observe a complete sample of red supergiants. We employ MARCS atmosphere models and fit spectral features of our stars to determine effective temperatures and spectral types, then we use this information in combination with photometry to calculate bolometric luminosities. After placing these objects on the H-R diagram, we notice some discrepancies with what the Geneva solar-metallicity evolutionary tracks (Ekstrom et al. 2012) predict, namely that the tracks may not extend to cool enough temperatures and high enough luminosities and masses to comply with what we see observationally. We propose this may be the result of a mismatch between M33’s metallicity and the solar-metallicity Geneva models; we hope to make comparisons in the future as these new evolutionary tracks become available. This work was supported by the NSF through grant numbers AST-1461200 and AST-1612874.

  12. YELLOW AND RED SUPERGIANTS IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Neugent, Kathryn F.; Massey, Philip; Skiff, Brian; Meynet, Georges E-mail: phil.massey@lowell.edu E-mail: georges.meynet@unige.ch

    2012-04-20

    Due to their transitionary nature, yellow supergiants (YSGs) provide a critical challenge for evolutionary modeling. Previous studies within M31 and the Small Magellanic Cloud show that the Geneva evolutionary models do a poor job at predicting the lifetimes of these short-lived stars. Here, we extend this study to the Large Magellanic Cloud (LMC) while also investigating the galaxy's red supergiant (RSG) content. This task is complicated by contamination by Galactic foreground stars that color and magnitude criteria alone cannot weed out. Therefore, we use proper-motions and the LMC's large systemic radial velocity ({approx}278 km s{sup -1}) to separate out these foreground dwarfs. After observing nearly 2000 stars, we identified 317 probable YSGs, 6 possible YSGs, and 505 probable RSGs. Foreground contamination of our YSG sample was {approx}80%, while that of the RSG sample was only 3%. By placing the YSGs on the Hertzsprung-Russell diagram and comparing them against the evolutionary tracks, we find that new Geneva evolutionary models do an exemplary job at predicting both the locations and the lifetimes of these transitory objects.

  13. Clump Accretion in Supergiant Fast X-Ray Transients

    NASA Astrophysics Data System (ADS)

    Chase, Eve; Raymer, E.; Blondin, J. M.

    2014-01-01

    Supergiant Fast X-Ray Transients (SFXTs) are a subclass of High-Mass X-Ray Binaries that consist of a neutron star and OB supergiant donor star. These systems display short, bright x-ray flares lasting a few minutes to a few hours with luminosities reaching 1036 erg/s, several orders of magnitude larger than the quiescent luminosities of 1032 erg/s. The clumpy wind hypothesis has been proposed as a possible mechanism for these transient flares; in this model, a portion of the stellar wind from the donor star forms into clumps and is accreted onto the neutron star, inducing flares. We use high-resolution 3D hydrodynamic simulations to test the clumpy wind hypothesis, tracking the mass and angular momentum accretion rates to infer properties of the resulting x-ray flare and secular evolution of the neutron star rotation. Our results are significantly different from the predictions of Hoyle-Lyttleton Accretion (HLA) theory, which assume steady, laminar, axisymmetric flow. For example, an off-axis clump initiated with an impact parameter greater than the clump radius (for which HLA predicts no effect) produces a small spike in mass accretion and induces a long period of disk-like flow that dramatically reduces the accretion rate below the steady HLA value. The result is a brief, weak flare with a net decrease in total accreted mass compared with steady wind accretion accompanied by a substantial accretion of angular momentum.

  14. Spectroscopic and photometric observations of M supergiants in Carina.

    NASA Technical Reports Server (NTRS)

    Humphreys, R. M.; Strecker, D. W.; Ney, E. P.

    1972-01-01

    Spectroscopic study of 30 Southern-Hemisphere M supergiants mostly in Carina in the blue and near-infrared, and photometrical study of these stars from 0.4 to 18 microns. The uncertainties in the determinations of interstellar extinction are discussed, and the spatial distribution of the M supergiants in the Carina arm is shown. The presence of the 11-micron excess attributed to silicate dust is a common feature. Stars of the same spectral type and luminosity class are remarkably homogeneous in their long-wave behavior. The silicate feature becomes more prominent in the more luminous stars and in stars of later spectral type. Four composite systems show little long-wave excess. The two VV Cephei objects have excesses probably produced by gas emission, and the other two have little or no excess - supporting the suggestion that the presence of the early star prohibits the formation of a dust envelope. Three stars - VY CMa, VX Sgr, and HD 9767 - appear to be extreme examples of stars with large excesses over the entire long-wave region. It is suggested that these objects are surrounded by large amounts of particulate material over a great range of distances from the stars.

  15. Detection of a red supergiant progenitor star of a type II-plateau supernova.

    PubMed

    Smartt, Stephen J; Maund, Justyn R; Hendry, Margaret A; Tout, Christopher A; Gilmore, Gerard F; Mattila, Seppo; Benn, Chris R

    2004-01-23

    We present the discovery of a red supergiant star that exploded as supernova 2003gd in the nearby spiral galaxy M74. The Hubble Space Telescope (HST) and the Gemini Telescope imaged this galaxy 6 to 9 months before the supernova explosion, and subsequent HST images confirm the positional coincidence of the supernova with a single resolved star that is a red supergiant of 8(+4)(-2) solar masses. This confirms both stellar evolution models and supernova theories predicting that cool red supergiants are the immediate progenitor stars of type II-plateau supernovae.

  16. Spectroscopic Analysis of the Supergiant Star HD 54605

    NASA Astrophysics Data System (ADS)

    Peña, L.; Rosenzweig, P.; Guzmán, E.; Hearnshaw, J.

    2009-05-01

    The main purpose of the present study is to analyze a high resolution spectrum of the supergiant star HD 54605, obtained in the year 2003, with a CCD coupled with the spectrograph HERCULES, attached to the 1m reflector telescope of Mt. John Observatory of the University of Canterbury (New Zealand). This spectrum covers the region λλ ≈ 4505-7080Å, with R = 41000 and a dispersion of ≈ 2Å/mm. According to previous spectroscopic observations, of low dispersion, the radial velocity of this star showed that it does not vary in periods of time relatively short. Until the present, we have identified five hundred photospheric lines, from which, with no doubt, we will obtain a satisfactory result that will give an important contribution to the database of the values of the radial velocity of HD 54605. We observe that Hβ, shows a relatively wide and deep profile and is in complete absorption.

  17. Quantitative spectroscopy of OB stars: from dwarfs to supergiants

    NASA Astrophysics Data System (ADS)

    Przybilla, N.; Nieva, M. F.; Firnstein, M.; Butler, K.

    2013-02-01

    We discuss recent progress made in the spectral modelling of OB stars from the main sequence to evolved phases as BA-type supergiants. Non-LTE line-formation computations can now reproduce observed spectra over the entire optical and near-IR wavelength range with high confidence, facilitating stellar atmospheric parameters and elemental abundances to be determined at high accuracy and precision. An overview is given how the fundamental stellar parameters of single stars determined in our new approach compare to high-precision data derived from detached eclipsing massive binary stars. Finally, the observational constraints for a sample of Galactic objects are put in context with state-of-the-art evolution models for rotating massive stars.

  18. Identification of Red Supergiants in the Magellanic Clouds.

    NASA Astrophysics Data System (ADS)

    Barandi, Brian Allan; Massey, Philip; Levesque, Emily M.

    2015-01-01

    The number and characteristics of red supergiants (RSGs) in the low metallicity environment of the Large and Small Magellanic Clouds (LMC, SMC) provide tests of stellar evolutionary tracks for massive stars. One complication is identifying Magellanic members due to the contamination of foreground stars in the Milky Way. We used the colors and magnitudes from the 2MASS survey to identify RSG candidates in the LMC and SMC, and used the Anglo Australian Telescope coupled with the AAOmega spectrograph to take spectra of 325 LMC and 423 SMC RSG candidates. Using the Ca II triplet, we measured the radial velocity of each candidate by cross correlation and assigned membership. Methods along with physical properties of each star will be presented. We gratefully acknowledge support by the National Science Foundation through the REU program at Lowell Observatory and Northern Arizona University (AST-1004107) and through PM's grant AST-1008020.

  19. Long-term spectropolarimetric monitoring of the cool supergiant betelgeuse

    NASA Astrophysics Data System (ADS)

    Bedecarrax, I.; Petit, P.; Aurière, M.; Grunhut, J.; Wade, G.; Chiavassa, A.; Donati, J.-F.; Konstantinova-Antova, R.; Perrin, G.

    2013-05-01

    We report on a long-term monitoring of the cool supergiant Betelgeuse, using the NARVAL and ESPaDOnS high-resolution spectropolarimeters, respectively installed at Telescope Bernard Lyot (Pic du Midi Observatory, France) and at the Canada-France-Hawaii Telescope (Mauna Kea Observatory, Hawaii). The data set, constituted of circularly polarized (Stokes V) and intensity (Stokes I) spectra, was collected between 2010 and 2012. We investigate here the temporal evolution of magnetic field, convection and temperature at photospheric level, using simultaneous measurements of the longitudinal magnetic field component, the core emission of the Ca II infrared triplet, the line-depth ratio of selected photospheric lines and the radial velocity of the star.

  20. Spectroscopic Diagnostics for Circumstellar Disks of B[e] Supergiants

    NASA Astrophysics Data System (ADS)

    Kraus, M.

    2017-02-01

    B[e] supergiants (B[e]SGs) are emission-line objects, presumably in a short-lived phase in the post-main sequence evolution of massive stars. Their intense infrared excess emission indicates large amounts of warm circumstellar dust. It has long been assumed that the stars possess an aspherical wind consisting of a classical line-driven wind in the polar direction and a dense, slow equatorial wind dubbed outflowing disk. The general properties obtained for these disks are in line with this scenario, although current theories have considerable difficulties reproducing the observed quantities. Therefore, more sophisticated observational constraints are needed. These follow from combined optical and infrared spectroscopic studies, which delivered the surprising result that the circumstellar material of B[e]SGs is concentrated in multiple rings revolving the stars on stable Keplerian orbits. Such a scenario requires new ideas for the formation mechanism where pulsations might play an important role.

  1. Searching for supergiant fast X-ray transients with Swift

    NASA Astrophysics Data System (ADS)

    Romano, P.; Bozzo, E.; Esposito, P.; Sbarufatti, B.; Haberl, F.; Ponti, G.; D'Avanzo, P.; Ducci, L.; Segreto, A.; Jin, C.; Masetti, N.; Del Santo, M.; Campana, S.; Mangano, V.

    2016-09-01

    Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) hosting a neutron star and an OB supergiant companion. We examine the available Swift data, as well as other new or archival/serendipitous data, on three sources: IGR J17407-2808, 2XMM J185114.3-000004, and IGR J18175-2419, whose X-ray characteristics qualify them as candidate SFXT, to explore their properties and test whether they are consistent with an SFXT nature. Since IGR J17407-2808 and 2XMM J185114.3-000004 triggered the Burst Alert Telescope on board Swift, the Swift data enable us to provide their first arcsecond localisations, leading to an unequivocal identification of the source CXOU J174042.0-280724 as the soft X-ray counterpart of IGR J17407-2808, as well as their first broadband spectra, which can be fit with models generally describing accreting neutron stars in HMXBs. While still lacking optical spectroscopy to assess the spectral type of the companion, we propose 2XMM J185114.3-000004 as a very strong SFXT candidate. The nature of IGR J17407-2808 remains, instead, more uncertain. Its broadband properties cannot exclude the fact that the emission originates from either an HMXB (and in that case, an SFXT) or, more likely, a low-mass X-ray binary. Finally, based on the deep non-detection in our XRT monitoring campaign and a careful reanalysis of the original INTEGRAL data in which the discovery of the source was first reported, we show that IGR J18175-2419 is likely a spurious detection.

  2. Red Supergiants in the Inner Galaxy: Stellar Properties

    NASA Astrophysics Data System (ADS)

    Messineo, Maria; Zhu, Qingfeng; Menten, Karl M.; Ivanov, Valentin D.; Figer, Donald F.; Kudritzki, Rolf-Peter; Chen, C.-H. Rosie

    2017-02-01

    Red supergiants (RSGs) are luminous cool stars detectable in disks of distant spirals. About a thousand are known in the Galaxy. Here, we analyze a sample of late-type stars recently observed by Messineo et al. in the inner Galaxy (10^\\circ < l< 60^\\circ ). A total of 58 targets (25% of previously known RSGs) were reported as supergiants based on their large equivalent widths of the CO band-head at 2.293 μm (EWs > 45 Å, ≳M0I). In this work, luminosities are estimated with infrared measurements and distance moduli for 47 spectroscopically classified RSGs; they range from 3.2× {10}4 to 1.3× {10}5 {L}ȯ . Six other RSGs with smaller EW(CO)s are classified according to their luminosities. Using a prescription based on {K}{{s}}{--}[W4], moderate mass-loss rates from 10‑8 to {10}-6.5 {M}ȯ yr‑1 are inferred. In addition, we report on H and K spectra of 26 stars at R = 1500–2200. EWs of the CO at 2.293 and 1.620 μm, and of atomic lines, are consistent with those of nearby RSGs, within uncertainties. Mg i appears to be a useful diagnostic to confirm RSGs at R = 1500–2200. RSG #66 is a member of the cluster Alicante 7. Star #92 is projected onto the overdensity #495 of Camargo et al., but our analysis suggests they are unrelated. Remaining targets are isolated from other known RSGs within ≈3‧.

  3. Variability and mass loss in IA O-B-A supergiants

    NASA Technical Reports Server (NTRS)

    Schild, R. E.; Garrison, R. F.; Hiltner, W. A.

    1983-01-01

    Recently completed catalogs of MK spectral types and UBV photometry of 1227 OB stars in the southern Milky Way have been analyzed to investigate brightness and color variability among the Ia supergiants. It is found that brightness variability is common among the O9-B1 supergiants with typical amplitudes about 0.1 and time scales longer than a week and shorter than 1000 days. Among the A supergiants fluctuations in U-B color are found on similar time scales and with amplitude about 0.1. For many early Ia supergiants there is a poor correlation between Balmer jump and spectral type, as had been known previously. An attempt to correlate the Balmer jump deficiency with mass loss rate yielded uncertain results.

  4. The energy distributions of B supergiants in the Large Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Edward L.

    1986-01-01

    It is shown that line-blanketed, LTE, plane-parallel model atmosphere calculations provide excellent fits to the ultraviolet-through-visual energy distributions of B supergiants in the Large Magellanic Cloud. The models were computed using Kurucz's (1979) ATLAS atmosphere program, but with lower gravities than were contained in Kurucz's published model grid. The ultraviolet continua of low gravity stars are found to be sensitive to changes in temperature and gravity. Measurements of Teff and log g for ten LMC B supergiants from model atmosphere fits to the energy distributions yield estimates of their radii, luminosities, and masses. Model atmosphere fits suggest that the late B supergiants have significantly lower masses than the earlier B types of the same luminosity, contrary to stellar evolution theory which predicts that B supergiants are in a post-core hydrogen burning phase and should evolve very quickly and at essentially constant mass.

  5. THE DUSTY CIRCUMSTELLAR DISKS OF B[e] SUPERGIANTS IN THE MAGELLANIC CLOUDS

    SciTech Connect

    Kastner, Joel H.; Buchanan, Catherine; Sahai, Raghvendra; Sargent, Benjamin A. E-mail: clb@unimelb.edu.a

    2010-05-15

    To better ascertain the nature of the infrared excesses that are characteristic of B[e] supergiants, we obtained Spitzer IRS spectroscopy and IRAC/MIPS imaging for a sample of nine B[e] supergiant stars in the Magellanic Clouds. We find that all nine stars display mid- to far-IR spectral and spatial characteristics indicative of the presence of circumstellar dust disks. Several of the sample B[e] supergiants display crystalline silicate features in their IRS spectra, consistent with grain processing in long-lived (i.e., orbiting) disks. Although it is possible that these disks are primordial in origin, large shell structures (with size scales of tens of parsec) are associated with five of the nine B[e] supergiants, suggesting that mass loss has provided the circumstellar material now orbiting these stars. Hence-via analogy to the class of post-asymptotic giant branch stars with binary companions and dusty, circumbinary disks-we speculate that B[e] supergiant stars may be post-red supergiants in binary systems with orbiting, circumbinary disks that are derived from post-main-sequence mass loss.

  6. The AG Carinae nebula: abundant evidence for a red supergiant progenitor?

    NASA Astrophysics Data System (ADS)

    Smith, L. J.; Stroud, M. P.; Esteban, C.; Vilchez, J. M.

    1997-09-01

    AG Carinae is a massive, evolved supergiant which is thought to be in transition from an O star to a Wolf-Rayet (WR) star and is currently identified as a luminous blue variable (LBV) with logL/solar=6.0. We present an abundance study of the ejecta nebula surrounding AG Car with the aim of elucidating the evolutionary history of the central star. Physical parameters and abundances are derived for five regions across the nebula from high spatial resolution spectroscopy obtained at the Anglo-Australian Telescope (AAT). We derive an average T_e of 6350+/-400K, an n_e of 820+/-170cm^-3, and find that nitrogen (N) is enhanced by a factor of 4.5+/-1.3 and that oxygen (O) is deficient by a factor of 15.1+/-7.2. The derived abundances are compared with those determined for ejecta-type nebulae around WR stars and those predicted by hydrodynamical calculations and stellar evolutionary models. We find that the AG Car nebula is composed of mildly processed material that has not reached the CNO-equilibrium abundances predicted for LBV nebulae. The similarity of the AG Car nebular N abundance to WR nebulae leads us to suggest that the nebulae were ejected at the same evolutionary point, and have undergone no further chemical modification. For AG Car, this point appears to have occurred before the LBV phase because of the observed low N enrichment. Comparison of the observed N abundance with evolutionary model predictions indicates that the AG Car nebula may represent the hydrogen-rich (H- rich) envelope of a red supergiant (RSG). The problem of an RSG progenitor for AG Car is discussed and it is found that the LBV model of Stothers & Chin, incorporating a brief unstable RSG phase, is capable of explaining the observations. We conclude that despite its high luminosity, AG Car has probably experienced a brief RSG phase where it ejected its outer layers to form the currently observed nebula.

  7. On The Explosion Geometry of Red Supergiant Stars

    NASA Astrophysics Data System (ADS)

    Leonard, Douglas C.; Supernova Spectropolarimetry Project (SNSPOL)

    2016-06-01

    From progenitor studies, type II-Plateau supernovae (SNe II-P) have been decisively and uniquely determined to arise from isolated red supergiant (RSG) stars, establishing the most homogeneous --- and well understood --- progenitor class of any type of core-collapse supernova. The physical process by which these stars explode, however, remains a mystery. A fundamental clue to the nature of the explosion mechanism is explosion geometry: In short, are supernovae round? Because young supernova atmospheres are electron-scattering dominated, their net linear polarization provides a direct probe of early-time supernova geometry, with higher degrees of polarization generally indicating greater departures from spherical symmetry. This presentation will describe the ongoing work being carried out on RSG explosion geometry by the SuperNova SpectroPOLarimetry project (SNSPOL), with a particular focus on SN 2013ej -- an SN II-P that exhibited remarkably high polarization just days after the explosion, and for which twelve epochs of spectropolarimetry trace an intriguing tale about its geometry deep into the nebular phase.We acknowledge support from NSF grants AST-1009571 and AST-1210311, under which part of this research was carried out.

  8. Supernovae from yellow, blue supergiants: origin and consequences for stellar evolution

    NASA Astrophysics Data System (ADS)

    Meynet, Georges; Georgy, Cyril; Saio, Hideyuki; Kudritzki, Rolf-Peter; Groh, Jose

    2015-08-01

    A few core collapse supernovae progenitors have been found to be yellow or blue supergiants. We shall discuss possible scenarios involving single and close binary evolution allowing to explain this kind of core collapse supernova progenitors. According to stellar models for both single and close binaries, blue supergiants, at the end of their nuclear lifetimes and thus progenitors of core collapse supernovae, present very different characteristics for what concerns their surface compositions, rotational surface velocities and pulsational properties with respect to blue supergiants in their core helium burning phase. We discuss how the small observed scatter of the flux-weighted gravity-luminosity (FWGL) relation of blue supergiants constrains the evolution of massive stars after the Main-Sequence phase and the nature of the progenitors of supernovae in the mass range between 12 and 40 solar masses. The present day observed surface abundances of blue supergiants, of their pulsational properties, as well as the small scatter of the FWGL relation provide strong constraints on both internal mixing and mass loss in massive stars and therefore on the end point of their evolution.

  9. On the Explosion Geometry of Red Supergiant Stars

    NASA Astrophysics Data System (ADS)

    Leonard, Douglas Christopher; Dessart, Luc; Pignata, Giuliano; Hillier, D. John; Williams, George Grant; Smith, Paul S.; Khandrika, Harish; Bilinski, Christopher; Duong, Nhieu; Flatland, Kelsi; Gonzalez, Luis; Hoffman, Jennifer L.; Horst, Chuck; Huk, Leah; Milne, Peter; Rachubo, Alisa A.; Smith, Nathan

    2015-08-01

    From progenitor studies, type II-Plateau supernovae (SNe II-P) have been decisively and uniquely determined to arise from isolated red supergiant (RSG) stars with initial masses ranging from 8 to 16 solar masses (Smartt 2009), establishing the most homogeneous -- and well understood -- progenitor class of any type of core-collapse supernova. However, we must admit a fundamental truth: We do not know how these stars explode. A basic discriminant among proposed explosion models is explosion geometry, since some models predict severe distortions from spherical symmetry. A primary method to gain such geometric information is through spectropolarimetry of the expanding (but, unresolved) atmosphere, with higher degrees of linear polarization generally demanding larger departures from spherical symmetry. Initially, as a class, SNe II-P were found to be only weakly polarized at the early epochs observed, suggesting a nearly spherical explosion for RSG stars. However, late-time observations of SN 2004dj captured a dramatic spike in polarization at just the moment the "inner core" of the ejecta was first revealed in this SN II-P (i.e., at the "drop" off of the photometric plateau; Leonard et al. 2006). This raised the possibility that the explosion of RSGs might be driven by a strongly non-spherical mechanism, with the evidence for the asphericity cloaked at early times by the massive, opaque, quasi-spherical hydrogen envelope. In this presentation we shall describe the continuing work on the explosion geometry of RSGs being carried out by the SuperNova SpectroPOLarimetry project (SNSPOL), with a particular focus on SN 2013ej -- an SN II-P that exhibited remarkably high polarization just days after the explosion (Leonard et al. 2013), and for which twelve epochs of spectropolarimetry trace an intriguing tale about its geometry deep into the nebular phase. We acknowledge support from NSF grants AST-1009571 and AST-1210311, under which part of this research was carried out.

  10. Supergiant X-Ray Binaries Observed by Suzaku

    NASA Technical Reports Server (NTRS)

    Bodaghee, A.; Tomsick, J. A.; Rodriquez, J.; Chaty, S.; Pottschmidt, K.; Walter, R.; Romano, P.

    2011-01-01

    Suzaku observations are presented for the high-mass X-ray binaries IGR 116207-5129 and IGR 117391-3021. For IGR 116207-5129, we provide the first X-ray broadband (0.5-60 keV) spectrum from which we confirm a large intrinsic column density (N(sub H) = 1.6 x 10(exp 23)/sq cm), and we constrain the cutoff energy for the first time (E(sub cut) = 19 keV). A prolonged (> 30 ks) attenuation of the X-ray flux was observed which we tentatively attribute to an eclipse of the probable neutron star by its massive companion, in a binary system with an orbital period between 4 and 9 days, and inclination angles> 50 degrees. For IGRJ17391-3021, we witnessed a transition from quiescence to a low-activity phase punctuated by weak flares whose peak luminosities in the 0.5-10keV band are only a factor of 5 times that of the pre-flare emission. These micro flares are accompanied by an increase in NH which suggests the accretion of obscuring clumps of wind. We now recognize that these low-activity epochs constitute the most common emission phase for this system, and perhaps in other supergiant fast X-ray transients (SFXTs) as well. We close with an overview of our upcoming program in which Suzaku will provide the first ever observation of an SFXT (IGRJ16479-4514) during a binary orbit enabling us to probe the accretion wind at every phase.

  11. The evolution of red supergiants to supernova in NGC 2100

    NASA Astrophysics Data System (ADS)

    Beasor, Emma R.; Davies, Ben

    2016-12-01

    The mass-loss rates of red supergiants (RSGs) govern their evolution towards supernova and dictate the appearance of the resulting explosion. To study how mass-loss rates change with evolution, we measure the mass-loss rates (dot{M}) and extinctions of 19 RSGs in the young massive cluster NGC 2100 in the Large Magellanic Cloud. By targeting stars in a coeval cluster, we can study the mass-loss rate evolution whilst keeping the variables of mass and metallicity fixed. Mass-loss rates were determined by fitting DUSTY models to mid-IR photometry from WISE and Spitzer/IRAC. We find that the dot{M} in RSGs increases as the star evolves, and is well described by dot{M} prescription of de Jager, used widely in stellar evolution calculations. We find that the extinction caused by the warm dust is negligible, meaning the warm circumstellar material of the inner wind cannot explain the higher levels of extinction found in the RSGs compared to other cluster stars. We discuss the implications of this work in terms of supernova progenitors and stellar evolution theory. We argue that there is little justification for substantially increasing the dot{M} during the RSG phase, as has been suggested recently in order to explain the absence of high-mass Type IIP supernova progenitors. We also argue that an increase in reddening towards the end of the RSG phase, as observed for the two most evolved cluster stars, may provide a solution to the RSG problem.

  12. Two Cases of Super-Giant Coronary Aneurysms after Kawasaki Disease

    PubMed Central

    Lee, Joowon; Kwon, Bo Sang; Bae, Eun Jung; Noh, Chung Il

    2014-01-01

    Acute giant coronary aneurysm after Kawasaki disease (KD) is a catastrophic complication that can be fatal and very difficult to manage. However, no fixed consensus has been reached for the management of super-giant coronary aneurysms in the acute setting. Here, we report the successful management of young children with super-giant coronary aneurysms after KD. Based on our experience, hemodynamic stabilization to prevent further coronary dilation or rupture and strict anticoagulation to avoid thrombus formation are mandatory in the management of this condition. PMID:24497892

  13. The galatic and LMC extreme line supergiants compared: IUE observations of the Henize-Carlson and Zoo star samples of massive supergiants. [Large Magellanic cloud (LMC)

    NASA Technical Reports Server (NTRS)

    Shore, S. N.; Sanduleak, N.; Brown, D. N.; Sonneborn, G.; Bopp, B. W.; Robinson, C. R.

    1988-01-01

    The Henize-Carlson sample of galactic massive supergiants, and a comparison between the Galactic and LMC samples are discussed. Several of the stars, notably He3-395 and S 127/LMC, have very similar shell characteristics. There appears to be little difference, other than luminosity, between the LMC and Galactic samples. One star, He3-1482, was detected with the Very Large Array at 6 cm. The UV data is combined with IRAS and optical information.

  14. SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR

    SciTech Connect

    Van Dyk, Schuyler D.; Elias-Rosa, Nancy; and others

    2012-01-15

    We have obtained limited photometric and spectroscopic data for supernova (SN) 2008bk in NGC 7793, primarily at {approx}> 150 days after explosion. We find that it is a Type II-Plateau (II-P) SN that most closely resembles the low-luminosity SN 1999br in NGC 4900. Given the overall similarity between the observed light curves and colors of SNe 2008bk and 1999br, we infer that the total visual extinction to SN 2008bk (A{sub V} = 0.065 mag) must be almost entirely due to the Galactic foreground, similar to what has been assumed for SN 1999br. We confirm the identification of the putative red supergiant (RSG) progenitor star of the SN in high-quality g'r'i' images we had obtained in 2007 at the Gemini-South 8 m telescope. Little ambiguity exists in this progenitor identification, qualifying it as the best example to date, next to the identification of the star Sk -69 Degree-Sign 202 as the progenitor of SN 1987A. From a combination of photometry of the Gemini images with that of archival, pre-SN, Very Large Telescope JHK{sub s} images, we derive an accurate observed spectral energy distribution (SED) for the progenitor. We find from nebular strong-intensity emission-line indices for several H II regions near the SN that the metallicity in the environment is likely subsolar (Z Almost-Equal-To 0.6 Z{sub Sun }). The observed SED of the star agrees quite well with synthetic SEDs obtained from model RSG atmospheres with effective temperature T{sub eff} = 3600 {+-} 50 K. We find, therefore, that the star had a bolometric luminosity with respect to the Sun of log (L{sub bol}/L{sub Sun} ) = 4.57 {+-} 0.06 and radius R{sub *} = 496 {+-} 34 R{sub Sun} at {approx}6 months prior to explosion. Comparing the progenitor's properties with theoretical massive-star evolutionary models, we conclude that the RSG progenitor had an initial mass in the range of 8-8.5 M{sub Sun }. This mass is consistent with, albeit at the low end of, the inferred range of initial masses for SN II

  15. The Curious Case of the Alpha Persei Corona: A Dwarf in Supergiant's Clothing?

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    2011-09-01

    Alpha Persei (HD 20902: F5 Iab) is a luminous, nonvariable supergiant located at the blue edge of the Cepheid instability strip. It is one of the brightest coronal X-ray sources in the young open cluster bearing its name, yet warm supergiants as a class generally avoid conspicuous high-energy activity. The Cosmic Origins Spectrograph on the Hubble Space Telescope has recently uncovered additional oddities. The 1290-1430 Å far-ultraviolet (FUV) spectrum of α Per is dominated by photospheric continuum emission, with numerous superposed absorption features, mainly stellar. However, the normal proxies of coronal activity, such as the Si IV 1400 Å doublet (T ~ 8 × 104 K), are very weak, as are the chromospheric C II 1335 Å multiplet (T ~ 3 × 104 K) and O I 1305 Å triplet. In fact, the Si IV features of α Per are not only narrower than those of later, G-type supergiants of similar L X/L bol, but are also fainter (in L Si IV /L bol) by two orders of magnitude. Further, a reanalysis of the ROSAT pointing on α Per finds the X-ray centroid offset from the stellar position by 9'', at a moderate level of significance. The FUV and X-ray discrepancies raise the possibility that the coronal source might be unrelated to the supergiant, perhaps an accidentally close dwarf cluster member; heretofore unrecognized in the optical, lost in the glare of the bright star.

  16. THE THIRD SIGNATURE OF GRANULATION IN BRIGHT-GIANT AND SUPERGIANT STARS

    SciTech Connect

    Gray, David F.; Pugh, Teznie

    2012-04-15

    We investigated third-signature granulation plots for 18 bright giants and supergiants and one giant of spectral classes G0 to M3. These plots reveal the net granulation velocities, averaged over the stellar disk, as a function of depth. Supergiants show significant differences from the 'standard' shape seen for lower-luminosity stars. Most notable is a striking reversal of slope seen for three of the nine supergiants, i.e., stronger lines are more blueshifted than weaker lines, opposite the solar case. Changes in the third-signature plot of {alpha} Sco (M1.5 Iab) with time imply granulation cells that penetrate only the lower portion of the photosphere. For those stars showing the standard shape, we derive scaling factors relative to the Sun that serve as a first-order measure of the strength of the granulation relative to the Sun. For G-type stars, the third-signature scale of the bright giants and supergiants is approximately 1.5 times as strong as in dwarfs, but for K stars, there in no discernible difference between higher-luminosity stars and dwarfs. Classical macroturbulence, a measure of the velocity dispersion of the granulation, increases with the third-signature-plot scale factors, but at different rates for different luminosity classes.

  17. Spectroscopic studies of four southern-hemisphere G-K supergiants: HD 192876 (α1 Cap), HD 194215 (HR 7801), HD 206834 (c Cap), and HD 222574 (104 Aqr)

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V.

    2015-11-01

    We have studied the high-resolution spectra taken with the 1.9-m telescope of the South African Astronomical Observatory for four supergiants that are deemed to be nonvariable and to lie beyond the red edge of the Cepheid instability strip (CIS): HD 192876, HD 194215, HD 206834, and HD 222574. The atmospheric parameters, reddenings, luminosities, distances, radii, and chemical composition have been determined for these stars. Based on these results, we have ascertained thatHD194215 is not a mainsequence star but an ordinary supergiant. All objects exhibit a nearly solar metallicity. The abundances of carbon and oxygen in HD 194215 and HD 206834 are nearly solar, while they are underabundant in HD 192876 and HD 222574. The abundances of sodium, magnesium, and aluminum are different for all objects, while those of the remaining elements are nearly solar. For HD 206834, the measured radial velocity exceeds its previously known values by a factor of 3, while the asymmetric knifelike profiles of the Ha and Hß absorption lines suggest the existence of an extended envelope around the star. Similar profiles of hydrogen absorption lines and strong lines of some metals with low lower-level excitation potentials have also been revealed in the spectrum of HD 222574. The positions of the supergiants on the effective temperature-luminosity diagram in comparison with the evolutionary tracks of the stars have shown their masses to lie within the range 3.4-4.3 M ⊙. HD 194215 and HD 206834 have crossed the CIS for the first time, with the latter object being near the stage of transformation into a red supergiant. HD 192876 and HD 222574 have already passed the first dredge-up and probably move from right to left, crossing the CIS for the second time. The position of HD 222574 near the red CIS edge is probably attributable to its Cepheid-like brightness and radial velocity variations.

  18. Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Martínez-Núñez, Silvia; Kretschmar, Peter; Bozzo, Enrico; Oskinova, Lidia M.; Puls, Joachim; Sidoli, Lara; Sundqvist, Jon Olof; Blay, Pere; Falanga, Maurizio; Fürst, Felix; Gímenez-García, Angel; Kreykenbohm, Ingo; Kühnel, Matthias; Sander, Andreas; Torrejón, José Miguel; Wilms, Jörn

    2017-03-01

    Massive stars, at least ˜10 times more massive than the Sun, have two key properties that make them the main drivers of evolution of star clusters, galaxies, and the Universe as a whole. On the one hand, the outer layers of massive stars are so hot that they produce most of the ionizing ultraviolet radiation of galaxies; in fact, the first massive stars helped to re-ionize the Universe after its Dark Ages. Another important property of massive stars are the strong stellar winds and outflows they produce. This mass loss, and finally the explosion of a massive star as a supernova or a gamma-ray burst, provide a significant input of mechanical and radiative energy into the interstellar space. These two properties together make massive stars one of the most important cosmic engines: they trigger the star formation and enrich the interstellar medium with heavy elements, that ultimately leads to formation of Earth-like rocky planets and the development of complex life. The study of massive star winds is thus a truly multidisciplinary field and has a wide impact on different areas of astronomy. In recent years observational and theoretical evidences have been growing that these winds are not smooth and homogeneous as previously assumed, but rather populated by dense "clumps". The presence of these structures dramatically affects the mass loss rates derived from the study of stellar winds. Clump properties in isolated stars are nowadays inferred mostly through indirect methods (i.e., spectroscopic observations of line profiles in various wavelength regimes, and their analysis based on tailored, inhomogeneous wind models). The limited characterization of the clump physical properties (mass, size) obtained so far have led to large uncertainties in the mass loss rates from massive stars. Such uncertainties limit our understanding of the role of massive star winds in galactic and cosmic evolution. Supergiant high mass X-ray binaries (SgXBs) are among the brightest X

  19. Luminous and Variable Stars in M31 and M33. III. The Yellow and Red Supergiants and Post-red Supergiant Evolution

    NASA Astrophysics Data System (ADS)

    Gordon, Michael S.; Humphreys, Roberta M.; Jones, Terry J.

    2016-07-01

    Recent supernova (SN) and transient surveys have revealed an increasing number of non-terminal stellar eruptions. Though the progenitor class of these eruptions includes the most luminous stars, little is known of the pre-SN mechanics of massive stars in their most evolved state, thus motivating a census of possible progenitors. From surveys of evolved and unstable luminous star populations in nearby galaxies, we select a sample of yellow and red supergiant (RSG) candidates in M31 and M33 for review of their spectral characteristics and spectral energy distributions (SEDs). Since the position of intermediate- and late-type supergiants on the color-magnitude diagram can be heavily contaminated by foreground dwarfs, we employ spectral classification and multi-band photometry from optical and near-infrared surveys to confirm membership. Based on spectroscopic evidence for mass loss and the presence of circumstellar (CS) dust in their SEDs, we find that 30%-40% of the yellow supergiants are likely in a post-RSG state. Comparison with evolutionary tracks shows that these mass-losing, post-RSGs have initial masses between 20 and 40 M ⊙. More than half of the observed RSGs in M31 and M33 are producing dusty CS ejecta. We also identify two new warm hypergiants in M31, J004621.05+421308.06 and J004051.59+403303.00, both of which are likely in a post-RSG state. Based on observations obtained with the Large Binocular Telescope (LBT), an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

  20. Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries

    NASA Astrophysics Data System (ADS)

    Giménez-García, A.; Shenar, T.; Torrejón, J. M.; Oskinova, L.; Martínez-Núñez, S.; Hamann, W.-R.; Rodes-Roca, J. J.; González-Galán, A.; Alonso-Santiago, J.; González-Fernández, C.; Bernabeu, G.; Sander, A.

    2016-06-01

    Context. Classical supergiant X-ray binaries (SGXBs) and supergiant fast X-ray transients (SFXTs) are two types of high-mass X-ray binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors' stellar wind can provide the required information to accomplish an adequate test of these theories. However, such analyses are scarce. Aims: To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J17544-2619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods: We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results: We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 ± 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e< 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the

  1. Discovery of the First B[e] Supergiants in M 31

    NASA Astrophysics Data System (ADS)

    Kraus, M.; Cidale, L. S.; Arias, M. L.; Oksala, M. E.; Borges Fernandes, M.

    2014-01-01

    B[e] supergiants (B[e]SGs) are transitional objects in the post-main sequence evolution of massive stars. The small number of B[e]SGs known so far in the Galaxy and the Magellanic Clouds indicates that this evolutionary phase is short. Nevertheless, the strong aspherical mass loss occurring during this phase, which leads to the formation of rings or disk-like structures, and the similarity to possible progenitors of SN1987 A emphasize the importance of B[e]SGs for the dynamics of the interstellar medium as well as stellar and galactic chemical evolution. The number of objects and their mass-loss behavior at different metallicities are essential ingredients for accurate predictions from stellar and galactic evolution calculations. However, B[e]SGs are not easily identified, as they share many characteristics with luminous blue variables (LBVs) in their quiescent (hot) phase. We present medium-resolution near-infrared K-band spectra for four stars in M 31, which have been assigned a hot LBV (candidate) status. Applying diagnostics that were recently developed to distinguish B[e]SGs from hot LBVs, we classify two of the objects as bonafide LBVs; one of them currently in outburst. In addition, we firmly classify the two stars 2MASS J00441709+4119273 and 2MASS J00452257+4150346 as the first B[e]SGs in M 31 based on strong CO band emission detected in their spectra, and infrared colors typical for this class of stars. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva

  2. RED SUPERGIANTS AS COSMIC ABUNDANCE PROBES: THE SCULPTOR GALAXY NGC 300

    SciTech Connect

    Gazak, J. Zachary; Kudritzki, Rolf; Bresolin, Fabio; Evans, Chris; Patrick, Lee; Davies, Ben; Bergemann, Maria; Plez, Bertrand; Bender, Ralf; Wegner, Michael; Bonanos, Alceste Z.; Williams, Stephen J.

    2015-06-01

    We present a quantitative spectroscopic study of 27 red supergiants (RSGs) in the Sculptor Galaxy NGC 300. J-band spectra were obtained using KMOS on the Very Large Telescope and studied with state of the art synthetic spectra including NLTE corrections for the strongest diagnostic lines. We report a central metallicity of [Z] = −0.03 ± 0.05 with a gradient of −0.083 ± 0.014 [dex/kpc], in agreement with previous studies of blue supergiants and H ii-region auroral line measurements. This result marks the first application of the J-band spectroscopic method to a population of individual RSG stars beyond the Local Group of galaxies and reveals the great potential of this technique.

  3. 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.

  4. A transient supergiant X-ray binary in IC 10: An extragalactic SFXT?

    SciTech Connect

    Laycock, Silas; Cappallo, Rigel; Oram, Kathleen; Balchunas, Andrew

    2014-07-01

    We report the discovery of a large amplitude (factor of ∼100) X-ray transient (IC 10 X-2, CXOU J002020.99+591758.6) in the nearby dwarf starburst galaxy IC 10 during our Chandra monitoring project. Based on the X-ray timing and spectral properties, and an optical counterpart observed with Gemini, the system is a high-mass X-ray binary consisting of a luminous blue supergiant and a neutron star. The highest measured luminosity of the source was 1.8 × 10{sup 37} erg s{sup –1}during an outburst in 2003. Observations before, during, and after a second outburst in 2010 constrain the outburst duration to be less than 3 months (with no lower limit). The X-ray spectrum is a hard power law (Γ = 0.3) with fitted column density (N{sub H} = 6.3 × 10{sup 21} atom cm{sup –2}), consistent with the established absorption to sources in IC 10. The optical spectrum shows hydrogen Balmer lines strongly in emission at the correct blueshift (-340 km s{sup –1}) for IC 10. The N III triplet emission feature is seen, accompanied by He II [4686] weakly in emission. Together these features classify the star as a luminous blue supergiant of the OBN subclass, characterized by enhanced nitrogen abundance. Emission lines of He I are seen, at similar strength to Hβ. A complex of Fe II permitted and forbidden emission lines are seen, as in B[e] stars. The system closely resembles galactic supergiant fast X-ray transients, in terms of its hard spectrum, variability amplitude, and blue supergiant primary.

  5. The Convection of Close Red Supergiant Stars Observed With Near-Infrared Interferometry

    NASA Astrophysics Data System (ADS)

    Montargès, M.; Kervella, P.; Perrin, G.; Chiavassa, A.; Aurière, M.

    2015-12-01

    Our team has obtained observations of the photosphere of the two closest red supergiant stars Betelgeuse (α Ori) and Antares (α Sco) using near infrared interferometry. We have been monitoring the photosphere of Betelgeuse with the VLTI/PIONIER instrument for three years. On Antares, we obtained an unprecedented sampling of the visibility function. These data allow us to probe the convective photosphere of massive evolved stars.

  6. An observational evaluation of magnetic confinement in the winds of BA supergiants

    NASA Astrophysics Data System (ADS)

    Shultz, M.; Wade, G. A.; Petit, V.; Grunhut, J.; Neiner, C.; Hanes, D.; MiMeS Collaboration

    2014-02-01

    Magnetic wind confinement has been proposed as one explanation for the complex wind structures of supergiant stars of spectral types B and A. Observational investigation of this hypothesis was undertaken using high-resolution (λ/Δλ ˜ 65 000) circular polarization (Stokes V) spectra of six late B- and early A-type supergiants (β Ori, B8Iae; 4 Lac, B9Iab; η Leo, A0Ib; HR1040, A0Ib; α Cyg, A2Iae; ν Cep, A2Iab), obtained with the instruments ESPaDOnS and Narval at the Canada-France-Hawaii Telescope and the Bernard Lyot Telescope. Least-squares deconvolution (LSD) analysis of the Stokes V spectra of all stars yields no evidence of a magnetic field, with best longitudinal field 1σ error bars ranging from ˜0.5 to ˜4.5 G for most stars. Spectrum synthesis analysis of the LSD profiles using Bayesian inference yields an upper limit with 95.4 per cent credibility on the polar strength of the (undetected) surface dipole fields of individual stars ranging from 3 to 30 G. These results strongly suggest that magnetic wind confinement due to organized dipolar magnetic fields is not the origin of the wind variability of BA supergiant stars. Upper limits for magnetic spots may also be inconsistent with magnetic wind confinement in the limit of large spot size and filling factor, depending on the adopted wind parameters. Therefore, if magnetic spots are responsible for the wind variability of BA supergiant stars, they likely occupy a small fraction of the photosphere.

  7. Near-infrared spectroscopy of candidate red supergiant stars in clusters

    NASA Astrophysics Data System (ADS)

    Messineo, Maria; Zhu, Qingfeng; Ivanov, Valentin D.; Figer, Donald F.; Davies, Ben; Menten, Karl M.; Kudritzki, Rolf P.; Chen, C.-H. Rosie

    2014-11-01

    Context. Clear identifications of Galactic young stellar clusters farther than a few kpc from the Sun are rare, despite the large number of candidate clusters. Aims: We aim to improve the selection of candidate clusters rich in massive stars with a multiwavelength analysis of photometric Galactic data that range from optical to mid-infrared wavelengths. Methods: We present a photometric and spectroscopic analysis of five candidate stellar clusters, which were selected as overdensities with bright stars (Ks< 7 mag) in GLIMPSE and 2MASS images. Results: A total of 48 infrared spectra were obtained. The combination of photometry and spectroscopy yielded six new red supergiant stars with masses from 10 M⊙ to 15 M⊙. Two red supergiants are located at Galactic coordinates (l,b) = (16.°7, -0.°63) and at a distance of about ~3.9 kpc; four other red supergiants are members of a cluster at Galactic coordinates (l,b) = (49.°3, + 0.°72) and at a distance of ~7.0 kpc. Conclusions: Spectroscopic analysis of the brightest stars of detected overdensities and studies of interstellar extinction along their line of sights are fundamental to distinguish regions of low extinction from actual stellar clusters. The census of young star clusters containing red supergiants is incomplete; in the existing all-sky near-infrared surveys, they can be identified as overdensities of bright stars with infrared color-magnitude diagrams characterized by gaps. Based on observations collected at the European Southern Observatory (ESO Programme 60.A-9700(E), and 089.D-0876), and on observations collected at the UKIRT telescope (programme ID H243NS).MM is currently employed by the MPIfR. Part of this work was performed at RIT (2009), at ESA (2010), and at the MPIfR.Tables 3, 4, and 6 are available in electronic form at http://www.aanda.org

  8. Abundances of r-PROCESS Elements in the Photosphere of Red Supergiant Star PMMR23 in Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Vasil'Eva, S. V.; Gopka, V. F.; Yushchenko, A. V.; Andryevsky, S. M.

    Detailed analysis of chemical abundances determined from high-resolution CCD-spectrogram of supergiant star PMMR23 (K5 I) in SMC is presented. The observation were obtained at 3.6 meter ESO La Silla telescope by Hill (1997). Spectral resolving power is near R=30.000. The wavelength coverage is 5050-7200 A. The abundances of iron and 15 r-, s-processes elements are found. The abundances of Cu, Zr, Mo, Ru, Pr, Sm, Gd, Dy, Er are found for the first time. The abundances of elements with atomic numbers less than 55 are deficient with respect to the Sun. The mean underabundance is near 0.7 dex. The abundances of barium and lanthanides are near solar values. The overabundances of these elements with respect to iron are in the range from 0.4 tp 0.9 dex. The abundances of heavy lanthanides are higher than the abundances of light lanthanides. The abundance pattern of PMMR23 can be fitted by scaled solar r-process distribution. The atmosphere of PMMR23 is enriched by r-process elements.

  9. SUPERGIANT SHELLS AND MOLECULAR CLOUD FORMATION IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Dawson, J. R.; Dickey, John M.; McClure-Griffiths, N. M.; Wong, T.; Hughes, A.; Fukui, Y.; Kawamura, A.

    2013-01-20

    We investigate the influence of large-scale stellar feedback on the formation of molecular clouds in the Large Magellanic Cloud (LMC). Examining the relationship between H I and {sup 12}CO(J = 1-0) in supergiant shells (SGSs), we find that the molecular fraction in the total volume occupied by SGSs is not enhanced with respect to the rest of the LMC disk. However, the majority of objects ({approx}70% by mass) are more molecular than their local surroundings, implying that the presence of a supergiant shell does on average have a positive effect on the molecular gas fraction. Averaged over the full SGS sample, our results suggest that {approx}12%-25% of the molecular mass in supergiant shell systems was formed as a direct result of the stellar feedback that created the shells. This corresponds to {approx}4%-11% of the total molecular mass of the galaxy. These figures are an approximate lower limit to the total contribution of stellar feedback to molecular cloud formation in the LMC, and constitute one of the first quantitative measurements of feedback-triggered molecular cloud formation in a galactic system.

  10. Do All Stars Form in Clusters?: Masses and Ages of Young Supergiants in Andromeda

    NASA Astrophysics Data System (ADS)

    Choudhury, Zareen; Debs, C.; Kirby, E. N.; Guhathakurta, P.

    2013-01-01

    Currently it is not understood whether seemingly isolated stars formed in situ or were ejected from star clusters as runaway stars. Previous studies determined the origins of isolated stars by measuring their velocities, but past research was limited to OB stars in the Milky Way and Magellanic Clouds due to the difficulty of computing velocities of distant objects. This study proposed an innovative velocity test to statistically determine whether six seemingly isolated BA-type supergiants in Andromeda are runaways. We calculated the minimum relative transverse velocity needed for each supergiant to travel to its current location from the nearest open cluster. By comparing the minimum velocity with Andromeda’s known velocity dispersion, a statistical measure of the stars’ actual velocities, we determined whether the star had the necessary velocity to be a runaway. Minimum velocity was computed from the age of the star, which was calculated from its effective temperature and surface gravity. To compute effective temperature and surface gravity, we applied three new techniques based on Balmer absorption features. The results suggest that all six supergiants had the necessary velocities to be runaways. Although the proposed velocity test is a statistical assessment, it offers a valuable new tool for future investigation of isolated stars beyond the Milky Way and its satellites. This research was supported by the Science Internship Program (SIP) at UCSC, the National Science Foundation, NASA, and Palomar Observatory.

  11. Analytical solutions of stellar winds in B-A type supergiants stars

    NASA Astrophysics Data System (ADS)

    Araya, Ignacio; Cure, Michel

    2013-06-01

    An analytical solution for the δ-slow hydrodynamic solution (Cure et al. 2011) in B-A type supergiants stars is developed. The methodology is based on the analytical solutions of a) Villata (1992), which is described in terms of the stellar and wind parameters and b) Muller & Vink (2008), which is described in terms of fitting parameters from a numerical solution (hydrodynamic). These methodologies only apply for fast solutions, for that reason the line acceleration term (gL) of Muller & Vink method is modified in order to obtain an analytical solution for the δ-slow solution. To find a relationship between the parameters from the fit and the stellar and wind parameters, a computational grid, based on the grid of stellar models from Ekstrom et al. (2012), is created for B-A type supergiants stars with δ-slow hydrodynamic solution. Finally, an analytical solution for B-A type supergiants stars is obtained based on the Lambert W function (Corless et al. 1996). Comparing with the numerical solutions, the terminal velocity has a median relative error below 4% and the mass loss rate has a median relative error below 5%. In addition, we calculated the wind-momentum luminosity relationship (WLR) with the models from the computational grid and compared with the observations, showing a very good agreement.

  12. Interacting supernovae from photoionization-confined shells around red supergiant stars.

    PubMed

    Mackey, Jonathan; Mohamed, Shazrene; Gvaramadze, Vasilii V; Kotak, Rubina; Langer, Norbert; Meyer, Dominique M-A; Moriya, Takashi J; Neilson, Hilding R

    2014-08-21

    Betelgeuse, a nearby red supergiant, is a fast-moving star with a powerful stellar wind that drives a bow shock into its surroundings. This picture has been challenged by the discovery of a dense and almost static shell that is three times closer to the star than the bow shock and has been decelerated by some external force. The two physically distinct structures cannot both be formed by the hydrodynamic interaction of the wind with the interstellar medium. Here we report that a model in which Betelgeuse's wind is photoionized by radiation from external sources can explain the static shell without requiring a new understanding of the bow shock. Pressure from the photoionized wind generates a standing shock in the neutral part of the wind and forms an almost static, photoionization-confined shell. Other red supergiants should have much more massive shells than Betelgeuse, because the photoionization-confined shell traps up to 35 per cent of all mass lost during the red supergiant phase, confining this gas close to the star until it explodes. After the supernova explosion, massive shells dramatically affect the supernova light curve, providing a natural explanation for the many supernovae that have signatures of circumstellar interaction.

  13. Toward Connecting Core-Collapse Supernova Theory with Observations: Nucleosynthetic Yields and Distribution of Elements in a 15 M⊙ Blue Supergiant Progenitor with SN 1987A Energetics

    NASA Astrophysics Data System (ADS)

    Plewa, Tomasz; Handy, Timothy; Odrzywolek, Andrzej

    2014-03-01

    We compute and discuss the process of nucleosynthesis in a series of core-collapse explosion models of a 15 solar mass, blue supergiant progenitor. We obtain nucleosynthetic yields and study the evolution of the chemical element distribution from the moment of core bounce until young supernova remnant phase. Our models show how the process of energy deposition due to radioactive decay modifies the dynamics and the core ejecta structure on small and intermediate scales. The results are compared against observations of young supernova remnants including Cas A and the recent data obtained for SN 1987A. The work has been supported by the NSF grant AST-1109113 and DOE grant DE-FG52-09NA29548. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the U.S. DoE under Contract No. DE-AC02-05CH11231.

  14. SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Deguchi, Shuji; Nakashima, Jun-Ichi; Zhang, Yong; Chong, Selina S. N.; Koike, Kazutaka; Kwok, Sun

    2010-04-01

    We present the results of radio observations of red supergiants in a star cluster, Stephenson (1990, AJ, 99, 1867)'s #2, and of candidates for red supergiants in three star clusters, Mercer et al. (2005, ApJ, 635, 560)'s #4, #8, and #13, in the SiO and H2O maser lines. The Stephenson's #2 cluster and nearby aggregation at the southwest contain more than 15 red supergiants. We detected one red supergiant at the center of Stephenson's #2 and three in a southwest aggregation in the SiO maser line; three out of these four were also detected in the H2O maser line. The average radial velocity of the four detected objects is 97 km s-1, giving a kinematic distance of 5.5 kpc, which locates this cluster near the base of the Scutum-Crux spiral arm. We also detected six SiO emitting objects associated with other star clusters. In addition, mapping observations in the CO J = 1-0 line toward these clusters revealed that an appreciable amount of molecular gas still remains around the Stephenson's #2 cluster in contrast to the prototypical red-supergiant cluster, Bica et al. (2003, A&A, 404, 223)'s #122. This indicates that the time scale of gas expulsion differs considerably in individual clusters.

  15. Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters

    NASA Astrophysics Data System (ADS)

    Firnstein, M.; Przybilla, N.

    2012-07-01

    Context. BA-type supergiants show a high potential as versatile indicators for modern astronomy. This paper constitutes the first in a series that aims at a systematic spectroscopic study of Galactic BA-type supergiants. Various problems will be addressed, including in particular observational constraints on the evolution of massive stars and a determination of abundance gradients in the Milky Way. Aims: The focus here is on the determination of accurate and precise atmospheric parameters for a sample of Galactic BA-type supergiants as prerequisite for all further analysis. Some first applications include a recalibration of functional relationships between spectral-type, intrinsic colours, bolometric corrections and effective temperature, and an exploration of the reddening-free Johnson Q and Strömgren [c1] and β-indices as photometric indicators for effective temperatures and gravities of BA-type supergiants. Methods: An extensive grid of theoretical spectra is computed based on a hybrid non-LTE approach, covering the relevant parameter space in effective temperature, surface gravity, helium abundance, microturbulence and elemental abundances. The atmospheric parameters are derived spectroscopically by line-profile fits of our theoretical models to high-resolution and high-S/N spectra obtained at various observatories. Ionization equilibria of multiple metals and the Stark-broadened hydrogen and the neutral helium lines constitute our primary indicators for the parameter determination, supplemented by (spectro-)photometry from the UV to the near-IR. Results: We obtain accurate atmospheric parameters for 35 sample supergiants from a homogeneous analysis. Data on effective temperatures, surface gravities, helium abundances, microturbulence, macroturbulence and rotational velocities are presented. The interstellar reddening and the ratio of total-to-selective extinction towards the stars are determined. Our empirical spectral-type-Teff scale is steeper than

  16. THE DISCOVERY OF A MASSIVE CLUSTER OF RED SUPERGIANTS WITH GLIMPSE

    SciTech Connect

    Alexander, Michael J.; Kobulnicky, Henry A.; Clemens, Dan P.; Jameson, Katherine; Pinnick, April; Pavel, Michael

    2009-06-15

    We report the discovery of a previously unknown massive Galactic star cluster at l = 29.{sup 0}22, b = -0.{sup 0}20. Identified visually in mid-IR images from the Spitzer GLIMPSE survey, the cluster contains at least eight late-type supergiants, based on follow-up near-IR spectroscopy, and an additional 3-6 candidate supergiant members having IR photometry consistent with a similar distance and reddening. The cluster lies at a local minimum in the {sup 13}CO column density and 8 {mu}m emission. We interpret this feature as a hole carved by the energetic winds of the evolving massive stars. The {sup 13}CO hole seen in molecular maps at V {sub LSR} {approx} 95 km s{sup -1} corresponds to near/far kinematic distances of 6.1/8.7 {+-} 1 kpc. We calculate a mean spectrophotometric distance of 7.0{sup +3.7} {sub -2.4} kpc, broadly consistent with the kinematic distances inferred. This location places it near the northern end of the Galactic bar. For the mean extinction of A{sub V} = 12.6 {+-} 0.5 mag (A{sub K} = 1.5 {+-} 0.1 mag), the color-magnitude diagram of probable cluster members is well fit by isochrones in the age range 18-24 Myr. The estimated cluster mass is {approx}20,000 M {sub sun}. With the most massive original cluster stars likely deceased, no strong radio emission is detected in this vicinity. As such, this red supergiant (RSG) cluster is representative of adolescent massive Galactic clusters that lie hidden behind many magnitudes of dust obscuration. This cluster joins two similar RSG clusters as residents of the volatile region where the end of our Galaxy's bar joins the base of the Scutum-Crux spiral arm, suggesting a recent episode of widespread massive star formation there.

  17. The Discovery of a Massive Cluster of Red Supergiants with GLIMPSE

    NASA Astrophysics Data System (ADS)

    Alexander, Michael J.; Kobulnicky, Henry A.; Clemens, Dan P.; Jameson, Katherine; Pinnick, April; Pavel, Michael

    2009-06-01

    We report the discovery of a previously unknown massive Galactic star cluster at ell = 29fdg22, b = -0fdg20. Identified visually in mid-IR images from the Spitzer GLIMPSE survey, the cluster contains at least eight late-type supergiants, based on follow-up near-IR spectroscopy, and an additional 3-6 candidate supergiant members having IR photometry consistent with a similar distance and reddening. The cluster lies at a local minimum in the 13CO column density and 8 μm emission. We interpret this feature as a hole carved by the energetic winds of the evolving massive stars. The 13CO hole seen in molecular maps at V LSR ~ 95 km s-1 corresponds to near/far kinematic distances of 6.1/8.7 ± 1 kpc. We calculate a mean spectrophotometric distance of 7.0+3.7 -2.4 kpc, broadly consistent with the kinematic distances inferred. This location places it near the northern end of the Galactic bar. For the mean extinction of AV = 12.6 ± 0.5 mag (AK = 1.5 ± 0.1 mag), the color-magnitude diagram of probable cluster members is well fit by isochrones in the age range 18-24 Myr. The estimated cluster mass is ~20,000 M sun. With the most massive original cluster stars likely deceased, no strong radio emission is detected in this vicinity. As such, this red supergiant (RSG) cluster is representative of adolescent massive Galactic clusters that lie hidden behind many magnitudes of dust obscuration. This cluster joins two similar RSG clusters as residents of the volatile region where the end of our Galaxy's bar joins the base of the Scutum-Crux spiral arm, suggesting a recent episode of widespread massive star formation there.

  18. The Mass and Age Dependence of Dusty Red Supergiant Winds, and Their Impact on Supernova Progenitors

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    The dusty winds of red supergiants (RSGs) have a tremendous impact on the evolution of stars of 8-40 M_sun. Wind strength determines whether a star can shed its H envelope or not, thus determining the type of resulting SN, and these dusty winds create the circumstellar medium (CSM) at the end of the stars life. However, RSG mass-loss rates are very uncertain, which hampers the predictive power of stellar evolution models. RSGs are expected to end their lives as Type II-P supernovae. Many RSGs are observed with initial masses well above 20 M_sun, but from Type II-P progenitors directly detected so far it seems that the stars that explode are of relatively low mass, with all progenitor mass estimates below 16-17 M_sun. This is known as the Red Supergiant Problem, prompting suggestions that the massive RSGs collapse to black holes with undetectably faint SNe. Alternatively, it has also been suggested that the more massive RSGs evolve to yield other types of SNe or that dusty CSM could cause the progenitor to faint, underestimating its mass. One expects that the most massive and most evolved RSGs would also have the highest extinction or would be the most likely to evolve to a H-free star -- this is qualitatively what is needed to explain the missing high-mass RSGs. To test this idea, we propose to use FORCAST to obtain mid-IR photometry for RSGs in three coeval star clusters with known ages(and different turnoff masses of 12, 18, and 35 M_sun). By modeling CSM dust emission, we will derive mass and age dependent mass-loss rates and CSM extinction, below and above the derived cutoff mass for Type II-P progenitors, thereby determining whether this effect is large enough to solve the Red Supergiant Problem.

  19. Clumpy Molecular Structures Revolving the B[e] Supergiant MWC 137

    NASA Astrophysics Data System (ADS)

    Kraus, M.; Cidale, L. S.; Liimets, T.; Cappa, C. E.; Duronea, N.; Gunawan, D. S.; Oksala, M. E.; Santander-García, M.; Arias, M. L.; Nickeler, D. H.; Maravelias, G.; Borges Fernandes, M.; Curé, M.

    2017-02-01

    The peculiar emission-line star MWC 137 with its extended optical nebula was recently classified as a B[e] supergiant. To study the spatial distribution of its circumstellar molecular gas on small and large scales, we obtained near-infrared and radio observations using SINFONI and APEX, respectively. We find that the hot CO gas is arranged in a moving clumpy ring and shell structures close to the star, while a cold CO envelope is encircling the borders of the optical nebula from South to West.

  20. Light variations of the population II F-type supergiant HD 46703

    NASA Technical Reports Server (NTRS)

    Bond, H. E.; Carney, B. W.; Grauer, A. D.

    1984-01-01

    Photometric monitoring has revealed brightness variations of 0.1 m on a time scale of weeks for HD 46703, a metal-deficient F-type field analog of the stars lying above the horizontal branch in globular clusters. It is suggested that HD 46703 belongs to the '89 Her' class of luminous F-type variables. Since HD 46703 is unquestionably a halo object, it is almost certainly a low-mass star. It is suggested that it, and probably the other 89 Her variables, are masquerading as supergiants during their final evolution off the asymptotic giant branch.

  1. Radiative hydrodynamic simulations of red supergiant stars. III. Spectro-photocentric variability, photometric variability, and consequences on Gaia measurements

    NASA Astrophysics Data System (ADS)

    Chiavassa, A.; Pasquato, E.; Jorissen, A.; Sacuto, S.; Babusiaux, C.; Freytag, B.; Ludwig, H.-G.; Cruzalèbes, P.; Rabbia, Y.; Spang, A.; Chesneau, O.

    2011-04-01

    Context. It has been shown that convection in red supergiant stars (RSG) gives rise to large granules that cause surface inhomogeneities and shock waves in the photosphere. The resulting motion of the photocentre (on time scales ranging from months to years) could possibly have adverse effects on the parallax determination with Gaia. Aims: We explore the impact of the granulation on the photocentric and photometric variability. We quantify these effects in order to better characterise the error that could possibly alter the parallax. Methods: We use 3D radiative-hydrodynamics (RHD) simulations of convection with CO5BOLD and the post-processing radiative transfer code Optim3D to compute intensity maps and spectra in the Gaia G band [325-1030 nm]. Results: We provide astrometric and photometric predictions from 3D simulations of RSGs that are used to evaluate the possible degradation of the astrometric parameters of evolved stars derived by Gaia. We show in particular from RHD simulations that a supergiant like Betelgeuse exhibits a photocentric noise characterised by a standard deviation of the order of 0.1 AU. The number of bright giant and supergiant stars whose Gaia parallaxes will be altered by the photocentric noise ranges from a few tens to several thousands, depending on the poorly known relation between the size of the convective cells and the atmospheric pressure scale height of supergiants, and to a lower extent, on the adopted prescription for galactic extinction. In the worst situation, the degradation of the astrometric fit caused by this photocentric noise will be noticeable up to about 5 kpc for the brightest supergiants. Moreover, parallaxes of Betelgeuse-like supergiants are affected by an error of the order of a few percents. We also show that the photocentric noise, as predicted by the 3D simulation, does account for a substantial part of the supplementary "cosmic noise" that affects Hipparcos measurements of Betelgeuse and Antares.

  2. A windswept cometary tail on the Galactic center supergiant IRS 7

    NASA Technical Reports Server (NTRS)

    Yusef-Zadeh, F.; Morris, Mark

    1991-01-01

    High-resolution VLA observations provide evidence of optically thick radio emission from IRS 7, a cool red supergiant star, located at a projected distance of roughly 1 1t-yr from the Galactic center. IRS 7 shows a remarkable tail of ionized gas pointing directly away from the compact nonthermal radio source at the Galactic center, Sgr A(asterisk). Given previous evidence for a strong source of UV emission and for a strong circumnuclear wind emanating from the Galactic center, the free-free emission from IRS 7 and its associated tail are interpreted in terms of the ionization and removal of the circumstellar envelope of the red supergiant either by the ram pressure of the nuclear wind or by the pressure of radiation arising from the immediate vicinity of Sgr A(asterisk). The wind mechanism is preferred because: (1) the force it can potentially exert is much greater; and (2) Sgr A(asterisk) is clearly not a known source of luminous energy in the near-IR, whereas it remains a plausible source of a hot, high-velocity wind. Also considered is the potential effect of a nuclear wind upon the atmospheres of red giants in the inner parsec.

  3. SPECTROSCOPIC AND PHOTOMETRIC VARIABILITY IN THE A0 SUPERGIANT HR 1040

    SciTech Connect

    Corliss, David J.; Morrison, Nancy D.; Adelman, Saul J.

    2015-12-15

    A time-series analysis of spectroscopic and photometric observables of the A0 Ia supergiant HR 1040 has been performed, including equivalent widths, radial velocities, and Strömgren photometric indices. The data, obtained from 1993 through 2007, include 152 spectroscopic observations from the Ritter Observatory 1 m telescope and 269 Strömgren photometric observations from the Four College Automated Photoelectric Telescope. Typical of late B- and early A-type supergiants, HR 1040 has a highly variable Hα profile. The star was found to have an intermittent active phase marked by correlation between the Hα absorption equivalent width and blue-edge radial velocity and by photospheric connections observed in correlations to equivalent width, second moment and radial velocity in Si ii λλ6347, 6371. High-velocity absorption (HVA) events were observed only during this active phase. HVA events in the wind were preceded by photospheric activity, including Si ii radial velocity oscillations 19–42 days prior to onset of an HVA event and correlated increases in Si ii W{sub λ} and second moment from 13 to 23 days before the start of the HVA event. While increases in various line equivalent widths in the wind prior to HVA events have been reported in the past in other stars, our finding of precursors in enhanced radial velocity variations in the wind and at the photosphere is a new result.

  4. SOFIA-EXES: Probing the Thermal Structure of M Supergiant Wind Acceleration Zones

    NASA Astrophysics Data System (ADS)

    Harper, Graham M.; O'Gorman, Eamon; Guinan, Edward F.; EXES Instrument Team, EXES Science Team

    2016-01-01

    There is no standard model for mass loss from cool evolved stars, particularly for non-pulsating giants and supergiants. For the early-M supergiants, radiation pressure, convective ejections, magnetic fields, and Alfven waves have all been put forward as potential mass loss mechanisms. A potential discriminator between these ideas is the thermal structure resulting from the heating-cooling balance in the acceleration zone - the most important region to study mass loss physics.We present mid-IR [Fe II] emission line profiles of Betelgeuse and Antares obtained with NASA-DLR SOFIA-EXES and NASA IRTF-TEXES that were obtained as part of a GO program (Harper: Cycle 2-0004) and EXES instrument commissioning observations. The intra-term transitions sample a range of excitation conditions, Texc=540K, 3,400K, and 11,700K, i.e., from the warm chromospheric plasma, that also emits in the cm-radio and ultraviolet, to the cold inner circumstellar envelope. The spectrally-resolved profiles, when combined with VLA cm-radio observations, provide new constraints on the temperature and flow velocity in the outflow accelerating region. The semi-empirical energy balance can be used to test theoretical predictions of wind heating.

  5. ALMA observations of the supergiant B[e] star Wd1-9

    NASA Astrophysics Data System (ADS)

    Fenech, D. M.; Clark, J. S.; Prinja, R. K.; Morford, J. C.; Dougherty, S.; Blomme, R.

    2017-01-01

    Mass-loss in massive stars plays a critical role in their evolution, although the precise mechanism(s) responsible - radiatively driven winds, impulsive ejection and/or binary interaction - remain uncertain. In this Letter, we present Atacama Large Millimetre/Submillimeter Array line and continuum observations of the supergiant B[e] star Wd1-9, a massive post-main-sequence object located within the starburst cluster Westerlund 1 (Wd1). We find it to be one of the brightest stellar point sources in the sky at millimetre wavelengths, with (serendipitously identified) emission in the H41α radio recombination line. We attribute these properties to a low velocity (˜100 km s-1 ) ionized wind, with an extreme mass-loss rate ≳6.4 × 10-5(d/5 kpc)1.5 M⊙yr- 1. External to this is an extended aspherical ejection nebula indicative of a prior phase of significant mass-loss. Taken together, the millimetre properties of Wd1-9 show a remarkable similarity to those of the highly luminous stellar source MWC349A. We conclude that these objects are interacting binaries evolving away from the main sequence and undergoing rapid case-A mass transfer. As such they - and by extension the wider class of supergiant B[e] stars - may provide a unique window into the physics of a process that shapes the life-cycle of ˜70 per cent of massive stars found in binary systems.

  6. The VLT-FLAMES Tarantula Survey. XXV. Surface nitrogen abundances of O-type giants and supergiants

    NASA Astrophysics Data System (ADS)

    Grin, N. J.; Ramírez-Agudelo, O. H.; de Koter, A.; Sana, H.; Puls, J.; Brott, I.; Crowther, P. A.; Dufton, P. L.; Evans, C. J.; Gräfener, G.; Herrero, A.; Langer, N.; Lennon, D. J.; van Loon, J. Th.; Markova, N.; de Mink, S. E.; Najarro, F.; Schneider, F. R. N.; Taylor, W. D.; Tramper, F.; Vink, J. S.; Walborn, N. R.

    2017-04-01

    Context. Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Aims: Using a sample of 72 presumably single O-type giants to supergiants observed in the context of the VLT-FLAMES Tarantula Survey (VFTS), we aim to investigate rotational mixing in evolved core-hydrogen burning stars initially more massive than 15 M⊙ by analysing their surface nitrogen abundances. Methods: Using stellar and wind properties derived in a previous VFTS study we computed synthetic spectra for a set of up to 21 N ii-v lines in the optical spectral range, using the non-LTE atmosphere code FASTWIND. We constrained the nitrogen abundance by fitting the equivalent widths of relatively strong lines that are sensitive to changes in the abundance of this element. Given the quality of the data, we constrained the nitrogen abundance in 38 cases; for 34 stars only upper limits could be derived, which includes almost all stars rotating at νesini> 200 km s-1. Results: We analysed the nitrogen abundance as a function of projected rotation rate νesini and confronted it with predictions of rotational mixing. We found a group of N-enhanced slowly-spinning stars that is not in accordance with predictions of rotational mixing in single stars. Among O-type stars with (rotation-corrected) gravities less than log gc = 3.75 this group constitutes 30-40 percent of the population. We found a correlation between nitrogen and helium abundance which is consistent with expectations, suggesting that, whatever the mechanism that brings N to the surface, it displays CNO-processed material. For the rapidly-spinning O-type stars we can only provide upper limits on the nitrogen abundance, which are not in violation with theoretical expectations. Hence, the data cannot be used to test the physics of rotation induced mixing in the regime of high spin rates

  7. IUE observations of the Henize-Carlson sample of peculiar emission line supergiants: The galactic analogs of the Magellanic Zoo

    NASA Technical Reports Server (NTRS)

    Shore, Steven N.; Brown, Douglas N.; Sanduleak, N.

    1986-01-01

    Some 15 stars from the Carlson-Henize survey of southern peculiar emission line stars were studied. From both the optical and UV spectra, they appear to be galactic counterparts of the most extreme early-type emission line supergiants of the Magellanic Clouds.

  8. A hot companion to Mu Sagittarii - An opportunity to sound the atmosphere of a B8 Ia supergiant

    NASA Technical Reports Server (NTRS)

    Polidan, R. S.; Plavec, M. J.

    1984-01-01

    It is argued that the bright supergiant star Mu Sagittarii is accompanied by a smaller and hotter star, of spectral type approximately B1.5 V. The single-line radial-velocity curve of the B8 star leads to a fairly large mass function, f(m) = 2.64 solar masses, implying that the companion should have at least 50 percent of the mass of the visible star. Older optical observations indicated the presence of a shallow eclipse at the time of the conjunction with the supergiant behind the companion. Since the Copernicus, IUE, and Voyager observations show that the companion is the hotter component, that eclipse must have been the secondary eclipse (if it was an eclipse at all). A deeper, primary eclipse has been predicted by Plavec in 1978. It was indeed observed as a marked decrease of the far-ultraviolet flux from the system both with the Copernicus and the IUE satellites. The presence of a hotter but smaller component in Mu Sagittarii offers a unique opportunity to study the outer atmospheric layers of a supergiant which is of a much earlier spectral type than the supergiants in the Zeta Aurigae systems.

  9. The mass-loss rates of red supergiants at low metallicity: detection of rotational CO emission from two red supergiants in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Matsuura, Mikako; Sargent, B.; Swinyard, Bruce; Yates, Jeremy; Royer, P.; Barlow, M. J.; Boyer, Martha; Decin, L.; Khouri, Theo; Meixner, Margaret; van Loon, Jacco Th.; Woods, Paul M.

    2016-11-01

    Using the PACS and SPIRE spectrometers on-board the Herschel Space Observatory, we obtained spectra of two red supergiants (RSGs) in the Large Magellanic Cloud (LMC). Multiple rotational CO emission lines (J = 6-5 to 15-14) and 15 H2O lines were detected from IRAS 05280-6910, and one CO line was detected from WOH G64. This is the first time that CO rotational lines have been detected from evolved stars in the LMC. Their CO line intensities are as strong as those of the Galactic RSG, VY CMa. Modelling the CO lines and the spectral energy distribution results in an estimated mass-loss rate for IRAS 05280-6910 of 3 × 10-4 M⊙ yr-1. The model assumes a gas-to-dust ratio and a CO-to-H2 abundance ratio is estimated from the Galactic values scaled by the LMC metallicity ([Fe/H] ˜ -0.3), i.e. that the CO-to-dust ratio is constant for Galactic and LMC metallicities within the uncertainties of the model. The key factor determining the CO line intensities and the mass-loss rate found to be the stellar luminosity.

  10. The early-type strong emission-line supergiants of the Magellanic Clouds - A spectroscopic zoology

    NASA Technical Reports Server (NTRS)

    Shore, S. N.; Sanduleak, N.

    1984-01-01

    The results of a spectroscopic survey of 21 early-type extreme emission line supergiants of the Large and Small Magellanic Clouds using IUE and optical spectra are presented. The combined observations are discussed and the literature on each star in the sample is summarized. The classification procedures and the methods by which effective temperatures, bolometric magnitudes, and reddenings were assigned are discussed. The derived reddening values are given along with some results concerning anomalous reddening among the sample stars. The derived mass, luminosity, and radius for each star are presented, and the ultraviolet emission lines are described. Mass-loss rates are derived and discussed, and the implications of these observations for the evolution of the most massive stars in the Local Group are addressed.

  11. The Swift Supergiant Fast X-Ray Transients Project:. [A Review, New Results and Future Perspectives

    NASA Technical Reports Server (NTRS)

    Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Vercellone, S.; Bocchino, F.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.; Farinelli, R.; Ceccobello, C.

    2013-01-01

    We present a review of the Supergiant Fast X-ray Transients (SFXT) Project, a systematic investigation of the properties of SFXTs with a strategy that combines Swift monitoring programs with outburst follow-up observations. This strategy has quickly tripled the available sets of broad-band data of SFXT outbursts, and gathered a wealth of out-of-outburst data, which have led us to a broad-band spectral characterization, an assessment of the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present some new observational results obtained through our outburst follow-ups, as fitting examples of the exceptional capabilities of Swift in catching bright flares and monitor them panchromatically.

  12. Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources

    NASA Technical Reports Server (NTRS)

    Cohen, R. J.; Downs, G.; Emerson, R.; Grimm, M.; Gulkis, S.; Stevens, G.

    1987-01-01

    High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.

  13. Physical conditions near red giant and supergiant stars - An interpretation of SiO VLBI maps

    NASA Technical Reports Server (NTRS)

    Alcock, Charles; Ross, Randy R.

    1986-01-01

    Understanding the dynamical structure of circumstellar envelopes around cool giant and supergiant stars depends critically on the knowledge of what happens in the 'near zone' of the envelope, within a few stellar radii of the star. One probe with adequate angular resolution to study the near zone is VLBI observation of the SiO masers. It is shown that VLBI maps of VX Sgr establish that the particle density in the SiO masers is very high (about 10 to the 12th/cu cm), indicating that the masers form in dense cloudlets and not in a spherically expanding wind. The implications of these results for the mechanism of mass loss are discussed.

  14. Properties of Supergiant Fast X-Ray Transients as Observed by Swift

    NASA Technical Reports Server (NTRS)

    Romano, P.; Vercellone, S.; Krimm, H. A.; Esposito, P.; Cusumano, C.; LaParola, V.; Mangano, V.; Kennea, J. A.; Burrows, D. N.; Pagani, C.; Gehrels, N.

    2011-01-01

    We present the most recent results from our investigation on Supergiant Fast X-ray Transients, a class of High-Mass X-ray Binaries, with a possible counterpart in the gamma-ray energy band. Since 2007 Swift has contributed to this new field by detecting outbursts from these fast transients with the BAT and by following them for days with the XRT. Thus, we demonstrated that while the brightest phase of the outburst only lasts a few hours, further activity is observed at lower fluxes for a remarkably longer time, up to weeks. Furthermore, we have performed several campaigns of intense monitoring with the XRT, assessing the fraction of the time these sources spend in each phase, and their duty cycle of inactivity.

  15. Impact of mass-loss on the evolution and pre-supernova properties of red supergiants

    NASA Astrophysics Data System (ADS)

    Meynet, G.; Chomienne, V.; Ekström, S.; Georgy, C.; Granada, A.; Groh, J.; Maeder, A.; Eggenberger, P.; Levesque, E.; Massey, P.

    2015-03-01

    Context. The post-main-sequence evolution of massive stars is very sensitive to many parameters of the stellar models. Key parameters are the mixing processes, the metallicity, the mass-loss rate, and the effect of a close companion. Aims: We study the change in the red supergiant (RSG) lifetimes, the tracks in the Hertzsprung-Russel diagram (HRD), the positions in this diagram of the pre-supernova progenitor and the structure of the stars at that time for various mass-loss rates during the RSG phase and for two different initial rotation velocities. Methods: Stellar models were computed with the Geneva code for initial masses between 9 and 25 M⊙ at solar metallicity (Z = 0.014) with 10 times and 25 times the standard mass-loss rates during the RSG phase, with and without rotation. Results: The surface abundances of RSGs are much more sensitive to rotation than to the mass-loss rates during that phase. A change of the RSG mass-loss rate has a strong impact on the RSG lifetimes and in turn on the luminosity function of RSGs. An observed RSG is associated with a model of higher initial mass when models with an enhanced RSG mass-loss rate are used to deduce that mass. At solar metallicity, models with an enhanced mass-loss rate produce significant changes in the populations of blue, yellow, and RSGs. When extended blue loops or blueward excursions are produced by enhanced mass-loss, the models predict that a majority of blue (yellow) supergiants are post-RSG objects. These post-RSG stars are predicted to show much lower surface rotational velocities than similar blue supergiants on their first crossing of the HR gap. Enhanced mass-loss rates during the RSG phase have little impact on the Wolf-Rayet populations. The position in the HRD of the end point of the evolution depends on the mass of the hydrogen envelope. More precisely, whenever at the pre-supernova stage the H-rich envelope contains more than about 5% of the initial mass, the star is a RSG, and whenever

  16. OBSERVATIONAL EVIDENCE FOR A CORRELATION BETWEEN MACROTURBULENT BROADENING AND LINE-PROFILE VARIATIONS IN OB SUPERGIANTS

    SciTech Connect

    Simon-Diaz, S.; Herrero, A.; Castro, N.; Uytterhoeven, K.; Puls, J.

    2010-09-10

    The spectra of O and B supergiants (Sgs) are known to be affected by a significant form of extra line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high-resolution spectra have shown that the interpretation of this line broadening as a consequence of large-scale turbulent motions would imply highly supersonic velocity fields in photospheric regions, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. As part of a long-term observational project, we are investigating the macroturbulent broadening in O and B Sgs and its possible connection with spectroscopic variability phenomena and stellar oscillations. In this Letter, we present the first encouraging results of our project, namely, firm observational evidence for a strong correlation between the extra broadening and photospheric line-profile variations in a sample of 13 Sgs with spectral types ranging from O9.5 to B8.

  17. Dense Molecular Clumps Associated with the LMC Supergiant Shell LMC 4 & LMC 5

    NASA Astrophysics Data System (ADS)

    Fujii, K.; Minamidani, T.; Mizuno, N.; Onishi, T.; Kawamura, A.; Muller, E.; Dawson, J.; Fukui, Y.

    2015-12-01

    The 12CO(J=3-2/1-0) and 13CO(J=3-2/1-0) observations with ASTE and Mopra telescopes have been carried out toward the giant molecular clouds (GMCs) in the N48/N49 regions in the Large Magellanic Cloud (LMC), which are located at the boundary of two kpc-scale Supergiant Shell (SGS) LMC 4 & LMC 5. The star formation is relatively evolved in the N48 region, which is just located at the boundary of SGSs, than in the N49 region. The clumps in the N48 show higher n(H2) and Tkin than those in the N49, but their densities are not so high as the LMC cluster forming clumps. The collision of two SGSs actually enhances the star formation but further evolution seem to be necessary for subsequent cluster formation.

  18. On the size distribution of newly formed grains in red supergiant atmospheres

    NASA Technical Reports Server (NTRS)

    Seab, C. Gregory; Snow, Theodore P.

    1989-01-01

    Theoretical ultraviolet extinction curves have been calculated for comparison with observed curves for circumstellar dust in M supergiants. The theoretical curves assume a silicate grain composition, because silicate grains are expected in the oxygen-rich environments that are observed. Calculations were performed with and without the inclusion of scattering into the beam, with largely similar results. A comparison of the computed curves with the observed ultraviolet extinction curve for circumstellar dust in Alpha Scorpii indicates that the size distribution of the circumstellar grains must cut off near 800 A; that is, there are few or no grains smaller than this. The conclusion is that smaller interstellar silicate grains, where they exist, must come from other sources such as grain fragmentation in shocks.

  19. Physical conditions near red giant and supergiant stars - an interpretation of SiO VLBI maps

    NASA Astrophysics Data System (ADS)

    Alcock, Charles; Ross, Randy R.

    1986-11-01

    Understanding the dynamical structure of circumstellar envelopes around cool giant and supergiant stars depends critically on the knowledge of what happens in the 'near zone' of the envelope, within a few stellar radii of the star. One probe with adequate angular resolution to study the near zone is VLBI observation of the SiO masers. It is shown that VLBI maps of VX Sgr establish that the particle density in the SiO masers is very high (about 10 to the 12th/cu cm), indicating that the masers form in dense cloudlets and not in a spherically expanding wind. The implications of these results for the mechanism of mass loss are discussed.

  20. The Type IIb Supernova 2013df and its Cool Supergiant Progenitor

    NASA Technical Reports Server (NTRS)

    VanDyk, Schuyler D.; Zeng, Weikang; Fox, Ori D.; Cenko, S. Bradley; Clubb, Kelsey I.; Filippenko, Alexei; Foley, Ryan J.; Miller, Adam A.; Smith, Nathan; Kelly, Patrick L.; Lee, William H.; Ben-Ami, Sagi; Gal-Yam, Avishay

    2014-01-01

    We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly of Type II b, with notable similarities to SN 1993J. From its luminosity at secondary maximum light, it appears that less Ni-56 (is approximately less than 0.06M) was synthesized in the SN 2013df explosion than was the case for the SNe II b 1993J, 2008ax, and 2011dh. Based on a comparison of the light curves, the SN 2013df progenitor must have been more extended in radius prior to explosion than the progenitor of SN 1993J. The total extinction for SN 2013dfis estimated to be A(sub V) = 0.30 mag. The metallicity at the SN location is likely to be solar. We have conducted Hubble Space Telescope(HST) Target of Opportunity observations of the SN with the Wide Field Camera 3, and from a precise comparison of these new observations to archival HST observations of the host galaxy obtained 14 yr prior to explosion, we have identified the progenitor of SN 2013df to be a yellow supergiant, somewhat hotter than a red supergiant progenitor for a normal Type II-Plateau SN. From its observed spectral energy distribution, assuming that the light is dominated by one star, the progenitor had effective temperature T(sub eff) = 4250+/-100 K and a bolometric luminosity L(sub bol) =10(exp 4.94+/-0.06) Solar Luminosity. This leads to an effective radius Reff = 545+/-65 Solar Radius. The star likely had an initial mass in the range of 13-17Solar Mass; however, if it was a member of an interacting binary system, detailed modeling of the system is required to estimate this mass more accurately. The progenitor star of SN 2013df appears to have been relatively similar to the progenitor of SN 1993J.

  1. The type IIb supernova 2013df and its cool supergiant progenitor

    SciTech Connect

    Van Dyk, Schuyler D.; Cenko, S. Bradley; Foley, Ryan J.; Miller, Adam A.; Smith, Nathan; Lee, William H.; Ben-Ami, Sagi; Gal-Yam, Avishay

    2014-02-01

    We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly of Type IIb, with notable similarities to SN 1993J. From its luminosity at secondary maximum light, it appears that less {sup 56}Ni (≲ 0.06 M {sub ☉}) was synthesized in the SN 2013df explosion than was the case for the SNe IIb 1993J, 2008ax, and 2011dh. Based on a comparison of the light curves, the SN 2013df progenitor must have been more extended in radius prior to explosion than the progenitor of SN 1993J. The total extinction for SN 2013df is estimated to be A{sub V} = 0.30 mag. The metallicity at the SN location is likely to be solar. We have conducted Hubble Space Telescope (HST) Target of Opportunity observations of the SN with the Wide Field Camera 3, and from a precise comparison of these new observations to archival HST observations of the host galaxy obtained 14 yr prior to explosion, we have identified the progenitor of SN 2013df to be a yellow supergiant, somewhat hotter than a red supergiant progenitor for a normal Type II-Plateau SN. From its observed spectral energy distribution, assuming that the light is dominated by one star, the progenitor had effective temperature T {sub eff} = 4250 ± 100 K and a bolometric luminosity L {sub bol} = 10{sup 4.94±0.06} L {sub ☉}. This leads to an effective radius R {sub eff} = 545 ± 65 R {sub ☉}. The star likely had an initial mass in the range of 13-17 M {sub ☉}; however, if it was a member of an interacting binary system, detailed modeling of the system is required to estimate this mass more accurately. The progenitor star of SN 2013df appears to have been relatively similar to the progenitor of SN 1993J.

  2. THE RED SUPERGIANT PROGENITOR OF SUPERNOVA 2012aw (PTF12bvh) IN MESSIER 95

    SciTech Connect

    Van Dyk, Schuyler D.; and others

    2012-09-10

    We report on the direct detection and characterization of the probable red supergiant (RSG) progenitor of the intermediate-luminosity Type II-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95; NGC 3351). We have identified the star in both Hubble Space Telescope images of the host galaxy, obtained 17-18 yr prior to the explosion, and near-infrared ground-based images, obtained 6-12 yr prior to the SN. The luminous supergiant showed evidence for substantial circumstellar dust, manifested as excess line-of-sight extinction. The effective total-to-selective ratio of extinction to the star was R'{sub V} Almost-Equal-To 4.35, which is significantly different from that of diffuse interstellar dust (i.e., R{sub V} = 3.1), and the total extinction to the star was therefore, on average, A{sub V} Almost-Equal-To 3.1 mag. We find that the observed spectral energy distribution for the progenitor star is consistent with an effective temperature of 3600 K (spectral type M3), and that the star therefore had a bolometric magnitude of -8.29. Through comparison with recent theoretical massive-star evolutionary tracks we can infer that the RSG progenitor had an initial mass 15 {approx}< M{sub ini}(M{sub Sun }) < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass {approx}17-18 M{sub Sun }. The circumstellar dust around the progenitor must have been destroyed in the explosion, as the visual extinction to the SN is found to be low (A{sub V} = 0.24 mag with R{sub V} = 3.1).

  3. Tests of two convection theories for red giant and red supergiant envelopes

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.; Chin, Chao-Wen

    1995-01-01

    Two theories of stellar envelope convection are considered here in the context of red giants and red supergiants of intermediate to high mass: Boehm-Vitense's standard mixing-length theory (MLT) and Canuto & Mazzitelli's new theory incorporating the full spectrum of turbulence (FST). Both theories assume incompressible convection. Two formulations of the convective mixing length are also evaluated: l proportional to the local pressure scale height (H(sub P)) and l proportional to the distance from the upper boundary of the convection zone (z). Applications to test both theories are made by calculating stellar evolutionary sequences into the red zone (z). Applications to test both theories are made by calculating stellar evolutionary sequences into the red phase of core helium burning. Since the theoretically predicted effective temperatures for cool stars are known to be sensitive to the assigned value of the mixing length, this quantity has been individually calibrated for each evolutionary sequence. The calibration is done in a composite Hertzsprung-Russell diagram for the red giant and red supergiant members of well-observed Galactic open clusters. The MLT model requires the constant of proportionality for the convective mixing length to vary by a small but statistically significant amount with stellar mass, whereas the FST model succeeds in all cases with the mixing lenghth simply set equal to z. The structure of the deep stellar interior, however, remains very nearly unaffected by the choices of convection theory and mixing lenghth. Inside the convective envelope itself, a density inversion always occurs, but is somewhat smaller for the convectively more efficient MLT model. On physical grounds the FST model is preferable, and seems to alleviate the problem of finding the proper mixing length.

  4. Quantitative spectroscopy of blue supergiants in metal-poor dwarf galaxy NGC 3109

    SciTech Connect

    Hosek, Matthew W. Jr.; Kudritzki, Rolf-Peter; Bresolin, Fabio; Urbaneja, Miguel A.; Przybilla, Norbert; Evans, Christopher J.; Pietrzyński, Grzegorz; Gieren, Wolfgang; Carraro, Giovanni E-mail: kud@ifa.hawaii.edu E-mail: Miguel.Urbaneja-Perez@uibk.ac.at E-mail: chris.evans@stfc.ac.uk E-mail: wgieren@astro-udec.cl

    2014-04-20

    We present a quantitative analysis of the low-resolution (∼4.5 Å) spectra of 12 late-B and early-A blue supergiants (BSGs) in the metal-poor dwarf galaxy NGC 3109. A modified method of analysis is presented which does not require use of the Balmer jump as an independent T {sub eff} indicator, as used in previous studies. We determine stellar effective temperatures, gravities, metallicities, reddening, and luminosities, and combine our sample with the early-B-type BSGs analyzed by Evans et al. to derive the distance to NGC 3109 using the flux-weighted gravity-luminosity relation (FGLR). Using primarily Fe-group elements, we find an average metallicity of [ Z-bar ] = –0.67 ± 0.13, and no evidence of a metallicity gradient in the galaxy. Our metallicities are higher than those found by Evans et al. based on the oxygen abundances of early-B supergiants ([ Z-bar ] = –0.93 ± 0.07), suggesting a low α/Fe ratio for the galaxy. We adjust the position of NGC 3109 on the BSG-determined galaxy mass-metallicity relation accordingly and compare it to metallicity studies of H II regions in star-forming galaxies. We derive an FGLR distance modulus of 25.55 ± 0.09 (1.27 Mpc) that compares well with Cepheid and tip of the red giant branch distances. The FGLR itself is consistent with those found in other galaxies, demonstrating the reliability of this method as a measure of extragalactic distances.

  5. Taux of the Binaries in the Northern Hemisphere F G K M Supergiants - Results of Five Years of Measurements with CORAVEL

    NASA Astrophysics Data System (ADS)

    Burki, G.; Mayor, M.

    Since May 1977, more than 1500 radial velocity measurements have been performed with CORAVEL on 265 northern F-M supergiants. Twenty new spectroscopic binaries have been detected and the orbital elements are determined for 6 systems. The total binary rate among F-M supergiants is evaluated to 31-38%. The relation between the orbital eccentricity and the period is examined in the case of systems having a component of class Ib.

  6. Seeing Stars Like Never Before: A Multi-Year Interferometric Imaging Study of Red Supergiants in the H-Band.

    NASA Astrophysics Data System (ADS)

    Norris, Ryan P.; Baron, Fabien

    2017-01-01

    As some of the largest stars, red supergiants (RSG) are ideal candidates for interferometric imaging. 3D radiative hydrodynamic (RHD) models suggest that RSG have large convection cells with lifetimes on the order of 1000s of days. Many imaging projects have hinted at the existence of these features but, until recently, we have lacked the angular resolution to directly compare models to observations. In this presentation, we discuss early results from a multi-year survey of red supergiants using the Michigan InfraRed Combinber (MIRC) on the Center for High Angular Resolution Astronomy (CHARA Array), which has a maximum baseline of 330 m. We will present H-band images of RSG spanning several years developed using a new machine learning based image reconstruction tool for interferometric data. We will also present fundamental parameters for the targets, and discuss the implications of these results on 1D model atmospheres and 3D RHD models of RSG.

  7. Discovery of a red supergiant counterpart to RX J004722.4-252051, a ULX in NGC 253

    NASA Astrophysics Data System (ADS)

    Heida, M.; Torres, M. A. P.; Jonker, P. G.; Servillat, M.; Repetto, S.; Roberts, T. P.; Walton, D. J.; Moon, D.-S.; Harrison, F. A.

    2015-11-01

    We present two epochs of near-infrared spectroscopy of the candidate red supergiant counterpart to RX J004722.4-252051, a ULX in NGC 253. We measure radial velocities of the object and its approximate spectral type by cross-correlating our spectra with those of known red supergiants. Our VLT/X-shooter spectrum is best matched by that of early M-type supergiants, confirming the red supergiant nature of the candidate counterpart. The radial velocity of the spectrum, taken on 2014 August 23, is 417 ± 4 km s-1. This is consistent with the radial velocity measured in our spectrum taken with Magellan/MMIRS on 2013 June 28, of 410 ± 70 km s-1, although the large error on the latter implies that a radial velocity shift expected for a black hole of tens of M⊙ can easily be hidden. Using nebular emission lines we find that the radial velocity due to the rotation of NGC 253 is 351 ± 4 km s-1 at the position of the ULX. Thus the radial velocity of the counterpart confirms that the source is located in NGC 253, but also shows an offset with respect to the local bulk motion of the galaxy of 66 ± 6 km s-1. We argue that the most likely origin for this displacement lies either in a SN kick, requiring a system containing a ≳ 50 M⊙ black hole, and/or in orbital radial velocity variations in the ULX binary system, requiring a ≳ 100 M⊙ black hole. We therefore conclude that RX J004722.4-252051 is a strong candidate for a ULX containing a massive stellar black hole.

  8. INTEGRAL Long-Term Monitoring of the Supergiant Fast X-Ray Transient XTE J1739-302

    NASA Technical Reports Server (NTRS)

    Blay, P.; Martinez-Nunez, S.; Negueruela, I.; Pottschmidt, K.; Smith, D. M.; Torrejon, J. M.; Reig, P.; Kretschmar, P.; Kreykenbohm, I.

    2008-01-01

    Context. In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are X-ray binary systems with a compact companion orbiting a supergiant star which show very short and bright outbursts in a series of activity periods overimposed on longer quiescent periods. Only very recently the first attempts to model the behaviour of these sources have been published, some of them within the framework of accretion from clumpy stellar winds. Aims. Our goal is to analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of the clumpy structure of the supergiant wind. Methods. We have used INTEGRAL and RXTE/PCA observations in order to obtain broad band (1 - 200 keV) spectra and light curves of XTE J1739-302 and investigate its X-ray spectrum and temporal variability. Results. We have found that XTE J1739-302 follows a much more complex behaviour than expected. Far from presenting a regular variability pattern, XTE J1739-302 shows periods of high, intermediate, and low flaring activity.

  9. An HST COS 'SNAPSHOT' spectrum of the K supergiant λ Vel (K4Ib-II)

    SciTech Connect

    Carpenter, Kenneth G.; Harper, Graham M.; Kober, Gladys; Nielsen, Krister E.; Wahlgren, Glenn M.

    2014-10-10

    We present a far-ultraviolet spectrum of the K4 Ib-II supergiant λ Vel obtained with the Hubble Space Telescope's Cosmic Origins Spectrograph (COS) as a part of the SNAPshot program 'SNAPing coronal iron' (GO 11687). The observation covers a wavelength region (1326-1467 Å) not previously recorded for λ Vel at a spectral resolving power of R ∼ 20,000 and displays strong emission and absorption features, superposed on a bright chromospheric continuum. Fluorescent excitation is responsible for much of the observed emission, mainly powered by strong H I Lyα and the O I (UV 2) triplet emission near λ1304. The molecular CO and H{sub 2} fluorescences are weaker than in the early-K giant α Boo while the Fe II and Cr II lines, also pumped by H I Lyα, are stronger in λ Vel. This pattern of relative line strengths between the two stars is explained by the lower iron-group element abundance in α Boo, which weakens that star's Fe II and Cr II emission without reducing the molecular fluorescences. The λ Vel spectrum shows fluorescent Fe II, Cr II, and H{sub 2} emission similar to that observed in the M supergiant α Ori, but more numerous well-defined narrow emissions from CO. The additional CO emissions are visible in the spectrum of λ Vel since that star does not have the cool, opaque circumstellar shells that surround α Ori and produce broad circumstellar CO (A-X) band absorptions that hide those emissions in the cooler star. The presence of Si IV emission in λ Vel indicates a ∼8 × 10{sup 4} K plasma that is mixed into the cooler chromosphere. Evidence of the stellar wind is seen in the C II λλ1334,1335 lines and in the blueshifted Fe II and Ni II wind absorption lines. Line modeling using Sobolev with Exact Integration for the C II lines indicates a larger terminal velocity (∼45 versus ∼30 km s{sup –1}) and turbulence (∼27 versus <21 km s{sup –1}) with a more quickly accelerating wind (β = 0.35 versus 0.7) at the time of this COS observation in

  10. Core collapse supernovae from blue supergiant progenitors : The evolutionary history of SN 1987A

    NASA Astrophysics Data System (ADS)

    Menon, Athira

    2015-08-01

    SN 1987A is historically one of the most remarkable supernova explosions to be seen from Earth. Due to the proximity of its location in the LMC, it remains the most well-studied object outside the solar system. It was also the only supernova whose progenitor was observed prior to its explosion.SN 1987A however, was a unique and enigmatic core collapse supernova. It was the first Type II supernova to have been observed to have exploded while its progenitor was a blue supergiant (BSG). Until then Type II supernovae were expected to originate from explosions of red supergiants (RSGs). A spectacular triple-ring nebula structure, rich in helium and nitrogen, was observed around the remnant, indicating a recent RSG phase before becoming a BSG. Even today it is not entirely understood what the evolutionary history may have been to cause a BSG to explode. The most commonly accepted hypothesis for its origin is the merger of a massive binary star system.An evolutionary scenario for such a binary system, was proposed by Podsiadlowski (1992) (P92). Through SPH simulations of the merger and the stellar evolution of the post-merger remnant, Ivanova & Podsiadlowski (2002) and (2003) (I&M) could successfully obtain the RSG to BSG transition of the progenitor.The aim of the present work is to produce the evolutionary history of the progenitor of SN 1987A and its explosion. We construct our models based on the results of P92 and I&M. Here, the secondary (less massive) star is accreted on the primary, while being simultaneously mixed in its envelope over a period of 100 years. The merged star is evolved until the onset of core collapse. For this work we use the 1-dimensional, implicit, hydrodynamical stellar evolution code, KEPLER. A large parameter space is explored, consisting of primary (16-20 Ms) and secondary masses (5-8 Ms), mixing boundaries, and accreting timescales. Those models whose end states match the observed properties of the progenitor of SN 1987A are exploded. The

  11. The quest for blue supergiants : The evolution of the progenitor of SN 1987A

    NASA Astrophysics Data System (ADS)

    Menon, Athira; Heger, Alexander

    2015-08-01

    SN 1987A is historically one of the most remarkable supernova explosions to be seen from Earth. Due to the proximity of its location in the LMC, it remains the most well-studied object outside the solar system. It was also the only supernova whose progenitor was observed prior to its explosion.SN 1987A however, was a unique and enigmatic core collapse supernova. It was the first Type II supernova to have been observed to have exploded while its progenitor was a blue supergiant (BSG). Until then Type II supernovae were expected to originate from explosions of red supergiants (RSGs). A spectacular triple-ring nebula structure, rich in helium and nitrogen, was observed around the remnant, indicating a recent RSG phase before becoming a BSG. Even today it is not entirely understood what the evolutionary history may have been to cause a BSG to explode. The most commonly accepted hypothesis for its origin is the merger of a massive binary star system.An evolutionary scenario for such a binary system, was proposed by Podsiadlowski (1992) (P92). Through SPH simulations of the merger and the stellar evolution of the post-merger remnant, Ivanova & Podsiadlowski (2002) and (2003) (I&M) could successfully obtain the RSG to BSG transition of the progenitor.The aim of the present work is to produce the evolutionary history of the progenitor of SN 1987A and its explosion. We construct our models based on the results of P92 and I&M. Here, the secondary (less massive) star is accreted on the primary, while being simultaneously mixed in its envelope over a period of 100 years. The merged star is evolved until the onset of core collapse. For this work we use the 1-dimensional, implicit, hydrodynamical stellar evolution code, KEPLER. A large parameter space is explored, consisting of primary (16-20 Ms) and secondary masses (5-8 Ms), mixing boundaries, and accreting timescales. Those models whose end states match the observed properties of the progenitor of SN 1987A are exploded. The

  12. X-RAY EMISSION FROM THE SUPERGIANT SHELL IN IC 2574

    SciTech Connect

    Yukita, Mihoko; Swartz, Douglas A.

    2012-05-01

    The M81 group member dwarf galaxy IC 2574 hosts a supergiant shell of current and recent star formation activity surrounding a 1000 Multiplication-Sign 500 pc hole in the ambient H I gas distribution. Chandra X-ray Observatory imaging observations reveal a luminous, L{sub X} {approx} 6.5 Multiplication-Sign 10{sup 38} erg s{sup -1} in the 0.3-8.0 keV band, point-like source within the hole but offset from its center and fainter diffuse emission extending throughout and beyond the hole. The star formation history at the location of the point source indicates a burst of star formation beginning {approx}25 Myr ago and currently weakening and there is a young nearby star cluster, at least 5 Myr old, bracketing the likely age of the X-ray source at between 5 and {approx}25 Myr. The source is thus likely a bright high-mass X-ray binary-either a neutron star or black hole accreting from an early B star undergoing thermal-timescale mass transfer through Roche lobe overflow. The properties of the residual diffuse X-ray emission are consistent with those expected from hot gas associated with the recent star formation activity in the region.

  13. Complexes of triggered star formation in supergiant shell of Holmberg II

    NASA Astrophysics Data System (ADS)

    Egorov, Oleg V.; Lozinskaya, Tatiana A.; Moiseev, Alexei V.; Shchekinov, Yuri A.

    2017-01-01

    We report a detailed analysis of all regions of current star formation in the walls of the supergiant H I shell (SGS) in the galaxy Holmberg II based on observations with a scanning Fabry-Perot interferometer at the Russian 6-m telescope. We compare the structure and kinematics of ionized gas with that of atomic hydrogen and with the stellar population of the SGS. Our deep Hα images and archival images taken by the Hubble Space Telescope demonstrate that current star formation episodes are larger and more complicated than previously thought: they represent unified star-forming complexes with sizes of several hundred pc rather than `chains' of separate bright nebulae in the walls of the SGS. The fact that we are dealing with unified complexes is evidenced by identified faint shell-like structures of ionized and neutral gas which connect several distinct bright H II regions. Formation of such complexes is due to the feedback of stars with very inhomogeneous ambient gas in the walls of the SGS. The arguments supporting an idea about the triggering of star formation in SGS by the H I supershells collision are presented. We also found a faint ionized supershell inside the H I SGS expanding with a velocity of no greater than 10-15 km s-1. Five OB stars located inside the inner supershell are sufficient to account for its radiation, although a possibility of leakage of ionizing photons from bright H II regions is not ruled out as well.

  14. Blue Supergiant X-Ray Binaries in the Nearby Dwarf Galaxy IC 10

    NASA Astrophysics Data System (ADS)

    Laycock, Silas G. T.; Christodoulou, Dimitris M.; Williams, Benjamin F.; Binder, Breanna; Prestwich, Andrea

    2017-02-01

    In young starburst galaxies, the X-ray population is expected to be dominated by the relics of the most massive and short-lived stars, black hole and neutron-star high-mass X-ray binaries (XRBs). In the closest such galaxy, IC 10, we have made a multi-wavelength census of these objects. Employing a novel statistical correlation technique, we have matched our list of 110 X-ray point sources, derived from a decade of Chandra observations, against published photometric data. We report an 8σ correlation between the celestial coordinates of the two catalogs, with 42 X-ray sources having an optical counterpart. Applying an optical color–magnitude selection to isolate blue supergiant (SG) stars in IC 10, we find 16 matches. Both cases show a statistically significant overabundance versus the expectation value for chance alignments. The blue objects also exhibit systematically higher {f}x/{f}v ratios than other stars in the same magnitude range. Blue SG-XRBs include a major class of progenitors of double-degenerate binaries, hence their numbers are an important factor in modeling the rate of gravitational-wave sources. We suggest that the anomalous features of the IC 10 stellar population are explained if the age of the IC 10 starburst is close to the time of the peak of interaction for massive binaries.

  15. The Envelopes of B[e] Supergiants in the Magellanic Clouds as Seen by Polarimetry

    NASA Astrophysics Data System (ADS)

    Seriacopi, D. B.; Carciofi, A. C.; Magalhães, A. M.

    2017-02-01

    B[e] supergiants (sgB[e]) are rare, massive post-main sequence stars. Their evolutionary status with respect to other objects on the H-R diagram is still unknown. These stars are surrounded by a non-spherically symmetric circumstellar envelope, from which arises a net intrinsic polarization. Therefore, spectropolarimetry is a very useful tool in the study of these objects. Since emission, absorption, and scattering processes are imprinted in the polarized flux, this technique can provide useful information about the circumstellar structure. We present a study of the envelope structure of RMC 82, a sgB[e] in the Large Magellanic Cloud, based on spectropolarimetric data. Our observations were obtained with the 8.2 m VLT/UT1 telescope at the Paranal Observatory (ESO). We analyzed the Balmer line formation loci, and their corresponding physical conditions. The data was modeled by a bimodal wind model of the circumstellar envelope, consisting of a slow, dense equatorial wind and a fast polar wind. The calculations were done with the radiative transfer code HDUST. Our results suggest that this geometry is indeed consistent with the RMC 82 data. Our best fit parameters are an opening angle of the disk of 15° and a total mass loss rate of 1.0×10-5 M⊙ yr-1 sr-1.

  16. X-Ray Observation of the Shocked Red Supergiant Wind of Cassiopeia A

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Joon; Park, Sangwook; Hughes, John P.; Slane, Patrick O.

    2014-07-01

    Cas A is a Galactic supernova remnant whose supernova explosion is observed to be of Type IIb from spectroscopy of its light echo. Having its SN type known, observational constraints on the mass-loss history of Cas A's progenitor can provide crucial information on the final fate of massive stars. In this paper, we study X-ray characteristics of the shocked ambient gas in Cas A using the 1 Ms observation carried out with the Chandra X-Ray Observatory and try to constrain the mass-loss history of the progenitor star. We identify thermal emission from the shocked ambient gas along the outer boundary of the remnant. Comparison of measured radial variations of spectroscopic parameters of the shocked ambient gas to the self-similar solutions of Chevalier show that Cas A is expanding into a circumstellar wind rather than into a uniform medium. We estimate a wind density n H ~ 0.9 ± 0.3 cm-3 at the current outer radius of the remnant (~3 pc), which we interpret as a dense slow wind from a red supergiant (RSG) star. Our results suggest that the progenitor star of Cas A had an initial mass around 16 M ⊙, and its mass before the explosion was about 5 M ⊙, with uncertainties of several tens of percent. Furthermore, the results suggest that, among the mass lost from the progenitor star (~11 M ⊙), a significant amount (more than 6 M ⊙) could have been via its RSG wind.

  17. High spatial resolution monitoring of the activity of BA supergiant winds

    NASA Astrophysics Data System (ADS)

    Chesneau, Olivier; Dessart, Luc; Kaufer, Andreas; Mourard, Denis; Stahl, Otmar; Prinja, Raman K.; Owocki, Stan P.

    2011-07-01

    There are currently two optical interferometry recombiners that can provide spectral resolutions better than 10000, AMBER/VLTI operating in the H-K bands, and VEGA/CHARA, recently commissioned, operating in the visible. These instruments are well suited to study the wind activity of the brightest AB supergiants in our vicinity, in lines such as Hα or Brγ. We present here the first observations of this kind, performed on Rigel (B8Ia) and Deneb (A2Ia). Rigel was monitored by AMBER in two campaigns, in 2006-2007 and 2009-2010, and observed in 2009 by VEGA; whereas Deneb was monitored in 2008-2009 by VEGA. The extension of the Hα and Brγ line forming regions were accurately measured and compared with CMFGEN models of both stars. Moreover, clear signs of activity were observed in the differential visibility and phases. These pioneer observations are still limited, but show the path for a better understanding of the spatial structure and temporal evolution of localized ejections using optical interferometry.

  18. Wolf-Rayet, Yellow and Red Supergiant in the single massive stars perspective

    NASA Astrophysics Data System (ADS)

    Georgy, Cyril; Hirschi, R.; Ekstrom, S.; Meynet, G.

    2013-06-01

    Rotation and mass loss are the key ingredients determining the fate of single massive stars. In recent years, a large effort has been made to compute whole grids of stellar models at different metallicities, including or not the effects of rotation, with the Geneva evolution code. In this talk, I will focus on the evolved stages of massive star evolution (red and yellow supergiants, Wolf-Rayet stars), in the framework of these new grids of models. I will highlight the effects of rotation and mass loss on the post-main sequence evolution of massive stars at solar and lower metallicity. In particular, I will discuss their impact on the maximum mass for a star to end its life as a RSG (leading to a type IIP supernova), on the possibility for a star to finish as a YSG, and on the initial mass ranges leading to various WR star subtypes. I will then compare the results predicted by our code with observed populations of evolved massive stars, bringing constraints on our computations, as well as some indications on the binary star fraction needed to reproduce them.

  19. The Physical Parameters of Red Supergiants: When Massive Stars Are as Cool as They Get

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Levesque, Emily; Olsen, Knut; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges

    2005-08-01

    Red supergiants (RSGs) are an important but poorly characterized stage in the evolution of massive stars. In the past, evolutionary models did not reproduce the ``observed" location of RSGs in the H-R diagram. However, our recent study using the new MARCS atmospheric models to fit spectrophotometry of Galactic RSGs has now led to good agreement between theory and observations (Levesque et al. 2005). With time generously granted by the TAC last year, we attempted to extend this study to the lower metallicity RSGs in the Magellanic Clouds, where the distribution of spectral types is quite different than that of the Milky Way (Elias et al. 1985; Massey & Olsen 2003). Unfortunately, our run was haunted by a ``grating ghost", rendering the observations in the near-UV and blue useless for our purposes, although good data were obtained in the red. We are now requesting time to complete these observations, using the last semester for which the RC Spectrograph is likely to be available. (The observations cannot be done with SOAR since the Goodman HTS lacks both a suitable grating and a blue-sensitive chip.) Reliable spectrophotometry in the blue is critical for deriving the effective temperatures, comparing the atomic lines Ca I(lambda) 4226 and Ca II H and K to the models, and in investigating the presence of peculiar reddening around these stars, presumably due to circumstellar dust.

  20. Identification of red supergiants in the Local Group with mid-IR photometry

    NASA Astrophysics Data System (ADS)

    Britavskiy, Nikolay; Bonanos, Alceste; Mehner, Andrea

    2015-08-01

    Star forming dwarf irregular (dIrr) galaxies serve as ideal laboratories for investigating the evolution and mass loss phenomenon of red supergiants (RSGs) within the context of different metallicities of host galaxies. Also, RSGs may be used for abundance determinations in dIrrs. The extremely low number of spectroscopically confirmed RSGs in external galaxies makes the identification of new RSGs statistically significant. We present a systematic survey of RSGs and luminous blue variables (LBVs) with the goal to complete the census of these objects in the Local Group. Using the fact that RSGs and LBVs are bright in mid-infrared colors due to dust, we propose and apply a technique that allows us to select dusty massive stars based on their [3.6] and [4.5] Spitzer photometry (Britavskiy et al. 2014). We present the results of our spectroscopic follow-up of luminous infrared sources in 7 nearby dIrrs (Phoenix, Pegasus, Sextans A, Sextans B, WLM, IC 10 and IC 1613) based on VLT/FORS2 and GTC/OSIRIS observations. In total we have observed ˜100 targets, among which we have so far identified 16 RSGs and 2 new emission line objects in these galaxies. Moreover, using the newly discovered RSGs, we have revised the mid-IR and optical photometric selection criteria for this type of objects, which can be applied to other galaxies of the Local Group and beyond.

  1. Similarities in the Structure of the Circumstellar Environments of B[e] Supergiants and Yellow Hypergiants

    NASA Astrophysics Data System (ADS)

    Aret, A.; Kolka, I.; Kraus, M.; Maravelias, G.

    2017-02-01

    Yellow hypergiants (YHGs) and B[e] supergiants (B[e]SGs), though in different phases in their evolution, have many features in common. This is partly due to the fact that both types of objects undergo strong, often asymmetric mass loss, and the ejected material accumulates in shells, rings, or disk-like structures, giving rise to emission from warm molecules and dust. We performed an optical spectroscopic survey of northern Galactic emission-line stars aimed at identifying tracers for the structure and kinematics of circumstellar environments. We identified two sets of lines, [O I] and [Ca II], which originate from the disks of B[e]SGs. The same set of lines is observed in V1302 Aql and V509 Cas, which are both hot YHGs. While V1302 Aql is known to have a disk-like structure, the kinematical broadening of the lines in V509 Cas suggests a Keplerian disk or ring around this star like their hotter B[e]SG counterparts.

  2. SPECTRAL TYPES OF RED SUPERGIANTS IN NGC 6822 AND THE WOLF-LUNDMARK-MELOTTE GALAXY

    SciTech Connect

    Levesque, Emily M.; Massey, Philip

    2012-07-15

    We present moderate-resolution spectroscopic observations of red supergiants (RSGs) in the low-metallicity Local Group galaxies NGC 6822 (Z = 0.4 Z{sub Sun} ) and Wolf-Lundmark-Melotte (WLM; Z = 0.1 Z{sub Sun} ). By combining these observations with reduction techniques for multislit data reduction and flux calibration, we are able to analyze spectroscopic data of 16 RSGs in NGC 6822 and spectrophotometric data of 11 RSGs in WLM. Using these observations, we determine spectral types for these massive stars, comparing them to Milky Way and Magellanic Cloud RSGs and thus extending observational evidence of the abundance-dependent shift of RSG spectral types to lower metallicities. In addition, we have uncovered two RSGs with unusually late spectral types (J000158.14-152332.2 in WLM, with a spectral type of M3 I, and J194453.46-144552.6 in NGC 6822, with a spectral type of M4.5 I) and a third RSG (J194449.96-144333.5 in NGC 6822) whose spectral type has varied from an M2.5 in 1997 to a K5 in 2008. All three of these stars could potentially be members of a recently discovered class of extreme RSG variables.

  3. Quantitative spectroscopic J-band study of red supergiants in Perseus OB-1

    SciTech Connect

    Gazak, J. Zachary; Kudritzki, Rolf; Davies, Ben; Bergemann, Maria; Plez, Bertrand

    2014-06-10

    We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ≈3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and χ Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra–one in pure LTE and one with non-LTE (NLTE) calculations for the most important diagnostic lines–we measure Z = +0.04 ± 0.10 (LTE) and Z = –0.04 ± 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than λ/δλ of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to 10 times farther by observing the integrated light of unresolved super star clusters.

  4. THE ULTRA-LONG GAMMA-RAY BURST 111209A: THE COLLAPSE OF A BLUE SUPERGIANT?

    SciTech Connect

    Gendre, B.; Cutini, S.; D'Elia, V.; Stratta, G.; Atteia, J. L.; Klotz, A.; Basa, S.; Boeer, M.; Coward, D. M.; Howell, E. J; Piro, L.

    2013-03-20

    We present optical, X-ray and gamma-ray observations of GRB 111209A, observed at a redshift of z = 0.677. We show that this event was active in its prompt phase for about 25000 s, making it the longest burst ever observed. This rare event could have been detected up to z {approx} 1.4 in gamma-rays. Compared to other long gamma-ray bursts (GRBs), GRB 111209A is a clear outlier in the energy-fluence and duration plane. The high-energy prompt emission shows no sign of a strong blackbody component, the signature of a tidal disruption event, or a supernova shock breakout. Given the extreme longevity of this event, and lack of any significant observed supernova signature, we propose that GRB 111209A resulted from the core-collapse of a low-metallicity blue supergiant star. This scenario is favored because of the necessity to supply enough mass to the central engine over a duration of thousands of seconds. Hence, we suggest that GRB 111209A could have more in common with population III stellar explosions, rather than those associated with normal long GRBs.

  5. THE PERIOD-LUMINOSITY RELATION OF RED SUPERGIANT STARS IN THE SMALL MAGELLANIC CLOUD

    SciTech Connect

    Yang Ming; Jiang, B. W. E-mail: bjiang@bnu.edu.cn

    2012-07-20

    The characteristics of light variation of red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) are analyzed based on the nearly 8-10 year data collected by the ASAS and MACHO projects. The 126 identified RSGs are classified into five categories accordingly: 20 with poor photometry, 55 with no reliable period, 6 with semi-regular variation, 15 with a long secondary period (LSP) and distinguishable short period, and 30 with only an LSP. For the semi-regular variables and the LSP variables with distinguishable short period, the K{sub S} -band period-luminosity (P-L) relation is analyzed and compared with that of the Galaxy, the Large Magellanic Cloud, and M33. It is found that the RSGs in these galaxies obey a similar P-L relation except for those in the Galaxy. In addition, the P-L relations in the infrared bands, namely, the 2MASS JHK{sub S} , Spitzer/IRAC, and Spitzer/MIPS 24 {mu}m bands, are derived with high reliability. The best P-L relation occurs in the Spitzer/IRAC [3.6] and [4.5] bands. Based on the comparison with the theoretical calculation of the P-L relation, the mode of pulsation of RSGs in the SMC is suggested to be the first-overtone radial mode.

  6. New spectroscopic and polarimetric observations of the A0 supergiant HD 92207

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Kholtygin, A. F.; Schöller, M.; Anderson, R. I.; Saesen, S.; González, J. F.; Ilyin, I.; Briquet, M.

    2015-02-01

    Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FORS 2 in spectropolarimetric mode revealed the presence of a longitudinal magnetic field of the order of a few hundred Gauss. However, the definite confirmation of the magnetic nature of this object remained pending due to the detection of short-term spectral variability probably affecting the position of line profiles in left- and right-hand polarized spectra. We present new magnetic field measurements of HD 92207 obtained on three different epochs in 2013 and 2014 using FORS 2 in spectropolarimetric mode. A 3σ detection of the mean longitudinal magnetic field using the entire spectrum, _all=104±34 G, was achieved in observations obtained in 2014 January. At this epoch, the position of the spectral lines appeared stable. Our analysis of spectral line shapes recorded in opposite circularly polarized light, i.e. in light with opposite sense of rotation, reveals that line profiles in the light polarized in a certain direction appear slightly split. The mechanism causing such a behaviour in the circularly polarized light is currently unknown. Trying to settle the issue of short-term variability, we searched for changes in the spectral line profiles on a time scale of 8-10 min using HARPS polarimetric spectra and on a time scale of 3-4 min using time series obtained with the CORALIE spectrograph. No significant variability was detected on these time scales during the epochs studied. Based on observations collected with the CORALIE echelle spectrograph mounted on the 1.2-m Swiss telescope at La Silla Observatory, data obtained at the European Southern Observatory (ESO Prg. 092.D-0209(A), and data obtained from the ESO Science Archive Facility under request MSCHOELLER 102067).

  7. A NEW DISTANCE TO M33 USING BLUE SUPERGIANTS AND THE FGLR METHOD

    SciTech Connect

    U, Vivian; Urbaneja, Miguel A.; Kudritzki, Rolf-Peter; Jacobs, Bradley A.; Bresolin, Fabio; Przybilla, Norbert E-mail: urbaneja@ifa.hawaii.ed E-mail: bjacobs@ifa.hawaii.ed E-mail: przybilla@sternwarte.uni-erlangen.d

    2009-10-20

    The quantitative spectral analysis of medium resolution optical spectra of A and B supergiants obtained with DEIMOS and ESI at the Keck Telescopes is used to determine a distance modulus of 24.93 +- 0.11 mag (968 +- 50 kpc) for the Triangulum Galaxy M33. The analysis yields stellar effective temperatures, gravities, interstellar reddening, and extinction, the combination of which provides a distance estimate via the flux-weighted gravity-luminosity relationship (FGLR). This result is based on an FGLR calibration that is continually being polished. An average reddening of (E(B - V)) approx 0.08 mag is found, with a large variation ranging from 0.01 to 0.16 mag, however, demonstrating the importance of accurate individual reddening measurements for stellar distance indicators in galaxies with evident signatures of interstellar absorption. The large-distance modulus found is in good agreement with recent work on eclipsing binaries, planetary nebulae, long-period variables, RR Lyrae stars, and also with Hubble Space Telescope (HST) observations of Cepheids, if reasonable reddening assumptions are made for the Cepheids. Since distances based on the tip of the red giant branch (TRGB) method found in the literature give conflicting results, we have used HST Advanced Camera for Surveys V- and I-band images of outer regions of M33 to determine a TRGB distance of 24.84 +- 0.10 mag, in basic agreement with the FGLR result. We have also determined stellar metallicities and discussed the metallicity gradient in the disk of M33. We find metallicity of Z {sub sun} at the center and 0.3 Z {sub sun} in the outskirts at a distance of one isophotal radius. The average logarithmic metallicity gradient is -0.07 +- 0.01 dex kpc{sup -1}. However, there is a large scatter around this average value, very similar to what has been found for the H II regions in M33.

  8. The chromosphere of VV cephei and the distribution of circumstellar dust around red giants and supergiants

    NASA Technical Reports Server (NTRS)

    Bauer, Wendy Hagen

    1992-01-01

    The work on this project has followed two separate paths of inquiry. The first project was entitled 'the Chromosphere of VV Cephei.' The examination of the archival spectra revealed significant changes in the spectra. Therefore, we obtained additional observing time with IUE to monitor the system during the summer of 1991. Short-term changes continue to be seen in both the overall spectrum and individual line profiles. Work continues on this object. The second project was entitled 'the Distribution of Circumstellar Dust around Red Giants and Supergiants.' A number of cool evolved stars are surrounded by dust shells of sufficient angular size as to appear extended in the IRAS survey data. The aim of this project has been to convolve the predictions of the flux distribution from model dust shells with the IRAS beam profiles in order to reproduce the observed IRAS scans. At the time of the last status report, the cross-scan profiles of the IRAS detectors had just been added to the modeling procedure. For scans in which the star passed near the detector center, there was no significant variation in predicted scan profile for different detectors. Scans in which the detector did not pass over the bright central star had been anticipated to be particularly useful in determining the dust distribution; however, significant differences in the predicted scan profiles were seen for different detector profiles. For this reason, and due to the cross-talk effects discussed in the previous status report, further work on the scans not including a central star has been postponed in favor of further analysis of scans passing over the central star.

  9. X-ray observation of the shocked red supergiant wind of Cassiopeia A

    SciTech Connect

    Lee, Jae-Joon; Park, Sangwook; Hughes, John P.; Slane, Patrick O.

    2014-07-01

    Cas A is a Galactic supernova remnant whose supernova explosion is observed to be of Type IIb from spectroscopy of its light echo. Having its SN type known, observational constraints on the mass-loss history of Cas A's progenitor can provide crucial information on the final fate of massive stars. In this paper, we study X-ray characteristics of the shocked ambient gas in Cas A using the 1 Ms observation carried out with the Chandra X-Ray Observatory and try to constrain the mass-loss history of the progenitor star. We identify thermal emission from the shocked ambient gas along the outer boundary of the remnant. Comparison of measured radial variations of spectroscopic parameters of the shocked ambient gas to the self-similar solutions of Chevalier show that Cas A is expanding into a circumstellar wind rather than into a uniform medium. We estimate a wind density n {sub H} ∼ 0.9 ± 0.3 cm{sup –3} at the current outer radius of the remnant (∼3 pc), which we interpret as a dense slow wind from a red supergiant (RSG) star. Our results suggest that the progenitor star of Cas A had an initial mass around 16 M {sub ☉}, and its mass before the explosion was about 5 M {sub ☉}, with uncertainties of several tens of percent. Furthermore, the results suggest that, among the mass lost from the progenitor star (∼11 M {sub ☉}), a significant amount (more than 6 M {sub ☉}) could have been via its RSG wind.

  10. Dense Molecular Clumps Associated with the Large Magellanic Cloud Supergiant Shells LMC 4 and LMC 5

    NASA Astrophysics Data System (ADS)

    Fujii, Kosuke; Minamidani, Tetsuhiro; Mizuno, Norikazu; Onishi, Toshikazu; Kawamura, Akiko; Muller, Erik; Dawson, Joanne; Tatematsu, Ken'ichi; Hasegawa, Tetsuo; Tosaki, Tomoka; Miura, Rie E.; Muraoka, Kazuyuki; Sakai, Takeshi; Tsukagoshi, Takashi; Tanaka, Kunihiko; Ezawa, Hajime; Fukui, Yasuo

    2014-12-01

    We investigate the effects of supergiant shells (SGSs) and their interaction on dense molecular clumps by observing the Large Magellanic Cloud (LMC) star-forming regions N48 and N49, which are located between two SGSs, LMC 4 and LMC 5. 12CO (J = 3-2, 1-0) and 13CO(J = 1-0) observations with the ASTE and Mopra telescopes have been carried out toward these regions. A clumpy distribution of dense molecular clumps is revealed with 7 pc spatial resolution. Large velocity gradient analysis shows that the molecular hydrogen densities (n(H2)) of the clumps are distributed from low to high density (103-105 cm-3) and their kinetic temperatures (T kin) are typically high (greater than 50 K). These clumps seem to be in the early stages of star formation, as also indicated from the distribution of Hα, young stellar object candidates, and IR emission. We found that the N48 region is located in the high column density H I envelope at the interface of the two SGSs and the star formation is relatively evolved, whereas the N49 region is associated with LMC 5 alone and the star formation is quiet. The clumps in the N48 region typically show high n(H2) and T kin, which are as dense and warm as the clumps in LMC massive cluster-forming areas (30 Dor, N159). These results suggest that the large-scale structure of the SGSs, especially the interaction of two SGSs, works efficiently on the formation of dense molecular clumps and stars.

  11. HD 179821 (V1427 Aql, IRAS 19114+0002) - a massive post-red supergiant star?

    NASA Astrophysics Data System (ADS)

    Şahin, T.; Lambert, David L.; Klochkova, Valentina G.; Panchuk, Vladimir E.

    2016-10-01

    We have derived elemental abundances of a remarkable star, HD 179821, with unusual composition (e.g. [Na/Fe] = 1.0 ± 0.2 dex) and extra-ordinary spectral characteristics. Its metallicity at [Fe/H] = 0.4 dex places it among the most metal-rich stars yet analysed. The abundance analysis of this luminous star is based on high-resolution and high-quality (S/N ≈ 120-420) optical echelle spectra from McDonald Observatory and Special Astronomy Observatory. The data includes five years of observations over 21 epochs. Standard 1D local thermodynamic equilibrium analysis provides a fresh determination of the atmospheric parameters over all epochs: Teff = 7350 ± 200 K, log g= +0.6 ± 0.3, and a microturbulent velocity ξ = 6.6 ± 1.6 km s-1 and [Fe/H] = 0.4 ± 0.2, and a carbon abundance [C/Fe] = -0.19 ± 0.30. We find oxygen abundance [O/Fe] = -0.25 ± 0.28 and an enhancement of 0.9 dex in N. A supersonic macroturbulent velocity of 22.0 ± 2.0 km s-1 is determined from both strong and weak Fe I and Fe II lines. Elemental abundances are obtained for 22 elements. HD 179821 is not enriched in s-process products. Eu is overabundant relative to the anticipated [X/Fe] ≈ 0.0. Some peculiarities of its optical spectrum (e.g. variability in the spectral line shapes) is noticed. This includes the line profile variations for H α line. Based on its estimated luminosity, effective temperature and surface gravity, HD 179821 is a massive star evolving to become a red supergiant and finally a Type II supernova.

  12. RED SUPERGIANT STARS IN THE LARGE MAGELLANIC CLOUD. I. THE PERIOD-LUMINOSITY RELATION

    SciTech Connect

    Yang Ming; Jiang, B. W. E-mail: bjiang@bnu.edu.cn

    2011-01-20

    From previous samples of red supergiants (RSGs) by various groups, 191 objects are assembled to compose a large sample of RSG candidates in LMC. For 189 of them, the identity as an RSG is verified by their brightness and color indexes in several near- and mid-infrared bands related to the Two Micron All Sky Survey (2MASS) JHK{sub S} bands and the Spitzer/IRAC and Spitzer/MIPS bands. From the visual time-series photometric observations by the ASAS and MACHO projects which cover nearly 8-10 years, the period and amplitude of light variation are analyzed carefully using both the phase dispersion minimization and Period04 methods. According to the properties of light variation, these objects are classified into five categories: (1) 20 objects are saturated in photometry or located in crowded stellar field with poor photometric results, (2) 35 objects with too complex variation to have any certain period, (3) 23 objects with irregular variation, (4) 16 objects with semi-regular variation, and (5) 95 objects with long secondary period (LSP) among which 31 have distinguishable short period and 51 have a long period shorter than 3000 days that can be determined with reasonable accuracy. For the semi-regular variables and the LSP variables with distinguishable short periods, the period-luminosity (P-L) relation is analyzed in the visual, near-infrared, and mid-infrared bands. It is found that the P-L relation is tight in the infrared bands such as the 2MASS JHK{sub S} bands and the Spitzer/IRAC bands, in particular in the Spitzer/IRAC [3.6] and [4.5] bands; meanwhile, the P-L relation is relatively sparse in the V band which may be caused by inhomogeneous interstellar extinction. The results are compared with others' P-L relationships for RSGs and the P-L sequences of red giants in LMC.

  13. The flux-weighted gravity-luminosity relationship of blue supergiant stars as a constraint for stellar evolution

    NASA Astrophysics Data System (ADS)

    Meynet, Georges; Kudritzki, Rolf-Peter; Georgy, Cyril

    2015-09-01

    Context. The flux-weighted gravity-luminosity relationship (FGLR) of blue supergiant stars (BSG) links their absolute magnitude to the spectroscopically determined flux-weighted gravity log g/T_text{eff ^4}. BSG are the brightest stars in the universe at visual light and the application of the FGLR has become a powerful tool for determining extragalactic distances. Aims: Observationally, the FGLR is a tight relationship with only small scatter. It is, therefore, ideal for using as a constraint for stellar evolution models. The goal of this work is to investigate whether stellar evolution can reproduce the observed FGLR and to develop an improved foundation for the FGLR as an extragalactic distance indicator. Methods: We used different grids of stellar models for initial masses between 9 and 40 M⊙ and for metallicities between Z = 0.002 and 0.014, with and without rotation, which were computed with various mass loss rates during the red supergiant phase. For each of these models, we discuss the details of post-main sequence evolution and construct theoretical FGLRs by means of population synthesis models that we then compare with the observed FGLR. Results: In general, the stellar evolution model FGLRs agree reasonably well with the observed one. There are, however, differences between the models, in particular with regard to the shape and width (scatter) in the flux-weighted gravity-luminosity plane. The best agreement is obtained with models that include the effects of rotation and assume that the large majority, if not all, of the observed BSG evolve toward the red supergiant phase and that only a few are evolving back from this stage. The effects of metallicity on the shape and scatter of the FGLR are small. Conclusions: The shape, scatter, and metallicity dependence of the observed FGLR are explained well by stellar evolution models. This provides a solid theoretical foundation for using this relationship as a robust extragalactic distance indicator.

  14. Cold gas in hot star clusters: the wind from the red supergiant W26 in Westerlund 1

    NASA Astrophysics Data System (ADS)

    Mackey, Jonathan; Castro, Norberto; Fossati, Luca; Langer, Norbert

    2015-10-01

    The massive red supergiant W26 in Westerlund 1 is one of a growing number of red supergiants shown to have winds that are ionized from the outside in. The fate of this dense wind material is important for models of second generation star formation in massive star clusters. Mackey et al. (2014, Nature, 512, 282) showed that external photoionization can stall the wind of red supergiants and accumulate mass in a dense static shell. We use spherically symmetric radiation-hydrodynamic simulations of an externally photoionized wind to predict the brightness distribution of Hα and [N II] emission arising from photoionized winds both with and without a dense shell. We analyse spectra of the Hα and [N II] emission lines in the circumstellar environment around W26 and compare them with simulations to investigate whether W26 has a wind that is confined by external photoionization. Simulations of slow winds that are decelerated into a dense shell show strongly limb-brightened line emission, with line radial velocities that are independent of the wind speed. Faster winds (≳22 km s-1) do not form a dense shell, have less limb-brightening, and the line radial velocity is a good tracer of the wind speed. The brightness of the [N II] and Hα lines as a function of distance from W26 agrees reasonably well with observations when only the line flux is considered. The radial velocity of the simulated winds disagrees with observations, however: the brightest observed emission is blueshifted by ≈25 km s-1 relative to the radial velocity of the star, whereas a spherically symmetric wind has the brightest emission at zero radial velocity because of limb brightening. Our results show that the bright nebula surrounding W26 must be asymmetric, and we suggest that it is confined by external ram pressure from the extreme wind of the nearby supergiant W9. We obtain a lower limit on the nitrogen abundance within the nebula of 2.35 times solar. The line ratio strongly favours photoionization

  15. A dark energy camera search for missing supergiants in the LMC after the advanced LIGO gravitational-wave event GW150914

    DOE PAGES

    Annis, J.

    2016-05-27

    The collapse of a stellar core is expected to produce gravitational waves (GWs), neutrinos, and in most cases a luminous supernova. Sometimes, however, the optical event could be significantly less luminous than a supernova and a direct collapse to a black hole, where the star just disappears, is possible. The GW event GW150914 was detected by the LIGO Virgo Collaboration via a burst analysis that gave localization contours enclosing the Large Magellanic Cloud (LMC). Shortly thereafter, we used DECam to observe 102 deg2 of the localization area, including 38 deg2 on the LMC for a missing supergiant search. We constructmore » a complete catalog of LMC luminous red supergiants, the best candidates to undergo invisible core collapse, and collected catalogs of other candidates: less luminous red supergiants, yellow supergiants, blue supergiants, luminous blue variable stars, and Wolf–Rayet stars. Of the objects in the imaging region, all are recovered in the images. The timescale for stellar disappearance is set by the free-fall time, which is a function of the stellar radius. Our observations at 4 and 13 days after the event result in a search sensitive to objects of up to about 200 solar radii. We conclude that it is unlikely that GW150914 was caused by the core collapse of a relatively compact supergiant in the LMC, consistent with the LIGO Collaboration analyses of the gravitational waveform as best interpreted as a high mass binary black hole merger. Lastly, we discuss how to generalize this search for future very nearby core-collapse candidates.« less

  16. A dark energy camera search for missing supergiants in the LMC after the advanced LIGO gravitational-wave event GW150914

    SciTech Connect

    Annis, J.

    2016-05-27

    The collapse of a stellar core is expected to produce gravitational waves (GWs), neutrinos, and in most cases a luminous supernova. Sometimes, however, the optical event could be significantly less luminous than a supernova and a direct collapse to a black hole, where the star just disappears, is possible. The GW event GW150914 was detected by the LIGO Virgo Collaboration via a burst analysis that gave localization contours enclosing the Large Magellanic Cloud (LMC). Shortly thereafter, we used DECam to observe 102 deg2 of the localization area, including 38 deg2 on the LMC for a missing supergiant search. We construct a complete catalog of LMC luminous red supergiants, the best candidates to undergo invisible core collapse, and collected catalogs of other candidates: less luminous red supergiants, yellow supergiants, blue supergiants, luminous blue variable stars, and Wolf–Rayet stars. Of the objects in the imaging region, all are recovered in the images. The timescale for stellar disappearance is set by the free-fall time, which is a function of the stellar radius. Our observations at 4 and 13 days after the event result in a search sensitive to objects of up to about 200 solar radii. We conclude that it is unlikely that GW150914 was caused by the core collapse of a relatively compact supergiant in the LMC, consistent with the LIGO Collaboration analyses of the gravitational waveform as best interpreted as a high mass binary black hole merger. Lastly, we discuss how to generalize this search for future very nearby core-collapse candidates.

  17. A Dark Energy Camera Search for Missing Supergiants in the LMC after the Advanced LIGO Gravitational-wave Event GW150914

    NASA Astrophysics Data System (ADS)

    Annis, J.; Soares-Santos, M.; Berger, E.; Brout, D.; Chen, H.; Chornock, R.; Cowperthwaite, P. S.; Diehl, H. T.; Doctor, Z.; Drlica-Wagner, A.; Drout, M. R.; Farr, B.; Finley, D. A.; Flaugher, B.; Foley, R. J.; Frieman, J.; Gruendl, R. A.; Herner, K.; Holz, D.; Kessler, R.; Lin, H.; Marriner, J.; Neilsen, E.; Rest, A.; Sako, M.; Smith, M.; Smith, N.; Sobreira, F.; Walker, A. R.; Yanny, B.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Bernstein, R. A.; Bertin, E.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Cenko, S. B.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Dietrich, J. P.; Eifler, T. F.; Evrard, A. E.; Fernandez, E.; Fischer, J.; Fong, W.; Fosalba, P.; Fox, D. B.; Fryer, C. L.; Garcia-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gutierrez, G.; Honscheid, K.; James, D. J.; Karliner, I.; Kasen, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Maia, M. A. G.; Martini, P.; Metzger, B. D.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Ogando, R.; Peoples, J.; Petravic, D.; Plazas, A. A.; Quataert, E.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, R. C.; Stebbins, A.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Thomas, R. C.; Tucker, D. L.; Vikram, V.; Wechsler, R. H.; Weller, J.; Wester, W.; DES Collaboration

    2016-06-01

    The collapse of a stellar core is expected to produce gravitational waves (GWs), neutrinos, and in most cases a luminous supernova. Sometimes, however, the optical event could be significantly less luminous than a supernova and a direct collapse to a black hole, where the star just disappears, is possible. The GW event GW150914 was detected by the LIGO Virgo Collaboration via a burst analysis that gave localization contours enclosing the Large Magellanic Cloud (LMC). Shortly thereafter, we used DECam to observe 102 deg2 of the localization area, including 38 deg2 on the LMC for a missing supergiant search. We construct a complete catalog of LMC luminous red supergiants, the best candidates to undergo invisible core collapse, and collected catalogs of other candidates: less luminous red supergiants, yellow supergiants, blue supergiants, luminous blue variable stars, and Wolf-Rayet stars. Of the objects in the imaging region, all are recovered in the images. The timescale for stellar disappearance is set by the free-fall time, which is a function of the stellar radius. Our observations at 4 and 13 days after the event result in a search sensitive to objects of up to about 200 solar radii. We conclude that it is unlikely that GW150914 was caused by the core collapse of a relatively compact supergiant in the LMC, consistent with the LIGO Collaboration analyses of the gravitational waveform as best interpreted as a high mass binary black hole merger. We discuss how to generalize this search for future very nearby core-collapse candidates.

  18. The identification of extreme asymptotic giant branch stars and red supergiants in M33 with 24 μm variability

    SciTech Connect

    Montiel, Edward J.; Clayton, Geoffrey C.; Johnson, Christopher B.; Srinivasan, Sundar; Engelbracht, Charles W.

    2015-02-01

    We present the first detection of 24 μm variability in 24 sources in the Local Group galaxy M33. These results are based on 4 epochs of Multiband Imaging Photometer for Spitzer observations, which are irregularly spaced over ∼750 days. We find that these sources are constrained exclusively to the Holmberg radius of the galaxy, which increases their chances of being members of M33. We have constructed spectral energy distributions (SEDs) ranging from the optical to the submillimeter to investigate the nature of these objects. We find that 23 of our objects are most likely heavily self-obscured, evolved stars, while the remaining source is the Giant H ii region, NGC 604. We believe that the observed variability is the intrinsic variability of the central star reprocessed through their circumstellar dust shells. Radiative transfer modeling was carried out to determine their likely chemical composition, luminosity, and dust production rate (DPR). As a sample, our modeling has determined an average luminosity of (3.8±0.9)×10{sup 4} L{sub ⊙} and a total DPR of (2.3±0.1)×10{sup −5} M{sub ⊙} yr{sup −1}. Most of the sources, given the high DPRs and short wavelength obscuration, are likely extreme asymptotic giant branch (XAGB) stars. Five of the sources are found to have luminosities above the classical AGB limit (M{sub bol} <−7.1 mag, L > 54,000 L{sub ⊙}), which classifies them as probable red supergiants (RSGs). Almost all of the sources are classified as oxygen-rich. As also seen in the LMC, a significant fraction of the dust in M33 is produced by a handful of XAGB and RSG stars.

  19. Visual, Near-IR, and TiO Spectrophotometry of Pulsating Giant and Supergiant M-Type Variable Stars

    NASA Astrophysics Data System (ADS)

    Wasatonic, R. P.; Guinan, E. F.

    1997-05-01

    Pulsating M-type giant and supergiant stars radiate mainly in the near to intermediate IR (1000-2000 nm). Since most prior long-term photometric observations have been done visually or with UBVRI filters, an on-going program was established to monitor selected stars using both wide-band visual (550 nm) and Wing (719 nm, 754 nm, and 1040 nm) intermediate band filters. Outer atmopsheric titanium-oxide (TiO) strenghts are calculated and compared with generated visual light curves to study correlations of stellar pulsa- tions with molecular formation. IR color temperatures are computed and are used in combination with measured bolome- tric magnitudes to estimate radii changes throughout pulsa- tional cycles. These results should provide information relevant for studies of internal structures, atmopsheres, and evolution of red giant and supergiant stars. Some stars currently being observed include Mira, Aldebaran, Alpha Her, Betelgeuse, V CVn, R Leo, and CE Tau. Additionally, a calibration of the Wing 3-color spectro- photometry sytem is in progress to correlate TiO strengths with known spectral types and near-IR color temperatures for the benefit of the community. Observations measuring spectral sub-type changes via cyclic pulsational variations in TiO-indices and near-IR color temperature changes will be more accurate once the calibration is completed. This work was in part supported by NSF grant AST-9315365, which we gratefully acknowledge.

  20. DISCOVERY OF A POSSIBLY SINGLE BLUE SUPERGIANT STAR IN THE INTRA-CLUSTER REGION OF VIRGO CLUSTER OF GALAXIES

    SciTech Connect

    Ohyama, Youichi; Hota, Ananda

    2013-04-20

    IC 3418 is a dwarf irregular galaxy falling into the Virgo cluster, and a 17 kpc long trail is seen behind the galaxy, which is considered to have formed due to ram pressure stripping. The trail contains compact knots and diffuse blobs of ultraviolet and blue optical emission and, thus, it is a clear site of recent star formation but in an unusual environment, surrounded by a million degree intra-cluster medium. We report on our optical spectroscopy of a compact source in the trail, SDSS J122952.66+112227.8, and show that the optical spectrum is dominated by emission from a massive blue supergiant star. If confirmed, our report would mark the farthest star with spectroscopic observation. We interpret that a massive O-type star formed in situ in the trail has evolved recently out of the main sequence into this blue supergiant phase, and now lacks any detectable spectral sign of its associated H II region. We argue that turbulence within the ram pressure striped gaseous trail may play a dominant role for the star formation within such trails.

  1. Swift-X-Ray Telescope Monitoring of the Candidate Supergiant Fast X-ray Transient IGR J16418-4532

    NASA Technical Reports Server (NTRS)

    Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Evans, P. A.; Vercellone, S.; Kennea, J. A.; Burrows, D. N.; Gehrels, N.

    2012-01-01

    We report on the Swift monitoring of the candidate supergiant fast X-ray transient (SFXT) IGR J16418-4532, for which both orbital and spin periods are known (approx. 3.7 d and approx.1250 s, respectively). Our observations, for a total of approx. 43 ks, span over three orbital periods and represent the most intense and complete sampling of the light curve of this source with a sensitive X-ray instrument. With this unique set of observations, we can address the nature of this transient. By applying the clumpy wind model for blue supergiants to the observed X-ray light curve, and assuming a circular orbit, the X-ray emission from this source can be explained in terms of the accretion from a spherically symmetric clumpy wind, composed of clumps with different masses, ranging from approx. 5 × 10(exp 16) to 10(exp 21) g. Our data suggest, based on the X-ray behaviour, that this is an intermediate SFXT.

  2. Swift/XRT Monitoring of the Candidate Supergiant Fast X-ray Transient IGR J16418-4532

    NASA Technical Reports Server (NTRS)

    Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Evans, P. A.; Vercellone, S.; Kennea, J. A.; Burrows, D. N.; Gehrels, N.

    2011-01-01

    We report on the Swift monitoring of the candidate supergiant fast X-ray transient (SFXT) IGR J16418.4532, for which both orbital and spin periods are known (approx. 3.7d and approx. 1250 s, respectively). Our observations, for a total of approx. 43 ks, span over three orbital periods and represent the most intense and complete sampling of the light curve of this source with a sensitive X-ray instrument. With this unique set of observations we can address the nature of this transient. By applying the clumpy wind model for blue supergiants to the observed X-ray light curve, and assuming a circular orbit, the X-ray emission from this source can be explained in terms of the accretion from a spherically symmetric clumpy wind, composed of clumps with different masses, ranging from 5 X 10(exp 16) g to 10(exp 21) g. Our data suggest, based on the X-ray behaviour, that this is an intermediate SFXT

  3. VLTI/AMBER Studies of the Atmospheric Structure and Fundamental Parameters of Red Giant and Supergiant Stars

    NASA Astrophysics Data System (ADS)

    Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Abellan, F. J.; Chiavassa, A.; Fabregat, J.; Freytag, B.; Guirado, J. C.; Hauschildt, P. H.; Marti-Vidal, I.; Quirrenbach, A.; Scholz, M.; Wood, P. R.

    2015-08-01

    We present recent near-IR interferometric studies of red giant and supergiant stars, which are aimed at obtaining information on the structure of the atmospheric layers and constraining the fundamental parameters of these objects. The observed visibilities of six red supergiants (RSGs), and also of one of the five red giants observed, indicate large extensions of the molecular layers, as previously observed for Mira stars. These extensions are not predicted by hydrostatic PHOENIX model atmospheres, hydrodynamical (RHD) simulations of stellar convection, or self-excited pulsation models. All these models based on parameters of RSGs lead to atmospheric structures that are too compact compared to our observations. We discuss how alternative processes might explain the atmospheric extensions for these objects. As the continuum appears to be largely free of contamination by molecular layers, we can estimate reliable Rosseland angular radii for our stars. Together with distances and bolometric fluxes, we estimate the effective temperatures and luminosities of our targets, locate them in the HR diagram, and compare their positions to recent evolutionary tracks.

  4. The Reddening of Red Supergiants: When Smoke Gets in Your Eyes

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Plez, Bertrand; Levesque, Emily M.; Olsen, K. A. G.; Clayton, Geoffrey C.; Josselin, Eric

    2005-12-01

    Deriving the physical properties of red supergiants (RSGs) depends on accurate corrections for reddening by dust. We use our recent modeling of the optical spectra of RSGs to address this topic. First, we find that previous broadband studies have underestimated the correction for extinction in the visible, and hence the luminosities (if derived from V); the shift in the effective wavelengths of the standard B and V bandpasses necessitates using an effective value of the ratio R'V=4.2 to correct broadband photometry of RSGs if RV=3.1 for early-type stars viewed through the same dust, where we have assumed the standard reddening law of Cardelli and coauthors. Use of the Fitzpatrick reddening law would lead to R'V=3.8, as well as slightly lower values of extinction derived from spectrophotometry, but results in slightly poorer fits. Second, we find that a significant fraction of RSGs in Galactic OB associations and clusters show up to several magnitudes of excess visual extinction compared to OB stars in the same regions; we argue that this is likely due to circumstellar dust around the RSGs. We also show that the RSG dust production rate (as indicated by the 12 μm excess) is well correlated with bolometric luminosity, contrary to what has been found by earlier studies. The stars with the highest amount of extra visual extinction also show significant near-UV (NUV) excesses compared to the stellar models reddened by the standard reddening law. This NUV excess is likely due to scattering of the star's light by the dust and/or a larger average grain size than that typical of grains found in the diffuse interstellar medium. Similar excesses have been attributed to circumstellar dust around R Coronae Borealis stars. Finally, we estimate that the RSGs contribute dust grains at the rate of 3×10-8Msolar yr-1 kpc-2 in the solar neighborhood, comparable to what we estimate for late-type WCs, 1×10-7Msolar yr-1 kpc-2. In the solar neighborhood this represents only a few

  5. X-ray, UV and optical analysis of supergiants: ɛ Ori

    NASA Astrophysics Data System (ADS)

    Puebla, Raul E.; Hillier, D. John; Zsargó, Janos; Cohen, David H.; Leutenegger, Maurice A.

    2016-03-01

    We present a multi-wavelength (X-ray to optical) analysis, based on non-local thermodynamic equilibrium photospheric+wind models, of the B0 Ia-supergiant: ɛ Ori. The aim is to test the consistency of physical parameters, such as the mass-loss rate and CNO abundances, derived from different spectral bands. The derived mass-loss rate is {dot {M}} / {√{f_{∞}}} {˜} 1.6 × 10-6 M⊙ yr-1 where f∞ is the volume filling factor. However, the S IV λλ1062,1073 profiles are too strong in the models; to fit the observed profiles it is necessary to use f∞ <0.01. This value is a factor of 5 to 10 lower than inferred from other diagnostics, and implies {dot{M}} ≲ 1 × 10^{-7} M⊙ yr-1. The discrepancy could be related to porosity-vorosity effects or a problem with the ionization of sulphur in the wind. To fit the UV profiles of N V and O VI it was necessary to include emission from an interclump medium with a density contrast (ρcl/ρICM) of ˜100. X-ray emission in H/He like and Fe L lines was modelled using four plasma components located within the wind. We derive plasma temperatures from 1 × 106 to 7 × 106 K, with lower temperatures starting in the outer regions (R0 ˜ 3-6 R*), and a hot component starting closer to the star (R0 ≲ 2.9 R*). From X-ray line profiles we infer {dot{M}} < 4.9 × 10-7 M⊙ yr-1. The X-ray spectrum (≥0.1 kev) yields an X-ray luminosity LX ˜ 2.0 × 10-7Lbol, consistent with the superion line profiles. X-ray abundances are in agreement with those derived from the UV and optical analysis: ɛ Ori is slightly enhanced in nitrogen and depleted in carbon and oxygen, evidence for CNO processed material.

  6. Wind Variability of B Supergiants. No. 2; The Two-component Stellar Wind of gamma Arae

    NASA Technical Reports Server (NTRS)

    Prinja, R. K.; Massa, D.; Fullerton, A. W.; Howarth, I. D.; Pontefract, M.

    1996-01-01

    The stellar wind of the rapidly rotating early-B supergiant, gamma Ara, is studied using time series, high-resolution IUE spectroscopy secured over approx. 6 days in 1993 March. Results are presented based on an analysis of several line species, including N(N), C(IV), Si(IV), Si(III), C(II), and Al(III). The wind of this star is grossly structured, with evidence for latitude-dependent mass loss which reflects the role of rapid rotation. Independent, co-existing time variable features are identified at low-velocity (redward of approx. -750 km/s) and at higher-speeds extending to approx. -1500 km/s. The interface between these structures is 'defined' by the appearance of a discrete absorption component which is extremely sharp (in velocity space). The central velocity of this 'Super DAC' changes only gradually, over several days, between approx. -400 and -750 km/s in most of the ions. However, its location is shifted redward by almost 400 km/s in Al(III) and C(II), indicating that the physical structure giving rise to this feature has a substantial velocity and ionization jump. Constraints on the relative ionization properties of the wind structures are discussed, together with results based on SEI line-profile-fitting methods. The overall wind activity in gamma Ara exhibits a clear ion dependence, such that low-speed features are promoted in low-ionization species, including Al(III), C(II), and Si(III). We also highlight that - in contrast to most OB stars - there are substantial differences in the epoch-to-epoch time-averaged wind profiles of gamma Ara. We interpret the results in terms of a two-component wind model for gamma Ara, with an equatorially compressed low ionization region, and a high speed, higher-ionization polar outflow. This picture is discussed in the context of the predicted bi-stability mechanism for line-driven winds in rapidly rotating early-B type stars, and the formation of compressed wind regions in rapidly rotating hot stars. The apparent

  7. Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

    NASA Astrophysics Data System (ADS)

    Kraus, M.; Cidale, L. S.; Arias, M. L.; Maravelias, G.; Nickeler, D. H.; Torres, A. F.; Borges Fernandes, M.; Aret, A.; Curé, M.; Vallverdú, R.; Barbá, R. H.

    2016-10-01

    Context. B[e] supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims: We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud B[e] supergiant LHA 120-S 73. Methods: High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from [Ca ii] and [O i], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results: All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160-6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen- and carbon-rich grain species, which indicates a long-lived, stable dusty disk. We cannot confirm the previously reported high value for the stellar rotation velocity. He i λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its

  8. Disentangling the System Geometry of the Supergiant Fast X-Ray Transient IGR J11215-5952 with Swift

    NASA Astrophysics Data System (ADS)

    Romano, P.; Sidoli, L.; Cusumano, G.; Vercellone, S.; Mangano, V.; Krimm, H. A.

    2009-05-01

    IGR J11215-5952 is a hard X-ray transient source discovered in 2005 April with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) and a member of the new class of high-mass X-ray binaries, the supergiant fast X-ray transients (SFXTs). While INTEGRAL and Rossi X-Ray Timing Explorer observations have shown that the outbursts occur with a periodicity of ~330 days, Swift data have recently demonstrated that the true outburst period is ~165 days. IGR J11215-5952 is the first discovered SFXT displaying periodic outbursts, which are possibly related to the orbital period. The physical mechanism responsible for the X-ray outbursts in SFXTs is still debated. The main hypotheses proposed to date involve the structure of the companion wind or gated mechanisms related to the properties of the compact object. We test our proposed model which explains the outbursts from SFXTs as being due to the passage of the neutron star inside the equatorially enhanced wind from the supergiant companion. We performed a Guest Investigator observation with Swift that lasted 20 ks and several follow-up Target of Opportunity (ToO) observations, for a total of ~32 ks, during the expected "apastron" passage (defined assuming an orbital period of ~330 days), between 2008 June 16 and July 4. The characteristics of this "apastron" outburst are quite similar to those previously observed during the "periastron" outburst of 2007 February 9. The mean spectrum of the bright peaks can be fitted with an absorbed power-law model with a photon index of 1 and an absorbing column of ~1022 cm-2. This outburst reached luminosities of ~1036 erg s-1 (1-10 keV), comparable with those measured in 2007. The light curve can be modeled with the parameters obtained by Sidoli et al. for the 2007 February 9 outburst, although some differences can be observed in its shape. The properties of the rise to this new outburst and the comparison with the previous outbursts allow us to suggest that the true orbital

  9. RED SUPERGIANTS AS COSMIC ABUNDANCE PROBES: THE FIRST DIRECT METALLICITY DETERMINATION OF NGC 4038 IN THE ANTENNAE

    SciTech Connect

    Lardo, C.; Davies, B.; Kudritzki, R-P.; Gazak, J. Z.; Evans, C. J.; Patrick, L. R.; Bergemann, M.; Plez, B.

    2015-10-20

    We present a direct determination of the stellar metallicity in the close pair galaxy NGC 4038 (D = 20 Mpc) based on the quantitative analysis of moderate-resolution KMOS/Very Large Telescope spectra of three super star clusters. The method adopted in our analysis has been developed and optimized to measure accurate metallicities from atomic lines in the J-band of single red supergiant (RSG) or RSG-dominated star clusters. Hence, our metallicity measurements are not affected by the biases and poorly understood systematics inherent to strong line H ii methods, which are routinely applied to massive data sets of galaxies. We find [Z] = +0.07 ± 0.03 and compare our measurements to H ii strong line calibrations. Our abundances and literature data suggest the presence of a flat metallicity gradient, which can be explained as redistribution of metal-rich gas following the strong interaction.

  10. The supergiant amphipod Alicella gigantea (Crustacea: Alicellidae) from hadal depths in the Kermadec Trench, SW Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Jamieson, A. J.; Lacey, N. C.; Lörz, A.-N.; Rowden, A. A.; Piertney, S. B.

    2013-08-01

    Here we provide the first record of the 'supergiant' amphipod Alicella gigantea Chevreux, 1899 (Alicellidae) from the Southern Hemisphere, and extend the known bathymetric range by over 1000 m to 7000 m. An estimated nine individuals were observed across 1500 photographs taken in situ by baited camera at 6979 m in the Kermadec Trench, SW Pacific Ocean. Nine specimens, ranging in length from 102 to 290 mm were recovered by baited trap at depths of 6265 m and 7000 m. Mitochondrial and nuclear DNA sequences obtained indicate a cosmopolitan distribution for the species. Data and observations from the study are used to discuss the reason for gigantism in this species, and its apparently disjunct geographical distribution.

  11. Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars

    NASA Technical Reports Server (NTRS)

    Maggio, A.; Vaiana, G. S.; Haisch, B. M.; Stern, R. A.; Bookbinder, J.

    1990-01-01

    Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emissions more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary.

  12. Line-profile microvariability in OB-star spectra: the Supergiant λ Cep (O6If(n))

    NASA Astrophysics Data System (ADS)

    Kholtygin, A. F.; Sudnik, N. P.; Burlakova, T. E.; Valyavin, G. G.

    2011-12-01

    We observed the bright O6If(n) supergiant λ Cep in 1997 with the 6-m optical telescope of the Special Astrophysical Observatory and in 2007 with the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). A total of 90 spectra of the star were acquired, with good time resolution (10 minutes), signal-to-noise ratios 150-300, and spectral resolutions of 45 000-60 000. We detected line-profile variations of H, HeI, and HeII lines. It is suggested that the detected variations are due to non-radial photospheric pulsations and the star's rotation (rotational profile modulation).

  13. Synchrotron radiation from the winds of O supergiants - Tb = 10 to the 7. 6th K at 60 stellar radii

    SciTech Connect

    Phillips, R.B.; Titus, M.A. )

    1990-08-01

    Results are presented on VLBI measurements of the nonthermal radio components around two O supergiant stars: Cyg OB2 No. 9 and HD 167971. The measurements were used to characterize the brightness temperature of the emission and to measure the size of compact 5-10 mJy components in these stars, reported by Bieging et al. (1989). The sizes found for the 5-10 mJy components are consistent with the free-free wind radii, indicating that the compact companions are not the sources of nonthermal radiation. Results suggest that there is a small fractional population (10 to the -4th to 10 to the -7th) of ultrarelativistic electrons (Teff of about 10 to the 11th K) coexisting with the stellar wind, which emit optically thin synchrotron radiation. This is in agreement with the synchrotron model of White (1985). 21 refs.

  14. Near-Infrared Photometric Properties of Red Supergiant Stars in Neaby Galaxies: NGC 4214, NGC 4736 and M51

    NASA Astrophysics Data System (ADS)

    Jung, DooSeok; Chun, Sang-Hyun; Choudhury, Samyaday; Sohn, Young-Jong

    2017-01-01

    Red supergiant stars (RSGs) are post-main sequence phase of massive stars which can be easily resolved in nearby galaxies due to their bright luminosity as compared to the low-mass stars. RSGs are cool, and hence have a dominant light output at near-infrared (NIR) wavelengths. To investigate the photometric properties of RSGs in a few nearby galaxies, we observed NGC 4214, NGC 4736 and M51 by using the WFCAM detector mounted on the UKIRT telescope at Hawaii, and obtained the NIR (JHK bands) imaging data. After carrying out the photometry, the age ranges of RSGs in each galaxy were estimated by over-plotting PARSEC isochrones to the (J-K, K) colour-magnitude diagram: log(tyr) = 6.9 - 7.3 for NGC 4214; log(tyr) = 7.0 - 8.0 for NGC 4736; and log(tyr) = 6.7 - 6.9 for M51. The effective temperatures and luminosities of RSGs were calculated using MARCS synthetic fluxes, and these results were used to compare the properties of RSGs in Hertzsprung-Russell (H-R) diagram of dominant H II regions within each galaxy, over-plotted with PARSEC evolutionary tracks. The RSGs in NGC 4214 and NGC 4736 are found to have a mass of 9 M⊙ - 30 M⊙, and the maximum luminosities found to be almost constant with log(L/L⊙) = 5.6 - 5.7. However, the location of the RSGs in the H-R diagram are not consistent with the evolutionary tracks for M51.(Key Words: stars: massive - supergiants - galaxies: photometry - galaxies: stellar content - infrared: stars)

  15. The VLT-FLAMES Tarantula Survey . XXIV. Stellar properties of the O-type giants and supergiants in 30 Doradus

    NASA Astrophysics Data System (ADS)

    Ramírez-Agudelo, O. H.; Sana, H.; de Koter, A.; Tramper, F.; Grin, N. J.; Schneider, F. R. N.; Langer, N.; Puls, J.; Markova, N.; Bestenlehner, J. M.; Castro, N.; Crowther, P. A.; Evans, C. J.; García, M.; Gräfener, G.; Herrero, A.; van Kempen, B.; Lennon, D. J.; Maíz Apellániz, J.; Najarro, F.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Taylor, W. D.; Vink, J. S.

    2017-04-01

    Context. The Tarantula region in the Large Magellanic Cloud (LMC) contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and mass-loss properties. Aims: Using ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to determine stellar, photospheric and wind properties of 72 presumably single O-type giants, bright giants and supergiants and to confront them with predictions of stellar evolution and of line-driven mass-loss theories. Methods: We apply an automated method for quantitative spectroscopic analysis of O stars combining the non-LTE stellar atmosphere model fastwind with the genetic fitting algorithm pikaia to determine the following stellar properties: effective temperature, surface gravity, mass-loss rate, helium abundance, and projected rotational velocity. The latter has been constrained without taking into account the contribution from macro-turbulent motions to the line broadening. Results: We present empirical effective temperature versus spectral subtype calibrations at LMC-metallicity for giants and supergiants. The calibration for giants shows a +1kK offset compared to similar Galactic calibrations; a shift of the same magnitude has been reported for dwarfs. The supergiant calibrations, though only based on a handful of stars, do not seem to indicate such an offset. The presence of a strong upturn at spectral type O3 and earlier can also not be confirmed by our data. In the spectroscopic and classical Hertzsprung-Russell diagrams, our sample O stars are found to occupy the region predicted to be the core hydrogen-burning phase by state-of-the-art models. For stars initially more massive than approximately 60 M⊙, the giant phase already appears relatively early on in the evolution; the supergiant phase develops later. Bright giants, however, are not

  16. High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.

    2014-01-01

    Context. The mass-loss mechanism in red giants and red supergiants is not yet understood well. The SiO fundamental lines near 8 μm are potentially useful for probing the outer atmosphere, which is essential for clarifying the mass-loss mechanism. However, these lines have been little explored until now. Aims: We present high spectral resolution spectroscopic observations of the SiO fundamental lines near 8.1 μm in 16 bright red giants and red supergiants. Our sample consists of seven normal (i.e., non-Mira) K-M giants (from K1.5 to M6.5), three Mira stars, three optically bright red supergiants, two dusty red supergiants, and the enigmatic object GCIRS3 near the Galactic center. Methods: Our program stars were observed between 8.088 μm and 8.112 μm with a spectral resolution of 30 000 using VLT/VISIR. Results: We detected SiO fundamental lines in all of our program stars except for GCIRS3. The SiO lines in normal K and M giants as well as optically bright (i.e., not dusty) red supergiants do not show P-Cyg profiles or blueshifts, which means the absence of systematic outflows in the SiO line forming region. We detected P-Cyg profiles in the SiO lines in the dusty red supergiants VY CMa and VX Sgr, with the latter object being a new detection. These SiO lines originate in the outflowing gas with the thermal dust continuum emission seen as the background. The outflow velocities of the SiO line forming region in VY CMa and VX Sgr are estimated to be 27 km s-1 and 17 km s-1, respectively. We derived basic stellar parameters (effective temperature, surface gravity, luminosity, and mass) for the normal K-M giants and optically bright red supergiants in our sample and compared the observed VISIR spectra with synthetic spectra predicted from MARCS photospheric models. Most of the SiO lines observed in the program stars warmer than ~3400 K are reasonably reproduced by the MARCS models, which allowed us to estimate the silicon abundance as well as the 28Si/29Si and 28Si

  17. Quantitative Studies of the Far-Ultraviolet, Ultraviolet, and Optical Spectra of Late O- and Early B-Type Supergiants in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Evans, C. J.; Crowther, P. A.; Fullerton, A. W.; Hillier, D. J.

    2004-08-01

    We present quantitative studies of eight late O- and early B-type supergiants in the Magellanic Clouds using far-ultraviolet Far Ultraviolet Spectroscopic Explorer, ultraviolet International Ultraviolet Explorer/Hubble Space Telescope, and optical VLT-UVES spectroscopy. Temperatures, mass-loss rates, and CNO abundances are obtained using the non-LTE, spherical, line-blanketed model atmosphere code of Hillier & Miller. We support recent results for lower temperatures of OB-type supergiants as a result of stellar winds and blanketing, which amounts to ~2000 K at B0 Ia. In general, Hα-derived mass-loss rates are consistent with UV and far-UV spectroscopy, although from consideration of the S IV λλ1063, 1073 doublet, clumped winds are preferred over homogenous models. AV 235 (B0 Iaw) is a notable exception, which has an unusually strong Hα profile that is inconsistent with the other Balmer lines and UV wind diagnostics. We also derive CNO abundances for our sample, revealing substantial nitrogen enrichment, with carbon and oxygen depletion. Our results are supported by comparison with the Galactic supergiant HD 2905 (BC0.7 Ia) for which near-solar CNO abundances are obtained. This bolsters previous suggestions that ``normal'' OB-type supergiants exhibit atmospheric compositions indicative of partial CNO processing. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated by Johns Hopkins University under NASA contract NAS5-32985. Also based in part on observations collected at the European Southern Observatory Very Large Telescope in program 67.D-0238, plus archival data obtained with the NASA-ESA Hubble Space Telescope and the NASA-ESA-PPARC International Ultraviolet Explorer.

  18. Broad Balmer Wings in BA Hyper/Supergiants Distorted by Diffuse Interstellar Bands: Five Examples in the 30 Doradus Region from the VLT-FLAMES Tarantula Survey

    NASA Astrophysics Data System (ADS)

    Walborn, Nolan R.; Sana, Hugues; Evans, Christopher J.; Taylor, William D.; Sabbi, Elena; Barbá, Rodolfo H.; Morrell, Nidia I.; Maíz Apellániz, Jesús; Sota, Alfredo; Dufton, Philip L.; McEvoy, Catherine M.; Clark, J. Simon; Markova, Nevena; Ulaczyk, Krzysztof

    2015-08-01

    Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them.

  19. A numerical investigation of wind accretion in persistent Supergiant X-ray Binaries I - Structure of the flow at the orbital scale

    NASA Astrophysics Data System (ADS)

    El Mellah, I.; Casse, F.

    2017-01-01

    Classical Supergiant X-ray Binaries host a neutron star orbiting a supergiant OB star and display persistent X-ray luminosities of 1035 to 1037 erg· s-1. The stellar wind from the massive companion is believed to be the main source of matter accreted by the compact object. With this first paper, we introduce a ballistic model to evaluate the influence of the orbital effects on the structure of the accelerating winds which participate to the accretion process. Thanks to the parametrization we retained and the numerical pipeline we designed, we can investigate the supersonic flow and the subsequent observables as a function of a reduced set of characteristic numbers and scales. We show that the shape of the permanent flow is entirely determined by the mass ratio, the filling factor, the Eddington factor and the α-force multiplier which drives the stellar wind acceleration. Provided scales such as the orbital period are known, we can trace back the observables to evaluate the mass accretion rates, the accretion mechanism, the shearing of the inflow and the stellar parameters. We discuss the likelihood of wind-formed accretion discs around the accretors in each case and confront our model to three persistent Supergiant X-ray Binaries (Vela X-1, IGR J18027-2016, XTE J1855-026).

  20. BROAD BALMER WINGS IN BA HYPER/SUPERGIANTS DISTORTED BY DIFFUSE INTERSTELLAR BANDS: FIVE EXAMPLES IN THE 30 DORADUS REGION FROM THE VLT-FLAMES TARANTULA SURVEY

    SciTech Connect

    Walborn, Nolan R.; Sana, Hugues; Sabbi, Elena E-mail: hsana@stsci.edu; and others

    2015-08-10

    Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them.

  1. HST Studies of the Chromospheres, Wind, and Mass-Loss Rates of Cool Giant and Supergiant Stars

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.

    2000-01-01

    UV spectra of K-M giant and supergiant stars and of carbon stars have been acquired with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). These spectra have been used to measure chromospheric flow and turbulent velocities, study the acceleration of their stellar winds, acquire constraints on their outer atmospheric structure, and enable estimates of their mass-loss rates. Results from our observations of the giant stars Gamma Dra (K5 III hybrid), Alpha Tau (K5 III), Gamma Cru (M3.4 III), Mu Gem (M3 IIIab), and 30 Her (MG III), the supergiants Alpha Ori (M2 Iab) and Lambda Vel (K5 Ib), and the carbon stars TX Psc (NO; C6,2) and TW Hor (NO; C7,2) will be summarized and compared. The high resolution and wavelength accuracy of these data have allowed the direct measurement of the acceleration of the stellar winds in the chromospheres of several of these stars (from initial velocities of 3-9 km/s to upper velocities of 15-25 km/s) and of the chromospheric macroturbulence (-25-35 km/s). The high signal-to-noise and large dynamic range of these spectra have allowed the detection and identification of numerous new emission features, including weak C IV emission indicative of hot transition-region plasma in the non-coronal giant Alpha Tau, many new fluorescent lines of Fe II, and the first detection of fluorescent molecular hydrogen emission and of Ca II recombination lines in the UV spectrum of a giant star. The UV spectrum of two carbon stars have been studied with unprecedented resolution and reveal extraordinarily complicated Mg II lines nearly smothered by circumstellar absorptions. Finally, comparison of synthetic UV emission line profiles computed with the Lamers et al. (1987) Sobolev with Exact Integration (SEI) code with observations of chromospheric emission lines overlain with wind absorption features provides estimates of the mass-loss rates for four of these stars.

  2. Evidence for the pulsational origin of the Long Secondary Periods: The red supergiant star V424 Lac (HD 216946)

    NASA Astrophysics Data System (ADS)

    Messina, Sergio

    2007-10-01

    The results of a long-term UBV photometric monitoring of the red supergiant (RSG) star V424 Lac are presented. V424 Lac shows multiperiodic brightness variations which can be attributed to pulsational oscillations. A much longer period ( P = 1601 d), that allows us to classify this star as a long secondary period variable star (LSPV) has been also detected. The B - V and U - B color variations related to the long secondary period (LSP) are similar to those related to the shorter periods, supporting the pulsational nature of LSP. The long period brightness variation of V424 Lac is accompanied by a near-UV (NUV) excess, which was spectroscopically detected in a previous study [Massey, P., Plez, B., Levesque, E.M., et al., 2005. ApJ 634, 1286] and which is now found to be variable from photometry. On the basis of the results found for V424 Lac, the NUV excess recently found in a number of RSGs may be due not solely to circumstellar dust but may also have a contribution from a still undetected LSP variability.

  3. CHARA/MIRC observations of two M supergiants in Perseus OB1: Temperature, bayesian modeling, and compressed sensing imaging

    SciTech Connect

    Baron, F.; Monnier, J. D.; Anderson, M.; Aarnio, A.; Kiss, L. L.; Neilson, H. R.; Zhao, M.; Pedretti, E.; Thureau, N.; Ten Brummelaar, T. A.; Sturmann, J.; Sturmann, L.; Turner, N.; Ridgway, S. T.; McAlister, H. A.

    2014-04-10

    Two red supergiants (RSGs) of the Per OB1 association, RS Per and T Per, have been observed in the H band using the Michigan Infra-Red Combiner (MIRC) instrument at the CHARA array. The data show clear evidence of a departure from circular symmetry. We present here new techniques specially developed to analyze such cases, based on state-of-the-art statistical frameworks. The stellar surfaces are first modeled as limb-darkened disks based on SATLAS models that fit both MIRC interferometric data and publicly available spectrophotometric data. Bayesian model selection is then used to determine the most probable number of spots. The effective surface temperatures are also determined and give further support to the recently derived hotter temperature scales of RSGs. The stellar surfaces are reconstructed by our model-independent imaging code SQUEEZE, making use of its novel regularizer based on Compressed Sensing theory. We find excellent agreement between the model-selection results and the reconstructions. Our results provide evidence for the presence of near-infrared spots representing about 3%-5% of the stellar flux.

  4. RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES: NLTE EFFECTS IN J-BAND IRON AND TITANIUM LINES

    SciTech Connect

    Bergemann, Maria; Kudritzki, Rolf-Peter; Lind, Karin; Plez, Bertrand; Davies, Ben; Gazak, Zach E-mail: klind@mpa-garching.mpg.de E-mail: zgazak@ifa.hawaii.edu E-mail: bdavies@ast.cam.ac.uk

    2012-06-01

    Detailed non-LTE (NLTE) calculations for red supergiant (RSG) stars are presented to investigate the influence of NLTE on the formation of atomic iron and titanium lines in the J band. With their enormous brightness at J band RSG stars are ideal probes of cosmic abundances. Recent LTE studies have found that metallicities accurate to 0.15 dex can be determined from medium-resolution spectroscopy of individual RSGs in galaxies as distant as 10 Mpc. The NLTE results obtained in this investigation support these findings. NLTE abundance corrections for iron are smaller than 0.05 dex for effective temperatures between 3400 K and 4200 K and 0.1 dex at 4400 K. For titanium the NLTE abundance corrections vary smoothly between -0.4 dex and +0.2 dex as a function of effective temperature. For both elements, the corrections also depend on stellar gravity and metallicity. The physical reasons behind the NLTE corrections and the consequences for extragalactic J-band abundance studies are discussed.

  5. The vast population of Wolf-Rayet and red supergiant stars in M101. I. Motivation and first results

    SciTech Connect

    Shara, Michael M.; Bibby, Joanne L.; Zurek, David; Crowther, Paul A.; Moffat, Anthony F. J.; Drissen, Laurent

    2013-12-01

    Assembling a catalog of at least 10,000 Wolf-Rayet (W-R) stars is an essential step in proving (or disproving) that these stars are the progenitors of Type Ib and Type Ic supernovae. To this end, we have used the Hubble Space Telescope (HST) to carry out a deep, He II optical narrowband imaging survey of the ScI spiral galaxy M101. Almost the entire galaxy was imaged with the unprecedented depth and resolution that only the HST affords. Differenced with archival broadband images, the narrowband images allow us to detect much of the W-R star population of M101. We describe the extent of the survey and our images, as well as our data reduction procedures. A detailed broadband-narrowband imaging study of a field east of the center of M101, containing the giant star-forming region NGC 5462, demonstrates our completeness limits, how we find W-R candidates, their properties and spatial distribution, and how we rule out most contaminants. We use the broadband images to locate luminous red supergiant (RSG) candidates. The spatial distributions of the W-R and RSG stars near NGC 5462 are strikingly different. W-R stars dominate the complex core, while RSGs dominate the complex halo. Future papers in this series will describe and catalog more than a thousand W-R and RSG candidates that are detectable in our images, as well as spectra of many of those candidates.

  6. MASER OBSERVATIONS OF WESTERLUND 1 AND COMPREHENSIVE CONSIDERATIONS ON MASER PROPERTIES OF RED SUPERGIANTS ASSOCIATED WITH MASSIVE CLUSTERS

    SciTech Connect

    Fok, Thomas K. T.; Nakashima, Jun-ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji

    2012-11-20

    We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v = 1, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines are detected toward two of four known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F {sub 21}/F {sub 12}) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in six massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H{sub 2}O line tend to distribute in a region with large L values.

  7. Spitzer-IRS Spectroscopic Studies of Oxygen-Rich Asymptotic Giant Branch Star and Red Supergiant Star Dust Properties

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, Sundar; Speck, Angela; Volk, Kevin; Kemper, Ciska; Reach, William T.; Lagadec, Eric; Bernard, Jean-Philippe; McDonald, Iain; Meixner, Margaret

    2015-01-01

    We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of Oxygen-rich (O-rich) asymptotic giant branch (AGB) and red supergiant (RSG) stars. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper) and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We present an update of our investigation of differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

  8. Comparative Studies of the Dust around Red Supergiant and Oxygen-Rich Asymptotic Giant Branch Stars in the Local Universe

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin; Srinivasan, Sundar; Speck, Angela K.; Volk, Kevin; Kemper, Ciska; Reach, William; Lagadec, Eric; Bernard, Jean-Philippe; McDonald, Iain; Meixner, Margaret; Sloan, Greg; Jones, Olivia

    2015-08-01

    We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 μm emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

  9. Comparative Studies of the Dust around Red Supergiant and Oxygen-Rich Asymptotic Giant Branch Stars in the Local Universe

    NASA Astrophysics Data System (ADS)

    Sargent, B. A.; Srinivasan, S.; Speck, A.; Volk, K.; Kemper, F.; Reach, W.; Lagadec, E.; Bernard, J.-P.; McDonald, I.; Meixner, M.; Sloan, G. C.; Jones, O.

    We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

  10. Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769

    NASA Astrophysics Data System (ADS)

    Aerts, C.; Simón-Díaz, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; Pápics, P. I.; Degroote, P.; Bloemen, S.; Østensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.

    2013-09-01

    Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO

  11. Sharpest views of Betelgeuse reveal how supergiant stars lose mass-Unveiling the true face of a behemoth

    NASA Astrophysics Data System (ADS)

    2009-07-01

    Using different state-of-the-art techniques on ESO's Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. Betelgeuse - the second brightest star in the constellation of Orion (the Hunter) - is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun [1]. It is also one of the most luminous stars known, emitting more light than 100000 Suns. Such extreme properties foretell the demise of a short-lived stellar king. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight. Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material - about the mass of the Sun - in only 10 000 years. Two teams of astronomers have used ESO's Very Large Telescope (VLT) and the most advanced technologies to take a closer look at the gigantic star. Their combined work suggests that an answer to the long-open mass-loss question may well be at hand. The first team used the adaptive optics instrument, NACO, combined with a so-called "lucky imaging" technique, to obtain the sharpest ever image of Betelgeuse, even with Earth's turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be. The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution is as fine as 37 milliarcseconds, which is roughly

  12. Blue supergiant model for ultra-long gamma-ray burst with superluminous-supernova-like bump

    SciTech Connect

    Nakauchi, Daisuke; Nakamura, Takashi; Kashiyama, Kazumi; Suwa, Yudai

    2013-11-20

    Long gamma-ray bursts (LGRBs) have a typical duration of ∼30 s, and some of them are associated with hypernovae, such as Type Ic SN 1998bw. Wolf-Rayet stars are the most plausible LGRB progenitors, since the free fall time of the envelope is consistent with the duration, and the natural outcome of the progenitor is a Type Ic SN. While a new population of ultra-long GRBs (ULGRBs), GRB 111209A, GRB 101225A, and GRB 121027A, has a duration of ∼10{sup 4} s, two of them are accompanied by superluminous-supernova-like (SLSN-like) bumps, which are ≲ 10 times brighter than typical hypernovae. Wolf-Rayet progenitors cannot explain ULGRBs because of durations that are too long and SN-like bumps that are too bright. A blue supergiant (BSG) progenitor model, however, can explain the duration of ULGRBs. Moreover, SLSN-like bumps can be attributed to the so-called cocoon fireball photospheric emissions (CFPEs). Since a large cocoon is inevitably produced during the relativistic jet piercing though the BSG envelope, this component can be smoking gun evidence of the BSG model for ULGRBs. In this paper, we examine u-, g-, r-, i-, and J-band light curves of three ULGRBs and demonstrate that they can be fitted quite well by our BSG model with the appropriate choices of the jet opening angle and the number density of the ambient gas. In addition, we predict that for 121027A, SLSN-like bump could have been observed for ∼20-80 days after the burst. We also propose that some SLSNe might be CFPEs of off-axis ULGRBs without visible prompt emissions.

  13. The Orbit and Properties of the BD+60 73 + IGRJ00370+612 Supergiant X-Ray Binary

    NASA Astrophysics Data System (ADS)

    Bolton, C. T.; Grunhut, J. H.

    2007-08-01

    Spectrograms of the blue and H alpha regions of BD+60 73 obtained with the Cassegrain spectrograph on the David Dunlap Observatory 1.88 m telescope have been measured for radial velocities. These measures confirm that BD+60 73 is a single-line spectroscopic binary with the same period, 15.665 d, as the x-ray flux variations of IGRJ00370+612. The x-ray maxima occur at or just after the time of periastron passage, even though the eccentricity e=0.37 does not seem large enough to produce a large increase in the mass flux at the position of the compact object at the time of periastron passage. The mass function combined with a plausible range of possible masses for a neutron star companion yields primary masses within the range expected for the spectral type of BD+60 73. The compact companion cannot be a black hole unless the supergiant has an exceptionally high mass for its B1Ib spectral type or the inclination of the orbit is very low. The H alpha line shows weak, variable emission, but we have insufficient data to test whether these variations are correlated with orbital phase. We note, as have other authors, that BD+60_73 is projected on the sky within the bounds of Cas OB5. It also lies close to the "adolescent" supernova remnant CTB1. However, the binary system has a radial velocity of approximately -40 km/s with respect to Cas OB5.

  14. Luminous and variable stars in M31 and M33. II. Luminous blue variables, candidate LBVs, Fe II emission line stars, and other supergiants

    SciTech Connect

    Humphreys, Roberta M.; Davidson, Kris; Weis, Kerstin; Bomans, D. J.; Burggraf, Birgitta E-mail: kweis@astro.rub.de

    2014-07-20

    An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor class, including the most luminous evolved stars, the luminous blue variables (LBVs), and the warm and cool hypergiants is now needed for a complete picture of the final pre-supernova stages of very massive stars. We have begun a survey of the evolved and unstable luminous star populations in several nearby resolved galaxies. In this second paper on M31 and M33, we review the spectral characteristics, spectral energy distributions, circumstellar ejecta, and evidence for mass loss for 82 luminous and variable stars. We show that many of these stars have warm circumstellar dust including several of the Fe II emission line stars, but conclude that the confirmed LBVs in M31 and M33 do not. The confirmed LBVs have relatively low wind speeds even in their hot, quiescent or visual minimum state compared to the B-type supergiants and Of/WN stars which they spectroscopically resemble. The nature of the Fe II emission line stars and their relation to the LBV state remains uncertain, but some have properties in common with the warm hypergiants and the sgB[e] stars. Several individual stars are discussed in detail. We identify three possible candidate LBVs and three additional post-red supergiant candidates. We suggest that M33-013406.63 (UIT301,B416) is not an LBV/S Dor variable, but is a very luminous late O-type supergiant and one of the most luminous stars or pair of stars in M33.

  15. HD 74194, a new binary supergiant fast X-ray transient?, possible optical counterpart of INTEGRAL hard X-ray source IGR J08408-4503

    NASA Astrophysics Data System (ADS)

    Barba, Rodolfo; Gamen, Roberto; Morrell, Nidia

    2006-05-01

    HD 74194 is an O-type supergiant, classified as O8.5 Ib (f) (Walborn 1973, AJ 78, 1067), also suspected as single-lined binary (see Maiz Apellaniz et al. 2004, ApJS 151, 103). This star is being spectroscopically monitored as part of our program of study of massive binaries. We have obtained high-resolution spectra of HD 74194 with the Echelle spectrograph attached to the du Pont 2.5-m telescope at Las Campanas Observatory in 2006 May 18.00, 20.96, 22.00, and 22.97.

  16. A Suzaku X-ray Observation of One Orbit of the Supergiant Fast X-ray Transient IGR J16479-4514

    NASA Technical Reports Server (NTRS)

    Sidoli, L.; Esposito, P.; Sguera, V.; Bodaghee, A.; Tomsick, J. A.; Pottschmidt, K.; Rodriguez, J.; Ramano, P.; Wilms, J.

    2013-01-01

    We report on a 250 ks long X-ray observation of the supergiant fast X-ray transient (SFXT) IGR J16479-4514 performed with Suzaku in 2012 February. During this observation, about 80% of the short orbital period (P(sub orb) approximates 3.32 days) was covered as continuously as possible for the first time. The source light curve displays variability of more than two orders of magnitude, starting with a very low emission state (10(exp -13) erg / sq cm/s; 1-10 keV) lasting the first 46 ks, consistent with being due to the X-ray eclipse by the supergiant companion. The transition to the uneclipsed X-ray emission is energy dependent. Outside the eclipse, the source spends most of the time at a level of 6-7X10)(exp-12) erg/sq. cm/s) punctuated by two structured faint flares with a duration of about 10 and 15 ks, respectively, reaching a peak flux of 3-4X10(exp -11) erg/sq. cm./S, separated by about 0.2 in orbital phase. Remarkably, the first faint flare occurs at a similar orbital phase of the bright flares previously observed in the system. This indicates the presence of a phase-locked large scale structure in the supergiant wind, driving a higher accretion rate onto the compact object. The average X-ray spectrum is hard and highly absorbed, with a column density, NH, of 10*exp 23)/sq cm, clearly in excess of the interstellar absorption. There is no evidence for variability of the absorbing column density, except that during the eclipse, where a less absorbed X-ray spectrum is observed. A narrow Fe K-alpha emission line at 6.4 keV is viewed along the whole orbit, with an intensity which correlates with the continuum emission above 7 keV. The scattered component visible during the X-ray eclipse allowed us to directly probe the wind density at the orbital separation, resulting in rho(sub w)=7X10(exp -14) g/cubic cm. Assuming a spherical geometry for the supergiant wind, the derived wind density translates into a ratio M(sub w)/v(sub infinity) = 7X10(exp -17) Solar M

  17. VLTI/AMBER spectro-interferometry of the late-type supergiants V766 Cen (=HR 5171 A), σ Oph, BM Sco, and HD 206859

    NASA Astrophysics Data System (ADS)

    Wittkowski, M.; Arroyo-Torres, B.; Marcaide, J. M.; Abellan, F. J.; Chiavassa, A.; Guirado, J. C.

    2017-01-01

    Aims: We add four warmer late-type supergiants to our previous spectro-interferometric studies of red giants and supergiants. Methods: We measure the near-continuum angular diameter, derive fundamental parameters, discuss the evolutionary stage, and study extended atmospheric atomic and molecular layers. Results: V766 Cen (=HR 5171 A) is found to be a high-luminosity (log L/L⊙ = 5.8 ± 0.4) source of effective temperature 4290 ± 760 K and radius 1490 ± 540 R⊙, located in the Hertzsprung-Russell (HR) diagram close to both the Hayashi limit and Eddington limit; this source is consistent with a 40 M⊙ evolutionary track without rotation and current mass 27-36 M⊙. V766 Cen exhibits Na i in emission arising from a shell of radius 1.5 RPhot and a photocenter displacement of about 0.1 RPhot. It shows strong extended molecular (CO) layers and a dusty circumstellar background component. The other three sources are found to have lower luminosities of about log L/L⊙ = 3.4-3.5, corresponding to 5-9 M⊙ evolutionary tracks. They cover effective temperatures of 3900 K to 5300 K and radii of 60-120 R⊙. They do not show extended molecular layers as observed for higher luminosity RSGs of our sample. BM Sco shows an unusually strong contribution by an over-resolved circumstellar dust component. Conclusions: V766 Cen is a red supergiant located close to the Hayashi limit instead of a yellow hypergiant already evolving back toward warmer effective temperatures as discussed in the literature. Our observations of the Na i line and the extended molecular layers suggest an optically thick pseudo-photosphere at about 1.5 RPhot at the onset of the wind. The stars σ Oph, BM Sco, and HD 206859 are more likely high-mass red giants instead of RSGs as implied by their luminosity class Ib. This leaves us with an unsampled locus in the HR diagram corresponding to luminosities log L/L⊙ 3.8-4.8 or masses 10-13 M⊙, possibly corresponding to the mass region where stars explode as

  18. IGR J17544-2619 IN DEPTH WITH SUZAKU: DIRECT EVIDENCE FOR CLUMPY WINDS IN A SUPERGIANT FAST X-RAY TRANSIENT

    SciTech Connect

    Rampy, Rachel A.; Smith, David M.; Negueruela, Ignacio

    2009-12-10

    We present direct evidence for dense clumps of matter in the companion wind in a Supergiant Fast X-ray Transient (SFXT) binary. This is seen as a brief period of enhanced absorption during one of the bright, fast flares that distinguish these systems. The object under study was IGR J17544-2619, and a total of 236 ks of data were accumulated with the Japanese satellite Suzaku. The activity in this period spans a dynamic range of almost 10{sup 4} in luminosity and gives a detailed look at SFXT behavior.

  19. Discovery and Characterization of Luminous Blue Variables, Wolf-Rayet Stars, and Massive Supergiants and Their Shells Using Spitzer, WISE, and Herschel Data

    NASA Astrophysics Data System (ADS)

    Stringfellow, Guy

    The extensive WISE all-sky 12 and 22 micron survey data, the Herschel PACS and SPIRE imaging archive (including the GTO and OT Key Programs), as well as the Spitzer IRAC 8 and MIPS 24 micron imaging archival data (GO, GTO, and Legacy Surveys) are being mined for the discovery of new shell and ring-nebulae. Combined with 2MASS data, the progenitor stars are also being identified, and optical and near-IR spectroscopy obtained to confirm their spectral types. Origin of the nebulae arise from a variety of progenitors that include very massive stars, with the vast majority not having been previously identified. Representative classes for the progenitor stars are Luminous Blue Variables (LBVs), Wolf-Rayet (WR), B[e], OB, and Supergiant stars. The discovery potential for these rare massive evolved stars from the mid-IR imaging archives is greater than any other technique utilized over the past several decades, including extensive broadband infrared photometry-color determinations (Hadfield et al. 2007), and near-IR narrowband methods (Shara et al. 2009). The statistics being provided on this new, previously hidden population of evolved stars may very well enable evolutionary pathways to be better delineated, thereby identifying the physics operating in these extreme stars. The data being collected will more tightly define the evolutionary models that apply to these stars, and that enter into modeling and interpretation of extragalactic massive star formation regions (starbursts). Multi-wavelength color-color maps wil be constructed and used to analyze the dust distribution, the energetics of the nebulae and its interaction with the ISM, and identification of nearby star formation perhaps being triggered by the massive stars and the nebulae they produce. As demonstrated in a recent publication presenting the discovery and analysis of two new candidate LBVs found in the early WISE data release (Gvaramadze et al. 2012), much discovery potential yet resides within the

  20. GALEX AND PAN-STARRS1 DISCOVERY OF SN IIP 2010aq: THE FIRST FEW DAYS AFTER SHOCK BREAKOUT IN A RED SUPERGIANT STAR

    SciTech Connect

    Gezari, S.; Huber, M. E.; Grav, T.; Rest, A.; Narayan, G.; Forster, K.; Neill, J. D.; Martin, D. C.; Valenti, S.; Smartt, S. J.; Chornock, R.; Berger, E.; Soderberg, A. M.; Mattila, S.; Kankare, E.; Burgett, W. S.; Chambers, K. C.; Dombeck, T.; Heasley, J. N.; Hodapp, K. W.

    2010-09-01

    We present the early UV and optical light curve of Type IIP supernova (SN) 2010aq at z = 0.0862, and compare it to analytical models for thermal emission following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring between the Galaxy Evolution Explorer (GALEX) Time Domain Survey (TDS) in the NUV and the Pan-STARRS1 Medium Deep Survey (PS1 MDS) in the g, r, i, and z bands. The GALEX and Pan-STARRS1 observations detect the SN less than 1 day after the shock breakout, measure a diluted blackbody temperature of 31, 000 {+-} 6000 K 1 day later, and follow the rise in the UV/optical light curve over the next 2 days caused by the expansion and cooling of the SN ejecta. The high signal-to-noise ratio of the simultaneous UV and optical photometry allows us to fit for a progenitor star radius of 700 {+-} 200R {sub sun}, the size of a red supergiant star. An excess in UV emission two weeks after shock breakout compared with SNe well fitted by model atmosphere-code synthetic spectra with solar metallicity is best explained by suppressed line blanketing due to a lower metallicity progenitor star in SN 2010aq. Continued monitoring of PS1 MDS fields by the GALEX TDS will increase the sample of early UV detections of Type II SNe by an order of magnitude and probe the diversity of SN progenitor star properties.

  1. Are Ultra-long Gamma-Ray Bursts Caused by Blue Supergiant Collapsars, Newborn Magnetars, or White Dwarf Tidal Disruption Events?

    NASA Astrophysics Data System (ADS)

    Ioka, Kunihito; Hotokezaka, Kenta; Piran, Tsvi

    2016-12-01

    Ultra-long gamma-ray bursts (ulGRBs) are a new population of GRBs with extreme durations of ∼104 s. Leading candidates for their origin are blue supergiant collapsars, magnetars, and white dwarf tidal disruption events (WD-TDEs) caused by massive black holes (BHs). Recent observations of supernova-like (SN-like) bumps associated with ulGRBs challenged both the WD-TDE and the blue supergiant models because of the detection of SNe and the absence of hydrogen lines, respectively. We propose that WD-TDEs can accommodate the observed SN-like bumps if the fallback WD matter releases energy into the unbound WD ejecta. The observed ejecta energy, luminosity, and velocity are explained by the gravitational energy, Eddington luminosity, and escape velocity of the formed accretion disk, respectively. We also show that the observed X-rays can ionize the ejecta, eliminating lines. The SN-like light curves (SN 2011kl) for the ulGRB 111209A are consistent with all three models, although a magnetar model is unnatural because the spin-down time required to power the SN-like bump is a hundred times longer than the GRB. Our results imply that TDEs are a possible energy source for SN-like events in general and for ulGRBs in particular.

  2. Wind Variability of B Supergiants. No. 1; The Rapid Rotator HD 64760 (B0.5 Ib)

    NASA Technical Reports Server (NTRS)

    Massa, Derck; Prinja, Raman K.; Fullerton, Alexander W.

    1995-01-01

    We present the results of a 6 day time series of observations of the rapidly rotating B0.5 Ib star HD 64760. We point out several reasons why such intermediate luminosity B supergiants are ideal targets for wind variability studies and then present our results that show the following: continuous wind activity throughout the 6 day run with the wind never in steady state for more than a few hr; wind variability very near nu = 0 km sec(exp -1) in the resonance lines from the lower ionization stages (Al III and C II); a distinct correlation between variability in the Si III ; lambda(lambda)1300 triplets, the strong C III (lambda)1247 singlet, and the onset of extremely strong wind activity, suggesting a connection between photospheric and wind activity; long temporal coherence in the behavior of the strong absorption events; evidence for large-scale spatial coherence, implied by a whole scale, simultaneous weakening in the wind absorption over a wide range in velocities; and ionization variability in the wind accompanying the largest changes in the absorption strengths of the wind lines. In addition, modeling of the wind lines provides the following information about the state the wind in HD 64760. The number of structures on the portion of a constant velocity surface occulting the stellar disk at a particular time must be quite small, while the number on the entire constant velocity surface throughout the wind must be large. The escape probability at low velocity is overestimated by a normal beta approx. 1 velocity law, perhaps due to the presence of low-velocity shocks deep in the wind or a shallow velocity gradient at low velocity. Estimates of the ionization structure in the wind indicate that the ionization ratios are not those expected from thermal equilibrium wind models or from an extrapolation of previous O star results. The large observed q(N V)/q(Si IV) ratio is almost certainly due to distributed X-rays, but the level of ionization predicted by distributed

  3. Photometry of the Variable Bright Red Supergiant Betelgeuse from the Ground and from Space with the BRITE Nano-satellites

    NASA Astrophysics Data System (ADS)

    Minor, Robert; Guinan, Edward F.

    2016-01-01

    Robert B. Minor, Edward Guinan, Richard Wasatonic Betelgeuse (Alpha Orionis) is a large, luminous semi-regular red supergiant of spectral class M1.5-2Iab. It is the 8th brightest star in the night sky. Betelgeuse is 30,000 times more luminous than the Sun and 700 times larger. It has an estimated age of ~8 +/- 2 Myr. Betelgeuse explode in a Type II supernova (anytime within the next million years). When it explodes, it will shine with about the intensity of a full moon and may be visible during the day. However, it is too far away to cause any major damage to Earth. Photometry of this pre-supernova star has been ongoing at Villanova for nearly 45 years. These observations are being used to define the complex brightness variations of this star. Semi-regular periodic light variations have been found with periods of 385 days up to many years. These light variations are used to study its unstable atmosphere and resulting complex pulsations. Over the last 15 years, it has been observed by Wasatonic who has accumulated a large photometric database. The ground-based observations are limited to precisions of 1.5%, and due to poor weather, limit observations to about 1-2 times per week. However, with the recent successful launch of the BRITE Nano-satellites (http://www.brite-constellation.at) during 2013-14, it is possible to secure high precision photometry of bright stars, including Betelgeuse, continuously for up to 3 months. Villanova has participated in the BRITE guest investigators program and has been awarded observing time and data rights many bright stars, including Betelgeuse. BRITE blue and red observations of Betelgeuse were carried out during the Nov-Feb 2013-14 season and the 2014-15. These datasets were given to Villanova and have been combined with coexistent photometry from Wasatonic. Although BRITE's red data is saturated, the blue data is useable. The BRITE datasets were combined with our ground-based V, red, and near-IR photometry. Problems were

  4. DISTANCE AND PROPER MOTION MEASUREMENT OF THE RED SUPERGIANT, PZ CAS, IN VERY LONG BASELINE INTERFEROMETRY H{sub 2}O MASER ASTROMETRY

    SciTech Connect

    Kusuno, K.; Asaki, Y.; Imai, H.; Oyama, T. E-mail: asaki@vsop.isas.jaxa.jp E-mail: t.oyama@nao.ac.jp

    2013-09-10

    We present the very long baseline interferometry H{sub 2}O maser monitoring observations of the red supergiant, PZ Cas, at 12 epochs from 2006 April to 2008 May. We fitted maser motions to a simple model composed of a common annual parallax and linear motions of the individual masers. The maser motions with the parallax subtracted were well modeled by a combination of a common stellar proper motion and a radial expansion motion of the circumstellar envelope. We obtained an annual parallax of 0.356 {+-} 0.026 mas and a stellar proper motion of {mu}{sub {alpha}}{sup *} cos {delta} = -3.7 {+-} 0.2 and {mu}{sup *}{sub {delta}}=-2.0{+-}0.3 mas yr{sup -1} eastward and northward, respectively. The annual parallax corresponds to a trigonometric parallax of 2.81{sup +0.22}{sub -0.19} kpc. By rescaling the luminosity of PZ Cas in any previous studies using our trigonometric parallax, we estimated the location of PZ Cas on a Hertzsprung-Russell diagram and found that it approaches a theoretically evolutionary track around an initial mass of {approx}25 M{sub Sun }. The sky position and the distance to PZ Cas are consistent with the OB association, Cas OB5, which is located in a molecular gas super shell. The proper motion of PZ Cas is close to that of the OB stars and other red supergiants in Cas OB5 measured by the Hipparcos satellite. We derived the peculiar motion of PZ Cas of U{sub s} = 22.8 {+-} 1.5, V{sub s} = 7.1 {+-} 4.4, and W{sub s} = -5.7 {+-} 4.4 km s{sup -1}. This peculiar motion has rather a large U{sub s} component, unlike those of near high-mass star-forming regions with negatively large V{sub s} motions. The uniform proper motions of the Cas OB5 member stars suggest random motions of giant molecular clouds moving into local potential minima in a time-dependent spiral arm, rather than a velocity field caused by the spiral arm density wave.

  5. Obama Finding Teacher Support Secure, If Tepid: Policy Rifts Complicate Obama-Teacher Dance

    ERIC Educational Resources Information Center

    Klein, Alyson

    2012-01-01

    Ask Antonio White what he thinks of Race to the Top--President Barack Obama's signature K-12 initiative--and the Florida teacher will tell you the competitive-grant program is a "difficult pill to swallow." Merit pay for teachers based partly on student test scores is "a joke," he says. He's also not a fan of expanding charter…

  6. RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 {mu}m CO EMISSION AROUND VY CMa AND BETELGEUSE

    SciTech Connect

    Smith, Nathan; Hinkle, Kenneth H.; Ryde, Nils E-mail: hinkle@noao.edu

    2009-03-15

    We present high-resolution 4.6 {mu}m CO spectra of the circumstellar environments of two red supergiants (RSGs) that are potential supernova (SN) progenitors: Betelgeuse and VY Canis Majoris (VY CMa). Around Betelgeuse, {sup 12}CO emission within {+-}3'' ({+-}12 km s{sup -1}) follows a mildly clumpy but otherwise spherical shell, smaller than its {approx}55'' shell in K I {lambda}7699. In stark contrast, 4.6 {mu}m CO emission around VY CMa is coincident with bright K I in its clumpy asymmetric reflection nebula, within {+-}5'' ({+-}40 km s{sup -1}) of the star. Our CO data reveal redshifted features not seen in K I spectra of VY CMa, indicating a more isotropic distribution of gas punctuated by randomly distributed asymmetric clumps. The relative CO and K I distribution in Betelgeuse arises from ionization effects within a steady wind, whereas in VY CMa, K I is emitted from skins of CO cloudlets resulting from episodic mass ejections 500-1000 yr ago. In both cases, CO and K I trace potential pre-SN circumstellar matter: we conclude that an extreme RSG like VY CMa might produce a Type IIn event like SN 1988Z if it were to explode in its current state, but Betelgeuse will not. VY CMa demonstrates that luminous blue variables are not necessarily the only progenitors of SNe IIn, but it underscores the requirement that SNe IIn suffer enhanced episodic mass loss shortly before exploding.

  7. The emission-line regions in the nucleus of NGC 1313 probed with GMOS-IFU: a supergiant/hypergiant candidate and a kinematically cold nucleus

    NASA Astrophysics Data System (ADS)

    Menezes, R. B.; Steiner, J. E.

    2017-04-01

    NGC 1313 is a bulgeless nearby galaxy, classified as SB(s)d. Its proximity allows high spatial resolution observations. We performed the first detailed analysis of the emission-line properties in the nuclear region of NGC 1313, using an optical data cube obtained with the Gemini Multi-object Spectrograph. We detected four main emitting areas, three of them (regions 1, 2 and 3) having spectra typical of H II regions. Region 1 is located very close to the stellar nucleus and shows broad spectral features characteristic of Wolf-Rayet stars. Our analysis revealed the presence of one or two WC4-5 stars in this region, which is compatible with results obtained by previous studies. Region 4 shows spectral features (as a strong Hα emission line, with a broad component) typical of a massive emission-line star, such as a luminous blue variable, a B[e] supergiant or a B hypergiant. The radial velocity map of the ionized gas shows a pattern consistent with rotation. A significant drop in the values of the gas velocity dispersion was detected very close to region 1, which suggests that the young stars there were formed from this cold gas, possibly keeping low values of velocity dispersion. Therefore, although detailed measurements of the stellar kinematics were not possible (due to the weak stellar absorption spectrum of this galaxy), we predict that NGC 1313 may also show a drop in the values of the stellar velocity dispersion in its nuclear region.

  8. DUST PRODUCTION FACTORIES IN THE EARLY UNIVERSE: FORMATION OF CARBON GRAINS IN RED-SUPERGIANT WINDS OF VERY MASSIVE POPULATION III STARS

    SciTech Connect

    Nozawa, Takaya; Yoon, Sung-Chul; Maeda, Keiichi; Kozasa, Takashi; Nomoto, Ken'ichi; Langer, Norbert

    2014-06-01

    We investigate the formation of dust in a stellar wind during the red-supergiant (RSG) phase of a very massive Population III star with a zero-age main sequence mass of 500 M {sub ☉}. We show that, in a carbon-rich wind with a constant velocity, carbon grains can form with a lognormal-like size distribution, and that all of the carbon available for dust formation finally condenses into dust for wide ranges of the mass-loss rate ((0.1-3) × 10{sup –3} M {sub ☉} yr{sup –1}) and wind velocity (1-100 km s{sup –1}). We also find that the acceleration of the wind, driven by newly formed dust, suppresses the grain growth but still allows more than half of the gas-phase carbon to finally be locked up in dust grains. These results indicate that, at most, 1.7 M {sub ☉} of carbon grains can form during the RSG phase of 500 M {sub ☉} Population III stars. Such a high dust yield could place very massive primordial stars as important sources of dust at the very early epoch of the universe if the initial mass function of Population III stars was top-heavy. We also briefly discuss a new formation scenario of carbon-rich ultra-metal-poor stars, considering feedback from very massive Population III stars.

  9. NuSTAR observations of the supergiant X-ray pulsar IGR J18027-2016: accretion from the stellar wind and possible cyclotron absorption line

    NASA Astrophysics Data System (ADS)

    Lutovinov, Alexander A.; Tsygankov, Sergey S.; Postnov, Konstantin A.; Krivonos, Roman A.; Molkov, Sergey V.; Tomsick, John A.

    2017-04-01

    We report on the first focused hard X-ray view of the absorbed supergiant system IGR J18027-2016 performed with the Nuclear Spectroscopic Telescope Array observatory. The pulsations are clearly detected with a period of Pspin = 139.866(1) s and a pulse fraction of about 50-60 per cent at energies from 3 to 80 keV. The source demonstrates an approximately constant X-ray luminosity on a time-scale of more than dozen years with an average spin-down rate of dot{P}≃ 6× 10^{-10} s s-1. This behaviour of the pulsar can be explained in terms of the wind accretion model in the settling regime. The detailed spectral analysis at energies above 10 keV was performed for the first time and revealed a possible cyclotron absorption feature at energy ∼23 keV. This energy corresponds to the magnetic field B ≃ 3 × 1012 G at the surface of the neutron star, which is typical for X-ray pulsars.

  10. Infrared Space Observatory Observations of Far-Infrared Rotational Emission Lines of Water Vapor Toward the Supergiant Star VY Canis Majoris

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Feuchtgruber, Helmut; Harwit, Martin; Melnick, Gary J.

    1999-01-01

    We report the detection of numerous far-infrared emission lines of water vapor toward the supergiant star VY Canis Majoris. A 29.5-45 micron grating scan of VY CMa, obtained using the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory at a spectral resolving power lambda/delat.lambda of approximately 2000, reveals at least 41 spectral features due to water vapor that together radiate a total luminosity of approximately 25 solar luminosity . In addition to pure rotational transitions within the ground vibrational state, these features include rotational transitions within the (010) excited vibrational state. The spectrum also shows the (sup 2)product(sub 1/2) (J = 5/2) left arrow (sup 2)product(sub 3/2) (J = 3/2) OH feature near 34.6 micron in absorption. Additional SWS observations of VY CMa were carried out in the instrument's Fabry-Perot mode for three water transitions: the 7(sub 25)-6(sub 16) line at 29.8367 micron, the 4(sub 41)-3(sub 12) line at 31.7721 micron, and the 4(sub 32)-3(sub 03) line at 40.6909 micron. The higher spectral resolving power lambda/delta.lambda of approximately 30,000 thereby obtained permits the line profiles to be resolved spectrally for the first time and reveals the "P Cygni" profiles that are characteristic of emission from an outflowing envelope.

  11. Spitzer-IRS Spectroscopic Studies of the Properties of Dust from Oxygen-Rich Asymptotic Giant Branch and Red Supergiant Stars

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Speck, A.; Volk, K.; Kemper, C.; Reach, W. T.; Lagadec, E.; Bernard, J.; McDonald, I.; Meixner, M.; Srinivasan, S.

    2014-01-01

    We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of Oxygen-rich (O-rich) asymptotic giant branch (AGB) and red supergiant (RSG) stars. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper) and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

  12. The XMM-Newton1 and INTEGRAL2 Observations of the Supergiant Fast X-Ray Transient IGR J16328-4726

    NASA Astrophysics Data System (ADS)

    Fiocchi, M.; Bazzano, A.; Natalucci, L.; Ubertini, P.; Sguera, V.; Bird, A. J.; Boon, C. M.; Persi, P.; Piro, L.

    2016-10-01

    The accretion mechanism producing the short flares observed from the Supergiant Fast X-ray Transients (SFXT) is still highly debated and forms a major part in our attempts to place these X-ray binaries in the wider context of the High Mass X-ray Binaries. We report on a 216 ks INTEGRAL observation of the SFXT IGR J16328-4726 (2014 August 24-27) simultaneous with two fixed-time observations with XMM-Newton (33 and 20 ks) performed around the putative periastron passage, in order to investigate the accretion regime and the wind properties during this orbital phase. During these observations, the source has shown luminosity variations, from ˜ 4× {10}34 to ˜ {10}36 {erg} {{{s}}}-1, linked to spectral properties changes. The soft X-ray continuum is well modeled by a power law with a photon index varying from ˜1.2 up to ˜1.7 and with high values of the column density in the range of ˜ 2{--}4× {10}23 {{cm}}-2. We report on the presence of iron lines at ˜6.8-7.1 keV, suggesting that the X-ray flux is produced by the accretion of matter from the companion wind characterized by density and temperature inhomogeneities.

  13. Chemical Emergencies

    MedlinePlus

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  14. Bispectrum speckle interferometry observations and radiative transfer modelling of the red supergiant NML Cyg. Multiple dust-shell structures evidencing previous superwind phases

    NASA Astrophysics Data System (ADS)

    Blöcker, T.; Balega, Y.; Hofmann, K.-H.; Weigelt, G.

    2001-04-01

    NML Cyg is a highly evolved OH/IR supergiant, one of the most prominent infrared objects due to its strong obscuration by dust, and supposed to be among the most luminous supergiants in the galaxy. We present the first diffraction-limited 2.13 mu m observations of NML Cyg with 73 mas resolution. The speckle interferograms were obtained with the 6 m telescope at the Special Astrophysical Observatory, and the image reconstruction is based on the bispectrum speckle-interferometry method. The visibility function declines towards the diffraction limit to ~ 0.6. Radiative transfer calculations have been carried out to model the spectral energy distribution, given by ground-based photometry and ISO spectroscopy, and our 2.13 mu m visibility function. Additionally, mid-infrared visibility functions at 11 mu m were considered. The observed dust shell properties do not appear to be in accordance with standard single-shell (uniform outflow) models but seem to require multiple components. Considering previous periods of enhanced mass-loss, various density enhancements in the dust shell were taken into account. An extensive grid of models was calculated for different locations and strenghts of such superwind regions in the dust shell. To match the observations from the optical to the sub-mm domain requires at least two superwind regions embedded in the shell. The best model includes a dust shell with a temperature of 1000 K at its inner radius of 6.2 R*, a close embedded superwind shell extending from 15.5 R* to 21.7 R* with an amplitude (factor of density enhancement) of 10, and a far-out density enhancement at 186 R* with an amplitude of 5. The angular diameters of the central star and of the inner rim of the dust shell amount to 16.2 mas and 105 mas, resp. The diameter of the embedded close superwind region extends from 263 mas to 368 mas, and the inner boundary of the distant superwind region has a diameter of 3\\farcs 15. In the near-infrared the dust condensation zone is

  15. Long-lasting X-ray emission from type IIb supernova 2011dh and mass-loss history of the yellow supergiant progenitor

    SciTech Connect

    Maeda, Keiichi; Katsuda, Satoru; Bamba, Aya; Terada, Yukikatsu; Fukazawa, Yasushi

    2014-04-20

    Type IIb supernova (SN) 2011dh, with conclusive detection of an unprecedented yellow supergiant (YSG) progenitor, provides an excellent opportunity to deepen our understanding on the massive star evolution in the final centuries toward the SN explosion. In this paper, we report on detection and analyses of thermal X-ray emission from SN IIb 2011dh at ∼500 days after the explosion on Chandra archival data, providing a solidly derived mass-loss rate of a YSG progenitor for the first time. We find that the circumstellar media should be dense, more than that expected from a Wolf-Rayet (W-R) star by one order of magnitude. The emission is powered by a reverse shock penetrating into an outer envelope, fully consistent with the YSG progenitor but not with a W-R progenitor. The density distribution at the outermost ejecta is much steeper than that expected from a compact W-R star, and this finding must be taken into account in modeling the early UV/optical emission from SNe IIb. The derived mass-loss rate is ∼3 × 10{sup –6} M {sub ☉} yr{sup –1} for the mass-loss velocity of ∼20 km s{sup –1} in the final ∼1300 yr before the explosion. The derived mass-loss properties are largely consistent with the standard wind mass-loss expected for a giant star. This is not sufficient to be a main driver to expel nearly all the hydrogen envelope. Therefore, the binary interaction, with a huge mass transfer having taken place at ≳ 1300 yr before the explosion, is a likely scenario to produce the YSG progenitor.

  16. APERTURE SYNTHESIS OBSERVATIONS OF CO, HCN, AND 89 GHz CONTINUUM EMISSION TOWARD NGC 604 IN M33: SEQUENTIAL STAR FORMATION INDUCED BY A SUPERGIANT H II REGION

    SciTech Connect

    Miura, Rie; Okumura, Sachiko K.; Kurono, Yasutaka; Nakanishi, Kouichiro; Tosaki, Tomoka; Tamura, Yoichi; Kuno, Nario; Kawabe, Ryohei; Sakamoto, Seiichi; Hasegawa, Takashi

    2010-12-01

    We present the results from new Nobeyama Millimeter Array observations of CO(1-0), HCN(1-0), and 89 GHz continuum emission toward NGC 604, known as the supergiant H II region in the nearby galaxy M33. Our high spatial resolution images (4.''2 x 2.''6, corresponding to 17 pc x 11 pc physical size) of CO emission allowed us to uncover 10 individual molecular clouds that have masses of (0.8-7.4) x10{sup 5} M{sub sun} and sizes of 5-29 pc, comparable to those of typical Galactic giant molecular clouds. Moreover, we detected for the first time HCN emission in the two most massive clouds and 89 GHz continuum emission at the rims of the 'H{alpha} shells'. The HCN and 89 GHz continuum emission are offset from the CO peak and are distributed in the direction of the central cluster. Three out of ten CO clouds are well correlated with the H{alpha} shells both in spatial and velocity domains, implying an interaction between molecular gas and the expanding H II region. The CO clouds show varieties in star formation efficiencies (SFEs), which are estimated from the 89 GHz emission and combination of H{alpha} and Spitzer 24 {mu}m data. Furthermore, we found that the SFEs decrease with increasing projected distance measured from the heart of the central OB star cluster in NGC 604, suggesting radial changes in the evolutionary stages of the molecular clouds in the course of stellar cluster formation. Our results provide further support to the picture of sequential star formation in NGC 604 initially proposed by Tosaki et al. with the higher spatially resolved molecular clouds, in which an isotropic expansion of the H II region pushes gases outward, which accumulates to form dense molecular clouds, and then induces massive star formations.

  17. The Contribution of Thermally-Pulsing Asymptotic Giant Branch and Red Supergiant Starts to the Luminosities of the Magellanic Clouds at 1-24 micrometers

    NASA Technical Reports Server (NTRS)

    Melbourne, J.; Boyer, Martha L.

    2013-01-01

    We present the near-through mid-infrared flux contribution of thermally-pulsing asymptotic giant branch (TP-AGB) and massive red supergiant (RSG) stars to the luminosities of the Large and Small Magellanic Clouds (LMC and SMC, respectively). Combined, the peak contribution from these cool evolved stars occurs at approx 3 - 4 micron, where they produce 32% of the SMC light, and 25% of the LMC flux. The TP-AGB star contribution also peaks at approx 3 - 4 micron and amounts to 21% in both galaxies. The contribution from RSG stars peaks at shorter wavelengths, 2.2 micron, where they provide 11% of the SMC flux, and 7% for the LMC. Both TP-AGB and RSG stars are short lived, and thus potentially impose a large stochastic scatter on the near-IR derived mass-to-light (M/L) ratios of galaxies at rest-frame 1 - 4 micron. To minimize their impact on stellar mass estimates, one can use the M/L ratio at shorter wavelengths (e.g., at 0.8 - 1 micron). At longer wavelengths (much > 8 micron), emission from dust in the interstellar medium dominates the flux. In the LMC, which shows strong polycyclic aromatic hydrocarbon (PAH) emission at 8 micron, TP-AGB and RSG contribute less than 4% of the 8 micron flux. However, 19% of the SMC 8 micron flux is from evolved stars, nearly half of which is produced by the rarest, dustiest, carbon-rich TP-AGB stars. Thus, star formation rates of galaxies, based on an 8 micron flux (e.g., observed-frame 24 micron at z = 2), may be biased modestly high, especially for galaxies with little PAH emission.

  18. THE CONTRIBUTION OF THERMALLY-PULSING ASYMPTOTIC GIANT BRANCH AND RED SUPERGIANT STARS TO THE LUMINOSITIES OF THE MAGELLANIC CLOUDS AT 1-24 {mu}m

    SciTech Connect

    Melbourne, J.; Boyer, Martha L. E-mail: martha.l.boyer@nasa.gov

    2013-02-10

    We present the near-through mid-infrared flux contribution of thermally-pulsing asymptotic giant branch (TP-AGB) and massive red supergiant (RSG) stars to the luminosities of the Large and Small Magellanic Clouds (LMC and SMC, respectively). Combined, the peak contribution from these cool evolved stars occurs at {approx}3-4 {mu}m, where they produce 32% of the SMC light, and 25% of the LMC flux. The TP-AGB star contribution also peaks at {approx}3-4 {mu}m and amounts to 21% in both galaxies. The contribution from RSG stars peaks at shorter wavelengths, 2.2 {mu}m, where they provide 11% of the SMC flux, and 7% for the LMC. Both TP-AGB and RSG stars are short lived, and thus potentially impose a large stochastic scatter on the near-IR derived mass-to-light (M/L) ratios of galaxies at rest-frame 1-4 {mu}m. To minimize their impact on stellar mass estimates, one can use the M/L ratio at shorter wavelengths (e.g., at 0.8-1 {mu}m). At longer wavelengths ({>=}8 {mu}m), emission from dust in the interstellar medium dominates the flux. In the LMC, which shows strong polycyclic aromatic hydrocarbon (PAH) emission at 8 {mu}m, TP-AGB and RSG contribute less than 4% of the 8 {mu}m flux. However, 19% of the SMC 8 {mu}m flux is from evolved stars, nearly half of which is produced by the rarest, dustiest, carbon-rich TP-AGB stars. Thus, star formation rates of galaxies, based on an 8 {mu}m flux (e.g., observed-frame 24 {mu}m at z = 2), may be biased modestly high, especially for galaxies with little PAH emission.

  19. Toward connecting core-collapse supernova theory with observations. I. Shock revival in a 15 M {sub ☉} blue supergiant progenitor with SN 1987A energetics

    SciTech Connect

    Handy, Timothy; Plewa, Tomasz; Odrzywołek, Andrzej

    2014-03-10

    We study the evolution of the collapsing core of a 15 M {sub ☉} blue supergiant supernova progenitor from the core bounce until 1.5 s later. We present a sample of hydrodynamic models parameterized to match the explosion energetics of SN 1987A. We find the spatial model dimensionality to be an important contributing factor in the explosion process. Compared to two-dimensional (2D) simulations, our three-dimensional (3D) models require lower neutrino luminosities to produce equally energetic explosions. We estimate that the convective engine in our models is 4% more efficient in 3D than in 2D. We propose that the greater efficiency of the convective engine found in 3D simulations might be due to the larger surface-to-volume ratio of convective plumes, which aids in distributing energy deposited by neutrinos. We do not find evidence of the standing accretion shock instability or turbulence being a key factor in powering the explosion in our models. Instead, the analysis of the energy transport in the post-shock region reveals characteristics of penetrative convection. The explosion energy decreases dramatically once the resolution is inadequate to capture the morphology of convection on large scales. This shows that the role of dimensionality is secondary to correctly accounting for the basic physics of the explosion. We also analyze information provided by particle tracers embedded in the flow and find that the unbound material has relatively long residency times in 2D models, while in 3D a significant fraction of the explosion energy is carried by particles with relatively short residency times.

  20. Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the Warm Hypergiants: How to Tell Them Apart

    NASA Astrophysics Data System (ADS)

    Humphreys, Roberta M.; Gordon, Michael S.; Martin, John C.; Weis, Kerstin; Hahn, David

    2017-02-01

    In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe ii emission line stars, the B[e] supergiants, and the warm hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. We examine their similarities and differences and propose the following guidelines that can be used to help distinguish these stars in future work. (1) The B[e] supergiants have emission lines of [O i] and [Fe ii] in their spectra. Most of the spectroscopically confirmed sgB[e] stars also have warm circumstellar dust in their spectral energy distributions (SEDs). (2) Confirmed LBVs do not have the [O i] emission lines in their spectra. Some LBVs have [Fe ii] emission lines, but not all. Their SEDs show free–free emission in the near-infrared but no evidence for warm dust. Their most important and defining characteristic is the S Dor-type variability. (3) The warm hypergiants spectroscopically resemble the LBVs in their dense wind state and the B[e] supergiants. However, they are very dusty. Some have [Fe ii] and [O i] emission in their spectra like the sgB[e] stars, but are distinguished by their A- and F-type absorption-line spectra. In contrast, the B[e] supergiant spectra have strong continua and few if any apparent absorption lines. Candidate LBVs should share the spectral characteristics of the confirmed LBVs with low outflow velocities and the lack of warm circumstellar dust. Based on observations with the Multiple Mirror Telescope, a joint facility of the Smithsonian Institution and the University of Arizona and on observations obtained with the Large Binocular Telescope (LBT), an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of

  1. Chemical Peel

    MedlinePlus

    ... be done at different depths — light, medium or deep — depending on your desired results. Each type of ... chemical peel after 12 months to maintain results. Deep chemical peel. A deep chemical peel removes skin ...

  2. Wind structure of late B supergiants. I. Multi-line analyses of near-surface and wind structure in HD 199 478 (B8 Iae)

    NASA Astrophysics Data System (ADS)

    Markova, N.; Prinja, R. K.; Markov, H.; Kolka, I.; Morrison, N.; Percy, J.; Adelman, S.

    2008-08-01

    Aims: We provide a quantitative analysis of time-variable phenomena in the photospheric, near-star, and outflow regions of the late-B supergiant (SG) HD 199 478. This study aims to provide new perspectives on the nature of outflows in late-B SGs and on the influence of large-scale structures rooted at the stellar surface. Methods: The analysis is based primarily on optical spectroscopic datasets secured between 1999 and 2000 from the Bulgarian NAO, Tartu, and Ritter Observatories. The acquired time-series samples a wide range of weak metal lines, He i absorption, and both emission and absorption signatures in Hα. Non-LTE line synthesis modelling is conducted using FASTWIND for a strategic set of late-B SGs to constrain and compare their fundamental parameters within the context of extreme behaviour in the Hα lines. Results: The temporal behaviour of HD 199 478 is characterised by three key empirical properties: (i) systematic central velocity shifts in the photospheric absorption lines, including C ii and He i, over a characteristic time-scale of ~20 days; (ii) extremely strong, variable Hα emission with no clear modulation signal; and (iii) the occurrence in 2000 of a (rare) high-velocity absorption (HVA) event in Hα, which evolved over ~60 days, showing the clear signature of mass infall and outflows. In these properties HD 199 478 resembles few other late-B SGs with peculiar emission and HVAs in Hα (HD 91 619, HD 34 085, HD 96919). Different possibilities accounting for the phenomenon observed are indicated and briefly discussed. Conclusions: At the cooler temperature edge of B SGs, there are objects whose wind properties, as traced by Hα, are inconsistent with the predictions of the smooth, spherically symmetric wind approximation. This discordance is still not fully understood and may highlight the role of a non-spherical, disk-like, geometry, which may result from magnetically-driven equatorial compression of the gas. Ordered dipole magnetic fields may

  3. Chemical sensor

    NASA Technical Reports Server (NTRS)

    Rauh, R. David (Inventor)

    1990-01-01

    A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

  4. GHRS Observations of Cool, Low-Gravity Stars. 5; The Outer Atmosphere and Wind of the Nearby K Supergiant Lambda Velorum

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Robinson, Richard D.; Harper, Graham M.; Bennett, Philip D.; Brown, Alexander; Mullan, Dermott J.

    1999-01-01

    UV spectra of lambda Velorum taken with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope are used to probe the structure of the outer atmospheric layers and wind and to estimate the mass-loss rate from this K5 lb-II supergiant. VLA radio observations at lambda = 3.6 cm are used to obtain an independent check on the wind velocity and mass-loss rate inferred from the UV observations, Parameters of the chromospheric structure are estimated from measurements of UV line widths, positions, and fluxes and from the UV continuum flux distribution. The ratios of optically thin C II] emission lines indicate a mean chromospheric electron density of log N(sub e) approximately equal 8.9 +/- 0.2 /cc. The profiles of these lines indicate a chromospheric turbulence (v(sub 0) approximately equal 25-36 km/s), which greatly exceeds that seen in either the photosphere or wind. The centroids of optically thin emission lines of Fe II and of the emission wings of self-reversed Fe II lines indicate that they are formed in plasma approximately at rest with respect to the photosphere of the star. This suggests that the acceleration of the wind occurs above the chromospheric regions in which these emission line photons are created. The UV continuum detected by the GHRS clearly traces the mean flux-formation temperature as it increases with height in the chromosphere from a well-defined temperature minimum of 3200 K up to about 4600 K. Emission seen in lines of C III] and Si III] provides evidence of material at higher than chromospheric temperatures in the outer atmosphere of this noncoronal star. The photon-scattering wind produces self-reversals in the strong chromospheric emission lines, which allow us to probe the velocity field of the wind. The velocities to which these self-absorptions extend increase with intrinsic line strength, and thus height in the wind, and therefore directly map the wind acceleration. The width and shape of these self

  5. The 100-month Swift catalogue of supergiant fast X-ray transients. I. BAT on-board and transient monitor flares

    NASA Astrophysics Data System (ADS)

    Romano, P.; Krimm, H. A.; Palmer, D. M.; Ducci, L.; Esposito, P.; Vercellone, S.; Evans, P. A.; Guidorzi, C.; Mangano, V.; Kennea, J. A.; Barthelmy, S. D.; Burrows, D. N.; Gehrels, N.

    2014-02-01

    Context. Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) that are defined by their hard X-ray flaring behaviour. During these flares they reach peak luminosities of 1036-1037 erg s-1 for a few hours (in the hard X-ray), which are much shorter timescales than those characterizing Be/X-ray binaries. Aims: We investigate the characteristics of bright flares (detections in excess of 5σ) for a sample of SFXTs and their relation to the orbital phase. Methods: We have retrieved all Swift/BAT Transient Monitor light curves and collected all detections in excess of 5σ from both daily- and orbital-averaged light curves in the time range of 2005 February 12 to 2013 May 31 (MJD 53 413-56 443). We also considered all on-board detections as recorded in the same time span and selected those in excess of 5σ and within 4 arcmin of each source in our sample. Results: We present a catalogue of over a thousand BAT flares from 11 SFXTs, down to 15-150 keV fluxes of ~6 × 10-10 erg cm-2 s-1 (daily timescale) and ~1.5 × 10-9 erg cm-2 s-1 (orbital timescale, averaging ~800 s); the great majority of these flares are unpublished. The catalogue spans 100 months. This population is characterized by short (a few hundred seconds) and relatively bright (in excess of 100 mCrab, 15-50 keV) events. In the hard X-ray, these flares last generally much less than a day. Clustering of hard X-ray flares can be used to indirectly measure the length of an outburst, even when the low-level emission is not detected. We construct the distributions of flares, of their significance (in terms of σ), and of their flux as a function of orbital phase to infer the properties of these binary systems. In particular, we observe a trend of clustering of flares at some phases as Porb increases, which is consistent with a progression from tight circular or mildly eccentric orbits at short periods to wider and more eccentric orbits at longer orbital periods. Finally, we estimate the

  6. Chemical burns

    PubMed Central

    Cartotto, Robert C.; Peters, Walter J.; Neligan, Peter C.; Douglas, Leith G.; Beeston, Jeff

    1996-01-01

    Objectives To report a burn unit’s experience with chemical burns and to discuss the fundamental principles in managing chemical burns. Design A chart review. Setting A burn centre at a major university-affiliated hospital. Patients Twenty-four patients with chemical burns, representing 2.6% of all burn admissions over an 8-year period at the Ross Tilley Regional Adult Burn Centre. Seventy-five percent of the burn injuries were work-related accidents. Chemicals involved included hydrofluoric acid, sulfuric acid, black liquor, various lyes, potassium permanganate and phenol. Results Fourteen patients required excision and skin grafting. Complications were frequent and included ocular chemical contacts, wound infections, tendon exposures, toe amputation and systemic reactions from absorption of chemical. One patient died from a chemical scald burn to 98% of the body surface area. Conclusions The key principles in the management of chemical burns include removal of the chemical, copious irrigation, limited use of antidotes, correct estimation of the extent of injury, identification of systemic toxicity, treatment of ocular contacts and management of chemical inhalation injury. Individualized treatment is emphasized. PMID:8640619

  7. [Chemical weapons and chemical terrorism].

    PubMed

    Nakamura, Katsumi

    2005-10-01

    Chemical Weapons are kind of Weapons of Mass Destruction (WMD). They were used large quantities in WWI. Historically, large quantities usage like WWI was not recorded, but small usage has appeared now and then. Chemical weapons are so called "Nuclear weapon for poor countrys" because it's very easy to produce/possession being possible. They are categorized (1) Nerve Agents, (2) Blister Agents, (3) Cyanide (blood) Agents, (4) Pulmonary Agents, (5) Incapacitating Agents (6) Tear Agents from the viewpoint of human body interaction. In 1997 the Chemical Weapons Convention has taken effect. It prohibits chemical weapons development/production, and Organization for the Prohibition of Chemical Weapons (OPCW) verification regime contributes to the chemical weapons disposal. But possibility of possession/use of weapons of mass destruction by terrorist group represented in one by Matsumoto and Tokyo Subway Sarin Attack, So new chemical terrorism countermeasures are necessary.

  8. Chemical microsensors

    SciTech Connect

    Li, DeQuan; Swanson, Basil I.

    1995-01-01

    An article of manufacture is provided including a substrate having an oxide surface layer and a selective thin film of a cyclodextrin derivative chemically bound upon said substrate, said film is adapted for the inclusion of a selected organic compound therewith. Such an article can be either a chemical sensor capable of detecting a resultant mass change from inclusion of the selected organic compound or a chemical separator capable of reversibly selectively separating a selected organic compound.

  9. Chemical sensors

    DOEpatents

    Lowell, Jr., James R.; Edlund, David J.; Friesen, Dwayne T.; Rayfield, George W.

    1991-01-01

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising (a) a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, operatively coupled to (b) a transducer capable of directly converting said expansion or contraction to a measurable electrical response.

  10. Chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Frye-Mason, Gregory C.

    2001-01-01

    A chemical preconcentrator is disclosed with applications to chemical sensing and analysis. The preconcentrator can be formed by depositing a resistive heating element (e.g. platinum) over a membrane (e.g. silicon nitride) suspended above a substrate. A coating of a sorptive material (e.g. a microporous hydrophobic sol-gel coating or a polymer coating) is formed on the suspended membrane proximate to the heating element to selective sorb one or more chemical species of interest over a time period, thereby concentrating the chemical species in the sorptive material. Upon heating the sorptive material with the resistive heating element, the sorbed chemical species are released for detection and analysis in a relatively high concentration and over a relatively short time period. The sorptive material can be made to selectively sorb particular chemical species of interest while not substantially sorbing other chemical species not of interest. The present invention has applications for use in forming high-sensitivity, rapid-response miniaturized chemical analysis systems (e.g. a "chem lab on a chip").

  11. Chemical pneumonitis

    MedlinePlus

    ... chemicals. Alternative Names Aspiration pneumonia - chemical Images Lungs Respiratory system References Blanc PD. Acute responses to toxic exposures. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine . 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: ...

  12. Unnecessary Chemicals

    ERIC Educational Resources Information Center

    Johnson, Anita

    1978-01-01

    Discusses the health hazards resulting from chemical additions of many common products such as cough syrups, food dyes, and cosmetics. Steps being taken to protect consumers from these health hazards are included. (MDR)

  13. Chemical sensors

    DOEpatents

    Lowell, J.R. Jr.; Edlund, D.J.; Friesen, D.T.; Rayfield, G.W.

    1992-06-09

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising a mechanicochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, either operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical or optical response, or adhered to a second inert polymeric strip, or doped with a conductive material. 12 figs.

  14. Chemical sensors

    DOEpatents

    Lowell, Jr., James R.; Edlund, David J.; Friesen, Dwayne T.; Rayfield, George W.

    1992-01-01

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising a mechanicochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, either operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical or optical response, or adhered to a second inert polymeric strip, or doped with a conductive material.

  15. Chemical carcinogenesis.

    PubMed

    Oliveira, Paula A; Colaço, Aura; Chaves, Raquel; Guedes-Pinto, Henrique; De-La-Cruz P, Luis F; Lopes, Carlos

    2007-12-01

    The use of chemical compounds benefits society in a number of ways. Pesticides, for instance, enable foodstuffs to be produced in sufficient quantities to satisfy the needs of millions of people, a condition that has led to an increase in levels of life expectancy. Yet, at times, these benefits are offset by certain disadvantages, notably the toxic side effects of the chemical compounds used. Exposure to these compounds can have varying effects, ranging from instant death to a gradual process of chemical carcinogenesis. There are three stages involved in chemical carcinogenesis. These are defined as initiation, promotion and progression. Each of these stages is characterised by morphological and biochemical modifications and result from genetic and/or epigenetic alterations. These genetic modifications include: mutations in genes that control cell proliferation, cell death and DNA repair--i.e. mutations in proto-oncogenes and tumour suppressing genes. The epigenetic factors, also considered as being non-genetic in character, can also contribute to carcinogenesis via epigenetic mechanisms which silence gene expression. The control of responses to carcinogenesis through the application of several chemical, biochemical and biological techniques facilitates the identification of those basic mechanisms involved in neoplasic development. Experimental assays with laboratory animals, epidemiological studies and quick tests enable the identification of carcinogenic compounds, the dissection of many aspects of carcinogenesis, and the establishment of effective strategies to prevent the cancer which results from exposure to chemicals.

  16. Chemical abundances of massive stars in Local Group galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.; Kaufer, Andreas; Tolstoy, Eline; Kudritzki, Rolf-Peter; Przybilla, Norbert; Smartt, Stephen J.; Lennon, Daniel J.

    The relative abundances of elements in galaxies can provide valuable information on the stellar and chemical evolution of a galaxy. While nebulae can provide abundances for a variety of light elements, stars are the only way to directly determine the abundances of iron-group and s-process and r-process elements in a galaxy. The new 8m and 10m class telescopes and high-efficiency spectrographs now make high-quality spectral observations of bright supergiants possible in dwarf galaxies in the Local Group. We have been concentrating on elemental abundances in the metal-poor dwarf irregular galaxies, NGC 6822, WLM, Sextants A, and GR 8. Comparing abundance ratios to those predicted from their star formation histories, determined from color-magnitude diagrams, and comparing those ratios between these galaxies can give us new insights into the evolution of these dwarf irregular galaxies. Iron-group abundances also allow us to examine the metallicities of the stars in these galaxies directly, which affects their inferred mass loss rates and predicted stellar evolution properties.

  17. Delicious Chemicals.

    ERIC Educational Resources Information Center

    Barry, Dana M.

    This paper presents an approach to chemistry and nutrition that focuses on food items that people consider delicious. Information is organized according to three categories of food chemicals that provide energy to the human body: (1) fats and oils; (2) carbohydrates; and (3) proteins. Minerals, vitamins, and additives are also discussed along with…

  18. Chemical Mahjong

    ERIC Educational Resources Information Center

    Cossairt, Travis J.; Grubbs, W. Tandy

    2011-01-01

    An open-access, Web-based mnemonic game is described whereby introductory chemistry knowledge is tested using mahjong solitaire game play. Several tile sets and board layouts are included that are themed upon different chemical topics. Introductory tile sets can be selected that prompt the player to match element names to symbols and metric…

  19. Chemical warfare

    PubMed Central

    Samuels, Richard Ian; Mattoso, Thalles Cardoso; Moreira, Denise D.O.

    2013-01-01

    Leaf-cutting ants are well known for their highly complex social organization, which provides them with a strong defense against parasites invading their colonies. Besides this attribute, these insects have morphological, physiological and structural characteristics further reinforcing the defense of their colonies. With the discovery of symbiotic bacteria present on the integument of leaf-cutting ants, a new line of defense was proposed and considered to be specific for the control of a specialized fungal parasite of the ants’ fungus gardens (Escovopsis). However, recent studies have questioned the specificity of the integumental bacteria, as they were also found to inhibit a range of fungi, including entomopathogens. The microbiota associated with the leaf-cutting ant gardens has also been proposed as another level of chemical defense, protecting the garden from parasite invasion. Here we review the chemical defense weaponry deployed by leaf-cutting ants against parasites of their fungus gardens and of the ants themselves. PMID:23795235

  20. Chemical Analyses

    NASA Technical Reports Server (NTRS)

    Bulluck, J. W.; Rushing, R. A.

    1994-01-01

    As a preliminary study on the effects of chemical aging of polymer materials MERL and TRI have examined two polymeric materials that are typically used for offshore umbilical applications. These two materials were Tefzel, a copolymer of ethylene and tetrafluoroethylene, and Coflon, polyvinylidene fluoride. The Coflon specimens were cut from pipe sections and exposed to H2S at various temperatures and pressures. One of these specimens was tested for methane permeation, and another for H2S permeation. The Tefzel specimens were cut from .05 mm sheet stock material and were exposed to methanol at elevated temperature and pressure. One of these specimens was exposed to methanol permeation for 2 days at 100 C and 2500 psi. An additional specimen was exposed to liquid methanol for 3 days at 150 C and 15 Bar. Virgin specimens of each material were similarly prepared and tested.

  1. Household Chemical Emergencies

    MedlinePlus

    ... Chemical Emergencies Hurricanes Landslides & Debris Flow Nuclear ... containing hazardous materials or chemicals. Although the risk of a chemical accident is slight, knowing how to handle these products ...

  2. Chemical Ecology: Chemical Communication in Nature.

    ERIC Educational Resources Information Center

    Wood, William F.

    1983-01-01

    Substances that deliver chemical messages between same/different species are called semiochemicals. Surveyed are three types of semiochemicals (pheromones, allomones, and kairomones), types of organisms involved, and specific chemicals used to carry the various kinds of messages. (JN)

  3. The Chemical Engineer in the Chemical Industry.

    ERIC Educational Resources Information Center

    Zabicky, Jacob

    1986-01-01

    Describes a course for third- or fourth-year chemical engineering students designed to acquaint them with the chemical industry. The course deals with productivity, characteristics of the chemical industry, sources of information, industrial intelligence, research and development, patent law, technology transfer, and quality control. (TW)

  4. Safer Chemicals Research

    EPA Pesticide Factsheets

    EPA's Chemical Safety research protects human health and the environment by evaluating chemicals for potential risk and providing tools and guidance for improved chemical production that supports a sustainable environment.

  5. Microfluidic chemical reaction circuits

    SciTech Connect

    Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C; Huang, Jiang; Heath, James R; Phelps, Michael E; Quake, Stephen R; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  6. Nature's chemicals and synthetic chemicals: comparative toxicology.

    PubMed Central

    Ames, B N; Profet, M; Gold, L S

    1990-01-01

    The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol (in broccoli) and ethanol. Trade-offs between synthetic and natural pesticides are discussed. The finding that in high-dose tests, a high proportion of both natural and synthetic chemicals are carcinogens, mutagens, teratogens, and clastogens (30-50% for each group) undermines current regulatory efforts to protect public health from synthetic chemicals based on these tests. PMID:2217211

  7. Nature's chemicals and synthetic chemicals: Comparative toxicology

    SciTech Connect

    Ames, B.N.; Profet, M.; Gold, L.S. )

    1990-10-01

    The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol (in broccoli) and ethanol. Trade-offs between synthetic and natural pesticides are discussed. The finding that in high-dose tests, a high proportion of both natural and synthetic chemicals are carcinogens, mutagens, teratogens, and clastogens (30-50{percent} for each group) undermines current regulatory efforts to protect public health from synthetic chemicals based on these tests.

  8. Chemical Industry Corrosion Management

    SciTech Connect

    2003-02-01

    Improved Corrosion Management Could Provide Significant Cost and Energy Savings for the Chemical Industry. In the chemical industry, corrosion is often responsible for significant shutdown and maintenance costs.

  9. Supergiant pulses from extragalactic neutron stars

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.; Wasserman, Ira

    2016-03-01

    We consider radio bursts that originate from extragalactic neutron stars (NSs) by addressing three questions about source distances. What are the physical limitations on coherent radiation at GHz frequencies? Do they permit detection at cosmological distances? How many bursts per NS are needed to produce the inferred burst rate ˜103-104sky-1 d-1? The burst rate is comparable to the NS formation rate in a Hubble volume, requiring only one per NS if they are bright enough. Radiation physics suggests a closer population, requiring more bursts per NS and increasing the chances for repeats. Bursts comprise sub-ns, coherent shot pulses superposed incoherently to produce ms-duration ˜1 Jy amplitudes; each shot pulse can be much weaker than 1 Jy, placing less restrictive requirements on the emission process. None the less, single shot pulses are similar to the extreme, unresolved (<0.4 ns) MJy shot pulse seen from the Crab pulsar, consistent with coherent curvature radiation emitted near the light cylinder by an almost neutral clump with net charge ˜± 1021e and total energy ≳ 1023 erg. Bursts from Gpc distances require incoherent superposition of {˜ } 10^{12}d_Gpc^2 shot pulses or a total energy ≳ 10^{35} d_Gpc^2 erg. The energy reservoir near the light cylinder limits the detection distance to ≲ few × 100 Mpc for a fluence ˜1 Jy ms unless conditions are more extreme than for the Crab pulsar, such as in magnetars. We discuss contributions to dispersion measures from galaxy clusters and we propose tests for the overall picture presented.

  10. Outer atmospheres of giant and supergiant stars

    NASA Technical Reports Server (NTRS)

    Brown, A.

    1984-01-01

    The properties of the chromospheres, transition regions and coronas of cool evolved stars are reviewed based primarily on recent ultraviolet and X-ray studies. Determinations of mass loss rates using new observational techniques in the ultraviolet and radio spectral regions are discussed and observations indicating general atmospheric motions are considered. The techniques available for the quantitative modeling of these atmospheres are outlined and recent results discussed. Finally, the current rudimentary understanding of the evolution of these outer atmospheres and its causes are considered.

  11. Red Supergiants in the Local Group

    NASA Astrophysics Data System (ADS)

    Levesque, E. M.

    2013-05-01

    Galaxies in the Local Group span a factor of 15 in metallicity, ranging from the super-solar M 31 to the Wolf-Lundmark-Melotte (WLM) galaxy, which is the lowest-metallicity (0.1 Z⊙) Local Group galaxy currently forming stars. Studies of massive star populations across this broad range of environments have revealed important metal-licity-dependent evolutionary trends, allowing us to test the accuracy of stellar evolutionary tracks at these metallicities for the first time. The RSG population is particularly valuable as a key mass-losing phase of moderately massive stars and a source of core-collapse supernova progenitors. By reviewing recent work on the RSG populations in the Local Group, we are able to quantify limits on these stars' effective temperatures and masses and probe the relationship between RSG mass loss behaviors and host environments. Extragalactic surveys of RSGs have also revealed several unusual RSGs that display signs of unusual spectral variability and dust production, traits that may potentially also correlate with the stars' host environments. I will present some of the latest work that has advanced our understanding of RSGs in the Local Group, and consider the many new questions posed by our ever-evolving picture of these stars.

  12. Multimedia regulated chemicals

    SciTech Connect

    Lee, C.C.; Huffman, G.L.; Mao, Y.L.

    1999-10-01

    This article examines those chemicals that are listed in either environmental laws or regulations. Its objective is to help readers determine which laws regulate what types of chemicals and which types of chemicals are regulated by what laws. It is multimedia in scope, describing the various chemicals that are regulated in the different media (i.e., air, water, or land).

  13. PINS chemical identification software

    DOEpatents

    Caffrey, Augustine J.; Krebs, Kennth M.

    2004-09-14

    An apparatus and method for identifying a chemical compound. A neutron source delivers neutrons into the chemical compound. The nuclei of chemical elements constituting the chemical compound emit gamma rays upon interaction with the neutrons. The gamma rays are characteristic of the chemical elements constituting the chemical compound. A spectrum of the gamma rays is generated having a detection count and an energy scale. The energy scale is calibrated by comparing peaks in the spectrum to energies of pre-selected chemical elements in the spectrum. A least-squares fit completes the calibration. The chemical elements constituting the chemical compound can be readily determined, which then allows for identification of the chemical compound.

  14. Chemical Data Reporting

    EPA Pesticide Factsheets

    The Chemical Data Reporting (CDR) site provides information on reporting requirements under TSCA's Chemical Data Reporting Rule. The site provides instruction to data submitters on how to report and enable users to download the reported information.

  15. Chemical Industry Bandwidth Study

    SciTech Connect

    none,

    2006-12-01

    The Chemical Bandwidth Study provides a snapshot of potentially recoverable energy losses during chemical manufacturing. The advantage of this study is the use of "exergy" analysis as a tool for pinpointing inefficiencies.

  16. Personal Chemical Exposure informatics

    EPA Science Inventory

    Chemical Exposure science is the study of human contact with chemicals (from manufacturing facilities, everyday products, waste) occurring in their environments and advances knowledge of the mechanisms and dynamics of events that cause or prevent adverse health outcomes. (adapted...

  17. Chemical burn or reaction

    MedlinePlus

    ... different products that contain toxic chemicals such as ammonia and bleach. The mixture can give off hazardous ... chemicals immediately after use. Use paints, petroleum products, ammonia, bleach, and other products that give off fumes ...

  18. Chemicals Industry Vision

    SciTech Connect

    none,

    1996-12-01

    Chemical industry leaders articulated a long-term vision for the industry, its markets, and its technology in the groundbreaking 1996 document Technology Vision 2020 - The U.S. Chemical Industry. (PDF 310 KB).

  19. Chemical Transformation Simulator

    EPA Science Inventory

    The Chemical Transformation Simulator (CTS) is a web-based, high-throughput screening tool that automates the calculation and collection of physicochemical properties for an organic chemical of interest and its predicted products resulting from transformations in environmental sy...

  20. Capacitive chemical sensor

    DOEpatents

    Manginell, Ronald P; Moorman, Matthew W; Wheeler, David R

    2014-05-27

    A microfabricated capacitive chemical sensor can be used as an autonomous chemical sensor or as an analyte-sensitive chemical preconcentrator in a larger microanalytical system. The capacitive chemical sensor detects changes in sensing film dielectric properties, such as the dielectric constant, conductivity, or dimensionality. These changes result from the interaction of a target analyte with the sensing film. This capability provides a low-power, self-heating chemical sensor suitable for remote and unattended sensing applications. The capacitive chemical sensor also enables a smart, analyte-sensitive chemical preconcentrator. After sorption of the sample by the sensing film, the film can be rapidly heated to release the sample for further analysis. Therefore, the capacitive chemical sensor can optimize the sample collection time prior to release to enable the rapid and accurate analysis of analytes by a microanalytical system.

  1. Computing Equilibrium Chemical Compositions

    NASA Technical Reports Server (NTRS)

    Mcbride, Bonnie J.; Gordon, Sanford

    1995-01-01

    Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

  2. Chemical and Environmental Technology.

    ERIC Educational Resources Information Center

    Sheather, Harry

    The two-year curriculum in chemical technology presented in the document is designed to prepare high school graduates for technical positions in the chemical industry. Course outlines are given for general chemistry, chemical calculations, quantitative analysis, environmental chemistry, organic chemistry 1 and 2, instrumental analysis, and…

  3. Toxicology and Chemical Safety.

    ERIC Educational Resources Information Center

    Hall, Stephen K.

    1983-01-01

    Topics addressed in this discussion of toxicology and chemical safety include routes of exposure, dose/response relationships, action of toxic substances, and effects of exposure to chemicals. Specific examples are used to illustrate the principles discussed. Suggests prudence in handling any chemicals, whether or not toxicity is known. (JN)

  4. Chemicals for worldwide aquaculture

    USGS Publications Warehouse

    Schnick, R.A.

    1991-01-01

    Regulations and therapeutants or other safe chemicals that are approved or acceptable for use in the aquaculture industry in the US, Canada, Europe and Japan are presented, discussing also compounds that are unacceptable for aquaculture. Chemical use practices that could affect public health are considered and details given regarding efforts to increase the number of registered and acceptable chemicals.

  5. Naturally occurring chemical carcinogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural products are chemicals found in nature which have unique pharmacological effects. Humans are exposed to many of these bioactive naturally occurring chemicals via the air breathed, the water drunk and the food eaten. Exposure also occurs in clinical settings. Naturally occurring chemicals ...

  6. Chemical Physics Courses.

    ERIC Educational Resources Information Center

    Lee, J.; Munn, R. W.

    1978-01-01

    This is a guide to the chemical physics major. The scope of chemical physics is presented, along with the general features of course contents and possible course structures. This information was derived from a survey of British universities and colleges offering undergraduate degree courses in chemical physics. (BB)

  7. The Chemical Literature

    ERIC Educational Resources Information Center

    Crombie, D. A.

    1975-01-01

    Describes a course designed to acquaint students with making a search of chemical literature. The course presents various classes of chemical publication and the methods of using Beilstein and Chemical Abstracts. A follow-up project involves each student in a search for references for one or two organic compounds. (GS)

  8. Chemical Synthesis of Proteins

    PubMed Central

    Nilsson, Bradley L.; Soellner, Matthew B.; Raines, Ronald T.

    2010-01-01

    Proteins have become accessible targets for chemical synthesis. The basic strategy is to use native chemical ligation, Staudinger ligation, or other orthogonal chemical reactions to couple synthetic peptides. The ligation reactions are compatible with a variety of solvents and proceed in solution or on a solid support. Chemical synthesis enables a level of control on protein composition that greatly exceeds that attainable with ribosome-mediated biosynthesis. Accordingly, the chemical synthesis of proteins is providing previously unattainable insight into the structure and function of proteins. PMID:15869385

  9. Chemical exchange program analysis.

    SciTech Connect

    Waffelaert, Pascale

    2007-09-01

    As part of its EMS, Sandia performs an annual environmental aspects/impacts analysis. The purpose of this analysis is to identify the environmental aspects associated with Sandia's activities, products, and services and the potential environmental impacts associated with those aspects. Division and environmental programs established objectives and targets based on the environmental aspects associated with their operations. In 2007 the most significant aspect identified was Hazardous Materials (Use and Storage). The objective for Hazardous Materials (Use and Storage) was to improve chemical handling, storage, and on-site movement of hazardous materials. One of the targets supporting this objective was to develop an effective chemical exchange program, making a business case for it in FY07, and fully implementing a comprehensive chemical exchange program in FY08. A Chemical Exchange Program (CEP) team was formed to implement this target. The team consists of representatives from the Chemical Information System (CIS), Pollution Prevention (P2), the HWMF, Procurement and the Environmental Management System (EMS). The CEP Team performed benchmarking and conducted a life-cycle analysis of the current management of chemicals at SNL/NM and compared it to Chemical Exchange alternatives. Those alternatives are as follows: (1) Revive the 'Virtual' Chemical Exchange Program; (2) Re-implement a 'Physical' Chemical Exchange Program using a Chemical Information System; and (3) Transition to a Chemical Management Services System. The analysis and benchmarking study shows that the present management of chemicals at SNL/NM is significantly disjointed and a life-cycle or 'Cradle-to-Grave' approach to chemical management is needed. This approach must consider the purchasing and maintenance costs as well as the cost of ultimate disposal of the chemicals and materials. A chemical exchange is needed as a mechanism to re-apply chemicals on site. This will not only reduce the quantity of

  10. ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY Canis Majoris

    NASA Astrophysics Data System (ADS)

    Decin, L.; Richards, A. M. S.; Millar, T. J.; Baudry, A.; De Beck, E.; Homan, W.; Smith, N.; Van de Sande, M.; Walsh, C.

    2016-07-01

    Context. At the end of their lives, most stars lose a significant amount of mass through a stellar wind. The specific physical and chemical circumstances that lead to the onset of the stellar wind for cool luminous stars are not yet understood. Complex geometrical morphologies in the circumstellar envelopes prove that various dynamical and chemical processes are interlocked and that their relative contributions are not easy to disentangle. Aims: We aim to study the inner-wind structure (R< 250 R⋆) of the well-known red supergiant VY CMa, the archetype for the class of luminous red supergiant stars experiencing high mass loss. Specifically, the objective is to unravel the density structure in the inner envelope and to examine the chemical interaction between gas and dust species. Methods: We analyse high spatial resolution (~0.̋24×0.̋13) ALMA science verification (SV) data in band 7, in which four thermal emission lines of gaseous sodium chloride (NaCl) are present at high signal-to-noise ratio. Results: For the first time, the NaCl emission in the inner wind region of VY CMa is spatially resolved. The ALMA observations reveal the contribution of up to four different spatial regions. The NaCl emission pattern is different compared to the dust continuum and TiO2 emission already analysed from the ALMA SV data. The emission can be reconciled with an axisymmetric geometry, where the lower density polar/rotation axis has a position angle of ~50° measured from north to east. However, this picture cannot capture the full morphological diversity, and discrete mass ejection events need to be invoked to explain localized higher-density regions. The velocity traced by the gaseous NaCl line profiles is significantly lower than the average wind terminal velocity, and much slower than some of the fastest mass ejections, signalling a wide range of characteristic speeds for the mass loss. Gaseous NaCl is detected far beyond the main dust condensation region. Realising the

  11. The chemical juggernaut.

    PubMed

    Cadbury, D

    1997-01-01

    Man-made chemicals pervade and support every aspect of modern living. The chemical industry has become such a powerful force in the global economy, sales of synthetic chemicals and products derived from them constitute well in excess of a third of the world's gross national product. But, these man-made chemicals are also 'elixirs of death,' the symbol of human destruction. Laboratory tests have shown that a number of chemicals in common use possess a remarkable property: they can weakly mimic or modify the action of human hormones. It has been proven that some chemicals found in plastics, pesticides, and industrial products are weakly estrogenic, modifying the action of the female hormone. In addition, other chemicals affect the male hormones, androgens, or anti-androgens; others are thought to target different hormone systems, such as thyroid and adrenal glands. Many research studies are being conducted to establish the impact of chemicals on human health. Of special concern are the rising incidence of testicular cancer, decline in human sperm counts, and the sharp rise of breast cancer. In conclusion, although there is a worldwide debate on the effects of chemical exposure on humans, the significance of findings for human health, concerning testicular and breast cancer, are still unknown. An international treaty is called for to control the use of the persistent hormonally active chemicals.

  12. Chemical penetration enhancers.

    PubMed

    Newton, Stephen J

    2013-01-01

    Chemical penetration enhancers are utilized in topical preparations as a method for enhancing permeation of drugs across the skin. In particular, they are utilized for transdermal delivery of medications in an attempt to produce a systemic response, to avoid first-pass metabolism, and to decrease the gastrointestinal transit time observed with oral medications. A review of the selection of chemical penetration enhancers, their mechanism of action, the most common chemical penetration enhancers in each class, and alternatives will be discussed in detail.

  13. Excimer laser chemical problems

    SciTech Connect

    Tennant, R.; Peterson, N.

    1982-01-01

    Techniques need to be developed to maintain XeF and XeCl laser performance over long periods of time without degradation resulting from chemical processes occurring within the laser. The dominant chemical issues include optical damage, corrosions of laser materials, gas contamination, and control of halogen concentration. Each of these issues are discussed and summarized. The methods of minimizing or controlling the chemical processes involved are presented.

  14. Multivariate Quantitative Chemical Analysis

    NASA Technical Reports Server (NTRS)

    Kinchen, David G.; Capezza, Mary

    1995-01-01

    Technique of multivariate quantitative chemical analysis devised for use in determining relative proportions of two components mixed and sprayed together onto object to form thermally insulating foam. Potentially adaptable to other materials, especially in process-monitoring applications in which necessary to know and control critical properties of products via quantitative chemical analyses of products. In addition to chemical composition, also used to determine such physical properties as densities and strengths.

  15. Chemical Processing Manual

    NASA Technical Reports Server (NTRS)

    Beyerle, F. J.

    1972-01-01

    Chemical processes presented in this document include cleaning, pickling, surface finishes, chemical milling, plating, dry film lubricants, and polishing. All types of chemical processes applicable to aluminum, for example, are to be found in the aluminum alloy section. There is a separate section for each category of metallic alloy plus a section for non-metals, such as plastics. The refractories, super-alloys and titanium, are prime candidates for the space shuttle, therefore, the chemical processes applicable to these alloys are contained in individual sections of this manual.

  16. Field emission chemical sensor

    DOEpatents

    Panitz, J.A.

    1983-11-22

    A field emission chemical sensor for specific detection of a chemical entity in a sample includes a closed chamber enclosing two field emission electrode sets, each field emission electrode set comprising (a) an electron emitter electrode from which field emission electrons can be emitted when an effective voltage is connected to the electrode set; and (b) a collector electrode which will capture said electrons emitted from said emitter electrode. One of the electrode sets is passive to the chemical entity and the other is active thereto and has an active emitter electrode which will bind the chemical entity when contacted therewith.

  17. 310 Facility chemical specifications

    SciTech Connect

    Hagerty, K.J.

    1997-05-21

    The 300 area Treated Effluent Disposal Facility (TEDF) was designed and built to treat the waste water from the 300 area process sewer system. Several treatment technologies are employed to remove the trace quantities of contaminants in the stream, including iron coprecipitation, clarification, filtration, ion exchange, and ultra violet light/hydrogen peroxide oxidation of organics. The chemicals that will be utilized in the treatment process are hydrogen peroxide, sulfuric acid, sodium hydroxide, and ferric chloride. This document annotates the required chemical characteristics of TEDF bulk chemicals as well as the criteria that were used to establish these criteria. The chemical specifications in appendix B are generated from this information.

  18. Apparatus for chemical synthesis

    DOEpatents

    Kong, Peter C.; Herring, J. Stephen; Grandy, Jon D.

    2011-05-10

    A method and apparatus for forming a chemical hydride is described and which includes a pseudo-plasma-electrolysis reactor which is operable to receive a solution capable of forming a chemical hydride and which further includes a cathode and a movable anode, and wherein the anode is moved into and out of fluidic, ohmic electrical contact with the solution capable of forming a chemical hydride and which further, when energized produces an oxygen plasma which facilitates the formation of a chemical hydride in the solution.

  19. Chemical Accident Prevention - Chemicals in your Community

    EPA Pesticide Factsheets

    This pamphlet summarizes the information you can obtain under Emergency Planning and Community Right-to-Know and Clean Air Act, how you can use these sources to build a snapshot of chemicals stored and released, and how SERCs and LEPCs can improve safety.

  20. Microorganisms and Chemical Pollution

    ERIC Educational Resources Information Center

    Alexander, M.

    1973-01-01

    Discusses the importance of microorganisms in chemical pollution and pollution abatement. Selected chemical pollutants are chosen to illustrate that microorganisms synthesize hazardous substances from reasonably innocuous precursors, while others act as excellent environmental decontaminating agents by removing undesirable natural and synthetic…

  1. Chemical Reactivity Test (CRT)

    SciTech Connect

    Zaka, F.

    2016-12-13

    The Chemical Reactivity Test (CRT) is used to determine the thermal stability of High Explosives (HEs) and chemical compatibility between (HEs) and alien materials. The CRT is one of the small-scale safety tests performed on HE at the High Explosives Applications Facility (HEAF).

  2. Chemicals and Allied Products.

    ERIC Educational Resources Information Center

    Nelson, R. F.; Hovious, J. C.

    1978-01-01

    Presents a literature review of wastes from chemical industry, covering publications of 1976-77. This review covers: (1) wastewater treatment by-product type; (2) biological, and physical/chemical treatments; and (3) source treatment. A list of 80 references is also presented. (HM)

  3. Chemical Compositions of Stars

    NASA Astrophysics Data System (ADS)

    Leckrone, D.; Murdin, P.

    2000-11-01

    In 1835, in a famously inaccurate forecast, the French philosopher Auguste Comte wrote of stars that, `We understand the possibility of determining their shapes, their distances, their sizes and their movements; whereas we would never know how to study by any means their chemical composition…'. At the close of the 20th century the accurate measurement of the abundances of the chemical elements in...

  4. Chemicals in Everyday Life.

    ERIC Educational Resources Information Center

    Seymour, Raymond B.

    1987-01-01

    Discusses the dependencies of people on chemicals in various aspects of life. Describes some of the natural and synthetic chemicals currently used in food production, clothing, shelter, travel and exploration, sports and recreation, ventilation, heating and cooling, communications, decoration, sanitation, and education. (TW)

  5. Difficult Decisions: Chemical Warfare.

    ERIC Educational Resources Information Center

    Slesnick, Irwin L.; Miller, John A.

    1988-01-01

    Gives the background history and chemistry of modern day chemical warfare from World War I to the present. Provides discussion questions to stimulate deeper thinking on the issue. Contains a discussion activity called "Can New Chemical Weapons Lead to Humane Warfare?" (CW)

  6. Great Lakes: Chemical Monitoring

    ERIC Educational Resources Information Center

    Delfino, Joseph J.

    1976-01-01

    The Tenth Great Lakes Regional Meeting of the American Chemical Society met to assess current Chemical Research activity in the Great Lakes Basin, and addressed to the various aspects of the theme, Chemistry of the Great Lakes. Research areas reviewed included watershed studies, atmospheric and aquatic studies, and sediment studies. (BT)

  7. Chemical Equation Balancing.

    ERIC Educational Resources Information Center

    Blakley, G. R.

    1982-01-01

    Reviews mathematical techniques for solving systems of homogeneous linear equations and demonstrates that the algebraic method of balancing chemical equations is a matter of solving a system of homogeneous linear equations. FORTRAN programs using this matrix method to chemical equation balancing are available from the author. (JN)

  8. Chemical Reaction Problem Solving.

    ERIC Educational Resources Information Center

    Veal, William

    1999-01-01

    Discusses the role of chemical-equation problem solving in helping students predict reaction products. Methods for helping students learn this process must be taught to students and future teachers by using pedagogical skills within the content of chemistry. Emphasizes that solving chemical reactions should involve creative cognition where…

  9. Tortuous path chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Wheeler, David R.; Simonson, Robert J.

    2010-09-21

    A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

  10. Chemical recognition software

    SciTech Connect

    Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.H. Jr.; Tisone, G.C.

    1994-06-01

    We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures, even when the mixture is noisy and contaminated with unknowns.

  11. Chemical recognition software

    SciTech Connect

    Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.J. Jr.; Tisone, G.C.

    1994-12-01

    We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures. even when the mixture is noisy and contaminated with unknowns.

  12. Prioritizing industrial chemical hazards.

    PubMed

    Hauschild, Veronique D; Bratt, Gary M

    This article describes the approach used to develop a prioritized list of toxic and hazardous industrial chemical hazards considered to pose substantial risk to deployed troops and military operations. The U.S. Army Center for Health Promotion and Preventive Medicine published the prioritized list in November 2003. The work was performed as part of a multinational military effort supported by Canada, the United Kingdom, and the United States. Previous chemical priority lists had been developed to support military as well as homeland defense research, development, and acquisition communities to determine enhanced detection and protection needs. However, there were questions as to the adequacy of the methodologies and focus of the previous efforts. This most recent effort is a more extensive evaluation of over 1700 industrial chemicals, with a modified methodology that includes not only the assessment of acute inhalation toxic industrial chemicals (TICs), but also chemicals/compounds that pose substantial physical risk (from fire/explosion) and those that may pose acute ingestion risks (such as in water supplies). The methodology was designed to rank such hazards from a strategic (global) military perspective, but it may be adapted to address more site/user specific needs. Users of this or any other chemical priority list are cautioned that the derivation of such lists is largely influenced by subjective decisions and significant variability in chemical-specific data availability and quality.

  13. Chemical process hazards analysis

    SciTech Connect

    1996-02-01

    The Office of Worker Health and Safety (EH-5) under the Assistant Secretary for the Environment, Safety and Health of the US Department (DOE) has published two handbooks for use by DOE contractors managing facilities and processes covered by the Occupational Safety and Health Administration (OSHA) Rule for Process Safety Management of Highly Hazardous Chemicals (29 CFR 1910.119), herein referred to as the PSM Rule. The PSM Rule contains an integrated set of chemical process safety management elements designed to prevent chemical releases that can lead to catastrophic fires, explosions, or toxic exposures. The purpose of the two handbooks, ``Process Safety Management for Highly Hazardous Chemicals`` and ``Chemical Process Hazards Analysis,`` is to facilitate implementation of the provisions of the PSM Rule within the DOE. The purpose of this handbook ``Chemical Process Hazards Analysis,`` is to facilitate, within the DOE, the performance of chemical process hazards analyses (PrHAs) as required under the PSM Rule. It provides basic information for the performance of PrHAs, and should not be considered a complete resource on PrHA methods. Likewise, to determine if a facility is covered by the PSM rule, the reader should refer to the handbook, ``Process Safety Management for Highly Hazardous Chemicals`` (DOE- HDBK-1101-96). Promulgation of the PSM Rule has heightened the awareness of chemical safety management issues within the DOE. This handbook is intended for use by DOE facilities and processes covered by the PSM rule to facilitate contractor implementation of the PrHA element of the PSM Rule. However, contractors whose facilities and processes not covered by the PSM Rule may also use this handbook as a basis for conducting process hazards analyses as part of their good management practices. This handbook explains the minimum requirements for PrHAs outlined in the PSM Rule. Nowhere have requirements been added beyond what is specifically required by the rule.

  14. Chemical warfare agents

    PubMed Central

    Ganesan, K.; Raza, S. K.; Vijayaraghavan, R.

    2010-01-01

    Among the Weapons of Mass Destruction, chemical warfare (CW) is probably one of the most brutal created by mankind in comparison with biological and nuclear warfare. Chemical weapons are inexpensive and are relatively easy to produce, even by small terrorist groups, to create mass casualties with small quantities. The characteristics of various CW agents, general information relevant to current physical as well as medical protection methods, detection equipment available and decontamination techniques are discussed in this review article. A brief note on Chemical Weapons Convention is also provided. PMID:21829312

  15. Chemical Hygiene Program

    NASA Technical Reports Server (NTRS)

    Mayor, Antoinette C.

    1999-01-01

    The Chemical Management Team is responsible for ensuring compliance with the OSHA Laboratory Standard. The program at Lewis Research Center (LeRC) evolved over many years to include training, developing Standard Operating Procedures (SOPS) for each laboratory process, coordinating with other safety and health organizations and teams at the Center, and issuing an SOP binder. The Chemical Hygiene Policy was first established for the Center. The Chemical Hygiene Plan was established and reviewed by technical, laboratory and management for viability and applicability to the Center. A risk assessment was conducted for each laboratory. The laboratories were prioritized by order of risk, higher risk taking priority. A Chemical Management Team staff member interviewed the lead researcher for each laboratory process to gather the information needed to develop the SOP for the process. A binder containing the Chemical Hygiene Plan, the SOP, a map of the laboratory identifying the personal protective equipment and best egress, and glove guides, as well as other guides for safety and health. Each laboratory process has been captured in the form of an SOP. The chemicals used in the procedure have been identified and the information is used to reduce the number of chemicals in the lab. The Chemical Hygiene Plan binder is used as a training tool for new employees. LeRC is in compliance with the OSHA Standard. The program was designed to comply with the OSHA standard. In the process, we have been able to assess the usage of chemicals in the laboratories, as well as reduce or relocate the chemicals being stored in the laboratory. Our researchers are trained on the hazards of the materials they work with and have a better understanding of the hazards of the process and what is needed to prevent any incident. From the SOP process, we have been able to reduce our chemical inventory, determine and implement better hygiene procedures and equipment in the laboratories, and provide

  16. Chemical ecology of fungi.

    PubMed

    Spiteller, Peter

    2015-07-01

    Fungi are widespread in nature and have conquered nearly every ecological niche. Fungi occur not only in terrestrial but also in freshwater and marine environments. Moreover, fungi are known as a rich source of secondary metabolites. Despite these facts, the ecological role of many of these metabolites is still unknown and the chemical ecology of fungi has not been investigated systematically so far. This review intends to present examples of the various chemical interactions of fungi with other fungi, plants, bacteria and animals and to give an overview of the current knowledge of fungal chemical ecology.

  17. ERLN Chemical Focus Area

    EPA Pesticide Factsheets

    The Environmental Response Laboratory Network is able to provide environmental laboratory testing capability and capacity to meet EPA's responsibilities for surveillance of, response to, and recovery from incidents involving Chemical Warfare Agents.

  18. Chemical Burns: First Aid

    MedlinePlus

    ... tetanus booster is up to date. When to seek emergency care The person shows signs of shock, ... 222-1222 in the United States. If you seek emergency medical help, take the chemical container or ...

  19. Chemical Safety Programs.

    ERIC Educational Resources Information Center

    Shaw, Richard

    2000-01-01

    Discusses the need to enhance understanding of chemical safety in educational facilities that includes adequate staff training and drilling requirements. The question of what is considered proper training is addressed. (GR)

  20. Legendary Chemical Aphrodisiacs.

    ERIC Educational Resources Information Center

    Waddell, Thomas G.; And Others

    1980-01-01

    Presents a survey of the literature and a summary of information regarding aphrodisiacs. Chemical compounds are discussed as groups of plant natural products, animal natural products, and synthetic products. (CS)

  1. Soil Fumigant Chemicals

    EPA Pesticide Factsheets

    The main soil fumigant pesticide chemicals are chloropicrin, dazomet, 1,3-dichloropropene (telone), dimethyl disulfide (DMDS), metam sodium, metam potassium, and methyl bromide. Find label requirements, reregistration eligibility decisions (REDs), and more

  2. Chemical dependence - resources

    MedlinePlus

    Substance use - resources, Drug abuse - resources; Resources - chemical dependence ... National Institute on Drug Abuse -- www.drugabuse.gov Substance Abuse and Mental Health Services Administration -- www.samhsa.gov

  3. A bionics chemical synapse.

    PubMed

    Thanapitak, Surachoke; Toumazou, Christofer

    2013-06-01

    Implementation of the current mode CMOS circuit for chemical synapses (AMPA and NMDA receptors) with dynamic change of glutamate as the neurotransmitter input is presented in this paper. Additionally, circuit realisation for receptor GABA(A) and GABA(B) with an electrical signal which symbolises γ-Aminobutyric Acid (GABA) perturbation is introduced. The chemical sensor for glutamate sensing is the modified ISFET with enzyme (glutamate oxidase) immobilisation. The measured results from these biomimetics chemical synapse circuits closely match with the simulation result from the mathematical model. The total power consumption of the whole chip (four chemical synapse circuits and all auxiliary circuits) is 168.3 μW. The total chip area is 3 mm(2) in 0.35-μm AMS CMOS technology.

  4. SAM Chemical Methods Query

    EPA Pesticide Factsheets

    Laboratories measuring target chemical, radiochemical, pathogens, and biotoxin analytes in environmental samples can use this online query tool to identify analytical methods in EPA's Selected Analytical Methods for Environmental Remediation and Recovery

  5. Chemical Accident Prevention Publications

    EPA Pesticide Factsheets

    These include chemical safety alerts, emergency preparedness and prevention advisories, and topical backgrounders. Excess flow valves, protecting workers in ethylene oxide sterilization facilities, reactivity hazards, and delayed coker units are covered.

  6. Chemical Engineering at NASA

    NASA Technical Reports Server (NTRS)

    Collins, Jacob

    2008-01-01

    This viewgraph presentation is a review of the career paths for chemicals engineer at NASA (specifically NASA Johnson Space Center.) The author uses his personal experience and history as an example of the possible career options.

  7. Chemical warfare agents.

    PubMed

    Kuca, Kamil; Pohanka, Miroslav

    2010-01-01

    Chemical warfare agents are compounds of different chemical structures. Simple molecules such as chlorine as well as complex structures such as ricin belong to this group. Nerve agents, vesicants, incapacitating agents, blood agents, lung-damaging agents, riot-control agents and several toxins are among chemical warfare agents. Although the use of these compounds is strictly prohibited, the possible misuse by terrorist groups is a reality nowadays. Owing to this fact, knowledge of the basic properties of these substances is of a high importance. This chapter briefly introduces the separate groups of chemical warfare agents together with their members and the potential therapy that should be applied in case someone is intoxicated by these agents.

  8. Tobacco and chemicals (image)

    MedlinePlus

    ... carbon dioxide, carbon monoxide, propane, methane, acetone, hydrogen cyanide and various carcinogens. Other chemicals that are associated with chewing or sniffing tobacco include aniline, naphthalene, phenol, pyrene, tar, and 2- ...

  9. Chemical Bonds II

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    The continuation of a paper discussing chemical bonding from a bond energy viewpoint, with a number of examples of single and multiple bonds. (Part I appeared in volume 1 number 3, pages 16-23, February 1972.) (AL)

  10. Chemical Principles Exemplified

    ERIC Educational Resources Information Center

    Plumb, Robert C.

    1972-01-01

    Collection of two short descriptions of chemical principles seen in life situations: the autocatalytic reaction seen in the bombardier beetle, and molecular potential energy used for quick roasting of beef. Brief reference is also made to methanol lighters. (PS)

  11. Chemical Engineering Education Revisited.

    ERIC Educational Resources Information Center

    Theodore, Louis

    1978-01-01

    The opinion is presented that chemical engineering education seems to emphasize the professor's research and/or professional interests with little regard for the real needs of the student who intends to become a practicing engineer. (BB)

  12. Reflections on Chemical Equations.

    ERIC Educational Resources Information Center

    Gorman, Mel

    1981-01-01

    The issue of how much emphasis balancing chemical equations should have in an introductory chemistry course is discussed. The current heavy emphasis on finishing such equations is viewed as misplaced. (MP)

  13. The U.S. Chemical Industry, Foreign Chemical Industries

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1972

    1972-01-01

    This section of the annual report on the chemical industry provides data on the chemical production of Japan, West Germany, United Kingdom, Italy, and France, including the output of major chemical products in these nations. (PR)

  14. Quantum Chemical Calculations

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The current methods of quantum chemical calculations will be reviewed. The accent will be on the accuracy that can be achieved with these methods. The basis set requirements and computer resources for the various methods will be discussed. The utility of the methods will be illustrated with some examples, which include the calculation of accurate bond energies for SiF$_n$ and SiF$_n^+$ and the modeling of chemical data storage.

  15. Chemicals from Space

    NASA Technical Reports Server (NTRS)

    Lewis, Karen

    2007-01-01

    Except for Hydrogen, Helium, and Lithium (which were around from the beginning) all the chemicals that you learned about this year were made in stars. We really are made out of stardust! I'm going to bring you on a tour of the lives of stars to show you how all the chemicals in the Universe were made during different stages of a stars life.

  16. Computational Systems Chemical Biology

    PubMed Central

    Oprea, Tudor I.; May, Elebeoba E.; Leitão, Andrei; Tropsha, Alexander

    2013-01-01

    There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically-based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology, SCB (Oprea et al., 2007). The overarching goal of computational SCB is to develop tools for integrated chemical-biological data acquisition, filtering and processing, by taking into account relevant information related to interactions between proteins and small molecules, possible metabolic transformations of small molecules, as well as associated information related to genes, networks, small molecules and, where applicable, mutants and variants of those proteins. There is yet an unmet need to develop an integrated in silico pharmacology / systems biology continuum that embeds drug-target-clinical outcome (DTCO) triplets, a capability that is vital to the future of chemical biology, pharmacology and systems biology. Through the development of the SCB approach, scientists will be able to start addressing, in an integrated simulation environment, questions that make the best use of our ever-growing chemical and biological data repositories at the system-wide level. This chapter reviews some of the major research concepts and describes key components that constitute the emerging area of computational systems chemical biology. PMID:20838980

  17. Computational systems chemical biology.

    PubMed

    Oprea, Tudor I; May, Elebeoba E; Leitão, Andrei; Tropsha, Alexander

    2011-01-01

    There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology (SCB) (Nat Chem Biol 3: 447-450, 2007).The overarching goal of computational SCB is to develop tools for integrated chemical-biological data acquisition, filtering and processing, by taking into account relevant information related to interactions between proteins and small molecules, possible metabolic transformations of small molecules, as well as associated information related to genes, networks, small molecules, and, where applicable, mutants and variants of those proteins. There is yet an unmet need to develop an integrated in silico pharmacology/systems biology continuum that embeds drug-target-clinical outcome (DTCO) triplets, a capability that is vital to the future of chemical biology, pharmacology, and systems biology. Through the development of the SCB approach, scientists will be able to start addressing, in an integrated simulation environment, questions that make the best use of our ever-growing chemical and biological data repositories at the system-wide level. This chapter reviews some of the major research concepts and describes key components that constitute the emerging area of computational systems chemical biology.

  18. Chemical Demilitarization Assembled Chemical Weapons Alternatives (Chem Demil-ACWA)

    DTIC Science & Technology

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-243 Chemical Demilitarization-Assembled Chemical Weapons Alternatives (Chem Demil-ACWA) As...Date Assigned: December 19, 2010 Program Information Program Name Chemical Demilitarization-Assembled Chemical Weapons Alternatives (Chem Demil...2012 Chem Demil-ACWA December 2015 SAR March 23, 2016 16:29:37 UNCLASSIFIED 5 Mission and Description Chemical Demilitarization-Assembled Chemical

  19. Evolution was chemically constrained.

    PubMed

    Williams, R J P; Fraústo Da Silva, J J R

    2003-02-07

    The objective of this paper is to present a systems view of the major features of biological evolution based upon changes in internal chemistry and uses of cellular space, both of which it will be stated were dependent on the changing chemical environment. The account concerns the major developments from prokaryotes to eukaryotes, to multi-cellular organisms, to animals with nervous systems and a brain, and finally to human beings and their uses of chemical elements in space outside themselves. It will be stated that the changes were in an inevitable progression, and were not just due to blind chance, so that "random searching" by a coded system to give species had a fixed overall route. The chemical sequence is from a reducing to an ever-increasingly oxidizing environment, while organisms retained reduced chemicals. The process was furthered recently by human beings who have also increased the range of reduced products trapped on Earth in novel forms. All the developments are brought about from the nature of the chemicals which organisms accumulate using the environment and its changes. The relationship to the manner in which particular species (gene sequences) were coincidentally changed, the molecular view of evolution, is left for additional examination. There is a further issue in that the changes of the chemistry of the environment developed largely at equilibrium due to the relatively fast reactions there of the available inorganic chemicals. Inside cells, some of these same chemicals also came to equilibrium within compounds. All such equilibria reduced the variance (degrees of freedom) of the total environmental/biological system and its possible development. However, the more sophisticated organic chemistry, almost totally inside cells until humans evolved, is kinetically controlled and limited by the demands of cellular reduction necessary to produce essential chemicals and by the availability of certain elements and energy. Hence the variability of

  20. How EPA Assesses Chemical Safety

    EPA Pesticide Factsheets

    EPA's existing chemicals programs address pollution prevention, risk assessment, hazard and exposure assessment and/or characterization, and risk management for chemicals substances in commercial use.

  1. Current Chemical Risk Reduction Activities

    EPA Pesticide Factsheets

    EPA's existing chemicals programs address pollution prevention, risk assessment, hazard and exposure assessment and/or characterization, and risk management for chemicals substances in commercial use.

  2. Chemical Equilibrium And Transport (CET)

    NASA Technical Reports Server (NTRS)

    Mcbride, B. J.

    1991-01-01

    Powerful, machine-independent program calculates theoretical thermodynamic properties of chemical systems. Aids in design of compressors, turbines, engines, heat exchangers, and chemical processing equipment.

  3. Biological and Chemical Security

    SciTech Connect

    Fitch, P J

    2002-12-19

    The LLNL Chemical & Biological National Security Program (CBNP) provides science, technology and integrated systems for chemical and biological security. Our approach is to develop and field advanced strategies that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical or biological weapons. Recent events show the importance of civilian defense against terrorism. The 1995 nerve gas attack in Tokyo's subway served to catalyze and focus the early LLNL program on civilian counter terrorism. In the same year, LLNL began CBNP using Laboratory-Directed R&D investments and a focus on biodetection. The Nunn-Lugar-Domenici Defense Against Weapons of Mass Destruction Act, passed in 1996, initiated a number of U.S. nonproliferation and counter-terrorism programs including the DOE (now NNSA) Chemical and Biological Nonproliferation Program (also known as CBNP). In 2002, the Department of Homeland Security was formed. The NNSA CBNP and many of the LLNL CBNP activities are being transferred as the new Department becomes operational. LLNL has a long history in national security including nonproliferation of weapons of mass destruction. In biology, LLNL had a key role in starting and implementing the Human Genome Project and, more recently, the Microbial Genome Program. LLNL has over 1,000 scientists and engineers with relevant expertise in biology, chemistry, decontamination, instrumentation, microtechnologies, atmospheric modeling, and field experimentation. Over 150 LLNL scientists and engineers work full time on chemical and biological national security projects.

  4. [Poisonous chemicals and urolithiasis].

    PubMed

    Tynaliev, M T

    1993-01-01

    For the last 30 years urolithiasis incidence in Kirghizia has been growing. Its prevalence is the highest in Chu and Osh rural areas (89%) where farmers widely use toxic insecticides. Urban population develop the disease more often (63%), especially employees (57.7%) versus workers (27.7%). Urolithiasis occurs in workers 8 times more frequently than in farmers. Food products contain insecticides in quantities much higher than MAC. The contamination concerns fruit and vegetables in a lesser and meat, milk products in greater degrees. In renal tissue, blood, urine of urolithiasis patients concentrations of the chemicals were increased 4 times against the control samples. In renal tissue and fat of urolithiasis animals nephrotoxic insecticides levels surpassed those in the controls 2-3 times. Uroliths contain chemicals in great concentrations also. Basing on the conformity of geography of insecticides us a ge with urolithiasis epidemiological data, high concentrations of the chemicals in food and biological objects, frequent occurrence of recurrent urolithiasis in patients known to acquire high chemicals levels in renal tissue and urine, it is inferred that toxic chemicals are involved in nephrolithiasis genesis by tubular impairment.

  5. INTEGRATED CHEMICAL INFORMATION TECHNOLOGIES ...

    EPA Pesticide Factsheets

    A central regulatory mandate of the Environmental Protection Agency, spanning many Program Offices and issues, is to assess the potential health and environmental risks of large numbers of chemicals released into the environment, often in the absence of relevant test data. Models for predicting potential adverse effects of chemicals based primarily on chemical structure play a central role in prioritization and screening strategies yet are highly dependent and conditional upon the data used for developing such models. Hence, limits on data quantity, quality, and availability are considered by many to be the largest hurdles to improving prediction models in diverse areas of toxicology. Generation of new toxicity data for additional chemicals and endpoints, development of new high-throughput, mechanistically relevant bioassays, and increased generation of genomics and proteomics data that can clarify relevant mechanisms will all play important roles in improving future SAR prediction models. The potential for much greater immediate gains, across large domains of chemical and toxicity space, comes from maximizing the ability to mine and model useful information from existing toxicity data, data that represent huge past investment in research and testing expenditures. In addition, the ability to place newer “omics” data, data that potentially span many possible domains of toxicological effects, in the broader context of historical data is the means for opti

  6. Chemically Powered Nanomotors

    NASA Astrophysics Data System (ADS)

    Kapral, Raymond

    2007-03-01

    Molecular motors play important roles in transport in biological systems. These molecular machines are powered by chemical energy and operate in the regime of low Reynolds number hydrodynamics. Recently a class of simple inorganic molecular motors has been constructed and studied experimentally [1,2]. These motors are bimetallic rods, one end of which is chemically active. The talk will describe simple mesoscopic models for the motion of such nanomotors. The motor consists of two linked spheres, one of which catalyzes the conversion between two chemical species. The chemical species interact differently with the the two spheres in the dimer. The nano-dimer motor is solvated by a molecules treated at a mesoscopic level whose evolution is governed by multi-particle collision dynamics. The dynamics conserves mass, momentum and energy so that coupling between the nanomotor and the hydrodynamic modes of the solvent is treated correctly. The simulations allow one to explore the mechanisms of the chemically powered motion and the effects of fluctuations on the motor dynamics. [1] W. F. Paxton, et al., ``Catalytic Nanomotors: Autonomous Movement of Striped Nanorods,'' J. Am. Chem. Soc. (JACS), 126 (41), 13424 (2004). [2] S. Fournier-Bidoz, et al. ``Synthetic Self-Propelled Nanorotors,'' Chem. Commun., (4), 441 (2005).

  7. Groundwater chemicals desk reference

    SciTech Connect

    Montgomery, J.H.; Welkom, L.M.

    1990-01-01

    Information is compiled on more than 135 compounds that may be groundwater pollutants. The compounds profiled include all the Priority Pollutants promulgated by the US EPA under the Clean Water Act (CWA) of 1977. Many of these priority pollutants were included among the Target Compounds promulgated by the EPA under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in 1980 and the Superfund Amendments and Reauthorization Act (SARA) of 1986. All chemicals described in the book are classified as priority pollutants and/or target compounds. For each chemical, the following information is given: (1) synonyms; (2) structural formula; (3) CAS Registry number; (4) DOT designation; (5) empirical formula; (6) formula weight; (7) RETCS number; (8) physical and chemical properties; (9) fire hazards; (10) health hazard data; and (11) manufacturing data and/or selected manufacturers.

  8. Translated chemical reaction networks.

    PubMed

    Johnston, Matthew D

    2014-05-01

    Many biochemical and industrial applications involve complicated networks of simultaneously occurring chemical reactions. Under the assumption of mass action kinetics, the dynamics of these chemical reaction networks are governed by systems of polynomial ordinary differential equations. The steady states of these mass action systems have been analyzed via a variety of techniques, including stoichiometric network analysis, deficiency theory, and algebraic techniques (e.g., Gröbner bases). In this paper, we present a novel method for characterizing the steady states of mass action systems. Our method explicitly links a network's capacity to permit a particular class of steady states, called toric steady states, to topological properties of a generalized network called a translated chemical reaction network. These networks share their reaction vectors with their source network but are permitted to have different complex stoichiometries and different network topologies. We apply the results to examples drawn from the biochemical literature.

  9. Chemical Kinetics Database

    National Institute of Standards and Technology Data Gateway

    SRD 17 NIST Chemical Kinetics Database (Web, free access)   The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.

  10. Micromachined chemical jet dispenser

    DOEpatents

    Swierkowski, Steve P.

    1999-03-02

    A dispenser for chemical fluid samples that need to be precisely ejected in size, location, and time. The dispenser is a micro-electro-mechanical systems (MEMS) device fabricated in a bonded silicon wafer and a substrate, such as glass or silicon, using integrated circuit-like fabrication technology which is amenable to mass production. The dispensing is actuated by ultrasonic transducers that efficiently produce a pressure wave in capillaries that contain the chemicals. The 10-200 .mu.m diameter capillaries can be arranged to focus in one spot or may be arranged in a larger dense linear array (.about.200 capillaries). The dispenser is analogous to some ink jet print heads for computer printers but the fluid is not heated, thus not damaging certain samples. Major applications are in biological sample handling and in analytical chemical procedures such as environmental sample analysis, medical lab analysis, or molecular biology chemistry experiments.

  11. Micromachined chemical jet dispenser

    DOEpatents

    Swierkowski, S.P.

    1999-03-02

    A dispenser is disclosed for chemical fluid samples that need to be precisely ejected in size, location, and time. The dispenser is a micro-electro-mechanical systems (MEMS) device fabricated in a bonded silicon wafer and a substrate, such as glass or silicon, using integrated circuit-like fabrication technology which is amenable to mass production. The dispensing is actuated by ultrasonic transducers that efficiently produce a pressure wave in capillaries that contain the chemicals. The 10-200 {micro}m diameter capillaries can be arranged to focus in one spot or may be arranged in a larger dense linear array (ca. 200 capillaries). The dispenser is analogous to some ink jet print heads for computer printers but the fluid is not heated, thus not damaging certain samples. Major applications are in biological sample handling and in analytical chemical procedures such as environmental sample analysis, medical lab analysis, or molecular biology chemistry experiments. 4 figs.

  12. Advanced Chemical Propulsion Study

    NASA Technical Reports Server (NTRS)

    Woodcock, Gordon; Byers, Dave; Alexander, Leslie A.; Krebsbach, Al

    2004-01-01

    A study was performed of advanced chemical propulsion technology application to space science (Code S) missions. The purpose was to begin the process of selecting chemical propulsion technology advancement activities that would provide greatest benefits to Code S missions. Several missions were selected from Code S planning data, and a range of advanced chemical propulsion options was analyzed to assess capabilities and benefits re these missions. Selected beneficial applications were found for higher-performing bipropellants, gelled propellants, and cryogenic propellants. Technology advancement recommendations included cryocoolers and small turbopump engines for cryogenic propellants; space storable propellants such as LOX-hydrazine; and advanced monopropellants. It was noted that fluorine-bearing oxidizers offer performance gains over more benign oxidizers. Potential benefits were observed for gelled propellants that could be allowed to freeze, then thawed for use.

  13. Chemical Domino Demonstration

    NASA Astrophysics Data System (ADS)

    Alexander, M. Dale

    1998-04-01

    The Chemical Domino Demonstration is both educational and entertaining. It provides an excellent means for a review of chemical concepts at the conclusion of a general chemistry course. This demonstration consists of a number of different chemical reactions occurring in sequence in a Rube Goldberg-type apparatus. These reactions include the reduction of water by an active metal, the oxidation of a moderately active metal by an acid, reduction of metallic ions by a metal of greater activity, acid-base neutralization reactions in solution monitored with indicators, a gas-phase acid-base neutralization reaction, decomposition of a compound, precipitation of an insoluble salt, substitution reactions of coordination complexes, and pyrotechnic oxidation-reduction reactions including a hypergolic oxidation-reduction reaction, an intramolecular oxidation-reduction reaction, and the combustion of a flammable gas.

  14. Idaho Chemical Processing Plant safety document ICPP hazardous chemical evaluation

    SciTech Connect

    Harwood, B.J.

    1993-01-01

    This report presents the results of a hazardous chemical evaluation performed for the Idaho Chemical Processing Plant (ICPP). ICPP tracks chemicals on a computerized database, Haz Track, that contains roughly 2000 individual chemicals. The database contains information about each chemical, such as its form (solid, liquid, or gas); quantity, either in weight or volume; and its location. The Haz Track database was used as the primary starting point for the chemical evaluation presented in this report. The chemical data and results presented here are not intended to provide limits, but to provide a starting point for nonradiological hazards analysis.

  15. Chemical sensing in Drosophila.

    PubMed

    Benton, Richard

    2008-08-01

    Chemical sensing begins when peripheral receptor proteins recognise specific environmental stimuli and translate them into spatial and temporal patterns of sensory neuron activity. The chemosensory system of the fruit fly, Drosophila melanogaster, has become a dominant model to understand this process, through its accessibility to a powerful combination of molecular, genetic and electrophysiological analysis. Recent results have revealed many surprises in the biology of peripheral chemosensation in Drosophila, including novel structural and signalling properties of the insect odorant receptors (ORs), combinatorial mechanisms of chemical recognition by the gustatory receptors (GRs), and the implication of Transient Receptor Potential (TRP) ion channels as a novel class of chemosensory receptors.

  16. Cyanobacterial chemical production.

    PubMed

    Case, Anna E; Atsumi, Shota

    2016-08-10

    The increase in global temperatures caused by rising CO2 levels necessitates the development of alternative sources of fuel and chemicals. One appealing alternative that has been receiving increased attention in recent years is the photosynthetic conversion of atmospheric CO2 to biofuels and chemical products using genetically engineered cyanobacteria. This can help to not only provide an alternate "greener" source for some of the most popular petroleum based products but it can also help to reduce atmospheric CO2. Utilizing cyanobacteria rather than plants allows for reduced land requirements and reduces competition with food crops. This review discusses advancements in the field since 2012 with a particular emphasis on production of hydrocarbons.

  17. Laboratory Safety and Chemical Hazards.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 1983

    1983-01-01

    Toxicology/chemical hazards, safety policy, legal responsibilities, adequacy of ventilation, chemical storage, evaluating experimental hazards, waste disposal, and laws governing chemical safety were among topics discussed in 10 papers presented at the Seventh Biennial Conference on Chemical Education (Stillwater, Oklahoma 1982). Several topics…

  18. Common Chemicals around the House.

    ERIC Educational Resources Information Center

    Katz, David A., Comp.; O'Brien, Thomas, Comp.

    1991-01-01

    Lists 46 household chemicals readily available at local stores by common name, chemical name, chemical formula, and typical commercial source. Suggests that school budgetary constraints can be eased by this practice and that students can become more chemically literate as consumers. (JJK)

  19. Environmental Chemicals in Breast Milk

    EPA Science Inventory

    Most of the information available on environmental chemicals in breast milk is focused on persistent, lipophilic chemicals; the database on levels of these chemicals has expanded substantially since the 1950s. Currently, various types of chemicals are measured in breast milk and ...

  20. Chemical Design of Elastomers

    DTIC Science & Technology

    1987-05-19

    TMTD), N-oxydiethylene-2- benzothiazole sulfenamide (MOR) and N-cyclohexyl- benzothiazole -2-sulfenamide (CBS). The chemical structures of the accelerators...disulfide CBS - N-cyclohexyl- benzothiazole -2-sulfenamide MOR - N-oxydiethylene- benzothiazole -2-sulfenamide AO - Antioxidant SA - Stearic acid 5.5. Results

  1. Making a Chemical Rainbow

    ERIC Educational Resources Information Center

    Angelin, Marcus; Ramstrom, Olof

    2010-01-01

    In this laboratory experiment, high school students are challenged to prepare a six-layered chemical "rainbow" in a test tube. Students start with six unknown, colorless liquids and six pigments ranging from violet to red. The experiment is problem based and forces the students to apply their knowledge of solubility and density and combine it with…

  2. Chemical Aspects of Dentistry.

    ERIC Educational Resources Information Center

    Helfman, Murry

    1982-01-01

    Dental caries (tooth decay) and periodontal (gum) disease are treated/prevented by procedures utilizing chemical expertise. Procedures and suggestions on how they might be incorporated into the high school chemistry curriculum are described. Specific topics discussed include dental caries, fluoride, diet, tooth decay prevention, silver amalgan,…

  3. Electro-chemical grinding

    NASA Technical Reports Server (NTRS)

    Feagans, P. L.

    1972-01-01

    Electro-chemical grinding technique has rotation speed control, constant feed rates, and contour control. Hypersonic engine parts of nickel alloys can be almost 100% machined, keeping tool pressure at virtual zero. Technique eliminates galling and permits constant surface finish and burr-free interrupted cutting.

  4. Risks and Chemical Substances.

    ERIC Educational Resources Information Center

    Blumberg, Avrom A.

    1994-01-01

    Examines exposure to chemicals within the home and three important ways in which hazardous substances can be identified and evaluated. Suggests a rational picture of human health risks and contains an introductory discussion of reasons for exposure, epidemiology, cancer causes and patterns, animal testing, toxins, and risk. (LZ)

  5. Advanced Chemical Propulsion

    NASA Technical Reports Server (NTRS)

    Alexander, Leslie, Jr.

    2006-01-01

    Advanced Chemical Propulsion (ACP) provides near-term incremental improvements in propulsion system performance and/or cost. It is an evolutionary approach to technology development that produces useful products along the way to meet increasingly more demanding mission requirements while focusing on improving payload mass fraction to yield greater science capability. Current activities are focused on two areas: chemical propulsion component, subsystem, and manufacturing technologies that offer measurable system level benefits; and the evaluation of high-energy storable propellants with enhanced performance for in-space application. To prioritize candidate propulsion technology alternatives, a variety of propulsion/mission analyses and trades have been conducted for SMD missions to yield sufficient data for investment planning. They include: the Advanced Chemical Propulsion Assessment; an Advanced Chemical Propulsion System Model; a LOx-LH2 small pumps conceptual design; a space storables propellant study; a spacecraft cryogenic propulsion study; an advanced pressurization and mixture ratio control study; and a pump-fed vs. pressure-fed study.

  6. Chemical reacting flows

    NASA Astrophysics Data System (ADS)

    Mularz, Edward J.; Sockol, Peter M.

    1990-02-01

    Future aerospace propulsion concepts involve the combustion of liquid or gaseous fuels in a highly turbulent internal airstream. Accurate predictive computer codes which can simulate the fluid mechanics, chemistry, and turbulence-combustion interaction of these chemical reacting flows will be a new tool that is needed in the design of these future propulsion concepts. Experimental and code development research is being performed at LeRC to better understand chemical reacting flows with the long-term goal of establishing these reliable computer codes. Our approach to understand chemical reacting flows is to look at separate, more simple parts of this complex phenomenon as well as to study the full turbulent reacting flow process. As a result, we are engaged in research on the fluid mechanics associated with chemical reacting flows. We are also studying the chemistry of fuel-air combustion. Finally, we are investigating the phenomenon of turbulence-combustion interaction. Research, both experimental and analytical, is highlighted in each of these three major areas.

  7. Chemical Principles Exemplified

    ERIC Educational Resources Information Center

    Plumb, Robert C.

    1970-01-01

    This is the first of a new series of brief ancedotes about materials and phenomena which exemplify chemical principles. Examples include (1) the sea-lab experiment illustrating principles of the kinetic theory of gases, (2) snow-making machines illustrating principles of thermodynamics in gas expansions and phase changes, and (3) sunglasses that…

  8. NETL - Chemical Looping Reactor

    SciTech Connect

    2013-07-24

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  9. Chemical calcium indicators.

    PubMed

    Paredes, R Madelaine; Etzler, Julie C; Watts, Lora Talley; Zheng, Wei; Lechleiter, James D

    2008-11-01

    Our understanding of the underlying mechanisms of Ca2+ signaling as well as our appreciation for its ubiquitous role in cellular processes has been rapidly advanced, in large part, due to the development of fluorescent Ca2+ indicators. In this chapter, we discuss some of the most common chemical Ca2+ indicators that are widely used for the investigation of intracellular Ca2+ signaling. Advantages, limitations and relevant procedures will be presented for each dye including their spectral qualities, dissociation constants, chemical forms, loading methods and equipment for optimal imaging. Chemical indicators now available allow for intracellular Ca2+ detection over a very large range (<50 nM to >50 microM). High affinity indicators can be used to quantify Ca2+ levels in the cytosol while lower affinity indicators can be optimized for measuring Ca2+ in subcellular compartments with higher concentrations. Indicators can be classified into either single wavelength or ratiometric dyes. Both classes require specific lasers, filters, and/or detection methods that are dependent upon their spectral properties and both classes have advantages and limitations. Single wavelength indicators are generally very bright and optimal for Ca2+ detection when more than one fluorophore is being imaged. Ratiometric indicators can be calibrated very precisely and they minimize the most common problems associated with chemical Ca2+ indicators including uneven dye loading, leakage, photobleaching, and changes in cell volume. Recent technical advances that permit in vivo Ca2+ measurements will also be discussed.

  10. Chemically Reacting Turbulent Flow.

    DTIC Science & Technology

    1987-04-14

    two stages of gen I tubes equipped with P-47 phosphor screens The detector chosen for the camera was a Reticon RL128S* line detectoI- .,hich consists...the Stud’, of Turbulent Mixing," William M. Pitts, Nuclear Engineering Seminar of the Department of Chemical and Nuclear Engineering, University of

  11. NETL - Chemical Looping Reactor

    ScienceCinema

    None

    2016-07-12

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  12. Epigenetics and environmental chemicals

    PubMed Central

    Baccarelli, A; Bollati, V.

    2011-01-01

    Purpose of the review Epigenetics investigates heritable changes in gene expression occurring without changes in DNA sequence. Several epigenetic mechanisms, including DNA methylation, histone modifications, and microRNA (miRNA) expression, can change genome function under exogenous influence. Here, we review current evidence indicating that epigenetic alterations mediate toxicity from environmental chemicals. Recent findings In-vitro, animal, and human investigations have identified several classes of environmental chemicals that modify epigenetic marks, including metals (cadmium, arsenic, nickel, chromium, methylmercury), peroxisome proliferators (trichloroethylene, dichloroacetic acid, trichloroacetic acid), air pollutants (particulate matter, black carbon, benzene), and endocrine-disrupting/reproductive toxicants (diethylstilbestrol, bisphenol A, persistent organic pollutants, dioxin). Most studies conducted so far have been centered on DNA methylation, whereas only a few investigations have studied environmental chemicals in relation to histone modications and miRNA. Summary For several exposures, it has been proved that chemicals can alter epigenetic marks and that the same or similar epigenetic alterations can be found in patients with the disease of concern or in diseased tissues. Future prospective investigations are needed to determine whether exposed subjects develop epigenetic alterations over time and, in turn, which such alterations increase the risk of disease. Also, further research is needed to determine whether environmental epigenetic changes are transmitted transgenerationally. PMID:19663042

  13. Chemical Bonds I

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)

  14. Chemical hygiene plan

    SciTech Connect

    Not Available

    1994-09-01

    This plan was written to administer and monitor safety measures and chemical hygiene principles in the TAC Uranium Mill Tailing Remedial Action Project sample preparation facility in Albuquerque, New Mexico. It applies to toxic and/or hazardous materials to radioactive materials.

  15. Chemical reacting flows

    NASA Technical Reports Server (NTRS)

    Mularz, Edward J.; Sockol, Peter M.

    1990-01-01

    Future aerospace propulsion concepts involve the combustion of liquid or gaseous fuels in a highly turbulent internal airstream. Accurate predictive computer codes which can simulate the fluid mechanics, chemistry, and turbulence-combustion interaction of these chemical reacting flows will be a new tool that is needed in the design of these future propulsion concepts. Experimental and code development research is being performed at LeRC to better understand chemical reacting flows with the long-term goal of establishing these reliable computer codes. Our approach to understand chemical reacting flows is to look at separate, more simple parts of this complex phenomenon as well as to study the full turbulent reacting flow process. As a result, we are engaged in research on the fluid mechanics associated with chemical reacting flows. We are also studying the chemistry of fuel-air combustion. Finally, we are investigating the phenomenon of turbulence-combustion interaction. Research, both experimental and analytical, is highlighted in each of these three major areas.

  16. Chemical reacting flows

    NASA Technical Reports Server (NTRS)

    Mularz, Edward J.; Sockol, Peter M.

    1987-01-01

    Future aerospace propulsion concepts involve the combination of liquid or gaseous fuels in a highly turbulent internal air stream. Accurate predictive computer codes which can simulate the fluid mechanics, chemistry, and turbulence combustion interaction of these chemical reacting flows will be a new tool that is needed in the design of these future propulsion concepts. Experimental and code development research is being performed at Lewis to better understand chemical reacting flows with the long term goal of establishing these reliable computer codes. The approach to understanding chemical reacting flows is to look at separate simple parts of this complex phenomena as well as to study the full turbulent reacting flow process. As a result research on the fluid mechanics associated with chemical reacting flows was initiated. The chemistry of fuel-air combustion is also being studied. Finally, the phenomena of turbulence-combustion interaction is being investigated. This presentation will highlight research, both experimental and analytical, in each of these three major areas.

  17. Accurate quantum chemical calculations

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1989-01-01

    An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.

  18. Identifying Chemical Groups for Biomonitoring

    PubMed Central

    Krowech, Gail; Hoover, Sara; Plummer, Laurel; Sandy, Martha; Zeise, Lauren; Solomon, Gina

    2016-01-01

    Summary: Regulatory agencies face daunting challenges identifying emerging chemical hazards because of the large number of chemicals in commerce and limited data on exposure and toxicology. Evaluating one chemical at a time is inefficient and can lead to replacement with uncharacterized chemicals or chemicals with structural features already linked to toxicity. The Office of Environmental Health Hazard Assessment (OEHHA) has developed a process for constructing and assessing chemical groups for potential biomonitoring in California. We screen for chemicals with significant exposure potential and propose possible chemical groups, based on structure and function. To support formal consideration of these groups by Biomonitoring California’s Scientific Guidance Panel, we conduct a detailed review of exposure and toxicity data and examine the likelihood of detection in biological samples. To date, 12 chemical groups have been constructed and added to the pool of chemicals that can be selected for Biomonitoring California studies, including p,p´-bisphenols, brominated and chlorinated organic compounds used as flame retardants, non-halogenated aromatic phosphates, and synthetic polycyclic musks. Evaluating chemical groups, rather than individual chemicals, is an efficient way to respond to shifts in chemical use and the emergence of new chemicals. This strategy can enable earlier identification of important chemicals for monitoring and intervention. PMID:27905275

  19. Chemical Debridement of Burns

    PubMed Central

    Levenson, Stanley M.; Kan, Dorinne; Gruber, Charles; Crowley, Leo V.; Lent, Richard; Watford, Alvin; Seifter, Eli

    1974-01-01

    The development of effective, non-toxic (local and systemic) methods for the rapid chemical (enzymatic and non-enzymatic) debridement of third degree burns would dramatically reduce the morbidity and mortality of severely burned patients. Sepsis is still the major cause of death of patients with extensive deep burns. The removal of the devitalized tissue, without damage to unburned skin or skin only partially injured by burning, and in ways which would permit immediate (or very prompt) skin grafting, would lessen substantially the problems of sepsis, speed convalescence and the return of these individuals to society as effective human beings, and would decrease deaths. The usefulness and limitations of surgical excision for patients with extensive third degree burns are discussed. Chemical debridement lends itself to complementary use with surgical excision and has the potential advantage over surgical excision in not requiring anesthesia or a formal surgical operation. The authors' work with the chemical debridement of burns, in particular the use of Bromelain, indicates that this approach will likely achieve clinical usefulness. The experimental studies indicate that rapid controlled debridement, with minimal local and systemic toxicity, is possible, and that effective chemotherapeutic agents may be combined with the Bromelain without either interfering with the actions of the other. The authors believe that rapid (hours) debridement accomplished by the combined use of chemical debriding and chemotherapeutic agents will obviate the possibility of any increase in infection, caused by the use of chemical agents for debridement, as reported for Paraenzyme21 and Travase.39,48 It is possible that the short term use of systemic antibiotics begun just before and continued during, and for a short time after, the rapid chemical debridement may prove useful for the prevention of infection, as appears to be the case for abdominal operations of the clean-contaminated and

  20. Chemical Modification of Polysaccharides

    PubMed Central

    Cumpstey, Ian

    2013-01-01

    This review covers methods for modifying the structures of polysaccharides. The introduction of hydrophobic, acidic, basic, or other functionality into polysaccharide structures can alter the properties of materials based on these substances. The development of chemical methods to achieve this aim is an ongoing area of research that is expected to become more important as the emphasis on using renewable starting materials and sustainable processes increases in the future. The methods covered in this review include ester and ether formation using saccharide oxygen nucleophiles, including enzymatic reactions and aspects of regioselectivity; the introduction of heteroatomic nucleophiles into polysaccharide chains; the oxidation of polysaccharides, including oxidative glycol cleavage, chemical oxidation of primary alcohols to carboxylic acids, and enzymatic oxidation of primary alcohols to aldehydes; reactions of uronic-acid-based polysaccharides; nucleophilic reactions of the amines of chitosan; and the formation of unsaturated polysaccharide derivatives. PMID:24151557

  1. Cooee bitumen: Chemical aging

    NASA Astrophysics Data System (ADS)

    Lemarchand, Claire A.; Schrøder, Thomas B.; Dyre, Jeppe C.; Hansen, Jesper S.

    2013-09-01

    We study chemical aging in "Cooee bitumen" using molecular dynamic simulations. This model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: "2 resins → 1 asphaltene." Molecular dynamic simulations of four bitumen compositions, obtained by a repeated application of the aging reaction, are performed. The stress autocorrelation function, the fluid structure, the rotational dynamics of the plane aromatic molecules, and the diffusivity of each molecule are determined for the four different compositions. The aging reaction causes a significant dynamics slowdown, which is correlated to the aggregation of asphaltene molecules in larger and dynamically slower nanoaggregates. Finally, a detailed description of the role of each molecule types in the aggregation and aging processes is given.

  2. Biocatalysis for biobased chemicals.

    PubMed

    de Regil, Rubén; Sandoval, Georgina

    2013-10-17

    The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme's own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis.

  3. Chemical Engineering in Space

    NASA Technical Reports Server (NTRS)

    Lobmeyer, Dennis A.; Meneghelli, Barry; Steinrock, Todd (Technical Monitor)

    2001-01-01

    The aerospace industry has long been perceived as the domain of both physicists and mechanical engineers. This perception has endured even though the primary method of providing the thrust necessary to launch a rocket into space is chemical in nature. The chemical engineering and chemistry personnel behind the systems that provide access to space have labored in the shadows of the physicists and mechanical engineers. As exploration into the cosmos moves farther away from Earth, there is a very distinct need for new chemical processes to help provide the means for advanced space exploration. The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit. As we move away from Earth, there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the chemical propulsion agents. It is with great care and significant cost that gaseous compounds such as hydrogen and oxygen are liquefied and become dense enough to use for rocket fuel. These low-temperature liquids fall within a specialty area known as cryogenics. Cryogenics, the science and art of producing cold operating conditions for use on Earth, in orbit, or on some other nonterrestrial body, has become increasingly important to our ability to travel within our solar system. The production of cryogenic fuels and the long-term storage of these fluids are necessary for travel. As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a round-trip. The cost and the size of these expeditions are extreme at best. If we take everything necessary for our survival for the round-trip, we invalidate any chance of travel in the near future. As with the early explorers on Earth, we need to harvest much of our energy and our life support from the celestial bodies. The in situ production of these energy

  4. Organic chemical evolution

    NASA Technical Reports Server (NTRS)

    Chang, S.

    1981-01-01

    The course of organic chemical evolution preceding the emergence of life on earth is discussed based on evidence of processes occurring in interstellar space, the solar system and the primitive earth. Following a brief review of the equilibrium condensation model for the origin and evolution of the solar system, consideration is given to the nature and organic chemistry of interstellar clouds, comets, Jupiter, meteorites, Venus and Mars, and the prebiotic earth. Major issues to be resolved in the study of organic chemical evolution on earth are identified regarding condensation and accretion in the solar nebula, early geological evolution, the origin and evolution of the atmosphere, organic production rates, organic-inorganic interactions, environmental fluctuations, phase separation and molecular selectivity.

  5. Chemical aerosol Raman detector

    NASA Astrophysics Data System (ADS)

    Aggarwal, R. L.; Farrar, L. W.; Di Cecca, S.; Amin, M.; Perkins, B. G.; Clark, M. L.; Jeys, T. H.; Sickenberger, D. W.; D'Amico, F. M.; Emmons, E. D.; Christesen, S. D.; Kreis, R. J.; Kilper, G. K.

    2017-03-01

    A sensitive chemical aerosol Raman detector (CARD) has been developed for the trace detection and identification of chemical particles in the ambient atmosphere. CARD includes an improved aerosol concentrator with a concentration factor of about 40 and a CCD camera for improved detection sensitivity. Aerosolized isovanillin, which is relatively safe, has been used to characterize the performance of the CARD. The limit of detection (SNR = 10) for isovanillin in 15 s has been determined to be 1.6 pg/cm3, which corresponds to 6.3 × 109 molecules/cm3 or 0.26 ppb. While less sensitive, CARD can also detect gases. This paper provides a more detailed description of the CARD hardware and detection algorithm than has previously been published.

  6. Biocatalysis for Biobased Chemicals

    PubMed Central

    de Regil, Rubén; Sandoval, Georgina

    2013-01-01

    The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme’s own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis. PMID:24970192

  7. Interactive chemical reactivity exploration.

    PubMed

    Haag, Moritz P; Vaucher, Alain C; Bosson, Maël; Redon, Stéphane; Reiher, Markus

    2014-10-20

    Elucidating chemical reactivity in complex molecular assemblies of a few hundred atoms is, despite the remarkable progress in quantum chemistry, still a major challenge. Black-box search methods to find intermediates and transition-state structures might fail in such situations because of the high-dimensionality of the potential energy surface. Here, we propose the concept of interactive chemical reactivity exploration to effectively introduce the chemist's intuition into the search process. We employ a haptic pointer device with force feedback to allow the operator the direct manipulation of structures in three dimensions along with simultaneous perception of the quantum mechanical response upon structure modification as forces. We elaborate on the details of how such an interactive exploration should proceed and which technical difficulties need to be overcome. All reactivity-exploration concepts developed for this purpose have been implemented in the samson programming environment.

  8. Chemicals in the Environment

    PubMed Central

    Rudd, Robert L.

    1970-01-01

    Synthetic chemicals are now being incorporated into the earth's ecosystems at a rate and in such manners as to alarm environmentalists. These chemicals are the uncontrolled waste products of a technological society. Most prominent among them at the present time are organochlorine, organomercurial and lead compounds. Persistent members of these groups disperse in water, air and animal tissues. Also they have the capacity for concentration in animal food chains, thereby reversing the historical expectation of the dilution and degradation of wastes. Examples of damage from environmental residues to man are at this stage speculative but documentation from effects on wild species is abundant. Already several species of birds seem on their way to extinction. These wild species constitute a gratuitous monitoring system which already has signaled clear warnings for the welfare of man. PMID:5485230

  9. [Chemical risk in farming].

    PubMed

    Moretto, Angelo

    2013-01-01

    The most important chemical risks in agriculture are plant protection products. Exposure evaluation in agriculture is not an easy task and cannot be carried out with the tools and methodologies of industrial exposures. However, toxicological studies on plant protection products, that are compulsory, provide a lot of useful information for actual risk assessment. Exposure evaluation can be carried out on the basis of exposure models and on semiquantitative measures based on the observation of the activity as it is carried our by the farmer. It is therefore possible to develop risk profiles that can guide exposure evaluation and health surveillance. Concentrated animal feeding operations are associated with several chemical risks including disinfectants, antibiotics, and gases such as ammonia and hydrogen sulfide, in addition to organic dusts and endotoxins.

  10. Chemical Synthesis of Glycosaminoglycans.

    PubMed

    Mende, Marco; Bednarek, Christin; Wawryszyn, Mirella; Sauter, Paul; Biskup, Moritz B; Schepers, Ute; Bräse, Stefan

    2016-07-27

    Glycosaminoglycans (GAGs) as one major part of the glycocalyx are involved in many essential biological cell processes, as well as in many courses of diseases. Because of the potential therapeutic application of GAG polymers, fragments, and also derivatives toward different diseases (e.g., heparin derivatives against Alzheimer's disease), there is a continual growing demand for new chemical syntheses, which suffice the high claim to stereoselectivity and chemoselectivity. This Review summarizes the progress of chemical syntheses of GAGs over the last 10 years. For each class of the glycosaminoglycans-hyaluronan (HA), heparan sulfate/heparin (HS/HP), chondroitin/dermatan sulfate (CS/DS), and keratan sulfate (KS)-mainly novel glycosylation strategies, elongation sequences, and protecting group patterns are discussed, but also (semi)automated syntheses, enzymatic approaches, and functionalizations of synthesized or isolated GAGs are considered.

  11. Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

    NASA Astrophysics Data System (ADS)

    Hernández-Martínez, L.; Carigi, L.; Peña, M.; Peimbert, M.

    2011-11-01

    Aims: Chemical evolution models are useful for understanding the formation and evolution of stars and galaxies. Model predictions will be more robust when more observational constraints are used. We present chemical evolution models for the dwarf irregular galaxy NGC 6822 using chemical abundances of old and young planetary nebulae (PNe) and H ii regions as observational constraints. We use two sets of chemical abundances, one derived from collisionally excited lines (CELs) and one from recombination lines (RLs). We use our models as a tool to distinguish between both procedures for abundance determinations. Methods: In our chemical evolution code the chemical contribution of low and intermediate mass stars is time-delayed, while for the massive stars the chemical contribution follows the instantaneous recycling approximation. Our models have two main free parameters: the mass-loss rate of a well-mixed outflow and the upper mass limit, Mup, of the initial mass function (IMF). To reproduce the gaseous mass and the present-day O/H value we need to vary the outflow rate and the Mup value. Results: We calculate two models with different Mup values that reproduce the constraints adequately. The abundances of old PNe agree with our models and support the star-formation history derived independently from photometric data. Both require an early well-mixed wind, lasting 5.3 Gyr, to reproduce the observed gaseous mass in the galaxy. In addition, by assuming a fraction of binaries producing SNIa of 1%, the models fit the Fe/H abundance ratio as derived from A supergiants. The first model (M4C), which assumes Mup = 40 M⊙, fits within errors smaller than 2σ the O/H, Ne/H, S/H, Ar/H and Cl/H abundances obtained from CELs for old and young PNe and H ii regions. The second model (M1R), which adopts Mup = 80 M⊙, reproduces within 2σ errors the O/H, C/H, Ne/H and S/H abundances adopted from RLs. Both models reproduce the increase of the O, Ne, S, and Ar elements during the

  12. Chemical sensor system

    NASA Technical Reports Server (NTRS)

    Darrach, Murray R. (Inventor); Chutjian, Ara (Inventor)

    2008-01-01

    A chemical sensing apparatus and method for the detection of sub parts-per-trillion concentrations of molecules in a sample by optimizing electron utilization in the formation of negative ions is provided. A variety of media may be sampled including air, seawater, dry sediment, or undersea sediment. An electrostatic mirror is used to reduce the kinetic energy of an electron beam to zero or near-zero kinetic energy.

  13. Chemically Reacting Turbulent Flow.

    DTIC Science & Technology

    1985-12-06

    pixel size, read rate, and single read capability. For this study, a linear silicon photodiode array produced by Reticon (RL128S) was chosen. This...array consists of 128 individual pixels located on 0.025 mm centers which have heights of 2.5 mm. The active length is therefore 3.2 mm. Reticon ...Mixing", presented by W.M. Pitts to the Nuclear Engineering Seminar of the Department of Chemical and Nuclear Engineering, University of Maryland

  14. Reproducibility in Chemical Research.

    PubMed

    Bergman, Robert G; Danheiser, Rick L

    2016-10-04

    "… To what extent is reproducibility a significant issue in chemical research? How can problems involving irreproducibility be minimized? … Researchers should be aware of the dangers of unconscious investigator bias, all papers should provide adequate experimental detail, and Reviewers have a responsibility to carefully examine papers for adequacy of experimental detail and support for the conclusions …" Read more in the Editorial by Robert G. Bergman and Rick L. Danheiser.

  15. Chemical bonding technology

    NASA Technical Reports Server (NTRS)

    Plueddemann, E.

    1986-01-01

    Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.

  16. Chemical Reactions in Clusters

    DTIC Science & Technology

    1992-11-04

    NH 3)n, n _> 4, clusters has been attributed to the (solvated) naphtholate anion.3a A single picosecond decay measurement has been reported which...vibrational energy in the cluster Sl state. The data are summarized in Table I. A model to explain these decay results can be constructed based on a proton...11 TITLE (Include Security Classification) Chemical Reactions in Clusters 12 PERSONAL AUTHOR(S) Elliot R. Bernstein 13a TYPE OF REPORT 13b TIME COVERED

  17. Chemical propulsion technology

    NASA Technical Reports Server (NTRS)

    Priem, R. J.

    1980-01-01

    An overview of NASA's low thrust liquid chemical propulsion program is presented with particular emphasis on thrust system technology in the ten to one thousand pound thrust range. Key technology issues include high performance of cooled low thrust engines; small cryogenic pumps; multiple starts-shutdowns (10) with slow ramps (approximately 10 seconds); thrust variation - 4/1 in flight and 20/1 between flights; long life (100 hours); improved system weight and size; and propellant selection.

  18. Chemical Interorbital Shuttle

    NASA Technical Reports Server (NTRS)

    1970-01-01

    In 1970, NASA initiated Phase A contracts to study alternate Space Shuttle designs in addition to the two-stage fully-reusable Space Shuttle system already under development. A number of alternate systems were developed to ensure the development of the optimum earth-to-orbit system, including the Stage-and-a-half Chemical Interorbital Shuttle, shown here. The concept would utilize a reusable marned spacecraft with an onboard propulsion system attached to an expendable fuel tank to provide supplementary propellants.

  19. Chemical and Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Bulluck, J. W.; Rushing, R. A.

    1997-01-01

    Work during the past three years has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-Ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted changes in the molecular weight distribution and the increased crosslinking of the Coflon material using Gel Permeation Chromatographic Analysis. Again these changes may result in variations in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, and Differential Scanning Calorimetry. We investigated a plethora of aged samples of both Tefzel and Coflon that were forwarded from MERL. Pressurized tests were performed on powdered PVDF in a modified Fluid A, which we will call A-2. In this case the ethylene diamine concentration was increased to 3 percent in methanol. Coflon pipe sections and powdered Coflon were exposed in pressure cells at 1700 psi at three separate test temperatures.

  20. Chemical and Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Bulluck, J. W.; Rushing, R. A.

    1994-01-01

    Thermal decomposition activation energies have been determined using two methods of Thermogravimetric Analysis (TGA), with good correlation being obtained between the two techniques. Initial heating curves indicated a two-component system for Coflon (i.e. polymer plus placticizer) but a single component system for Tefzel. Two widely differing activation energies were for Coflon supported this view, 15 kcl/mol being associated with plasticizer, and 40 kcal/mol with polymer degradation. With Tefzel, values were 40-45 kcal/mol, the former perhaps being associated with a low molecular weight fraction. Appropriate acceleration factors have been determined. Thermomechanical Analysis (TMA) has shown considerable dimensional change during temperature cycles. For unaged pipe sections heating to 100 C and then holding the temperature resulted in a stable thickness increase of 2%, whereas the Coflon thickness decreased continuously, reaching -4% in 2.7 weeks. Previously strained tensile bars of Tefzel expanded on cooling during TMA. SEM performed on H2S-aged Coflon samples showed significant changes in both physical and chemical nature. The first may have resulted from explosive decompression after part of the aging process. Chemically extensive dehydrofluorination was indicated, and sulfur was present as a result of the aging. These observations indicate that chemical attack of PVDF can occur in some circumstances.

  1. Chemical Education in Bulgaria

    NASA Astrophysics Data System (ADS)

    Garkov, Vladimir N.

    1999-08-01

    The sociopolitical changes in Eastern Europe of the 1990s and the ongoing globalization of the chemical industry and chemical education prompted this analysis of the current status of chemical education in Bulgaria, which is not very different from the educational practices in the rest of Europe. The level of chemistry knowledge expected from all high-school graduates in Bulgaria is roughly equivalent to the general and organic chemistry courses for science majors at U.S. universities. The newly introduced four-year bachelor's degree curriculum (based on 15-week semesters) at the University of Sofia includes a core of 106 semester hours (labs counted as 1 hour each), 41 semester hours of electives, and 445 contact hours (11 weeks) of research, which ends with a thesis defense. The instructional techniques in Bulgaria are subject-centered and follow the hierarchical structure of knowledge in an integrated and unitary manner. In conclusion, the Bulgarian system of education in chemistry aims at preparing a scientifically literate citizenry and broadly trained chemists by imposing a very challenging and rigid curriculum with very few choices. It is speculated that the laissez-faire climate of free intellectual initiative seen only at American universities provides a more appropriate environment for talent encouragement and scientific innovation for overseas-educated undergraduate and graduate students than their home institutions.

  2. Chemical Reactions at Surfaces

    SciTech Connect

    Michael Henderson and Nancy Ryan Gray

    2010-04-14

    Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

  3. Metabolomics in chemical ecology.

    PubMed

    Kuhlisch, Constanze; Pohnert, Georg

    2015-07-01

    Chemical ecology elucidates the nature and role of natural products as mediators of organismal interactions. The emerging techniques that can be summarized under the concept of metabolomics provide new opportunities to study such environmentally relevant signaling molecules. Especially comparative tools in metabolomics enable the identification of compounds that are regulated during interaction situations and that might play a role as e.g. pheromones, allelochemicals or in induced and activated defenses. This approach helps overcoming limitations of traditional bioassay-guided structure elucidation approaches. But the power of metabolomics is not limited to the comparison of metabolic profiles of interacting partners. Especially the link to other -omics techniques helps to unravel not only the compounds in question but the entire biosynthetic and genetic re-wiring, required for an ecological response. This review comprehensively highlights successful applications of metabolomics in chemical ecology and discusses existing limitations of these novel techniques. It focuses on recent developments in comparative metabolomics and discusses the use of metabolomics in the systems biology of organismal interactions. It also outlines the potential of large metabolomics initiatives for model organisms in the field of chemical ecology.

  4. Miniature Chemical Sensor

    SciTech Connect

    Andrew C. R. Pipino

    2004-12-13

    A new chemical detection technology has been realized that addresses DOE environmental management needs. The new technology is based on a variant of the sensitive optical absorption technique, cavity ring-down spectroscopy (CRDS). Termed evanescent-wave cavity ring-down spectroscopy (EW-CRDS), the technology employs a miniature solid-state optical resonator having an extremely high Q-factor as the sensing element, where the high-Q is achieved by using ultra-low-attenuation optical materials, ultra-smooth surfaces, and ultra-high reflectivity coatings, as well as low-diffraction-loss designs. At least one total-internal reflection (TIR) mirror is integral to the resonator permitting the concomitant evanescent wave to probe the ambient environment. Several prototypes have been designed, fabricated, characterized, and applied to chemical detection. Moreover, extensions of the sensing concept have been explored to enhance selectivity, sensitivity, and range of application. Operating primarily in the visible and near IR regions, the technology inherently enables remote detection by optical fiber. Producing 11 archival publications, 5 patents, 19 invited talks, 4 conference proceedings, a CRADA, and a patent-license agreement, the project has realized a new chemical detection technology providing >100 times more sensitivity than comparable technologies, while also providing practical advantages.

  5. Chemical and Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Bulluck, J. W.; Rushing, R. A.; Thornton, C. P.

    1996-01-01

    Work has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-Ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted changes in the molecular weight distribution of the Coflon material using a dual detector Gel Permeation Analysis. Again these changes may result in variation in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-Ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis, and Differential Scanning Calorimetry. We investigated a number of aged samples of both Tefzel and Coflon that were forwarded from MERL. Pressurized tests were performed in a modified Fluid G, which we will call G2. In this case the ethylene diamine concentration was increased to 3 percent in methanol. Coflon pipe sections and powdered Coflon were exposed in pressure cells at 1700 psi at three separate test temperatures, 70 C, 110 C, and 130 C. The primary purpose of the pressure tests in Fluid G2 was to further elucidate the aging mechanism of PVDF degradation.

  6. Understanding NMR Chemical Shifts

    NASA Astrophysics Data System (ADS)

    Jameson, Cynthia J.

    1996-10-01

    The NMR chemical shift serves as a paradigm for molecular electronic properties. We consider the factors that determine the general magnitudes of the shifts, the state of the art in theoretical calculations, the nature of the shielding tensor, and the multidimensional shielding surface that describes the variation of the shielding with nuclear positions. We also examine the nature of the intermolecular shielding surface as a general example of a supermolecule property surface. The observed chemical shift in the zero-pressure limit is determined not only by the value of the shielding at the equilibrium geometry, but the dynamic average over the multidimensional shielding surface during rotation and vibration of the molecule. In the gas, solution, or adsorbed phase it is an average of the intermolecular shielding surface over all the configurations of the molecule with its neighbors. The temperature dependence of the chemical shift in the isolated molecule, the changes upon isotopic substitution, the changes with environment, are well characterized experimentally so that quantum mechanical descriptions of electronic structure and theories related to dynamics averaging of any electronic property can be subjected to stringent test.

  7. CHEMICAL PRIORITIZATION FOR DEVELOPMENTAL ...

    EPA Pesticide Factsheets

    Defining a predictive model of developmental toxicity from in vitro and high-throughput screening (HTS) assays can be limited by the availability of developmental defects data. ToxRefDB (www.epa.gov/ncct/todrefdb) was built from animal studies on data-rich environmental chemicals, and has been used as an anchor for predictive modeling of ToxCast™ data. Scaling to thousands of untested chemicals requires another approach. ToxPlorer™ was developed as a tool to query and extract specific facts about defined biological entities from the open scientific literature and to coherently synthesize relevant knowledge about relationships, pathways and processes in toxicity. Here, we investigated the specific application of ToxPlorer to weighting HTS assay targets for relevance to developmental defects as defined in the literature. First, we systemically analyzed 88,193 Pubmed abstracts selected by bulk query using harmonized terminology for 862 developmental endpoints (www.devtox.net) and 364,334 dictionary term entities in our VT-KB (virtual tissues knowledgebase). We specifically focused on entities corresponding to genes/proteins mapped across of >500 ToxCast HTS assays. The 88,193 devtox abstracts mentioned 244 gene/protein entities in an aggregated total of ~8,000 occurrences. Each of the 244 assays was scored and weighted by the number of devtox articles and relevance to developmental processes. This score was used as a feature for chemical prioritization by Toxic

  8. Chemical Demonstrations with Consumer Chemicals: The Black and White Reaction.

    ERIC Educational Resources Information Center

    Wright, Stephen W.

    2002-01-01

    Describes a dramatic chemical demonstration in which chemicals that are black and white combine to produce a colorless liquid. Reactants include tincture of iodine, bleach, white vinegar, Epsom salt, vitamin C tablets, and liquid laundry starch. (DDR)

  9. Chemical Demilitarization - Assembled Chemical Weapons Assessment (ACWA): Root Cause Analysis

    DTIC Science & Technology

    2011-07-01

    Anniston Army Depot in Alabama, Umatilla Chemical Depot in Oregon, and Deseret Chemical Depot in Utah. The chemical weapons in these facilities account...program office has allocated additional costs for closure based on data from the closure process at the Umatilla and Anniston Chemical Agent Disposal...contractor, PCAPP is approximately five times as complex than the Anniston incineration facility and BGCAPP is roughly ten times as complex.7 As an

  10. Chemical Abstracts Service Chemical Registry System: History, Scope, and Impacts.

    ERIC Educational Resources Information Center

    Weisgerber, David W.

    1997-01-01

    Describes the history, scope, and applications of the Chemical Abstracts Service Chemical Registry System, a computerized database that uniquely identifies chemical substances on the basis of their molecular structures. Explains searching the system is and discusses its use as an international resource. (66 references) (Author/LRW)

  11. Chemical Educators Stress Industry Ties

    ERIC Educational Resources Information Center

    Worthy, Ward

    1975-01-01

    Describes various courses and programs designed to better prepare graduates to enter the chemical industry, including courses which stress the chemistry of industrial processes, and the economics of the chemical industry. (MLH)

  12. CHEMICAL STORAGE: MYTHS VERSUS REALITY

    SciTech Connect

    Simmons, F

    2007-03-19

    A large number of resources explaining proper chemical storage are available. These resources include books, databases/tables, and articles that explain various aspects of chemical storage including compatible chemical storage, signage, and regulatory requirements. Another source is the chemical manufacturer or distributor who provides storage information in the form of icons or color coding schemes on container labels. Despite the availability of these resources, chemical accidents stemming from improper storage, according to recent reports (1) (2), make up almost 25% of all chemical accidents. This relatively high percentage of chemical storage accidents suggests that these publications and color coding schemes although helpful, still provide incomplete information that may not completely mitigate storage risks. This manuscript will explore some ways published storage information may be incomplete, examine the associated risks, and suggest methods to help further eliminate chemical storage risks.

  13. Chemical Educators Mull Problems, Needs

    ERIC Educational Resources Information Center

    O'Sullivan, Dermot A.

    1977-01-01

    Discusses the international symposium on chemical education held in Ljubljana, Yugoslavia, August, 1977. Included are the symposium's recommendations for future international action relating to the problems and needs of chemical education. (SL)

  14. Safety Tips: Hazardous Chemical Storage.

    ERIC Educational Resources Information Center

    Williamson, J. R.

    1983-01-01

    Discusses storage of hazardous chemicals and provides a list of eight basic safety rules to use in developing a safe storage system. Suggestions include not storing materials alphabetically, storing nonreactive chemicals together, and not storing oxidizers and fuels together. (JN)

  15. Chemical Processing. Resources in Technology.

    ERIC Educational Resources Information Center

    Technology Teacher, 1991

    1991-01-01

    Reviews major organic and inorganic chemicals, their products, and the sociocultural impact of the chemical industry. Provides the following learning activity components: objectives, list of materials and equipment, procedures, student quiz with answers, and three references. (SK)

  16. Chemical Manufacturing Sector (NAICS 325)

    EPA Pesticide Factsheets

    find EPA regulatory information for the chemical manufacturing sector, including NESHAPs, the SNAP program for ozone depleting substances,effluent guidelines, and new and existing chemicals testing requirements under TSCA.

  17. Devices for collecting chemical compounds

    DOEpatents

    Scott, Jill R; Groenewold, Gary S

    2013-12-24

    A device for sampling chemical compounds from fixed surfaces and related methods are disclosed. The device may include a vacuum source, a chamber and a sorbent material. The device may utilize vacuum extraction to volatilize the chemical compounds from a fixed surface so that they may be sorbed by the sorbent material. The sorbent material may then be analyzed using conventional thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) instrumentation to determine presence of the chemical compounds. The methods may include detecting release and presence of one or more chemical compounds and determining the efficacy of decontamination. The device may be useful in collection and analysis of a variety of chemical compounds, such as residual chemical warfare agents, chemical attribution signatures and toxic industrial chemicals.

  18. Chemical Sensing in Process Analysis.

    ERIC Educational Resources Information Center

    Hirschfeld, T.; And Others

    1984-01-01

    Discusses: (1) rationale for chemical sensors in process analysis; (2) existing types of process chemical sensors; (3) sensor limitations, considering lessons of chemometrics; (4) trends in process control sensors; and (5) future prospects. (JN)

  19. LLNL Chemical Kinetics Modeling Group

    SciTech Connect

    Pitz, W J; Westbrook, C K; Mehl, M; Herbinet, O; Curran, H J; Silke, E J

    2008-09-24

    The LLNL chemical kinetics modeling group has been responsible for much progress in the development of chemical kinetic models for practical fuels. The group began its work in the early 1970s, developing chemical kinetic models for methane, ethane, ethanol and halogenated inhibitors. Most recently, it has been developing chemical kinetic models for large n-alkanes, cycloalkanes, hexenes, and large methyl esters. These component models are needed to represent gasoline, diesel, jet, and oil-sand-derived fuels.

  20. Chemical kinetics modeling

    SciTech Connect

    Westbrook, C.K.; Pitz, W.J.

    1993-12-01

    This project emphasizes numerical modeling of chemical kinetics of combustion, including applications in both practical combustion systems and in controlled laboratory experiments. Elementary reaction rate parameters are combined into mechanisms which then describe the overall reaction of the fuels being studied. Detailed sensitivity analyses are used to identify those reaction rates and product species distributions to which the results are most sensitive and therefore warrant the greatest attention from other experimental and theoretical research programs. Experimental data from a variety of environments are combined together to validate the reaction mechanisms, including results from laminar flames, shock tubes, flow systems, detonations, and even internal combustion engines.

  1. Chemical sensor system

    DOEpatents

    Darrow, Christopher B.; Satcher, Jr., Joe H.; Lane, Stephen M.; Lee, Abraham P.; Wang, Amy W.

    2002-01-01

    An implantable chemical sensor system for medical applications is described which permits selective recognition of an analyte using an expandable biocompatible sensor, such as a polymer, that undergoes a dimensional change in the presence of the analyte. The expandable polymer is incorporated into an electronic circuit component that changes its properties (e.g., frequency) when the polymer changes dimension. As the circuit changes its characteristics, an external interrogator transmits a signal transdermally to the transducer, and the concentration of the analyte is determined from the measured changes in the circuit. This invention may be used for minimally invasive monitoring of blood glucose levels in diabetic patients.

  2. Galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Mollá, M.; Cavichia, O.; da Costa, R.; Gibson, B. K.; Díaz, A. I.

    2017-03-01

    We analyze the evolution of oxygen abundance radial gradients resulting from our chemical evolution models calculated with different prescriptions for the star formation rate (SFR) and for the gas infall rate, in order to assess their respective roles in shaping gradients. We also compare with cosmological simulations and confront all with recent observational datasets, in particular with abundances inferred from planetary nebulae. We demonstrate the critical importance in isolating the specific radial range over which a gradient is measured, in order for their temporal evolution to be useful indicators of disk growth with redshift.

  3. Chemical and Biological Kinetics

    NASA Astrophysics Data System (ADS)

    Emanuel', N. M.

    1981-10-01

    Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.

  4. Chemical Microthruster Options

    NASA Technical Reports Server (NTRS)

    DeGroot, Wim; Oleson, Steve

    1996-01-01

    Chemical propulsion systems with potential application to microsatellites are classified by propellant phase, i.e. gas, liquid, or solid. Four promising concepts are selected based on performance, weight, size, cost, and reliability. The selected concepts, in varying stages of development, are advanced monopropellants, tridyne(TM), electrolysis, and solid gas generator propulsion. Tridyne(TM) and electrolysis propulsion are compared vs. existing cold gas and monopropellant systems for selected microsatellite missions. Electrolysis is shown to provide a significant weight advantage over monopropellant propulsion for an orbit transfer and plane change mission. Tridyne(TM) is shown to provide a significant advantage over cold gas thrusters for orbit trimming and spacecraft separation.

  5. Green chemistry for chemical synthesis

    PubMed Central

    Li, Chao-Jun; Trost, Barry M.

    2008-01-01

    Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign. PMID:18768813

  6. Modern Chemical Technology, Volume 8.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is one of a series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: amino acids and proteins, carbohydrates, synthetic polymers, other natural products, chemical separations…

  7. Mass Transfer with Chemical Reaction.

    ERIC Educational Resources Information Center

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  8. Modern Chemical Technology, Volume 5.

    ERIC Educational Resources Information Center

    Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.

    This volume contains chapters 26-31 for the American Chemical Society (ACS) "Modern Chemical Technology" (ChemTeC) instructional material intended to prepare chemical technologists. Chapter 26 reviews oxidation and reduction, including applications in titrations with potassium permanganate and iodometry. Coordination compounds are…

  9. Chemical Waste Management and Disposal.

    ERIC Educational Resources Information Center

    Armour, Margaret-Ann

    1988-01-01

    Describes simple, efficient techniques for treating hazardous chemicals so that nontoxic and nonhazardous residues are formed. Discusses general rules for management of waste chemicals from school laboratories and general techniques for the disposal of waste or surplus chemicals. Lists specific disposal reactions. (CW)

  10. Chemical Waste and Allied Products.

    PubMed

    Hung, Yung-Tse; Aziz, Hamidi Abdul; Ramli, Siti Fatihah; Yeh, Ruth Yu-Li; Liu, Lian-Huey; Huhnke, Christopher Robert

    2016-10-01

    This review of literature published in 2015 focuses on waste related to chemical and allied products. The topics cover the waste management, physicochemical treatment, aerobic granular, aerobic waste treatment, anaerobic granular, anaerobic waste treatment, chemical waste, chemical wastewater, fertilizer waste, fertilizer wastewater, pesticide wastewater, pharmaceutical wastewater, ozonation. cosmetics waste, groundwater remediation, nutrient removal, nitrification denitrification, membrane biological reactor, and pesticide waste.

  11. Safer Chemicals Research Fact Sheets

    EPA Pesticide Factsheets

    Chemical safety is a major priority of the U.S. EPA. Moving toward a healthier, more sustainable environment requires making safer, “greener” chemicals and producing new and existing chemicals in ways that are safer for humans and wildlife.

  12. The chemical ecology of cyanobacteria

    PubMed Central

    Leão, Pedro N.; Engene, Niclas; Antunes, Agostinho; Gerwick, William H.; Vasconcelos, Vitor

    2014-01-01

    This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed. PMID:22237837

  13. Modern Chemical Technology, Volume 6.

    ERIC Educational Resources Information Center

    Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.

    This volume contains chapters 32-39 for the American Chemical Society (ACS) "Modern Chemical Technology" (ChemTeC) instructional materials intended to prepare chemical technologists. The study of organic chemistry is continued as these major topics are considered: alcohols and phenols, alkyl and aryl halides, ethers, aldehydes and…

  14. Identification of Chemical Toxicity Using Ontology Information of Chemicals.

    PubMed

    Jiang, Zhanpeng; Xu, Rui; Dong, Changchun

    2015-01-01

    With the advance of the combinatorial chemistry, a large number of synthetic compounds have surged. However, we have limited knowledge about them. On the other hand, the speed of designing new drugs is very slow. One of the key causes is the unacceptable toxicities of chemicals. If one can correctly identify the toxicity of chemicals, the unsuitable chemicals can be discarded in early stage, thereby accelerating the study of new drugs and reducing the R&D costs. In this study, a new prediction method was built for identification of chemical toxicities, which was based on ontology information of chemicals. By comparing to a previous method, our method is quite effective. We hope that the proposed method may give new insights to study chemical toxicity and other attributes of chemicals.

  15. The chemical peel.

    PubMed

    Peters, W

    1991-06-01

    Chemical peeling of facial skin has become a valuable adjunct in the armamentarium of the facial aesthetic surgeon. Among the various techniques available, phenol solutions are the most commonly used. Peeling produces a controlled, partial-thickness chemical burn of the epidermis and the outer dermis. Several techniques are available to "fine tune" the depth of the peel. Regeneration of peeled skin results in a fresh, orderly, organized epidermis. In the dermis, a new 2- to 3-mm band of dense, compact, orderly collagen is formed between the epidermis and the underlying damaged dermis, which results in effective ablation of the fine wrinkles in the skin and a reduction of pigmentation. These clinical and histological changes are long lasting (15-20 years) and may be permanent in some patients. Because of the metabolism and systemic complications of phenol, patient selection should involve systemic evaluation of liver, renal, and cardiac function, as well as an evaluation of the skin quality and medication status of the patient. Because of potential cardiac arrhythmias, peeling must be performed in a medically supervised environment, with continuous cardiac monitoring. The local complications of peeling include pigmentation changes, scarring, milia, ectropion, infection, activation of herpes simplex, and toxic shock syndrome.

  16. Chemical simulation of greywater.

    PubMed

    Abed, Suhail Najem; Scholz, Miklas

    2016-01-01

    Sustainable water resources management attracts considerable attention in today's world. Recycling and reuse of both wastewater and greywater are becoming more attractive. The strategy is to protect ecosystem services by balancing the withdrawal of water and the disposal of wastewater. In the present study, a timely and novel synthetic greywater composition has been proposed with respect to the composition of heavy metals, nutrients and organic matter. The change in water quality of the synthetic greywater due to increasing storage time was monitored to evaluate the stability of the proposed chemical formula. The new greywater is prepared artificially using analytical-grade chemicals to simulate either low (LC) or high (HC) pollutant concentrations. The characteristics of the synthetic greywater were tested (just before starting the experiment, after two days and a week of storage under real weather conditions) and compared to those reported for real greywater. Test results for both synthetic greywater types showed great similarities with the physiochemical properties of published findings concerning real greywater. Furthermore, the synthetic greywater is relatively stable in terms of its characteristics for different storage periods. However, there was a significant (p < .05) reduction in 5-day biochemical oxygen demand (BOD5) for both low (LC) and high (HC) concentrations of greywater after two days of storage with reductions of 62% and 55%, respectively. A significant (p < .05) change was also noted for the reduction (70%) of nitrate-nitrogen (NO3-N) concerning HC greywater after seven days of storage.

  17. Controlling toxic chemicals

    SciTech Connect

    Postel, S.

    1988-01-01

    The use of pesticides in agriculture and the disposal of industrial chemical wastes constitute two major pathways by which people are inadvertently exposed to toxics. These practices release hundreds of millions of tons of potentially hazardous substances into the environment each year. In many ways the situation with industrial chemical waste parallels the predicament with pesticides: Not only are current practices contaminating the environment and creating health risks, but they are unsustainable over the long term. Strategies that reduce pesticide use in agriculture and minimize waste generation in industry offer cost-effective approaches to decreasing risks from toxics. Such strategies differ fundamentally from current practice and require new ways of thinking. The quick fixes of pesticide spraying and end-of-pipe pollution control are replaced with new production systems aimed at reconciling economic profits with environmental protection. Current efforts in integrated pest management and industrial waste reduction, although clearly promising, only hint at their long-term potential for detoxifying the environment.

  18. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1981-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  19. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  20. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to faciliate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  1. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate intallation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  2. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A.

    2011-05-20

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  3. Chemical Reactions in DSMC

    NASA Astrophysics Data System (ADS)

    Bird, G. A.

    2011-05-01

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  4. Pressure Controlled Chemical Gardens.

    PubMed

    Bentley, Megan R; Batista, Bruno C; Steinbock, Oliver

    2016-06-30

    The dissolution of metal salts in silicate solution can result in the growth of hollow precipitate tubes. These "chemical gardens" are a model of self-organization far from the equilibrium and create permanent macroscopic structures. The reproducibility of the growth process is greatly improved if the solid salt seed is replaced by a salt solution that is steadily injected by a pump; however, this modification of the original experiment eliminates the membrane-based osmotic pump at the base of conventional chemical gardens and does not allow for analyses in terms of the involved pressure. Here we describe a new experimental method that delivers the salt solution according to a controlled hydrostatic pressure. In one form of the experiment, this pressure slowly decreases as zinc sulfate solution flows into the silicate-containing reaction vessel, whereas a second version holds the respective solution heights constant. In addition to three known growth regimes (jetting, popping, budding), we observe single tubes that fill the vessel in a horizontally undulating but vertically layered fashion (crowding). The resulting, dried product has a cylindrical shape, very low density, and one continuous connection from top to bottom. We also present phase diagrams of these growth modes and show that the flow characteristics of our experiments follow a reaction-independent Hagen-Poiseuille equation.

  5. [Chemical food contaminants].

    PubMed

    Schrenk, D

    2004-09-01

    Chemical food contaminants are substances which are neither present naturally in the usual raw material used for food production nor are added during the regular production process. Examples are environmental pollutants or contaminants derived from agricultural production of crops or livestock or from inadequate manufacturing of the food product itself. More difficult is the classification of those compounds formed during regular manufacturing such as products of thermal processes including flavoring substances. In these cases, it is common practice to call those compounds contaminants which are known for their adverse effects such as acrylamide, whereas constituents which add to the food-specific flavor such as Maillard products formed during roasting, baking etc. are not termed contaminants. From a toxicological viewpoint this distinction is not always clear-cut. Important groups of chemical contaminants are metals such as mercury or lead, persistent organic pollutants such as polychlorinated biphenyls and related pollutants, which are regularly found in certain types of food originating from background levels of these compounds in our environment. Furthermore, natural toxins form microorganisms or plants, and compounds formed during thermal treatment of food are of major interest. In general, a scientific risk assessment has to be carried out for any known contaminant. This comprises an exposure analysis and a toxicological and epidemiological assessment. On these grounds, regulatory and/or technological measures can often improve the situation. Major conditions for a scientific risk assessment and a successful implementation of regulations are highly developed food quality control, food toxicology and nutritional epidemiology.

  6. Chemical organisation theory.

    PubMed

    Dittrich, Peter; di Fenizio, Pietro Speroni

    2007-05-01

    Complex dynamical reaction networks consisting of many components that interact and produce each other are difficult to understand, especially, when new component types may appear and present component types may vanish completely. Inspired by Fontana and Buss (Bull. Math. Biol., 56, 1-64) we outline a theory to deal with such systems. The theory consists of two parts. The first part introduces the concept of a chemical organisation as a closed and self-maintaining set of components. This concept allows to map a complex (reaction) network to the set of organisations, providing a new view on the system's structure. The second part connects dynamics with the set of organisations, which allows to map a movement of the system in state space to a movement in the set of organisations. The relevancy of our theory is underlined by a theorem that says that given a differential equation describing the chemical dynamics of the network, then every stationary state is an instance of an organisation. For demonstration, the theory is applied to a small model of HIV-immune system interaction by Wodarz and Nowak (Proc. Natl. Acad. USA, 96, 14464-14469) and to a large model of the sugar metabolism of E. Coli by Puchalka and Kierzek (Biophys. J., 86, 1357-1372). In both cases organisations where uncovered, which could be related to functions.

  7. Frontiers in Chemical Physics

    SciTech Connect

    Bowlan, Pamela Renee

    2016-05-02

    These are slides dealing with frontiers in chemical physics. The following topics are covered: Time resolving chemistry with ultrashort pulses in the 0.1-40 THz spectral range; Example: Mid-infrared absorption spectrum of the intermediate state CH2OO; Tracking reaction dynamics through changes in the spectra; Single-shot measurement of the mid-IR absorption dynamics; Applying 2D coherent mid-IR spectroscopy to learn more about transition states; Time resolving chemical reactions at a catalysis using mid-IR and THz pulses; Studying topological insulators requires a surface sensitive probe; Nonlinear phonon dynamics in Bi2Se3; THz-pump, SHG-probe as a surface sensitive coherent 2D spectroscopy; Nanometer and femtosecond spatiotemporal resolution mid-IR spectroscopy; Coherent two-dimensional THz/mid-IR spectroscopy with 10nm spatial resolution; Pervoskite oxides as catalysts; Functionalized graphene for catalysis; Single-shot spatiotemporal measurements; Spatiotemporal pulse measurement; Intense, broad-band THz/mid-IR generation with organic crystals.

  8. Chemical Looping Combustion Kinetics

    SciTech Connect

    Edward Eyring; Gabor Konya

    2009-03-31

    One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

  9. Wearable Optical Chemical Sensors

    NASA Astrophysics Data System (ADS)

    Lobnik, Aleksandra

    Wearable sensors can be used to provide valuable information about the wearer's health and/or monitor the wearer's surroundings, identify safety concerns and detect threats, during the wearer's daily routine within his or her natural environment. The "sensor on a textile", an integrated sensor capable of analyzing data, would enable early many forms of detection. Moreover, a sensor connected with a smart delivery system could simultaneously provide comfort and monitoring (for safety and/or health), non-invasive measurements, no laboratory sampling, continuous monitoring during the daily activity of the person, and possible multi-parameter analysis and monitoring. However, in order for the technology to be accessible, it must remain innocuous and impose a minimal intrusion on the daily activities of the wearer. Therefore, such wearable technologies should be soft, flexible, and washable in order to meet the expectations of normal clothing. Optical chemical sensors (OCSs) could be used as wearable technology since they can be embedded into textile structures by using conventional dyeing, printing processes and coatings, while fiber-optic chemical sensors (FOCSs) as well as nanofiber sensors (NFSs) can be incorporated by weaving, knitting or laminating. The interest in small, robust and sensitive sensors that can be embedded into textile structures is increasing and the research activity on this topic is an important issue.

  10. [Child health and chemical safety].

    PubMed

    Morita, Takeshi; Ishimitsu, Susumu; Morikawa, Kaoru

    2005-01-01

    Recently concern over the hazards posed by chemicals to children has become more active. Many chemicals have been introduced into the market within the past several decades. These chemicals are used widely in consumer products and dispersed in the environment. Children are at risk of exposure to such chemicals. Scientific understanding has also improved about the vulnerability of children to chemical hazards. As children represent the future of our societies, protecting their health is an important issue. Thus, many actions are being undertaken by international organizations, e.g., the World Health Organization and the United Nations, and regulatory bodies in Japan, the US and the EU, based on the probable vulnerability of infants and children to chemicals. In this paper, these efforts and state measures are summarized, the characteristics of children at risk assessed, and the list of chemicals concerning child health as well as future actions in Japan are presented.

  11. Natural chemicals, synthetic chemicals, risk assessment, and cancer

    SciTech Connect

    Ames, B.N.; Gold, L.S. )

    1990-01-01

    The administration of chemicals at the maximum tolerated dose (MTD) in standard animal cancer tests is postulated to increase cell division (mitogenesis), which in turn increases rates of mutagenesis and thus carcinogenesis. The animal data are consistent with this mechanism, because a high proportion of all chemicals tested are indeed rodent carcinogens. We conclude that at the low doses of most human exposures, where cell killing does not occur, the hazards to humans of rodent carcinogens may be much lower than is commonly assumed. The toxicological significance of exposures to synthetic chemicals is examined in the context of exposures to naturally occurring chemicals. We calculate that 99.99% of the pesticides in the American diet are chemicals that plants produce to defend themselves. Only 52 natural pesticides have been tested in high-dose animal cancer tests, and about half (27) are rodent carcinogens; these 27 are shown to be present in many common foods. We conclude that natural and synthetic chemicals are equally likely to be positive in animal cancer tests. The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol and ethanol. The finding that in high-dose tests, a high proportion of both natural and synthetic chemicals are carcinogens, mutagens, teratogens, and clastogens (30-50% for each group) undermines current regulatory effects based on these tests to protect public health from low doses of synthetic chemicals.

  12. Superficial chemical peels.

    PubMed

    Zakopoulou, N; Kontochristopoulos, G

    2006-09-01

    Superficial chemical peeling (SCP) involves the application of a peeling agent to the skin, resulting in destruction of part or all of the epidermis. SCP is mainly recommended for facial rejuvenation, photoaging and superficial rhytides, pigmentary dyschromias and acne. It can be used on all Fitzpatrick skin types, no sedation is needed, and the desquamation is usually well accepted. Overpeel and complications are very rare. The most commonly used SCP agents are glycolic acid 20-70%, trichloroacetic acid 10-35%, Jessner's solution, salicylic acid, pyruvic acid, resorcinol 30-50% preparations, and solid carbon dioxide. The careful selection of patients is critical for the outcome of a SCP and contraindications must be seriously considered. The peel procedure is generally common for all SCP agents but a good knowledge of the specific characters of each agent is of great importance in order to decide which to use for each individual patient.

  13. Chemical composition of Mars

    NASA Technical Reports Server (NTRS)

    Morgan, J. W.; Anders, E.

    1979-01-01

    The chemical composition of Mars is estimated from the cosmochemical model of Ganapathy and Anders (1974) with additional petrological and geophysical constraints. The model assumes that planets and chondrites underwent the same fractionation processes in the solar nebula, and constraints are imposed by the abundance of the heat-producing elements, U, Th and K, the volatile-rich component and the high density of the mantle. Global abundances of 83 elements are presented, and it is noted that the mantle is an iron-rich garnet wehrlite, nearly identical to the bulk moon composition of Morgan at al. (1978) and that the core is sulfur poor (3.5% S). The comparison of model compositions for the earth, Venus, Mars, the moon and a eucrite parent body suggests that volatile depletion correlates mainly with size rather than with radial distance from the sun.

  14. Groundwater and organic chemicals

    SciTech Connect

    Dawson, H.E.

    1995-12-01

    Groundwater is a major source of drinking water for many communities. Unfortunately, organic chemicals such as dry cleaning fluids, solvent, fuels, and pesticides have contaminated groundwater in many areas, rendering the groundwater useless as a drinking water resource. In many cases, the groundwater cannot be cleaned up with current technologies, particularly if the groundwater has been contaminated with immiscible (low solubility) organic liquids. In this talk, I will describe the path I have followed from geologist to geochemist and finally to environmental engineer. As a geologist, I studied the chemistry of rock metamorphosis. As a geochemist, I explored for gold and other metals. Now as an environmental engineer, I investigate the behavior of organic liquids in the subsurface. While these fields all appear very different, in reality I have always focused on the interaction of rocks or sediments with the fluids with which they come in contact.

  15. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    A chemical vapor deposition (CVD) reactor system with a vertical deposition chamber was used for the growth of Si films on glass, glass-ceramic, and polycrystalline ceramic substrates. Silicon vapor was produced by pyrolysis of SiH4 in a H2 or He carrier gas. Preliminary deposition experiments with two of the available glasses were not encouraging. Moderately encouraging results, however, were obtained with fired polycrystalline alumina substrates, which were used for Si deposition at temperatures above 1,000 C. The surfaces of both the substrates and the films were characterized by X-ray diffraction, reflection electron diffraction, scanning electron microscopy optical microscopy, and surface profilometric techniques. Several experiments were conducted to establish baseline performance data for the reactor system, including temperature distributions on the sample pedestal, effects of carrier gas flow rate on temperature and film thickness, and Si film growth rate as a function of temperature.

  16. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    The chemical vapor deposition (CVD) method for the growth of Si sheet on inexpensive substrate materials is investigated. The objective is to develop CVD techniques for producing large areas of Si sheet on inexpensive substrate materials, with sheet properties suitable for fabricating solar cells meeting the technical goals of the Low Cost Silicon Solar Array Project. Specific areas covered include: (1) modification and test of existing CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures, using standard and near-standard processing techniques.

  17. Concordant Chemical Reaction Networks

    PubMed Central

    Shinar, Guy; Feinberg, Martin

    2015-01-01

    We describe a large class of chemical reaction networks, those endowed with a subtle structural property called concordance. We show that the class of concordant networks coincides precisely with the class of networks which, when taken with any weakly monotonic kinetics, invariably give rise to kinetic systems that are injective — a quality that, among other things, precludes the possibility of switch-like transitions between distinct positive steady states. We also provide persistence characteristics of concordant networks, instability implications of discordance, and consequences of stronger variants of concordance. Some of our results are in the spirit of recent ones by Banaji and Craciun, but here we do not require that every species suffer a degradation reaction. This is especially important in studying biochemical networks, for which it is rare to have all species degrade. PMID:22659063

  18. Volatile chemical reagent detector

    DOEpatents

    Chen, Liaohai; McBranch, Duncan; Wang, Rong; Whitten, David

    2004-08-24

    A device for detecting volatile chemical reagents based on fluorescence quenching analysis that is capable of detecting neutral electron acceptor molecules. The device includes a fluorescent material, a contact region, a light source, and an optical detector. The fluorescent material includes at least one polymer-surfactant complex. The polymer-surfactant complex is formed by combining a fluorescent ionic conjugated polymer with an oppositely charged surfactant. The polymer-surfactant complex may be formed in a polar solvent and included in the fluorescent material as a solution. Alternatively, the complex may be included in the fluorescent material as a thin film. The use of a polymer-surfactant complex in the fluorescent material allows the device to detect both neutral and ionic acceptor molecules. The use of a polymer-surfactant complex film allows the device and the fluorescent material to be reusable after exposing the fluorescent material to a vacuum for limited time.

  19. CHRIS: Hazardous Chemical Data

    DTIC Science & Technology

    1978-10-01

    54 Toolclybylnhalalon(ThreldLeslVasw): 11. 16 41115, 23 NFPAHaUrdC~mmaoe 1315 HOWaloluion: 󈧅 fOl -I11 55 Short- Teen InhIon801 Umlim D-1. 11,4 -0...134 Omed. PornO o ’ c 3. CHEMICAL DESIGNATIONS 4. OBS!RVABLE CIIAAIERISTICS 88~3 e~aTmeaer~~el80 8.88.8 Syanv 81p t~ah~~r q, ’ W36 Ce4IcalPoernar S~nn...1 Ntnien .- ad 4MNlo,d h, AA t 132 Molear aWaiglt %Nrltl-:~ I ,,i,64 an rlr,.rca (,J, ooImJA ~n,1- 13.3 BolrrgPoirttlatam Son ,h 14Frosang PornO _2

  20. Chemical and Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Bulluck, J. W.; Rushing, R. A.

    1995-01-01

    During the past six months we have conducted significant research in several domains in order to clarify and understanding the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. We organized numerous analytical studies with methods including Fourier Transform Infrared Spectroscopy, Dynamic Mechanical Analysis, Differential Scanning Calorimetry, and Stress Relaxation experiments. In addition we have reanalyzed previous thermogravimetric data concerning the rate of deplasticization of Coflon pipe. We investigated a number of aged samples of both Tefzel and Coflon that were forwarded from MERL. We conducted stress relaxation experiments of Coflon pipe at several temperatures and determined an activation energy. We also examined the dynamic mechanical response PVDF during deplasticization and during methanol plasticization. We performed numerous DSC analyses to research the changing crystalline morphology. We have noted significant changes in crystallinity upon aging for both PVDF and Tefzel. Little variation in elemental composition was noted for many of the aged Coflon and Tefzel samples tested.

  1. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1980-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer. The heat pump part of the system heats or cools a house or other structure through a combination of evaporation and absorption or, conversely, condensation and desorption, in a pair of containers. A set of automatic controls change the system for operation during winter and summer months and for daytime and nighttime operation to satisfactorily heat and cool a house during an entire year. The absorber chamber is subjected to solar heating during regeneration cycles and is covered by one or more layers of glass or other transparent material. Daytime home air used for heating the home is passed at appropriate flow rates between the absorber container and the first transparent cover layer in heat transfer relationship in a manner that greatly reduce eddies and resultant heat loss from the absorbant surface to ambient atmosphere.

  2. The unfought chemical war

    SciTech Connect

    Freeman, K. )

    1991-12-01

    In December 1943, in the middle of the scorching northern Australia summer, a young Australian commando, Tom Mitchell, sweated in his respirator and gas-protective clothing as he got ready to take part in a mustard-gas experiment. He grimly watched six US aircraft, B-24 Liberators, drop bombs filled with mustard gas on Brook Island, near Innisfail in the state of Queensland. Ten minutes later, Mitchell was rushing around the island to tend sampling equipment. But a few hours later, he and another Australian soldier were ordered back onto the island - this time, stripped of their respirators and protective clothing. They were forced to camp on the island from dusk to dawn in ordinary clothing without any safety equipment. Mitchell now suffers from lung and heart disease. Last year, nearly 47 years after he was burned, Mitchell settled with the Australian government for $25,000 (Australian). Publicity over his lawsuit, filed in 1981, along with revelations made in a documentary film broadcast in Australia in 1989, has prompted thousands of other Australian survivors of chemical-warfare tests to ask the Australian Department of Veterans Affairs for disability benefits. Veterans of chemical-warfare tests are also breaking their silence in the United States and Canada, stepping forward to seek compensation for their injuries. The impetus behind the US revelations came from a campaign begun in 1989 by Cong. Porter Goss, a Florida Republican, to win benefits for four participants in US Navy mustard-gas tests. During a flurry of publicity in mid-June 1991, the Department of Veterans Affairs announced that it was relaxing its rules to make it easier for World War 2 mustard-gas victims to collect benefits. In Canada, an information hot line run by the Department of National Defense in 1988 and a 1989 book by John Bryden, Deadly Allies: Canada's Secret War 1937-1947, brought the tests to national attention.

  3. Chemical properties of mendelevium

    SciTech Connect

    Hulet, E.K.

    1980-11-01

    Even with the most intense ion beams and the largest available quantities of target isotope, about 10/sup 6/ atoms at a time is all the Md that can be produced for chemical studies. This lack of sufficient sample size coupled with the very short lifetimes of the few atoms produced has severely restricted the gathering and the broadness of our knowledge concerning the properties of Md and the heavier elements. To illustrate, the literature contains a mere eleven references to the chemical studies of Md, and none of these deal with bulk properties associated with the element bound in solid phases. Some of these findings are: Md was found to be more volatile than other actinide metals which lead to the belief that it is divalent in the metallic state; separation of Md from the other actinides can be accomplished either by reduction of Md/sup 3 +/ to the divalent state or by chromatographic separations with Md remaining in the tripositive state; extraction of Md/sup 2 +/ with bis(2-ethylhexyl)phosphoric acid is much poorer than the extraction of the neighboring tripositive actinides; attempts to oxidize Md/sup 3 +/ with sodium bismuthate failed to show any evidence for Md/sup 4 +/; reduction potential of Md/sup 3 +/ was found to be close to -0.1 volt; Md/sup 3 +/ can be reduced to Md(Hg) by sodium amalgams and by electrolysis; the electrochemical behavior of Md is very similar to that of Fm and can be summarized in the equation, Md/sup 2 +/ + 2e/sup -/ = Md(Hg) and E/sup 0/ = -1.50 V.; and Md cannot be reduced to a monovalent ion with Sm/sup 2 +/.

  4. Gas phase chemical detection with an integrated chemical analysis system

    SciTech Connect

    CASALNUOVO,STEPHEN A.; FRYE-MASON,GREGORY CHARLES; KOTTENSTETTE,RICHARD; HELLER,EDWIN J.; MATZKE,CAROLYN M.; LEWIS,PATRICK R.; MANGINELL,RONALD P.; BACA,ALBERT G.; HIETALA,VINCENT M.

    2000-04-12

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample preconcentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described.

  5. Gas Phase Chemical Detection with an Integrated Chemical Analysis System

    SciTech Connect

    Baca, Albert G.; Casalnuovo, Stephen A.; Frye-Mason, Gregory C.; Heller, Edwin J.; Hietala, Susan L.; Hietala, Vincent M.; Kottenstette, Richard J.; Lewis, Patrick R.; Manginell, Ronald P.; Matzke, Carloyn M.; Reno, John L.; Sasaki, Darryl Y.; Schubert, W. Kent

    1999-07-08

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample concentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described. The design and performance of novel micromachined acoustic wave devices, with the potential for improved chemical sensitivity, are also described.

  6. Chemical Engineering in Space

    NASA Technical Reports Server (NTRS)

    Lobmeyer, Dennis A.; Meneghelli, Barry J.

    2001-01-01

    The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit and escape the bonds of Earth's gravity. In the future there may be other means available; however, currently few of these alternatives can compare to the speed or the ease of use provided by cryogenic chemical propulsion agents. Cryogenics, the science and art of producing cold operating conditions, has become increasingly important to our ability to travel within our solar system. The production and transport of cryogenic fuels as well as the long-term storage of these fluids are necessary for mankind to travel within our solar system. It is with great care and at a significant cost that gaseous compounds such as hydrogen and oxygen are liquified and become dense enough to use for rocket fuel. As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a complete round-trip. The cost and the size of any expedition to another celestial body are extreme. If we are constrained by the need to take everything necessary (fuel, life support, etc.) for our survival and return, we greatly increase the risk of being able to go. As with the early explorers on Earth, we will need to harvest much of our energy and our life support from the celestial bodies. The in situ production of these energy sources is paramount to success. Due to the current propulsion system designs, the in-situ processes will require liquefaction and the application of cryogenics. The challenge we face for the near future is to increase our understanding of cryogenic long-term storage and off-world production of cryogenic fluids. We must do this all within the boundaries of very restricted size, weight, and robustness parameters so that we may launch these apparatus from Earth and utilize them elsewhere. Miniaturization, efficiency, and physically robust systems will all play a part in

  7. Systematic chemical-genetic and chemical-chemical interaction datasets for prediction of compound synergism

    PubMed Central

    Wildenhain, Jan; Spitzer, Michaela; Dolma, Sonam; Jarvik, Nick; White, Rachel; Roy, Marcia; Griffiths, Emma; Bellows, David S.; Wright, Gerard D.; Tyers, Mike

    2016-01-01

    The network structure of biological systems suggests that effective therapeutic intervention may require combinations of agents that act synergistically. However, a dearth of systematic chemical combination datasets have limited the development of predictive algorithms for chemical synergism. Here, we report two large datasets of linked chemical-genetic and chemical-chemical interactions in the budding yeast Saccharomyces cerevisiae. We screened 5,518 unique compounds against 242 diverse yeast gene deletion strains to generate an extended chemical-genetic matrix (CGM) of 492,126 chemical-gene interaction measurements. This CGM dataset contained 1,434 genotype-specific inhibitors, termed cryptagens. We selected 128 structurally diverse cryptagens and tested all pairwise combinations to generate a benchmark dataset of 8,128 pairwise chemical-chemical interaction tests for synergy prediction, termed the cryptagen matrix (CM). An accompanying database resource called ChemGRID was developed to enable analysis, visualisation and downloads of all data. The CGM and CM datasets will facilitate the benchmarking of computational approaches for synergy prediction, as well as chemical structure-activity relationship models for anti-fungal drug discovery. PMID:27874849

  8. Systematic chemical-genetic and chemical-chemical interaction datasets for prediction of compound synergism.

    PubMed

    Wildenhain, Jan; Spitzer, Michaela; Dolma, Sonam; Jarvik, Nick; White, Rachel; Roy, Marcia; Griffiths, Emma; Bellows, David S; Wright, Gerard D; Tyers, Mike

    2016-11-22

    The network structure of biological systems suggests that effective therapeutic intervention may require combinations of agents that act synergistically. However, a dearth of systematic chemical combination datasets have limited the development of predictive algorithms for chemical synergism. Here, we report two large datasets of linked chemical-genetic and chemical-chemical interactions in the budding yeast Saccharomyces cerevisiae. We screened 5,518 unique compounds against 242 diverse yeast gene deletion strains to generate an extended chemical-genetic matrix (CGM) of 492,126 chemical-gene interaction measurements. This CGM dataset contained 1,434 genotype-specific inhibitors, termed cryptagens. We selected 128 structurally diverse cryptagens and tested all pairwise combinations to generate a benchmark dataset of 8,128 pairwise chemical-chemical interaction tests for synergy prediction, termed the cryptagen matrix (CM). An accompanying database resource called ChemGRID was developed to enable analysis, visualisation and downloads of all data. The CGM and CM datasets will facilitate the benchmarking of computational approaches for synergy prediction, as well as chemical structure-activity relationship models for anti-fungal drug discovery.

  9. Chemical substructure analysis in toxicology

    SciTech Connect

    Beauchamp, R.O. Jr.

    1990-12-31

    A preliminary examination of chemical-substructure analysis (CSA) demonstrates the effective use of the Chemical Abstracts compound connectivity file in conjunction with the bibliographic file for relating chemical structures to biological activity. The importance of considering the role of metabolic intermediates under a variety of conditions is illustrated, suggesting structures that should be examined that may exhibit potential activity. This CSA technique, which utilizes existing large files accessible with online personal computers, is recommended for use as another tool in examining chemicals in drugs. 2 refs., 4 figs.

  10. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Campbell, A. G.; Johnson, R. E.; Kenty, J. L.; Moudy, L. A.; Shaw, G. L.; Simpson, W. I.; Yang, J. J.

    1978-01-01

    The objective was to investigate and develop chemical vapor deposition (CVD) techniques for the growth of large areas of Si sheet on inexpensive substrate materials, with resulting sheet properties suitable for fabricating solar cells that would meet the technical goals of the Low Cost Silicon Solar Array Project. The program involved six main technical tasks: (1) modification and test of an existing vertical-chamber CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures, using impurity diffusion and other standard and near-standard processing techniques supplemented late in the program by the in situ CVD growth of n(+)/p/p(+) sheet structures subsequently processed into experimental cells.

  11. Enhancing chemical reactions

    DOEpatents

    Morrey, John R.

    1978-01-01

    Methods of enhancing selected chemical reactions. The population of a selected high vibrational energy state of a reactant molecule is increased substantially above its population at thermal equilibrium by directing onto the molecule a beam of radiant energy from a laser having a combination of frequency and intensity selected to pump the selected energy state, and the reaction is carried out with the temperature, pressure, and concentrations of reactants maintained at a combination of values selected to optimize the reaction in preference to thermal degradation by transforming the absorbed energy into translational motion. The reaction temperature is selected to optimize the reaction. Typically a laser and a frequency doubler emit radiant energy at frequencies of .nu. and 2.nu. into an optical dye within an optical cavity capable of being tuned to a wanted frequency .delta. or a parametric oscillator comprising a non-centrosymmetric crystal having two indices of refraction, to emit radiant energy at the frequencies of .nu., 2.nu., and .delta. (and, with a parametric oscillator, also at 2.nu.-.delta.). Each unwanted frequency is filtered out, and each desired frequency is focused to the desired radiation flux within a reaction chamber and is reflected repeatedly through the chamber while reactants are fed into the chamber and reaction products are removed therefrom.

  12. Chemical Stockpile Disposal Program

    SciTech Connect

    Krummel, J.R.; Policastro, A.J.; Olshansky, S.J.; McGinnis, L.D.

    1990-10-01

    As part of the Chemical Stockpile Disposal Program mandated by Public Law 99--145 (Department of Defense Authorization Act), an independent review is presented of the US Army Phase I environmental report for the disposal program at the Pine Bluff Arsenal (PBA) in Arkansas. The Phase I report addressed new and additional concerns not incorporated in the final programmatic environmental impact statement (FPEIS). Those concerns were addressed by examining site-specific data for the PBA and by recommending the scope and content of a more detailed site- specific study. This dependent review evaluates whether the new site-specific data presented in the Phase I report would alter the decision in favor of on-site disposal that was reached in the FPEIS, and whether the recommendations for the scope and content of the site-specific study are adequate. Based on the methods and assumptions presented in the FPEIS, the inclusion of more detailed site-specific data in the Phase I report does not change the decision reached in the FPEIS (which favored on-site disposal at PBA). It is recommended that alternative assumptions about meteorological conditions be considered and that site-specific data on water, ecological, socioeconomic, and cultural resources, and emergency planning and preparedness be considered explicitly in the site-specific EIS decision-making process. 13 refs., 1 fig.

  13. Chemical Stockpile Disposal Program

    SciTech Connect

    Krummel, J.R.; Policastro, A.J.; Olshansky, S.J.; McGinnis, L.D.

    1990-10-01

    As part of the Chemical Stockpile Disposal Program mandated by Public Law 99--145 (Department of Defense Authorization Act), an independent review is presented of the US Army Phase I environmental report for the disposal program at the Umatilla Depot Activity (UMDA) in Hermiston, Oregon. The Phase I report addressed new and additional concerns not incorporated in the final programmatic environmental impact statement (FPEIS). Those concerns were addressed by examining site-specific data for the Umatilla Depot Activity and by recommending the scope and content of a more detailed site-specific study. This independent review evaluates whether the new site-specific data presented in the Phase I report would alter the decision in favor of on-site disposal that was reached in the FPEIS, and whether the recommendations for the scope and content of the site-specific study are adequate. Based on the methods and assumptions presented in the FPEIS, the inclusion of more detailed site-specific data in the Phase I report does not change the decision reached in the FPEIS (which favored on-site disposal at UMDA). It is recommended that alternative assumptions about meteorological conditions be considered and that site-specific data on water, ecological, socioeconomic, and cultural resources; seismicity; and emergency planning and preparedness be considered explicitly in the site-specific EIS decision-making process. 7 refs., 1 fig.

  14. Chemical communication in bacteria

    NASA Astrophysics Data System (ADS)

    Suravajhala, Srinivasa Sandeep; Saini, Deepak; Nott, Prabhu

    Luminescence in Vibrio fischeri is a model for quorum-sensing-gene-regulation in bacteria. We study luminescence response of V. fischeri to both internal and external cues at the single cell and population level. Experiments with ES114, a wild-type strain, and ainS mutant show that luminescence induction in cultures is not always proportional to cell-density and there is always a basal level of luminescence. At any given concentration of the exogenously added signals, C6-HSL and C8-HSL, luminescence per cell reaches a maximum during the exponential phase and decreases thereafter. We hypothesize that (1) C6-HSL production and LuxR activity are not proportional to cell-density, and (2) there is a shift in equilibrium from C6-HSL to C8-HSL during the later stages of growth of the culture. RT-PCR analysis of luxI and luxR shows that the expression of these genes is maximum corresponding to the highest level of luminescence. The shift in equilibrium is shown by studying competitive binding of C6-HSL and C8-HSL to LuxR. We argue that luminescence is a unicellular behaviour, and an intensive property like per cell luminescence is more important than gross luminescence of the population in understanding response of bacteria to chemical signalling. Funding from the Department of Science and Technology, India is acknowledged.

  15. Beyond new chemical entities

    PubMed Central

    Caoili, Salvador Eugenio C; Caoili, Salvador Eugenio C

    2014-01-01

    Antibody-type agents (i.e., antibodies and derivatives thereof) may be produced as clinically valuable antidotes, which conceivably could be developed in tandem with prospective new pharmaceutical products so as to render the risks of clinical trials more acceptable from a regulatory standpoint. Yet, this is but a relatively narrow view of the full potential utility associated with antibody-type agents, the significance of which is appreciated upon reconsidering key aspects of early modern biomedical research (notably major contributions thereto by Nobel Laureate Paul Ehrlich) in light of much more recent advances (e.g., application of immunity-oriented approaches to diseases in general, epitope-specific targeting, abzyme-mediated catalysis, antibody-mediated sustained-release buffering of unbound-ligand concentrations, and enhanced thermal and metabolic stability of deuterated chemical species via the kinetic isotope effect), as conditioned by health-related concerns (e.g., current and anticipated epidemiologic transitions vis-a-vis environmental changes) especially with regard to sustainable development (e.g., emphasizing more efficient resource utilization toward increased global resilience based on greater independence from high-maintenance technological infrastructure). The broader view that thus emerges highlights the urgent need to rebalance the health-research agenda, which presently reflect an overemphasis on small-molecule candidate-drug discovery, in order to advance health based on a comprehensive fundamental synthesis of immunity and pharmacology. PMID:24632567

  16. Strength of Chemical Bonds

    NASA Technical Reports Server (NTRS)

    Christian, Jerry D.

    1973-01-01

    Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.

  17. Chemicals in Classrooms. Pesticides and Maintenance Chemicals in Vermont Schools.

    ERIC Educational Resources Information Center

    Sterling, Peter; Browning, Brigid

    This report is the second in a series of studies on the serious threat toxic chemical use may pose to the health of Vermont's children, teachers, and school staff. The first report, "Toxic Chemical Exposure in Schools: Our Children at Risk," provided an overview of the problem of poor indoor air quality (IAQ) in schools and discussed…

  18. Safety in the Chemical Laboratory. Safety Course for Chemical Technologists.

    ERIC Educational Resources Information Center

    Simpson, Kathleen A.

    1987-01-01

    Describes two courses in chemical safety required as a part of a two-year program in chemical technology offered by the Northern Alberta Institute of Technology (Canada). Lists the topics covered in each course. Provides descriptions of hand-outs, audiovisual materials, demonstrations, assignments, and examinations used in the courses. (TW)

  19. Chemical Mixtures: Considering the Evolution of Toxicology and Chemical Assessment

    PubMed Central

    Monosson, Emily

    2005-01-01

    The assessment of chemical mixtures is a complex topic for toxicologists, regulators, and the public. In this article the linkage between the science of toxicology and the needs of governmental regulatory agencies in the United States is explored through an overview of environmental regulations enacted over the past century and a brief history of modern toxicology. One of the goals of this overview is to encourage both regulators and scientists to consider the benefits and limitations of this science–regulatory relationship as they tackle existing issues such as chemical mixtures. It is clear that a) over the past 100 years chemical regulation and toxicologic research, have in large part, shared a common emphasis on characterization and regulation of individual chemicals. But chemical mixtures have been, and continue to be, evaluated at hazardous waste sites around the United States. For this reason the current U.S. Environmental Protection Agency guidelines for chemical mixtures assessment are also reviewed. These guidelines highlight the current practice of mixtures assessment, which relies primarily on the existing single-chemical database. It is also clear that b) the science and assessment of chemical mixtures are moving forward through the combined efforts of regulatory agencies and scientists from a broad range of disciplines, including toxicology. Because toxicology is at this exciting crossroads, particular attention should be paid to the forces (e.g., public demands, regulatory needs, funding, academic interests) that both promote and limit the growth of this expanding discipline. PMID:15811826

  20. 78 FR 16698 - Chemical Facility Anti-Terrorism Standards (CFATS) Chemical-Terrorism Vulnerability Information...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... SECURITY Chemical Facility Anti-Terrorism Standards (CFATS) Chemical- Terrorism Vulnerability Information... Collection Request, Chemical Facility Anti- Terrorism Standards (CFATS) Chemical-terrorism Vulnerability... chemical facilities. On April 9, 2007, the Department issued an Interim Final Rule (IFR), implementing...

  1. Toxicokinetic Triage for Environmental Chemicals.

    PubMed

    Wambaugh, John F; Wetmore, Barbara A; Pearce, Robert; Strope, Cory; Goldsmith, Rocky; Sluka, James P; Sedykh, Alexander; Tropsha, Alex; Bosgra, Sieto; Shah, Imran; Judson, Richard; Thomas, Russell S; Setzer, R Woodrow

    2015-09-01

    Toxicokinetic (TK) models link administered doses to plasma, blood, and tissue concentrations. High-throughput TK (HTTK) performs in vitro to in vivo extrapolation to predict TK from rapid in vitro measurements and chemical structure-based properties. A significant toxicological application of HTTK has been "reverse dosimetry," in which bioactive concentrations from in vitro screening studies are converted into in vivo doses (mg/kg BW/day). These doses are predicted to produce steady-state plasma concentrations that are equivalent to in vitro bioactive concentrations. In this study, we evaluate the impact of the approximations and assumptions necessary for reverse dosimetry and develop methods to determine whether HTTK tools are appropriate or may lead to false conclusions for a particular chemical. Based on literature in vivo data for 87 chemicals, we identified specific properties (eg, in vitro HTTK data, physico-chemical descriptors, and predicted transporter affinities) that correlate with poor HTTK predictive ability. For 271 chemicals we developed a generic HT physiologically based TK (HTPBTK) model that predicts non-steady-state chemical concentration time-courses for a variety of exposure scenarios. We used this HTPBTK model to find that assumptions previously used for reverse dosimetry are usually appropriate, except most notably for highly bioaccumulative compounds. For the thousands of man-made chemicals in the environment that currently have no TK data, we propose a 4-element framework for chemical TK triage that can group chemicals into 7 different categories associated with varying levels of confidence in HTTK predictions. For 349 chemicals with literature HTTK data, we differentiated those chemicals for which HTTK approaches are likely to be sufficient, from those that may require additional data.

  2. Simulations of chemical catalysis

    NASA Astrophysics Data System (ADS)

    Smith, Gregory K.

    This dissertation contains simulations of chemical catalysis in both biological and heterogeneous contexts. A mixture of classical, quantum, and hybrid techniques are applied to explore the energy profiles and compare possible chemical mechanisms both within the context of human and bacterial enzymes, as well as exploring surface reactions on a metal catalyst. A brief summary of each project follows. Project 1 - Bacterial Enzyme SpvC The newly discovered SpvC effector protein from Salmonella typhimurium interferes with the host immune response by dephosphorylating mitogen-activated protein kinases (MAPKs) with a beta-elimination mechanism. The dynamics of the enzyme substrate complex of the SpvC effector is investigated with a 3.2 ns molecular dynamics simulation, which reveals that the phosphorylated peptide substrate is tightly held in the active site by a hydrogen bond network and the lysine general base is positioned for the abstraction of the alpha hydrogen. The catalysis is further modeled with density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31 G(d,p) level of theory. The truncated model suggested the reaction proceeds via a single transition state. After including the enzyme environment in ab initio QM/MM studies, it was found to proceed via an E1cB-like pathway, in which the carbanion intermediate is stabilized by an enzyme oxyanion hole provided by Lys104 and Tyr158 of SpvC. Project 2 - Human Enzyme CDK2 Phosphorylation reactions catalyzed by kinases and phosphatases play an indispensable role in cellular signaling, and their malfunctioning is implicated in many diseases. Ab initio quantum mechanical/molecular mechanical studies are reported for the phosphoryl transfer reaction catalyzed by a cyclin-dependent kinase, CDK2. Our results suggest that an active-site Asp residue, rather than ATP as previously proposed, serves as the general base to activate the Ser nucleophile. The corresponding transition state features a

  3. Titan's chemical complexity

    NASA Astrophysics Data System (ADS)

    Vuitton, Veronique

    2012-04-01

    We review here our current knowledge of Titan's gas phase chemistry. We base our discussion on photochemical models as well as on laboratory experiments. We identify the lower mass positive [1,2] and negative [3] ions detected in the upper atmosphere and we show that their formation is a direct consequence of the presence of heavy neutrals. We demonstrate that the observed densities of CO, CO2 and H2O can be explained by a combination of exogenous O, and OH/H2O input [4]. We argue that benzene [5] and ammonia [6] are created in the upper atmosphere through complex chemical processes involving both neutral and ion chemistry. These species diffuse downward where they are at the origin of heavier aromatics and amines, respectively. Finally, we discuss the impact on hydrocarbon densities of recent theoretical calculations of the rate constants of association reactions [7]. [1] V. Vuitton, R. V. Yelle and V. G. Anicich, Astrophys. J., 647, L175 (2006). [2] V. Vuitton, R. V. Yelle and M. J. McEwan, Icarus, 191, 722 (2007). [3] V. Vuitton, P. Lavvas, R. V. Yelle, M. Galand, A. Wellbrock, G. R. Lewis, A. J. Coates and J.-E. Wahlund, Planet. Space Sci., 57, 1558 (2009). [4] S. M. Hörst, V. Vuitton, and R. V. Yelle, J. Geophys. Res., 113, E10006 (2008). [5] V. Vuitton, R. V. Yelle and J. Cui, J. Geophys. Res., 113, E05007 (2008). [6] R. V. Yelle, V. Vuitton, P. Lavvas, S. J. Klippenstein, M. A. Smith, S. M. Hörst and J. Cui, Faraday Discuss., 147, 31 (2010). [7] V. Vuitton, R. V. Yelle, S. J. Klippenstein and P. Lavvas, Astrophys. J., in press.

  4. Chemical earth models

    NASA Astrophysics Data System (ADS)

    Javoy, Marc

    1999-10-01

    This article presents a critical review of method, concepts and prejudices used bv modelists of the Earth's chemical composition over approximate the last fifty years and of the resulting compositions. Brief descriptions are given of admitted accretion mechanisms, of the starting materials most often considered and of the major parameters and recurrent concepts: 'reduced" state, mantle homogeneity vs heterogeneity, 'low pressure' core formation, 'great impact', refractory, lithophile, siderophile, compatible, incompatible character of elements, depleted and degassed mantle, Urey ratio, as well as the description of a commonly-used instrument, possibly harmful to Iogic, the famous Ockham's razor. Differences between models are now restricted to the lower mantle composition:the 'primary' (before crust differentiation) upper mentle varies little from model to model and the idea of a 10-15% combined Si-O-S concentration as representing the necessary light elements in the core is gaining more and more ground. The dominant type of model derives more or less directly from the CI cabonaceous composition by complete devolatilization and reduction. Its mantle is homogeneous and convecting mainly in a one-level mode, in accordence with dominant geophysicists' views but in rather strong disagreement with geochemical data and models which insist on the strong decoupling between lower and upper mantle. Its low Si excess is generally supposed to have been absorbed by the core, whereas its high refractory lithophile element (RLE) content creates mass balance problems relative to presently observed mantle and crust concentrations. The alternative type is a two-lavel mantle with a Si and Fe-rich, RLE-poor, lower mantle, previously based mainly on seismic and mineral physics data, and now also on geochemical and cosmochemical arguments.

  5. Chemical Information: Print. Directed Study.

    ERIC Educational Resources Information Center

    Stone, Catherine C.

    This report provides a survey and evaluation of chemical information literature. Contained in this survey are an overview of the chemical literature field, comments on obtaining access to this literature and annotated bibliographies of primary, secondary, and tertiary sources as well as special topics. Primary sources include journals, patents,…

  6. Chemical modification of semiconductor surfaces

    NASA Technical Reports Server (NTRS)

    Finklea, H. O.

    1981-01-01

    Results of research on the chemical modification of TiO2 powders in the gas phase and the examination of the modified powders by infrared absorption spectroscopy are comprehensively summarized. The range of information obtainable by IR spectroscopy of chemically modified semiconductors, and a definition of the optimum reaction conditions for synthesizing a monolayer of methylsilanes using vapor phase reaction conditions were considered.

  7. Reduction of chemical reaction models

    NASA Technical Reports Server (NTRS)

    Frenklach, Michael

    1991-01-01

    An attempt is made to reconcile the different terminologies pertaining to reduction of chemical reaction models. The approaches considered include global modeling, response modeling, detailed reduction, chemical lumping, and statistical lumping. The advantages and drawbacks of each of these methods are pointed out.

  8. Modern Chemical Technology, Volume 3.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume contains chapters 14-18 for the ACS "Modern Chemical Technology" (ChemTeC) instructional material which is intended to prepare chemical technologists. The content concentrates on the background needed to understand the periodic table; names of inorganic compounds; structures, names and classes of common organic material; chemistry and…

  9. Optical waveguides for chemical sensing

    NASA Astrophysics Data System (ADS)

    Burgess, Lloyd W.

    1992-07-01

    Possibilities of employing thin film optical waveguides for chemical analysis are reviewed. Particular attention is given to the use of integrated or planar optical elements in sensors which may be applied to continuous or in situ monitoring in biomedical, environmental, and chemical processes.

  10. Modern Chemical Technology, Volume 1.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is the first in a series of the ACS "Modern Chemical Technology" (ChemTeC) curriculum which is to prepare chemical technicians. The chapters concentrate on gas chromatography, tests for purity, properties of gases, and gas measurements. Included is the appropriate content, exercises, laboratory activities, and all needed mathematics.…

  11. Chemical Compatibility of Polymeric Materials.

    ERIC Educational Resources Information Center

    Solen, Kenneth A.; Kuchar, Marvin C.

    1990-01-01

    Presents some principles for specifying general classes of polymers for predicting relative chemical attack from acids, bases, oxidants, and certain common antagonists. Also discusses predicting relative solvent effects. Suggests uses of this information in two or three lectures in a chemical engineering materials course. (YP)

  12. Developmental neurotoxicity of industrial chemicals.

    PubMed

    Grandjean, P; Landrigan, P J

    2006-12-16

    Neurodevelopmental disorders such as autism, attention deficit disorder, mental retardation, and cerebral palsy are common, costly, and can cause lifelong disability. Their causes are mostly unknown. A few industrial chemicals (eg, lead, methylmercury, polychlorinated biphenyls [PCBs], arsenic, and toluene) are recognised causes of neurodevelopmental disorders and subclinical brain dysfunction. Exposure to these chemicals during early fetal development can cause brain injury at doses much lower than those affecting adult brain function. Recognition of these risks has led to evidence-based programmes of prevention, such as elimination of lead additives in petrol. Although these prevention campaigns are highly successful, most were initiated only after substantial delays. Another 200 chemicals are known to cause clinical neurotoxic effects in adults. Despite an absence of systematic testing, many additional chemicals have been shown to be neurotoxic in laboratory models. The toxic effects of such chemicals in the developing human brain are not known and they are not regulated to protect children. The two main impediments to prevention of neurodevelopmental deficits of chemical origin are the great gaps in testing chemicals for developmental neurotoxicity and the high level of proof required for regulation. New, precautionary approaches that recognise the unique vulnerability of the developing brain are needed for testing and control of chemicals.

  13. Modern Chemical Technology, Volume 7.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: the nature of reversible processes, equilibrium constants, variable reaction tendencies, practical…

  14. Chemicals: What's in? What's out?

    ERIC Educational Resources Information Center

    Roy, Ken

    2004-01-01

    Chemistry should be fun and exciting, but much preparation and skill are needed by the teacher and students in working with chemicals. Unfortunately, accidents do happen and things can blow up, but these incidents can help be prevented by knowing and following proper safety procedures. Knowing which chemicals are appropriate for the middle level…

  15. Modern Chemical Technology, Volume 9.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: ion exchange, electrphoresis, dialysis, electrochemistry, corrosion, electrolytic cells, coulometry,…

  16. Teaching Chemical Engineers about Teaching

    ERIC Educational Resources Information Center

    Heath, Daniel E.; Hoy, Mary; Rathman, James F.; Rohdieck, Stephanie

    2013-01-01

    The Chemical and Biomolecular Engineering Department at The Ohio State University in collaboration with the University Center for the Advancement of Teaching developed the Chemical Engineering Mentored Teaching Experience. The Mentored Teaching Experience is an elective for Ph.D. students interested in pursuing faculty careers. Participants are…

  17. Students' Conceptions of Chemical Change.

    ERIC Educational Resources Information Center

    Hesse, Joseph J., III; Anderson, Charles W.

    1992-01-01

    Presents results of intensive clinical interviews with 11 high school chemistry students representing a broad range of achievement levels as selected from 180 students who completed a written test upon completion of an instructional unit on chemical change. Results indicate that students commonly experience difficulties in chemical knowledge,…

  18. Modern Chemical Technology, Volume 2.

    ERIC Educational Resources Information Center

    Pecsok, Robert L.; Chapman, Kenneth

    This volume contains chapters 8 to 13 of the ACS "Modern Chemical Technology" (ChemTeC) curriculum material which is intended to prepare chemical technologists. The content is centered around the background needed to understand the structure of the atom, covalence, electrovalence, elements and compounds, liquids and solutions, and chemical…

  19. Chemical Control of Plant Growth.

    ERIC Educational Resources Information Center

    Agricultural Research Center (USDA), Beltsville, MD.

    Seven experiments are presented in this Science Study Aid to help students investigate the control of plant growth with chemicals. Plant growth regulators, weed control, and chemical pruning are the topics studied in the experiments which are based on investigations that have been and are being conducted at the U. S. Agricultural Research Center,…

  20. Chemicals from Cradle to Grave

    ERIC Educational Resources Information Center

    Science Scope, 2005

    2005-01-01

    About two years ago, an urban school district had planned for the disposal of some hazardous chemicals. It contracted with a chemical recycling company that was considered to be reputable. The school district, along with several other companies, was charged and fined by the Environmental Protection Agency for improperly releasing hazardous…

  1. Chemical Waste and Allied Products.

    PubMed

    Hung, Yung-Tse; Aziz, Hamidi Abdul; Yusoff, Mohd Suffian; Kamaruddin, Mohamad Anuar; Yeh, Ruth Yu-Li; Liu, Lian-Huey; Huhnke, Christopher Robert; Fu, Yen-Pei

    2015-10-01

    This review of literature published in 2014 focuses on waste related to chemical and allied products. The topics cover the waste management practices, hospital waste, pesticide waste, chemical wastewater, pesticide wastewater and pharmaceutical wastewater. The other topics include aerobic treatment, anaerobic treatment, sorption and ozonation.

  2. Job Prospects for Chemical Engineers.

    ERIC Educational Resources Information Center

    Basta, Nicholas

    1985-01-01

    The job situation for new chemical engineers with bachelor's degrees is continuing to reflect the gradual improvement that began in 1983. However, companies are looking for graduates with technical expertise as well as marketing, sales, or communications skills. Smaller classes may lead to shortages of chemical engineering graduates in the future.…

  3. EXPANDING CHEMICAL-TOXICITY INFORMATION ...

    EPA Pesticide Factsheets

    We find that the connection between structure and biological response is not symmetric, with biological response better at predicting chemical structure than vice versa. *ToxCast Toxicity Reference Database. We find that the connection between structure and biological response is not symmetric, with biological response better at predicting chemical structure than vice versa. *ToxCast Toxicity Reference Database.

  4. Making Models of Chemical Compounds.

    ERIC Educational Resources Information Center

    Hoehn, Robert G.

    1992-01-01

    Describes the benefits and techniques of having students create models of chemical compounds. This hands-on approach uses colored paper and other inexpensive materials to construct the models. A step-by-step approach provides objectives, materials, an explanation on how to calculate chemical ratios, procedures, follow-up activities, and a resource…

  5. Mathematical Modeling of Chemical Stoichiometry

    ERIC Educational Resources Information Center

    Croteau, Joshua; Fox, William P.; Varazo, Kristofoland

    2007-01-01

    In beginning chemistry classes, students are taught a variety of techniques for balancing chemical equations. The most common method is inspection. This paper addresses using a system of linear mathematical equations to solve for the stoichiometric coefficients. Many linear algebra books carry the standard balancing of chemical equations as an…

  6. Chemical Soil Physics Phenomena for Chemical Sensing of Buried UXO

    SciTech Connect

    Phelan, James, M.; Webb, Stephen W.

    1999-06-14

    Technology development efforts are under way to apply chemical sensors to discriminate inert ordnance and clutter from live munitions that remain a threat to reutilization of military ranges. However, the chemical signature is affected by multiple environmental phenomena that can enhance or reduce its presence and transport behavior, and can affect the distribution of the chemical signature in the environment. For example, the chemical can be present in the vapor, aqueous, and solid phases. The distribution of the chemical among these phases, including the spatial distribution, is key in designing appropriate detectors, e.g., gas, aqueous or solid phase sampling instruments. A fundamental understanding of the environmental conditions that affect the chemical signature is needed to describe the favorable and unfavorable conditions of a chemical detector based survey to minimize the consequences of a false negative. UXO source emission measurements are being made to estimate the chemical flux from a limited set of ordnance items. Phase partitioning analysis has been completed to show what the expected concentrations of chemical analytes would be fi-om total concentrations measured in the soil. The soil moisture content in the dry region has been shown to be critical in the attenuation of soil gas concentrations by increased sorption to soil particles. Numerical simulation tools have been adapted to include surface boundary conditions such as solar radiation, surface boundary layer (which is a function of wind speed), precipitation and evaporation, and plant cover/root density to allow transport modeling and evaluate long term processes. Results of this work will provide performance targets for sensor developers and support operational decisions regarding field deployments.

  7. Chemical Mapping of Vesta

    NASA Technical Reports Server (NTRS)

    Prettyman, Thomas H.; Mittlefehldt, D. W.; Yamashita, N.; Lawrence, D. J.; Beck, A. W.; McSween, H. Y.; Feldman, W. C.; McCoy, T. J.; Titus, T. N.; Toplis, M. J.; Reedy, R. C.; Forni, O.; Mizzon, H.; Peplowski, P. N.; Raymond, C. A.; Russell, C. T.

    2012-01-01

    Vesta s surface mineralogy and composition have been studied for decades via telescopic spectroscopy and laboratory analyses of the howardite, eucrite, and diogenite (HED) meteorites, which are thought to originate from Vesta. Visible and infrared reflectance measurements by Dawn have broadly confirmed the paradigm established by Earth-based work, strengthening the Vesta-HED connection. The Dawn mission has achieved a milestone by completing the first chemical measurements of a main-belt asteroid using nuclear spectroscopy. Dawn s Gamma Ray and Neutron Detector (GRaND) has globally mapped the composition of Vesta, including the portions of the northern hemisphere not illuminated by solar radiation. GRaND is sensitive to the composition of the bulk regolith to depths of several decimeters. Abundances and/or detection limits for specific elements and elemental ratios, such as H, Fe, Si, Fe/O, Fe/Si, and K, have been measured. Variations in the average atomic mass and neutron macroscopic absorption cross section have been characterized. The measurements constrain the relative proportions of HED whole-rock end-members, providing measurements of the pyroxene and plagioclase content of the regolith, thereby constraining the processes underlying Vesta s differentiation and crustal evolution. The spatial resolution of GRaND is sufficient to determine basin-average compositions of Veneneia and Rheasilvia, which may contain outcrops of Vesta s olivine-rich mantle. While the elemental composition of Vesta s regolith is similar to the meteorites, there are notable departures from HED whole-rock compositions. While these differences are not sufficient to topple the Vesta-HED paradigm, they provide insight into global-scale processes that have shaped Vesta s surface. Questions addressed by the analysis of GRaND data include: (i) Is Vesta the source of the Fe-rich mesosiderites? (ii) Are evolved, igneous lithologies present on Vesta s surface? (iii) What are the origins of

  8. Chemically enabled nanostructure fabrication

    NASA Astrophysics Data System (ADS)

    Huo, Fengwei

    The first part of the dissertation explored ways of chemically synthesizing new nanoparticles and biologically guided assembly of nanoparticle building blocks. Chapter two focuses on synthesizing three-layer composite magnetic nanoparticles with a gold shell which can be easily functionalized with other biomolecules. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, while maintaining the magnetic properties of the Fe3O4 inner shell. Chapter three describes a new method for synthesizing nanoparticles asymmetrically functionalized with oligonucleotides and the use of these novel building blocks to create satellite structures. This synthetic capability allows one to introduce valency into such structures and then use that valency to direct particle assembly events. The second part of the thesis explored approaches of nanostructure fabrication on substrates. Chapter four focuses on the development of a new scanning probe contact printing method, polymer pen lithography (PPL), which combines the advantages of muCp and DPN to achieve high-throughput, flexible molecular printing. PPL uses a soft elastomeric tip array, rather than tips mounted on individual cantilevers, to deliver inks to a surface in a "direct write" manner. Arrays with as many as ˜11 million pyramid-shaped pens can be brought into contact with substrates and readily leveled optically in order to insure uniform pattern development. Chapter five describes gel pen lithography, which uses a gel to fabricate pen array. Gel pen lithography is a low-cost, high-throughput nanolithography method especially useful for biomaterials patterning and aqueous solution patterning which makes it a supplement to DPN and PPL. Chapter 6 shows a novel form of optical nanolithography, Beam Pen Lithography (BPL), which uses an array of NSOM pens to do nanoscale optical

  9. Swift's Christmas Burst From Blue Supergiant Star Explosion

    NASA Video Gallery

    GRB 101225A, better known as the "Christmas burst," was an unusually long-lasting gamma-ray burst. Because its distance was not measured, astronomers came up with two radically different interpreta...

  10. Atmospheric accelerations and the stability of dynamic supergiant atmospheres.

    NASA Astrophysics Data System (ADS)

    Nieuwenhuijzen, H.; de Jager, C.

    1995-10-01

    The goal of this paper is to study instability regions in the HR diagram, through a calculation of the atmospheric accelerations for spherically symmetric stars, in dynamic equilibrium, without using detailed atmospheric models. The input data are five primary data, viz.: the stellar luminosity L, the effective temperature T_eff_, the mass M, the rate of mass loss ˙(M), and the microturbulent velocity component ζmu_, while we assume the temperature for a reference atmospheric layer, an assumption that appears not to be critical. An iterative solution of the momentum equation, simultaneous with some other equations, yields values for the various accelerations acting on a stellar atmosphere and their algebraic sum g_eff_', the predicted effective acceleration. In the first part of the paper we compare this latter quantity with the g_eff_-value derived observationally from spectral studies of nine program stars and we find overall fair agreement. This supports the method as well as the values of the five input data. In part 2 we determine g'_eff_ in same way for the whole upper part of the Hertzsprung-Russell diagram by using statistical primary data on the mass (based on evolutionary calculations), on mass-loss and on microturbulence (shock-strengths). We find as a fairly general rule that, as stars move along their evolutionary track, and for time scales longer than the dynamic time scale of the atmosphere, the atmosphere continuously adapts to the new (L,T_eff_)-values and essentially remains stable. Current practice of determining the stability limit of stellar atmospheres by extrapolating hydrostatic models to the Eddington limit is not justified by this study. There is one exception: we find a small area around T_eff_=8300K and log(L/Lsun_)=5.7, where no solution is possible for evolved stars on their blueward evolutionary track; the stars in this area have in any case effective accelerations <1mm/s^2^: the "Yellow Evolutionary Void". In the third part we estimate approximately the pulsational (in-)stability of stars in the upper part of the Hertzsprung-Russell diagram, by comparing the g'_eff_ values determined in part 2 with the average outward pulsational acceleration. We thus confirm the 'Yellow Evolutionary Void' for blueward evolving stars, and also find an instability region for blueward evolving stars in the area occupied by the Wolf-Rayet stars. This seems to agree with the observations that the low-temperature boundary of the Yellow Evolutionary Void appears to coincide with the region where the yellow hypergiants are clustering. The yellow hypergiants are therefore interpreted as blueward moving stars with ZAMS masses of about 25-40Msun_, and actual masses between 15 and 25Msun_. For our galaxy it is found that only a few stars are situated within the 'Yellow Evolutionary Void', in accordance with our expectation.

  11. Infrared observations of circumstellar ammonia in OH/IR supergiants

    NASA Technical Reports Server (NTRS)

    Mclaren, R. A.; Betz, A. L.

    1980-01-01

    Ammonia has been detected in the circumstellar envelopes of VY Canis Majoris, VX Sagittarii, and IRC +10420 by means of several absorption lines in the nu-2 vibration-rotation band near 950 kaysers. The line profiles are well resolved (0.2 km/sec resolution) and show the gas being accelerated to terminal expansion velocities near 30 km/sec. The observations reveal a method for determining the position of the central star on VLBI maps of OH maser emission to an accuracy of approximately 0.2 arcsec. A firm lower limit of 2 x 10 to the 15th/sq cm is obtained for the NH3 column density in VY Canis Majoris.

  12. Safety in the Chemical Laboratory. Laboratory Chemical Reports: The First Step in Chemical Safety.

    ERIC Educational Resources Information Center

    Renfrew, Malcolm M., Ed.; Tenpas, Carl J.

    1980-01-01

    Describes a prelab activity, the chemistry report, that acquaints college students with the nature of the chemical(s) they are using in the laboratory. Methodology, experimental procedures and safety rules are emphasized, with particular emphasis on potential hazards, safety requirements and emergency procedures. (CS)

  13. Safety, security and dual-use chemicals

    DOE PAGES

    Walters, Douglas B.; Ho, Pauline; Hardesty, Jasper

    2014-12-18

    Many chemicals that are frequently used in laboratories and industries can be harmful if not handled properly. Chemical safety best practices are designed to protect people from accidentally being exposed to hazardous chemicals. On the other hand, chemical security best practices are designed to protect people from someone deliberately exposing others to hazardous chemicals. Finally, many chemical safety best practices overlap with chemical security best practices, but there are important differences, as will be discussed in this paper.

  14. Method of forming a chemical composition

    DOEpatents

    Bingham, Dennis N.; Wilding, Bruce M.; Klingler, Kerry M.; Zollinger, William T.; Wendt, Kraig M.

    2007-10-09

    A method of forming a chemical composition such as a chemical hydride is described and which includes the steps of selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of hydrogen; and exposing the selected composition to an amount of ionizing radiation to encourage the changing of the chemical bonds of the selected composition, and chemically reacting the selected composition with the source of hydrogen to facilitate the formation of a chemical hydride.

  15. FMC: Expanding its chemical universe

    SciTech Connect

    Wood, A.

    1992-12-23

    With a portfolio ranging from defense systems to gold to food machinery - the source of its name - FMC Corp. (Chicago) ranks as a diversified conglomerate. The company's industrial chemicals operation consists of alkali chemicals, chiefly soda ash and derivatives: peroxygen chemicals, made up of hydrogen peroxide and other peroxygens; and phosphorus chemicals. FMC has about a 30% market share in each of these three. It also includes the Foret (Barcelona) division, part of FMC Europe. Moving lithium into FMC's specialties group reflects the R D-intensive nature of many lithium compounds, explains F. Wyman Morgan, director/group technology for the chemical product and specialty chemicals groups. FMC is also involved in collaborative research programs to develop lithium-based batteries and fuel cells. We have a decentralized business-oriented R D focus, Morgan says. The main thrusts in lithium are in developing organolithiums for drug synthesis. FMC also has a major industrial lithium business; it recently added a new butyl lithium unit in Texas and is looking to expand production through the development of lithium deposits in Latin America. But lithium is growing fastest in the downstream areas, says W. Reginald Hall, v.p. and group manager/specialty chemicals group. It has an unbelievable range of uses, he says, including catalytic applications in the pharmaceuticals industry. We are working on lithium compounds that allow you to drop a functional organic group into a molecule in a reliable way.

  16. [Developmental neurotoxicity of industrial chemicals].

    PubMed

    Labie, Dominique

    2007-10-01

    "A Silent Pandemic : Industrial Chemicals Are Impairing the Brain Development of Children Worldwide" Fetal and early childhood exposures to industrial chemicals in the environment can damage the developing brain and can lead to neurodevelopmental disorders (NDDs)--autism, attention deficit disorder (ADHD), and mental retardation. In a new review study, published in The Lancet, Philip Grandjean and Philip Landrigan from the Harvard School of Public Health systematically examined publicly available data on chemical toxicity in order to identify the industrial chemicals that are the most likely to damage the developing brain. The researchers found that 202 industrial chemicals have the capacity to damage the human brain, and they conclude that chemical pollution may have harmed the brains of millions of children worldwide. The authors conclude further that the toxic effects of industrial chemicals on children have generally been overlooked. In North Amercia, the commission for environmental cooperation, and in European Union the DEVNERTOX projects had reached to the same conclusions. We analyse this review and discuss these rather pessimistic conclusions.

  17. Chemical munitions dumped at sea

    NASA Astrophysics Data System (ADS)

    Edwards, Margo; Bełdowski, Jacek

    2016-06-01

    Modern chemical warfare is a byproduct of the industrial revolution, which created factories capable of rapidly producing artillery shells that could be filled with toxic chemicals such as chlorine, phosgene and mustard agent. The trench warfare of World War I inaugurated extensive deployments of modern chemical weapons in 1915. Concomitantly, the need arose to dispose of damaged, captured or excess chemical munitions and their constituents. Whereas today chemical warfare agents (CWA) are destroyed via chemical neutralization processes or high-temperature incineration in tandem with environmental monitoring, in the early to middle 20th century the options for CWA disposal were limited to open-air burning, burial and disposal at sea. The latter option was identified as the least likely of the three to impact mankind, and sea dumping of chemical munitions commenced. Eventually, the potential impacts of sea dumping human waste were recognized, and in 1972 an international treaty, the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, was developed to protect the marine environment from pollution caused by the dumping of wastes and other matter into the ocean. By the time this treaty, referred to as the London Convention, was signed by a majority of nations, millions of tons of munitions were known to have been disposed throughout the world's oceans.

  18. Chemical Safety Alert: Identifying Chemical Reactivity Hazards Preliminary Screening Method

    EPA Pesticide Factsheets

    Introduces small-to-medium-sized facilities to a method developed by Center for Chemical Process Safety (CCPS), based on a series of twelve yes-or-no questions to help determine hazards in warehousing, repackaging, blending, mixing, and processing.

  19. Chemical Safety Alert: Chemical Accidents from Electric Power Outages

    EPA Pesticide Factsheets

    Incident data from the National Response Center (NRC) shows that during 2000 there were about 240 chemical releases reported due to an electric power interruption, as well as resumption/restart; only a few were related to planned rolling blackouts.

  20. Chemical constituents of fugitive dust.

    PubMed

    Van Pelt, R Scott; Zobeck, Ted M

    2007-07-01

    Wind erosion selectively winnows the fine, most chemically concentrated portions of surface soils and results in the inter-regional transport of fugitive dust containing plant nutrients, trace elements and other soil-borne contaminants. We sampled and analyzed surface soils, sediments in transport over eroding fields, and attic dust from a small area of the Southern High Plains of Texas to characterize the physical nature and chemical constituents of these materials and to investigate techniques that would allow relatively rapid, low cost techniques for estimating the chemical constituents of fugitive dust from an eroding field. From chemical analyses of actively eroding sediments, it would appear that Ca is the only chemical species that is enriched more than others during the process of fugitive dust production. We found surface soil sieved to produce a sub-sample with particle diameters in the range of 53-74 microm to be a reasonably good surrogate for fugitive dust very near the source field, that sieved sub-samples with particle diameters <10 microm have a crustal enrichment factor of approximately 6, and that this factor, multiplied by the chemical contents of source soils, may be a reasonable estimator of fugitive PM(10) chemistry from the soils of interest. We also found that dust from tractor air cleaners provided a good surrogate for dust entrained by tillage and harvesting operations if the chemical species resulting from engine wear and exhaust were removed from the data set or scaled back to the average of enrichment factors noted for chemical species with no known anthropogenic sources. Chemical analyses of dust samples collected from attics approximately 4 km from the nearest source fields indicated that anthropogenic sources of several environmentally important nutrient and trace element species are much larger contributors, by up to nearly two orders of magnitude, to atmospheric loading and subsequent deposition than fugitive dust from eroding