Sample records for tepid supergiants chemical

  1. Red Supergiants as Luminous Beacons of Cosmic Chemical Abundances: The Infrared J--Band Spectroscopic Technique

    NASA Astrophysics Data System (ADS)

    Gazak, Jonathan Zachary

    A new spectroscopic method has been developed and tested which, with the advent of the next generation of 30 meter class telescopes, will enable the study of the chemical evolution of galaxies through the spectroscopy of individual red supergiant stars out to the Coma cluster of galaxies. This J--band (1.165-1.215 mum) technique requires modest spectral resolutions of lambda/deltalambda ˜ 3000, enabling multi object spectroscopy using existing 8 meter telescopes (Keck, VLT) and future "extremely large telescopes" such as the Thirty Meter Telescope. We demonstrate the power of the technique and study its limitations with high spectral resolution observations of the galactic h and chi Persei clusters and then set our sights outward. We observe a population of RSGs in M31 using MOSFIRE on Keck and measure the central metallicity and gradient using individual supergiants in NGC 300 at 1.9 Mpc with KMOS on the VLT. Following these successes we demonstrate an extension of the technique by proving that the J--band method is applicable to the integrated light of super star clusters. These distant, massive coeval ensembles of stars present as red supergiants photometrically and spectroscopically when the first such stars evolve after roughly six million years. We provide a photometric technique to select properly aged clusters and apply the technique to two test cases, a super-solar cluster in M83 and a sub-solar cluster in NGC 6946. After the successful applications to those clusters we observed three super star clusters in the Antennae galaxies at 20 Mpc and extract metallicity information from their J--band spectra without difficulty. This application over such a distance is a stunning success for a stellar chemical abundance technique and with it in hand we offer the J--band technique as a powerful new tool for the study of galaxy evolution and the chemical enrichment of a significant volume of the local universe.

  2. 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."

  3. Secular resonant dressed orbital diffusion II : application to an isolated self similar tepid galactic disc

    E-print Network

    Fouvry, Jean-Baptiste

    2015-01-01

    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 v...

  4. The $^{13}$Carbon footprint of B[e] supergiants

    E-print Network

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

    2010-01-01

    We report on the first detection of $^{13}$C enhancement in two B[e] supergiants in the Large Magellanic Cloud. Stellar evolution models predict the surface abundance in $^{13}$C 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] supergiants is hampered by their dense, disk-forming winds, hiding the stars. Recent theoretical computations predict the detectability of enhanced $^{13}$C via the molecular emission in $^{13}$CO arising in the circumstellar disks of B[e] supergiants. To test this potential method and to unambiguously identify a post-main sequence B[e]SG by its $^{13}$CO emission, we have obtained high-quality $K$-band spectra of two known B[e] supergiants 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 $^{13}$CO band emission, whose strength implies ...

  5. 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.

  6. 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 factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in turns of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

  7. 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 differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

  8. Spectral atlas of A-type supergiants

    E-print Network

    Klochkova, V G; Chentsov, E L

    2015-01-01

    Based on high-spectral-resolution observations (R=60000) performed with the 6-m BTA telescope in combination with the echelle spectrograph NES, we have studied the optical spectra of three A-type supergiants: a peculiar supergiant 3 Pup, a post-AGB star BD+48 1220, and a massive $\\alpha$ Cyg, which belong to essentially different stages of evolution. A spectral atlas for these stars is prepared in the wavelength interval of 3920 to 6720 \\AA.

  9. Photospheric velocity gradients in B1 supergiants

    NASA Technical Reports Server (NTRS)

    Massa, D.; Shore, S. N.; Wynne, D.

    1992-01-01

    We present IUE spectra for a set of B1 supergiants. These data clearly demonstrate that the Si III 1300A multiplet (lower level 6.6 ev above ground) becomes progressively more asymmetric with increasing luminosity or, equivalently, mass loss. In the most luminous supergiants, the cores of the 1300A multiplets become displaced by up to -150 km/s relative to nearby, weaker lines. In addition, systematic velocity shifts and asymmetries are also present in the strong Si III singlets 1312A and 1417A in the more luminous stars. The obvious implication of these observations is that the outer photospheres of B supergiants are affected by radial expansion, and this may account for why even non-LTE line analyses of these stars require large micro-turbulent velocity fields, and why line blanketed LTE models underestimate their overall UV line blanketing.

  10. THE TEMPERATURES OF RED SUPERGIANTS

    SciTech Connect

    Davies, Ben [Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom)] [Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Kudritzki, Rolf-Peter; Gazak, Zach [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)] [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Plez, Bertrand [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France)] [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France); Trager, Scott [Kapteyn Institute, University of Groningen, P.O. Box 800, 9700-AV Groningen (Netherlands)] [Kapteyn Institute, University of Groningen, P.O. Box 800, 9700-AV Groningen (Netherlands); Lancon, Ariane [Observatoire Astronomique and CNRS UMR 7550, Universite de Strasbourg, F-67000 Strasbourg (France)] [Observatoire Astronomique and CNRS UMR 7550, Universite de Strasbourg, F-67000 Strasbourg (France); Bergemann, Maria [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)] [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); Evans, Chris [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Chiavassa, Andrea [CNRS Laboratoire Lagrange, Universite de Nice Sophia-Antipolis, Observatoire de la Cote d'Azur, BP 4229, F-06304 Nice Cedex 4 (France)] [CNRS Laboratoire Lagrange, Universite de Nice Sophia-Antipolis, Observatoire de la Cote d'Azur, BP 4229, F-06304 Nice Cedex 4 (France)

    2013-04-10

    We present a re-appraisal of the temperatures of red supergiants (RSGs) using their optical and near-infrared spectral energy distributions (SEDs). We have obtained data of a sample of RSGs in the Magellanic Clouds using VLT+XSHOOTER, and we fit MARCS model atmospheres to different regions of the spectra, deriving effective temperatures for each star from (1) the TiO bands, (2) line-free continuum regions of the SEDs, and (3) the integrated fluxes. We show that the temperatures derived from fits to the TiO bands are systematically lower than the other two methods by several hundred kelvin. The TiO fits also dramatically overpredict the flux in the near-IR, and imply extinctions which are anomalously low compared to neighboring stars. In contrast, the SED temperatures provide good fits to the fluxes at all wavelengths other than the TiO bands, are in agreement with the temperatures from the flux integration method, and imply extinctions consistent with nearby stars. After considering a number of ways to reconcile this discrepancy, we conclude that three-dimensional effects (i.e., granulation) are the most likely cause, as they affect the temperature structure in the upper layers where the TiO lines form. The continuum, however, which forms at much deeper layers, is apparently more robust to such effects. We therefore conclude that RSG temperatures are much warmer than previously thought. We discuss the implications of this result for stellar evolution and supernova progenitors, and provide relations to determine the bolometric luminosities of RSGs from single-band photometry.

  11. Observations of emission lines in M supergiants

    NASA Technical Reports Server (NTRS)

    Lambert, D. L.

    1979-01-01

    Copernicus observations of Mg 2 h and k emission lines from M giants and supergiants are described. Supergiants with extensive circumstellar gas shells show an asymmetric k line. The asymmetry is ascribed to superimposed lines of Fe 1 and Mn 1. The Mg 2 line width fit the Wilson-Bappu relation derived from observations of G and K Stars. Results of correlated ground-based observations include (1) the discovery of K 1 fluorescent emission from the Betelgeuse shell; (2) extimates of the mass-loss rates; and (3) the proposal that silicate dust grains must account for the major fraction of the Si atoms in the Betelgeuse shell.

  12. 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.

  13. Optical Interferometry of Giants and Supergiants

    NASA Astrophysics Data System (ADS)

    Kloppenborg, Brian; van Belle, Gerard

    Over the last several decades optical interferometers have made substantial gains in ability, evolving from simple two-telescope arrays with 10-m baselines that primarily measured the angular diameters of stars, to four- to six-telescope arrays with 300-m baselines that are capable of imaging objects at high spatial resolution (0.3 milli-arcseconds) and high spectral resolution (R ˜ 30, 000). This chapter highlights how optical interferometers have been used during the last three decades to study single and binary systems containing giant and supergiant stars. It reviews diameter measurements and astrometry for single and binary stars, discusses the asymmetric mass-loss processes seen in asymptotic giant-branch stars, shows how resolving stellar disks is helping to solve long-standing problems related to carbon stars, and summarizes some of the state-of-the-art techniques that are now being used to image spots and convective cells on supergiants.

  14. Spectral atlas of A-type supergiants

    NASA Astrophysics Data System (ADS)

    Klochkova, V. G.; Sendzikas, E. G.; Chentsov, E. L.

    2015-01-01

    Using the data from the observations carried out with a high spectral resolution of R = 60 000 at the 6-m BTA telescope in combination with the echelle spectrograph NES, we thoroughly studied the characteristics of the optical spectra of the A supergiants 3 Pup, BD+48°1220, and ? Cyg, which belong to essentially different stages of evolution. A spectral atlas for these stars was compiled in the wavelength interval of 3920 to 6720 Å.

  15. Hidden bipolarity in red supergiant winds

    E-print Network

    A. M. S. Richards; M. R. W. Masheder; H. J. van Langevelde; R. J. Cohen; M. D. Gray; J. A. Yates; P. J. Diamond; W. H. T. Vlemmings; M. Szymczak; K. Murakawa

    2005-01-03

    Many observations of late-type M stars show large near-spherical circumstellar envelopes, yet planetary nebulae and supernova remnants are frequently axisymmetric. We present VLBI and MERLIN observations of masers around the red supergiant S Per which show varying degrees of axisymmetry and a dynamically significant magnetic field. There is no evidence for rotation here or in most similar objects. We examine possible origins of the magnetic field.

  16. 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.

  17. Cool Giants and Supergiants with Hot Companions

    NASA Astrophysics Data System (ADS)

    Parsons, Sidney B.

    We propose to observe middle and late-type giant and supergiant stars whose TD-1 fluxes or ground-based spectra indicate the presence of a hot component. Some of the secondaries are seen weakly in optical spectra but cannot be classified accurately, while others are UV discoveries. The companions apparently lie on the upper main sequence, thus their accurate temperature classifications from the IUE spectra will lead to good estimates of their luminosities. These in turn can be used to derive more accurate luminosities than can now be done for individual giants and supergiants. Since the companions contribute little light in the optical region, ultimately this group can be useful in calibrating the upper end of the Wilson-Bappu relationship. We will pursue an enigma that many giant stars apparently have companions which are too hot for consistency with the primary's spectral classification. Combined with previous observations, this project will yield a total sample of more than 80 giant or supergiant absolute magnitudes, enabling both a firmer statistical base for luminosity calibrations and an opportunity to investigate temperature dependence of such calibrations.

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

    SciTech Connect

    Bergemann, Maria; Kudritzki, Rolf-Peter; Wuerl, Matthias [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, D-85741 Garching (Germany)] [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, D-85741 Garching (Germany); Plez, Bertrand [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France)] [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France); Davies, Ben [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA (United Kingdom)] [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA (United Kingdom); Gazak, Zach, E-mail: mbergema@mpa-garching.mpg.de, E-mail: Matthias.Wuerl@physik.uni-muenchen.de, E-mail: kud@ifa.hawaii.edu, E-mail: zgazak@ifa.hawaii.edu, E-mail: bertrand.plez@univ-montp2.fr, E-mail: bdavies@ast.cam.ac.uk [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)] [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    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.

  19. 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).

  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. Peculiar Type II supernovae from blue supergiants

    NASA Astrophysics Data System (ADS)

    Kleiser, Io K. W.; Poznanski, Dovi; Kasen, Daniel; Young, Timothy R.; Chornock, Ryan; Filippenko, Alexei V.; Challis, Peter; Ganeshalingam, Mohan; Kirshner, Robert P.; Li, Weidong; Matheson, Thomas; Nugent, Peter E.; Silverman, Jeffrey M.

    2011-07-01

    The vast majority of Type II supernovae (SNeII) are produced by red supergiants, but SN 1987A revealed that blue supergiants (BSGs) can produce members of this class as well, albeit with some peculiar properties. This best-studied event revolutionized our understanding of SNe and linking it to the bulk of Type II events is essential. We present here the optical photometry and spectroscopy gathered for SN 2000cb, which is clearly not a standard SNII and yet is not a SN 1987A analogue. The light curve of SN 2000cb is reminiscent of that of SN 1987A in shape, with a slow rise to a late optical peak, but on substantially different time-scales. Spectroscopically, SN 2000cb resembles a normal SNII, but with ejecta velocities that far exceed those measured for SN 1987A or normal SNeII, above 18 000 km s-1 for H? at early times. The red colours, high velocities, late photometric peak and our modelling of this object all point towards a scenario involving the high-energy explosion of a small-radius star, most likely a BSG, producing 0.1 M? of 56Ni. Adding a similar object to the sample, SN 2005ci, we derive a rate of ˜2 per cent of the core-collapse rate for this loosely defined class of BSG explosions.

  2. Non-LTE studies of A-type supergiants

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    The tenuous atmospheres of A-type supergiants are good sources for studying non-LTE physics. We present an overview of recent achievements in quantitative analyses of high-resolution spectra of Galactic A-type supergiants at optical and near-IR wavelengths, focusing on the nature and extent of non-LTE effects. We discuss their impact on determinations of atmospheric and fundamental stellar parameters and element abundances, and draw some conclusions regarding the evolutionary status of A-type supergiants.

  3. Supergiant halos as an integral record of natural pionic radioactivity

    E-print Network

    D. B. Ion; Reveica Ion-Mihai; M. L. Ion; Adriana I. Sandru

    2004-01-09

    In this paper an unified interpretation of the supergiant halos (SGH), discovered by Grady, Walker and Laemmlein, is discussed. So, it is proved that SGH`s can be considered as integral records of the nuclear pionic radioactivity.

  4. Radiation driven wind models for A, F and G supergiants.

    NASA Astrophysics Data System (ADS)

    Achmad, L.; Lamers, H. J. G. L. M.; Pasquini, L.

    1997-04-01

    We investigate the effects of radiation pressure on the atmospheres of A, F and G-supergiants by calculating hydrodynamical model atmospheres for stars with 5500<=T_eff_<=9500K. In the subsonic part of the wind, the radiation pressure by continuum and lines from Kurucz (1992, ATLAS 6 program) is taken into account. In the supersonic part of the wind, the radiation pressure is expressed in terms of the force multiplier formalism (Castor et al. 1975ApJ...195..157C) with the correction for the finite disk taken into account. The temperature structure is from the T(?) relation of blanketed model atmospheres. The predicted mass loss rates of the A-supergiants agrees excellently with the observed values. However the predicted terminal velocities are about a factor 3 higher than observed. We discuss several possible causes for this discrepancy. The most likely one is a change in the force multiplier parameter ? of the line radiation force from about 0.5 in the lower parts of the wind to a much smaller value of about 0.1 throughout most of the wind. This might be the result of a change in the ionization of the wind with distance, or a decoupling of the line driven ions in the wind from the ambient gas. The predicted mass loss rate of the G-type supergiant 22Vul, which is the only G-supergiant with a reliable mass loss rate, is a factor 10^5^ smaller than observed. This is probably due to the fact that G-supergiants have chromospheres, which were not taken into account in our model. Our models for F-supergiants could not be compared with observations because there are no reliable empirical mass loss rates or terminal wind velocities for normal F-supergiants. The F-supergiants ?Cas and HR8752 have highly variable mass loss rates which obviously cannot be explained by our models. We conclude that mass loss from A-type supergiants is most likely due to a line driven wind but that the mass loss from G-supergiants is not. It is interesting to find the spectral type between F0 and G3 where the radiation driven wind models break down and to compare that with the type where the chromospheres become noticeable. The high opacity in the hydrogen ionization zone produces a net outward force in those layers. This gives rise to a pressure inversion in the subsonic part of the atmosphere, but does not lead to high mass loss rates.

  5. New Nitrogen and Carbon in AF-supergiants

    E-print Network

    Kim A. Venn; Norbert Przybilla

    2002-12-11

    The AF-supergiants in the Galaxy and the SMC allow us to examine predictions from evolution models through their CNO abundances. In these proceedings, we recalculate the NLTE nitrogen abundances in 22 Galactic and 9 SMC A-supergiants using improved atomic data and model atmospheres to compare with new evolution models. The new abundances are higher than previously published values, and suggest that most of these stars have undergone substantial mixing with CN-cycled gas. While there is no clear relationship with mass, there is an apparent relation with metallicity since the SMC stars (including B-stars) have larger nitrogen enrichments. We suggest that rotational mixing is indicated from the main-sequence throughout the supergiant range, with more substantial rotational mixing in the SMC stars. In addition, the SMC AF-supergiants appear to have undergone the first dredge-up during a previous red giant phase, and possibly the Galactic AF-supergiants have as well. All abundances are compared to the new solar abundances from M. Asplund (this conference).

  6. Supergiant variability - Amplitudes and pulsation constants in relation with mass loss and convection

    Microsoft Academic Search

    A. Maeder

    1980-01-01

    The distribution in the HR diagram of the amplitudes of light variations for supergiants is established on the basis of 2420 observations of supergiants made over the last 20 yr in the Geneva photometry (Rufener, 1979). It is shown that a) for any spectral type the amplitudes increase with the luminosity, b) for Ia supergiants there is a small local

  7. Is macroturbulent broadening in OB Supergiants related to pulsations?

    E-print Network

    Simón-Díaz, S; Herrero, A; Castro, N; Puls, J; Aerts, C

    2010-01-01

    The spectrum of O and B Supergiants is known to be affected by an important extra line-broadening (usually called \\macro) that adds to stellar rotation. Recent analysis of high resolution spectra has shown that the interpretation of this line-broadening as a consequence of large-scale turbulent motions would imply highly super-sonic velocity fields, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. We present first encouraging results of an observational project aimed at investigating the $macroturbulent$ broadening in O and B Supergiants, and its possible connection with spectroscopic variability phenomena and stellar oscillations: a) all the studied B Supergiants show line profile variations, quantified by means of the first () and third velocity () moments of the lines, b) there is a strong correlation between the peak-to-peak amplitudes of the and variability and the size of the extra-broadening.

  8. 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)

  9. Wind emission of OB supergiants and the influence of clumping

    E-print Network

    Michaela Kraus; Jiri Kubat; Jiri Krticka

    2007-08-06

    The influence of the wind to the total continuum of OB supergiants is discussed. For wind velocity distributions with \\beta > 1.0, the wind can have strong influence to the total continuum emission, even at optical wavelengths. Comparing the continuum emission of clumped and unclumped winds, especially for stars with high \\beta values, delivers flux differences of up to 30% with maximum in the near-IR. Continuum observations at these wavelengths are therefore an ideal tool to discriminate between clumped and unclumped winds of OB supergiants.

  10. Red Supergiant Stars as Cosmic Abundance Probes: KMOS Observations in NGC 6822

    E-print Network

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

    2015-01-01

    We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new VLT-KMOS instrument. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = -0.52 $\\pm$ 0.21 which agrees well with previous abundance studies of young stars and HII 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 with recent evolutionary models.

  11. Red Supergiant Stars as Cosmic Abundance Probes: KMOS Observations in NGC 6822

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  12. Red supergiants as tracers of Perseus Arm structure

    NASA Astrophysics Data System (ADS)

    Dorda, Ricardo; Negueruela, Ignacio; Gonzalez-Fernandez, Carlos

    2013-06-01

    We have performed a systematic search for red supergiants in the Perseus Arm (from l = 95 degrees up to l = 150 degrees). For this purpose we made a selection of candidates through photometric criteria, using data from UCAC, USNO and 2MASS catalogs. 747 stars were observed in the spectral region around the infrared Ca triplet (8400-8900 Å) at R ~ 10000, using the Intermediate Dispersion Spectrograph (IDS) on the Isaac Newton Telescope (INT, Roque de los Muchachos Observatory). From these data we have obtained radial velocities, spectral type and luminosity class, finding 353 supergiants. Using them we have analysed the distribution in the radial velocity-galactic latitude diagram, tracing the young clusters and galactic structure in this region.

  13. Observations of Cool Giants and Supergiants with Hot Companions

    NASA Astrophysics Data System (ADS)

    Ake, Thomas B.

    1984-07-01

    We propose to observe middle and late-type giant and supergiant stars whose TD-1 and ANS fluxes indicate the presence of a hot component. Some of the secondaries are seen weakly in optical spectra but cannot be classified accurately, while others are UV discoveries. The companions apparently lie on the main sequence, and thus can be used to derive more accurate luminosities than can now be done for individual giants and supergiants. Since the companions contribute little light in the optical region, ultimately this group can be useful in calibrating the upper end of the Wilson-Bappu relations. Evidence for enhanced mass loss for the secondaries or warm plasma around the stars, as seen in some systems of this kind, will be examined.

  14. Yellow Hypergiants as Dynamically Unstable Post-Red-supergiant Stars

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.; Chin, Chao-wen; Hansen, James E. (Technical Monitor)

    2001-01-01

    According to recent theoretical studies, the majority of single stars more massive than 30 solar mass successfully evolve into red supergiants, but then lose most of their hydrogen envelopes and metamorphose into hot blue remnants. While they are cool, they become dynamically unstable as a result of high radiation pressure and partial ionization of the gases in their outer layers. It is shown here that these unstable red-supergiant models repeatedly shrink and re-expand on a thermal time scale when perturbed by heavy bursts of mass loss. Consequently, they fill up the domain of yellow hypergiants on the Hertzsprung-Russell diagram and display very fast rates of evolution there, as observed.

  15. Turbulent Structure in the Upper Chromospheres of Cool Supergiants

    NASA Astrophysics Data System (ADS)

    Griffin, R. E.

    2013-05-01

    Although the contribution of a chromosphere to the total flux may be small, it plays a vital role as the interface between the star and interstellar space, as it is where the stellar wind originates. The very outermost layers of a star are expected to be turbulent. Images of the solar chromosphere and corona reveal both small-scale inhomogeneities (prominences and spaces) and large-scale variability (polar plumes near sunspot minima, streamers near sunspot maxima), and something similar but more exaggerated can be expected in cool supergiants. Samplings of the high chromosphere in late-K supergiants show extreme variability in both density and velocity, and can be thought of as analogues of the solar case. Series of chromospheric-eclipse spectra of the Ca ii K line in 31 Cyg, 32 Cyg and ?Aur demonstrate (a) the presence in the high chromosphere of discrete, rapidly-moving clumps of gas, (b) that structures are not stable or symmetrical, either from eclipse to eclipse or from ingress to egress in the same eclipse, (c) plenty of empty space, and (d) huge differences between one late-K supergiant and another. What information can this evidence offer as regards the outer structure and wind of Betelgeuse?

  16. Luminosities for two yellow supergiants - Nonvariables and the instability strip

    NASA Technical Reports Server (NTRS)

    Evans, Nancy R.

    1993-01-01

    The luminosities for two yellow supergiants HD 183864 and Psi And = HD 223047 are determined from the IUE spectra of their hot companions. The absolute magnitudes of HD 183864 and HD 223047 are -2.3 and -2.1 mag, respectively, and their companions have spectral types of A0.0 V and B8.8 V. The companion of Psi And is compatible with the orbital motion tentatively detected by speckle interferometric observations. The supergiant luminosities are combined with the Cepheid luminosities determined in the same way, and also the variables and nonvariables from Schmidt's studies of open clusters. As found by Schmidt, the variable and nonvariable supergiants have almost no overlap in the HR diagram. The combined sample defines the locus of the helium burning blue loops of evolutionary tracks. Because no nonvariables are found to the blue of fainter Cepheids, the observed blue edge of the Cepheid region may be partly determined by the blue loops rather than by the region of pulsational instability.

  17. B[e] supergiants: What is their evolutionary status?

    E-print Network

    N. Langer; A. Heger

    1997-11-25

    In this paper, we investigate the evolutionary status of B[e]~stars from the point of view of stellar evolution theory. We try to answer to the question of how massive hot supergiants --- i.e. evolved stars --- can be capable of producing a circumstellar disk. We find and discuss three possibilities: very massive evolved main sequence stars close to critical rotation due to their proximity to their Eddington-limit, blue supergiants which have just left the red supergiant branch, and single star merger remnants of a close binary system. While the latter process seems to be required to understand the properties of the spectroscopic binary R4 in the LMC, the other two scenarios may be capable of explaining the distribution of the B[e] stars in the HR~diagram. The three scenarios make different predictions about the duration of the B[e]~phase, the time integrated disk mass and the stellar properties during the B[e]~phase, which may ultimately allow to distinguish them observationally.

  18. Water on the Early M Supergiant Stars ? Orionis and ? Cephei

    NASA Astrophysics Data System (ADS)

    Tsuji, T.

    2000-08-01

    We reanalyze the spectra of ? Ori (M2 Iab) and ? Cep (M2 Ia) observed with the balloon-borne telescope Stratoscope II more than 35 years ago, and we confirm the presence of water in these early M supergiant stars. This identification was first proposed by the Stratoscope observers themselves (Woolf, Schwarzschild, and Rose in 1964; and Danielson, Woolf, and Gaustad in 1965), but this important discovery was overlooked for a long time without any follow-up observation. Consequently, this finding has so far had little influence on the theory of the atmosphere of red supergiant stars. A reason for this may be due to an early criticism by Wing and Spinrad, who suggested CN instead of H2O for the spectral features observed by Stratoscope II. This alternative proposition has more easily been accepted since CN has widely been observed from the Sun to red supergiants, while H2O has been observed only in very cool stars such as Mira variables. In fact, we confirm that the self-consistent photospheric model of the early M supergiants shows CN bands but no H2O band in the near-infrared. Nevertheless, we find that the contribution of CN is only minor and that H2O should be the dominant absorber for the 1.4 and 1.9 ?m features on the Stratoscope spectra of ? Ori and ? Cep, a conclusion opposite to that of Wing and Spinrad. The observed spectra can best be interpreted by the water gas with the column density of the order of 1020 cm-2 and temperature about 1500+/-500 K, but they cannot be originating in the photosphere. We suggest a possible presence of a gaseous component not as hot as the chromosphere but warmer than the cool expanding envelope. On the other hand, we notice that the mid-infrared pure-rotation lines of H2O recently discovered on Betelgeuse (? Ori) and Antares (? Sco) by Jennings and Sada may partly be originating in the photosphere, even though the larger part should again be nonphotospheric in origin. Thus, the presence of water possibly originating in the outer atmosphere of Betelgeuse is confirmed by the independent observation in the mid-infrared region. We now conclude that water should be an important new probe on the atmosphere of the early M supergiant stars, for which water has not been recognized as such until recently.

  19. A-type Supergiant Abundances in the SMC: Probes of Evolution

    E-print Network

    Kim Venn

    1999-01-21

    New abundances of N, O, Na, Mg, Si, Ca, Sc, Ti, Cr, Fe, Sr, Zr, and Ba are presented for 10 A-type supergiants in the SMC, plus upper limits for C. In interpreting the CNO results for constraints on stellar evolution theories, careful attention has been paid to the comparison abundances, i.e., the present day abundances of SMC nebulae and B-dwarf stars. These new results are also compared to published results from F-K supergiant analyses, and found to be in good agreement when both sets of data are carefully examined as differential (SMC minus Galactic standard) abundances. With the exception of nitrogen, very small star-to-star abundance variations are found for all elements in this analysis. The N variations are not predicted by standard stellar evolution models. Instead, the results support the new predictions reported from rotating stellar models, where the range in nitrogen is the result of partial mixing of CN-cycled gas from the stellar interior due to main-sequence rotation at different rates (c.f., Langer & Heger 1998). The overall overabundance of nitrogen in the sampled stars also implies these stars have undergone the first dredge-up in addition to having been mixed while on the main-sequence. The alpha-elements (O, Mg, Si, Ca, Ti) have similar underabundances to Fe, which is not the same as seen in metal-poor stars in the solar neighborhood of the Galaxy. In addition, certain light s-process elements (Zr, Ba) are slightly more underabundant than Fe, which is predicted by the bursting chemical evolution model presented by Pagel & Tautvaisiene (1998) for the SMC.

  20. Supergiant Fast X-ray Transients With Swift

    NASA Astrophysics Data System (ADS)

    Mangano, V.

    2011-09-01

    We present a review of the Swift monitoring program of Supergiant Fast X-ray Transients (SFXT). This class of High-Mass X-ray Binaries with O or B supergiant stars as optical counterparts shows X-ray outbursts about 4 orders of magnitude brighter than the quiescent state. Thanks to its scheduling flexibility, Swift has recently opened a new line of investigation on these sources. It allowed us to regularly monitor a small sample of SFXTs with 2-3 observations per week (1-2 ks) with the X-ray Telescope (XRT) over their entire visibility period (9 months/year) for over 2 years. This intense monitoring caught the sources throughout all phases of their lives (outbursts, intermediate emission level, and quiescence) with very sensitive non-serendipitous observations and allowed us to determine long-term properties and duty cycles. We also monitored two sources along their whole orbital periods and provided for the first time well sampled light curves suitable for testing different mechanisms proposed to explain the nature of these transients. Finally, thanks to Swift's autonomous and rapid re-pointing, we were able to catch and study, for the first time, the X-ray evolution of bright outburst episodes over timescales of days/weeks, thus determining the actual duration of the events. We also characterized the shape of their X-ray spectra through simultaneous broadband spectroscopy.

  1. Yellow and Red Supergiants in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Neugent, Kathryn F.; Massey, Philip; Skiff, Brian; Meynet, Georges

    2012-04-01

    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 (~278 km s-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 ~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.

  2. 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.

  3. YELLOW AND RED SUPERGIANTS IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Neugent, Kathryn F.; Massey, Philip; Skiff, Brian [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States); Meynet, Georges, E-mail: kneugent@lowell.edu, E-mail: phil.massey@lowell.edu, E-mail: bas@lowell.edu, E-mail: georges.meynet@unige.ch [Geneva Observatory, Geneva University, CH-1290 Versoix (Switzerland)

    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.

  4. 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. PMID:14739452

  5. Red supergiants in the LMC - II. Spectrophotometry and model atmospheres

    NASA Astrophysics Data System (ADS)

    Oestreicher, M. O.; Schmidt-Kaler, Th.

    1998-09-01

    Spectrophotometric observations for 88 red supergiant candidates in the Large Magellanic Cloud are presented. The spectra range from 4800 to 7700Angstroms with a resolution of 10Angstroms. The error in the absolute fluxes is 0.04 to 0.05mag. The molecular bands of the member stars are often rather weak, i.e. many of these are not M- but K-type supergiants. The data are available on the Strasbourg stellar data base (CDS). Most of the red (super)giant model atmospheres available up to now do not reproduce the observations well. The models of Kurucz and Lejeune, Cuisinier & Buser - often applied especially to population synthesis - correctly describe the strengths of atomic lines and the overall increase of the flux towards the red, but strongly underestimate the strengths of molecular bands. The models presented by Plez, however, tend to reproduce the observed spectra well, except for the blue, as they include a more complete list of opacity sources. Concerning physical properties, only the Plez models give reliable results. Considering the relation between effective temperature and the strengths of molecular bands, both the Kurucz and Lejeune models predict much higher temperatures than derived from the interferometric radius measurements discussed by Schmidt-Kaler and Dyck et al. The temperatures given by the Plez models show a much better agreement with these observations. Furthermore, the relation between T_eff and molecular absorption is much more clearly defined. When considering metallicities, however, the Plez models also fail, as they predict a [Fe/H] distribution that is much too broad, and furthermore an increase of T_eff with increasing [Fe/H] which clearly contradicts models of stellar evolution. The effective temperatures based on the Plez models range mostly from 3500 to 4100K. The surface gravities derived on the basis of the Geneva evolutionary models range from logg=-0.3 to 0.3, while the bolometric luminosities based on BVRIJHK observations range from -6.6 to -9.0mag. Except for the most luminous objects, the stars form a well-defined strip in the Hertzsprung-Russell diagram extending to the Hayashi limit at 3500K. At present, reliable metallicities cannot be derived because of inadequacies in the model atmospheres.

  6. Delta-slow solution to explain B supergiant stars' winds

    NASA Astrophysics Data System (ADS)

    Haucke, M.; Araya, I.; Arcos, C.; Curé, M.; Cidale, L.; Kanaan, S.; Venero, R.; Kraus, M.

    2015-01-01

    A new radiation-driven wind solution called ?-slow was found by Curé et al. (2011) and it predicts a mass-loss rate and terminal velocity slower than the fast solution (m-CAK, Pauldrach et al. 1986). In this work, we present our first synthetic spectra based on the ?-slow solution for the wind of B supergiant (BSG) stars. We use the output of our hydrodynamical code HYDWIND as input in the radiative transport code FASTWIND (Puls et al. 2005). In order to obtain stellar and wind parameters, we try to reproduce the observed H?, H?, H?, H?, Hei 4471, Hei 6678 and Heii 4686 lines. The synthetic profiles obtained with the new hydrodynamical solutions are in good agreement with the observations and could give us clues about the parameters involved in the radiation force.

  7. A new survey of cool supergiants in the Magellanic Clouds

    E-print Network

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

    2015-01-01

    In this study, we conduct a pilot program aimed at the red supergiant population of the Magellanic Clouds. We intend to extend the current known sample to the unexplored low end of the brightness distribution of these stars, building a more representative dataset with which to extrapolate their behaviour to other Galactic and extra-galactic environments. We select candidates using only near infrared photometry, and with medium resolution multi-object spectroscopy, we perform spectral classification and derive their line-of-sight velocities, confirming the nature of the candidates and their membership to the clouds. Around two hundred new RSGs have been detected, hinting at a yet to be observed large population. Using near and mid infrared photometry we study the brightness distribution of these stars, the onset of mass-loss and the effect of dust in their atmospheres. Based on this sample, new a priori classification criteria are investigated, combining mid and near infrared photometry to improve the observat...

  8. 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.

  9. Elemental abundances of the supergiant stars ? Cygnus and ? Leonis

    NASA Astrophysics Data System (ADS)

    Tanr?verdi, Taner

    2013-12-01

    This study aims to analyse the elemental abundances for the late B type supergiant star ? Cyg and the early A-type supergiant ? Leo using ATLAS9 (Kurucz, 1995; Sbordone et al., 2004), assuming local thermodynamic equilibrium (LTE). The spectra used in this study are obtained from Dominion Astrophysical Observatory and have high resolution and signal-to-noise ratios. The effective temperature and the surface gravity of ? Cyg are determined from the ionisation equilibria of Al I/II, Mg I/II, Fe I/II, Fe II/III, and by fitting to the wings of H? and H? profiles as Teff = 10388 K and log g = 1.80. The elemental abundances of ? Leo are determined using Teff = 9600 K and log g = 2.00, as reported by Przybilla et al. (2006). The ionisation equilibria of C I/II, N I/II, Mg I/II, Ca I/II, Cr I/II and Fe I/II/III are also satisfied in the atmosphere of ? Leo. The radial velocities of ? Cyg and ? Leo are -7.25 ± 7.57 km s-1 and 10.40 ± 13.37 km s-1, respectively. The derived projected rotational velocities vsini from synthetic spectra are 27 and 2 km s-1 for both stars, respectively. The macroturbulent velocities (?) are 24 ± 2 km s-1 and 14.5 ± 1.5 km s-1. Also, the microturbulent velocities (?) have been determined for both of stars as 3.5 km s-1. The CNO abundance results of ? Cyg and ? Leo show C deficiency, N overabundance and O in excess.

  10. Investigating supergiant fast X-ray transients with LOFT

    NASA Astrophysics Data System (ADS)

    Romano, P.; Bozzo, E.; Esposito, P.; Ferrigno, C.; Mangano, V.

    2012-12-01

    Supergiant Fast X-ray Transients (SFXT) are a class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. LOFT, the Large Observatory For X-ray Timing, with its coded mask Wide Field Monitor (WFM) and its 10 m2 class collimated X-ray Large Area Detector (LAD), will be able to dramatically deepen the knowledge of this class of sources. It will provide simultaneous high S/N broad-band and time-resolved spectroscopy in several intensity states, and long term monitoring that will yield new determinations of orbital periods, as well as spin periods. We show the results of an extensive set of simulations performed using previous observational results on these sources obtained with Swift and XMM-Newton. The WFM will detect all SFXT flares within its field of view down to a 15-20 mCrab in 5 ks. Our simulations describe the outbursts at several intensities (F(2-10keV) = 5.9×10-9 to 5.5 × 10-10 erg cm-2 s-1), the intermediate and most common state (10-11 erg cm-2 s-1), and the low state (1.2 × 10-12 to 5 × 10-13 erg cm-2 s-1). We also considered large variations of NH and the presence of emission lines, as observed by Swift and XMM-Newton.

  11. IRC -10414: a bow-shock-producing red supergiant star

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Menten, K. M.; Kniazev, A. Y.; Langer, N.; Mackey, J.; Kraus, A.; Meyer, D. M.-A.; Kami?ski, T.

    2014-01-01

    Most runaway OB stars, like the majority of massive stars residing in their parent clusters, go through the red supergiant (RSG) phase during their lifetimes. Nonetheless, although many dozens of massive runaways were found to be associated with bow shocks, only two RSG bow-shock-producing stars, Betelgeuse and ? Cep, are known to date. In this paper, we report the discovery of an arc-like nebula around the late M-type star IRC -10414 using the SuperCOSMOS H-alpha Survey. Our spectroscopic follow-up of IRC -10414 with the Southern African Large Telescope (SALT) showed that it is a M7 supergiant, which supports previous claims on the RSG nature of this star based on observations of its maser emission. This was reinforced by our new radio- and (sub)millimetre-wavelength molecular line observations made with the Atacama Pathfinder Experiment 12-m telescope and the Effelsberg 100-m radio telescope, respectively. The SALT spectrum of the nebula indicates that its emission is the result of shock excitation. This finding along with the arc-like shape of the nebula and an estimate of the space velocity of IRC -10414 (?70 ± 20 km s-1) imply the bow shock interpretation for the nebula. Thus, IRC -10414 represents the third case of a bow-shock-producing RSG and the first one with a bow shock visible at optical wavelengths. We discuss the smooth appearance of the bow shocks around IRC -10414 and Betelgeuse and propose that one of the necessary conditions for stability of bow shocks generated by RSGs is the ionization of the stellar wind. Possible ionization sources of the wind of IRC -10414 are proposed and discussed.

  12. 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.

  13. Supergiant fast X-ray transients as an under-luminous class of supergiant X-ray binaries

    NASA Astrophysics Data System (ADS)

    Bozzo, E.; Romano, P.; Ducci, L.; Bernardini, F.; Falanga, M.

    2015-02-01

    The usage of cumulative luminosity distributions, constructed thanks to the long-term observations available through wide field hard X-ray imagers, has been recently exploited to study the averaged high energy emission (>17 keV) from supergiant fast X-ray transients (SFXTs) and classical Supergiant High Mass X-ray Binaries (SgXBs). Here, we take advantage of the long term monitorings now available with Swift/XRT to construct for the first time the cumulative luminosity distributions of a number of SFXTs and the classical SgXB IGR J18027-2016 in the soft X-ray domain with a high sensitivity focusing X-ray telescope (0.3-10 keV). By complementing previous results obtained in the hard X-rays, we found that classical SgXBs are characterized by cumulative distributions with a single knee around ? 1036-1037 erg s-1, while SFXTs are found to be systematically sub-luminous and their distributions are shifted at significantly lower luminosities (a factor of ? 10-100). As the luminosity states in which these sources spend most of their time are typically below the sensitivity limit of large field of view hard X-ray imagers, we conclude that soft X-ray monitorings carried out with high sensitivity telescopes are particularly crucial to reconstruct the complete profile of the SFXT cumulative luminosity distributions. The difference between the cumulative luminosity distributions of classical SgXBs and SFXTs is interpreted in terms of accretion from a structured wind in the former sources and the presence of magnetic/centrifugal gates or a quasi-spherical settling accretion regime in the latter.

  14. The Araucaria Project: VLT Spectra of Blue Supergiants in WLM- Classification and First Abundances

    NASA Astrophysics Data System (ADS)

    Bresolin, Fabio; Pietrzy?ski, Grzegorz; Urbaneja, Miguel A.; Gieren, Wolfgang; Kudritzki, Rolf-Peter; Venn, Kim A.

    2006-09-01

    As part of the Araucaria Project, we present the first spectral catalog of supergiant stars in the Local Group dwarf irregular galaxy WLM. In assigning a spectral classification to these stars we accounted for the low metal content of WLM relative to the galactic standards used in the MK process, by using classification criteria developed for B and A supergiants contained in the Small Magellanic Cloud. Our spectral catalog shows that our higher signal-to-noise ratio (S/N) spectroscopic sample of 19 objects contains at least six early B (B0-B5) supergiants and six late B and early A (B8-A2) stars of luminosity class between Ia and II, as well as an O7 V star and an O9.7 Ia star. The spectra of several of these stars are of sufficiently high quality for a determination of the stellar parameters and abundances. We have also acquired a second set of lower S/N spectra for mostly BA stars; however, their quality does not allow a further analysis. We have carried out a quantitative analysis for three early B supergiants. The mean oxygen abundance we derive is 12+log(O/H)=7.83+/-0.12. This value agrees very well with the measurement that is obtained from H II regions. We therefore find no additional evidence for the discrepancy between stellar and nebular oxygen abundances measured for a single A-type supergiant by Venn et al. The analysis of B- and A-type supergiants yields compatible results for nitrogen, silicon, and magnesium. We show that the photometric variability of the blue supergiants included in our spectroscopic sample is negligible for the use of these stars as distance indicators. Based on VLT observations for ESO Large Program 171.D-0004.

  15. The Araucaria Project. VLT spectra of blue supergiants in WLM: classification and first abundances

    E-print Network

    Fabio Bresolin; Grzegorz Pietrzynski; Miguel A. Urbaneja; Wolfgang Gieren; Rolf-Peter Kudritzki; Kim A. Venn

    2006-05-24

    As part of the Araucaria Project, we present the first spectral catalog of supergiant stars in the Local Group dwarf irregular galaxy WLM. In assigning a spectral classification to these stars we accounted for the low metal content of WLM relative to the galactic standards used in the MK process, by using classification criteria developed for B and A supergiants contained in the Small Magellanic Cloud. Our spectral catalog shows that our higher S/N spectroscopic sample of 19 objects contains at least 6 early-B (B0-B5) supergiants and 6 late-B and early-A (B8-A2) stars of luminosity class between Ia and II, as well as an O7~V star and an O9.7 Ia star. The spectra of several of these stars is of sufficiently high quality for a determination of the stellar parameters and abundances. We have acquired also a second set of lower S/N spectra for mostly BA stars, however their quality does not allow a further analysis. We have carried out a quantitative analysis for three early-B supergiants. The mean oxygen abundance we derive is 12+log(O/H)=7.83 +/- 0.12. This value agrees very well with the measurement that is obtained from HII regions. We therefore find no additional evidence for the discrepancy between stellar and nebular oxygen abundances measured for a single A-type supergiant by Venn et al. The analysis of B- and A-type supergiants yields compatible results for nitrogen, silicon and magnesium. We show that the photometric variability of the blue supergiants included in our spectroscopic sample is negligible for the use of these stars as distance indicators.

  16. Bright Flares in Supergiant Fast X-ray Transients

    E-print Network

    Shakura, N; Sidoli, L; Paizis, A

    2014-01-01

    At steady low-luminosity states, Supergiant Fast X-ray Transients (SFXTs) can be at the stage of quasi-spherical settling accretion onto slowly rotating magnetized NS from the OB-companion winds. At this stage, a hot quasi-static shell is formed above the magnetosphere, the plasma entry rate into magnetosphere is controlled by (inefficient) radiative plasma cooling, and the accretion rate onto the NS is suppressed by a factor of \\sim 30 relative to the Bondi-Hoyle-Littleton value. Changes in the local wind velocity and density can only slightly increase the mass accretion rate (a factor of \\sim 10) bringing the system into the Compton cooling dominated regime and led to the production of moderately bright flares (L_x\\lesssim 10^{36} erg/s). To interpret the brightest flares (L_x>10^{36}~erg/s) displayed by the SFXTs, we propose that a larger increase in the mass accretion rate can be produced by sporadic capture of magnetized stellar wind plasma. At sufficiently low accretion rates, magnetic reconnection can ...

  17. The atmospheric structure and fundamental parameters of Red Supergiants

    NASA Astrophysics Data System (ADS)

    Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H.

    2013-05-01

    We present studies of the atmospheric structure and fundamental properties of the red supergiants (RSGs) VY CMa, AH Sco, UY Sct, and KW Sgr based on near-infrared K-band interferometry obtained with the VLTI/AMBER instrument with a spectral resolution of 1500. In our visibility data, we observe the presence of molecular layers of water and CO in extended atmospheres. For a uniform disk modeling, we observe size increases in the water band centered at 1.9 ?m and in the CO band at 2.3-2.5 ?m, with respect to the near-continuum bandpass (2.20-2.25 ?m). With our spectral resolution, we obtain diameters in the near-continuum, that are free from contamination by molecular layers. Using PHOENIX atmosphere models, we estimate Rosseland-mean photospheric angular diameters of VY CMa, AH Sco, UY Sct, and KW Sgr of 11.13 ± 0.3mas, 5.81 ± 0.15mas, 5.48 ± 0.10mas, and 3.91 ± 0.25mas, respectively. We estimate radii and effective temperatures, and place the stars in the HR diagram. The PHOENIX atmosphere models predict the spectra and the continuum visibility values, but do not predict the molecular layers visibility well: The model atmosphere is too compact when compared with the observations. This may be caused by pulsation and/or convection, which are not included in the models.

  18. The molecular envelope around the red supergiant VY CMa

    E-print Network

    S. Muller; Dinh-V-Trung; J. Lim; N. Hirano; C. Muthu; S. Kwok

    2006-11-17

    We present millimeter interferometric observations of the molecular envelope around the red supergiant VY CMa with the SubMillimeter Array (SMA). The high angular resolution (< 2'') allows us to derive the structure of the envelope as observed in the 1.3 mm continuum, 12CO(2-1), 13CO(2-1) and SO(6,5-5,4) lines emission. The circumstellar envelope is resolved into three components: a dense, compact and dusty central component, embedded in a more diffuse and extended envelope plus a high velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (~ 120 deg.) viewed close to the line of sight (i = 15 deg.). Our model can explain the main features of the SMA data and previous single-dish CO multi-line observations. An episode of enhanced mass loss along the bipolar direction is inferred from our modelling. The SMA data provide a better understanding of the complicated morphology seen in the optical/IR high resolution observations.

  19. An IUE survey of activity in red giants and supergiants

    NASA Astrophysics Data System (ADS)

    Oznovich, I.; Gibson, D. M.

    1987-08-01

    Chromospheric and transition region line activity is examined in apparently single red giants and supergiants using the IUE archives. Low-resolution, large-aperture spectra (mostly short-wavelength) were used to search for variations of emission-line fluxes in time. A series of automatic processing procedures were implemented in order to uniformly calibrate a large number of spectra, fit continua to each of them, determine the fluxes of as many as 18 emission lines, and compare them at different epochs. A method is offered to compute the overall error in the integrated flux, a critical measure of activity, independent of the observing and processing details. This processing was applied to above 120 images of 26 stars taken over a period of 7 yr (1978-1984). Four stars showed UV emission-line flux variations. Alpha Aqr, Beta Peg, and Sigma Oph showed a single enhanced-emission event in all detectable emission lines. Gamma Aql exhibited an increase in the flux level of the O I (1641 A) line in mid-1981 with no comparable change in any other lines. These four stars lie in a region of the H-R diagram in which time-dependent circumstellar absorption lines appear.

  20. Line-profiles of F supergiant stars as candidates of proto-planetary nebulae

    NASA Astrophysics Data System (ADS)

    Tamura, S.; Takeuti, M.; Zalewski, J.

    1993-12-01

    In this report the results of spectroscopic observations on selected F supergiant stars as the candidates of proto-planetary nebulae (PPNs) are presented. Volk and Kwok (1989) selected nearly one hundred new candidates of PPNs based upon the scenario on the evolution of them. They summarized four classes of stars which should be the PPNs and are described in various papers. These are (1) High galactic latitude supergiants, (2) Nonvariable OH/IR stars, (3) Low color temperature infrared objects, and (4) R CrB. In order to examine the extended envelope of the PPNs we have started our project to obtain the H alpha profile which should give us some clue to the structure of the envelope. We are mainly concerned with F supergiant stars. Our sample objects are mostly classified as pulsating or semiregular variables.

  1. The missing piece of the puzzle: Neutron stars accreting from supergiant companions

    NASA Astrophysics Data System (ADS)

    Antoniou, Vallia; Zezas, Andreas; Maravelias, Grigoris; Kalogera, Vicky

    2012-09-01

    The supergiant X-ray binaries (SG-XRBs) is a class of High-Mass X-ray Binaries that consists of supergiant fast X-ray transients (SFXTs) and "classical" SG-XRBs exhibiting a strong intrinsic absorption. Nowadays, we know only 3 Galactic "classical" SG-XRBs (with the remaining known wind-fed systems being SFXTs)! Recently, our team discovered the first extragalactic member of this well-hidden population of "classical" SG-XRBs that motivated us to look for additional neutron-star X-ray binaries accreting from supergiant stars. In this talk, I will present the latest results of this reseach based on multi-wavelength observations of the Magellanic Clouds. These first observational constraints of the formation and evolution of "classical" SG-XRBs will help in the planning and interpretation of future multi-wavelength observations of these obscured high-mass X-ray binaries in nearby star-forming galaxies.

  2. Evidence for processed material in the atmospheres of Large Magellanic Cloud B supergiants

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Edward L.; Bohannan, Bruce

    1993-01-01

    We present a high-dispersion study of the optical spectra of 11 LMC B-type supergiants. These stars had been shown previously to have a wide range in nitrogen absorption line strengths, despite having very similar temperatures and luminosities. The current study shows that the relatively rare nitrogen-weak stars also have weaker photospheric helium lines and stronger photospheric oxygen lines than the more spectroscopically typical supergiants. This pattern suggests that the vast majority of LMC B-type supergiants have had their surfaces contaminated by material from their original hydrogen-burning cores - with a resultant enhancement of surface nitrogen and helium and a depletion in oxygen - while the spectroscopically nitrogen-weak stars are more likely to have retained their main-sequence surface abundances.

  3. A spectroscopic survey of B supergiants in the Large Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Edward L.

    1991-01-01

    The results of a low-dispersion digital optical spectral survey of about 100 B-type supergiants in the Large Magellanic Cloud are presented. The MK spectral classification framework for B supergiants has been transferred to the metal-weak LMC stars, and recommended classification standards have been designated. Variations among the metal line strengths are examined. The most extreme variations are found for the nitrogen lines, for which a range of a factor of 3 or more may be seen in the equivalent widths within some spectral subclasses. It is suggested that these variations indicate a range of nitrogen surface abundances among the B supergiants, resulting from contamination of some of the stellar surfaces by processed material from the original H-burning core.

  4. Supernovae from red supergiants with extensive mass loss

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi; Tominaga, Nozomu; Blinnikov, Sergei I.; Baklanov, Petr V.; Sorokina, Elena I.

    2011-07-01

    We calculate multicolour light curves (LCs) of supernovae (SNe) from red supergiants (RSGs) that have exploded within a dense circumstellar medium (CSM). Multicolour LCs are calculated by using the multigroup radiation hydrodynamics code STELLA. If the CSM is dense enough, the shock breakout signal is delayed and smeared by the CSM and the kinetic energy of SN ejecta is efficiently converted to thermal energy, which is eventually released as radiation. We find that explosions of RSGs are affected by the CSM in the early epochs, when the mass-loss rate just before the explosions is higher than ˜10-4 M? yr-1. Their characteristic features are that the LC has a luminous round peak followed by a flat part, that multicolour LCs are simultaneously bright in both ultraviolet and optical at the peak, and that the photospheric velocity is very low at these epochs. We calculate LCs for various CSM conditions and explosion properties, i.e. mass-loss rates, radii of the CSM, density slopes of the CSM, explosion energies of SN ejecta and the SN progenitors contained within, to see their influence. We compare our model LCs with those of ultraviolet-bright Type IIP SN 2009kf and show that the mass-loss rate of the progenitor of SN 2009kf just before the explosion is likely to be higher than 10-4 M? yr-1. Combined with the fact that SN 2009kf is likely to be an energetic explosion and has large 56Ni production, which implies that the progenitor of SN 2009kf is a massive RSG, our results indicate that there could be some mechanism to induce extensive mass loss in massive RSGs just before their explosions.

  5. 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.

  6. Discovery of SiO Band Emission from Galactic B[e] Supergiants

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulate in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation. Based on observations collected with the ESO VLT Paranal Observatory under program 093.D-0248(A).

  7. Quantitative Studies of the Optical and UV Spectra of Galactic Early B Supergiants

    NASA Technical Reports Server (NTRS)

    Searle, S. C.; Prinja, R. K.; Massa, D.; Ryans, R.

    2008-01-01

    We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0-B5 supergiants of luminosity classes Ia, Ib, Iab, and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical comparison of the model predictions to observed UV spectral features is made. Methods. Fundamental parameters (e.g., T(sub eff), log L(sub *), mass-loss rates and CNO abundances) are derived for individual stars using CMFGEN, a nLTE, line-blanketed model atmosphere code. The impact of these newly derived parameters on the Galactic B supergiant Ten scale, mass discrepancy, and wind-momentum luminosity relation is examined. Results. The B supergiant temperature scale derived here shows a reduction of about 1000-3000 K compared to previous results using unblanketed codes. Mass-loss rate estimates are in good agreement with predicted theoretical values, and all of the 20 BO-B5 supergiants analysed show evidence of CNO processing. A mass discrepancy still exists between spectroscopic and evolutionary masses, with the largest discrepancy occuring at log (L/(solar)L approx. 5.4. The observed WLR values calculated for B0-B0.7 supergiants are higher than predicted values, whereas the reverse is true for B1-B5 supergiants. This means that the discrepancy between observed and theoretical values cannot be resolved by adopting clumped (i.e., lower) mass-loss rates as for O stars. The most surprising result is that, although CMFGEN succeeds in reproducing the optical stellar spectrum accurately, it fails to precisely reproduce key UV diagnostics, such as the N v and C IV P Cygni profiles. This problem arises because the models are not ionised enough and fail to reproduce the full extent of the observed absorption trough of the P Cygni profiles. Conclusions. Newly-derived fundamental parameters for early B supergiants are in good agreement with similar work in the field. The most significant discovery, however, is the failure of CMFGEN to predict the correct ionisation fraction for some ions. Such findings add further support to revising the current standard model of massive star winds, as our understanding of these winds is incomplete without a precise knowledge of the ionisation structure and distribution of clumping in the wind. Key words. techniques: spectroscopic - stars: mass-loss - stars: supergiants - stars: abundances - stars: atmospheres - stars: fundamental parameters

  8. 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.

  9. SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR

    SciTech Connect

    Van Dyk, Schuyler D.; Elias-Rosa, Nancy [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Davidge, Tim J., E-mail: vandyk@ipac.caltech.edu, E-mail: tim.davidge@nrc.ca [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, B.C., V9E 2E7 (Canada); 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-P progenitors. It is also consistent with the estimated upper limit on the initial mass of the progenitor of SN 1999br, and it agrees with the low initial masses found for the RSG progenitors of other low-luminosity SNe II-P.

  10. RAPIDLY ACCRETING SUPERGIANT PROTOSTARS: EMBRYOS OF SUPERMASSIVE BLACK HOLES?

    SciTech Connect

    Hosokawa, Takashi; Yorke, Harold W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Omukai, Kazuyuki, E-mail: Takashi.Hosokawa@jpl.nasa.gov, E-mail: hosokwtk@gmail.com, E-mail: omukai@tap.scphys.kyoto-u.ac.jp [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2012-09-01

    Direct collapse of supermassive stars (SMSs) is a possible pathway for generating supermassive black holes in the early universe. It is expected that an SMS could form via very rapid mass accretion with M-dot{sub *} {approx} 0.1-1 M{sub Sun} yr{sup -1} during the gravitational collapse of an atomic-cooling primordial gas cloud. In this paper, we study how stars would evolve under such extreme rapid mass accretion, focusing on the early evolution until the stellar mass reaches 10{sup 3} M{sub Sun }. To this end, we numerically calculate the detailed interior structure of accreting stars with primordial element abundances. Our results show that for accretion rates higher than 10{sup -2} M{sub Sun} yr{sup -1}, stellar evolution is qualitatively different from that expected at lower rates. While accreting at these high rates, the star always has a radius exceeding 100 R{sub Sun }, which increases monotonically with the stellar mass. The mass-radius relation for stellar masses exceeding {approx}100 M{sub Sun} follows the same track with R{sub *}{proportional_to}M {sup 1/2}{sub *} in all cases with accretion rates {approx}> 10{sup -2} M{sub Sun} yr{sup -1}; at a stellar mass of 10{sup 3} M{sub Sun }, the radius is {approx_equal} 7000 R{sub Sun} ({approx_equal} 30 AU). With higher accretion rates, the onset of hydrogen burning is shifted toward higher stellar masses. In particular, for accretion rates exceeding M-dot{sub *}{approx}>0.1 M{sub Sun} yr{sup -1}, there is no significant hydrogen burning even after 10{sup 3} M{sub Sun} have accreted onto the protostar. Such 'supergiant' protostars have effective temperatures as low as T{sub eff} {approx_equal} 5000 K throughout their evolution and because they hardly emit ionizing photons, they do not create an H II region or significantly heat their immediate surroundings. Thus, radiative feedback is unable to hinder the growth of rapidly accreting stars to masses in excess of 10{sup 3} M{sub Sun} as long as material is accreted at rates M-dot{sub *}{approx}>10{sup -2} M{sub Sun} yr{sup -1}.

  11. X-ray Spectroscopy of O Supergiant Winds: Shock Physics, Clumping, and Mass-Loss Rates

    E-print Network

    Cohen, David

    X-ray Spectroscopy of O Supergiant Winds: Shock Physics, Clumping, and Mass-Loss Rates David Cohen-ray emission: wind shocks 1. X-ray constraints on the shocked wind plasma 2. X-ray absorption as a mass. Adiabatic shocks Open questions: very dense winds (WR stars); low density winds (B stars); magnetic OB stars

  12. IGR J18483-0311: a new intermediate supergiant fast X-ray transient

    E-print Network

    F. Rahoui; S. Chaty

    2008-09-25

    IGR J18483-0311 is a high-mass X-ray binary recently discovered by INTEGRAL. Its periodic fast X-ray transient activity and its position in the Corbet diagram - although ambiguous - led to the conclusion that the source was a likely Be/X-ray binary (BeXB), even if a supergiant fast X-ray transient (SFXT) nature could not be excluded. We aimed at identifying the companion star of IGR J18483-0311 to discriminate between the BeXB and the SFXT nature of the source. Optical and near-infrared photometry, as well as near-infrared spectroscopy of the companion star were performed to identify its spectral type. We also assembled and fitted its broad-band spectral energy distribution to derive its physical parameters. We show that the companion star of IGR J18483-0311 is an early-B supergiant, likely a B0.5Ia, and that its distance is about 3-4 kpc. The early-B supergiant nature of its companion star, as well as its fast X-ray transient activity point towards an SFXT nature of IGR J18483-0311. Nevertheless, the long duration and the periodicity of its outbursts, as well as its high level of quiescence, are consistent with IGR J18483-0311 being an intermediate SFXT, in between classical supergiant X-ray binaries (SGXBs) characterised by small and circular orbits, and classical SFXTs with large and eccentric orbits.

  13. Spectrum of class-M supergiants in the region lambda lambda 7000-6000 angstrom

    NASA Technical Reports Server (NTRS)

    Orlov, M. Y.; Rodriguez, M. H.; Shavrina, A. V.

    1973-01-01

    A general description is given of the spectrum of four M-supergiants in the region lambda lambda 7000-6000 A from high-dispersion spectrograms (6 A/mm). The equivalent widths of several hundred lines and depths of some molecular band heads were measured.

  14. The Araucaria Project. VLT spectra of blue supergiants in WLM: classification and first abundances

    E-print Network

    Bresolin, F; Urbaneja, M A; Gieren, W; Kudritzki, R P; Venn, K A; Bresolin, Fabio; Pietrzynski, Grzegorz; Urbaneja, Miguel A.; Gieren, Wolfgang; Kudritzki, Rolf-Peter; Venn, Kim A.

    2006-01-01

    As part of the Araucaria Project, we present the first spectral catalog of supergiant stars in the Local Group dwarf irregular galaxy WLM. In assigning a spectral classification to these stars we accounted for the low metal content of WLM relative to the galactic standards used in the MK process, by using classification criteria developed for B and A supergiants contained in the Small Magellanic Cloud. Our spectral catalog shows that our higher S/N spectroscopic sample of 19 objects contains at least 6 early-B (B0-B5) supergiants and 6 late-B and early-A (B8-A2) stars of luminosity class between Ia and II, as well as an O7~V star and an O9.7 Ia star. The spectra of several of these stars is of sufficiently high quality for a determination of the stellar parameters and abundances. We have acquired also a second set of lower S/N spectra for mostly BA stars, however their quality does not allow a further analysis. We have carried out a quantitative analysis for three early-B supergiants. The mean oxygen abundanc...

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

    SciTech Connect

    Gray, David F.; Pugh, Teznie, E-mail: dfgray@uwo.ca [Department of Physics and Astronomy, University of Western Ontario, London, Ontario (Canada)

    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.

  16. 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 ? 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 ? 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 ? 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.

  17. Water vapor on supergiants. The 12 micron TEXES spectra of mu Cephei

    E-print Network

    N. Ryde; M. J. Richter; G. M. Harper; K. Eriksson; D. L. Lambert

    2006-03-15

    Several recent papers have argued for warm, semi-detached, molecular layers surrounding red giant and supergiant stars, a concept known as a MOLsphere. Spectroscopic and interferometric analyses have often corroborated this general picture. Here, we present high-resolution spectroscopic data of pure rotational lines of water vapor at 12 microns for the supergiant mu Cephei. This star has often been used to test the concept of molecular layers around supergiants. Given the prediction of an isothermal, optically thick water-vapor layer in Local Thermodynamic Equilibrium around the star (MOLsphere), we expected the 12 micron lines to be in emission or at least in absorption but filled in by emission from the molecular layer around the star. Our data, however, show the contrary; we find definite absorption. Thus, our data do not easily fit into the suggested isothermal MOLsphere scenario. The 12 micron lines, therefore, put new, strong constraints on the MOLsphere concept and on the nature of water seen in signatures across the spectra of early M supergiants. We also find that the absorption is even stronger than that calculated from a standard, spherically symmetric model photosphere without any surrounding layers. A cool model photosphere, representing cool outer layers is, however, able to reproduce the lines, but this model does not account for water vapor emission at 6 microns. Thus, a unified model for water vapor on mu Cephei appears to be lacking. It does seem necessary to model the underlying photospheres of these supergiants in their whole complexity. The strong water vapor lines clearly reveal inadequacies of classical model atmospheres.

  18. The chemical composition of luminous stars: problems or opportunities?

    NASA Astrophysics Data System (ADS)

    Lambert, D. L.

    The surface chemical composition of a luminous star changes as the star evolves. Spectroscopic definition of the changes may be used to test stellar evolutionary models. This essay discusses some of the observed and predicted changes in three different groups of luminous stars: hot massive stars, yellow supergiants, and luminous asymptotic giant branch stars.

  19. 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 (Argentina), under program ID GN-2013B-Q-10.

  20. Herschel/HIFI View on Massive Evolved Stars: the HIFISTARS sample of Supergiant and Yellow Hypergiant envelopes

    NASA Astrophysics Data System (ADS)

    Teyssier, D.; Marston, A.; Alcolea, J.; Bujarrabal, V.; Hifistars Consortium

    2011-05-01

    We present the first results of one the HIFISTARS (Bujarrabal et al. 2010, see also Decin et al., this conference) sub-programmes dedicated to the study of the physico-chemical conditions and the mass-loss history in Red Supergiants and Yellow Hypergiants. Such sources are the most massive and luminous stars in the pathway of stellar evolution, and as such are fast-lived and characterised by very intense winds and mass-loss rates. These conditions and the large size of their envelope contribute to a particularly rich chemistry. At the end of their evolution, Super/Hyergiant stars are expected to die hard and form black holes or neutron stars after a supernova. The HIFISTARS' sample of evolved massive stars considers three Red Supergiants (NML Cyg, Betelgeuse, and VY CMa) and two Yellow Hypergiants (IRC+10420 and AFGL2343), in a handful of submm and FIR CO/13CO lines, as well as several water, HCN, SiO, SO, SO2, and other bonus lines collected over the whole HIFI frequency ranges. While most of the CO, the OH line at 1835 GHz, and both ortho- and para- ground-state water lines are detected in all targets, there is a clear difference for the less-abundant N-bearing, Si-bearing and S-bearing species. The various water lines covered by the survey are also relatively un-evenly represented from one source to another, with some of the transitions showing up as masers. The observed lines feature complex and distinct profiles, indicative of the strong and asymmetric wings at play for some of the transitions. Of the four sources observed so far (all but AFGL2343), VY CMa clearly stands out as an exceptional object, with most lines 2-10x stronger than any other Super/Hypergiants, and revealing in particular an extremely rich water chemistry observed nowhere in the other sources of the sample (Alcolea et al., in preparation, see also Menten et al., this conference).

  1. Properties of the CO and H$_2$O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations

    E-print Network

    Montargès, Miguel; Perrin, Guy; Ohnaka, Keiichi; Chiavassa, Andrea; Ridgway, Stephen T; Lacour, Sylvestre

    2014-01-01

    Context. Betelgeuse is the closest red supergiant (RSG), therefore it is well suited to study the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims. We intend to investigate the shape and composition of the close molecular layer (also known as the MOLsphere) that surrounds the star. This analysis is part of a wider program that aims at understanding the dynamics of the circumstellar envelope of Betelgeuse. Methods. On January and February 2011, Betelgeuse was observed using the VLTI/AMBER interferometer in the H and K bands. Using the medium spectral resolution of the instrument ($R \\sim 1500$), we were able to investigate the carbon monoxide band heads and the water-vapor bands. We used two different approaches to analyse our data: model fitting both in the continuum and absorption lines and then fit with a RHD simulation. Results. Using the continuum data we derive a uniform disk diameter of $41.01 \\pm 0.41$ mas, a power law type limb-darkened disk dia...

  2. UBV Observations of Post-AGB Supergiants and Peculiarities of Their Photometric Variability

    NASA Astrophysics Data System (ADS)

    Arkhipova, V. P.; Ikonnikova, N. P.; Noskova, R. I.; Sokol, G. V.

    2000-09-01

    The systematic UBV observations of six variable post-AGB supergiants in 1991-1999 are presented. Their variability is analyzed. The coolest stars V1027 Cyg and V354 Lac exhibit bimodal pulsations with variable amplitudes. Apart from pulsations, the hotter stars V887 Her and IRAS 19386+0155 show light variations associated with a stellar wind. A variable stellar wind appears to be mainly responsible for the photometric variations in the still hotter stars SAO 163075 and IRAS 20572+4919. Distinct trends in the yearly mean brightness have been found in three of the six supergiants studied, with the trend amplitude being independent of the spectral range. They are interpreted as the result of dust envelopes composed of large grains with R = A_V/E(B-V) > or = 7 becoming optically thin.

  3. 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 (?/?? ˜ 65 000) circular polarization (Stokes V) spectra of six late B- and early A-type supergiants (? Ori, B8Iae; 4 Lac, B9Iab; ? Leo, A0Ib; HR1040, A0Ib; ? Cyg, A2Iae; ? 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 1? 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.

  4. 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

  5. B-type supergiants in the Small Magellanic Cloud: rotational velocities and implicationsfor evolutionary models

    Microsoft Academic Search

    P. L. Dufton; R. S. I. Ryans; S. Simón-Díaz; C. Trundle; D. J. Lennon

    2006-01-01

    High-resolution spectra for 24 SMC and Galactic B-type supergiants have been analysed to estimate the contributions of both macroturbulence and rotation to the broadening of their metal lines. Two different methodologies are considered, viz. goodness-of-fit comparisons between observed and theoretical line profiles and identifying zeros in the Fourier transforms of the observed profiles. The advantages and limitations of the two

  6. B-type supergiants in the SMC: Rotational velocities and implications for evolutionary models

    Microsoft Academic Search

    P. L. Dufton; R. S. I. Ryans; S. Simon-D ´ iaz; C. Trundle; D. J. Lennon

    2005-01-01

    High-resolution spectra for 24 SMC and Galactic B-type supergiants have been\\u000aanalysed to estimate the contributions of both macroturbulence and rotation to\\u000athe broadening of their metal lines. Two different methodologies are\\u000aconsidered, viz. goodness-of-fit comparisons between observed and theoretical\\u000aline profiles and identifying zeros in the Fourier transforms of the observed\\u000aprofiles. The advantages and limitations of the two

  7. A Transient Supergiant X-Ray Binary in IC 10: An Extragalactic SFXT?

    NASA Astrophysics Data System (ADS)

    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 × 1037 erg s-1during 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 (? = 0.3) with fitted column density (NH = 6.3 × 1021 atom cm-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-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 H?. 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.

  8. 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. PMID:25119040

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    SciTech Connect

    Dawson, J. R.; Dickey, John M. [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia)] [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia); McClure-Griffiths, N. M. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield NSW 2122 (Australia)] [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield NSW 2122 (Australia); Wong, T. [Astronomy Department, University of Illinois, Urbana, IL 61801 (United States)] [Astronomy Department, University of Illinois, Urbana, IL 61801 (United States); Hughes, A. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany)] [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany); Fukui, Y. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan)] [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan); Kawamura, A., E-mail: joanne.dawson@utas.edu.au [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan)

    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.

  11. Spectral atlas of O9.5-A1-Type supergiants

    NASA Astrophysics Data System (ADS)

    Chentsov, E. L.; Sarkisyan, A. N.

    2007-09-01

    High-resolution spectra of nine supergiants and three comparison stars taken with CCD echelle spectrographs in the coude’ foci of the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and 2-m telescope of Terskol Observatory (with R = 40000 and R = 45000, respectively) are reported in a tabular and graphic form. Two hundred ( ? Cam, O9.5 Ia) to 1000 (HD 12953, A1 Ia-0) stellar and interstellar lines and bands are identified in the 3600 7800 ÅÅ wavelength interval and most of them have their central intensities and heliocentric radial velocities measured. A spectral classification based on weak photospheric absorptions is tested. This is actual for the brightest supergiants and hypergiants, where the formation regions of strong lines, which are traditionally used for classification, also include the bases of stellar winds. Radial gradients of velocity are revealed in the atmospheres of supergiants. The cases of the refinement of the effective wavelengths, analysis of blends, and revealing of wind anomalies in line profiles are illustrated. The atlas is used extensively as a teaching tool.

  12. 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.

  13. Red supergiants in the LMC - IV: Calibration of intrinsic colours and the HRD

    NASA Astrophysics Data System (ADS)

    Oestreicher, M. O.; Schmidt-Kaler, Th.

    A new calibration of the (B-V)0, (V-R)0 and (V-I)0 colours in the Kron-Cousins system for F to M supergiants and of the (V-K)0 colours in the SAAO system of K to M supergiants in the LMC as measures of effective temperature and bolometric correction is given. For F to G supergiants the theoretical Teff-intrinsic colour- relations given by Lejeune et al. (1997) on the basis of their own model atmospheres agree mostly well with our observations. For K to M supergiants, however, their intrinsic colours are too red in most cases. The relations given by Bessell et al. (1998) based on the model atmospheres of Plez (1997) fit the observations better, but their synthetic colours are often also too red. The calibration of the bolometric correction is not reproduced well by any of the models. The HRD of the stars shows two distinct groups, one with log Teff above 3.80 and one with log Teff between 3.53 and 3.62. The upper luminosity and therefore the mass limit depends significantly on effective temperature. The F to G stars have Mbol up to -9.8 mag (corresponding to 45 Msun), while the K to M stars do not exceed - -9.0 mag (corresponding to 31 Msun). Neither the Geneva nor the Padova models can fit the positions of the most luminous and the coolest supergiants. The discrepancy between theory and observation increases both with increasing mass loss rate and overshooting. Best agreement with the observations is reached by assuming mass loss rates of 2/3 of the de Jager et al. (1988) mass loss rates. As shown both by the luminosity and initial mass function, very luminous (i.e. massive) stars are overproportionally rare. With -3.73 +/- 0.20 the slope of the initial mass function is very steep in the considered range of 16-35 Msun, but confirms the results obtained by Massey et al. (1995) from an extensive study of the field OB stars both in the Magellanic Clouds and the Galaxy.

  14. Mon. Not. R. Astron. Soc. 000, 117 (2012) Printed 13 August 2013 (MN LATEX style file v2.2) The Main Sequence of three Red Supergiant Clusters

    E-print Network

    Froebrich, Dirk

    2012-01-01

    Mon. Not. R. Astron. Soc. 000, 1­17 (2012) Printed 13 August 2013 (MN LATEX style file v2.2) The Main Sequence of three Red Supergiant Clusters Dirk Froebrich1 , Alexander Scholz2,3 1Centre and characterisation of the main sequence members of red supergiant rich clusters. Here we utilise publicly available

  15. Spectroscopy and Multi-Band Photometry of Yellow and Red Supergiants in M31 and M33

    NASA Astrophysics Data System (ADS)

    Gordon, Michael; Humphreys, Roberta M.

    2015-01-01

    Recent supernova 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-supernova 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 supergiant candidates in M31 and M33 for review of spectral characteristics and spectral energy distributions. 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. In this study, we present spectral types and discussion of spectral energy distributions of intermediate-type red and yellow supergiants in M31 and M33.

  16. 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 ?m 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.

  17. Properties of the CO and H2O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations

    NASA Astrophysics Data System (ADS)

    Montargès, M.; Kervella, P.; Perrin, G.; Ohnaka, K.; Chiavassa, A.; Ridgway, S. T.; Lacour, S.

    2014-12-01

    Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is well suited for studying the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims: We intend to investigate the shape and composition of the close molecular layer (also known as the MOLsphere) that surrounds the star. This analysis is part of a wider program that aims at understanding the dynamics of the circumstellar envelope of Betelgeuse. Methods: On January and February 2011, Betelgeuse was observed using the Astronomical Multi-BEam combineR (AMBER) instrument of the Very Large Telescope Interferometer (VLTI) in the H and K bands. Using the medium spectral resolution of the instrument (R ~ 1500), we were able to investigate the carbon monoxide band heads and the water-vapor bands. We used two different approaches to analyse our data: a model fit in both the continuum and absorption lines and then a fit with a radiative hydrodynamics (RHD) simulation. Results: Using the continuum data, we derive a uniform disk diameter of 41.01 ± 0.41 mas, a power law type limb-darkened disk diameter of 42.28 ± 0.43 mas and a limb-darkening exponent of 0.155 ± 0.009. Within the absorption lines, using a single layer model, we obtain parameters of the MOLsphere. Using a RHD simulation, we unveil the convection pattern in the visibilities. Conclusions: We derived a new value of the angular diameter of Betelgeuse in the K band continuum. Our observations in the absorption lines are well reproduced by a molecular layer at 1.2 stellar radii containing both CO and H2O. The visibilities at higher spatial frequencies are matching a convection pattern in a RHD simulation. Based on AMBER observations made with ESO Telescopes at the Paranal Observatory under programmes ID 086.D-0351 and 286.D-5036(A).Table 1 is available in electronic form at http://www.aanda.org

  18. The intrinsic values and color excesses of (B-V) for 115 F-K supergiants

    NASA Technical Reports Server (NTRS)

    Kelsall, T.

    1972-01-01

    Color excesses in B-V are determined indirectly from a study of Stromgren's b-y color for a sample of F0 - K5 supergiants. The resulting E(B-V)'s are estimated to have an expected precision of + or - 0.05. With the calculated color excesses and the observed values of B-V given in various catalogs, the run of B-V with spectral type is obtained. This B-V/(spectral type) relationship is compared with those found previously by other investigators.

  19. INTEGRAL observations of OAO 1657-415: gamma-ray tomography of a B supergiant

    E-print Network

    M. Denis; T. Bulik; R. Marcinkowski

    2005-03-14

    OAO 1657-415 is an accreting pulsar in an eclipsing binary system. We analyzed the INTEGRAL core program observations of this object and obtained the eclipse light curve in the soft gamma-ray band between 15 and 40 keV. We note that the gamma rays from the pulsar allow to probe the density profile of the outer layers of the B supergiant companion. We find that the density profile of the outer layer can be described by a power law with the index $\\alpha = 8.5$. We also note that the fit hints toward smaller inclinations of the system within the allowed range 60-90 degrees.

  20. The ARAUCARIA Project - First Observations of Blue Supergiants in NGC 3109

    NASA Astrophysics Data System (ADS)

    Evans, C.; Bresolin, F.; Urbaneja, M.; Peitrzy?ski, G.; Gieren, W.; Kudritzki, R.-P.

    2006-12-01

    NGC 3109 is an irregular galaxy at the edge of the Local Group at a distance of 1.3 Mpc. Here we present new VLT observations of its young, massive star population, which have allowed us to probe stellar abundances and kinematics for the first time. The mean oxygen abundance obtained from early B-type supergiants confirms suggestions that NGC 3109 is very metal poor. In this context we advocate studies of the stellar population of NGC 3109 as a compelling target for future Extremely Large Telescopes (ELTs).

  1. Pulsation and Mass Loss Across the HR Diagram: From OB stars to Cepheids to Red Supergiants

    E-print Network

    Neilson, Hilding R

    2013-01-01

    Both pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation driven mass loss in massive main sequence stars, classical Cepheids and red supergiants and present some challenges remaining.

  2. VizieR Online Data Catalog: 40 field red supergiants in the SMC (Meliani+, 1995)

    NASA Astrophysics Data System (ADS)

    Meliani, M. T.; Barbuy, B.; Richtler, T.

    1996-01-01

    Low-resolution spectra (~5A) for 40 red supergiants in the Small Magellanic Cloud were compared with synthetic spectra, and their metallicities were derived. A mean metallicity of [Fe/He]=-0.71 is found for 38 stars cooler than Teff<4500K. Using the stellar parameters derived, the carbon abundances were determined by comparing synthetic spectra at the G-band region to the observed spectra. A mean {epsilon}(C)=7.85 is found, clearly higher than the low values suggested in the literature for the H II regions. (45 data files).

  3. The progenitor of supernova 1993J - A stripped supergiant in a binary system?

    NASA Technical Reports Server (NTRS)

    Podsiaklowski, PH.; Hsu, J. J. L.; Joss, P. C.; Ross, R. R.

    1993-01-01

    Supernova 1993J in the spiral galaxy M81 is the brightest supernova since SN1987A and, like the latter, appears to be another 'peculiar' type II supernova. The available photometry of the supernova region before the explosion requires the presence of at least two supergiants (one of early spectral type and the other of late type), but the actual progenitor has yet to be identified. We show that the explosion of a late-type supergiant can explain the initial sharp peak in the supernova light curve, provided that the star had lost almost all of its hydrogen-rich envelope before the explosion. In our model, the secondary brightening of the supernova, about 10 days later, is then a consequence of the radioactive decay of Ni-56 (and subsequently Co-56) produced in the explosion. The progenitor could have lost its hydrogen-rich envelope either in a strong stellar wind or, as seems more likely, through mass transfer to a companion star. In the latter case, the companion should reappear after the supernova photosphere has receded, the system having become a binary composed of a neutron star with a massive stellar companion.

  4. THE YELLOW SUPERGIANT PROGENITOR OF THE TYPE II SUPERNOVA 2011dh IN M51

    SciTech Connect

    Maund, J. R. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej, DK-2100 Copenhagen Oe (Denmark); Fraser, M.; Smartt, S. J.; Kotak, R.; Magill, L. [Astrophysics Research Center, School of Mathematics and Physics, Queens University Belfast, Belfast, BT7 1NN (United Kingdom); Ergon, M.; Sollerman, J. [Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University, 106 91 Stockholm (Sweden); Pastorello, A. [Dipartimento di Astronomia, Universita di Padova, Vicolo dell'Osservatorio 3, 35122 Padova (Italy); Benetti, S.; Botticella, M.-T.; Valenti, S. [INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova (Italy); Bufano, F. [INAF-Osservatorio Astronomico di Catania, Via S.Sofia 78, 95123 Catania (Italy); Danziger, I. J. [INAF Osservatorio Astronomico di Trieste and Dipartimento di Fisica, Sezione di Astronomia, Universit di Trieste, via G.B. Tiepolo 11, 34131 Trieste (Italy); Stephens, A. W., E-mail: justyn@dark-cosmology.dk [Gemini Observatory, 670 North Aohoku Place, Hilo, HI 96720 (United States)

    2011-10-01

    We present the detection of the putative progenitor of the Type IIb SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the supernova (SN) in the pre-explosion images was determined to within 23 mas. The progenitor candidate is consistent with an F8 supergiant star (logL/L{sub sun} = 4.92 {+-} 0.20 and T {sub eff} = 6000 {+-} 280 K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M{sub ZAMS} = 13 {+-} 3 M{sub sun}. The possibility of the progenitor source being a cluster is rejected, on the basis of: (1) the source not being spatially extended, (2) the absence of excess H{alpha} emission, and (3) the poor fit to synthetic cluster spectral energy distributions (SEDs). It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest that the companion does not contribute significantly. Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax and suggest that a large amount of the progenitor's hydrogen envelope was removed before explosion. Late-time observations will reveal if the yellow supergiant or the putative companion star were responsible for this SN explosion.

  5. The Yellow Supergiant Progenitor of the Type II Supernova 2011dh in M51

    NASA Astrophysics Data System (ADS)

    Maund, J. R.; Fraser, M.; Ergon, M.; Pastorello, A.; Smartt, S. J.; Sollerman, J.; Benetti, S.; Botticella, M.-T.; Bufano, F.; Danziger, I. J.; Kotak, R.; Magill, L.; Stephens, A. W.; Valenti, S.

    2011-10-01

    We present the detection of the putative progenitor of the Type IIb SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the supernova (SN) in the pre-explosion images was determined to within 23 mas. The progenitor candidate is consistent with an F8 supergiant star (logL/L sun = 4.92 ± 0.20 and T eff = 6000 ± 280 K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M ZAMS = 13 ± 3 M sun. The possibility of the progenitor source being a cluster is rejected, on the basis of: (1) the source not being spatially extended, (2) the absence of excess H? emission, and (3) the poor fit to synthetic cluster spectral energy distributions (SEDs). It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest that the companion does not contribute significantly. Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax and suggest that a large amount of the progenitor's hydrogen envelope was removed before explosion. Late-time observations will reveal if the yellow supergiant or the putative companion star were responsible for this SN explosion.

  6. DOUBLE BOW SHOCKS AROUND YOUNG, RUNAWAY RED SUPERGIANTS: APPLICATION TO BETELGEUSE

    SciTech Connect

    Mackey, Jonathan; Mohamed, Shazrene; Neilson, Hilding R.; Langer, Norbert; Meyer, Dominique M.-A., E-mail: jmackey@astro.uni-bonn.de [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany)

    2012-05-20

    A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow shock. In late evolutionary stages these stars may undergo rapid transitions from red to blue and vice versa on the Hertzsprung-Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks. Recent three-dimensional simulations of the bow shock produced by the nearby runaway red supergiant (RSG) Betelgeuse, under the assumption of a constant wind, indicate that the bow shock is very young (<30, 000 years old), hence Betelgeuse may have only recently become an RSG. To test this possibility, we have calculated stellar evolution models for single stars which match the observed properties of Betelgeuse in the RSG phase. The resulting evolving stellar wind is incorporated into two-dimensional hydrodynamic simulations in which we model a runaway blue supergiant (BSG) as it undergoes the transition to an RSG near the end of its life. We find that the collapsing BSG wind bubble induces a bow shock-shaped inner shell around the RSG wind that resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow shock generated by the now defunct BSG wind's interaction with the ISM. We suggest that this outer shell could explain the bar feature located (at least in projection) just in front of Betelgeuse's bow shock.

  7. X-RAY PHOTOIONIZED BUBBLE IN THE WIND OF VELA X-1 PULSAR SUPERGIANT COMPANION

    SciTech Connect

    Krticka, Jiri; Skalicky, Jan [Ustav teoreticke fyziky a astrofyziky, Masarykova univerzita, Kotlarska 2, CZ-611 37 Brno (Czech Republic); Kubat, Jiri [Astromomicky ustav Akademie ved Ceske republiky, Fricova 298, CZ-251 65 Ondrejov (Czech Republic)

    2012-10-01

    Vela X-1 is the archetype of high-mass X-ray binaries (HMXBs), composed of a neutron star and a massive B supergiant. The supergiant is a source of a strong radiatively driven stellar wind. The neutron star sweeps up this wind and creates a huge amount of X-rays as a result of energy release during the process of wind accretion. Here, we provide detailed NLTE models of the Vela X-1 envelope. We study how the X-rays photoionize the wind and destroy the ions responsible for the wind acceleration. The resulting decrease of the radiative force explains the observed reduction of the wind terminal velocity in a direction to the neutron star. The X-rays create a distinct photoionized region around the neutron star filled with a stagnating flow. The existence of such photoionized bubbles is a general property of HMXBs. We unveil a new principle governing these complex objects, according to which there is an upper limit to the X-ray luminosity the compact star can have without suspending the wind due to inefficient line driving.

  8. SLOW RADIATION-DRIVEN WIND SOLUTIONS OF A-TYPE SUPERGIANTS

    SciTech Connect

    Cure, M. [Departamento de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso Av. Gran Bretana 1111, Casilla 5030, Valparaiso (Chile); Cidale, L.; Granada, A., E-mail: michel.cure@uv.cl [Departamento de EspectroscopIa, Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata (UNLP), and Instituto de Astrofisica La Plata, CCT La Plata, CONICET-UNLP Paseo del Bosque S/N, 1900 La Plata (Argentina)

    2011-08-10

    The theory of radiation-driven winds succeeded in describing terminal velocities and mass-loss rates of massive stars. However, for A-type supergiants the standard m-CAK solution predicts values of mass loss and terminal velocity higher than the observed values. Based on the existence of a slow wind solution in fast rotating massive stars, we explore numerically the parameter space of radiation-driven flows to search for new wind solutions in slowly rotating stars that could explain the origin of these discrepancies. We solve the one-dimensional hydrodynamical equation of rotating radiation-driven winds at different stellar latitudes and explore the influence of ionization changes throughout the wind in the velocity profile. We have found that for particular sets of stellar and line-force parameters, a new slow solution exists over the entire star when the rotational speed is slow or even zero. In the case of slow rotating A-type supergiant stars, the presence of this novel slow solution at all latitudes leads to mass losses and wind terminal velocities which are in agreement with the observed values. The theoretical wind-momentum-luminosity relationship derived with these slow solutions shows very good agreement with the empirical relationship. In addition, the ratio between the terminal and escape velocities, which provides a simple way to predict stellar wind energy and momentum input into the interstellar medium, is also properly traced.

  9. Study of the extinction law in M31 and selection of red supergiants

    NASA Astrophysics Data System (ADS)

    Nedialkov, Petko; Veltchev, Todor

    2015-01-01

    An average value of the total-to-selective-extinction ratio R_{V}=3.8 ± 0.4 in M31 is obtained by means of two independent methods and by use of the analytical formula of Cardelli, Clayton & Mathis (1989). This result differs from previous determinations as well from the `standard' value 3.1 for the Milky Way. The derived individual extinctions for blue and red luminous stars from the catalogue of Magnier et al. (1992) are in good agreement with recent estimates for several OB associations in M31 and thus the issue about the assumed optical opacity of the spiral disk still remains open. The presented list of 113 red supergiant candidates in M31 with their extinctions and luminosities contains 60 new objects of this type which are not identified in other publications. It is supplemented with further 290 stars dereddened on the base of results for their closest neighbors. The luminosity function of all red supergiant candidates and the percentage of those with progenitors over 20 M_{?} suggests that the evolution of massive stars in M31 resembles that in other Local Group galaxies.

  10. Departure from centrosymmetry of red giants and supergiants measured with VLTI/AMBER

    NASA Astrophysics Data System (ADS)

    Cruzalèbes, P.; Jorissen, A.; Chiavassa, A.; Paladini, C.; Rabbia, Y.; Spang, A.

    2015-02-01

    We study a sample of 16 bright and well-resolved late-type stars (10 O-rich giants, 2 red supergiants, and 4 C-rich giants) using the ESO VLTI/AMBER facility at medium resolution (R=1500}) in the K band to detect and measure the deviation from centrosymmetry of their resolved surface brightness distribution. As indicator for departure from centrosymmetry, we use the centrosymmetry parameter (CSP). We observe that CSP increases along the asymptotic giant branch, reaching values as large as 30°. These large CSP values are likely attributable to a few large photospheric convective cells. Carbon stars like W Ori and R Scl, being close to the AGB tip, have the second largest CSP values (17.6° and 22.3°, respectively), being only surpassed by the M5.5Ib/II supergiant T Cet (with CSP of 30.4°.). For K and early M giants, CSP values are smaller, never exceeding 10°, with a clear tendency to increase with the atmospheric pressure scaleheight. This supports the hypothesis that the observed deviations from centrosymmetry are somehow related to convective cells, whose size depends upon the atmospheric pressure scaleheight.

  11. The Fundamental Parameters and Chromospheric Structure of the M Supergiant VV Cephei

    NASA Astrophysics Data System (ADS)

    Bennett, Philip D.

    2013-07-01

    The long-period binary VV Cephei (M2 Iab + B0-2, V=4.9, P=20.34 yr) is the brightest M supergiant eclipsing binary in the sky. The M star primary is a close spectral match to that of Betelgeuse. In the ultraviolet (UV), the early B-type hot companion dominates the spectrum, and as the system emerges from eclipse, the line of sight to the B star probes deep into the outer atmosphere (the "chromosphere") of the M supergiant. The UV spectrum of VV Cep has been observed from total eclipse (in 1997-98) through quadrature (2002) and periastron (2005) at a total of 22 epochs, 20 of these using STIS high-resolution ( 100,000) ultraviolet spectroscopy from the Hubble Space Telescope, and two with the Far Ultraviolet Spectroscopic Explorer satellite. I will present a brief overview of spectrum formation in the system, and focus on the subset of the STIS observations (those immediately following the egress from totality) that probed the chromosphere of VV Cephei. From these observations, I have constructed a spatially-resolved empirical model chromosphere that includes the temperature, density, velocity, and ionization structure of the outer atmosphere of VV Cep above the classical photosphere. I will present these results, and also constraints on the fundamental stellar and orbital parameters provided by these UV observations.

  12. Spectroscopic and Temporal Properties of Supergiant Fast X-ray Transients with Swift

    NASA Astrophysics Data System (ADS)

    Romano, Patrizia; Kennea, J. A.; Vercellone, S.; Burrows, D. N.; Cusumano, G.; Esposito, P.; Farinelli, R.; Krimm, H. A.; La Parola, V.; Mangano, V.; Pagani, C.; Gehrels, N.

    2011-09-01

    We present a review of the Swift Supergiant Fast X-ray Transients (SFXT) project. Swift has recently opened a brand new way of investigating this class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. Thanks to its scheduling flexibility, Swift has allowed us to regularly monitor a small sample of SFXTs with 2-3 observations per week (1-2 ks) with the X-Ray Telescope (XRT) over their entire visibility period (9 months/year) for over 2 years. This intense monitoring has allowed us to study them throughout all phases of their lives (outbursts, intermediate level, and quiescence) and to determine the long-term properties and their duty cycles, through very sensitive and non-serendipitous observations. We also monitored one source along its whole orbital period. Furthermore, thanks to its autonomous and rapid repointing, Swift has allowed us for the first time to catch and study, from optical to hard X-ray, the bright outbursts, and to follow them in the X-ray for days, thus determining the actual duration of the outburst episodes and the shape of their X-ray spectra through simultaneous broadband spectroscopy. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0.

  13. Usage of Red supergiant spectral features as age indicators in starburst regions

    E-print Network

    Y. D. Mayya

    1997-04-09

    We investigate techniques that can be used to determine ages of starburst regions containing populations beyond their early nebular phase. In particular, we study the strength of the CaII triplet (lambda 8498, 8542, 8662 Ang) and the CO index (2.31-2.40 micron band) using synthetic models as the starburst evolves. For an instantaneous burst of star formation both of these absorption features remain strongest between 7-14 Myr corresponding to the red supergiant population. The detailed evolutionary behavior of the starburst is strongly metallicity dependent. Low metallicity starburst models successfully reproduce the distribution of equivalent widths of CaII triplet with age in Large Magellanic Cloud clusters. The clusters in the red supergiant phase strongly favor the stellar evolutionary models incorporating mass-loss rates higher than the standard values. We suggest usage of diagrams involving CaII triplet equivalent width, CO index and nebular recombination lines to infer the history as well as age of starburst regions.

  14. Luminous and Variable Stars in M31 and M33. I. The Warm Hypergiants and Post-Red Supergiant Evolution

    NASA Astrophysics Data System (ADS)

    Humphreys, Roberta M.; Davidson, K.; Grammer, S.; Martin, J. C.; Weis, K.

    2013-06-01

    The progenitors of the Type IIP supernovae have an apparent upper mass limit of ~ 20 solar masses suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very few post-red supergiants are known. We have identified a small group of luminous stars in M31 and M33 that are candidates for post-red supergiant evolution. These stars have A -- F-type supergiant absorption line spectra and strong hydrogen emission, hence the warm hypergiant name. Their spectra are also distinguished by the Ca II triplet and [Ca II] doublet in emission formed in a low density circumstellar environment. They all have significant near- and mid-infrared excess radiation due to free-free emission and thermal emission from dust. We discuss their wind parameters and mass loss rates which range from a few times 10^-6 to 10^-4 solar masses per year. On an HR Diagram, these stars will overlap the region of the LBVs at maximum light, however the warm hypergiants are not LBVs. Their winds are not optically thick and they have no significant variability. We suggest, howvwr, that the warm hypergiants may be the progenitors of the ``less luminous'' LBVs such as R71 and even SN1987A.

  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 the H-rich envelope contains less than 1% of the total mass, the star is a blue supergiant. For intermediate situations, intermediate colors and effective temperatures are obtained. Yellow progenitors for core-collapse supernovae can be explained by models with an enhanced mass-loss rate, while the red progenitors are better fitted by models with the standard mass-loss rate. Tracks of the enhanced mass loss rates models are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A60

  16. 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.

  17. The high-latitude F supergiant IRAS 18095 + 2704 - A proto-planetary nebula

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.; Kwok, Sun; Volk, Kevin M.

    1988-01-01

    The paper reports the discovery of a new high-latitude F supergiant, IRAS 18095 + 2704, which shows a large excess in the far-infrared. Ground-based observations have identified it as a V = 10.4 mag F3 Ib star which displays light and velocity variability. Comparison with the post-asymptotic giant branch (AGB) evolution model of Volk and Kwok suggests that it is an excellent candidate for a protoplanetary nebula. Model fitting of the spectrum of 18095 + 2704 from 0.35 to 100 microns suggests that it evolved from the AGB approximately 265 yr ago and had a mass-loss rate of 0.00003 solar mass/yr at the end of the AGB.

  18. The high-latitude F supergiant IRAS 18095 + 2704 - A proto-planetary nebula

    NASA Astrophysics Data System (ADS)

    Hrivnak, Bruce J.; Kwok, Sun; Volk, Kevin M.

    1988-08-01

    The paper reports the discovery of a new high-latitude F supergiant, IRAS 18095 + 2704, which shows a large excess in the far-infrared. Ground-based observations have identified it as a V = 10.4 mag F3 Ib star which displays light and velocity variability. Comparison with the post-asymptotic giant branch (AGB) evolution model of Volk and Kwok suggests that it is an excellent candidate for a protoplanetary nebula. Model fitting of the spectrum of 18095 + 2704 from 0.35 to 100 microns suggests that it evolved from the AGB approximately 265 yr ago and had a mass-loss rate of 0.00003 solar mass/yr at the end of the AGB.

  19. The Chromospheric Structure and Wind of the K-Supergiant Lambda Velorum

    NASA Astrophysics Data System (ADS)

    Carpenter, Kenneth G.; Ayres, T. R.; Brown, A.; Harper, G. M.; Wahlgren, G. M.

    2011-01-01

    Recently, the 1326-1466 Å region of the FUV spectrum of the K4 Ib-II supergiant Lambda Vel was observed with the Cosmic Origins Spectrograph (COS) on HST, as part of the Ayres and Redfield Cycle 17 SNAP program "SNAPing Coronal Iron.” This spectrum covers a region not previously recorded in Lambda Vel at high resolution and, in a mere 20 minutes of exposure, reveals an amazing treasure trove of information. It shows a wide variety of strong atomic and molecular emission lines formed in the chromosphere and multiple atomic absorption lines formed in the stellar wind, both superposed on a bright chromospheric continuum. Further evidence of the stellar wind is seen in the P Cygni profiles presented by the C II (UV 1) lines near 1335 Å. We combine this COS data with archival GHRS spectra of other selected FUV and NUV regions to better characterize the outer atmospheric structure of the star and its massive, outflowing wind.

  20. 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.

  1. 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.

  2. 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.

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

    SciTech Connect

    Van Dyk, Schuyler D. [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Cenko, S. Bradley; Filippenko, Alexei V., E-mail: vandyk@ipac.caltech.edu, E-mail: cenko@berkeley.edu, E-mail: afilippenko@berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); 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).

  4. Supergiant Fast X-ray Transients: A Case Study for LOFT

    NASA Astrophysics Data System (ADS)

    Romano, Patrizia; Mangano, V.; Bozzo, E.; Esposito, P.; Ferrigno, C.

    2013-04-01

    LOFT, the Large Observatory For X-ray Timing, is a new space mission concept selected by ESA in February 2011 and currently competing for a launch of opportunity in 2022. LOFT will carry a coded mask Wide Field Monitor (WFM) and a 10-m^2 class collimated X-ray Large Area Detector (LAD) operating in the energy range 2-80 keV. The instruments on-board LOFT will dramatically deepen our knowledge of Supergiant Fast X-ray Transients, a class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. The LAD and the WFM will provide simultaneous high S/N broad-band and time-resolved spectroscopy in several intensity states, long term monitoring that will yield new determinations of orbital periods, as well as spin periods. We show the results of an extensive set of simulations based on the Swift broad-band and detailed XMM-Newton observations we collected up to now. Our simulations describe the outbursts at several intensities (F(2-10 keV)=5.9E-9 to 5.5E-10 erg cm-2 s-1), the intermediate and most common state (1E-11 erg cm-2 s-1), and the low state (1.2E-12 to 5E-13 erg cm-2 s-1). We also considered large variations of NH and the presence of emission lines, as observed by Swift and XMM-Newton. We acknowledge financial contribution from ASI-INAF I/004/11/0 and I/021/12/0.

  5. Young red supergiants and the near infrared light appearance of disk galaxies

    E-print Network

    James E. Rhoads

    1997-10-17

    Disk galaxies often show prominent nonaxisymmetric features at near-infrared wavelengths. Such features may indicate variations in the surface density of stellar mass, contributions from young red supergiants in star forming regions, or substantial dust obscuration. To distinguish among these possibilities, we have searched for spatial variations in the 2.3 micron photometric CO index within the disks of three nearby galaxies (NGC 278, NGC 2649, & NGC 5713). This index measures the strength of the absorption bands of molecular CO in stellar atmospheres, and is strong in cool, low surface-gravity stars, reaching the largest values for red supergiants. We observe significant spatial CO index variations in two galaxies (NGC 278 & NGC 5713), indicating that the dominant stellar population in the near-infrared is not everywhere the same. Central CO index peaks are present in two galaxies; these could be due to either metallicity gradients or recent star formation activity. In addition, significant azimuthal CO index variations are seen in NGC 278. Because strong azimuthal metallicity gradients are physically implausible in disk galaxies, these features are most naturally explained by the presence of a young stellar population. The fraction of 2 micron light due to young stellar populations in star forming regions can be calculated from our data. Overall, young stellar populations can contribute ~3% of a (normal) galaxy's near infrared flux. Locally, this fraction may rise to ~33%. Thus, young stars do not dominate the total near infrared flux, but can be locally dominant in star forming regions, and can bias estimates of spiral arm amplitude or other nonaxisymmetric structures in galaxies' mass distributions.

  6. The ring nebula around the blue supergiant SBW1: pre-explosion snapshot of an SN 1987A twin

    NASA Astrophysics Data System (ADS)

    Smith, Nathan; Arnett, W. David; Bally, John; Ginsburg, Adam; Filippenko, Alexei V.

    2013-02-01

    SBW1 is a B-type supergiant surrounded by a ring nebula that is a nearby twin of SN 1987A's progenitor and its circumstellar ring. We present images and spectra of SBW1 obtained with the Hubble Space Telescope (HST), the Spitzer Space Telescope and Gemini South. HST images of SBW1 do not exhibit long Rayleigh-Taylor (RT) fingers, which are presumed to cause the `hotspots' in the SN 1987A ring when impacted by the blast wave, but instead show a geometrically thin (?R/R ? 0.05) clumpy ring. The radial mass distribution and size scales of inhomogeneities in SBW1's ring closely resemble those in the SN 1987A ring, but the more complete disc expected to reside at the base of the RT fingers is absent in SBW1. This structure may explain why portions of the SN 1987A ring between the hotspots have not yet brightened, more than 15 years after the first hotspots appeared. The model we suggest does not require a fast wind colliding with a previous red supergiant wind, because a slowly expanding equatorial ring may be ejected by a rotating blue supergiant star or in a close binary system. More surprisingly, high-resolution images of SBW1 also reveal diffuse emission filling the interior of the ring seen in H? and in thermal-infrared (IR) emission; ˜190 K dust dominates the 8-20 ?m luminosity (but contains only 10-5 M? of dust). Cooler (˜85 K) dust resides in the equatorial ring itself (and has a dust mass of at least 5 × 10-3 M?). Diffuse emission extends inward to ˜1 arcsec from the central star, where a paucity of H? and IR emission suggests an inner hole excavated by the B-supergiant wind. We propose that diffuse emission inside the ring arises from an ionized flow of material photoevaporated from the dense ring, and its pressure prevents the B-supergiant wind from advancing in the equatorial plane. This inner emission could correspond to a structure hypothesized to reside around Sk-69°202 that was never directly detected. If this interpretation is correct, it would suggest that photoionization can play an important dynamical role in shaping the ring nebula, and we speculate that this might help explain the origin of the polar rings around SN 1987A. In effect, the photoevaporative flow shields the outer bipolar nebula at low latitudes, whereas the blue supergiant wind expands freely out the poles and clears away the polar caps of the nebula; the polar rings reside at the intersection of these two zones.

  7. The ARAUCARIA Project: VLT-FORS Spectroscopy of Blue Supergiants in NGC 3109-Classifications, First Abundances, and Kinematics

    NASA Astrophysics Data System (ADS)

    Evans, C. J.; Bresolin, F.; Urbaneja, M. A.; Pietrzy?ski, G.; Gieren, W.; Kudritzki, R.-P.

    2007-04-01

    We have obtained multiobject spectroscopy of luminous blue supergiants in NGC 3109, a galaxy at the periphery of the Local Group at ~1.3 Mpc. We present a detailed catalog including finding charts, V and I magnitudes, spectral classifications, and stellar radial velocities. The radial velocities are seen to trace the rotation curves obtained from studies of the H I gas. From quantitative analysis of eight B-type supergiants we find a mean oxygen abundance of 12+log(O/H)=7.76+/-0.07 (1 ? systematic uncertainty), with a median result of 7.8. Given its distance, we highlight NGC 3109 as the ideal example of a low-metallicity, dark-matter-dominated dwarf galaxy for observations with the next generation of ground-based extremely large telescopes. Based on observations at the European Southern Observatory Very Large Telescope in program 171.D-0004.

  8. The Araucaria Project: the Local Group Galaxy WLM--Distance and metallicity from quantitative spectroscopy of blue Supergiants

    E-print Network

    M. A. Urbaneja; R. -P. Kudritzki; F. Bresolin; N. Przybilla; W. Gieren; G. Pietrzynski

    2008-05-22

    The quantitative analysis of low resolution spectra of A and B supergiants is used to determine a distance modulus of 24.99 +/- 0.10 mag (995 +/- 46 Kpc) to the Local Group galaxy WLM. The analysis yields stellar effective temperatures and gravities, which provide a distance through the Flux weighted Gravity--Luminosity Relationship (FGLR). Our distance is 0.07 mag larger than the most recent results based on Cepheids and the tip of the RGB. This difference is within the 1-sigma overlap of the typical uncertainties quoted in these photometric investigations. In addition, non-LTE spectral synthesis of the rich metal line spectra (mostly iron, chromium and titanium) of the A supergiants is carried out, which allows the determination of stellar metallicities. An average metallicity of -0.87 +/- 0.06 dex with respect to solar metallicity is found.

  9. The Araucaria Project: the Local Group Galaxy WLM--Distance and metallicity from quantitative spectroscopy of blue Supergiants

    E-print Network

    Urbaneja, M A; Bresolin, F; Przybilla, N; Gieren, W; Pietrzynski, G

    2008-01-01

    The quantitative analysis of low resolution spectra of A and B supergiants is used to determine a distance modulus of 24.99 +/- 0.10 mag (995 +/- 46 Kpc) to the Local Group galaxy WLM. The analysis yields stellar effective temperatures and gravities, which provide a distance through the Flux weighted Gravity--Luminosity Relationship (FGLR). Our distance is 0.07 mag larger than the most recent results based on Cepheids and the tip of the RGB. This difference is within the 1-sigma overlap of the typical uncertainties quoted in these photometric investigations. In addition, non-LTE spectral synthesis of the rich metal line spectra (mostly iron, chromium and titanium) of the A supergiants is carried out, which allows the determination of stellar metallicities. An average metallicity of -0.87 +/- 0.06 dex with respect to solar metallicity is found.

  10. The ARAUCARIA Project: VLT-FORS spectroscopy of blue supergiants in NGC 3109 - Classifications, first abundances and kinematics

    E-print Network

    C. J. Evans; F. Bresolin; M. A. Urbaneja; G. Pietrzynski; W. Gieren; R. -P. Kudritzki

    2006-12-05

    We have obtained multi-object spectroscopy of luminous blue supergiants in NGC 3109, a galaxy at the periphery of the Local Group at ~1.3 Mpc. We present a detailed catalog including finding charts, V and I magnitudes, spectral classifications, and stellar radial velocities. The radial velocities are seen to trace the rotation curves obtained from studies of the HI gas. From quantitative analysis of eight B-type supergiants we find a mean oxygen abundance of 12+log(O/H) = 7.76 +/-0.07 (1-sigma systematic uncertainty), with a median result of 7.8. Given its distance, we highlight NGC 3109 as the ideal example of a low metallicity, dark-matter dominated, dwarf galaxy for observations with the next generation of ground-based extremely large telescopes (ELTs).

  11. The ARAUCARIA Project: VLT-FORS spectroscopy of blue supergiants in NGC 3109 - Classifications, first abundances and kinematics

    E-print Network

    Evans, C J; Urbaneja, M A; Pietrzynski, G; Gieren, W; Kudritzki, R P

    2006-01-01

    We have obtained multi-object spectroscopy of luminous blue supergiants in NGC 3109, a galaxy at the periphery of the Local Group at ~1.3 Mpc. We present a detailed catalog including finding charts, V and I magnitudes, spectral classifications, and stellar radial velocities. The radial velocities are seen to trace the rotation curves obtained from studies of the HI gas. From quantitative analysis of eight B-type supergiants we find a mean oxygen abundance of 12+log(O/H) = 7.76 +/-0.07 (1-sigma systematic uncertainty), with a median result of 7.8. Given its distance, we highlight NGC 3109 as the ideal example of a low metallicity, dark-matter dominated, dwarf galaxy for observations with the next generation of ground-based extremely large telescopes (ELTs).

  12. The Araucaria Project: The Local Group Galaxy WLM-Distance and Metallicity from Quantitative Spectroscopy of Blue Supergiants

    NASA Astrophysics Data System (ADS)

    Urbaneja, Miguel A.; Kudritzki, Rolf-Peter; Bresolin, Fabio; Przybilla, Norbert; Gieren, Wolfgang; Pietrzy?ski, Grzegorz

    2008-09-01

    The quantitative analysis of low-resolution spectra of A and B supergiants is used to determine a distance modulus of 24.99+/-0.10 mag (995+/-46 kpc) to the Local Group galaxy WLM. The analysis yields stellar effective temperatures and gravities, which provide a distance through the flux-weighted gravity-luminosity relationship (FGLR). Our distance is 0.07 mag larger than the most recent results based on Cepheids and the tip of the red giant branch. This difference is within the 1 ? overlap of the typical uncertainties quoted in these photometric investigations. In addition, non-LTE spectral synthesis of the rich metal-line spectra (mostly iron, chromium, and titanium) of the A supergiants is carried out, which allows the determination of stellar metallicities. An average metallicity of -0.87+/-0.06 dex with respect to solar metallicity is found. Based on VLT observations for ESO Large Program 171.D-0004.

  13. The supergiant fast X-ray transient IGRJ18483-0311 in quiescence: XMM-Newton, Swift and Chandra observations

    Microsoft Academic Search

    A. Giunta; E. Bozzo; F. Bernardini; G. Israel; L. Stella; M. Falanga; S. Campana; A. Bazzano; A. J. Dean; M. Mendez

    2009-01-01

    IGRJ18483-0311 was discovered with INTEGRAL in 2003 and later classified as a supergiant fast X-ray transient. It was observed in outburst many times, but its quiescent state is still poorly known. Here, we present the results of XMM-Newton, Swift and Chandra observations of IGRJ18483-0311. These data improved the X-ray position of the source, and provided new information on the timing

  14. A new outburst from the Supergiant Fast X-ray Transient IGRJ17544-2619 caught by Swift

    Microsoft Academic Search

    L. Sidoli; P. Romano; V. Mangano; J. A. Kennea; G. Cusumano; S. Campana; S. Vercellone; D. N. Burrows; N. Gehrels

    2008-01-01

    The Swift satellite has observed a new outburst from IGR J17544-2619, a Supergiant Fast X-ray Transient discovered in September 2003 with INTEGRAL (Sunyaev et al., ATel#190). The Swift Burst Alert Telescope (BAT) triggered on March 31 at 20:50:45 UT, (trigger=308224). Swift immediately slewed to the target, so that the NFI onboard Swift started observing it about 162s after the trigger.

  15. Geological and geochemical controls on the formation and distribution of supergiant gas fields in the Russian sedimentary basins

    Microsoft Academic Search

    N. Lopatin

    1996-01-01

    The West Siberian, Barents Sea and Northern Caspian sedimentary basins are the most prolific Russian gas producing regions and include 15 supergiant gas fields each of them content identified gas reserves between 1 x 10[sup 12] m[sup 3] to 11 x 10[sup 12] m[sup 3]. They are Urengoi, Yarnburg, Bovanenkov, Zapoljarnoye, Medvezhie, Charasavey, Kruzenshtern, N.Urengoi, S.Tambey, S.Russkoye, Rusanov, Shtockmanov, Lunin,

  16. 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.

  17. An HST COS "SNAPshot" Spectrum of the K Supergiant ? Vel (K4Ib-II)

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We present a far-ultraviolet spectrum of the K4 Ib-II supergiant ? 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 ? 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 Ly? and the O I (UV 2) triplet emission near ?1304. The molecular CO and H2 fluorescences are weaker than in the early-K giant ? Boo while the Fe II and Cr II lines, also pumped by H I Ly?, are stronger in ? Vel. This pattern of relative line strengths between the two stars is explained by the lower iron-group element abundance in ? Boo, which weakens that star's Fe II and Cr II emission without reducing the molecular fluorescences. The ? Vel spectrum shows fluorescent Fe II, Cr II, and H2 emission similar to that observed in the M supergiant ? Ori, but more numerous well-defined narrow emissions from CO. The additional CO emissions are visible in the spectrum of ? Vel since that star does not have the cool, opaque circumstellar shells that surround ? 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 ? Vel indicates a ~8 × 104 K plasma that is mixed into the cooler chromosphere. Evidence of the stellar wind is seen in the C II ??1334,1335 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-1) and turbulence (~27 versus <21 km s-1) with a more quickly accelerating wind (? = 0.35 versus 0.7) at the time of this COS observation in 2010 than derived from Goddard High Resolution Spectrograph data obtained in 1994. The Fe II and Ni II absorptions are blueshifted by 7.6 km s-1 relative to the chromospheric emission, suggesting formation in lower levels of the accelerating wind and their widths indicate a higher turbulence in the ? Vel wind compared to ? Ori. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

  18. Multiple, short-lived ``stellar prominences'' on O stars: the supergiant ? Cephei

    NASA Astrophysics Data System (ADS)

    Henrichs, H. F.; Sudnik, N.

    2015-01-01

    Many OB stars show unexplained cyclical variability in their winds and in many optical lines, which are formed at the base of the wind. For these stars no dipolar magnetic fields have been detected. We propose that these cyclical variations are caused by the presence of multiple, transient, short-lived, corotating magnetic loops, which we call ``stellar prominences''. We present a simplified model representing these prominences as corotating spherical blobs and fit the rapid variability in the Heii ?4686 line of the O supergiant ? Cep for time-resolved spectra obtained in 1989. Our conclusions are: (1) From model fits we find that the life time of the prominences varies, and is between 2-7 h. (2) The adopted inclination angle is 68° with a rotation period of ~ 4.1 d (but not well constrained). (3) The contribution of non-radial pulsations is negligible (4) Similar behavior is observed in at least 4 other O stars. We propose that prominences are a common phenomenon among O stars.

  19. The Yellow Supergiant Progenitor of the Type II Supernova 2011dh in M51

    E-print Network

    Maund, J R; Ergon, M; Pastorello, A; Smartt, S J; Sollerman, J; Benetti, S; Botticella, M -T; Bufano, F; Danziger, I J; Kotak, R; Magill, L; Stephens, A W; Valenti, S

    2011-01-01

    We present the detection of the progenitor of the Type II SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the SN in the pre-explosion images was determined to within 23mas. The progenitor object was found to be consistent with a F8 supergiant star (log L/L_{\\odot}=4.92+/-0.20 and T_{eff}=6000+/-280K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M_{ZAMS}=13+/-3M_{\\odot}. The possibility of the progenitor source being a cluster is rejected, on the basis of: 1) the source is not spatially extended; 2) the absence of excess H\\alpha\\, emission; and 3) the poor fit to synthetic cluster SEDs. It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest the companion does not contribute significantly. Early ph...

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

    SciTech Connect

    Yang Ming; Jiang, B. W., E-mail: myang@mail.bnu.edu.cn, E-mail: bjiang@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    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.

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

    SciTech Connect

    Gendre, B.; Cutini, S.; D'Elia, V. [ASI Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy)] [ASI Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy); Stratta, G. [Osservatorio Astronomico di Roma, OAR-INAF, via Frascati 33, I-00040, Monte Porzio Catone (Italy)] [Osservatorio Astronomico di Roma, OAR-INAF, via Frascati 33, I-00040, Monte Porzio Catone (Italy); Atteia, J. L.; Klotz, A. [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France)] [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Basa, S. [Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)] [Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Boeer, M. [CNRS, ARTEMIS, UMR 7250, Boulevard de l'Observatoire, BP 4229, F-06304 Nice Cedex 4 (France)] [CNRS, ARTEMIS, UMR 7250, Boulevard de l'Observatoire, BP 4229, F-06304 Nice Cedex 4 (France); Coward, D. M.; Howell, E. J [University of Western Australia, School of Physics, University of Western Australia, Crawley WA 6009 (Australia)] [University of Western Australia, School of Physics, University of Western Australia, Crawley WA 6009 (Australia); Piro, L., E-mail: bruce.gendre@gmail.com [Istituto di Astrofisica e Planetologia Spaziali di Roma, INAF, via fosso del cavaliere 100, I-00133 Roma (Italy)

    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.

  2. Tracing the mass-loss history of B[e] supergiants

    NASA Astrophysics Data System (ADS)

    Kraus, Michaela; Cidale, Lydia S.; Arias, Maria L.; Torres, Andrea F.; Aret, Anna; Fernandes, Marcelo Borges; Muratore, Florencia; Cure, Michel; Oksala, Mary E.

    2013-06-01

    The post-main sequence evolution of massive stars encompasses several phases with strong, often eruptive mass-loss events, including the puzzling B[e] supergiants (B[e]SG). Stars in this group are surrounded by disks which are cool and dense, and give rise to a complex chemistry, producing molecules and dust. The original idea was that these disks have been formed via a steady, but slow, high density equatorially confined wind. However, recent observations revealed that the circumstellar material is located in detached disks or rings, sometimes even multiple rings, favouring a scenario in which mass loss happens episodically rather than smoothly. Furthermore, time-resolved observations of these disk or ring structures implied a high variability in density and kinematics. Some Galactic B[e]SGs were recently found to be in binaries, and in a few cases, the disks are circumbinary instead of circumstellar. We have initiated an observing campaign using high-resolution optical and near-infrared spectroscopy aimed at studying the structure and kinematics of the circumstellar material of B[e]SGs. While in the optical spectral range several forbidden emission lines can be used as ideal tracers for the ionized and neutral atomic disk regions close to the star, near-infrared spectra host band emission from molecules such as CO, which are excellent indicators for the disk conditions at larger distances. Here we present first results and discuss possible mass-loss history scenarios for some of these enigmatic stars.

  3. On the stability of bow shocks generated by red supergiants: the case of IRC -10414

    NASA Astrophysics Data System (ADS)

    Meyer, D. M.-A.; Gvaramadze, V. V.; Langer, N.; Mackey, J.; Boumis, P.; Mohamed, S.

    2014-03-01

    In this Letter, we explore the hypothesis that the smooth appearance of bow shocks around some red supergiants (RSGs) might be caused by the ionization of their winds by external sources of radiation. Our numerical simulations of the bow shock generated by IRC -10414 (the first-ever RSG with an optically detected bow shock) show that the ionization of the wind results in its acceleration by a factor of 2, which reduces the difference between the wind and space velocities of the star and makes the contact discontinuity of the bow shock stable for a range of stellar space velocities and mass-loss rates. Our best-fitting model reproduces the overall shape and surface brightness of the observed bow shock and suggests that the space velocity and mass-loss rate of IRC -10414 are ?50 km s-1 and ?10-6 M? yr-1, respectively, and that the number density of the local interstellar medium is ?3 cm-3. It also shows that the bow shock emission comes mainly from the shocked stellar wind. This naturally explains the enhanced nitrogen abundance in the line-emitting material, derived from the spectroscopy of the bow shock. We found that photoionized bow shocks are ?15-50 times brighter in optical line emission than their neutral counterparts, from which we conclude that the bow shock of IRC -10414 must be photoionized.

  4. Ejecting the envelope of red supergiant stars with jets launched by an inspiralling neutron star

    NASA Astrophysics Data System (ADS)

    Papish, Oded; Soker, Noam; Bukay, Inbal

    2015-05-01

    We study the properties of jets launched by a neutron star (NS) spiralling inside the envelope and core of a red supergiant (RSG). We propose that Thorne-?ytkow objects (TZO) are unlikely to be formed via common envelope (CE) evolution if accretion on to the NS can exceed the Eddington rate with much of the accretion energy directed into jets that subsequently dissipate within the giant envelope. We use the jet-feedback mechanism, where energy deposited by the jets drives the ejection of the entire envelope and part of the core, and find a very strong interaction of the jets with the core material at late phases of the CE evolution. Following our results, we speculate on two rare processes that might take place in the evolution of massive stars. (1) Recent studies have claimed that the peculiar abundances of the HV2112 RSG star can be explained if this star is a TZO. We instead speculate that the rich-calcium envelope comes from a supernova (SN) explosion of a stellar companion that was only slightly more massive than HV2112, such that during its explosion HV2112 was already a giant that intercepted a relatively large fraction of the SN ejecta. (2) We raise the possibility that strong r-process nucleosynthesis, where elements with high atomic weight of A ? 130 are formed, occurs inside the jets that are launched by the NS inside the core of the RSG star.

  5. The velocity gradient in the pseudo-photosphere of the peculiar supergiant HD101584

    E-print Network

    Eric J. Bakker

    1995-10-23

    In this paper preliminary results are presented based on a study of the low and high resolution ultraviolet spectrum of the peculiar supergiant (post-AGB star) HD101584. By a comparison of the low resolution spectrum (1200-3200ang) with standard stars, the star is classified as an A7I, indicating an effective temperature of 8150 K, where literature quotes spectral type F0I. The Doppler shift of the FeII absorption lines in the high resolution spectrum (2500-3000ang) show a relation with the line optical depth. This suggests an expanding accelerating wind, c.q. pseudo-photosphere. The relation is extended by a factor 10^5 in optical depth by using available data from optical HeI and NI lines. The relation suggests that the radial heliocentric velocity of the star is at least 54.5km/s. From the Halpha line a velocity of 96km/s is measured for the terminal velocity of the wind.

  6. The Temperatures of Red Supergiants: how cool are the coolest massive stars?

    NASA Astrophysics Data System (ADS)

    Davies, B.; Kudritzki, R.-P.; Plez, B.; Bergemann, M.; Lançon, A.; Trager, S.; Gazak, Z.; Evans, C.; Chiavassa, A.

    2013-05-01

    We have re-appraised the temperatures of Red Supergiants (RSGs) in the Magellanic Clouds, by studying their spectral energy distributions (SEDs) from 400-2500 nm using VLT+XSHOOTER, in conjunction with MARCS model atmospheres. We determine temperatures using 3 methods: from model fits to the TiO bands in the optical; from model fits to the SED using the line-free continuum in the near-infrared; and from the integrated fluxes. We find that the temperatures from the TiO fits are systematically lower that those from the other methods by several hundred Kelvin. The TiO fits also dramatically over-predict the flux in the near-IR, and imply extinctions which are anomalously low compared to neighbouring stars. In contrast, the SED temperatures provide good fits to the fluxes at all wavelengths other than the TiO bands, are in agreement with the temperatures from the flux integration method, and imply extinctions consistent with nearby stars. We consider a number of ways to reconcile this discrepancy, concluding that 3-D effects are responsible, and that RSG temperatures are much warmer than previously thought.

  7. 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.

  8. Near-infrared identification of the counterpart to X1908+075: a new OB-supergiant X-ray binary

    E-print Network

    Thierry Morel; Yves Grosdidier

    2004-10-07

    We report the near-infrared (IR) identification of the likely counterpart to X1908+075, a highly-absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron star binary systems. Our JHKs-band imaging of the field reveals the existence within the X-ray error boxes of a near-IR source consistent with an early-type star lying at d=7 kpc and suffering A(V)=16 mag of extinction, the latter value being in good agreement with the hydrogen column density derived from a modelling of the X-ray spectrum. Our follow-up, near-IR spectroscopic observations confirm the nature of this candidate and lead to a late O-type supergiant classification, thereby supporting the identification of a new Galactic OB-supergiant X-ray binary.

  9. 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 H?, 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.

  10. 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 3? 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).

  11. IGR J16328-4726: A NEW CANDIDATE SUPERGIANT FAST X-RAY TRANSIENT

    SciTech Connect

    Fiocchi, M.; Bazzano, A.; Natalucci, L.; Ubertini, P. [Instituto di Astrofisica Spaziale e Fisica Cosmica di Roma (INAF), Via Fosso del Cavaliere 100, Roma, I-00133 (Italy); Sguera, V.; Bassani, L. [Instituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (INAF), Via Gobetti 101, Bologna, I-40129 (Italy); Bird, A. J. [School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ (United Kingdom)

    2010-12-10

    The unidentified source IGR J16328-4726 was covered with INTEGRAL observations for a long period ({approx}9.8 Ms) and was undetectable for most of the time while showing a very recurrent micro-activity with a duration from tens of minutes to several hours. We report the discovery of two strong outbursts started at 53420.65 MJD and 54859.99 MJD, respectively, the first with a duration of {approx}1 hr and the second with a lower limit on the duration of {approx}3.5 hr. Furthermore, the sources have been detected in nine other short pointings with significance between 4{sigma} and 5{sigma} as well as in one of the revolutions (during the exposure {approx}130 ks) at a significance level of {approx}7{sigma}. The stronger outburst spectrum is well described by a power-law model with a photon index of {approx}2.0 and a flux of {approx}3.3 x10{sup -10} erg cm{sup -2} s{sup -1} in the 20-50 keV energy band. The weaker outburst and revolution spectra show the same spectral shape and different fluxes. The combined timing and spectral properties observed during the outburst, the recurrent nature of this transient source, the Galactic plane location, a dynamic range >170 in the 0.3-10 keV band and >165 in the 20-50 keV, and the presence of an IR star in the error circle of a Swift X-ray Telescope pointing are suggesting this source as a member of the class of the supergiant fast X-ray transients.

  12. Exploring jet-launching conditions for supergiant fast X-ray transients

    NASA Astrophysics Data System (ADS)

    García, Federico; Aguilera, Deborah N.; Romero, Gustavo E.

    2014-05-01

    Context. In the magneto-centrifugal mechanism for jet formation, accreting neutron stars are assumed to produce relativistic jets only if their surface magnetic field is weak enough (B ~ 108 G). However, the most common manifestation of neutron stars are pulsars, whose magnetic field distribution peaks at B ~ 1012 G. If the neutron star magnetic field has at least this strength at birth, it must decay considerably before jets can be launched in binary systems. Aims: We study the magnetic field evolution of a neutron star that accretes matter from the wind of a high-mass stellar companion so that we can constrain the accretion rate and the impurities in the crust, which are necessary conditions for jet formation. Methods: We solved the induction equation for the diffusion and convection of the neutron star magnetic field confined to the crust, assuming spherical accretion in a simpliflied one-dimensional treatment. We incorporated state-of-the-art microphysics, including consistent thermal evolution profiles, and assumed two different neutron star cooling scenarios based on the superfluidity conditions at the core. Results: We find that in this scenario, magnetic field decay at long timescales is governed mainly by the accretion rate, while the impurity content and thermal evolution of the neutron star play a secondary role. For accretion rates ? ? 10-10 M? yr-1, surface magnetic fields can decay up to four orders of magnitude in ~107 yr, which is the timescale imposed by the evolution of the high-mass stellar companion in these systems. Based on these results, we discuss the possibility of transient jet-launching in strong wind-accreting high-mass binary systems like supergiant fast X-ray transients.

  13. Pulsations of red supergiant pair-instability supernova progenitors leading to extreme mass loss

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.; Langer, Norbert

    2015-01-01

    Recent stellar evolution models show consistently that very massive metal-free stars evolve into red supergiants shortly before they explode. We argue that the envelopes of these stars, which will form pair-instability supernovae, become pulsationally unstable and that this will lead to extreme mass-loss rates despite the tiny metal content of the envelopes. We investigate the pulsational properties of such models and derive pulsationally induced mass-loss rates, which take the damping effects of the mass loss on the pulsations selfconsistently into account. We find that the pulsations may induce mass-loss rates of ~10-4 - 10-2M? yr-1 shortly before the explosions, which may create a dense circumstellar medium. Our results show that very massive stars with dense circumstellar media may stem from a wider initial mass range than pulsational-pair instability supernovae. The extreme mass loss will cease when so much of the hydrogen-rich envelope is lost that the star becomes more compact and stops pulsating. The helium core of these stars therefore remains unaffected, and their fate as pair-instability supernovae remains unaltered. The existence of dense circumstellar media around metal-free pair-instability supernovae can make them brighter and bluer, and they may be easier to detect at high redshifts than previously expected. We argue that the mass-loss enhancement in pair-instability supernova progenitors can naturally explain some observational properties of superluminous supernovae: the energetic explosions of stars within hydrogen-rich dense circumstellar media with little 56Ni production and the lack of a hydrogen-rich envelope in pair-instability supernova candidates with large 56Ni production.

  14. ISOLATED WOLF-RAYET STARS AND O SUPERGIANTS IN THE GALACTIC CENTER REGION IDENTIFIED VIA PASCHEN-{alpha} EXCESS

    SciTech Connect

    Mauerhan, J. C.; Stolovy, S. R. [Infrared Processing and Analysis Center, California Institute of Technology, Mail Code 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Cotera, A. [SETI Institute, 515 North Whisman Road, Mountain View, CA 94043 (United States); Dong, H.; Wang, Q. D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Morris, M. R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Lang, C., E-mail: mauerhan@ipac.caltech.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States)

    2010-12-10

    We report the discovery of 19 hot, evolved, massive stars near the Galactic center region (GCR). These objects were selected for spectroscopy owing to their detection as strong sources of Paschen-{alpha} (P{alpha}) emission-line excess, following a narrowband imaging survey of the central 0.{sup 0}65 x 0.{sup 0}25 (l, b) around Sgr A* with the Hubble Space Telescope. Discoveries include six carbon-type (WC) and five nitrogen-type (WN) Wolf-Rayet stars, six O supergiants, and two B supergiants. Two of the O supergiants have X-ray counterparts having properties consistent with solitary O stars and colliding-wind binaries. The infrared photometry of 17 stars is consistent with the Galactic center distance, but 2 of them are located in the foreground. Several WC stars exhibit a relatively large infrared excess, which is possibly thermal emission from hot dust. Most of the stars appear scattered throughout the GCR, with no relation to the three known massive young clusters; several others lie near the Arches and Quintuplet clusters and may have originated within one of these systems. The results of this work bring the total sample of Wolf-Rayet (WR) stars in the GCR to 88. All sources of strong P{alpha} excess have been identified in the area surveyed with HST, which implies that the sample of WN stars in this region is near completion, and is dominated by late (WNL) types. The current WC sample, although probably not complete, is almost exclusively dominated by late (WCL) types. The observed WR subtype distribution in the GCR is a reflection of the intrinsic rarity of early subtypes (WNE and WCE) in the inner Galaxy, an effect that is driven by metallicity.

  15. MOST Detects g- and p-Modes in the B Supergiant HD 163899 (B2 Ib/II)

    NASA Astrophysics Data System (ADS)

    Saio, H.; Kuschnig, R.; Gautschy, A.; Cameron, C.; Walker, G. A. H.; Matthews, J. M.; Guenther, D. B.; Moffat, A. F. J.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.

    2006-10-01

    The Microvariability and Oscillations of Stars (MOST) satellite observed the B supergiant HD 163899 (B2 Ib/II) for 37 days as a guide star and detected 48 frequencies <~2.8 cycles day-1 with amplitudes of a few millimagnitudes (mmag) and less. The frequency range embraces g- and p-mode pulsations. It was generally thought that no g-modes are excited in less luminous B supergiants because strong radiative damping is expected in the core. Our theoretical models, however, show that such g-modes are excited in massive post-main-sequence stars, in accordance with these observations. The nonradial pulsations excited in models between 20 Msolar at logTeff~4.41 and 15 Msolar at logTeff~4.36 are roughly consistent with the observed frequency range. Excitation by the Fe bump in opacity is possible because g-modes can be partially reflected at a convective zone associated with the hydrogen-burning shell, which significantly reduces radiative damping in the core. The MOST light curve of HD 163899 shows that such a reflection of g-modes actually occurs and reveals the existence of a previously unrecognized type of variable, slowly pulsating B supergiants (SPBsg) distinct from ? Cyg variables. Such g-modes have great potential for asteroseismology. Based on data from the MOST satellite, a Canadian Space Agency mission, operated jointly by Dynacon, Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with the assistance of the University of Vienna.

  16. On the optical--infra-red continuum emission from equatorial discs of supergiant B[e] stars

    E-print Network

    John M. Porter

    2002-11-20

    Two models of the circumstellar disc around supergiant B[e] stars are discussed: an equatorial wind model produced by wind bi-stability, and a Keplerian viscous disc model. Both models are successful in providing a site for dust formation once they have cooled sufficiently. However, the optical--infra-red continuum is calculated and it is found that both models have significant trouble in accounting for observations. In particular the optical--near-IR emission is accounted for, but the dust emission is underestimated by at least an order of magnitude. Variations in the structure of the models (the temperature variation with radius, the density structure and the dust opacity) are investigated to assess how (in)appropriate the standard models are for supergiant B[e] star discs. Changing the temperature structure, and making simple dust opacity changes within the disc has little effect on the resultant continuum emission. By altering the density structure of the discs, the continuum may be accounted for by both models: the equatorial wind model requires a very flat density profile which is impossible to explain with any accelerating wind, and the viscous disc model's density structure is required to fall off less steeply with radius than would have been expected, although this may be explained from consideration of viscous processes in the disc. It is recognised that both theoretical interpretations have difficulties and unsolved problems.

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

    SciTech Connect

    Ohyama, Youichi; Hota, Ananda [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China)

    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.

  18. 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.

  19. 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

  20. Spatially resolving the atmospheric dynamics over the surface of red supergiants with the Very Large Telescope Interferometer

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.

    2013-05-01

    The mass-loss mechanism in red supergiants is a long-stand-ing problem. The milliarcsecond angular resolution achieved by infrared long-baseline interferometry provides us with the only way to spatially resolve the region where the material is accelerated. For this goal, the 2.3 ?m CO lines are important, because they form in the upper photosphere and the outer atmosphere (so-called MOLsphere). We present high-spatial and high-spectral resolution observations of the 2.3 ?m CO lines in the red supergiants Betelgeuse and Antares using the Very Large Telescope Interferometer (VLTI). This has enabled us to spatially resolve the gas dynamics in the photosphere (and the MOLsphere) for the first time other than the Sun. We have detected vigorous motions of large CO gas clumps with velocities of up to 20-30 km s-1. Comparison of the CO line data taken 1 year apart shows a significant change in the dynamics of the atmosphere. In contrast to the CO line data, the continuum data reveal no or only marginal time variations. The observationally estimated gas density in the outer atmosphere at 1.3-1.4 R? is higher than the values predicted by the current 3-D convection simulations by 6 to 11 orders of magnitude. Therefore, at the moment, convection alone cannot explain the detected vigorous gas motions in the extended outer atmosphere of Betelgeuse and Antares.

  1. Pulsations in B-type supergiants with masses M<20 M_{?} before and after core helium ignition

    NASA Astrophysics Data System (ADS)

    Ostrowski, J.; Daszy?ska-Daszkiewicz, J.

    2015-03-01

    Evolutionary tracks and pulsational analysis of models with masses of 13-18 M? are presented. We address two important questions. The first one deals with one of the most unresolved problems in astrophysics, i.e. the existence of a blue loop after core helium ignition; the so-called to loop or not to loop problem. We show that inward overshooting from the outer convective zone in the red giant phase is prerequisite for the development of the blue loop. Our second question concerns pulsational instability of models in the core helium burning phase. We present for the first time that models on the blue loop can have unstable modes driven by the ? mechanism operating in the Z-bump. Contrary to post-main-sequence models in the shell hydrogen burning phases, pulsational instability of the blue loop models depends mainly on effective temperature and metallicity is of secondary importance. Finally, we try to interpret the oscillation spectrum of the blue supergiant HD 163899, the only member of the slowly pulsating B-type supergiant class and to get some clue on the evolutionary status of the star.

  2. Giant outburst from the supergiant fast X-ray transient IGR J17544-2619: accretion from a transient disc?

    NASA Astrophysics Data System (ADS)

    Romano, P.; Bozzo, E.; Mangano, V.; Esposito, P.; Israel, G.; Tiengo, A.; Campana, S.; Ducci, L.; Ferrigno, C.; Kennea, J. A.

    2015-04-01

    Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries associated with OB supergiant companions and characterized by an X-ray flaring behaviour whose dynamical range reaches 5 orders of magnitude on time scales of a few hundred to thousands of seconds. Current investigations concentrate on finding possible mechanisms to inhibit accretion in SFXTs and to explain their unusually low average X-ray luminosity. We present the Swift observations of an exceptionally bright outburst displayed by the SFXT IGR J17544-2619 on 2014 October 10 when the source achieved a peak luminosity of 3 × 1038 erg s-1. This extends the total source dynamic range to ?106, the largest (by a factor of 10) recorded so far from an SFXT. Tentative evidence for pulsations at a period of 11.6 s is also reported. We show that these observations challenge, for the first time, the maximum theoretical luminosity achievable by an SFXT and propose that this giant outburst was due to the formation of a transient accretion disc around the compact object. Tables 1 and 2, and Fig. 2 are available in electronic form at http://www.aanda.org

  3. Discovery of a possibly single blue supergiant star in the intra-cluster region of Virgo cluster of galaxies

    E-print Network

    Ohyama, Youichi; 10.1088/2041-8205/767/2/L29

    2013-01-01

    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 HII region. We argue that turbulence within the ram pressure striped gaseous trail may play a dominant role for the sta...

  4. Unveiling Type IIb Supernova Progenitors: SN 2011hs from a Supergiant Star

    NASA Astrophysics Data System (ADS)

    Bufano, F.

    2014-10-01

    Type IIb Supernovae are the final evolutionary stage of massive stars that were able to retain only a thin (lesssim 1 M_{odot}) H/He external envelope at the time of the explosion. The mechanism of mass-loss that made such final structure possible and the nature of such progenitor stars are still open issues. We present the results obtained from the study of a sample of Type IIb SNe, in particular, of SN 2011hs (Bufano et al., 2013, MNRAS submitted). SN 2011hs was a relatively faint (M_{B} = -15.6 mag) and red Type IIb SN, characterized by a narrow light curve shape. Its spectral evolution showed the metamorphosis typical of this class of SN, from spectra dominated by H I lines to spectra where He I features dominate, but with broad absorption line profiles indicating high expansion velocities. Modeling the light curve of SN 2011hs and its velocity evolution with hydrodynamical calculations, we estimated that the SN is consistent with the explosion of a 3-4 M_{odot} He-core star, from a main sequence mass of 12-15 M_{odot}, ejecting a ^{56}Ni mass equal to 0.04 M_{odot} and characterized by an explosion energy of E? 8.5× 10^{50} erg s^{-1}. Based on the light curve evolution, we assumed that the explosion occurred 6 days before the discovery (2,455,872 ± 4 JD), resulting in an adiabatic cooling phase lasting 8 days, similarly to SN 1993J. Since the duration and the decreasing rate of the cooling branch depends mainly on the progenitor size, we could infer from it a progenitor radius of ? 500-600 R_{odot}, like a supergiant star. Our modeling rules out models with He core mass >5 M_{odot}, i.e. main sequence masses above 20 M_{odot}. Such a lower limit for the progenitor mass could indicate the possibility of a binary origin, although the radio light curve does not show strong deviations, typically signature of the presence of a companion star.

  5. The weak magnetic field of the O9.7 supergiant ?OrionisA

    NASA Astrophysics Data System (ADS)

    Bouret, J.-C.; Donati, J.-F.; Martins, F.; Escolano, C.; Marcolino, W.; Lanz, T.; Howarth, I. D.

    2008-09-01

    We report here the detection of a weak magnetic field of 50-100G on the O9.7 supergiant ?OrionisA (?OriA), using spectropolarimetric observations obtained with NARVAL at the 2-m Télescope Bernard Lyot atop Pic du Midi (France). ?OriA is the third O star known to host a magnetic field (along with ?1OriC and HD191612), and the first detection on a `normal' rapidly rotating O star. The magnetic field of ?OriA is the weakest magnetic field ever detected on a massive star. The measured field is lower than the thermal equipartition limit (about 100G). By fitting non-local thermodynamic equilibrium (NLTE) model atmospheres to our spectra, we determined that ?OriA is a 40Msolar star with a radius of 25Rsolar and an age of about 5-6Myr, showing no surface nitrogen enhancement and losing mass at a rate of about 2 × 10-6Msolaryr-1. The magnetic topology of ?OriA is apparently more complex than a dipole and involves two main magnetic polarities located on both sides of the same hemisphere; our data also suggest that ?OriA rotates in about 7.0d and is about 40° away from pole-on to an Earth-based observer. Despite its weakness, the detected magnetic field significantly affects the wind structure; the corresponding Alfvén radius is however very close to the surface, thus generating a different rotational modulation in wind lines than that reported on the two other known magnetic O stars. The rapid rotation of ?OriA with respect to ?1OriC appears as a surprise, both stars having similar unsigned magnetic fluxes (once rescaled to the same radius); it may suggest that the subequipartition field detected on ?OriA is not a fossil remnant (as opposed to that of ?1 OriC and HD191612), but the result of an exotic dynamo action produced through magnetohydrodynamics (MHD) instabilities. Based on observations obtained at the Télescope Bernard Lyot (TBL), operated by the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France. E-mail: jean-claude.bouret@oamp.fr

  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 absence of a substantial shift in the wind ionization mixture of gamma Ara, and the normal nature of its photospheric spectrum, suggests wind-compression as the likely dominant cause for the observed equatorial density enhancements.

  7. 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 ?m 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 percent of the dust production (which is dominated by low-mass AGBs), but we note that in low-metallicity starbursts, dust production by RSGs would likely dominate over other sources.

  8. Ionization structure in the winds of B[e] supergiants II. Influence of rotation on the formation of equatorial hydrogen neutral zones

    E-print Network

    Michaela Kraus

    2006-06-06

    Context: B[e] supergiants are known to have non-spherical winds, and the existence of disks that are neutral in hydrogen close to their stellar surface has been postulated. A suitable mechanism to produce non-spherical winds seems to be rapid rotation, and at least for three B[e] supergiants in the Magellanic Clouds rotation velocities at a substantial fraction of their critical velocity have been found. Aims: We want to find suitable recombination distances in the equatorial plane of rapidly rotating stars that explain the observed huge amounts of neutral material in the vicinity of B[e] supergiants. Methods: We perform ionization structure calculations in the equatorial plane around rapidly rotating luminous supergiants. The restriction to the equatorial plane allows us to treat the ionization balance equations 1-dimensionally, while the stellar radiation field is calculated 2-dimensionally, taking into account the latitudinal variation of the stellar surface parameters. The stellar parameters used correspond to those known for B[e] supergiants. The assumptions made in the computations all have in common that the total number of available ionizing photons at any location within the equatorial plane is overestimated, resulting in upper limits for the recombination distances. Results: We find that despite the drop in equatorial surface density of rapidly rotating stars (neglecting effects like bi-stability and/or wind compression), hydrogen and helium recombine at or close to the stellar surface, for mass loss rates Mdot > 5d-5 M_sun/yr and rotation speeds in excess of v(rot,eq)/v(crit)=0.8.

  9. CHARA/MIRC observations of two M supergiants in Perseus OB1: temperature, Bayesian modeling, and compressed sensing imaging

    E-print Network

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

    2014-01-01

    Two red supergiants of the Per OB1 association, RS Per and T Per, have been observed in H band using the MIRC instrument at the CHARA array. The data show clear evidence of 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 discs 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 red su- pergiants. 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 th...

  10. 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.

  11. 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.

  12. 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. (Haystack Observatory, Westford, MA (USA))

    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.

  13. BROADBAND ESO/VISIR-SPITZER INFRARED SPECTROSCOPY OF THE OBSCURED SUPERGIANT X-RAY BINARY IGR J16318-4848

    SciTech Connect

    Chaty, S.; Rahoui, F., E-mail: sylvain.chaty@cea.fr, E-mail: frahoui@cfa.harvard.edu [AIM (UMR-E 9005 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d'Astrophysique, Centre de Saclay, FR-91191 Gif-sur-Yvette Cedex (France)

    2012-06-01

    A new class of X-ray binaries has recently been discovered by the high-energy observatory INTEGRAL. It is composed of intrinsically obscured supergiant high-mass X-ray binaries, unveiled by means of multi-wavelength X-ray, optical, near- and mid-infrared observations, in particular, photometric and spectroscopic observations using ESO facilities. However, the fundamental questions about these intriguing sources, namely, their formation, evolution, and the nature of their environment, are still unsolved. Among them, IGR J16318-4848, a compact object orbiting around a supergiant B[e] star, seems to be one of the most extraordinary celestial sources of our Galaxy. We present here new ESO/Very Large Telescope (VLT) VISIR mid-infrared (MIR) spectroscopic observations of this source. First, line diagnostics allow us to confirm the presence of absorbing material (dust and cold gas) enshrouding the whole binary system, and to characterize the nature of this material. Second, by fitting broadband near- to mid-infrared spectral energy distribution, including ESO NTT/SofI, VLT/VISIR, and Spitzer data, with a phenomenological model for sgB[e] stars, we show that the star is surrounded by an irradiated rim heated to a temperature of {approx}3800-5500 K, along with a viscous disk component at an inner temperature of {approx}750 K. VISIR data allow us to exclude the spherical geometry for the dust component. This detailed study will allow us in the future to get better constraints on the formation and evolution of such rare and short-living high-mass X-ray binary systems in our Galaxy.

  14. DISTANCE AND PROPER MOTION MEASUREMENT OF THE RED SUPERGIANT, S PERSEI, WITH VLBI H{sub 2}O MASER ASTROMETRY

    SciTech Connect

    Asaki, Y. [Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuou, Sagamihara, Kanagawa 252-5210 (Japan); Deguchi, S. [Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku 384-1305 (Japan); Imai, H. [Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Hachisuka, K. [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Miyoshi, M. [Division of Radio Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Honma, M., E-mail: asaki@vsop.isas.jaxa.j, E-mail: deguchi@nro.nao.ac.j, E-mail: hiroimai@sci.kagoshima-u.ac.j, E-mail: khachi@shao.ac.c, E-mail: makoto.miyoshi@nao.ac.j, E-mail: mareki.honma@nao.ac.j [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2010-09-20

    We have conducted Very Long Baseline Array phase-referencing monitoring of H{sub 2}O masers around the red supergiant, S Persei, for six years. We have fitted maser motions to a simple expanding-shell model with a common annual parallax and stellar proper motion, and obtained the annual parallax as 0.413 {+-} 0.017 mas and the stellar proper motion as (-0.49 {+-} 0.23 mas yr{sup -1}, -1.19 {+-} 0.20 mas yr{sup -1}) in right ascension and declination, respectively. The obtained annual parallax corresponds to the trigonometric distance of 2.42{sup +0.11}{sub -0.09} kpc. Assuming a Galactocentric distance of the Sun of 8.5 kpc, the circular rotational velocity of the local standard of rest at a distance of the Sun of 220 km s{sup -1}, and a flat Galactic rotation curve, S Persei is suggested to have a non-circular motion deviating from the Galactic circular rotation for 15 km s{sup -1}, which is mainly dominated by the anti-rotation direction component of 12.9 {+-} 2.9 km s{sup -1}. This red supergiant is thought to belong to the OB association, Per OB1, so that this non-circular motion is representative of a motion of the OB association in the Milky Way. This non-circular motion is somewhat larger than that explained by the standard density-wave theory for a spiral galaxy and is attributed to either a cluster shuffling of the OB association, or to non-linear interactions between non-stationary spiral arms and multi-phase interstellar media. The latter comes from a new view of a spiral arm formation in the Milky Way suggested by recent large N-body/smoothed particle hydrodynamics numerical simulations.

  15. On the magnetic structure and wind parameter profiles of Alfven wave driven winds in late-type supergiant stars

    E-print Network

    D. Falceta-Goncalves; A. A. Vidotto; V. Jatenco-Pereira

    2006-02-14

    Cool stars at giant and supergiant evolutionary phases present low velocity and high density winds, responsible for the observed high mass-loss rates. Although presenting high luminosities, radiation pressure on dust particles is not sufficient to explain the wind acceleration process. Among the possible solutions to this still unsolved problem, Alfven waves are, probably, the most interesting for their high efficiency in transfering energy and momentum to the wind. Typically, models of Alfven wave driven winds result in high velocity winds if they are not highly damped. In this work we determine self-consistently the magnetic field geometry and solve the momentum, energy and mass conservation equations, to demonstrate that even a low damped Alfven wave flux is able to reproduce the low velocity wind. We show that the magnetic fluxtubes expand with a super-radial factor S>30 near the stellar surface, larger than that used in previous semi-empirical models. The rapid expansion results in a strong spatial dilution of the wave flux. We obtained the wind parameter profiles for a typical supergiant star of 16 M_sun. The wind is accelerated in a narrow region, coincident with the region of high divergence of the magnetic field lines, up to 100 km/s. For the temperature, we obtained a slight decrease near the surface for low damped waves, because the wave heating mechanism is less effective than the radiative losses. The peak temperature occurs at 1.5 r_0 reaching 6000 K. Propagating outwards, the wind cools down mainly due to adiabatic expansion.

  16. QUANTITATIVE SPECTROSCOPY OF BLUE SUPERGIANT STARS IN THE DISK OF M81: METALLICITY, METALLICITY GRADIENT, AND DISTANCE

    SciTech Connect

    Kudritzki, Rolf-Peter; Urbaneja, Miguel A.; Gazak, Zachary; Bresolin, Fabio [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Przybilla, Norbert [Dr. Remeis-Sternwarte Bamberg and ECAP, D-96049 Bamberg (Germany); Gieren, Wolfgang; Pietrzynski, Grzegorz, E-mail: kud@ifa.hawaii.edu, E-mail: urbaneja@ifa.hawaii.edu, E-mail: zgazak@ifa.hawaii.edu, E-mail: bresolin@ifa.hawaii.edu, E-mail: przybilla@sternwarte.uni-erlangen.de, E-mail: wgieren@astro-udec.cl, E-mail: pietrzyn@astrouw.edu.pl [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

    2012-03-01

    The quantitative spectral analysis of low-resolution ({approx}5 A) Keck LRIS spectra of blue supergiants in the disk of the giant spiral galaxy M81 is used to determine stellar effective temperatures, gravities, metallicities, luminosities, interstellar reddening, and a new distance using the flux-weighted gravity-luminosity relationship. Substantial reddening and extinction are found with E(B - V) ranging between 0.13 and 0.38 mag and an average value of 0.26 mag. The distance modulus obtained after individual reddening corrections is 27.7 {+-} 0.1 mag. The result is discussed with regard to recently measured tip of the red giant branch and Cepheid distances. The metallicities (based on elements such as iron, titanium, magnesium) are supersolar ( Almost-Equal-To 0.2 dex) in the inner disk (R {approx}< 5 kpc) and slightly subsolar ( Almost-Equal-To - 0.05 dex) in the outer disk (R {approx}> 10 kpc) with a shallow metallicity gradient of 0.034 dex kpc{sup -1}. The comparison with published oxygen abundances of planetary nebulae and metallicities determined through fits of Hubble Space Telescope color-magnitude diagrams indicates a late metal enrichment and a flattening of the abundance gradient over the last 5 Gyr. This might be the result of gas infall from metal-rich satellite galaxies. Combining these M81 metallicities with published blue supergiant abundance studies in the Local Group and the Sculptor Group, a galaxy mass-metallicity relationship based solely on stellar spectroscopic studies is presented and compared with recent studies of Sloan Digital Sky Survey star-forming galaxies.

  17. A Suzaku X-ray observation of one orbit of the supergiant fast X-ray transient IGR J16479-4514

    E-print Network

    Sidoli, L; Sguera, V; Bodaghee, A; Tomsick, J A; Pottschmidt, K; Rodriguez, J; Romano, P; Wilms, J

    2012-01-01

    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. About 80% of the short orbital period (Porb=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 lasting the first 46 ks (1E-13 erg/cm2/s, 1-10 keV), 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 (6-7)x10^-12 erg/cm2/s punctuated by two structured faint flares with a duration of about 10 and 15 ks. 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 obj...

  18. Imaging the outward motions of clumpy dust clouds around the red supergiant Antares with VLT/VISIR

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.

    2014-08-01

    Aims: We present a 0."5-resolution 17.7 ?m image of the red supergiant Antares. Our aim is to study the structure of the circumstellar envelope in detail. Methods: Antares was observed at 17.7 ?m with the VLT mid-infrared instrument VISIR. Taking advantage of the BURST mode, in which a large number of short exposure frames are taken, we obtained a diffraction-limited image with a spatial resolution of 0."5. Results: The VISIR image shows six clumpy dust clouds located at 0."8-1."8 (43-96 R? = 136-306 AU) away from the star. We also detected compact emission within a radius of 0."5 around the star. Comparison of our VISIR image taken in 2010 and the 20.8 ?m image taken in 1998 with the Keck Telescope reveals the outward motions of four dust clumps. The proper motions of these dust clumps (with respect to the central star) amount to 0."2-0."6 in 12 years. This translates into expansion velocities (projected onto the plane of the sky) of 13-40 km s-1 with an uncertainty of ± 7 km s-1. The inner compact emission seen in the 2010 VISIR image is presumably newly formed dust, because it is not detected in the image taken in 1998. If we assume that the dust is ejected in 1998, the expansion velocity is estimated to be 34 km s-1, in agreement with the velocity of the outward motions of the clumpy dust clouds. The mass of the dust clouds is estimated to be (3-6) × 10-9 M?. These values are lower by a factor of 3-7 than the amount of dust ejected in one year estimated from the (gas+dust) mass-loss rate of 2 × 10-6 M? yr-1, suggesting that the continuous mass loss is superimposed on the clumpy dust cloud ejection. Conclusions: The clumpy dust envelope detected in the 17.7 ?m diffraction-limited image is similar to the clumpy or asymmetric circumstellar environment of other red supergiants. The velocities of the dust clumps cannot be explained by a simple accelerating outflow, implying the possible random nature of the dust cloud ejection mechanism. Based on VISIR observations made with the Very Large Telescope of the European Southern Observatory. Program ID: 385.D-0120(A), 286.D-5007(A).

  19. Chemical Peels

    MedlinePLUS

    ... How to Choose the Best Skin Care Products Chemical Peels Uses for Chemical Peels Learn more about specific conditions where chemical ... damaged skin Sagging skin Wrinkles What is a chemical peel? A chemical peel is a technique used ...

  20. The supergiant shell with triggered star formation in the dwarf irregular galaxy IC 2574: neutral and ionized gas kinematics

    NASA Astrophysics Data System (ADS)

    Egorov, O. V.; Lozinskaya, T. A.; Moiseev, A. V.; Smirnov-Pinchukov, G. V.

    2014-10-01

    We analyse the ionized gas kinematics in the star formation regions of the supergiant shell (SGS) of the IC 2574 galaxy using observations made with the Fabry-Perot interferometer at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences; the data of the H I Nearby Galaxy Survey (THINGS) are used to analyse the neutral gas kinematics in the area. We perform the `derotation' of the H? and H I data cubes and show its efficiency in the kinematics analysis. We confirm the SGS expansion velocity of 25 km s-1 obtained previously and conclude that the SGS is located at the far side of the galactic disc plane. We determine the expansion velocities, kinematic ages and the required mechanical energy input rates for four star formation complexes in the walls of the SGS; for those remaining, we give the limiting values of the above parameters. A comparison with the age and energy input of the stellar population of the complexes shows that sufficient energy is fed to all H II regions except one. We discuss in detail the possible nature of this region and that of another region, which was believed to be a supernova remnant, according to radio observations. We have measured the expansion velocity of the latter and we can confirm its identification as an old supernova remnant. Our observations have allowed us to identify a faint diffuse H? emission inside the SGS, which was not been previously observed.

  1. High-latitude supergiant V5112 Sgr: Enrichment of the envelope with heavy s-process metals

    NASA Astrophysics Data System (ADS)

    Klochkova, V. G.

    2013-11-01

    High-resolution ( R = 60 000) echelle spectroscopy of the post-AGB supergiant V5112 Sgr performed in 1996-2012 with the 6-m BTA telescope has revealed peculiarities of the star's optical spectrum and has allowed the variability of the velocity field in the stellar atmosphere and envelope to be studied in detail. An asymmetry and splitting of strong absorption lines with a low lower-level excitation potential have been detected for the first time. The effect is maximal in Ba II lines whose profile is split into three components. The profile shape and positions of the split lines change with time. The short-wavelength components of the split absorption lines are shown to be formed in a structured circumstellar envelope, suggesting an efficient dredge-up of the heavy metals produced during the preceding evolution of this star into the envelope. The envelope expansion velocities have been estimated to be V exp ? 20 and 30 km s-1. The mean radial velocity from diffuse bands in the spectrum of V5112 Sgr coincides with that from the short-wavelength shell component of the Na I D lines, which leads to the conclusion about their formation in the circumstellar envelope. Analysis of the set of radial velocities V r based on symmetric absorption lines has confirmed the presence of pulsations in the stellar atmosphere with an amplitude ? V r ? 8 km s-1.

  2. 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 [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Deguchi, Shuji, E-mail: junichi@hku.hk [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)

    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.

  3. 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 [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, D-85741 Garching (Germany); Plez, Bertrand [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS, F-34095 Montpellier (France); Davies, Ben [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Gazak, Zach, E-mail: mbergema@mpa-garching.mpg.de, E-mail: klind@mpa-garching.mpg.de, E-mail: kud@ifa.hawaii.edu, E-mail: zgazak@ifa.hawaii.edu, E-mail: bertrand.plez@univ-montp2.fr, E-mail: bdavies@ast.cam.ac.uk [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    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.

  4. The atmospheric structure and fundamental parameters of the red supergiants AH Sco, UY Sct, and KW Sgr

    NASA Astrophysics Data System (ADS)

    Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H.

    2013-05-01

    We present the atmospheric structure and the fundamental parameters of the Red Supergiants (RSGs) AH Sco, UY Sct, and KW Sgr. We have carried out spectro-interferometric observations in the near-infrared bands (between 1.9 ?m and 2.5 ?m) with the VLTI/AMBER instrument in medium resolution. In the visibility data, we detect the presence of molecular layers of water and CO in extended atmospheres. For a uniform disk modelling, we observe size increases in the water band centered at 1.9 ?m and in the CO band at 2.3--2.5 ?m, with respect to the near-continuun bandpass (2.20-2.25 ?m). Our near-infrared spectra of AH Sco, UY Sct, and KW Sgr are well reproduced by the PHOENIX model. However the synthetic visibility amplitudes of the model do not predict the large extensions of the molecular bands. The continuum (2.15-2.25 ?m) appears free from contamination by molecular layers. Thus, the continuum fitting to the PHOENIX can be used to estimate the diameter. We estimate the Rosseland-mean photospheric angular diameter of AH Sco, UY Sct, and KW Sgr to be 6.12±0.7 mas, 5.67± 0.55 mas, and 4.07±0.65 mas, respectively (preliminary values). We estimate radii and effective temperatures, and place the stars in the HR diagram.

  5. 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.

  6. On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

    E-print Network

    Jones, O C; Sargent, B A; McDonald, I; Gielen, C; Woods, Paul M; Sloan, G C; Boyer, M L; Zijlstra, A A; Clayton, G C; Kraemer, K E; Srinivasan, S; Ruffle, P M E

    2012-01-01

    We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust ma...

  7. 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 the size of a tennis ball on the International Space Station (ISS), as seen from the ground. "Thanks to these outstanding images, we have detected a large plume of gas extending into space from the surface of Betelgeuse," says Pierre Kervella from the Paris Observatory, who led the team. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. "This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions," adds Kervella. Two mechanisms could explain this asymmetry. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection - similar to the circulation of water heated in a pot. To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry. With the AMBER instrument on ESO's Very Large Telescope Interferometer, which combines the light from three 1.8-metre Auxiliary Telescopes of the VLT, the astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such superb resolution, the astronomers were able to detect indirectly details four times finer still than the amazing NACO images had already allowed (in other words, the size of a marble on the ISS, as seen from the ground). "Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, we detected how the gas is moving in different areas of Betelgeuse's surface ? the first time this has been done for a star other than the Sun", says Ohnaka. The AMBER observations revealed that the gas in Betelgeuse's atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. Their unrivalled observations have led

  8. Chemical Changes

    NSDL National Science Digital Library

    Mr. Jolley

    2005-10-25

    In this activity you will learn what a chemical change is. The first step to understanding chemical changes is to recognize the difference between chemical properties and physical properties. Click here for an example: Chemical and Physical Changes What are the signs of a chemical reaction occuring? Signs of Chemical Change What variables affect a chemical reaction? Variables ...

  9. Chemical Mechanical Planarization- Chemical

    NSDL National Science Digital Library

    This website includes an animation which illustrates the chemical action of slurry in the chemical-mechanical planarization process. Objective: Explain the mechanical and chemical steps in the CMP process. This simulation is from Module 068 of the Process & Equipment III Cluster of the MATEC Module Library (MML). Find this animation under the section "Process & Equipment III." To view other clusters or for more information about the MML visit http://matec.org/ps/library3/process_I.shtmlKey Phrase: MATEC Animation

  10. Chemical Threats

    MedlinePLUS

    ... indicate a chemical agent release. Before Before a Chemical Threat What you should do to prepare for ... and on the highest level. During During a Chemical Threat What you should do in a chemical ...

  11. 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 ...

  12. The VLT-FLAMES Tarantula Survey. XIX. B-type supergiants: Atmospheric parameters and nitrogen abundances to investigate the role of binarity and the width of the main sequence

    NASA Astrophysics Data System (ADS)

    McEvoy, C. M.; Dufton, P. L.; Evans, C. J.; Kalari, V. M.; Markova, N.; Simón-Díaz, S.; Vink, J. S.; Walborn, N. R.; Crowther, P. A.; de Koter, A.; de Mink, S. E.; Dunstall, P. R.; Hénault-Brunet, V.; Herrero, A.; Langer, N.; Lennon, D. J.; Maíz Apellániz, J.; Najarro, F.; Puls, J.; Sana, H.; Schneider, F. R. N.; Taylor, W. D.

    2015-03-01

    Context. Model atmosphere analyses have been previously undertaken for both Galactic and extragalactic B-type supergiants. By contrast, little attention has been given to a comparison of the properties of single supergiants and those that are members of multiple systems. Aims: Atmospheric parameters and nitrogen abundances have been estimated for all the B-type supergiants identified in the VLT-FLAMES Tarantula survey. These include both single targets and binary candidates. The results have been analysed to investigate the role of binarity in the evolutionary history of supergiants. Methods: tlusty non-local thermodynamic equilibrium (LTE) model atmosphere calculations have been used to determine atmospheric parameters and nitrogen abundances for 34 single and 18 binary supergiants. Effective temperatures were deduced using the silicon balance technique, complemented by the helium ionisation in the hotter spectra. Surface gravities were estimated using Balmer line profiles and microturbulent velocities deduced using the silicon spectrum. Nitrogen abundances or upper limits were estimated from the N ii spectrum. The effects of a flux contribution from an unseen secondary were considered for the binary sample. Results: We present the first systematic study of the incidence of binarity for a sample of B-type supergiants across the theoretical terminal age main sequence (TAMS). To account for the distribution of effective temperatures of the B-type supergiants it may be necessary to extend the TAMS to lower temperatures. This is also consistent with the derived distribution of mass discrepancies, projected rotational velocities and nitrogen abundances, provided that stars cooler than this temperature are post-red supergiant objects. For all the supergiants in the Tarantula and in a previous FLAMES survey, the majority have small projected rotational velocities. The distribution peaks at about 50 km s-1 with 65% in the range 30 km s-1 ? vesini ? 60 km s-1. About ten per cent have larger vesini (?100 km s-1), but surprisingly these show little or no nitrogen enhancement. All the cooler supergiants have low projected rotational velocities of ?70 km s-1and high nitrogen abundance estimates, implying that either bi-stability braking or evolution on a blue loop may be important. Additionally, there is a lack of cooler binaries, possibly reflecting the small sample sizes. Single-star evolutionary models, which include rotation, can account for all of the nitrogen enhancement in both the single and binary samples. The detailed distribution of nitrogen abundances in the single and binary samples may be different, possibly reflecting differences in their evolutionary history. Conclusions: The first comparative study of single and binary B-type supergiants has revealed that the main sequence may be significantly wider than previously assumed, extending to Teff = 20 000 K. Some marginal differences in single and binary atmospheric parameters and abundances have been identified, possibly implying non-standard evolution for some of the sample. This sample as a whole has implications for several aspects of our understanding of the evolutionary status of blue supergiants. Tables 1, 4, 7 are available in electronic form at http://www.aanda.org

  13. Spectral and temporal properties of the supergiant fast X-ray transient IGR J18483-0311 observed by INTEGRAL

    NASA Astrophysics Data System (ADS)

    Ducci, L.; Doroshenko, V.; Sasaki, M.; Santangelo, A.; Esposito, P.; Romano, P.; Vercellone, S.

    2013-11-01

    Context. IGR J18483-0311 is a supergiant fast X-ray transient whose compact object is located in a wide (18.5 d) and eccentric (e ~ 0.4) orbit, which shows sporadic outbursts that reach X-ray luminosities of ~1036 erg s-1. Aims: We investigated the timing properties of IGR J18483-0311 and studied the spectra during bright outbursts by fitting physical models based on thermal and bulk Comptonization processes for accreting compact objects. Methods: We analysed archival INTEGRAL data collected in the period 2003-2010, focusing on the observations with IGR J18483-0311 in outburst. We searched for pulsations in the INTEGRAL light curves of each outburst. We took advantage of the broadband observing capability of INTEGRAL for the spectral analysis. Results: We observed 15 outbursts, seven of which we report here for the first time. This data analysis almost doubles the statistics of flares of this binary system detected by INTEGRAL. A refined timing analysis did not reveal a significant periodicity in the INTEGRAL observation where a ~21 s pulsation was previously detected. Neither did we find evidence for pulsations in the X-ray light curve of an archival XMM-Newton observation of IGR J18483-0311. In the light of these results the nature of the compact object in IGR J18483-0311 is unclear. The broadband X-ray spectrum of IGR J18483-0311 in outburst is well fitted by a thermal and bulk Comptonization model of blackbody seed photons by the infalling material in the accretion column of a neutron star. We also obtained a new measurement of the orbital period using the Swift/BAT light curve.

  14. 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.

  15. On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

    NASA Astrophysics Data System (ADS)

    Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, Paul M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.

    2012-12-01

    We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 ?m. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ˜10-9 M? yr-1. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-?m feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-?m band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.

  16. Supergiant Fast X-ray Transients in outburst: new Swift observations of XTEJ1739-302, IGRJ17544-2619, and IGRJ08408-4503

    Microsoft Academic Search

    L. Sidoli; P. Romano; L. Ducci; A. Paizis; G. Cusumano; V. Mangano; H. A. Krimm; S. Vercellone; D. N. Burrows; J. A. Kennea; N. Gehrels

    2009-01-01

    We report on new X-ray outbursts observed with Swift from three Supergiant\\u000aFast X-ray Transients (SFXTs): XTEJ1739-302, IGRJ17544-2619 and IGRJ08408-4503.\\u000aThe former two outbursts were caught during the monitoring campaign we have\\u000abeen performing with the Swift satellite since October 2007: XTEJ1739-302\\u000aunderwent a new outburst on 2008, August 13, IGRJ17544-2619 on 2008, September\\u000a4, while IGRJ08408-4503 on 2008, September

  17. 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/km which, assuming terminal velocities in a large range 500-3000 km/s, implies an accretion luminosity two orders of magnitude higher than that observed. As a consequence, a mechanism should be at work reducing the mass accretion rate. Different possibilities are discussed.

  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. [Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, 1156 High St., Santa Cruz, CA (United States); Negueruela, Ignacio, E-mail: rrampy@ucsc.ed [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99 E03080, Alicante (Spain)

    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. IGR J17544-2619 in Depth With Suzaku: Direct Evidence for Clumpy Winds in a Supergiant Fast X-ray Transient

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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 104 in luminosity and gives a detailed look at SFXT behavior.

  20. IR Mergers and IR QSOs with Galactic Winds. II. NGC 5514, two Extra-nuclear Starburts/LINERs with a Supergiant Bubble in the Rupture Phase

    E-print Network

    S. Lipari; E. Mediavilla; B. Garcia-Lorenzo; R. Diaz; J. Acosta-Pulido; M. Aguero; Y. Taniguchi; H. Dottori; R. Terlevich

    2004-09-05

    A study of morphology, kinematics and ionization structure of the IR merger NGC 5514, is presented. This study is based mainly on Integral 2D spectroscopy obtained on 4.2 m William Herschel Telescope (La Palma, Spain) and data from CASLEO (Argentina). Clear evidence of two extra-nuclear starbursts with young outflows and LINER activity are reported. One of these outflow generate a supergiant bubble, where the emission lines and kinematics maps show 4 extended ejections. These results suggest that the bubble is in the rupture phase.

  1. Supermassive Star Clusters in Supergiant Galaxies: Tracing the Enrichment of the Earliest Stellar Systems

    NASA Astrophysics Data System (ADS)

    Harris, William

    2010-09-01

    The cD-type Brightest Cluster Galaxies contain the richest globular cluster systems {GCSs} that exist. The wealth of results gathered from previous HST imaging programs in many smaller galaxies show that GCSs are powerful and unique tracers that link to origin and evolution of structure in two directions simultaneously: one direction is inward to the structure of the protoglobular clouds, star formation in the densest known conditions, and their chemical enrichment history. The other direction is outward to constraining early galaxy formation history, the nature of the pregalactic dwarfs, or the spatial and dynamic structure of the halo. But we have not yet tapped the vast mine of GCS data waiting for exploitation in the most luminous galaxies of all, the cDs. Surprisingly, we know little about these systems beyond the globular cluster populations in the nearby cDs M87 {Virgo} and NGC 1399 {Fornax}, and these two cases no longer provide adequate tests of the new phenomena now being uncovered, such as the correlation between GC mass and metallicity, the strikingly different formation efficiencies of metal-poor and metal-rich clusters, the galaxy-to-galaxy differences in GC mass distribution, and connections to Ultra-Compact Dwarfs and dE nuclei.We propose to image 7 cD-type systems within 200 Mpc that are representative of the very biggest galaxies known {Mv < -23}. These lie in far richer Abell-cluster environments than we could ever probe in Virgo, Fornax, or nearer systems. We will use ACS/WFC and WFC3 to image their GCSs down to the turnover point of the GC luminosity function, using the B and I filters for an optimal combination of exposure time, field size, and metallicity sensitivity. Our complete survey will produce luminosities, metallicities, and spatial distribution functions for more than 35,000 GCs, the largest GC database in existence and an order of magnitude larger than even the recent Virgo Cluster Survey. The legacy value of our survey will supply a rich resource for a wide array of other GC science and the formation histories of these unique systems.

  2. Chemical milling

    Microsoft Academic Search

    J. W. Dini

    1974-01-01

    Chemical milling was used in removing excess material and reducing overall weight of metal parts. Chemical milling is discussed generally, describing the process, its applications, advantages and limitations, chemical milling solutions, maskants, and various other aspects of the chemical milling process. The effectiveness of chemical milling of specific materials such as aluminum, beryllium, magnesium, titanium, steel, and stainless steel alloys

  3. A FIVE-YEAR SPECTROSCOPIC AND PHOTOMETRIC CAMPAIGN ON THE PROTOTYPICAL {alpha} CYGNI VARIABLE AND A-TYPE SUPERGIANT STAR DENEB

    SciTech Connect

    Richardson, N. D. [Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P.O. Box 4106, Atlanta, GA 30302-4106 (United States); Morrison, N. D.; Kryukova, E. E. [Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft, Toledo, OH 43606 (United States); Adelman, S. J., E-mail: richardson@chara.gsu.edu, E-mail: nmorris@utnet.utoledo.edu, E-mail: eallga@physics.utoledo.edu, E-mail: adelmans@citadel.edu [Department of Physics, The Citadel, 171 Moultrie Street, Charleston, SC 29409 (United States)

    2011-01-15

    Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stroemgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H{alpha} profile, H{alpha} equivalent widths, and radial velocities measured from Si II {lambda}{lambda} 6347, 6371. Time-series analysis reveals no obvious cyclic behavior that proceeds through multiple observing seasons, although we found a suspected 40 day period in two, non-consecutive observing seasons. Some correlations are found between photometric and radial velocity data sets and suggest radial pulsations at two epochs. No correlation is found between the variability of the H{alpha} profiles and that of the radial velocities or the photometry. Lucy found evidence that Deneb was a long-period single-lined spectroscopic binary star, but our data set shows no evidence for radial velocity variations caused by a binary companion.

  4. Neutral and ionised gas around the post-red supergiant IRC +10 420 at AU size scales

    NASA Astrophysics Data System (ADS)

    Oudmaijer, R. D.; de Wit, W. J.

    2013-03-01

    Context. IRC +10 420 is one of the few known massive stars in rapid transition from the red supergiant phase to the Wolf-Rayet or luminous blue variable phase. Aims: The star has an ionised wind and using the Br? line we assess the mass-loss on spatial scales of ~1 AU. Methods: We present new VLT Interferometer AMBER data which are combined with all other AMBER data present in the literature. The final dataset covers a position angle range of ~180° and baselines up to 110 m. The spectrally dispersed visibilities, differential phases and line flux are conjointly analysed and modelled. We also present the first AMBER/FINITO observations which cover a larger wavelength range and allow us to observe the Na i doublet at 2.2 ?m. The data are complemented by X-Shooter data, which provide a higher spectral resolution view. Results: The Br? emission line and the Na i doublet are both spatially resolved. After correcting the AMBER data for the fact that the lines are not spectrally resolved, we find that Br? traces a ring with a diameter of 4.18 mas, in agreement with higher spectral resolution data. We consider a geometric model in which the Br? emission emerges from the top and bottom rings of an hour-glass shaped structure, viewed almost pole-on. It provides satisfactory fits to most visibilities and differential phases. The fact that we detect line emission from a neutral metal like Na i within the ionised region, a very unusual occurrence, suggests the presence of a dense pseudo-photosphere. Conclusions: The ionised wind can be reproduced with a polar wind, which could well have the shape of an hour-glass. Closer in, the resolved Na i emission is found to occur on scales barely larger than the continuum. This fact and that many yellow hypergiants exhibit this comparatively rare emission hints at the presence of a "Yellow" or even "White Wall" in the Hertzsprung-Russell diagram, preventing them from visibly evolving to the blue. Based on observations at ESO, and in particular with VLTI, proposals 079.D-0123(A), and 383.C-0166(A) and X-Shooter, proposal SV-9434.FITS files are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/551/A69

  5. The atmospheric structure and fundamental parameters of the red supergiants AH Scorpii, UY Scuti, and KW Sagittarii

    NASA Astrophysics Data System (ADS)

    Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H.

    2013-06-01

    Aims: We present the atmospheric structure and the fundamental properties of the red supergiants (RSGs) AH Sco, UY Sct, and KW Sgr based on VLTI/AMBER observations. Methods: We carried out spectro-interferometric observations of AH Sco, UY Sct, and KW Sgr in the near-infrared K band (1.92-2.47 ?m) with the VLTI/AMBER instrument with spatial and spectral resolutions of 3 milliarcsec and 1500, respectively, and compared the data to a new grid of hydrostatic PHOENIX model atmospheres. Results: In our visibility data, we observe molecular layers of water and CO in extended atmospheres. For a uniform disk modeling, we observe size increases at the water band centered at 1.9 ?m of 10% to 25% and at the CO bandheads at 2.3-2.5 ?m of 20%-35% with respect to the near-continuum bandpass at around 2.20 ?m. Our near-infrared spectra of AH Sco, UY Sct, and KW Sgr are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models. However, the model visibilities do not predict the large observed extensions of the molecular layers. Comparing the continuum visibility values to PHOENIX models, we estimate the Rosseland-mean photospheric angular diameters of AH Sco, UY Sct, and KW Sgr to be 5.81 ± 0.15 mas, 5.48 ± 0.10 mas, and 3.91 ± 0.25 mas, respectively. Together with the distance and the spectro-photometry, we calculate radii of 1411 ± 124 R? for AH Sco, 1708 ± 192 R? for UY Sct, and 1009 ± 142 R? for KW Sgr and effective temperatures of 3682 ± 190 K for AH Sco, 3365 ± 134 K for UY Sct, and 3720 ± 183 K for KW Sgr. Conclusions: AH Sco, UY Sct, and KW Sgr exhibit extended atmospheric layers of H2O and CO. The PHOENIX atmosphere models predict the spectra and the continuum visibility values, but cannot reproduce the large extensions of the molecular layers. This indicates that the opacities of the molecular bands are included, but that the model atmospheres are too compact compared to the observations. The observed extended layers may be levitated by processes such as pulsation or convection, which are not included in the hydrostatic atmospheric models. The location of the targets in the HR-diagram is confirmed to be close to, and possibly slightly to the right of, the Hayashi limit of recent evolutionary tracks corresponding to masses between about 20 M? and 40 M?.

  6. 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 X-ray wind models is inconsistent with the predicted mass-loss rate. Thus, it is impossible to reconcile the observed ionization ratios and the predicted mass-loss rate within the framework of the available models.

  7. Chemical Equations

    NSDL National Science Digital Library

    Anthony Carpi

    2003-03-27

    It discusses the process of equation writing and balancing chemical equations in perspective of the chemical changes that take place during a reaction. This module is the third in a series on chemical reactions.

  8. Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other Supergiants

    NASA Astrophysics Data System (ADS)

    Humphreys, Roberta M.; Weis, Kerstin; Davidson, Kris; Bomans, D. J.; Burggraf, Birgitta

    2014-07-01

    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. 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 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.

  9. The circumstellar environment and evolutionary state of the supergiant B[e] star Wd1-9

    NASA Astrophysics Data System (ADS)

    Clark, J. S.; Ritchie, B. W.; Negueruela, I.

    2013-12-01

    Context. Historically, supergiant (sg)B[e] stars have been difficult to include in theoretical schemes for the evolution of massive OB stars. Aims: The location of Wd1-9 within the coeval starburst cluster Westerlund 1 means that it may be placed into a proper evolutionary context and we therefore aim to utilise a comprehensive multiwavelength dataset to determine its physical properties and consequently its relation to other sgB[e] stars and the global population of massive evolved stars within Wd1. Methods: Multi-epoch R- and I-band VLT/UVES and VLT/FORS2 spectra are used to constrain the properties of the circumstellar gas, while an ISO-SWS spectrum covering 2.45-45 ?m is used to investigate the distribution, geometry and composition of the dust via a semi-analytic irradiated disk model. Radio emission enables a long term mass-loss history to be determined, while X-ray observations reveal the physical nature of high energy processes within the system. Results: Wd1-9 exhibits the rich optical emission line spectrum that is characteristic of sgB[e] stars. Likewise its mid-IR spectrum resembles those of the LMC sgB[e] stars R66 and 126, revealing the presence of equatorially concentrated silicate dust, with a mass of ~10-4 M?. Extreme historical and ongoing mass loss (?10-4 M? yr-1) is inferred from the radio observations. The X-ray properties of Wd1-9 imply the presence of high temperature plasma within the system and are directly comparable to a number of confirmed short-period colliding wind binaries within Wd1. Conclusions: The most complete explanation for the observational properties of Wd1-9 is that it is a massive interacting binary currently undergoing, or recently exited from, rapid Roche-lobe overflow, supporting the hypothesis that binarity mediates the formation of (a subset of) sgB[e] stars. The mass loss rate of Wd1-9 is consistent with such an assertion, while viable progenitor and descendent systems are present within Wd1 and comparable sgB[e] binaries have been identified in the Galaxy. Moreover, the rarity of sgB[e] stars - only two examples are identified from a census of ~68 young massive Galactic clusters and associations containing ~600 post-Main Sequence stars - is explicable given the rapidity (~104 yr) expected for this phase of massive binary evolution. This work is based on observations collected at the European Southern Observatory, Paranal (programme IDs ESO 087.D-0355, 087.D-0440, 087.D-0673, and 073.D-0327) and uses the ISO-SWS database of Sloan et al. (2003).Table 1 and Appendix A are available in electronic form at http://www.aanda.org

  10. A study of several F and G supergiant-like stars with infrared excesses as candidates for proto-planetary nebulae

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.; Kwok, Sun; Volk, Kevin M.

    1989-01-01

    Ground-based observations have been obtained for eight F and G supergiant-like stars showing large IR excesses. The combination of ground-based and IRAS data shows that these objects have dual-peak energy distributions, with comparable amounts of energy emitted in the visible and the IR. The IR-emitting cool dust shells are likely to represent the remnants of ejecta from an earlier phase of evolution. It is suggested that these eight objects are similar to IRAS 18095 + 2704 and are intermediate-mass stars in a post-AGB phase of evolution. Model fittings to the 0.4-100 micron energy distribution of these objects suggest that they left the AGB within the last 1000 yr.

  11. NuSTAR detection of a cyclotron line in the supergiant fast X-ray transient IGR J17544-2619

    NASA Astrophysics Data System (ADS)

    Bhalerao, Varun; Romano, Patrizia; Tomsick, John; Natalucci, Lorenzo; Smith, David M.; Bellm, Eric; Boggs, Steven E.; Chakrabarty, Deepto; Christensen, Finn E.; Craig, William W.; Fuerst, Felix; Hailey, Charles J.; Harrison, Fiona A.; Krivonos, Roman A.; Lu, Ting-Ni; Madsen, Kristin; Stern, Daniel; Younes, George; Zhang, William

    2015-03-01

    We present NuSTAR spectral and timing studies of the supergiant fast X-ray transient (SFXT) IGR J17544-2619. The spectrum is well described by an ˜1 keV blackbody and a hard continuum component, as expected from an accreting X-ray pulsar. We detect a cyclotron line at 17 keV, confirming that the compact object in IGR J17544-2619 is indeed a neutron star. This is the first measurement of the magnetic field in an SFXT. The inferred magnetic field strength, B = (1.45 ± 0.03) × 1012G (1 + z) is typical of neutron stars in X-ray binaries, and rules out a magnetar nature for the compact object. We do not find any significant pulsations in the source on time-scales of 1-2000 s.

  12. New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619

    NASA Astrophysics Data System (ADS)

    Drave, S. P.; Bird, A. J.; Sidoli, L.; Sguera, V.; Bazzano, A.; Hill, A. B.; Goossens, M. E.

    2014-04-01

    XMM-Newton observations of the supergiant fast X-ray transient IGR J17544-2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272 ± 0.0004 d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations (each lasting ˜15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544-2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033 erg s-1 (0.5-10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544-2619 dropped to ˜4 × 1032 erg s-1 (0.5-10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544-2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544-2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the `quasi-spherical accretion' model provides a good description of the behaviour of IGR J17544-2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.

  13. Chemical Communication

    NSDL National Science Digital Library

    0000-00-00

    A concise lesson about chemical communication in insects covering both semio and info chemicals. The site includes a short video of grape root borer moths using sex pheromone. Further links on the take the user to visual and auditory communication.

  14. Chemical Oxidation

    Microsoft Academic Search

    Nazih K. Shammas; John Y. Yang; Pao-Chiang Yuan; Yung-Tse Hung

    Chemical oxidation is a process involving the transfer of electrons from an oxidizing reagent to the chemical species being\\u000a oxidized. In water and wastewater engineering, chemical oxidation serves the purpose of converting putrescible pollutant substances\\u000a to innocuous or stabilized products. Chemical oxidation processes take place in natural waters and serve as an important mechanism\\u000a in the natural self-purification of surface

  15. Home Chemicals

    NSDL National Science Digital Library

    Chris Fox

    This lesson provides an introduction to the occurrence and possible risks of household chemical products. Topics include some basic chemistry (how elements combine to form compounds), how chemicals are classified, and the idea of natural, as opposed to synthetic, chemicals. The lesson includes an activity in which students take an inventory of chemical products in their homes and research the possible hazards of some of them using an online resource developed by the National Institutes of Health (NIH).

  16. Chemical Innovation

    NSDL National Science Digital Library

    Free online through December 2000, Chemical Innovation is a monthly journal that explores topics in research and development in chemical industries, and features such departments as Patent Watch, Chemist at Large, Book Alert, and The Industrial Chemist. The journal also shows a lighter side by including chemistry-related cartoons and jokes. The online version is provided by the American Chemical Society.

  17. 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

  18. [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. PMID:16296384

  19. Chemical Bonds

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    Electrons are key to forming the two broad categories of chemical bonds: covalent and ionic. Atoms, which have a nucleus surrounded by electrons, are represented in several different ways. In the Chemical Bonds activity, students explore the different kinds of chemical bonds that can form, ranging from non-polar covalent to ionic. In the model depicted above students adjust the electronegativity of two atoms and see the effect it has on electron distribution and bond type.

  20. Chemical microsensors

    DOEpatents

    Li, DeQuan (Los Alamos, NM); Swanson, Basil I. (Los Alamos, NM)

    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.

  1. 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. [Department of Space and Astronautical Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), 3-1-1 Yoshinodai, Chuou-Ku, Sagamihara, Kanagawa 252-5210 (Japan); Imai, H. [Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Oyama, T., E-mail: kusuno@vsop.isas.jaxa.jp, E-mail: asaki@vsop.isas.jaxa.jp, E-mail: hiroimai@sci.kagoshima-u.ac.jp, E-mail: t.oyama@nao.ac.jp [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    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.

  2. Chemical Name

    Cancer.gov

    Attachment III Chemical Quick Reference Chart for Minors Chemical Name Select Carcinogen Reproductive Toxin LD50 < 50 mg/kg (oral rat) LD50 < 200 mg/kg for 24 hours or less (dermal rabbit) LC50 < 200 ppm or 2 mg/L for one hour (inhalation rat)

  3. Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-05-01

    We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

  4. Chemical Linkage

    Microsoft Academic Search

    R. F. Hunter; R. Samuel

    1934-01-01

    IN the Research Items in NATURE of October 20, certain arguments are advanced in opposition to the views which we expressed in a recent paper published in the Journal of the Chemical Society, and without going into detail we wish to take the opportunity of pointing out that : (1) We cannot call to mind any evidence, chemical or physical,

  5. What causes the large extensions of red-supergiant atmospheres? Comparisons of interferometric observations with 1-D hydrostatic, 3-D convection, and 1-D pulsating model atmospheres

    E-print Network

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

    2015-01-01

    We present the atmospheric structure and the fundamental parameters of three red supergiants, increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. We carried out spectro-interferometric observations of 3 RSGs in the near-infrared K-band with the VLTI/AMBER instrument at medium spectral resolution. To comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3-D convection, and new 1-D self-excited pulsation models of RSGs. Our near-infrared flux spectra are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict ...

  6. 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)

  7. Chemical Weathering

    NSDL National Science Digital Library

    Kira Lawrence

    This tombstone weathering lab is designed to provide students with tangible understanding of chemical weathering and weathering rates. To prepare for this lab, students will have learned in previous labs to identify common minerals and rocks and will have attended lectures about the process of chemical weathering. During the first part of the lab we travel to the city cemetery to collect data on the age and extent of chemical weathering of tombstones that are made of limestone and igneous rocks. After collecting data for ~1 hour, we return to the computer lab where students use Microsoft Excel to analyze and interpret their data. Their task is to calculate a chemical weathering rate for limestone for our region and compare that rate to those from other regions. This activity gives students experience in the process of scientific inquiry: data collection, data analysis and data interpretation. Students develop Microsoft Excel skills: writing formulas, producing charts, understanding trendlines and R2 values.

  8. Chemical Emergency

    MedlinePLUS

    ... Landslide Pet Safety Poisoning Power Outage Terrorism Thunderstorm Tornado Tsunami Volcano Water Safety Wildfire Winter Storm Tools ... and your family is to be prepared. In Case of Poisoning The most common home chemical emergencies ...

  9. 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.

  10. High spectral resolution imaging of the dynamical atmosphere of the red supergiant Antares in the CO first overtone lines with VLTI/AMBER

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.; Hofmann, K.-H.; Schertl, D.; Weigelt, G.; Baffa, C.; Chelli, A.; Petrov, R.; Robbe-Dubois, S.

    2013-07-01

    Aims: We present aperture-synthesis imaging of the red supergiant Antares (? Sco) in the CO first overtone lines. Our goal is to probe the structure and dynamics of the outer atmosphere. Methods: Antares was observed between 2.28 ?m and 2.31 ?m with VLTI/AMBER with spectral resolutions of up to 12 000 and angular resolutions as high as 7.2 mas at two epochs with a time interval of one year. Results: The reconstructed images in individual CO lines reveal that the star appears differently in the blue wing, line center, and red wing. In 2009, the images in the line center and red wing show an asymmetrically extended component, while the image in the blue wing shows little trace of it. In 2010, however, the extended component appears in the line center and blue wing, and the image in the red wing shows only a weak signature of the extended component. Our modeling of these AMBER data suggests that there is an outer atmosphere (MOLsphere) extending to 1.2-1.4 R? with CO column densities of (0.5-1) × 1020 cm-2 and a temperature of ~2000 K. The CO line images observed in 2009 can be explained by a model in which a large patch or clump of CO gas is infalling at only 0-5 km s-1, while the CO gas in the remaining region is moving outward much faster at 20-30 km s-1. The images observed in 2010 suggest that a large clump of CO gas is moving outward at 0-5 km s-1, while the CO gas in the remaining region is infalling much faster at 20-30 km s-1. In contrast to the images in the CO lines, the AMBER data in the continuum show only a slight deviation from limb-darkened disks and only marginal time variations. We derive a limb-darkened disk diameter of 37.38 ± 0.06 mas and a power-law-type limb-darkening parameter of (8.7 ± 1.6) × 10-2 (2009) and 37.31 ± 0.09 mas and (1.5 ± 0.2) × 10-1 (2010). We also obtain an effective temperature of 3660 ± 120 K (the error includes the effects of the temporal flux variation that is assumed to be the same as Betelgeuse) and a luminosity of log L?/L? = 4.88 ± 0.23. Comparison with theoretical evolutionary tracks suggests a mass of 15 ± 5 M? with an age of 11-15 Myr, which is consistent with the recently estimated age for the Upper Scorpius OB association. Conclusions: The properties of the outer atmosphere of Antares are similar to those of another well-studied red supergiant, Betelgeuse. The density of the extended outer atmosphere of Antares and Betelgeuse is higher than predicted by the current 3D convection simulations by at least six orders of magnitude, implying that convection alone cannot explain the formation of the extended outer atmosphere. Based on AMBER observations made with the Very Large Telescope Interferometer of the European Southern Observatory. Program ID: 083.D-0333(A/B) (AMBER guaranteed time observation), 085.D-0085(A/B).Appendices are available in electronic form at http://www.aanda.orgMovies of data cube are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A24

  11. LUMINOUS SUPERNOVA-LIKE UV/OPTICAL/INFRARED TRANSIENTS ASSOCIATED WITH ULTRA-LONG GAMMA-RAY BURSTS FROM METAL-POOR BLUE SUPERGIANTS

    SciTech Connect

    Kashiyama, Kazumi; Yajima, Hidenobu [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Nakauchi, Daisuke; Nakamura, Takashi [Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan); Suwa, Yudai, E-mail: kzk15@psu.edu [Yukawa Institute for Theoretical Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)

    2013-06-10

    Metal-poor massive stars typically end their lives as blue supergiants (BSGs). Gamma-ray bursts (GRBs) from such progenitors could have an ultra-long duration of relativistic jets. For example, Population III (Pop III) GRBs at z {approx} 10-20 might be observable as X-ray-rich events with a typical duration of T{sub 90} {approx} 10{sup 4}(1 + z) s. The recent GRB111209A at z = 0.677 has an ultra-long duration of T{sub 90} {approx} 2.5 Multiplication-Sign 10{sup 4} s and it has been suggested that its progenitor might have been a metal-poor BSG in the local universe. Here, we suggest that luminous UV/optical/infrared emission is associated with this new class of GRBs from metal-poor BSGs. Before the jet head breaks out of the progenitor envelope, the energy injected by the jet is stored in a hot plasma cocoon, which finally emerges and expands as a baryon-loaded fireball. We show that the photospheric emissions from the cocoon fireball could be intrinsically very bright (L{sub peak} {approx} 10{sup 42}-10{sup 44} erg s{sup -1}) in UV/optical bands ({epsilon}{sub peak} {approx} 10 eV) with a typical duration of {approx}100 days in the rest frame. Such cocoon emissions from Pop III GRBs might be detectable in infrared bands at {approx}years after Pop III GRBs at up to z {approx} 15 by upcoming facilities such as the James Webb Space Telescope. We also suggest that GRB111209A might have been rebrightening in UV/optical bands up to an AB magnitude of {approx}< 26. The cocoon emission from local metal-poor BSGs might have been observed previously as luminous supernovae without GRBs since they can be seen from the off-axis direction of the jet.

  12. A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant zeta Orionis

    E-print Network

    A. M. T. Pollock

    2006-12-18

    XMM-Newton observations of the O supergiant zeta Orionis (O9.7 Ib) extend knowledge of its high-resolution spectrum beyond the CVI line at 33.7 Angstroms and suggest a new framework for the interpretation of the X-ray spectra of single hot stars. All the lines are broad and asymmetric with similar velocity profiles. X-rays probably originate in the wind's terminal velocity regime in collisionless shocks controlled by magnetic fields rather than in cooling shocks in the acceleration zone. During post-shock relaxation, exchange of energy between ions and electrons is so slow that electron heating does not take place before hot gas is quenched by the majority cool gas. The observed plasma is not in equilibrium and the electron bremsstrahlung continuum is weak. Charge exchange, ionization and excitation are likely to be produced by protons. Fully thermalized post-shock velocities ensure high cross-sections and account for the observed line widths, with some allowance probably necessary for non-thermal particle acceleration. In general, the form of X-ray spectra in both single and binary stars is likely to be determined principally by the amount of post-shock electron heating: magnetically confined X-ray plasma in binary systems can evolve further towards the higher electron temperatures of equilibrium while in single stars this does not take place. The long mean-free path for Coulomb energy exchange between fast-moving ions may also inhibit the development of line-driven instabilities.

  13. 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.

  14. Toward Connecting Core-collapse Supernova Theory with Observations. I. Shock Revival in a 15 M ? Blue Supergiant Progenitor with SN 1987A Energetics

    NASA Astrophysics Data System (ADS)

    Handy, Timothy; Plewa, Tomasz; Odrzywo?ek, Andrzej

    2014-03-01

    We study the evolution of the collapsing core of a 15 M ? 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.

  15. Long-lasting X-Ray Emission from Type IIb Supernova 2011dh and Mass-loss History of the Yellow Supergiant Progenitor

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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 × 10-6 M ? yr-1 for the mass-loss velocity of ~20 km s-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. Chemical Changes

    NSDL National Science Digital Library

    can& #39; t tell- a science educator- not affiliated with any specific organization

    2011-10-10

    This is an excellent resource for teachers and students. It offers countless lab ideas for teaching chemical and physical changes and is geared for fifth through eighth grade. It also gives interactive web addresses for students and includes PowerPoint presentations on this topic.

  17. Chemical separations

    SciTech Connect

    King, J.C.; Navratil, J.D.

    1986-01-01

    This volume collects papers presented at a conference on chemical separation. Topics include: field-flow fractionation, chromatography, electrophoresis, solvent extraction in metals recovery, extraction of uranium and plutonium from nitric acid, modeling of flow fields in oscillating droplets, inclusion, and membrane processes.

  18. Chemical Wonders

    NSDL National Science Digital Library

    Integrated Teaching and Learning Program,

    Students are introduced to chemical engineering and learn about its many different applications. They are provided with a basic introduction to matter and its different properties and states. An associated hands-on activity gives students a chance to test their knowledge of the states of matter and how to make observations using their five senses: touch, smell, sound, sight and taste.

  19. 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…

  20. 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…

  1. Chemical Reactions

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-05-04

    We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

  2. 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

  3. Optical spectra of five new Be/X-ray binaries in the Small Magellanic Cloud and the link of the supergiant B[e] star LHA 115-S 18 with an X-ray source

    NASA Astrophysics Data System (ADS)

    Maravelias, G.; Zezas, A.; Antoniou, V.; Hatzidimitriou, D.

    2014-03-01

    The Small Magellanic Cloud (SMC) is well known to harbour a large number of high-mass X-ray binaries (HMXBs). The identification of their optical counterparts provides information on the nature of the donor stars and can help to constrain the parameters of these systems and their evolution. We obtained optical spectra for a number of HMXBs identified in previous Chandra and XMM-Newton surveys of the SMC using the AAOmega/2dF fibre-fed spectrograph at the Anglo-Australian Telescope. We find five new Be/X-ray binaries (BeXRBs; including a tentative one), by identifying the spectral type of their optical counterparts, and we confirm the spectral classification of an additional 15 known BeXRBs. We compared the spectral types, orbital periods and eccentricities of the BeXRB populations in the SMC and the Milky Way and we find marginal evidence for difference between the spectral type distributions, but no statistically significant differences for the orbital periods and the eccentricities. Moreover, our search revealed that the well-known supergiant B[e] star LHA 115-S 18 (or AzV 154) is associated with the weak X-ray source CXOU J005409.57-724143.5. We provide evidence that the supergiant star LHA 115-S 18 is the optical counterpart of the X-ray source, and we discuss different possibilities of the origin of its low X-ray luminosity (Lx ˜ 4 × 1033 erg s-1).

  4. 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 schools, or of U.S.…

  5. Carbon abundance and the N/C ratio in atmospheres of A-, F- and G-type supergiants and bright giants

    NASA Astrophysics Data System (ADS)

    Lyubimkov, Leonid S.; Lambert, David L.; Korotin, Sergey A.; Rachkovskaya, Tamara M.; Poklad, Dmitry B.

    2015-02-01

    Based on our prior accurate determination of fundamental parameters for 36 Galactic A-, F- and G-type supergiants and bright giants (luminosity classes I and II), we undertook a non-LTE analysis of the carbon abundance in their atmospheres. It is shown that the non-LTE corrections to the C abundances derived from C I lines are negative and increase with the effective temperature Teff; the corrections are especially significant for the infrared C I lines with wavelengths 9060-9660 Å. The carbon underabundance as a general property of the stars in question is confirmed; a majority of the stars studied has the carbon deficiency [C/Fe] between -0.1 and -0.5 dex, with a minimum at -0.7 dex. When comparing the derived C deficiency with the N excess found by us for the same stars earlier, we obtain a pronounced N versus C anticorrelation, which could be expected from predictions of the theory. We found that the ratio [N/C] spans mostly the range from 0.3 to 1.7 dex. Both these enhanced [N/C] values and the C and N anomalies themselves are an obvious evidence of the presence on a star's surface of mixed material from stellar interiors; so, a majority of programme stars passed through the deep mixing during the main sequence (MS) and/or the first dredge-up (FD) phase. Comparison with theoretical predictions including rotationally induced mixing shows that the stars are either post-MS objects with the initial rotational velocities V0 = 200-300 km s-1 or post-FD objects with V0 = 0-300 km s-1. The observed N versus C anticorrelation reflects a dependence of the C and N anomalies on the V0 value: on average the higher V0 the greater the anomalies. It is shown that an absence of detectable lithium in the atmospheres of the stars, which is accompanied with the observed N excess and C deficiency, is quite explainable.

  6. 1-D Imaging of the Dynamical Atmosphere of the Red Supergiant Betelgeuse in the CO First Overtone Lines with VLTI/AMBER

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.

    2014-09-01

    We present high-spatial and high-spectral resolution observations of the red supergiant Betelgeuse in the CO first overtone lines near 2.3?m with the AMBER instrument at the Very Large Telescope Interferometer (VLTI). Our AMBER observations in 2008 spatially resolved the gas motions in a stellar atmosphere (photosphere and extended molecular outer atmosphere) for the first time other than the Sun. From our second observations one year later, we have reconstructed 1-D images in the individual CO lines with an angular resolution of 9.8 mas and a spectral resolution of 6000 by applying the self-calibration technique to restore the Fourier phase from the differential phase measurements. The reconstructed 1-D images reveal that the star appears different in the blue and red wing of the individual CO lines. In the blue wing, the star shows a pronounced, asymmetrically extended component at least up to 1.3 R?, while such a component does not appear in the red wing 1-D image. This can be explained by a model in which the CO gas patch (or clump) more than half as large as the star is moving slightly outward with 0-5 km s-1, while the gas in the remaining region is infalling fast with 20-30 km s-1. Comparison between the CO line data taken in 2008 and 2009 shows a significant time variation in the dynamics of the photosphere and outer atmosphere. However, the 1-D images in the continuum show only a slight deviation from a limb-darkened disk with an angular diameter of 42.49±0.06 mas, which leads to an effective temperature of 3690± 54 K. Moreover, the continuum data taken in 2008 and 2009 reveal no or only marginal time variations, much smaller than the maximum variation predicted by the current 3-D convection simulation. The derived continuum diameter also shows that the near-IR size of Betelgeuse has been nearly constant over the last 18 years, in marked contrast to the recently reported noticeable decrease in the mid-IR size.

  7. What causes the large extensions of red supergiant atmospheres?. Comparisons of interferometric observations with 1D hydrostatic, 3D convection, and 1D pulsating model atmospheres

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Aims: This research has two main goals. First, we present the atmospheric structure and the fundamental parameters of three red supergiants (RSGs), increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. Methods: We carried out spectro-interferometric observations of the RSGs V602 Car, HD 95687, and HD 183589 in the near-infrared K-band (1.92-2.47 ?m) with the VLTI/AMBER instrument at medium spectral resolution (R ~ 1500). To categorize and comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3D convection, and new 1D self-excited pulsation models of RSGs. Results: Our near-infrared flux spectra of V602 Car, HD 95687, and HD 183589 are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict the large observed extensions of molecular layers, most remarkably in the CO bands. Likewise, the 3D convection models and the 1D pulsation models with typical parameters of RSGs lead to compact atmospheric structures as well, which are similar to the structure of the hydrostatic PHOENIX models. They can also not explain the observed decreases in the visibilities and thus the large atmospheric molecular extensions. The full sample of our RSGs indicates increasing observed atmospheric extensions with increasing luminosity and decreasing surface gravity, and no correlation with effective temperature or variability amplitude. Conclusions: The location of our RSG sources in the Hertzsprung-Russell diagram is confirmed to be consistent with the red limits of recent evolutionary tracks. The observed extensions of the atmospheric layers of our sample of RSGs are comparable to those of Mira stars. This phenomenon is not predicted by any of the considered model atmospheres including available 3D convection and new 1D pulsation models of RSGs. This confirms that neither convection nor pulsation alone can levitate the molecular atmospheres of RSGs. Our observed correlation of atmospheric extension with luminosity supports a scenario of radiative acceleration on Doppler-shifted molecular lines. Based on observations made with the VLT Interferometer (VLTI) at Paranal Observatory under programme ID 091.D-0275.Figures 2-6 are available in electronic form at http://www.aanda.org

  8. Chemical Separations

    NSDL National Science Digital Library

    This site contains complete notes in a PowerPoint-like presentation for a chemical separations course. It covers a wide variety of topics, including distillation, extraction, gas chromatography, liquid chromatograpy, chromatography theory, instrumentation, electrophoresis, field flow fractionation, and affinity chromatography. It covers these topics thoroughly using a clear, consistent, and simple presentation style. Links to major topics like GC, LC, and electrophoresis provide specific information about the theory, instrumentation, and practice related to these techniques. The site also contains many annimations illustrating important separation processes.

  9. Chemical Accelerators The phrase "chemical accelerators"

    E-print Network

    Zare, Richard N.

    that there is a wealth of important chemistry occurring only at higher energies (of the order of the strength of chemicalMeetings Chemical Accelerators The phrase "chemical accelerators" is scarcely older than for one or two dozen people grew to include nearly a hundred. Chemical accelerators is a name sug- gested

  10. 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-absorptions reflect a wind turbulence of approximately equal 9-21 km/s. We further characterize the wind by comparing the observations with synthetic profiles generated with the Lamers et al. Sobolev with Exact Integration (SEI) radiative transfer code, assuming simple models of the outer atmospheric structure. These comparisons indicate that the wind in 1994 can be described by a model with a wind acceleration parameter beta approximately 0.9, a terminal velocity of 29-33 km/s, and a mass-loss rate approximately 3 x 10(exp -9) solar M/yr. Modeling of the 3.6 cm radio flux observed in 1997 suggests a more slowly accelerating wind (higher beta) and/or a higher mass-loss rate than inferred from the UV line profiles. These differences may be due to temporal variations in the wind or from limitations in one or both of the models. The discrepancy is currently under investigation.

  11. 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 5?) 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 5? 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 5? 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 ?), 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 expected number of flares for a given source for our limiting flux and provide the recipe for calculating them for the limiting flux of future hard X-ray observatories. Project web page: http://www.ifc.inaf.it/sfxt/Full Table 4 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A2

  12. The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. IV. Construction and Validation of a Grid of Models for Oxygen-rich AGB Stars, Red Supergiants, and Extreme AGB Stars

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, S.; Meixner, M.

    2011-02-01

    To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores four parameters—stellar effective temperature from 2100 K to 4700 K luminosity from 103 to 106 L sun; dust shell inner radii of 3, 7, 11, and 15 R star; and 10.0 ?m optical depth from 10-4 to 26. From an initial grid of ~1200 2Dust models, we create a larger grid of ~69,000 models by scaling to cover the luminosity range required by the data. These models are available online to the public. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR stars is generally very good. The extreme AGB star candidates from SAGE are more consistent with carbon-rich (C-rich) than O-rich dust composition. Our model grid suggests lower limits to the mid-infrared colors of the dustiest AGB stars for which the chemistry could be O-rich. Finally, the fitting of GRAMS models to spectral energy distributions of sources fit by other studies provides additional verification of our grid and anticipates future, more expansive efforts.

  13. 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)

  14. Microfluidic chemical reaction circuits

    DOEpatents

    Lee, Chung-cheng (Irvine, CA); Sui, Guodong (Los Angeles, CA); Elizarov, Arkadij (Valley Village, CA); Kolb, Hartmuth C. (Playa del Rey, CA); Huang, Jiang (San Jose, CA); Heath, James R. (South Pasadena, CA); Phelps, Michael E. (Los Angeles, CA); Quake, Stephen R. (Stanford, CA); Tseng, Hsian-rong (Los Angeles, CA); Wyatt, Paul (Tipperary, IE); Daridon, Antoine (Mont-Sur-Rolle, CH)

    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.

  15. CHEMICAL SAFETY ALERTS-

    EPA Science Inventory

    Chemical Safety Alerts are short publications which explain specific hazards that have become evident through chemical accident investigation efforts. EPA has produced over a dozen Alerts to date. This year's Alert: Managing Chemical Reactivity Hazards...

  16. CHEMICALS IN PROGRESS BULLETIN

    EPA Science Inventory

    Chemicals in Progress Bulletin is a quarterly newsletter which highlights regulatory and program activities of the Office of Pollution Prevention and Toxics. Regular features and news items include the existing chemicals program, new chemicals program, pollution prevention activi...

  17. The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars

    NASA Astrophysics Data System (ADS)

    Hunter, I.; Brott, I.; Langer, N.; Lennon, D. J.; Dufton, P. L.; Howarth, I. D.; Ryans, R. S. I.; Trundle, C.; Evans, C. J.; de Koter, A.; Smartt, S. J.

    2009-03-01

    Aims: We have previously analysed the spectra of 135 early B-type stars in the Large Magellanic Cloud (LMC) and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and Small Magellanic Cloud (SMC) metallicities. Methods: We provide chemical compositions for ~50 Galactic and ~100 SMC early B-type stars and compare these to the LMC results. These samples cover a range of projected rotational velocities up to ~300 km s-1 and hence are well suited to testing rotational mixing models. The surface nitrogen abundances are utilised as a probe of the mixing process since nitrogen is synthesized in the core of the stars and mixed to the surface. Results: In the SMC, we find a population of slowly rotating nitrogen-rich stars amongst the early B type core-hydrogen burning stars, which is comparable to that found previously in the LMC. The identification of non-enriched rapid rotators in the SMC is not possible due to the relatively high upper limits on the nitrogen abundance for the fast rotators. In the Galactic sample we find no significant enrichment amongst the core hydrogen-burning stars, which appears to be in contrast with the expectation from both rotating single-star and close binary evolution models. However, only a small number of the rapidly rotating stars have evolved enough to produce a significant nitrogen enrichment, and these may be analogous to the non-enriched rapid rotators previously found in the LMC sample. Finally, in each metallicity regime, a population of highly enriched supergiants is observed, which cannot be the immediate descendants of core-hydrogen burning stars. Their abundances are, however, compatible with them having gone through a previous red supergiant phase. Together, these observations paint a complex picture of the nitrogen enrichment in massive main sequence and supergiant stellar atmospheres, where age and binarity cause crucial effects. Whether rotational mixing is required to understand our results remains an open question at this time, but could be answered by identifying the true binary fraction in those groups of stars that do not agree with single-star evolutionary models. Based on observations at the European Southern Observatory in programmes 171.0237 and 073.0234. Figure 1 and Tables 1 and 2 are only available in electronic form at http://www.aanda.org

  18. CHEMICAL SAFETY Emergency Numbers

    E-print Network

    Bolch, Tobias

    Storage 11 Chemical Inventory 12 Chemical Transportation 13 Chemical Labeling 13 Chemical Spills 14 Ethidium Bromide Spills 15 Injuries 16 4. Laboratory Safety Inspections Safety Officer Inspections 17 5 Oxidizing Materials 22 Toxic Materials 24 Corrosive Materials 24 Dangerously Reactive Materials 25 7

  19. The chemical life(1).

    PubMed

    Hodges, Nathan

    2015-06-01

    You write this narrative autoethnography to open up a conversation about our chemical lives. You go through your day with chemical mindfulness, questioning taken-for-granted ideas about natural and artificial, healthy and unhealthy, dependency and addiction, trying to understand the chemical messages we consume through the experiences of everyday life. You reflect on how messages about chemicals influence and structure our lives and why some chemicals are celebrated and some are condemned. Using a second-person narrative voice, you show how the personal is relational and the chemical is cultural. You write because you seek a connection, a chemical bond. PMID:24905820

  20. 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.

  1. CHEMICAL ENGINEERING AND MANUFACTURING CHEMICAL ENGINEERING

    E-print Network

    Provancher, William

    are involved in the production of food, cosmetics, fuels, and anything else that requires the mixing: chemistry, chemical equations, math, etc.) There is a branch of Chemical Engineering called Process on a large scale. This applies to all production: crude oil separation, food processing, cosmetic

  2. Chemical Signals Production

    E-print Network

    Wilkinson, Gerald S.

    ­ Food detection ­ Social signals (vomeronasal organs) #12;Olfactory signal features · Directionality organ ­ Responds to range of different chemicals ­ Sensitive to low concentrations · Labeled-line coding ­ Individual receptors respond to single chemicals ­ Organ has many different cells types ­ Higher sensitivity

  3. Physical vs Chemical Changes

    NSDL National Science Digital Library

    The phenomena are physical changes, including the crushing of a can, melting of ice, and melting of sugar, and chemical changes, including and the rusting of iron and burning of sugar. This analysis will address the chemical change component.

  4. DTP - Chemical Biology Consortium

    Cancer.gov

    Chemical Biology Consortium Home Discovery Development Pathways Grants/Contracts Books/Publications Site Search Data Search What's New Chemical Biology Consortium (CBC) Division of Cancer Treatment and Diagnosis To download Adobe Reader for documents

  5. Household Chemical Emergencies

    MedlinePLUS

    ... the risk of injury. Before Before a Household Chemical Emergency The following are guidelines for buying and ... is (800) 222-1222. During During a Household Chemical Emergency Get out of the residence immediately if ...

  6. 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.

  7. Tobacco and chemicals (image)

    MedlinePLUS

    Some of the chemicals associated with tobacco smoke include ammonia, carbon dioxide, carbon monoxide, propane, methane, acetone, hydrogen cyanide and various carcinogens. Other chemicals that are associated with chewing ...

  8. Floor Chemical Basics.

    ERIC Educational Resources Information Center

    Shaw, Richard

    1998-01-01

    Discusses the issues to consider when selecting floor-care chemicals, including the floor-finish systems for hard-surface floors and the care of carpeted floors. Provides thoughts on cleaning chemical usage and environmental awareness. (GR)

  9. Chemistry 455 Chemical Nanotechnology

    E-print Network

    Rohs, Remo

    Chemistry 455 Chemical Nanotechnology 4 units Prof. Richard Brutchey, Fall 2014 (Lecture = 12:00­12:50 pm MWF) CHEM 455 is an upper-division undergraduate course in Chemical Nanotechnology. The intent

  10. Chemical Reactions (Netorials)

    NSDL National Science Digital Library

    Chemical Reactions: this is a resource in the collection "Netorials". The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

  11. Physical and Chemical Change

    NSDL National Science Digital Library

    Mr. Wood

    2010-11-15

    Overview of physical and chemical changes with practice activities and a quiz. Worksheet - Physical Chemical Change Worksheet After viewing the worksheet, copy and paste it into a new blank Google Document - MyDSD Google Login Title your Document "Chemical and Physical Change". Make sure to include your name and period in the body of the doc. The answers in your document should be a different color or font. Examples of Chemical Changes Changes info page More Examples After completing the rest ...

  12. Chemical of the Week

    NSDL National Science Digital Library

    Shakhashiri, Bassam Z.

    1997-01-01

    Professor Bassam Z. Shakhashiri at the University of Wisconsin-Madison adds a new chemical to this page every week. The site was created for his general chemistry courses, Chem 103 and Chem 104, to increase students' knowledge about various chemicals and their use. Users can view featured chemicals from the currently updated fall course (103) or from the spring course (104). The chemicals featured thus far include: lime, methane, uranium, the chemistry of autumn colors, and gases that emit light.

  13. 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.

  14. More on Chemical Changes

    NSDL National Science Digital Library

    The phenomenon is a series of chemical reactions and observation of signs of a chemical change. The laboratory activities can be done by students or as a teacher demonstration. They involve mixing chemicals and noting color change, formation of a precipitate, and production of a gas.

  15. HARVARD UNIVERSITY CHEMICAL BIOLOGY

    E-print Network

    Church, George M.

    HARVARD UNIVERSITY CHEMICAL BIOLOGY PHD PROGRAM 2013-2014 Student Handbook #12;Program Contacts at the beginning of each semester. Laboratory Rotations Students in the Chemical Biology Program are expected an interest in having Chemical Biology Program Students in their labs. Students may rotate in the labs

  16. 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.

  17. AGRICULTURAL CHEMICAL USAGE DATA

    EPA Science Inventory

    This report, which summarizes the use of agricultural chemicals is issued by the National Agricultural Statistics Service (NASS) as part of its series on Agricultural Chemical Usage. Other publications in the series present statistics for on-farm agricultural chemical usage for f...

  18. 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)

  19. Equilibrium Chemical Engines

    E-print Network

    Tatsuo Shibata; Shin-ichi Sasa

    1997-10-30

    An equilibrium reversible cycle with a certain engine to transduce the energy of any chemical reaction into mechanical energy is proposed. The efficiency for chemical energy transduction is also defined so as to be compared with Carnot efficiency. Relevance to the study of protein motors is discussed. KEYWORDS: Chemical thermodynamics, Engine, Efficiency, Molecular machine.

  20. Chemical Plume Source Localization

    Microsoft Academic Search

    Shuo Pang; Jay A. Farrell

    2006-01-01

    This paper addresses the problem of estimating a likelihood map for the location of the source of a chemical plume using an autonomous vehicle as a sensor probe in a fluid flow. The fluid flow is assumed to have a high Reynolds number. Therefore, the dispersion of the chemical is dominated by turbulence, resulting in an intermittent chemical signal. The

  1. Chemistry Review: Chemical Change

    NSDL National Science Digital Library

    James Kessler

    2010-01-01

    This review provides many details about chemical reactions and the components involved in order to make one happen, such as energy, heat, density, and substance. Provided are animations that show molecular combustion that occurs with a chemical reaction. The role of atoms is also described, including Ionic bonds that occur or break in a chemical reaction. Simple experiments use substances such as vinegar, water, and baking soda to show a real chemical reaction in progress. Temperature change in chemical reactions is explained in detail, along with endothermic and exothermic reactions.

  2. Chemical Reactivity Worksheet

    NSDL National Science Digital Library

    2012-08-24

    The National Oceanic and Atmospheric Administration's (NOAA) Office of Response and Restoration has created the Chemical Reactivity Worksheet to help teachers, students, and the general public learn about the chemical reactivity of thousands of common hazardous chemicals. After downloading a free program, visitors will find that the datasheets contain information about the hazards of a number of chemicals, along with information on whether a chemical reacts with air, water, or other materials. Visitors can create their own custom chemical datasheets or virtually "mix" chemicals to find out what dangers might arise from accidental mixing. The site is rounded out by an excellent FAQ section, along with information about the technical specifications of the program and a development history.

  3. 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 unneeded chemicals and the amount spent on new purchases, but will also avoid disposal costs. If SNL/NM were to realize a 5 percent reduction in chemical inventory and a 10 percent reduction in disposal of unused chemicals the total savings would be $189, 200 per year.

  4. Chemical evolution STRUCTURE OF GALAXIES

    E-print Network

    Kruit, Piet van der

    Outline Absorption Chemical evolution STRUCTURE OF GALAXIES 8. Absorption; chemical evolution Piet Piet van der Kruit, Kapteyn Astronomical Institute Absorption; chemical evolution #12;Outline Absorption Chemical evolution Outline Absorption Holmberg's analysis Analysis of Disney et al. Edge

  5. Journal of Chemical Education: Chemical Resource Shelf

    NSDL National Science Digital Library

    1995-01-01

    Produced under the auspices of the Journal of Chemical Education Online, this site is the basis for that journal's "Book Buyer's Guide." It provides high school and college-level chemistry educators with various teaching resources, including a comprehensive index to chemistry textbooks in print. The index is arranged by subject, under which entries are listed in chronological order, from newest to oldest. Subjects covered range from Biochemistry and Computers in Chemistry to Quantum Chemistry and Writing in Science. In addition to basic bibliographic information, when available, each entry includes citations of reviews and links to publishers' online catalogs. Another feature is "Hal's Picks of the Month," a growing archive of over 30 "books and recent articles for teachers of chemistry and related sciences" as recommended and reviewed by Professor Harold (Hal) Harris of the University of Missouri - St. Louis Chemistry Department. "Journals of Interest to Chemical Educators" and "Suppliers of Software for Chemical Education" are two other lists available at this site.

  6. Hand chemical burns.

    PubMed

    Robinson, Elliot P; Chhabra, A Bobby

    2015-03-01

    There is a vast and ever-expanding variety of potentially harmful chemicals in the military, industrial, and domestic landscape. Chemical burns make up a small proportion of all skin burns, yet they can cause substantial morbidity and mortality. Additionally, the hand and upper extremity are the most frequently involved parts of the body in chemical burns, and therefore these injuries may lead to severe temporary or permanent loss of function. Despite this fact, discussion of the care of these injuries is sparse in the hand surgery literature. Although most chemical burns require only first response and wound care, some require the attention of a specialist for surgical debridement and, occasionally, skin coverage and reconstruction. Exposure to certain chemicals carries the risk of substantial systemic toxicity and even mortality. Understanding the difference between thermal and chemical burns, as well as special considerations for specific compounds, will improve patient treatment outcomes. PMID:25653184

  7. 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.

  8. Miniature chemical measurement systems

    SciTech Connect

    Ramsey, J.M.

    1996-12-31

    Prospect of microfabricated monolithic devices that accomplish complete chemical assays is enticing. Early work with microfabricated chemical analysis devices focused on separations methods. More recently reagent manipulation has been integrated with separation devices to create more powerful capabilities. Examples of procedures, other than separations, that have been demonstrated on micromachined structures include reagent mixing, dilution, and reaction, preconcentration through sample stacking and biopolymer tagging for detection. Developments in liquid phase microfabricated chemical analysis devices are reviewed.

  9. Insect Chemical Warfare

    NSDL National Science Digital Library

    0000-00-00

    Discussion of the Bombardier beetle's chemical defense, detailing the explosive qualities of the chemicals, where the beetle is found, a bit about distribution, and what the chemicals do to people. There's also a bit about insects in the news detailing the beetle's role in the ongoing religious debate as it pertains to how such an animal might evolve, with an aside about a Richard Dawkin's demonstration.

  10. 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.

  11. 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.

  12. Physical and Chemical Changes

    NSDL National Science Digital Library

    Mrs. Holly

    2010-11-15

    Physical and chemical changes in matter affect us every day. Use the following resources to help you understand these changes more completely. Read this document to help you understand the difference between physical and chemical changes in matter. definitions Watch this! It illustrates the physical change of matter. physical change video Now, watch this! It illustrates the chemical change of matter. chemical change video Click on this link to read and explore the Utah Science Sci-ber Site. It will help you to ...

  13. Apparatus for chemical synthesis

    DOEpatents

    Kong, Peter C. (Idaho Falls, ID); Herring, J. Stephen (Idaho Falls, ID); Grandy, Jon D. (Idaho Falls, ID)

    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.

  14. 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.

  15. Chemically Layered Porous Solids

    NASA Technical Reports Server (NTRS)

    Koontz, Steve

    1991-01-01

    Aerogels and other porous solids in which surfaces of pores have chemical properties varying with depth below macroscopic surfaces prepared by sequences of chemical treatments. Porous glass or silica bead treated to make two depth zones having different chemical properties. Beads dropped along tube filled with flowing gas containing atomic oxygen, generated in microwave discharge. General class of materials treatable include oxides of aluminum, silicon, zirconium, tin, titanium, and nickel, and mixtures of these oxides. Potential uses of treated materials include chromatographic separations, membrane separations, controlled releases of chemicals, and catalysis.

  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. Chemical Regulatory Reporting Worksheet Chemical Name CAS

    E-print Network

    Entekhabi, Dara

    -01-0 Hydrogen fluoride (gas) 7664-39-3 Department: PI / Supervisor: Chemical Reporter: Rooms: Submission Date-81-6 Tetrafluoroethane (134-A) 811-97-2 Thiodiglycol 111-48-8 Titanium tetrachloride 7550-45-0 Transformer Oil

  18. Systems Chemical Biology

    PubMed Central

    Oprea, Tudor I.; Tropsha, Alexander; Faulon, Jean-Loup; Rintoul, Mark D.

    2009-01-01

    The increasing availability of data related to genes, proteins and their modulation by small molecules, paralleled by the emergence of simulation tools in systems biology, has provided a vast amount of biological information. However, there is a critical need to develop cheminformatics tools that can integrate chemical knowledge with these biological databases, with the goal of creating systems chemical biology. PMID:17637771

  19. Chemical and Physical Changes

    NSDL National Science Digital Library

    The phenomenon is a chemical reaction between sugar and sulfuric acid. The demonstration (a discrepant event) compares the way sugar and water interact when combined (physical change) to the way sugar and sulfuric acid interact when combined (chemical change). In part II, students are given additional substances and changes to observe.

  20. 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)

  1. 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)

  2. Elemental Chemical Puzzlers

    ERIC Educational Resources Information Center

    Thomas, Nicholas C.

    2009-01-01

    This paper provides nine short chemically based puzzles or problems extensible for use with students from middle school to college. Some of these will strengthen students' recognition of individual elements and element names. Others require students to focus on the salient properties of given chemical elements.

  3. Chemical warfare in freshwater

    Microsoft Academic Search

    Gabi Mulderij

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field experiments we studied the allelopathic effects of the aquatic macrophytes, Chara and Stratiotes. Laboratory experiments showed that

  4. Chemical Kinetics: Isolation Method

    NSDL National Science Digital Library

    David N. Blauch

    This site offers an interactive tutorial that guides the student through the Method of Isolation used for the determination of chemical reaction rate laws and rate constants. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.

  5. “Chemical Changes: Burning”

    NSDL National Science Digital Library

    Kris Ryan

    2012-07-25

    This lesson demonstrates how students can apply the process of identifying main idea and supporting details to show the different ways burning can chemically change matter. The students can identify these changes and discuss the details that support these changes, which will help them further understand how burning matter is considered a chemical change.

  6. Chemical Biology Consortium Agreement

    Cancer.gov

    NCI_CBC v.1.2 9/2009 The National Cancer Institute’s Chemical Biology Consortium Participants Agreement Mission: The mission of the National Cancer Institute’s (“NCI”) Chemical Biology Consortium (“CBC”) is to increase the flow of early

  7. Misconceptions of chemical equilibrium

    Microsoft Academic Search

    Mark W. Hackling; Patrick J. Garnett

    1985-01-01

    Those propositions deemed necessary for an understanding of chemical equilibrium and Le Chatelier's Principle were defined by the investigators and validated.Thirty, Year 12 Western Australian chemistry students (17 years of age) who had studied chemical equilibrium were interviewed and students’ responses were coded into various categories of misconception that had been identified. The most significant misconceptions revealed by the study

  8. NISt Chemical Kinetics Database

    NSDL National Science Digital Library

    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.

  9. 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...

  10. 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)

  11. Chemical warfare agents

    Microsoft Academic Search

    Rohit Shenoi

    2002-01-01

    There is an increased risk that civilian populations will be targets of domestic terrorism. Release of chemical warfare agents in these populations can cause a large number of casualties, with children being disproportionately affected. Chemical agents pose a significant risk to unprepared medical providers. Emergency medical personnel must be able to diagnose and manage victims of toxic exposures. This article

  12. Electropulse chemical machining

    Microsoft Academic Search

    T. A. Allen; S. D. Rospopo

    1984-01-01

    Electropulse Chemical Machining, a new technique in chemical milling was applied to the photoforming of molybdenum. Direct current was applied in short pulses at current densities of thousands of amperes per square foot with little thermal degradation of resists or workpieces. Etch rates an order of magnitude faster than those of existing methods, with a corresponding improvement in surface finish

  13. CHEMICAL PROCESSES IN SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    “Chemical Processes in Soils” edited by Tabatabai and D.L. Sparks (2005) is a key review useful for soil scientists, agronomists, conservationists, environmental scientists and other related professionals who need to understand these processes of chemical reactions and how they may be related to the...

  14. Chemical burn or reaction

    MedlinePLUS

    Chemicals that touch skin can lead to a reaction on the skin, throughout the body, or both. ... leave the person alone and watch carefully for reactions affecting the entire body. Note: If a chemical gets into the eyes, the eyes should be ...

  15. Chemical Reactions and Stoichiometry

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

  16. 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…

  17. Tortuous path chemical preconcentrator

    DOEpatents

    Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)

    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.

  18. Combination chemical genetics

    PubMed Central

    Lehár, Joseph; Stockwell, Brent R; Giaever, Guri; Nislow, Corey

    2009-01-01

    Predicting the behavior of living organisms is an enormous challenge given their vast complexity. Efforts to model biological systems require large datasets generated by physical binding experiments and perturbation studies. Genetic perturbations have proven important and are greatly facilitated by the advent of comprehensive mutant libraries in model organisms. Small-molecule chemical perturbagens provide a complementary approach, especially for systems that lack mutant libraries, and can easily probe the function of essential genes. Though single chemical or genetic perturbations provide crucial information associating individual components (for example, genes, proteins or small molecules) with pathways or phenotypes, functional relationships between pathways and modules of components are most effectively obtained from combined perturbation experiments. Here we review the current state of and discuss some future directions for ‘combination chemical genetics’, the systematic application of multiple chemical or mixed chemical and genetic perturbations, both to gain insight into biological systems and to facilitate medical discoveries. PMID:18936752

  19. PhD Chemical Engineering MS Chemical Engineering

    E-print Network

    Collins, Gary S.

    1 PhD Chemical Engineering MS Chemical Engineering Bylaws Gene and Linda Voiland School of Chemical Engineering and Bioengineering College of Engineering and Architecture Approved by Voiland School facultyD Chemical Engineering, MS Chemical Engineering B. Discipline: Edgar, et al.1 provide a succinct description

  20. Ultrafast chemical kinetics: Elementary chemical act

    NASA Astrophysics Data System (ADS)

    Bratos, S.; Wulff, M.; Leicknam, J.-Cl.; Kong, Q.

    2015-01-01

    Predictions of the classical theory of chemical reaction rates are compared with experimental results obtained by ultrafast time-resolved X-ray diffraction techniques. Our analysis is illustrated with the reaction I + I = I2 in solution at times immediately preceding recombination. Main features of experimentally detected dynamics are discussed and are compared with what is expected according to Eyring and Kramers. It is emphasized that atomic dynamics are unexpectedly complex at very earliest times.

  1. 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. PMID:16020181

  2. Chemical process hazards analysis

    SciTech Connect

    NONE

    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.

  3. Chemical Patents Plus

    NSDL National Science Digital Library

    Chemical Patents Plus, an information retrieval service provided by Chemical Abstracts, is available via the Web. After registering, interested users can freely search and receive title and abstract information for chemical patents going back to 1971. Other options, such as patent number, front page and all claims, and complete patent, are fee based. The service is available from 6:00 p.m. Sunday through 10:00 p.m. Friday and from 3:00 a.m through 6:00 p.m. Saturday.

  4. Chemical Heritage Foundation

    NSDL National Science Digital Library

    "The Chemical Heritage Foundation (CHF) is dedicated to preserving and sharing the history and heritage of the chemical and molecular sciences, technologies, and allied industries." This Web site illustrates how chemistry has shaped our world. Students can discover the chemical history of Innovations and Industry, Ancients and Alchemists, and much more. Through the Online Exhibits, visitors can view the pictures of Walter J. Hamer's collection of early batteries. In the Classroom Resources, educators will find online tools discussing molecular science and pharmaceutical achievers and many Chemistry Web Quests including Evidence for Atoms and The Great MTBE Controversy. Graduate students may want to take advantage of the many fellowships offered on the site.

  5. 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

  6. Chemical warfare agents.

    PubMed

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

    2010-07-01

    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

  7. Chemical Hygiene Plan i January 2013 Chemical Hygiene Plan

    E-print Network

    Nizkorodov, Sergey

    .......................................................................................9-1 Chapter 10: Accidents and Chemical Spills.........................................................................L-1 Appendix M: Spill Clean-Up Procedures.....................................O-1 Appendix P: Acutely Toxic Chemicals SOP

  8. Endocrine Disrupting Chemicals (EDCs)

    MedlinePLUS

    ... exposure to them. What are the sources of EDCs? Most EDCs are synthetic chemicals designed for use ... endocrine system. How could you be exposed to EDCs? Humans come into contact with EDCs in many ...

  9. 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.

  10. Chemical engineering Research !!

    E-print Network

    hydrolysis Improved fermentation Yeast Fermentation technology Hydrolysis Process integration Consider and yeasts. The project leader is VTT, Finland. The department contribution concerns fermentation technologyChemical engineering Research !! www.chemeng.lth.se Updated August 2012 #12;WWT Fermentation

  11. Chemical and Biochemical

    E-print Network

    Neimark, Alexander V.

    clean drinking water to a village in Kenya, a country experiencing its worst drought in 20 years," said- nology fields where they can test the side effects of antibiotics or develop agricultural chemicals

  12. 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)

  13. Reducing Household Chemical Risks

    NSDL National Science Digital Library

    2011-03-02

    This series of public service videos from the National Institute of Environmental Health Sciences provides quick solutions and action steps to minimize exposure to pesticides, chemical contaminants, and secondhand smoke.

  14. Safer Science: Chemical Storage

    NSDL National Science Digital Library

    Ken Roy

    2009-10-01

    Using chemicals safely requires a number of things, including current inventory control, appropriate labeling and storage segregation, ongoing inspections, and more. How can a science teacher find the appropriate storage information? Read on. This month's

  15. Sawmill chemicals and carcinogenesis.

    PubMed Central

    Huff, J

    2001-01-01

    Workers in wood industries are exposed to variable medleys of chemicals, both natural and synthetic. Additional exposures include fungi, bacteria, bark and wood dusts, solvents, paints, and various other wood coatings. These individual and conglomerate exposures have been associated with diverse occupational illnesses and hazards, including cancers. In this commentary, I summarize both experimental and epidemiologic carcinogenesis results for several chemicals used in the wood industry, as well as for wood dust. Working in the wood industries entails excess risks of cancers, among other diseases and workplace injuries. A key to preventing occupationally and environmentally associated cancers, as in the wood industries, is avoiding exposures to chemicals and wood dusts and, in particular, chemicals known to cause cancer in animals or/and humans. PMID:11333179

  16. Chemical dependence - resources

    MedlinePLUS

    Drug abuse - resources; Resources - chemical dependence ... a good resource for information on drug dependence: Narcotics Anonymous - www.na.org National Council on Alcoholism and Drug Dependence - www.ncadd.org National Institute on Drug Abuse - www.drugabuse.gov

  17. 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)

  18. AGRI-SCIENCE CHEMICAL BIOLOGY

    E-print Network

    photosynthetic efficiency Improve chemical agronomic and agro-ecological control measures ModellingAGRI-SCIENCE CHEMICAL BIOLOGY NETWORK Vehicle for translation: Pioneering a cross-academic, -industry and -government network Chemical Biology Community Agri- Sciences Community Industry Policy makers

  19. Journal of Chemical Education

    NSDL National Science Digital Library

    Published since 1924,the Journal of Chemical Education's mission is to help chemistry teachers stay current with research advances, and to be informed about new ideas in teaching methodologies and course organization. To achieve this mission, JCE online provides a plethora of resources on chemistry and chemical education. JCE's digital library is especially helpful and includes detailed information on molecules, mathematic equations, and much more.

  20. [Cutaneous absorption of chemicals].

    PubMed

    Schröder, J

    1986-09-01

    Chemicals have become indispensible for the maintenance of health in animals and man. The route of administration of each medicament is decided by factors such as site of desired action, chemistry of the active ingredient, age and species of the patient, and frequency of administration (or desired duration of activity). In situations where the oral and hypodermic routes, which are used most frequently, are inadequate or unsatisfactory, dermal application can provide a valuable alternative method to achieve systemic activity. Examples of formulations currently available for dermal application contain diverse chemicals and are intended for a variety of purposes, such as crufomate against cattle grubs, fenthion against cattle lice, levamisole against gastrointestinal nematodes, nitroglycerine for angina pectoris, and scopolamine for motion sickness. The skin acts as a barrier to penetration by chemicals and micro-organisms by virtue of its morphology and chemical composition. Chemicals which do penetrate, do not necessarily pass through the appendages (hair follicles and gland ducts), but mostly penetrate through the interjacent epidermis, either through the cells, or via the intracellular spaces. These spaces have recently been shown by electron microscopy to be filled by an amorphous substance which exudes on the skin surface in convex ridges. This substance has a lipid nature, but is not hydrophobic as is often accepted. For a chemical to be able to penetrate the skin, it must be partially water and lipid soluble, polar, and weakly ionizing. A variety of factors can possibly affect the permeability of skin for a chemical. These include species differences in morphology (skin thickness, tightness of intercellular junctions, density of hair follicles and other appendages), biochemistry, and physiology; seasonal and climatic variations; and differences between breeds and genders. Species differences in skin permeability are largely unpredictable and inconsistent. An observed difference between two species for one chemical cannot necessarily be extrapolated to another.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3543356

  1. Toxic Chemicals Initiative

    NSDL National Science Digital Library

    This World Wildlife Fund initiative is aimed at banning the most deadly, persistent pollutants (such as DDT, PCBs, and dioxins) that endanger every species, ecosystem, and community on Earth. The serious damage to the health of wildlife and humans caused by synthetic chemical contamination is addressed. There are documents about persistent organic pollutants, and endocrine disrupting chemicals. There are also several photographs of polar bears and other animals.

  2. Quality of Chemical Measurements

    NSDL National Science Digital Library

    The International Union of Pure and Applied Chemistry's online newsletter, Chemistry International, posts this article about the problem of wide variation in chemical trace and catalyst measurements. This is important because such data are increasingly used in industry decision-making. In the words of the authors, "This article provides 'snapshot' pictures of chemical measurement (un)reliability, with many practical, societal implications." All text is in HTML.

  3. Quality of Chemical Measurements

    NSDL National Science Digital Library

    1997-01-01

    The International Union of Pure and Applied Chemistry's online newsletter, Chemistry International, posts this article about the problem of wide variation in chemical trace and catalyst measurements. This is important because such data are increasingly used in industry decision-making. In the words of the authors, "This article provides 'snapshot' pictures of chemical measurement (un)reliability, with many practical, societal implications." All text is in HTML.

  4. Rates of Chemical Weathering

    NSDL National Science Digital Library

    Michael Passow

    In this activity, students will investigate the weathering of rocks by chemical processes. They will use effervescent cleansing tablets as a model for rock, and vary surface area, temperature, and acidity to see how rapidly the "rock" dissolves. This investigation will help them understand three of the factors that affect the rate of chemical weathering and develop better understanding of how to design controlled experiments by exploring only one experimental variable at a time.

  5. Integrated Chemical List

    Cancer.gov

    Some Long Island breast cancer advocates, who have been interested in the Long Island Breast Cancer Study Project (LIBCSP), submitted a list of chemicals and other agents of concern to them as possible causes of breast cancer. Many of the agents are already included in the LIBCSP. The table lists both the agents of community interest and those included in the LIBCSP, and is called the Integrated Chemical List.

  6. Chemical and Biological Disarmament

    NSDL National Science Digital Library

    This online directory from the University of Michigan Documents Center provides annotated links to materials related to chemical and biological warfare and disarmament. Included here are resources for background information, related international organizations, and subject-specific sites on chemical and biological warfare, Iraq, peace and conflict studies, as well as pertinent treaties and organizations. The site was created by librarian Susan Wright at the University of Michigan Residential College.

  7. Chemical Communication in Lobsters

    Microsoft Academic Search

    Juan Aggio; Charles D. Derby

    \\u000a Lobsters are fascinating animals that use chemicals as messages regarding their sexual status, their standing in a social\\u000a hierarchy, and whether they affiliate with or avoid conspecifics. This, plus their economic importance, makes them important\\u000a models for the study of intraspecific chemical communication. Our chapter is an overview of these processes, including the\\u000a types of interactions between lobsters influenced by

  8. 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.

  9. 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.

  10. Chemical evolutionary games.

    PubMed

    Aristotelous, Andreas C; Durrett, Richard

    2014-05-01

    Inspired by the use of hybrid cellular automata in modeling cancer, we introduce a generalization of evolutionary games in which cells produce and absorb chemicals, and the chemical concentrations dictate the death rates of cells and their fitnesses. Our long term aim is to understand how the details of the interactions in a system with n species and m chemicals translate into the qualitative behavior of the system. Here, we study two simple 2×2 games with two chemicals and revisit the two and three species versions of the one chemical colicin system studied earlier by Durrett and Levin (1997). We find that in the 2×2 examples, the behavior of our new spatial model can be predicted from that of the mean field differential equation using ideas of Durrett and Levin (1994). However, in the three species colicin model, the system with diffusion does not have the coexistence which occurs in the lattices model in which sites interact with only their nearest neighbors. PMID:24513098

  11. 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.

  12. Chemical inhomogeneities and pulsation

    E-print Network

    S. Turcotte

    2001-11-08

    Major improvements in models of chemically peculiar stars have been achieved in the past few years. With these new models it has been possible to test quantitatively some of the processes involved in the formation of abundance anomalies and their effect on stellar structure. The models of metallic A (Am) stars have shown that a much deeper mixing has to be present to account for observed abundance anomalies. This has implications on their variability, which these models also reproduce qualitatively. These models also have implications for other chemically inhomogeneous stars such as HgMn B stars which are not known to be variable and lambda Bootis stars which can be. The study of the variability of chemically inhomogeneous stars can provide unique information on the dynamic processes occurring in many types of stars in addition to modeling of the evolution of their surface composition.

  13. 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.

  14. Micromachined chemical jet dispenser

    DOEpatents

    Swierkowski, Steve P. (Livermore, CA)

    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.

  15. 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.

  16. Chemically programmed antibodies.

    PubMed

    Rader, Christoph

    2014-04-01

    Due to their unlimited chemical diversity, small molecules can rival monoclonal antibodies (mAbs) with respect to specificity and affinity for target molecules. However, key pharmacological properties of mAbs remain unmatched by small molecules. Chemical programming strategies have been developed for site-specific and covalent conjugation of small molecules to mAbs with unique reactivity centers. In addition to blending favorable features of small molecules and mAbs, chemically programmed antibodies (cpAbs) are economically attractive because they utilize the same mAb for an almost unlimited number of target molecule specificities, reducing manufacturing costs and shortening drug discovery and development time. Preclinical studies and clinical trials have begun to demonstrate the broad utility of cpAbs for the treatment and prevention of human diseases. PMID:24630478

  17. 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 ...

  18. 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…

  19. Precision Chemical Abundance Measurements

    NASA Astrophysics Data System (ADS)

    Yong, David; Grundahl, Frank; Meléndez, Jorge; Norris, John E.

    2015-03-01

    This talk covers preliminary work in which we apply a strictly differential line-by-line chemical abundance analysis to high quality UVES spectra of the globular cluster NGC 6752. We achieve extremely high precision in the measurement of relative abundance ratios. Our results indicate that the observed abundance dispersion exceeds the measurement uncertainties and that many pairs of elements show significant correlations when plotting [X1/H] vs. [X2/H]. Our tentative conclusions are that either NGC 6752 is not chemically homogeneous at the ~=0.03 dex level or the abundance variations and correlations signify star-to-star He abundance variations.

  20. National Historic Chemical Landmarks

    NSDL National Science Digital Library

    The American Chemical Society (ACS) displays the key roles chemists played in "expanding the frontiers of knowledge, advancing medicine and industry, and creating products from aspirin to zippers" at this website. Users can find clear summaries and images of the places, discoveries, and achievements that have been designated landmarks by ACS members and an international committee. Within many of the biographies, educators can find links to teaching guides and activities. Individuals that know of an unrecognized important element of the chemical heritage can learn how to nominate the site, artifact, or collection.

  1. Magnetic chemically peculiar stars

    E-print Network

    Schöller, Markus

    2015-01-01

    Chemically peculiar (CP) stars are main-sequence A and B stars with abnormally strong or weak lines for certain elements. They generally have magnetic fields and all observables tend to vary with the same period. Chemically peculiar stars provide a wealth of information; they are natural atomic and magnetic laboratories. After a brief historical overview, we discuss the general properties of the magnetic fields in CP stars, describe the oblique rotator model, explain the dependence of the magnetic field strength on the rotation, and concentrate at the end on HgMn stars.

  2. Endocrine disrupting chemicals

    PubMed Central

    Yeung, Bonnie HY; Wan, Hin T; Law, Alice YS

    2011-01-01

    In the past 200 years, an enormous number of synthetic chemicals with diverse structural features have been produced for industrial, medical and domestic purposes. These chemicals, originally thought to have little or no biological toxicity, are widely used in our daily lives as well as are commonly present in foods. It was not until the first World Wildlife Federation Wingspread Conference held in 1994 were concerns about the endocrine disrupting (ED) effects of these chemicals articulated. The potential hazardous effects of endocrine disrupting chemicals (EDCs) on human health and ecological well-being are one of the global concerns that affect the health and propagation of human beings. Considerable numbers of studies indicated that endocrine disruption is linked to “the developmental basis of adult disease,” highlighting the significant effects of EDC exposure on a developing organism, leading to the propensity of an individual to develop a disease or dysfunction in later life. In this review, we intend to provide environmental, epidemiological and experimental data to associate pollutant exposure with reproductive disorders, in particular on the development and function of the male reproductive system. Possible effects of pollutant exposure on the processes of embryonic development, like sex determination and masculinization are described. In addition, the effects of pollutant exposure on hypothalamus-pituitary-gonadal axis, testicular signaling, steroidogenesis and spermatogenesis are also discussed. PMID:22319671

  3. STW chemical sensors

    Microsoft Academic Search

    R. L. Baer; C. A. Flory; M. Tom-Moy; D. Solomon

    1992-01-01

    A new kind of chemical sensor which is based on the surface transverse wave (STW) delay line is reported. This sensor is ideally suited to measurements of surface-attached mass under fluid immersion, and it is demonstrated operating under these conditions at 250 MHz. The mass sensitivity of an STW sensor is approximately 10 times greater than that of a thickness

  4. Chemical and biochemical microreactors

    Microsoft Academic Search

    Stephen J Haswell; Victoria Skelton

    2000-01-01

    Research into the fundamental and practical advantages of using micrometre scale reactors for chemical and biochemical applications is now growing at a considerable rate. This review tracks such developments, illustrating their inherent strengths and identifying areas where further development of a technology is poised to revolutionise significant areas of synthetic chemistry and biochemistry.

  5. Guidance Document Reactive Chemicals

    E-print Network

    compounds, shock sensitive materials, organic peroxides, peroxidable chemicals, air-reactive and water-sensitive Materials: Shock-sensitive materials are explosive and are sensitive to heat or shock. Examples include dry picric acid, fulminates, dry benzoyl peroxide, ammonium perchlorate, and compounds with functional groups

  6. 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.

  7. Chemical Engineering Andrew Zydney

    E-print Network

    Maranas, Costas

    Chemistry Medicine Consumer Products SemiconductorsPharmaceuticals Biotechnology Chemical Engineering Fuels;ChE Employment (2003 at PSU) Merck Dow ExxonMob Air Products Amgen PPG Sunoco Kraft Foods NRC Procter and Gamble J&J Shell DuPont Aramco Conoco M&M Mars Grad School Anheuser Busch GlaxoSmith Kline Mixing

  8. 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)

  9. Common Sense and Chemicals

    ERIC Educational Resources Information Center

    Roy, Ken

    2010-01-01

    This month's column features two true stories about the use of chemicals in the middle school science classroom. The lesson of these stories is simple. Certainly, it is prudent to have age-appropriate experiences in science, given the developmental constraints of students in middle school. On the other hand, when the curriculum necessitates…

  10. Safety Issues Chemical Storage

    E-print Network

    Cohen, Robert E.

    acids, e.g. Nitric acid and acetic acid. Oxidizers stored with flammables. Acids stored with bases cabinets. Corrosives (acids and bases) or other liquids stored above eye level. Stock chemicals stored that will be stored in the lab. · Store in groups based on compatibility. · Where possible, use separate cabinets

  11. Rates of Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    1900-01-01

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Chemical Reactions SciPack. It demonstrates

  12. CHEMICAL SIGNALS INVERTEBRATES 4

    E-print Network

    Galef Jr., Bennett G.

    CHEMICAL SIGNALS INVERTEBRATES 4 Ecology, Evolution, and Comparative Biology Edited by David Duvall potential predator, to a promising feeding site (Smythe, 1970); a vulture, descending to scavenge from and Zahavi, 1973), i.e., as aggregation sites at which information concerning current availability of foods

  13. Categorizing Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-07-10

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of four Science Objects in the Chemical Reactions SciPack. It provides an

  14. Chemical genomics in yeast

    PubMed Central

    Brenner, Charles

    2004-01-01

    Many drugs have unknown, controversial or multiple mechanisms of action. Four recent 'chemical genomic' studies, using genome-scale collections of yeast gene deletions that were either arrayed or barcoded, have presented complementary approaches to identifying gene-drug and pathway-drug interactions. PMID:15345040

  15. 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)

  16. Proton Chemical Shifts

    NSDL National Science Digital Library

    Reich, Hans J.

    Created by Hans Reich, professor of organic chemistry at the Uiversity of Wisconsin-Madison, this site contains a compilation of proton chemical shifts and coupling constants. This is an excellent resource for providing students familiarity with Nuclear Magnetic Resonance (NMR) Spectroscopy Data.

  17. Chemical Methods of Control

    NSDL National Science Digital Library

    Fran Slowiczek, Ed.D.

    2009-01-01

    In this lab, learners evaluate the relative effectiveness of various chemical substances (i.e. garlic powder, bathroom cleaner, mouthwash, etc.) as antimicrobial agents. Learners use the agar diffusion method to determine "zones of inhibition." This lesson guide includes background information, questions for learners, and additional activity ideas.

  18. NETL - Chemical Looping Reactor

    ScienceCinema

    None

    2014-06-26

    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.

  19. Chemical properties of mendelevium

    Microsoft Academic Search

    Hulet

    1980-01-01

    Even with the most intense ion beams and the largest available quantities of target isotope, about 10⁶ 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

  20. Green Chemical Processing with

    E-print Network

    Su, Xiao

    (biologics) · Commodity chemicals production ­ 1,3 propanediol, lysine, succinic acid, more · Specialty the industrial applications of protein engineering. #12;Model of primary metabolism #12;Applied optimization Anaplerotic reactions TCA cycle Biosynthesis of serine family amino acids Biosynthesis of alanine family amino

  1. 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.

  2. CHEMICALLY REACTING TURBULENT JETS

    EPA Science Inventory

    The paper reports additional experimental evidence supporting a new description of the mechanism of turbulent entrainment, mixing, and chemical reactions that is emerging from experiments in the last few years which reveal the presence of large scale structures in turbulent shear...

  3. Environmental and chemical carcinogenesis

    Microsoft Academic Search

    Gerald N. Wogana; Stephen S. Hecht; James S. Felton; Allan H. Conney; Lawrence A. Loeb

    2004-01-01

    People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or muta- genic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to

  4. Chemical Zeolites Combinatorial . . .

    E-print Network

    Servatius, Brigitte

    Chemical Zeolites Combinatorial . . . Realization 2d Zeolites Finite Zeolites The Layer . . . Holes in Zeolites Motions Open Problems Home Page Title Page Page 1 of 100 Go Back Full Screen Close Quit ·First ·Prev ·Next ·Last ·Go Back ·Full Screen ·Close ·Quit Combinatorial Zeolites Herman Servatius -- Clark

  5. NETL - Chemical Looping Reactor

    SciTech Connect

    None

    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.

  6. 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…

  7. The newly discovered eclipsing supergiant 22 Vulpeculae

    NASA Technical Reports Server (NTRS)

    Ake, T. B.; Parsons, S. B.; Kondo, Y.

    1985-01-01

    Spectra obtained with the IUE satellite have led to the discovery that 22 Vul is an atmospheric eclipsing binary belonging to the zeta Aurigae class of stars. The system is the first found with a G-type primary (G3 Ib-II), while the spectral type of the secondary is the latest (B9) and its period is the shortest (249 days) of any of the classical members of the group. Out-of-eclipse spectra, atmospheric eclipse phases and totality observations are discussed. Comparisons are made with other systems.

  8. 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.

  9. Supergiant Pulses from Extragalactic Neutron Stars

    E-print Network

    Cordes, J M

    2015-01-01

    We evaluate the hypothesis that extragalactic radio bursts originate from neutron stars. These could be active pulsars or dormant, slowly spinning objects, but the different population distances for these two classes require correspondingly different contributions to burst dispersion measures from any host or intervening galaxies combined with the intergalactic medium. The large, apparent burst rate $\\sim 10^4~$ sky$^{-1}~$ day$^{-1}$ is comparable to the core-collapse supernova rate in a Hubble volume and can be accommodated by a single burst per object in the resulting large reservoir of $\\sim 10^{17}~$ neutron stars. A smaller population distance requires more bursts per object but the likelihood of seeing repeated bursts from any single object is extremely low on human timescales. Gravitational microlensing could play a role for high redshift sources. Extrapolation of the Crab pulsar's giant pulses --- exemplars of coherent, high brightness temperature radiation --- to a rate of one per $10^3~$yr yields a...

  10. The chemical space project.

    PubMed

    Reymond, Jean-Louis

    2015-03-17

    One of the simplest questions that can be asked about molecular diversity is how many organic molecules are possible in total? To answer this question, my research group has computationally enumerated all possible organic molecules up to a certain size to gain an unbiased insight into the entire chemical space. Our latest database, GDB-17, contains 166.4 billion molecules of up to 17 atoms of C, N, O, S, and halogens, by far the largest small molecule database reported to date. Molecules allowed by valency rules but unstable or nonsynthesizable due to strained topologies or reactive functional groups were not considered, which reduced the enumeration by at least 10 orders of magnitude and was essential to arrive at a manageable database size. Despite these restrictions, GDB-17 is highly relevant with respect to known molecules. Beyond enumeration, understanding and exploiting GDBs (generated databases) led us to develop methods for virtual screening and visualization of very large databases in the form of a "periodic system of molecules" comprising six different fingerprint spaces, with web-browsers for nearest neighbor searches, and the MQN- and SMIfp-Mapplet application for exploring color-coded principal component maps of GDB and other large databases. Proof-of-concept applications of GDB for drug discovery were realized by combining virtual screening with chemical synthesis and activity testing for neurotransmitter receptor and transporter ligands. One surprising lesson from using GDB for drug analog searches is the incredible depth of chemical space, that is, the fact that millions of very close analogs of any molecule can be readily identified by nearest-neighbor searches in the MQN-space of the various GDBs. The chemical space project has opened an unprecedented door on chemical diversity. Ongoing and yet unmet challenges concern enumerating molecules beyond 17 atoms and synthesizing GDB molecules with innovative scaffolds and pharmacophores. PMID:25687211

  11. Targeted chemical nucleases

    SciTech Connect

    Sigman, D.S.; Bruice, T.W.; Mazumder, A.; Sutton, C.L. (Univ. of California, Los Angeles (United States))

    1993-03-01

    The design of functional molecules has been an active area of research in chemistry and molecular biology during the past decade, encompassing topics such as host-guest chemistry, ribozymes, catalytic antibodies, and most recently, fullerenes. Nucleolytic agents that cleave the phosphodiester backbone of DNA and RNA have been another important focus of activity. Interest in this subject has paralleled, and relied on, rapid advances in molecular biology, genome mapping and sequencing, and also the chemical synthesis of deoxyoligonucleotides and peptides. The goals of this research, the methodological approaches, and the insights into chemical biology provided by these molecules are the topic of this Account, which emphasizes research with the chemical nuclease activity of 1,10-phenanthroline-copper by the authors laboratory and others but also summarizes the innovative studies of Dervan and colleagues using ferrous-EDTA linked to targeting molecules. Chemical nucleases are defined here as redox active coordination complexes that cleave DNA by an oxidative pathway. The term nuclease is used as a shorthand for nucleolytic activity. Since these reagents are generally used in excess of their substrates and also self-destruct because they generate reactive intermediates, turnover has not been rigorously demonstrated. In addition to 1,10-phenanthroline-copper and ferrous-EDTA, other chelates capable of cleaving the phosphodiester backbone of DNA under physiological conditions include metalloporphyrins, uranyl acetate, and octahedral rhodium complexes. The generation of piperidine sensitive cleavage sites resulting from guanosine oxidation has been achieved with ruthenium and nickel complexes. Chemical methods for cleaving the phosphodiester backbone by hydrolysis or nucleophilic catalysis are not yet efficient enough to be useful. 101 refs., 6 figs.

  12. 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.

  13. 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 contaminated types. ImagesFigs. 1a-c.Fig. 1b.Fig. 1c.Fig. 2.Fig. 3.Fig. 4.Fig. 5.Fig. 6.Fig. 7.Fig. 8.Fig. 9a.Fig. 9B.Fig. 10.Fig. 11.Figs. 12a-c.Fig. 12b.Fig. 12c.Figs. 14a-c.Fig. 14b.Fig. 14c.Figs. 15a-c.Fig. 15b.Fig. 15c. PMID:4606330

  14. INCOMPATIBLE CHEMICAL LIST PRUDENT PRACTICES FOR HANDLING CHEMICALS IN LABORATORIES

    E-print Network

    Cho, Junghyun

    heavy metals Nitrites Acids Nitroparaffins Inorganic bases, amines Oxalic Acid Silver, mercury Oxygen of Incompatible Chemicals CHEMICAL IS INCOMPATIBLE WITH Acetic Acid Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates Acetylene Chlorine, bromine, copper, fluorine

  15. 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)

  16. Chemical and Biological Engineering Department of Chemical and Biological Engineering

    E-print Network

    Heller, Barbara

    Issues Particle Processing Pharmaceutical Engineering Polymer Science and Engineering Process Operation Hybrid Systems Biological Engineering Molecular Modeling Diabetes Biomedical and Pharmaceutical EngineeriChemical and Biological Engineering Department of Chemical and Biological Engineering 127 Perlstein

  17. Industrial chemicals and chemical feedstocks from wood pulping wastewaters

    SciTech Connect

    Compere, A.L.; Griffith, W.L.

    1980-01-01

    A number of industrial chemicals and chemical feedstocks can be made from wood pulping wastewaters by fermentation. The chemicals which can be made include lactic acid, and acrylic acid feedstock; neutral solvents having wide industrial use e.g. butanol, isopropanol, and ethanol; and Kreb's cycle intermediates, which are used as chelating agents and in food additives. The types of wastewaters and conditions required to produce these chemicals will be reviewed.

  18. 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

  19. Chemical Education Digital Library

    NSDL National Science Digital Library

    2013-01-01

    Benzene rings and other aspects of chemistry come alive with these "living textbooks." This collection of key chemistry documents and primers is made possible via the Chemical Education Digital Library (ChemEd DL) and it contains eight separate items. They are called "living" because they are updated by their owners and those responsible for their continued success. Users will find "Practice in Thinking: A Laboratory Course in Introductory Chemistry," "Chemistry Leaflets," and "Wiki: Quantum States of Atoms and Molecules" here for their consideration. The Chemistry Leaflets provide an interesting wrinkle as they were originally published between 1927 and the mid-1940s. Visitors shouldn't miss "Chemical Principles through Integrated Multiple Exemplars (ChemPRIME)" as it is designed so that general chemistry concepts can be presented in an order that reflects the conceptual structure of the discipline.

  20. 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

  1. Chemical Sensing with Nanowires

    NASA Astrophysics Data System (ADS)

    Penner, Reginald M.

    2012-07-01

    Transformational advances in the performance of nanowire-based chemical sensors and biosensors have been achieved over the past two to three years. These advances have arisen from a better understanding of the mechanisms of transduction operating in these devices, innovations in nanowire fabrication, and improved methods for incorporating receptors into or onto nanowires. Nanowire-based biosensors have detected DNA in undiluted physiological saline. For silicon nanowire nucleic acid sensors, higher sensitivities have been obtained by eliminating the passivating oxide layer on the nanowire surface and by substituting uncharged protein nucleic acids for DNA as the capture strands. Biosensors for peptide and protein cancer markers, based on both semiconductor nanowires and nanowires of conductive polymers, have detected these targets at physiologically relevant concentrations in both blood plasma and whole blood. Nanowire chemical sensors have also detected several gases at the parts-per-million level. This review discusses these and other recent advances, concentrating on work published in the past three years.

  2. Chemical Education Xchange

    NSDL National Science Digital Library

    The JCE Chemical Education Exchange serves as the website of the Journal of Chemical Education. It is committed to providing helpful resources for educators working at two-year colleges. In the Navigation area, visitors can get started with their journey through the site by looking over Activities, Blogs, Picks, and Popular Content. The Activities area features dynamic and interactive activities that deal with writing formulas of ionic compounds, the organization of the periodic table, and a fun one that relates the solubility of gas to the boiling of eggs. The Picks area includes thoughtful meditations on thermodynamic sinks, the use of social media in organic chemistry labs, and how to address climate change in the classroom through small discussion groups.

  3. Environmental and chemical carcinogenesis.

    PubMed

    Wogan, Gerald N; Hecht, Stephen S; Felton, James S; Conney, Allan H; Loeb, Lawrence A

    2004-12-01

    People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to environmental chemical carcinogens may contribute significantly to the causation of a sizable fraction, perhaps a majority, of human cancers, when exposures are related to "life-style" factors such as diet, tobacco use, etc. This chapter summarizes several aspects of environmental chemical carcinogenesis that have been extensively studied and illustrates the power of mechanistic investigation combined with molecular epidemiologic approaches in establishing causative linkages between environmental exposures and increased cancer risks. A causative relationship between exposure to aflatoxin, a strongly carcinogenic mold-produced contaminant of dietary staples in Asia and Africa, and elevated risk for primary liver cancer has been demonstrated through the application of well-validated biomarkers in molecular epidemiology. These studies have also identified a striking synergistic interaction between aflatoxin and hepatitis B virus infection in elevating liver cancer risk. Use of tobacco products provides a clear example of cancer causation by a life-style factor involving carcinogen exposure. Tobacco carcinogens and their DNA adducts are central to cancer induction by tobacco products, and the contribution of specific tobacco carcinogens (e.g. PAH and NNK) to tobacco-induced lung cancer, can be evaluated by a weight of evidence approach. Factors considered include presence in tobacco products, carcinogenicity in laboratory animals, human uptake, metabolism and adduct formation, possible role in causing molecular changes in oncogenes or suppressor genes, and other relevant data. This approach can be applied to evaluation of other environmental carcinogens, and the evaluations would be markedly facilitated by prospective epidemiologic studies incorporating phenotypic carcinogen-specific biomarkers. Heterocyclic amines represent an important class of carcinogens in foods. They are mutagens and carcinogens at numerous organ sites in experimental animals, are produced when meats are heated above 180 degrees C for long periods. Four of these compounds can consistently be identified in well-done meat products from the North American diet, and although a causal linkage has not been established, a majority of epidemiology studies have linked consumption of well-done meat products to cancer of the colon, breast and stomach. Studies employing molecular biomarkers suggest that individuals may differ in their susceptibility to these carcinogens, and genetic polymorphisms may contribute to this variability. Heterocyclic amines, like most other chemical carcinogens, are not carcinogenic per se but must be metabolized by a family of cytochrome P450 enzymes to chemically reactive electrophiles prior to reacting with DNA to initiate a carcinogenic response. These same cytochrome P450 enzymes--as well as enzymes that act on the metabolic products of the cytochromes P450 (e.g. glucuronyl transferase, glutathione S-transferase and others)--also metabolize chemicals by inactivation pathways, and the relative amounts of activation and detoxification will determine whether a chemical is carcinogenic. Because both genetic and environmental factors influence the levels of enzymes that metabolically activate and detoxify chemicals, they can also influence carcinogenic risk. Many of the phenotypes of cancer cells can be the result of mutations, i.e., changes in the nucleotide sequence of DNA that accumulate as tumors progress. These can arise as a result of DNA damage or by the incorporation of non-complementary nucleotides during DNA synthetic processes. Based upon the disparity between the infrequency of spontaneous mutations and the large numbers of

  4. Chemical resonant sensors

    NASA Astrophysics Data System (ADS)

    Hauptmann, Peter R.

    1993-03-01

    Resonant sensors designed to have a mechanical resonance frequency are a subject of special practical interest. They are sensors with outputs based on a quasi-digital frequency signal which is a great advantage over conventional analog sensors. Micromachined mechanical resonant sensors can be used to replace conventional piezoresistors in precision sensor applications such as pressure sensors and accelerometers. For the detecting of chemical species, only a part of known resonant sensor principles can be used for practical aims. Ultrasonic sensors can be classified in this category. They include BAW-, SAW-, APM-, and FPW-sensors. The theoretical concepts for their behavior and the advantages and disadvantages in comparison with other chemical sensors are discussed. Experimental results with BAW-sensors for gas and under-liquid sensing are given. Finally, the actual situation in research and industrial application of this sensor class is reviewed.

  5. 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 sources is paramount to success. We are currently working on several processes to produce the propellants that would allow us to visit and explore the surface of Mars. The capabilities currently at our disposal for launching and delivering equipment to another planet or satellite dictate that the size and scale of any hardware must be extremely small. The miniaturization of the processes needed to prepare the in situ propellants and life support commodities is a real challenge. Chemical engineers are faced with the prospect of reproducing an entire production facility in miniature so the complex can be lifted into space and delivered to our destination. Another area that does not normally concern chemical engineers is the extreme physical aspects payloads are subjected to with the launch of a spacecraft. Extreme accelerations followed by the sudden loss of nearly all gravitational forces are well outside normal equipment design conditions. If the equipment cannot survive the overall trip, then it obviously will not be able to yield the needed products upon arrival. These launch constraints must be taken into account. Finally, we must consider both the effectiveness and efficiencies of the processes. A facility located on the Moon or Mars will not have an unlimited supply of power or other ancillary utilities. For a Mars expedition, the available electric power is severely limited. The design of both the processes and the equipment must be considered. With these constraints in mind, only the most efficient designs will be viable. Cryogenics, in situ resource utilization, miniaturization, launchability, and power/process efficiencies are only a few of the areas that chemical engineers provide support and expertise for the exploration of space.

  6. LEGO® Chemical Reactions

    NSDL National Science Digital Library

    Kathleen M. Vandiver, Ph.D.

    2009-01-01

    This activity uses LEGO® bricks to represent atoms bonding into molecules and crystals. The lesson plan is for a 2.5 hour workshop (or four 45-minute classes). There is a "wet lab" chemistry experiment (mixing baking soda and calcium chloride with phenol red indicator), followed by a "LEGO lab" modeling phase that includes writing formulas using chemical notation. This lesson is also offered as a 2.5 hour field trip lesson at the MIT Edgerton Center.

  7. Chemical constituents of Asparagus

    PubMed Central

    Negi, J. S.; Singh, P.; Joshi, G. P.; Rawat, M. S.; Bisht, V. K.

    2010-01-01

    Asparagus species (family Liliaceae) are medicinal plants of temperate Himalayas. They possess a variety of biological properties, such as being antioxidants, immunostimulants, anti-inflammatory, antihepatotoxic, antibacterial, antioxytocic, and reproductive agents. The article briefly reviews the isolated chemical constituents and the biological activities of the plant species. The structural formula of isolated compounds and their distribution in the species studied are also given. PMID:22228964

  8. Chemicals and campesinos

    E-print Network

    Johnson, Roland Hunter

    1993-01-01

    food, primarily bananas, for the United States and other core nations. Chiguita Brands dominates Honduras and is the largest producer and shipper of bananas in the world. The export duty on bananas helps pay Honduran international debt. Exposure... to dangerous chemicals is a grievance in recent labor unrest on banana plantations. Hale sterility, resulting from exposure to 1, 2- dibromo-3-chloropropane (DBCP) as a part of the banana production process, has several social and cultural ramifications...

  9. Chemical Communication in Crayfish

    Microsoft Academic Search

    Thomas Breithaupt

    \\u000a Crayfish are a species rich group of large decapod crustaceans that inhabit freshwater environments. Having served as important\\u000a models for the study of the neural and hormonal control of behavior crayfish were among the first crustacean taxa that were\\u000a reported to use sex pheromones. Decades of research on crayfish chemical communication have, after initial controversies,\\u000a now generated a comprehensive picture

  10. All about Chemical Bonding

    NSDL National Science Digital Library

    Lower, Stephen

    Stephen Lower, a retired professor at Simon Fraser University, created this expansive and instructive website as a supplement to formal chemistry education for undergraduate students. Visitors will find in-depth descriptions along with several diagrams dealing with chemical bonding issues including their properties, shared-electron covalent bonds, hybrid orbitals, coordination complexes, and metals and semiconductors. General chemistry students looking for assistance should visit this well-developed educational site.

  11. 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.

  12. 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.

  13. Chemical Biology Chemical Screening for Hair Cell Loss and Protection

    E-print Network

    Rubel, Edwin

    Chemical Biology Chemical Screening for Hair Cell Loss and Protection in the Zebrafish Lateral Line Rubel,1,2 and David W. Raible1,4 Abstract In humans, most hearing loss results from death of hair cells of mechanosensory hair cells. We discuss chemical screens to identify compounds that induce hair cell loss

  14. Chemical Soil Physics Phenomena for Chemical Sensing of Buried UXO

    Microsoft Academic Search

    James Phelan; Stephen W. Webb

    1999-01-01

    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.

  15. Appendix B: Chemicals Appendix B: Chemicals B-3

    E-print Network

    Pennycook, Steve

    of chemicals, we can increase food production, cure diseases, build more efficient houses, and send people of metals such as selenium, arsenic, or molybdenum, which may be hazardous to humans or animals. However health. Not all chemicals are toxic: every day we ingest chemicals in the form of food, water

  16. The Chemical Scorecard

    NSDL National Science Digital Library

    An information service provided by the Environmental Defense Fund, The Chemical Scorecard allows the general population easy access to the Environmental Protection Agency's (EPA) Toxic Release Inventory (TRI). The TRI is a compilation of all self-reported releases of toxic substances into the environment. Visitors can search for pollution reports via a map interface or by specifying the desired state. Reports are available for states, counties, cities, and companies. Each report includes maps of manufacturing facilities, chemical releases or waste generation for 1995, TRI pollution releases and data summaries. At the end of each report, visitors are provided with ways to voice their concern about toxic releases. In addition to the reports, the Scorecard contains rankings of toxic releases by state, county, zip code, and facility. The rankings are ordered based on a variety of criteria, including carcinogens, different toxicants, and cancer and non-cancer hazards. The Scorecard also provides information on over 5,000 chemicals included in the TRI, their health effects, and a glossary of commonly used terminology.

  17. Chemical Industry Archives

    NSDL National Science Digital Library

    In March 2001, PBS aired a disturbing two-hour special hosted by Bill Moyers that explores the history of the chemical revolution of the past 50 years and how companies have long sought to withhold information from the public and their employees about the safety of many substances. The program draws on a large collection of previously secret industry documents unearthed during a ten-year lawsuit by the family of a man who died from a rare brain cancer after working at a vinyl-chloride plant. The family's lawyer eventually charged all vinyl-chloride-producing companies with conspiracy, and the discovery process brought to light hundreds of thousands of pages of documents which reveal a closely planned and well-executed campaign to limit regulation of toxic chemicals and the liability of manufacturers and to withhold important health information from all parties. A large selection of these internal documents, over 37,000 pages, is available at the Chemical Industry Archives, created by the Environmental Working Group. The site offers several essays on the archive and the industry, including a selection of some egregious examples of companies hiding or denying known health risks of their products. The archive itself may be searched by keyword with several modifiers. The documents are presented in .pdf format. This site is sure to become an extremely important resource for health activists, journalists, and the concerned public.

  18. 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.

  19. Chemical hazards in radiology.

    PubMed

    Byrns, G E; Palatianos, K H; Shands, L A; Fennelley, K P; McCammon, C S; Boudreau, A Y; Breysse, P N; Mitchell, C S

    2000-02-01

    A variety of chemicals are used in medical imaging as developer and fixer ingredients, germicides, and cleaning agents. Glutaraldehyde, a potent sensitizer, may cause occupational skin and respiratory diseases in exposed individuals. Poor ventilation, unsafe practices, and lack of hazard recognition may contribute to occupational asthma and other respiratory disease in susceptible medical imaging personnel. Failure to respond effectively to initial health complaints and reduce exposure levels can have serious consequences for affected employees. It is therefore important for occupational safety and health professionals to alert health facility managers to potential dangers and to recommend effective intervention strategies. When problems are identified, a multidisciplinary team approach is the best method for evaluating and controlling hazards. This team should include industrial hygienists, safety staff, occupational medicine physicians, mechanical and ventilation engineers, personnel specialists, and medical imaging staff. A thorough hazard assessment, medical diagnosis, and administrative personnel actions are critical to effective problem identification and correction. In the case of chemical sensitization, removal of the affected employee may be necessary. By working with designers and equipment installers to monitor compliance with appropriate codes and manufacturers' specifications, hazards can be prevented. We present additional operations, ventilation, and design improvements to reduce chemical exposures to radiology employees. PMID:10675978

  20. 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.

  1. 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.

  2. Chemical & Engineering News

    NSDL National Science Digital Library

    The American Chemical Society produces the weekly magazine "Chemical & Engineering News" which reports on topics ranging from business to government to education drawn from across the world of chemistry. Although much of the content on the website is password-protected for those with a subscription to the magazine, the fascinating "Multimedia" section of the website is accessible to all visitors. The "Latest Photo Galleries" section has the must see gallery "Another Kind of Landscape" from May 2, 2011, which is about a new book on environmental degradation. There are just five photos, all aerial views, that at first blush look beautiful and like works of art, but upon reading the caption, visitors will learn that the photos are of the run-off from a fertilizer plant, an aluminum producer, and a coal mine. The enlightening and interactive article from June 2007 (under "Other Multimedia") titled "The Incredible Vastness of Data lets visitors visualize the differences between chemical research conducted in 1907 and 2007. Overall, the multimedia has much to offer and warrants several return visits.

  3. 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.

  4. 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.

  5. 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.

  6. ChemTeacher: Chemical Changes

    NSDL National Science Digital Library

    2011-01-01

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Chemical Changes page includes resources for teaching students about properties and examples of chemical changes.

  7. 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.

  8. Chemical Agents: Facts about Evacuation

    MedlinePLUS

    ... Public Health Matters What's New A - Z Index Chemical Agents: Facts About Evacuation Language: English Español (Spanish) ... on Facebook Tweet Share Compartir Some kinds of chemical accidents or attacks, such as a train derailment ...

  9. 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)

  10. or ChemiCal engineering?

    E-print Network

    Wagner, Stephan

    for plant cultures or using bacteria to extract minerals from their ores. Another frontier for the chemical. The chemists and the chemical engineer often form a close-knit team. The engineer takes over after the chemist

  11. 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.

  12. Physical and Chemical Changes Paper

    NSDL National Science Digital Library

    Mr. Wall

    2008-10-28

    In this activity you will write a paper explaining Physical and Chemical Changes. Follow the instructions below to show what you know about Physical and Chemical Changes. Create a word document titled "Physical and Chemical Changes". Put a heading on it that includes your name, number, date, and class period in the upper right corner. Your document should be double spaced, 12 point Times ...

  13. Chemical Kinetics: Rate of Reaction

    NSDL National Science Digital Library

    David N. Blauch

    This site offers an interactive tutorial that emphasizes graphical interpretation of chemical kinetics. The stoichiometric coefficients for a chemical equation are determined by comparing the slopes of concentration-time plots for the reactants and products. This tutorial is coupled to others to further guide the student to a better understanding of chemical kinetics.

  14. 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…

  15. ANALYTICAL METHODS in CHEMICAL ECOLOGY

    E-print Network

    ANALYTICAL METHODS in CHEMICAL ECOLOGY a post graduate course (doktorandkurs) when: February 10 ­ 28, 2014 where: Chemical Ecology, Plant Protection Biology, Swedish University of Agriculture (SLU to modern analytical methods used in Chemical Ecological and Ecotoxicological research, such as: methods

  16. 48 Chemical Engineering Education Incorporating

    E-print Network

    Hesketh, Robert

    these to fields such as specialty chemical manufacture, green engineering, bio/pharmaceutical manufac- ture48 Chemical Engineering Education Incorporating GREEN ENGINEERING Into a Material and Energy prob- lems in chemical engineering. Problems of the type that can be used to motivate the student

  17. 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

  18. High energy chemical laser system

    Microsoft Academic Search

    D. W. Gregg; R. K. Pearson

    1975-01-01

    A high energy chemical laser system is described wherein explosive ; gaseous mixtures of a reducing agent providing hydrogen isotopes and interhalogen ; compounds are uniformly ignited by means of an electrical discharge, flash-; photolysis or an electron beam. The resulting chemical explosion pumps a lasing ; chemical species, hydrogen fluoride or deuterium fluoride which is formed in the ;

  19. 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 described in the…

  20. 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 ketones,…

  1. 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)

  2. Chemical Aspects of Machining Processes

    Microsoft Academic Search

    E. Brinksmeier; D. A. Lucca; A. Walter

    2004-01-01

    Machining processes used to create surfaces are influenced by the mechanical, thermal, and chemical loading in the contact zone. In addition, the tribo-physical and tribo-chemical interactions between the cutting tool, workpiece, metalworking fluid and surrounding medium have an influence on the properties of the resulting surface. In order to design efficient machining processes and control the chemical state of the

  3. Chemical xenogenization of experimental tumors

    Microsoft Academic Search

    Paolo Puccetti; Luigina Romani; Maria C. Fioretti

    1987-01-01

    Chemical xenogenization occurs when experimental tumors, treated in vivo or in vitro with selected chemicals, become immunogenic, i.e., able to induce a strong rejection response, immunological in nature, in the histocompatible hosts. Unlike modifications induced by haptens, changes in tumor cell immunogenicity associated with chemical xenogenization are heritable as a result of drug interfence with the genetic code. Drugs endowed

  4. Green chemistry for chemical synthesis

    Microsoft Academic Search

    Chao-Jun Li; Barry M. Trost

    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.

  5. Adapting Chemical Mixture Risk Assessment Methods to Assess Chemical and Non-Chemical Stressor Combinations

    EPA Science Inventory

    Presentation based on the following abstract: Chemical mixtures risk assessment methods are routinely used. To address combined chemical and nonchemical stressors, component-based approaches may be applicable, depending on the toxic action among diverse stressors. Such methods a...

  6. Chemical Health and Safety Data

    NSDL National Science Digital Library

    These Chemical Health and Safety Data are an excellent resource for reliable, no-frills information from the National Toxicology Program (NTP). Data from "over 2000 chemicals studied by the NTP" are made available here, and users have a couple of different options for retrieving information. They may simply view a list of chemicals or search the Health and Safety database. Information on each chemical includes physical chemical data (like solubilities, solvents, volatility, flammability, and reactivity), toxicity data, handling procedures, emergency procedures, and a bibliographic list of sources for the information collected. Archived data may be downloaded (.sea, .zip).

  7. Chemical sensing flow probe

    DOEpatents

    Laguna, George R. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Butler, Michael A. (Albuquerque, NM)

    1999-01-01

    A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the analyte or result in significant regent contamination of the analyte reservoir.

  8. Chemical kinetics modeling

    SciTech Connect

    Westbrook, C.K.; Pitz, W.J. [Lawrence Livermore National Laboratory, CA (United States)

    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.

  9. Chemical sensing flow probe

    DOEpatents

    Laguna, G.R.; Peter, F.J.; Butler, M.A.

    1999-02-16

    A new chemical probe determines the properties of an analyte using the light absorption of the products of a reagent/analyte reaction. The probe places a small reaction volume in contact with a large analyte volume. Analyte diffuses into the reaction volume. Reagent is selectively supplied to the reaction volume. The light absorption of the reaction in the reaction volume indicates properties of the original analyte. The probe is suitable for repeated use in remote or hostile environments. It does not require physical sampling of the analyte or result in significant regent contamination of the analyte reservoir. 7 figs.

  10. Chemical Weathering of Limestone

    NSDL National Science Digital Library

    This activity demonstrates the chemical attack on limestone by rain that is naturally acidic (containing dissolved carbon dioxide) and acid rain (rain that is more acidic because of dissolved pollutants such as sulfur dioxide and nitrogen oxides). Students will blow through a straw into water containing a Universal Indicator and note that the water becomes slightly acidic because carbon dioxide from their breath dissolves in it. They then add limestone chips to the water and note that the solution gradually becomes neutral as the calcium carbonate in the chips reacts with the acid. The site also has instructions for teacher and students, a list of materials, questions to answer, and a glossary.

  11. Chemically rechargeable battery

    NASA Technical Reports Server (NTRS)

    Graf, James E. (Inventor); Rowlette, John J. (Inventor)

    1984-01-01

    Batteries (50) containing oxidized, discharged metal electrodes such as an iron-air battery are charged by removing and storing electrolyte in a reservoir (98), pumping fluid reductant such as formalin (aqueous formaldehyde) from a storage tank (106) into the battery in contact with the surfaces of the electrodes. After sufficient iron hydroxide has been reduced to iron, the spent reductant is drained, the electrodes rinsed with water from rinse tank (102) and then the electrolyte in the reservoir (106) is returned to the battery. The battery can be slowly electrically charged when in overnight storage but can be quickly charged in about 10 minutes by the chemical procedure of the invention.

  12. 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.

  13. Chemical sensor system

    DOEpatents

    Darrow, Christopher B. (Pleasanton, CA); Satcher, Jr., Joe H. (Modesto, CA); Lane, Stephen M. (Oakland, CA); Lee, Abraham P. (Walnut Creek, CA); Wang, Amy W. (Berkeley, CA)

    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.

  14. [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. PMID:15773297

  15. Natural chemicals, synthetic chemicals, risk assessment, and cancer

    SciTech Connect

    Ames, B.N.; Gold, L.S. (Division of Biochemistry and Molecular Biology, University of California, Berkeley (United States))

    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.

  16. 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).

  17. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A. [GAB Consulting Pty Ltd, 144/110 Sussex Street, Sydney NSW 2000 (Australia)

    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.

  18. 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.

  19. Chemical heat pump

    DOEpatents

    Greiner, Leonard (2853-A Hickory Pl., Costa Mesa, CA 92626)

    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.

  20. Chemical heat pump

    DOEpatents

    Greiner, Leonard (2853-A Hickory Pl., Costa Mesa, CA 92626)

    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.

  1. Chemical heat pump

    DOEpatents

    Greiner, Leonard (2853-A Hickory Pl., Costa Mesa, CA 92626)

    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.

  2. Chemical heat pump

    DOEpatents

    Greiner, Leonard (2853-A Hickory Pl., Costa Mesa, CA 92626)

    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.

  3. Chemical synthesis of saponins.

    PubMed

    Yang, You; Laval, Stephane; Yu, Biao

    2014-01-01

    Saponins are a large family of amphiphilic glycosides of steroids and triterpenes found in plants and some marine organisms. By expressing a large diversity of structures on both sugar chains and aglycones, saponins exhibit a wide range of biological and pharmacological properties and serve as major active principles in folk medicines, especially in traditional Chinese medicines. Isolation of saponins from natural sources is usually a formidable task due to the microheterogeneity of saponins in Nature. Chemical synthesis can provide access to large amounts of natural saponins as well as congeners for understanding their structure-activity relationships and mechanisms of action. This article presents a comprehensive account on chemical synthesis of saponins. First highlighted are general considerations on saponin synthesis, including preparation of aglycones and carbohydrate building blocks, assembly strategies, and protecting-group strategies. Next described is the state of the art in the synthesis of each type of saponins, with an emphasis on those representative saponins having sophisticated structures and potent biological activities. PMID:25480505

  4. Aqueous chemical wash compositions

    SciTech Connect

    Bannister, C.E.

    1987-07-21

    This patent describes an aqueous, substantially unfoamed chemical wash composition having properties making it suitable for use as a pre-flush in well cementing operations and/or for removal of drilling mud from a borehole at a temperature of from about 150/sup 0/F to about 270/sup 0/F, the wash a. being predominantly composed of water, b. containing an active surfactant component comprising a combination of (1) from about 0.1 to about 1.5 weight percent (total weight basis) of a water soluble anionic surfactant; (2) from about 0.1 to about 1.5 weight percent (total weight basis) of a nonionic surfactant; and (3) from about 0.05 to about 0.54 weight percent (total weight basis) of at least one water soluble amphoteric surfactant, and c. having dispersed therein a heterogeneous mixture of distinct particles comprising both a first particulate oil soluble resin which is friable and a second particulate oil soluble resin which is pliable and where the size of the friable resin particles ranges from about 0.5 to about 300 microns and the size of the pliable resin particles ranges from about 0.05 to about 30 microns. The amount of the friable-pliable resin mixture is sufficient to impart effective fluid loss control to the chemical wash composition.

  5. Selective chemical stripping

    NASA Astrophysics Data System (ADS)

    Malavallon, Olivier

    1995-04-01

    At the end of the 80's, some of the large European airlines expressed a wish for paint systems with improved strippability on their aircraft, allowing the possibility to strip down to the primer without altering it, using 'mild' chemical strippers based on methylene chloride. These improvements were initially intended to reduce costs and stripping cycle times while facilitating rapid repainting, and this without the need to change the conventionally used industrial facilities. The level of in-service performance of these paint systems was to be the same as the previous ones. Requirements related to hygiene safety and the environment were added to these initial requirements. To meet customers' expectations, Aerospatiale, within the Airbus Industry GIE, formed a work group. This group was given the task of specifying, following up the elaboration and qualifying the paint systems allowing requirements to be met, in relation with the paint suppliers and the airlines. The analysis made in this report showed the interest of transferring as far upstream as possible (to paint conception level) most of the technical constraints related to stripping. Thus, the concept retained for the paint system, allowing selective chemical stripping, is a 3-coat system with characteristics as near as possible to the previously used paints.

  6. Recover chemicals from wastewater

    SciTech Connect

    NONE

    1995-01-01

    For years, solution mining near Prague in the Czech Republic has produced acid-laden wastewater, which has accumulated in deep underground caverns. Over the years, this acid waste has spread into a large underground reservoir, which today threatens the aquifer that supplies drinking water to Prague, about 70 miles south of the mine. Later this year, a two-pronged site cleanup will be carried out by Resources Conservation Co. International (RCCI), a subsidiary of Ionics, Inc. (Watertown, Mass.). First, the acid water will be pumped to the surface. Then, the stream, which contains sulfuric acid and aluminum ammonium sulfate (ammonium alum) will undergo evaporation and crystallization to recover the ammonium alum, a widely used water-treatment chemical, and fresh water for reuse.

  7. Chemical Equilibrium Detonation

    NASA Astrophysics Data System (ADS)

    Bastea, Sorin; Fried, Laurence E.

    Energetic materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. The fundamental principles outlined in this chapter pertain to the study of detonation in both gas-phase and condensed-phase energetic materials, but our main focus will be on the condensed ones, particularly on high explosives (HEs). They share many properties with other classes of condensed energetic compounds such as propellants and pyrotechnics, but a detailed understanding of detonation is especially important for numerous HE applications. The usage and study of HE materials goes back more than a century, but many questions remain to be answered, e.g., on their reaction pathways at high pressures and temperatures, chemical properties, etc.

  8. 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.

  9. Biological and Chemical Weapons

    NSDL National Science Digital Library

    One of the latest in MEDLINEplus' special collections, the Biological and Chemical Weapons page addresses health issues at the forefront of many people's minds these days. As with other MEDLINEplus special collections, this page offers links to news stories, sites providing general information and overviews, information about specific conditions, and relevant organizations. While the sites are not annotated, the page provides a useful introduction to these health issues. The links here are all authoritative and range from the National Center for Infectious Diseases' (NCID) faq on anthrax to Johns Hopkins University's Center for Civilian Biodefense Studies to National Library of Medicine's TOXNET Databases. MEDLINEplus is offered by the National Library of Medicine (NLM) and was last mentioned in the April 14, 2000 Scout Report.

  10. The brassinosteroid chemical toolbox.

    PubMed

    Dejonghe, Wim; Mishev, Kiril; Russinova, Eugenia

    2014-12-01

    Chemical biology approaches have been instrumental in understanding the mode of action of brassinosteroids, a group of plant steroid hormones essential for plant development and growth. The small molecules used for such approaches include inhibitors of biosynthetic enzymes and signaling components. Additionally, recent structural data on the brassinosteroid receptor complex together with its ligand brassinolide, the most active brassinosteroid, and knowledge on its different analogs have given us a better view on the recognition of the hormone and signaling initiation. Moreover, a fluorescently labeled brassinosteroid enabled the visualization of the receptor-ligand pair in the cell. Given the insights obtained, small molecules will continue to provide new opportunities for probing brassinosteroid biosynthesis and for unraveling the dynamic and highly interconnected signaling. PMID:25282585

  11. Chemical Comic Relief

    NSDL National Science Digital Library

    John Selegue and James Holler at the University of Kentucky have provided this ingenious learning resource, Chemical Comic Relief. Visitors to the site click on an element on the periodic table to see a list of comic pages involving that element. For example, clicking on Oxygen brings up a list of comics including Four Color: Ricky Nelson, which shows Ricky discussing oxygen to attempt (unsuccessfully) to impress a girl. Some pages include a summary discussing both the comic as well as the element it features, and the site also offers a chronological History of Chemistry in the Comics -- an album of comic pages from the 1930s to the present. To gain a greater understanding of the technical aspects (atomic weight, key data and description, and history) of each element, the user can link to the WebElements Website.

  12. 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.

  13. 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.

  14. JCE Chemical Education Xchange

    NSDL National Science Digital Library

    The JCE Chemical Education Exchange offers a range of videos designed for educators and the curious public. Created as part of the larger ChemEd Exchange website, videos include "Boiling by Cooling,� "Atmosphere Pressure,� "Ammonia Fountain,� and "Canned Heat.� All told, the website hosts over 280 videos and several dozen are available at no charge. Visitors can use the search engine on the top of the page for specific content or browse around at their leisure. A list of related blogs and relevant blog topics, such as Lego Periodic Table, can also be found on this site. It is a great resource to get the creative juices flowing in regard to chemistry education.

  15. Chemical heat pump

    DOEpatents

    Greiner, Leonard (2750-C Segerstrom Ave., Santa Ana, CA 92704)

    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.

  16. The unfought chemical war

    SciTech Connect

    Freeman, K. (Pennsylvania State Univ., University Park (United States))

    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.

  17. 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 +/.

  18. Chemical substructure analysis in toxicology

    SciTech Connect

    Beauchamp, R.O. Jr. [Center for Information on Toxicology and Environment, Raleigh, NC (United States)

    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.

  19. ELECTRICAL AND CHEMICAL CHARACTERIZATION OF CHEMICALLY PASSIVATED SILICON SURFACES

    E-print Network

    Honsberg, Christiana

    is investigated using XPS and FTIR techniques. The samples are passivated with methanol, quinhydrone passivated silicon substrates are also measured. Quinhydrone-methanol solution provides a chemically inert important. Chemical passivation using iodine-methanol and quinhydrone-methanol has been used previously

  20. 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

  1. Environmental chemicals, respiratory hypersensitization and international chemical safety

    Microsoft Academic Search

    Edward Smith

    1996-01-01

    Allergic hypersensitization to a variety of chemicals, natural and synthetic, is a worldwide health problem. Respiratory tract hypersensitization is responsible for significant morbidity and, in some cases, mortality. An important step in managing and controlling health risks, such as allergic hypersensitization, is to identify the chemical hazard, define dose-effect and dose-response relationships, evaluate exposure, and characterize risk. In practical terms,

  2. 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 sources of…

  3. Chemical abundances of M giants in the Galactic centre: A single metal-rich population with low [?/Fe

    NASA Astrophysics Data System (ADS)

    Ryde, N.; Schultheis, M.

    2015-01-01

    Context. The formation and evolution of the Milky Way bulge is still largely an unanswered question. Some of the most essential observations needed for its modelling are the metallicity distribution and the trends of the ? elements, as measured in stars. While bulge regions beyond R ? 50 pc of the centre have been targeted in several surveys, the central part has escaped a detailed study due to the extreme extinction and crowding. The abundance gradients from the centre are, however, of large diagnostic value. Aims: We aim at investigating the Galactic centre environment by probing M giants in the field by avoiding supergiants and cluster members. Methods: For nine field M-giants in the Galactic centre region, we have obtained high- and low-resolution spectra observed simultaneously with CRIRES and ISAAC on UT1 and UT3 of the VLT. The low-resolution spectra provide a means of determining the effective temperatures, and the high-resolution spectra provide detailed abundances of Fe, Mg, Si, and Ca. Results: We find a metal-rich population at [ Fe / H ] = + 0.11 ± 0.15 and a lack of the metal-poor population, which is found further out in the bulge, corroborating earlier studies. Our [?/Fe] element trends, however, show low values, by following the outer bulge trends. A possible exception of the [Ca/Fe] trend is found and needs further investigation. Conclusions: The results of the analysed field M-giants in the Galactic centre region exclude a scenario with rapid formation, in which SNIIe played a dominated role in the chemical enrichment of the gas. The high metallicities with low ?-enhancement seems to indicate a bar-like population that is, perhaps, related to the nuclear bar. Based on observations collected at the European Southern Observatory, Chile, program number 089.B-0312(A)/VM/CRIRES and 089.B-0312(B)/VM/ISAAC.Figures 8 and 9 are available in electronic form at http://www.aanda.org

  4. 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.

  5. 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.

  6. 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.

  7. Chemical approaches to artificial photosynthesis

    Microsoft Academic Search

    Thomas J. Meyer

    1989-01-01

    In artificial photosynthesis, the goal is to mimic the ability of green plants and other photosynthetic organisms in their use of sunlight to make high-energy chemicals. This is a difficult problem chemically, which accounts for much of the complexity of the natural photosynthetic apparatus. Nonetheless, a number of promising approaches have appeared in recent years based on semiconductors, membranes, vesicles,

  8. 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…

  9. Career Choices for Chemical Engineers

    NSDL National Science Digital Library

    1997-01-01

    The American Institute of Chemical Engineers has recently added a new feature, Career Choices for Chemical Engineers, to their Website. The AIChE Career Services sections provide a listing of job openings in academia and industry under the Employers section. In addition, this page includes sections that publish information on job searches, salary surveys, and career fairs.

  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. Job Prospects for Chemical Engineers.

    ERIC Educational Resources Information Center

    Basta, Nicholas

    1985-01-01

    After several lean years, chemical engineering (a popular discipline among women) is witnessing a higher job demand for new graduates. Companies show a trend toward specialty chemicals with resultant needs for more engineering talent. Other opportunities in the field include agriculture and food processing, environmental control, biotechnology,…

  12. 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…

  13. 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…

  14. 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…

  15. Chemical Evolution in Omega Centauri

    E-print Network

    Verne V. Smith

    2003-10-22

    The globular cluster Omega Centauri displays evidence of a complex star formation history and peculiar internal chemical evolution, setting it apart from essentially all other globular clusters of the Milky Way. In this review we discuss the nature of the chemical evolution that has occurred within Omega Cen and attempt to construct a simple scenario to explain its chemistry.

  16. Where chemical EOR stands today

    Microsoft Academic Search

    Hause

    1981-01-01

    Two major factors that stand in the way of chemical recovery of residual oil left in a reservoir after waterflooding are the high cost of efficient processes and reservoir heterogeneity. Under present economic conditions, it appears that chemical enhanced oil recovery (EOR) processes are only marginally profitable when applied under true tertiary conditions. These same processes can be more profitable

  17. Safety in the Chemical Laboratory

    ERIC Educational Resources Information Center

    Coffee, Robert D.

    1972-01-01

    The author discusses a system for establishing the relative potential of a chemical to release energy suddenly and to indicate release. This system is applicable to chemical storage and transportation. The system is based upon three simple tests requiring a minimum sample (1 go or 1 ml): (1) computation, (2) impact sensitivity, and (3) thermal…

  18. Chemical hazards in the organisation.

    PubMed

    Winder, Chris

    2012-01-01

    The use of hazardous chemicals in organisations represents a substantial risk to occupational health, safety and the environment (OHSE). Organisational directors and managers have a responsibility to provide and maintain organisational management systems that manage these risks. The risk management approach of establishing organisational considerations, identifying chemical hazards (health and environmental), assessing and controlling risks and evaluating management activities has become the de facto means of managing organisational hazards in general and may be satisfactorily applied to the management of chemicals in the organisation. The Globally Harmonized System for the Classification and Labelling of Chemicals (GHS) is now at the forefront of major regulatory issues facing the chemicals manufacturing industry and downstream users of chemicals. The GHS offers one system for the classification of all dangerous, toxic and environmental (ecotoxic) effects of chemicals. Organisations should develop occupational health, safety and environment (OHSE) management systems which contain programs and procedures that contain systems for inventory control, hazard communication, competency training, risk assessment and control, transport and storage, monitoring and health surveillance, chemical emergencies (including accident investigation), waste minimisation and disposal, record keeping and management system review. PMID:22945564

  19. 4, 19111940, 2004 Chemical ozone

    E-print Network

    Paris-Sud XI, Université de

    ACPD 4, 1911­1940, 2004 Chemical ozone depletion in the 1999/2000 Arctic polar vortex prior-latitudes of chemical ozone depletion in the 1999/2000 Arctic polar vortex prior to the vortex breakup G. Koch 1 , H in the 1999/2000 Arctic polar vortex prior to the vortex breakup G. Koch et al. Title Page Abstract

  20. Clare Reimers Professor, Chemical Oceanography

    E-print Network

    Kurapov, Alexander

    Clare Reimers Professor, Chemical Oceanography Clare Reimers, Professor of Chemical Oceanography research, education and outreach in fields including geology, oceanography, atmospheric sciences, volcanism in 1976 from the University of Virginia. She received an MS in Oceanography in 1978 and a PhD in 1982 from