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Sample records for tepid supergiants chemical

  1. Cool giants and supergiants as probes of the chemical evolution of the Milky Way

    NASA Astrophysics Data System (ADS)

    Origlia, Livia

    2015-08-01

    Evolved, cool giant and supergiant stars are among the brightest populations in any stellar system and easily observable out to large distances, especially at infrared wavelengths.These stars also dominate the integrated light of star clusters in a wide range of ages, making them powerful tracers of stellar populations in more distant galaxies.The current generation of medium-high resolution spectrographs in the optical and near IR with high throughput has allowed to get accurate abundances of the most important metals in giants and supergiants, also in high reddened environments like the inner Galaxy disk and bulge and the Galactic center.In this talk I will review some of the most important results obtained so far in tracing the chemical evolution of the inner Galaxy and future perspectives with the next generation of telescopes and instrumentation.

  2. Chemical Abundances and the Evolutionary Status of 22 Galactic A-type Supergiants

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.

    1996-03-01

    The A-type supergiants have an interesting location on the HR-diagram for testing stellar evolution theories since various evolution scenarios describe vastly different histories for these stars. In particular, the predicted abundances of carbon and nitrogen in the stellar atmospheres differ significantly since these stars may have evolved directly from the main-sequence or may be returning from the red giant branch where they would undergo the first dredge-up of CN-cycled H-burned gas from the stellar interior. This thesis provides new elemental abundances for a large group of Galactic A-type supergiants in the 5 to 20 solar mass range, while also addressing the difficulties in determining reliable abundances in these stars. The atmospheric analysis of each star was performed using the most recent Kurucz LTE model atmospheres. Atmospheric parameters (Teff and log g) have been determined from ionization equilibrium of weak Mg I and Mg II lines and fitting the wings of the H-gamma line profiles; the final parameters were chosen at the intersection of the loci of possible Teff-gravity values from each indicator. Calculations show that NLTE effects on the weak Mg I and Mg II spectral lines used in this analysis are small, therefore they are ideal atmospheric parameter indicators. The metal abundances, log epsilon (O, Mg, Si, Ca, Sc, Ti, Cr, Fe, Ni) are solar to within about $\\pm$0.2~dex, calculated assuming LTE. Overabundances of Na are found, which are discussed as a combination of possible NLTE effects and/or pollution of newly synthesized Na from a NeNa proton capture reaction that could occur in the stellar core. Otherwise, we see no evidence of slight overall metal enrichments in these young stars that might be expected due to Galactic chemical evolution. More details of the atmospheric and LTE metal abundance analyses can be found in Venn 1994 (ApJS, 99, 659). The carbon and nitrogen abundances are examined in order to study the evolutionary status of these

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Molina, R. E.; Rivera, H.

    2016-04-01

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

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

    SciTech Connect

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

    2009-05-10

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

  6. In tepid defense of population health: physicians and antibiotic resistance.

    PubMed

    Saver, Richard S

    2008-01-01

    Antibiotic resistance menaces the population as a dire public health threat and costly social problem. Recent proposals to combat antibiotic resistance focus to a large degree on supply side approaches. Suggestions include tinkering with patent rights so that pharmaceutical companies have greater incentives to discover novel antibiotics as well as to resist overselling their newer drugs already on market. This Article argues that a primarily supply side emphasis unfortunately detracts attention from physicians' important demand side influences. Physicians have a vital and unavoidably necessary role to play in ensuring socially optimal access to antibiotics. Dismayingly, physicians' management of the antibiotic supply has been poor and their defense of population health tepid at best. Acting as a prudent steward of the antibiotic supply often seems to be at odds with a physician's commonly understood fiduciary duties, ethical obligations, and professional norms, all of which traditionally emphasize the individual health paradigm as opposed to population health responsibilities. Meanwhile, physicians face limited incentives for antibiotic conservation from other sources, such as malpractice liability, regulatory standards, and reimbursement systems. While multifaceted efforts are needed to combat antibiotic resistance effectively, physician gatekeeping behavior should become a priority area of focus. This Article considers how health law and policy tools could favorably change the incentives physicians face for antibiotic conservation. A clear lesson from the managed care reform battles of the recent past is that interventions, to have the best chance of success, need to respect physician interest in clinical autonomy and individualized medicine even if, somewhat paradoxically, vigorously promoting population health perspectives. Also, physicians' legal and ethical obligations need to be reconceptualized in the antibiotic context in order to better support

  7. 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."

  8. Red Supergiants as Cosmic Abundance Probes

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    By studying a galaxy's present-day chemical abundances, we are effectively looking at its star-forming history. Cosmological simulations of galaxy evolution make predictions about the relative metal contents of galaxies as a function of their stellar mass, a trend known as the mass-metallicity relation. These predictions can be tested with observations of nearby galaxies. However, providing reliable, accurate abundance measurements at extragalactic distances is extremely challenging. In this project, we have developed a technique to extract abundance information from individual red supergiant stars at megaparsec distances. We are currently exploiting this technique using the unique capabilities of KMOS on the VLT.

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

    NASA Astrophysics Data System (ADS)

    Fouvry, Jean-Baptiste; Pichon, Christophe

    2015-05-01

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

  10. 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.

  11. 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

  12. 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

  13. Red supergiants as type II supernova progenitors

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  14. Secular diffusion in discrete self-gravitating tepid discs. I. Analytic solution in the tightly wound limit

    NASA Astrophysics Data System (ADS)

    Fouvry, J. B.; Pichon, C.; Chavanis, P. H.

    2015-09-01

    The secular evolution of an infinitely thin tepid isolated galactic disc made of a finite number of particles is described using the inhomogeneous Balescu-Lenard equation. Assuming that only tightly wound transient spirals are present in the disc, a WKB approximation provides a simple and tractable quadrature for the corresponding drift and diffusion coefficients. It provides insight into the physical processes at work during the secular diffusion of a self-gravitating discrete disc and makes quantitative predictions on the initial variations of the distribution function in action space. When applied to the secular evolution of an isolated stationary self-gravitating Mestel disc, this formalism predicts the initial importance of the corotation resonance in the inner regions of the disc leading to a regime involving radial migration and heating. It predicts in particular the formation of a ridge-like feature in action space, in agreement with simulations, but over-estimates the timescale involved in its appearance. Swing amplification is likely needed to resolve this discrepancy. In astrophysics, the inhomogeneous Balescu-Lenard equation and its WKB limit may also describe the secular diffusion of giant molecular clouds in galactic discs, the secular migration and segregation of planetesimals in proto-planetary discs, or even the long-term evolution of population of stars within the Galactic centre. Appendices are available in electronic form at http://www.aanda.org

  15. THE TEMPERATURES OF RED SUPERGIANTS

    SciTech Connect

    Davies, Ben; Kudritzki, Rolf-Peter; Gazak, Zach; Plez, Bertrand; Trager, Scott; Lancon, Ariane; Bergemann, Maria; Evans, Chris; Chiavassa, Andrea

    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.

  16. 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.

  17. Secular diffusion in discrete self-gravitating tepid discs II. Accounting for swing amplification via the matrix method

    NASA Astrophysics Data System (ADS)

    Fouvry, J. B.; Pichon, C.; Magorrian, J.; Chavanis, P. H.

    2015-12-01

    The secular evolution of an infinitely thin tepid isolated galactic disc made of a finite number of particles is investigated using the inhomogeneous Balescu-Lenard equation expressed in terms of angle-action variables. The matrix method is implemented numerically in order to model the induced gravitational polarisation. Special care is taken to account for the amplification of potential fluctuations of mutually resonant orbits and the unwinding of the induced swing amplified transients. Quantitative comparisons with N-body simulations yield consistent scalings with the number of particles and with the self-gravity of the disc: the fewer the particles and the colder the disc, the faster the secular evolution. Secular evolution is driven by resonances, but does not depend on the initial phases of the disc. For a Mestel disc with Q ~ 1.5, the polarisation cloud around each star boosts its secular effect by a factor of a thousand or more, accordingly promoting the dynamical relevance of self-induced collisional secular evolution. The position and shape of the induced resonant ridge are found to be in very good agreement with the prediction of the Balescu-Lenard equation, which scales with the square of the susceptibility of the disc. In astrophysics, the inhomogeneous Balescu-Lenard equation may describe the secular diffusion of giant molecular clouds in galactic discs, the secular migration and segregation of planetesimals in proto-planetary discs, or even the long-term evolution of population of stars within the Galactic centre. It could be used as a valuable check of the accuracy of N-body integrators on secular timescales. Appendices are available in electronic form at http://www.aanda.orgA copy of the linear matrix response code 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/584/A129

  18. A Census of B[e] Supergiants

    NASA Astrophysics Data System (ADS)

    Castillo, Robert

    2013-01-01

    B[e] supergiants are luminous, hot stars characterized by strong Balmer line emission, permitted emission lines like Fe II, forbidden (e.g., [Fe II]) optical emission lines, and large thermal IR excesses due to circumstellar dust. The relationship between B[e] supergiants and other classes of massive star is uncertain, as is the origin of their large masses of circumstellar material. The Magellanic Clouds (MCs) are presently known to host less than 20 objects classified as B[e] supergiants; yet these objects include most of the known members of the class. On the basis of a new search utilizing photometry from the Spitzer SAGE (Surveying the Agents of a Galaxy's Evolution) and Galaxy Evolution Explorer (Galex) survey databases, we have identified an additional 25 B stars in the LMC and 11 B stars in the SMC whose UV through infrared spectral energy distributions strongly resemble those of the known B[e] supergiants. Model atmospheres were fit to the photometric measurements to estimate photospheric temperatures for these candidates. Future spectroscopic observations will confirm how many among our new list of candidates are in fact B[e]-type stars. This research is supported by the NSF, via a Research Experience for Undergraduates program operated at RIT's Center for Imaging Science and by NASA Astrophysics Data Analysis Program award NNX11AB06G to RIT.

  19. 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.

  20. 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.

  1. The Red Supergiant Content of M31*

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Evans, Kate Anne

    2016-08-01

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

  2. The Red Supergiant Content of M31*

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Evans, Kate Anne

    2016-08-01

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

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

    SciTech Connect

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

    2013-02-20

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

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

    NASA Astrophysics Data System (ADS)

    Kraus, M.

    2016-08-01

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

  5. Long term variability of B supergiant winds

    NASA Technical Reports Server (NTRS)

    Massa, Derck L.

    1995-01-01

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

  6. YELLOW SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Drout, Maria R.; Massey, Philip; Meynet, Georges; Tokarz, Susan; Caldwell, Nelson E-mail: Phil.Massey@lowell.ed E-mail: tokarz@cfa.harvard.ed

    2009-09-20

    The yellow supergiant content of nearby galaxies can provide a critical test of stellar evolution theory, bridging the gap between the hot, massive stars and the cool red supergiants. But, this region of the color-magnitude diagram is dominated by foreground contamination, requiring membership to somehow be determined. Fortunately, the large negative systemic velocity of M31, coupled to its high rotation rate, provides the means for separating the contaminating foreground dwarfs from the bona fide yellow supergiants within M31. We obtained radial velocities of {approx}2900 individual targets within the correct color-magnitude range corresponding to masses of 12 M{sub sun} and higher. A comparison of these velocities to those expected from M31's rotation curve reveals 54 rank-1 (near certain) and 66 rank-2 (probable) yellow supergiant members, indicating a foreground contamination >= 96%. We expect some modest contamination from Milky Way halo giants among the remainder, particularly for the rank-2 candidates, and indeed follow-up spectroscopy of a small sample eliminates four rank 2's while confirming five others. We find excellent agreement between the location of yellow supergiants in the H-R diagram and that predicted by the latest Geneva evolutionary tracks that include rotation. However, the relative number of yellow supergiants seen as a function of mass varies from that predicted by the models by a factor of >10, in the sense that more high-mass yellow supergiants are predicted than those are actually observed. Comparing the total number (16) of >20 M{sub sun} yellow supergiants with the estimated number (24,800) of unevolved O stars indicates that the duration of the yellow supergiant phase is {approx}3000 years. This is consistent with what the 12 M{sub sun} and 15 M{sub sun} evolutionary tracks predict, but disagrees with the 20,000-80,000 year timescales predicted by the models for higher masses.

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

    SciTech Connect

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

    2015-05-10

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

  8. Supernova shock breakout from a red supergiant.

    PubMed

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

    2008-07-11

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

  9. Hunting for exploding red supergiant stars

    NASA Astrophysics Data System (ADS)

    Messineo, Maria; Menten, Karl M.; Figer, Donald F.; Ivanov, Valentin D.; Zhu, Qingfeng; Kudritzki, Rolf-Peter; Davies, Ben; Clark, J. Simon; Rich, Michael; Chen, Rosie; Trombley, Christine; MacKenty, John W.; Habing, Harm; Churchwell, Edward

    2015-08-01

    Red supergiants (RSGs) are among the brightest Galactic stars at infrared wavelengths. They lose mass at high-rates and, eventually, explode as supernovae, enriching the interstellar medium. I would like to present results on our ongoing searches for candidate obscured-far-luminous late-type stars, which are based on 2MASS, UKIDSS, and GLIMPSE data, on extinction-free colors(Messineo et al. 2012, A&A, 537) and on the analysis of the extinction curve along a given line-of-sight with clump stars. Messineo et al. (2014, A&A, 571, 43) spectroscopically confirmed two clusters of red supergiants, one on the Sagittarius-Carina spiral arm at a distance of ~7 kpc, and another on the Scutum-Crux arm at a distance of ~4 kpc; while Messineo et al. (2014, A&A, 569, 20) have, found several RSGs in the core of SNRs W41 and within the area covered by the SNR G22.7-0.2 in the GMC G23.3-0.3. SNR G22.7-0.2 appears to be most likely a type II SNR.Messineo , M.; Menten, K. M.; Churchwell, E.; Habing, H. 2012A&A...537A..10MMessineo, Maria; Zhu, Qingfeng; Ivanov, Valentin D.; Figer, Donald F.; Davies, Ben; Menten, Karl M.; Kudritzki, Rolf P.; Chen, C.-H. Rosie 2014A&A...571A..43MMessineo, Maria; Menten, Karl M.; Figer, Donald F.; Davies, Ben; Clark, J. Simon; Ivanov, Valentin D.; Kudritzki, Rolf-Peter; Rich, R. Michael; MacKenty, John W.; Trombley, Christine; 2014A&A...569A..20M

  10. Mass-losing M supergiants in the solar neighborhood

    NASA Technical Reports Server (NTRS)

    Jura, M.; Kleinmann, S. G.

    1990-01-01

    A list of the 21 mass-losing red supergiants (20 M type, one G type; L greater than 100,000 solar luminosities) within 2.5 kpc of the sun is compiled. These supergiants are highly evolved descendants of main-sequence stars with initial masses larger than 20 solar masses. The surface density is between about 1 and 2/sq kpc. As found previously, these stars are much less concentrated toward the Galactic center than W-R stars, which are also highly evolved massive stars. Although with considerable uncertainty, it is estimated that the mass return by the M supergiants is somewhere between 0.00001 and 0.00003 solar mass/sq kpc yr. In the hemisphere facing the Galactic center there is much less mass loss from M supergiants than from W-R stars, but, in the anticenter direction, the M supergiants return more mass than do the W-R stars. The duration of the M supergiant phase appears to be between 200,000 and 400,000 yr. During this phase, a star of initially at least 20 solar masses returns perhaps 3-10 solar masses into the interstellar medium.

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

    PubMed

    Berghöfer, T W; Schmitt, J H

    1994-09-16

    Hot massive stars represent only a small fraction of the stellar population of the galaxy, but their enormous luminosities make them visible over large distances. Therefore, they are ideal standard candles, used to determine distances of near galaxies. Their mass loss due to supersonic winds driven by radiation pressure contributes significantly to the interstellar medium and thus to the chemical evolution of galaxies. All hot stars are soft x-ray sources; in contrast to the sun with its highly variable x-ray flux, long time scale x-ray variability is not common among hot stars. An analysis is presented here of an unusual increase in x-ray flux observed with the roentgen observatory satellite during a period of 2 days for the hot supergiant zeta Orionis, the only episode of x-ray variability that has been found in a hot star. These observations provide the most direct evidence so far for the scenario of shock-heated gas in the winds of hot stars. PMID:17770897

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

    PubMed

    Berghöfer, T W; Schmitt, J H

    1994-09-16

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

  13. Another cluster of red supergiants close to RSGC1

    NASA Astrophysics Data System (ADS)

    Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S.

    2010-04-01

    Context. Recent studies have revealed massive star clusters in a region of the Milky Way close to the tip of the Long Bar. These clusters are heavily obscured and are characterised by a population of red supergiants. Aims: We analyse a previously unreported concentration of bright red stars ~16' away from the cluster RSGC1 Methods: We utilised near IR photometry to identify candidate red supergiants and then K-band spectroscopy of a sample to characterise their properties. Results: We find a compact clump of eight red supergiants and five other candidates at some distance, one of which is spectroscopically confirmed as a red supergiant. These objects must form an open cluster, which we name Alicante 8. Because of the high reddening and strong field contamination, the cluster sequence is not clearly seen in 2MASS or UKIDSS near-IR photometry. From the analysis of the red supergiants, we infer an extinction AKS = 1.9 and an age close to 20 Myr. Conclusions: Though this cluster is smaller than the three known previously, its properties still suggest a mass in excess of 10 000 M⊙. Its discovery corroborates the hypothesis that star formation in this region has happened on a wide scale between ~10 and ~20 Myr ago.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  15. Dust around main-sequence and supergiant stars

    NASA Astrophysics Data System (ADS)

    Sylvester, Roger James

    This thesis is a study of the properties of the dust around two rather different types of star. The first part is concerned with the mid-infrared emission from a sample of 16 M-type supergiants. As well as silicate emission features, seven of the stars showed the UIR (unidentified infrared) emission bands, associated with carbonaceous material. According to standard theory, all the carbon in the outflows from these oxygen-rich stars should be bound up in CO molecules, preventing the formation of carbonaceous dust. The results were interpreted in terms of a non-equilibrium chemical model, which invoked chromospheric UV photons to dissociate CO, allowing carbonaceous material to form, and to excite the observed UIR-band emission. The larger part of the thesis considers Vega-excess stars - main sequence stars with excess infrared emission from circumstellar dust discs. Photometric and spectroscopic observations were carried out. A number of the stars displayed excess near-IR emission, indicating the presence of hot material. Mid-infrared spectroscopy enabled the grain composition to be identified: both silicates and carbonaceous species were detected. Millimetre and submillimetre photometry indicated that large grains are present around many of our sources, implying that significant grain coagulation has occurred. Most of the sources were modelled using a radiative transfer code, with disc geometry and multiple grain sizes. Two grain materials, astronomical silicate and amorphous carbon, were considered. Successful fits to the spectral energy distributions at mid-IR and longer wavelengths were found. The temperatures needed to produce near-IR excess emission were too high for grains in thermal equilibrium to survive. A model was therefore developed with very small grains undergoing thermal spiking due to single-photon absorption, which provided satisfactory fits for the hottest stars; the others had insufficient UV flux to excite the small grains.

  16. Red Supergiants as Cosmic Abundance Probes: The Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Davies, Ben; Kudritzki, Rolf-Peter; Gazak, Zach; Plez, Bertrand; Bergemann, Maria; Evans, Chris; Patrick, Lee

    2015-06-01

    Red Supergiants (RSGs) are cool (˜4000 K), highly luminous stars (L˜ {{10}5} L⊙ ), and are among the brightest near-IR sources in star-forming galaxies. This makes them powerful probes of the properties of their host galaxies, such as kinematics and chemical abundances. We have developed a technique whereby metallicities of RSGs may be extracted from a narrow spectral window around 1 μm from only moderate resolution data. The method is therefore extremely efficient, allowing stars at large distances to be studied, and so has tremendous potential for extragalactic abundance work. Here, we present an abundance study of the Large and Small Magellanic Clouds (LMC and SMC respectively) using samples of 9-10 RSGs in each. We find average abundances for the two galaxies of {{[Z]}LMC}=-0.37+/- 0.14 and {{[Z]}SMC}=-0.53+/- 0.16 (with respect to a solar metallicity of {{Z}⊙ }=0.012). These values are consistent with other studies of young stars in these galaxies, and though our result for the SMC may appear high it is consistent with recent studies of hot stars which find 0.5-0.8 dex below solar. Our best-fit temperatures are on the whole consistent with those from fits to the optical-infrared spectral energy distributions, which is remarkable considering the narrow spectral range being studied. Combined with our recent study of RSGs in the Galactic cluster Per OB1, these results indicate that this technique performs well over a range of metallicities, paving the way for forthcoming studies of more distant galaxies beyond the Local Group.

  17. 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)

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

    SciTech Connect

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

    2014-10-01

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

  19. Late-Type Red Supergiants: Too Cool for the Clouds?

    NASA Astrophysics Data System (ADS)

    Levesque, Emily M.; Massey, P.; Olsen, K. A.; Plez, B.

    2006-12-01

    It has long been known that the median spectral types of red supergiants change from M2 I in the Milky Way to M1 I in the Large Magellanic Cloud (LMC) and to K5-7 I in the Small Magellanic Cloud (SMC) (Elias et al 1985, Massey & Olsen 2002). This is now understood in terms of the shifting of the evolutionary tracks to warmer temperatures with decreasing metallicity. Stars falling below the temperatures of these tracks would no longer be in hydrostatic equilibrium. This region of the H-R diagram is known as the Hayashi "forbidden zone". Early work identified supergiants no later than M2 I in the SMC, while in the Milky Way supergiants of spectral class M4 I and later abound. However, our work has identified seven red supergiants in the LMC and four red supergiants in the SMC, all of which have spectral types that are considerably later than the average type observed in their parent galaxy. We find that these stars have radial velocities which are consistent with membership in the Clouds. By fitting our moderate-resolution spectrophotometry of these stars with MARCS stellar atmosphere models of the appropriate metallicities, we also determine their physical parameters and place them on the H-R diagram for comparison with the predictions of current stellar evolutionary tracks. We find that these stars are colder and more luminous than allowed by the predictions of stellar evolutionary theory at these low metallicities. Unsurprisingly, these stars also exhibit unusual variability in V. We then suggest that these stars have such unusual properties because they are in an unstable (and short-lived) phase of their evolutionary lives. This work was supported by the National Science Foundation through AST-0604569 to PM.

  20. Models for circumstellar nebulae around red and blue supergiants

    NASA Astrophysics Data System (ADS)

    Chita, S. M.

    2011-10-01

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

  1. A New Survey for Red Supergiants in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    González-Fernández, C.; Negueruela, I.; Dorda, R.

    2016-10-01

    We present a pilot program focused on the red supergiant population of the Magellanic Clouds, with the intent of extending the current known sample to include the unexplored low end of the brightness distribution of these stars, building a more representative dataset with which to extrapolate their behavior to other Galactic and extra-galactic environments. For a pool of candidates selected over near-infrared photometry, we obtain medium resolution multi-object spectroscopy to confirm their nature and their membership in the clouds. Around two hundred new red supergiants have been detected, hinting at a yet-to-be-observed large population. Based on this sample, new a priori classification criteria are investigated, combining mid- and near-infrared photometry to improve the observational efficiency of programs similar to this. A more complete and detailed analysis of this dataset can be found in González- Fernández et al. (2015).

  2. Fast radio bursts counterparts in the scenario of supergiant pulses

    NASA Astrophysics Data System (ADS)

    Popov, S. B.; Pshirkov, M. S.

    2016-10-01

    We discuss identification of possible counterparts and persistent sources related to fast radio bursts (FRBs) in the framework of the model of supergiant pulses from young neutron stars with large spin-down luminosities. In particular, we demonstrate that at least some of the sources of FRBs can be observed as ultraluminous X-ray sources (ULXs). At the moment no ULXs are known to be coincident with localization areas of FRBs. We searched for a correlation of FRB positions with galaxies in the 2MASS Redshift survey catalogue. Our analysis produced statistically insignificant overabundance (p-value ≈ 4 per cent) of galaxies in error boxes of FRBs. In the very near future with even modestly increased statistics of FRBs and with the help of dedicated X-ray observations and all-sky X-ray surveys it will be possible to decisively prove or falsify the supergiant pulses model.

  3. Are blue supergiants descendants of magnetic main sequence stars?

    NASA Astrophysics Data System (ADS)

    Petermann, Ilka; Langer, Norbert

    2013-06-01

    Red and blue supergiants are, together with luminous blue variables and Wolf-Rayet stars, evolved phases of massive (OB) stars. The position of blue supergiants (BSG) near the main sequence band cannot be reproduced by standard stellar evolution calculations. However, the assumption of a reduced convective core mass during the main sequence (MS) due to strong internal magnetic fields, established in roughly 10% of all stars on the upper MS, can recover this BSG population. For our calculations of the (non-rotating) massive stars at solar metallicity we used the 1D stellar evolution code MESA and compare their evolutionary tracks with positions from stars obtained from the VLT Flames survey of massive stars.

  4. Chandra HETG Spectroscopy of the F0 Ib Supergiant Canopus

    NASA Astrophysics Data System (ADS)

    Brown, A.; Ayres, T. R.; Osten, R. A.; Harper, G. M.

    2000-10-01

    The F0 supergiant Canopus (α Car) was observed by the Chandra X-ray Observatory on 2000 July 21 for 96 ksec using the High Energy Transmission Grating (HETG) and the ACIS-S detector. Canopus is the nearest supergiant star at a distance of only 96 pc and undergoing He-burning, post-M-supergiant evolution. It has a hot (107 K) corona with log Lx ~ 29.8 erg s-1, even though it has only a thin convection zone. The HETG data show a coronal emission line spectrum with the strongest lines being from Fe XVII, Ne X, and O VIII. We shall present a detailed analysis of the HETG spectra and the first accurate description of this star's coronal temperature distribution. These coronal properties will be compared with those implied by earlier ASCA, EUVE, ROSAT, and Einstein observations. This work is supported by NASA LTSA grant NAG5-3226, NASA GSRP fellowship NGT5-50241, and the Chandra Guest Observer program.

  5. 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.

  6. On the Dynamic Stability of Cool Supergiant Atmospheres

    NASA Astrophysics Data System (ADS)

    Lobel, A.

    2001-09-01

    We have developed a new formalism to compute the thermodynamic coefficient Γ1 in the theory of stellar and atmospheric stability. We generalize the classical derivation of the first adiabatic index, which is based on the assumption of thermal ionization and equilibrium between gas and radiation temperature, toward an expression that incorporates photoionization due to radiation with a temperature Trad different from the local kinetic gas temperature. Our formalism considers the important non-LTE conditions in the extended atmospheres of supergiant stars. An application to the Kurucz grid of cool supergiant atmospheres demonstrates that models with Trad~=Teff between 6500 and 7500 K become most unstable against dynamic perturbations, according to Ledoux' stability integral <Γ1>. This results from Γ1 and <Γ1> acquiring very low values, below 4/3, throughout the entire stellar atmosphere, which causes very high gas compression ratios around these effective temperatures. Based on detailed non-LTE calculations, we discuss atmospheric instability of pulsating massive yellow supergiants, such as the hypergiant ρ Cas (Ia+), which exist in the extension of the Cepheid instability strip, near the Eddington luminosity limit.

  7. UV emission from he M1 supergiant TV Gem

    NASA Technical Reports Server (NTRS)

    Michalitsianos, A. G.; Kafatos, M.

    1982-01-01

    Low and high dispersion ultraviolet spectra were obtained of the M1 supergiant TV Gem with IUE. Previous IUE observations of this late type supergiant revealed unexpected UV continuum emission, perhaps arising from an early B companion. Low resolution spectra obtained approximately one year apart suggest that the strong Si III in combination perhaps with O I at wavelengths approximately 1300 A varies considerably with time. Large variation in the column density is required to explain these changes. Sporadic mass expulsion with mass loss rates dM/dt approximately 0.00001 solar mass yr minus 1st power from the M supergiant could lead to a dense circumstellar wind near the hot early companion, and thus could account for these observed variations in equivalent width. The high resolution spectrum in the 2000 to 3200 A wavelength range is characterized by narrow absorption lines primarily due to Fe II, Mn II and Mg II (h and k), which are skewed in profile with an extended red wing. This profile structure is tentatively attributed to interstellar absorption and an intervening differentially moving cloud in the direction of Gem OB1, of which TV Gem is a known association member.

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

    SciTech Connect

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

    2015-04-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Tanrıverdi, T.; Baştürk, Ö.

    2016-08-01

    This study presents elemental abundances of the early A-type supergiant HD 80057 and the late A-type supergiant HD 80404. High resolution and high signal-to-noise ratio spectra published by the UVES Paranal Observatory Project (Bagnulo et al., 2003)1

  12. Spectroscopic Study of HD 179821 (IRAS 19114+0002): Proto-Planetary Nebula or Supergiant?

    NASA Technical Reports Server (NTRS)

    Reddy, B. E.; Hrivnak, Bruce J.

    1999-01-01

    A detailed chemical composition analysis of the bright post-AGB candidate HD 179821 (IRAS 19114 + 0002) is presented. The LTE analysis, based on high-resolution (R approximately equal 50,000) and high-quality (S/N approximately equal 300) spectra, yields atmospheric parameters T(sub eff) = 6750 K, log g = 0.5, and xi(sub t) = 5.25 km/s. The elemental abundance results of HD 179821 are found to be [Fe/H] = -0.1, [C/Fe] = +0.2, [N/Fe] = +1.3, [O/Fe] = +0.2, [alpha-process/Fe] = +0.5, and [s-process/Fe] = +0.4. These values clearly differ from the elemental abundances of Population I F supergiants. The C, N, and O abundances and the total CNO abundance value relative to Fe, [C+N+O/Fe] = +0.5, indicate that the photosphere of HD 179821 is contaminated with both the H- and He-burning products of the AGB phase. The evidence for He burning through the 3.alpha process and deep AGB mixing also comes from the observed overabundances of s-process elements. Remarkably, the abundance of the element Na is found to be very large, [Na/Fe] = +0.9. The ratio O/C = 2.6 indicates that the atmosphere is oxygen rich. The results of this abundance study support the argument that HD 179821 is a proto-planetary nebula,. probably with an intermediate-mass progenitor. However, the strength of the O I triplet lines at 7774 A and the distance derived from the interstellar Na I D1 and D2 components imply that the star is a luminous object (M(sub bol) approximately -8.9 +/- 1) and thus a massive supergiant. Thus, while this study contributes important new observational results for this star, an unambiguous determination of its evolutionary status has yet to be achieved.

  13. THE YELLOW AND RED SUPERGIANTS OF M33

    SciTech Connect

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

    2012-05-10

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

  14. Magnetic main sequence stars as progenitors of blue supergiants

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  15. The Brightening of the Red Supergiant alpha Ori

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    We have been carrying out V-band and Wing TiO-band and Near-IR photoelectric photometry of the semi-regular variable red supergiant alpha Ori (Betelgeuse) over last 20 yrs. Photometry obtained during early to mid September 2016 indicates that the star is at (or near) maximum light at = +0.29 mag. Measures of TiO-band and near-IR colors indicate that alpha Ori has undergone a temperature increase of about +120 K and has an estimated spectral type of M0.5 Iab. Because alpha Ori is one of the nearest Type II SN progenitors, it an important star to monitor.

  16. Spectroscopic studies of yellow supergiants in the open cluster NGC 129

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.

    2015-09-01

    Spectroscopic studies of three yellow supergiants in the open cluster NGC 129, the classical Cepheid DL Cas, SAO 21450, and SAO 21482, have been performed on the basis of high-resolution spectra. For the two nonvariable cluster supergiants, the atmospheric parameters and chemical composition have been determined for the first time. SAO 21450 ( T eff = 6541 ± 16 K, log g = 2.00, V t = 4.20 km s-1) has nearly solar abundances of the key elements in the evolution of yellow supergiants (CNO, Na, Mg, and Al), while SAO 21482 ( T eff = 4506 ± 50 K, log g = 1.10, V t = 9.90 km s-1) exhibits an overabundance of carbon ([C/H] = +0.34 dex) and aluminum and nearly solar N, O, Na, and Mg abundances. The abundances of the key elements in the Cepheid DL Cas are typical for an object that has passed the first dredge-up: a C underabundance, N and Na overabundances, and nearly solar O, Mg, and Al abundances. In all objects, the abundances of iron [Fe/H] = -0.01 dex, α-elements, Fe-peak elements, and r- and s-process elements are virtually identical and nearly solar. The radial velocities of SAO 21482 measured from metal absorption lines have confirmed its membership in NGC 129. The knifelike shape of the H α and H β line profiles in SAO 21482 and the asymmetry of the Mg Ib 5183.618 Å line in SAO 21482 and DL Cas as well as the absorption lines of neutral atoms and ions of metals in the Cepheid suggest the existence of extended gaseous envelopes around them. The positions of the objects on the T eff- L diagram among the tracks of evolutionary masses for the objects show the following: (1) the primary component of SAO 21450 has a mass of 6.6 M ⊙ and approaches the blue edge of the Cepheid instability strip (CIS) for the first time, while its companion of possible spectral type B5 V has a mass of 4.8 M ⊙; (2) DL Cas is on the path of its CIS with a mass of 5.8 M ⊙ and has lost ~1.5 M ⊙ after the first dredge-up; (3) SAO 21482 with a mass of no more than 7.3 M ⊙ has

  17. YELLOW AND RED SUPERGIANTS IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect

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

    2012-04-20

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

  18. The Swift Supergiant Fast X-ray Transients outburst factory

    NASA Astrophysics Data System (ADS)

    Romano, Patrizia; Kennea, Jamie; Barthelmy, Scott Douglas; Bozzo, Enrico; Burrows, David N.; Ducci, Lorenzo; Esposito, Paolo; Evans, Phil; Gehrels, Neil; Krimm, Hans A.; Vercellone, Stefano

    2016-04-01

    We present the Swift Supergiant Fast X-ray Transients project, which has been exploiting Swift's capabilities in a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) since 2007. We performed an efficient long-term monitoring of 16 sources including both SFXTs and classical SGXBs and followed source activity across more than 4 orders of magnitude in X-ray luminosity, sampling the light curves on timescales spanning from few hundred seconds to years. We use our measurements of dynamic ranges, duty cycles as a function of luminosity, and luminosity distributions to highlight systematic differences that help discriminate between different theoretical models proposed to explain the differences between the wind accretion processes in SFXTs and classical SGXBs. Our follow-ups of the SFXT outbursts provide a steady advancement in the comprehension of the mechanisms triggering the high X-ray level emission of these sources. In particular, the recent observations of the outburst of the SFXT prototype IGR J17544-2619 on 2014 October 10, when the source reached a peak luminosity of 3x1038 erg s-1, challenged, for the first time, the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object.

  19. Blue supergiants as descendants of magnetic main sequence stars

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    About 10% of the massive main sequence stars have recently been found to host a strong, large scale magnetic field. Both, the origin and the evolutionary consequences of these fields are largely unknown. We argue that these fields may be sufficiently strong in the deep interior of the stars to suppress convection near the outer edge of their convective core. We performed parametrised stellar evolution calculations and assumed a reduced size of the convective core for stars in the mass range 16M⊙ to 28M⊙ from the zero age main sequence until core carbon depletion. We find that such models avoid the coolest part of the main sequence band, which is usually filled by evolutionary models that include convective core overshooting. Furthermore, our "magnetic" models populate the blue supergiant region during core helium burning, i.e., the post-main sequence gap left by ordinary single star models, and some of them end their life in a position near that of the progenitor of Supernova 1987A in the Hertzsprung-Russell diagram. Further effects include a strongly reduced luminosity during the red supergiant stage, and downward shift of the limiting initial mass for white dwarf and neutron star formation.

  20. 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.

  1. 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.

  2. 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

  3. Spectroscopic Analysis of the Supergiant Star HD 54605

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  7. 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.

  8. The wind momentum-luminosity relationship of galactic A- and B-supergiants

    NASA Astrophysics Data System (ADS)

    Kudritzki, R. P.; Puls, J.; Lennon, D. J.; Venn, K. A.; Reetz, J.; Najarro, F.; McCarthy, J. K.; Herrero, A.

    1999-10-01

    The Balmer lines of four A Ia-supergiants (spectral type A0 to A3) and fourteen B Ia and Ib-supergiants (spectral type B0 to B3) in the solar neighbourhood are analyzed by means of NLTE unified model atmospheres to determine the properties of their stellar winds, in particular their wind momenta. As in previous work for O-stars (Puls et al. \\cite{pul96}) a tight relationship between stellar wind momentum and luminosity (``WLR'') is found. However, the WLR varies as function of spectral type. Wind momenta are strongest for O-supergiants, then decrease from early B (B0 and B1) to mid B (B1.5 to B3) spectral types and become stronger again for A-supergiants. The slope of the WLR appears to be steeper for A- and mid B-supergiants than for O-supergiants. The spectral type dependence is interpreted as an effect of ionization changing the effective number and the line strength distribution function of spectral lines absorbing photon momentum around the stellar flux maximum. This interpretation needs to be confirmed by theoretical calculations for radiation driven winds. The ``Pistol-Star'' in the Galactic Centre, an extreme mid B-hypergiant recently identified as one of the most luminous stars (Figer et al. \\cite{fig99}) is found to coincide with the extrapolation of the mid B-supergiant WLR towards higher luminosities. However, the wind momentum of the Luminous Blue Variable P Cygni, a mid B-supergiant with extremely strong mass-loss, is 1.2 dex higher than the WLR of the ``normal'' supergiants. This significant difference is explained in terms of the well-known stellar wind bi-stability of supergiants very close to the Eddinton-limit in this particular range of effective temperatures. A-supergiants in M31 observed with HIRES at the Keck telescope have wind momenta compatible with their galactic counterparts. The potential of the WLR as a new, independent extragalactic distance indicator is discussed. It is concluded that with ten to twenty objects, photometry with HST

  9. Accretion in supergiant High Mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Manousakis, A.; Blondin, J.; Walter, R.

    2013-09-01

    Supergiant High Mass X-ray Binary systems (sgHMXBs) consist of a massive, late type, star and a neutron star. The massive stars exhibit strong, radiatively driven, stellar winds. Wind accretion onto compact object triggers X-ray emission, which alters the stellar wind significantly. Hydrodynamic simulation has been used to study the neutron star - stellar wind interaction it two sgHMXBs: i) A heavily obscured sgHMXB (IGR J17252-3616) discovered by INTEGRAL. To account for observable quantities (i.e., absorbing column density) we have to assume a very slow wind terminal velocity of about 500 km/s and a rather massive neutron star. If confirmed in other obscured systems, this could provide a completely new stellar wind diagnostics. ii) A classical sgHMXB (Vela X-1) has been studied in depth to understand the origin of the off-states observed in this system. Among many models used to account for this observed behavior (clumpy wind, gating mechanism) we propose that self-organized criticality of the accretion stream is the likely reason for the observed behavior. In conclusion, the neutron star, in these two examples, acts very efficiently as a probe to study stellar winds.

  10. Stellar winds in supergiant High Mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Manousakis, Antonios; Walter, Roland

    2013-06-01

    Supergiant High Mass X-ray Binary systems (sgHMXBs) consist of a massive, late type, star and a neutron star. The massive stars exhibit strong, radiatively driven, stellar winds. Wind accretion onto compact object triggers X-ray emission, which alters the stellar wind significantly. Hydrodynamic simulation has been used to study the neutron star - stellar wind interaction it two sgHMXBs: i) A heavily obscured sgHMXB (IGR J17252-3616) discovered by INTEGRAL. To account for observable quantities (i.e., absorbing column density) we have to assume a very slow wind terminal velocity of about 500 km/s and a rather massive neutron star. If confirmed in other obscured systems, this could provide a completely new stellar wind diagnostics. ii) A classical sgHMXB (Vela X-1) has been studied in depth to understand the origin of the off-states observed in this system. Among many models used to account for this observed behavior (clumpy wind, gating mechanism) we propose that self-organized criticality of the accretion stream is the likely reason for the observed behavior.

  11. Accretion in supergiant High Mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Manousakis, Antonios; Walter, Roland; Blondin, John

    2014-01-01

    Supergiant High Mass X-ray Binary systems (sgHMXBs) consist of a massive, late type, star and a neutron star. The massive stars exhibits strong, radiatively driven, stellar winds. Wind accretion onto compact object triggers X-ray emission, which alters the stellar wind significantly. Hydrodynamic simulation has been used to study the neutron star - stellar wind interaction it two sgHMXBs: i) A heavily obscured sgHMXB (IGR J17252-3616) discovered by INTEGRAL. To account for observable quantities (i.e., absorbing column density) we have to assume a very slow wind terminal velocity of about 500 km/s and a rather massive neutron star. If confirmed in other obscured systems, this could provide a completely new stellar wind diagnostics. ii) A classical sgHMXB (Vela X-1) has been studied in depth to understand the origin of the off-states observed in this system. Among many models used to account for this observed behavior (clumpy wind, gating mechanism) we propose that self-organized criticality of the accretion stream is the likely reason for the observed behavior. In conclusion, the neutron star, in these two examples, acts very effciently as a probe to study stellar winds.

  12. Yellow and Red Supergiants in the Local Group

    NASA Astrophysics Data System (ADS)

    Massey, Philip; Neugent, Kathryn; Drout, Maria; Meynet, Georges

    2013-06-01

    Yellow and red supergiants are the "poor cousins" of massive star studies, often overlooked in favor of strong emission-lined Wolf-Rayets or the spectacular, enigmatic Luminous Blue Variables. Recent studies, however, are proving the truth of Kippenhahn & Weigert (1990)'s claim that these evolved stages act as a "sort of magnifying glass, revealing relentlessly the faults of calculations of earlier phases." Identifying complete samples of YSGs and RSGs among the galaxies of the Local Group is difficult, as foreground dwarfs are nearly indistinguishable from bona-fide extragalactic members. We have succeeded in this task only by using a combination of wide-area photometry surveys combined with spectroscopic followup. Since massive star evolution is greatly affected by mass-loss, and mass-loss rates depend upon metallicity, we have conducted such studies over a range of 10 in metallicity, including the SMC, LMC, M33, and M31. These studies not only allow us to test the stellar evolutionary models, but the identification of these stars provides interesting kinematic information on the youngest stellar populations in these galaxies. We will review here what we have learned over the past few years, and what new questions these studies are raising.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  14. Seven years with the Swift Supergiant Fast X-ray Transients project

    NASA Astrophysics Data System (ADS)

    Romano, P.

    2015-09-01

    Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions. I review the results of the Swift SFXT project, which since 2007 has been exploiting Swift's capabilities in a systematic study of SFXTs and supergiant X-ray binaries (SGXBs) by combining follow-ups of outbursts, when detailed broad-band spectroscopy is possible, with long-term monitoring campaigns, when the out-of-outburst fainter states can be observed. This strategy has led us to measure their duty cycles as a function of luminosity, to extract their differential luminosity distributions in the soft X-ray domain, and to compare, with unprecedented detail, the X-ray variability in these different classes of sources. I also discuss the "seventh year crisis", the challenges that the recent Swift observations are making to the prevailing models attempting to explain the SFXT behavior.

  15. Expected number of supergiant fast X-ray transients in the Milky Way

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    In the past fifteen years a new generation of X-ray satellites led to the discovery of a subclass of high-mass X-ray binaries (HMXBs) with supergiant companions and a peculiar transient behaviour: supergiant fast X-ray transients (SFXTs). We calculate the expected number of Galactic SFXTs for the first time, using two different statistical approaches and two sets of data based on Swift and INTEGRAL surveys, with the aim to determine how common the SFXT phenomenon really is. We find that the expected number of SFXTs in the Galaxy is 37+53-22, which shows that SFXTs constitute a large portion of X-ray binaries with supergiant companions in the Galaxy. We compare our estimate with the expected number of Galactic HMXBs predicted from observations and evolutionary models and discuss the implications for the nature of SFXTs.

  16. Extinction and Scattering Properties of Dust Around Red Supergiants

    NASA Astrophysics Data System (ADS)

    Bright, Stacey; Clayton, G.; Massey, P.; Gordon, K.; Levesque, E.; Plez, B.

    2007-12-01

    We have been amassing a unique dataset which can be used to investigate the amount and nature of dust produced by red supergiants (RSGs) in very different environments. To this end, optical spectra are being obtained for RSGs in various galaxies in the Local Group. Moderate-resolution, high S/N, spectrophotometry, covering 3500-9000A, has been obtained for a sample of RSGs in the Milky Way and the Magellanic Clouds. Using the the MARCS stellar atmosphere models to fit the SEDs, we are deriving extinction curves from 3500A to the K-band for the Local Group RSGs. In particular, for the LMC and SMC stars, the problem is more tractable than for the Milky Way RSGs, given the small and relatively uniform foreground extinction of the Clouds. We will construct extinction curves using the classic "pair method". The feasibility of using the model SEDs as "unreddened" standards will be examined, as well as the more conventional pairing of stars that are closely matched in spectral type but have different reddenings. These extinction curves are actually attenuation curves since the RSG circumstellar dust shells are not resolved and light can be scattered back into the beam. In particular, we plan to examine the apparent NUV excess seen in the Galactic RSG extinction curves. The NUV excess is possibly due to scattering of the star's light by circumstellar dust and/or a larger average size than that typical of grains found in the diffuse interstellar medium. This project is being supported by NSF grant AST-0707691 and a LaSPACE Undergraduate Research Assistantship (NASA grant NNG05GH22H).

  17. Dust Around Red Supergiants in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Bright, Stacey N.; Chatelain, J.; Freeman, W.; Clayton, G.; Gordon, K.; Nordhaus, J.; Massey, P.; Levesque, E.; Plez, B.; Olsen, K.; Silva, D.

    2009-01-01

    We have gathered together a unique dataset for red supergiants (RSGs) in the Magellanic Clouds, which can be used to investigate the amount and nature of dust produced by RSGs in different environments. For a sample of 40 RSGs in each of the LMC and the SMC, we have obtained visible spectrophotometry (4000-9000 A), 2MASS photometry (JHK), and photometry in the Spitzer IRAC and MIPS bands. In addition, we have obtained Spitzer/IRS spectra for 10 stars in each galaxy. We will use our Monte Carlo radiative transfer models to analyze the emission from dust in the circumstellar shells. We plan to use the IRS data to make a systematic study of the dust properties in RSG shells in the LMC and SMC so that we can probe how they may vary with a large range of galactic metallicities. The derived stellar SEDs and extinction curves will be combined with the IRAC and MIPS photometry and IRS spectra as inputs to our Monte Carlo codes which will be used to study the composition, size distributions and clumpiness of the dust. We will model the dust shells using amorphous carbon and silicate dust grains as well as PAHs appropriate to these shells. This modeling will allow us to infer the total circumstellar dust mass around the sample RSGs. We will also consider whether the large global metallicity differences between galaxies lead to observable differences in the dust being produced by their RSGs. This project is being supported by NSF grant AST-0707691 and a LaSPACE Undergraduate Research Assistantship (NASA grant NNG05GH22H).

  18. On the Explosion Geometry of Red Supergiant Stars

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  19. Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Bozzo, E.; Oskinova, L.; Feldmeier, A.; Falanga, M.

    2016-05-01

    The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.

  20. On the neutron stars in supergiant fast x-ray transients

    NASA Astrophysics Data System (ADS)

    Li, Xiangdong

    Supergiant Fast X-ray Transients (SFXTs) are a new class of high-mass X-ray binaries com-posed by a massive OB supergiant star as companion donor and a compact object, possibly a neutron star. SFXTs display short X-ray outbursts characterized by fast flares on brief timescales of hours and large flux variability typically in the range 103 - 105 . Based on the most recent observational features of SFXTs we discuss the evolution of the neutron stars in SFXTs, and suggest that they may be born with relatively long spin periods.

  1. 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

  2. DISCOVERY OF THE FIRST B[e] SUPERGIANTS IN M 31

    SciTech Connect

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

  3. 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).

  4. What does C II lambda 2325 A emission tell us about chromospheres of red supergiants? - A critical test using Zeta Aurigae-type K supergiants

    NASA Technical Reports Server (NTRS)

    Schroeder, K.-P.; Reimers, D.; Carpenter, K. G.; Brown, A.

    1988-01-01

    The limitations of the Carpenter et al. (1985) C II intercombination multiplet method of determining the density and geometric extent of red giant chromospheres are presently tested through observation of the C II 2325 A emission of two K-type supergiants whose empirical model chromospheres have been derived by high-resolution IUE observations at eclipse phases. While the observed C II emission fluxes are well reproduced, much of this emission originates in the high-density lower chromosphere.

  5. 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.

  6. RED SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Massey, Philip; Silva, David R.; Olsen, Knut A. G.; Levesque, Emily M.; Plez, Bertrand; Clayton, Geoffrey C.; Meynet, Georges; Maeder, Andre E-mail: dsilva@noao.ed E-mail: emsque@ifa.hawaii.ed E-mail: gclayton@fenway.phys.lsu.ed E-mail: andre.maeder@unige.c

    2009-09-20

    Red supergiants (RSGs) are a short-lived stage in the evolution of moderately massive stars (10-25 M{sub sun}), and as such their location in the H-R diagram provides an exacting test of stellar evolutionary models. Since massive star evolution is strongly affected by the amount of mass loss a star suffers, and since the mass-loss rates depend upon metallicity, it is highly desirable to study the physical properties of these stars in galaxies of various metallicities. Here we identify a sample of RSGs in M31, the most metal-rich of the Local Group galaxies. We determine the physical properties of these stars using both moderate resolution spectroscopy and broadband V - K photometry. We find that on average the RSGs of our sample are variable in V by 0.5 mag, smaller but comparable to the 0.9 mag found for Magellanic Cloud (MC) RSGs. No such variability is seen at K, also in accord with what we know of Galactic and MC RSGs. We find that there is a saturation effect in the model TiO band strengths with metallicities higher than solar. The physical properties we derive for the RSGs from our analysis with stellar atmosphere models agree well with the current evolutionary tracks, a truly remarkable achievement given the complex physics involved in each. We do not confirm an earlier result that the upper luminosities of RSGs depend upon metallicity; instead, the most luminous RSGs have log L/L{sub sun}{approx}5.2-5.3, broadly consistent but slightly larger than that recently observed by Smartt et al. as the upper luminosity limit to Type II-P supernovae, believed to have come from RSGs. We find that, on average, the RSGs are considerably more reddened than O and B stars, suggesting that circumstellar dust is adding a significant amount of extra extinction, {approx}0.5 mag, on average. This is in accord with our earlier findings on Milky Way and Magellanic Cloud stars. Finally, we call attention to a peculiar star whose spectrum appears to be heavily veiled, possibly due

  7. SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR

    SciTech Connect

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

    2012-01-15

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

  8. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  10. Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    Aims: 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_eff}, {log L*}, 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 {T_eff} 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 B0-B5 supergiants analysed show evidence of CNO processing. A mass discrepancy still exists between spectroscopic and evolutionary masses, with the largest discrepancy occurring at {log (L/L⊙}) 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

  11. Radiative Transfer Modeling of Warm Transition Region Winds in F- and G-type Supergiants

    NASA Astrophysics Data System (ADS)

    Lobel, A.; Avrett, E. H.; Aufdenberg, J. P.

    2004-12-01

    We present FUSE spectra of upper transition region emission lines of O VI in the dynamic atmosphere of the short-period classic Cepheid Beta Dor (F-G Ia). The far-UV O VI 1032 & 1037 Å lines indicate a heating mechanism in the outer atmospheres of strongly pulsating F- and G-type supergiants sustaining hot plasmas at kinetic gas temperatures between 100 kK and 300 kK. Our observation of prominent upper transition region emission lines in Beta Dor contrasts with the very low X-ray luminosities of Cepheid variables that signal only weak coronal plasmas. On the other hand, FUSE and HST-STIS observations of the non-variable yellow (hybrid) supergiants Alpha Aqr (G2 Ib) and Beta Aqr (G0 Ib), having large X-ray fluxes, reveal supersonic warm wind velocities of 140 km/s and 90 km/s, respectively, in lower transition region emission lines of C III 977 Å and Si III 1206 Å. Our semi-empiric radiative transfer models show that these optically thick winds occur at kinetic gas temperatures well above 70 kK, much larger than assumed for the chromospheres of cool supergiants. Remarkably, these emission lines reveal peculiar shapes reminiscent of P-Cygni type line profiles observed in UV spectra of hot supergiants. Both hybrid supergiants lack the strongly oscillating photospheres of Cepheids, suggesting that their transition region wind acceleration and heating do not result from a pure mechanical driving mechanism due to atmospheric pulsations. We present detailed semi-empiric radiative transfer models of the thermal and dynamic structures of the outer atmospheres of these luminous F- and G-type supergiants based on the FUSE and HST-STIS spectra. We investigate if warm accelerating winds observed in high ions of cool supergiants can (partly) be driven by radiation pressure. This research is based on data obtained with the NASA/ESA Hubble Space Telescope, collected at the STScI, operated by AURA Inc., under contract NAS5-26555. Financial support has been provided by STSc

  12. The Wind of Rotating B Supergiants. I. Domains of Slow and Fast Solution Regimes

    NASA Astrophysics Data System (ADS)

    Venero, R. O. J.; Curé, M.; Cidale, L. S.; Araya, I.

    2016-05-01

    In the scenario of rotating radiation-driven wind theory for massive stars, three types of stationary hydrodynamic solutions are currently known: the classical (fast) m-CAK solution, the Ω-slow solution that arises for fast rotators, and the so-called δ-slow solution if high values of the δ line-force parameter are allowed independently of the rotation speed. Compared to the fast solution, both “slow solutions” have lower terminal velocities. As the study of the parameter domain for the slow solution is still incomplete, we perform a comprehensive analysis of the distinctive flow regimes for B supergiants that emerge from a fine grid of rotation values, Ω, and various ionization conditions in the wind (δ) parameter. The wind ionization defines two domains: one for fast outflowing winds and the other for slow expanding flows. Both domains are clear-cut by a gap, where a kink/plateau structure of the velocity law could exist for a finite interval of δ. The location and width of the gap depend on T eff and Ω. There is a smooth and continuous transition between the Ω-slow and δ-slow regimes, a single Ω δ-slow regime. We discuss different situations where the slow solutions can be found and the possibility of a switch between fast and slow solutions in B supergiant winds. We compare the theoretical terminal velocity with observations of B and A supergiants and find that the fast regime prevails mostly for early B supergiants while the slow wind regime matches better for A and B mid- and late-type supergiants.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  14. Comparative Spectroscopic Analysis of B[e] Supergiants and LBV

    NASA Astrophysics Data System (ADS)

    Borges Fernandes, M.

    2000-02-01

    The upper HRD is populated by massive stars. These objects have, as a characteristic, a substantial mass loss, due mostly to radiation pressure, throughout their whole lives. However about the evolution of these stars, the only secure informations are that they are B or O type stars in the zero age main sequence and they finish their lifes in a supernova explosion. The difficulties, to ascertain the others evolutive stages of these objects, are that they do not exhibit (in most cases) photosferic absorption lines, due to their complex circumstellar medium, preventing the estimate of the physical parameters. Moreover, these phases are relatively "shorts", and so we have a little sample of objects. Among the "short" phases, we detach the B[e] Supergiant (B[e]sg) and the Luminous Blue Variable (LBV) phases. The stars in these two evolutive stages show similar characteristics in the optical spectrum. They are, the presence in B type stars, of forbidden emission lines of [FeII], [OI] (in the B[e]sg) and [NII] (in the LBV). The presence of strong Balmer emission lines, low excitation permitted emission lines of predominantly low ionization metals, e.g. FeII in the optical spectrum and a strong near or mid-infrared excess due to hot circumstellar dust. In general, the Balmer lines (and sometimes HeI and FeII lines too) show P-Cygni profiles, due to mass loss. In despite of the similarities, the LBV are separated of the B[e]sg, due to strong spectral-photometric variability. Then it is necessary a detailed spectroscopical analysis of some objects, to obtain not only a better classification, like a B[e]sg or LBV, but useful informations to perform in the future a physical model. We have done such analysis for five stars in the Galaxy: HD 87643, HD 89249, HR Car, GG Car and CPD-529243. With our new data, others presented by literature, and a long time monitoring of these stars, we believe that in the near future, it will be possible to determine a correct classification to

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  18. 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

  19. A cool supergiant with anomalous behavior of the 2800 Mg II doublet

    NASA Technical Reports Server (NTRS)

    Gurzadian, G. A.; Rustambekian, S. S.; Kondo, Y.; Perez, Mario R.; Terzian, Yervant

    1991-01-01

    The IUE ultraviolet spectrum for a supergiant of type G Ia, HD 135345, is obtained for the wavelength region 2000-3000 A. In the spectrum, the continuum as well as the feature of the Mg II doublet at 2800 A is found to be anomalous. The observed level of continuum increases toward short wavelengths to 2000 A, verifying that this supergiant is actually a binary system with a hot companion. The anomalies in the magnesium doublet are the complete absence of the chromospheric emission and the very small equivalent width of the doublet absorption: the equivalent width is 4 A, which is 7.5 times smaller than that for a typical G5 star. The main parameters of the binary system are obtained, namely, spectral classes, effective temperatures, ratio of radii, and visible magnitudes.

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

    NASA Astrophysics Data System (ADS)

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

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

  1. 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

  2. The evolution of Red Supergiants to supernova in the LMC cluster NGC 2100

    NASA Astrophysics Data System (ADS)

    Beasor, Emma R.; Davies, Ben

    2016-08-01

    The mass loss rates of red supergiants (RSGs) govern their evolution towards supernova and dictate the appearance of the resulting explosion. To study how mass-loss rates change with evolution we measure the mass-loss rates (dot{M}) and extinctions of 19 red supergiants in the young massive cluster NGC2100 in the Large Magellanic Cloud. By targeting stars in a coeval cluster we can study the mass-loss rate evolution whilst keeping the variables of mass and metallicity fixed. Mass-loss rates were determined by fitting DUSTY models to mid-IR photometry from WISE and Spitzer/IRAC. We find that the dot{M} in red supergiants increases as the star evolves, and is well described by dot{M} prescription of de Jager, used widely in stellar evolution calculations. We find the extinction caused by the warm dust is negligible, meaning the warm circumstellar material of the inner wind cannot explain the higher levels of extinction found in the RSGs compared to other cluster stars. We discuss the implications of this work in terms of supernova progenitors and stellar evolution theory. We argue there is little justification for substantially increasing the dot{M} during the RSG phase, as has been suggested recently in order to explain the absence of high mass Type IIP supernova progenitors. We also argue that an increase in reddening towards the end of the RSG phase, as observed for the two most evolved cluster stars, may provide a solution to the red supergiant problem.

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

    SciTech Connect

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

    2014-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. 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.

  7. 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

  8. Evidence for Tidal Heating in the Dynamics of LMC Carbon Stars and Red Supergiants

    NASA Astrophysics Data System (ADS)

    Olsen, Knut A.; Massey, P.

    2006-12-01

    We present an analysis of the kinematics of the HI gas, carbon stars, and red supergiants of the Large Magellanic Cloud. After correcting the line-of-sight velocities for the recent accurate measurement of the LMC's space motion, we find that each kinematic tracer clearly defines a flat rotation curve with similar shape but different amplitude for each tracer: 61 km s-1 for the carbon stars, 80 km s-1 for the HI gas, and 107 km s-1 for the red supergiants. We suggest that noncircular motions of the stars and gas in the LMC can at least in part explain the different rotation amplitudes. A significant fraction, 7-15%, of the total sample of carbon stars appears to be associated with previously identified tidal HI streamers. In addition, although the local velocity dispersion of the red supergiants is small, 8 km s-1, their velocity dispersion about the carbon star rotation solution is 17 km s-1, equal to the velocity dispersion of the carbon stars themselves. We thus appear to be witnessing the tidal heating of the LMC's stellar populations.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Plewa, Tomasz; Handy, Timothy; Odrzywolek, Andrzej

    2014-03-01

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

  11. On the Hα behaviour of blue supergiants: rise and fall over the bi-stability jump

    NASA Astrophysics Data System (ADS)

    Petrov, Blagovest; Vink, Jorick S.; Gräfener, Götz

    2014-05-01

    Context. The evolutionary state of blue supergiants is still unknown. Stellar wind mass loss is one of the dominant processes determining the evolution of massive stars, and it may provide clues to the evolutionary properties of blue supergiants. As the Hα line is the most oft-used mass-loss tracer in the OB-star regime, we investigate Hα line formation as a function of Teff. Aims: We provide a detailed analysis of the Hα line for OB supergiant models over an Teff range between 30 000 and 12 500 K, with the aim of understanding the mass-loss properties of blue supergiants. Methods: We model the Hα line using the non-LTE code cmfgen, in the context of the bi-stability jump at Teff ~ 22 500 K. Results: We find a maximum in the Hα equivalent width at 22 500 K exactly at the location of the bi-stability jump. The Hα line-profile behaviour is characterised by two branches of effective temperature: (i) a hot branch between 30 000 and 22 500 K, where Hα emission becomes stronger with decreasing Teff; and (ii) a cool branch between 22 500 and 12 500 K, where the Hα line becomes weaker. Our models show that this non-monotonic Hα behaviour is related to the optical depth of Lyα, finding that at the "cool" branch the population of the 2nd level of hydrogen is enhanced in comparison to the 3rd level. This is expected to increase line absorption, leading to weaker Hα flux when Teff drops from 22 500 K downwards. We also show that for late B supergiants (at Teff below ~15 000 K), the differences in the Hα line between homogeneous and clumpy winds becomes insignificant. Moreover, we show that, at the bi-stability jump, Hα changes its character completely, from an optically thin to an optically thick line, implying that macro-clumping should play an important role at temperatures below the bi-stability jump. This would not only have consequences for the character of observed Hα line profiles, but also for the reported discrepancies between theoretical and empirical

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

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

    SciTech Connect

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

    2009-06-15

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

  14. Searching for Complex, Weak or Tangled Magnetic Fields in the Blue Supergiant Rigel

    NASA Astrophysics Data System (ADS)

    Shultz, M.; Wade, G. A.; Neiner, C.; Manset, N.; Petit, V.; Grunhut, J.; Guinan, E.; Hanes, D.; Mimes Collaboration

    Seventy-eight high-resolution Stokes V, Q and U spectra of the B8 Iae supergiant Rigel were obtained with the ESPaDOnS instrument at the CFHT, and its clone NARVAL at the TBL in the context of the Magnetism in Massive Stars (MiMeS) Large Program, with the aim of scrutinizing this core-collapse supernova progenitor for direct evidence of weak and/or complex magnetic fields. In this paper we describe the reduction and analysis of the data, the constraints obtained on any magnetic field present in the stellar photosphere, and the variability of photospheric and wind lines.

  15. Microwave continuum measurements and estimates of mass loss rates for cool giants and supergiants

    NASA Technical Reports Server (NTRS)

    Drake, S. A.; Linsky, J. L.

    1986-01-01

    Attention is given to the results of a sensitive, 6-cm radio continuum survey conducted with the NRAO VLA of 39 of the nearest single cool giants and supergiants of G0-M5 spectral types; the survey was conducted in order to obtain accurate measurements of the mass loss rates of ionized gas for a representative sample of such stars, in order to furnish constraints for, and a better understanding of, the total mass loss rates. The inferred angular diameters for the cool giant sources are noted to be twice as large as photospheric angular diameters, implying that these stars are surrounded by extended chromospheres containing warm partially ionized gas.

  16. The circumstellar envelopes of F- and G-type supergiants in the Large Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Hagen, W.; Humphreys, R. M.; Stencel, R. E.

    1981-01-01

    The outer atmospheres of four F- and G-type supergiants in the LMC are compared with those of their Milky Way counterparts by means of 2.5 and 5.1 A/mm high dispersion Echelle spectra. Na I D line doubling indicates extensive circumstellar envelopes, mass loss rates greater than 0.00001 solar masses/year, and outflow velocities of 10-60 km/sec. The Ca II H and K lines yield new data on extragalactic star chromospheres.

  17. Temperature, gravity, and bolometric correction scales for non-supergiant OB stars

    NASA Astrophysics Data System (ADS)

    Nieva, M.-F.

    2013-02-01

    Context. Precise and accurate determinations of the atmospheric parameters effective temperature and surface gravity are mandatory to derive reliable chemical abundances in OB stars. Furthermore, fundamental parameters like distances, masses, radii, luminosities can also be derived from the temperature and gravity of the stars. Aims: Atmospheric parameters recently determined at high precision with several independent spectroscopic indicators in non-local thermodynamic equilibrium, with typical uncertainties of ~300 K for temperature and of ~0.05 dex for gravity, are employed to calibrate photometric relationships. This is in order to investigate whether a faster tool to estimate atmospheric parameters can be provided. Methods: Temperatures and gravities of 30 calibrators, i.e. well-studied OB main sequence to giant stars in the solar neighbourhood, are compared to reddening-independent quantities of the Johnson and Strömgren photometric systems, assuming normal reddening. In addition, we examine the spectral and luminosity classification of the star sample and compute bolometric corrections. Results: Calibrations of temperatures and gravities are proposed for various photometric indices and spectral types. Once the luminosity of the stars is well known, effective temperatures can be determined at a precision of ~400 K for luminosity classes III/IV and ~800 K for luminosity class V. Furthermore, surface gravities can reach internal uncertainties as low as ~0.08 dex when using our calibration to the Johnson Q-parameter. Similar precision is achieved for gravities derived from the β-index and the precision is lower for both atmospheric parameters when using the Strömgren indices [c1] and [u - b] . In contrast, external uncertainties are larger for the Johnson than for the Strömgren calibrations. Our uncertainties are smaller than typical differences among other methods in the literature, reaching values up to ± 2000 K for temperature and ± 0.25 dex for gravity

  18. Observations of the O I lambda 7773 triplet in intermediate-type supergiants using a linear photodiode array

    NASA Astrophysics Data System (ADS)

    Hopkinson, G. R.; Humrich, A.

    1981-05-01

    Partially resolved spectra of the infrared oxygen triplet in A-G supergiants have been obtained with a new self-scanned photodiode array system. Curve of growth analyses indicate that the lines are formed in non-LTE. A line is identified at 7777.9 A which is strong in A supergiants and which will complicate the analysis of low resolution spectra. At a resolution of 0.45 A/diode the CN lines which appear in G8 and later stars are blended with the O I triplet rendering its equivalent width unreliable as a luminosity indicator.

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

    SciTech Connect

    Krticka, Jiri; Skalicky, Jan; Kubat, Jiri

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  1. INTEGRAL study of temporal properties of bright flares in Supergiant Fast X-ray Transients

    NASA Astrophysics Data System (ADS)

    Sidoli, L.; Paizis, A.; Postnov, K.

    2016-04-01

    We have characterized the typical temporal behaviour of the bright X-ray flares detected from the three Supergiant Fast X-ray Transients (SFXTs) showing the most extreme transient behaviour (XTE J1739-302, IGR J17544-2619, SAX J1818.6-1703). We focus here on the cumulative distributions of the waiting-time (time interval between two consecutive X-ray flares), and the duration of the hard X-ray activity (duration of the brightest phase of an SFXT outburst), as observed by INTEGRAL/IBIS in the energy band 17-50 keV. Adopting the cumulative distribution of waiting-times, it is possible to identify the typical time-scale that clearly separates different outbursts, each composed by several single flares at ˜ks time-scale. This allowed us to measure the duration of the brightest phase of the outbursts from these three targets, finding that they show heavy-tailed cumulative distributions. We observe a correlation between the total energy emitted during SFXT outbursts and the time interval covered by the outbursts (defined as the elapsed time between the first and the last flare belonging to the same outburst as observed by INTEGRAL). We show that temporal properties of flares and outbursts of the sources, which share common properties regardless different orbital parameters, can be interpreted in the model of magnetized stellar winds with fractal structure from the OB-supergiant stars.

  2. Wind variability in the Large Magellanic Cloud B(e) supergiant HD 34664

    NASA Technical Reports Server (NTRS)

    Schulte-Ladbeck, R. E.; Clayton, G. C.

    1993-01-01

    We present optical linear spectropolarimetry of the B(e) supergiant HD 34664. The polarization and position angle display significant spectral features which correspond to the H-alpha and H-beta emission lines. We use the line polarizations to separate the interstellar foreground polarization from the intrinsic polarization of HD 34664. The intrinsic polarization is consistent with electron scattering in a circumstellar disk seen at high inclination and provides further and independent evidence for the two-component wind model of the B(e) supergiants. We compare the polarization and spectrum of HD 34664 to observations published in the literature. In our data the continuum polarization is by a factor of two larger and the H-alpha line-to-continuum ratio is by a factor of at least four increased over previous observations. Since both the polarization and the line intensity are measures of the electron density in the stellar wind, we suggest that the observed variations can be attributed to a rise in the stellar mass-loss rate.

  3. Spectroscopic and Photometric Variability in the A0 Supergiant HR 1040

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    SciTech Connect

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

    2015-12-15

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

  5. 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.

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    SciTech Connect

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

    2010-09-10

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

  10. 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.

  11. IUE observations of HR 6902 - Effect of luminosity on supergiant chromospheres

    NASA Technical Reports Server (NTRS)

    Ahmad, Imad A.

    1990-01-01

    IUE observations of the most recently discovered Zeta Aurigae system, HR 6902, are reported to reveal profound differences in the spectrum of the chromosphere of the cool primary from those of all other Zeta Aurigae systems. Unlike its sister systems, HR 6902 shows evidence of neither strong wind nor an extended chromosphere for the cool primary. Instead, the spectrum is like that of a single blue dwarf. The most likely reason for this contrast to all other Zeta Aur systems observed with IUE is the lower luminosity of the HR 6902 primary: a type-II 'bright giant' as opposed to the type I (or Ib-II in the case of 22 Vul) 'supergiants' in the other Zeta Aur systems.

  12. Red-Supergiant and Supernova Rate Problems: Implication for the Relic Supernova Neutrino Spectrum

    NASA Astrophysics Data System (ADS)

    Hidaka, J.; Kajino, T.; Mathews, G. J.

    2016-08-01

    Direct observations of core-collapse supernovae (SNe) and their red supergiant (RSG) progenitors suggest that the upper mass limit of RSGs may be only about 16.5{--}18{M}ȯ , while the standard theoretical value is as much as 25{M}ȯ . We investigate the possibility that RSGs with m\\gt 16.5{--}18{M}ȯ end their lives as failed supernovae (fSNe) and analyze their contribution to the relic supernova neutrino spectrum. We show that adopting this mass limit simultaneously solves both the RSG problem and the supernova rate problem. In addition, energetic neutrinos that originated from fSNe are sensitive to the explosion mechanism, and in particular, to the nuclear equation of state (EOS). We show that this solution to the RSG problem might also be used to constrain the EOS for failed supernovae.

  13. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  15. Two supergiants in the Large Magellanic Cloud with thick dust shells

    NASA Technical Reports Server (NTRS)

    Elias, J. H.; Frogel, J. A.; Schwering, P. B. W.

    1986-01-01

    Ground-based observations from 0.6 to 20 microns have identified two luminous, evolved stars surrounded by thick dust shells among the Magellanic Cloud sources detected by the Infrared Astronomical Satellite. Their energy distributions resemble those of typical Galactic OH/IR stars, but they have bolometric magnitudes brighter than -9 and the small-amplitude variability of supergiants. One star, IRAS 04553 - 6825, has a special type of M7.5 and a dust shell which absorbs and reradiates roughly 75 percent of the star's luminosity; its radial velocity confirms its LMC membership. The second star, IRAS 05346 - 6949, has an even thicker dust shell, and the central star is not observable.

  16. A large population of red supergiants in the super star cluster NGC 1705-1

    NASA Astrophysics Data System (ADS)

    Martins, F.; Förster Schreiber, N. M.; Eisenhauer, F.; Lutz, D.

    2013-05-01

    We present near-infrared integral field observations of the super star cluster in the amorphous galaxy NGC1705. Data have been collected with SINFONI mounted on the VLT. Adaptive optics was used under good seeing conditions. Mosaics of the cluster and its immediate surrounding have been constructed. The cluster is not spatially resolved. Its radius is smaller than 2.85 ± 0.50pc. The K-band spectrum of the cluster is dominated by strong CO absorption bandheads. It is typical of a Galactic K 4-5 supergiant. Its age is estimated to be 12 ± 6Myr. The large error bar is rooted in the uncertainties of the input physics and ingredients of different evolutionary models.

  17. The Ultraviolet Spectral Morphology of a Sample of B Supergiants in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    McNeil, R. C.; Borchers, A. L.; Sonneborn, G.; Fahey, R. P.

    1995-05-01

    A study of the ultraviolet spectra of a sample of B supergiants in the Small Magellanic Cloud is being undertaken as a means of addressing some questions about the nature and evolution of massive stars. All spectra are new or archival low-dispersion SWP spectra (1200

  18. Detection of Rotational CO Emission From the Red-supergiants in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Matsuura, M.; Sargent, B.; Swinyard, B.; Yates, J. A.; Royer, P.; Barlow, M. J.; Boyer, M. L.; Decin, L.; Khouri, T.; Meixner, M.; van Loon, J. Th.; Woods, P. M.

    2015-12-01

    It is yet well understood how mass-loss rates from evolved stars depend on metallicities. With a half of the solar metallicity and the distance of only 50 kpc, the evolved stars of the Large Magellanic Cloud (LMC) are an ideal target for studying mass loss at low metallicity. We have obtained spectra of red-supergiants in the LMC, using the Hershel Space Observatory, detecting CO thermal lines fro J=6-5 up to 15-14 lines. Modelling CO lines with non-LTE Radiative transfer code suggests that CO lines intensities can be well explained with high gas-to-dust ratio, with no obvious reduction in mass-loss rate at the LMC. We conclude that the luminosities of the stars are dominant factors on mass-loss rates, rather than the metallicity.

  19. A semiempirical model for the red supergiant's wind in Zeta Aurigae systems

    NASA Technical Reports Server (NTRS)

    Kuin, N. P. M.; Ahmad, I. A.

    1989-01-01

    A semiempirical model for the wind in four Zeta Aur binary systems is developed, basing the analyses on the velocity function, nonthermal velocities, and upper limits to Ne/N(H) inferred from observations of the winds from the cool supergiants. The model assumes that the energy fluxes needed to drive the wind are supplied by Alfven waves, since the acoustic wave flux estimated from line broadening is too low. The damping scale length of the waves, is found to change from very small values near the star to larger values of the order of the local radius further out in the wind. The temperature structure and hydrogen ionization are derived for these models. Limits to the stellar magnetic field are found, as well as a necessary constraint for the existence of cool massive winds, suggesting that the dividing line in the H-R diagram is where this constraint is violated.

  20. Microvariability of line profiles in the spectra of OB stars: III. The supergiant ρ LEO

    NASA Astrophysics Data System (ADS)

    Kholtygin, A. F.; Fabrika, S. N.; Burlakova, T. E.; Valyavin, G. G.; Chuntonov, G. A.; Kudryavtsev, D. O.; Kang, D.; Yushkin, M. V.; Galazutdinov, G. A.

    2007-11-01

    We observed the bright supergiant ρ Leo (B1 lab) in January-February 2004 using the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). 47 spectra with high time resolution (4-10 min), signal-to-noise ratios 300-1000, and spectral resolutions 45 000-60 000 were obtained. We detected variability in the HeI, SiII, SiIII, and NII line profiles, which may be due to rotational modulation of the profiles and photospheric pulsations of ρ Leo. The possible influence of the stellar magnetic field on the line-profile variations is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  2. 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

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  4. TEXES OBSERVATIONS OF M SUPERGIANTS: DYNAMICS AND THERMODYNAMICS OF WIND ACCELERATION

    SciTech Connect

    Harper, Graham M.; Richter, Matthew J.; Ryde, Nils; Brown, Alexander; Brown, Joanna; Greathouse, Thomas K.; Strong, Shadrian

    2009-08-20

    We have detected [Fe II] 17.94 {mu}m and 24.52 {mu}m emission from a sample of M supergiants ({mu} Cep, {alpha} Sco, {alpha} Ori, CE Tau, AD Per, and {alpha} Her) using the Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility. These low opacity emission lines are resolved at R {approx_equal} 50, 000 and provide new diagnostics of the dynamics and thermodynamics of the stellar wind acceleration zone. The [Fe II] lines, from the first excited term (a {sup 4} F), are sensitive to the warm plasma where energy is deposited into the extended atmosphere to form the chromosphere and wind outflow. These diagnostics complement previous Kuiper Airborne Observatory and Infrared Space Observatory observations which were sensitive to the cooler and more extended circumstellar envelopes. The turbulent velocities of V{sub turb} {approx_equal} 12-13 km s{sup -1} observed in the [Fe II] a {sup 4} F forbidden lines are found to be a common property of our sample, and are less than that derived from the hotter chromospheric C II] 2325 A lines observed in {alpha} Ori, where V{sub turb} {approx_equal} 17-19 km s{sup -1}. For the first time, we have dynamically resolved the motions of the dominant cool atmospheric component discovered in {alpha} Ori from multiwavelength radio interferometry by Lim et al. Surprisingly, the emission centroids are quite Gaussian and at rest with respect to the M supergiants. These constraints combined with model calculations of the infrared emission line fluxes for {alpha} Ori imply that the warm material has a low outflow velocity and is located close to the star. We have also detected narrow [Fe I] 24.04 {mu}m emission that confirms Fe II is the dominant ionization state in {alpha} Ori's extended atmosphere.

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

    SciTech Connect

    Van Dyk, Schuyler D.; and others

    2012-09-10

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

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

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.; Chin, Chao-Wen

    1995-01-01

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

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

    SciTech Connect

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

    2014-04-20

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

  8. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  10. 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.

  11. Identification of red supergiants in nearby galaxies with mid-IR photometry

    NASA Astrophysics Data System (ADS)

    Britavskiy, N. E.; Bonanos, A. Z.; Mehner, A.; García-Álvarez, D.; Prieto, J. L.; Morrell, N. I.

    2014-02-01

    Context. The role of episodic mass loss in massive-star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. Aims: We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we employed mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. Methods: The method is based on mid-IR colors, using 3.6 μm and 4.5 μm photometry from archival Spitzer Space Telescope images of nearby galaxies and J-band photometry from 2MASS. We applied our criteria to two nearby star-forming dwarf irregular galaxies, Sextans A and IC 1613, selecting eight targets, which we followed-up with spectroscopy. Results: Our spectral classification and analysis yielded the discovery of two M-type supergiants in IC 1613, three K-type supergiants and one candidate F-type giant in Sextans A, and two foreground M giants. We show that the proposed criteria provide an independent way for identifying dusty evolved massive stars that can be extended to all nearby galaxies with available Spitzer/IRAC images at 3.6 μm and 4.5 μm. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio de El Roque de Los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma, and the 2.5 m du Pont telescope in operation at Las Campanas Observatory, Chile.Spectra 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/562/A75

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

    NASA Astrophysics Data System (ADS)

    Menon, Athira; Heger, Alexander

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Menon, Athira

    2015-08-01

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

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

    SciTech Connect

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

    2014-10-10

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

  15. Multi-Frequency Photometric Analyses of Rigel, the nearest Blue Supergiant and Supernova Progenitor

    NASA Astrophysics Data System (ADS)

    Stewart, Heather A.; Guinan, E. F.; Wasatonic, R.; Engle, S. G.; McCook, G. P.

    2009-01-01

    As the 7th brightest star and the most luminous star in the solar neighborhood Rigel (β Orionis) is a very intriguing object. This blue supergiant (B8 Iab; 0.12-mag; B-V = -0.03) has been distanced at 240 +/-35 pc by a Hipparcos parallax and has a resulting average absolute magnitude -6.7 mag.has been distanced at 240 +/-35 pc by Hipparcos parallax and an average absolute magnitude -6.7 mag. The following physical properties were determined via spectroscopic, photometric, and interferometric studies: L/Lo 66,000; Teff = 12,000 K; M/Mo 17 +/- 3; R/Ro 70; age 3-10 Myr. Interestingly Rigel has similar physical properties with the 12th-mag blue supergiant progenitor of SN 1987A: Sanduleak -69° 202a. Thus Rigel (along with its co-asterism Betelgeuse) are likely to be the nearest progenitors of a Type II supernova. Such a nearby explosion would have an apparent magnitude of -17 mag (nearly 100 full moons). We report on initial results of intensive photometry of Rigel being conducted with telescopes in Pennsylvania and Arizona. Also studied are two years of Hipparcos photometry. These datasets indicate brightness variations on nearly all time scales - from minutes to weeks. The photometry is being analyzed for possible periodicities using FFT and CLEAN-est routines provides by Peranso. Evidence of cyclic/periodic oscillations appears present in some of the datasets in addition to stochastic variations. We present the initial results and implications for probing the interior of this important star. Our study indicates that Rigel will be an excellent target for asteroseismic studies with MOST and the upcoming BRITE-Constellation Mission. Continuous high precision photometry from space could yield important information on the possible presence of g- and p- mode oscillations in this star. We acknowledge support for this research from NSF/RUI Grants AST05-07542 and AST05-07536.

  16. Dynamical mass of the O-type supergiant in ζ Orionis A

    NASA Astrophysics Data System (ADS)

    Hummel, C. A.; Rivinius, Th.; Nieva, M.-F.; Stahl, O.; van Belle, G.; Zavala, R. T.

    2013-06-01

    Aims: A close companion of ζ Orionis A was found in 2000 with the Navy Precision Optical Interferometer (NPOI), and shown to be a physical companion. Because the primary is a supergiant of type O, for which dynamical mass measurements are very rare, the companion was observed with NPOI over the full 7-year orbit. Our aim was to determine the dynamical mass of a supergiant that, due to the physical separation of more than 10 AU between the components, cannot have undergone mass exchange with the companion. Methods: The interferometric observations allow measuring the relative positions of the binary components and their relative brightness. The data collected over the full orbital period allows all seven orbital elements to be determined. In addition to the interferometric observations, we analyzed archival spectra obtained at the Calar Alto, Haute Provence, Cerro Armazones, and La Silla observatories, as well as new spectra obtained at the VLT on Cerro Paranal. In the high-resolution spectra we identified a few lines that can be associated exclusively to one or the other component for the measurement of the radial velocities of both. The combination of astrometry and spectroscopy then yields the stellar masses and the distance to the binary star. Results: The resulting masses for components Aa of 14.0 ± 2.2 M⊙ and Ab of 7.4 ± 1.1 M⊙ are low compared to theoretical expectations, with a distance of 294 ± 21 pc which is smaller than a photometric distance estimate of 387 ± 54 pc based on the spectral type B0III of the B component. If the latter (because it is also consistent with the distance to the Orion OB1 association) is adopted, the mass of the secondary component Ab of 14 ± 3 M⊙ would agree with classifying a star of type B0.5IV. It is fainter than the primary by about 2.2 ± 0.1 magnitudes in the visual. The primary mass is then determined to be 33 ± 10 M⊙. The possible reasons for the distance discrepancy are most likely related to physical

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

    SciTech Connect

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

    2013-03-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. Multiple, short-lived ``stellar prominences'' on O stars: the supergiant λ 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 λ4686 line of the O supergiant λ 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.

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

    SciTech Connect

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

    2014-06-10

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

  1. The eclipsing, double-lined, Of supergiant binary Cygnus OB2-B17

    NASA Astrophysics Data System (ADS)

    Stroud, V. E.; Clark, J. S.; Negueruela, I.; Roche, P.; Norton, A. J.; Vilardell, F.

    2010-02-01

    Context. Massive, eclipsing, double-lined, spectroscopic binaries are not common but are necessary to understand the evolution of massive stars as they are the only direct way to determine stellar masses. They are also the progenitors of energetic phenomena such as X-ray binaries and γ-ray bursts. Aims: We present a photometric and spectroscopic analysis of the candidate binary system Cyg OB2-B17 to show that it is indeed a massive evolved binary. Methods: We utilise V band and white-light photometry to obtain a light curve and period of the system, and spectra at different resolutions to calculate preliminary orbital parameters and spectral classes for the components. Results: Our results suggest that B17 is an eclipsing, double-lined, spectroscopic binary with a period of 4.0217±0.0004 days, with two massive evolved components with preliminary classifications of O7 and O9 supergiants. The radial velocity and light curves are consistent with a massive binary containing components with similar luminosities, and in turn with the preliminary spectral types and age of the association.

  2. Discovery of an Extraordinary Number of Red Supergiants in the Inner Galaxy

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    In this Letter, we present a search for Galactic red supergiant stars (RSGs) in the direction of the inner Galaxy. A total of 94 targets selected from the 2MASS and GLIMPSE I North catalogs—via their blue extinction-free Q1 and Q2 colors—were spectroscopically observed at infrared wavelengths (in the H- and K-bands at R ˜ 1000), and an extraordinary high detection rate of RSGs (\\gt 61%) was found. We identified spectroscopically 58 RSGs, based on their flat continua and large equivalent widths of the CO-band at 2.293 μm (EW > 45 Å). This increase corresponds to about 25% of previously known RSGs in the Galactic region 10° < l < 60°, -1.°1 < b < 1.°1. In order to confirm the location of the new RSGs in the inner Galaxy, distances were estimated for a subsample of 47 stars with the clump method and found to range from 3.6 ± 0.4 to 8.6 ± 0.7 kpc. The large new sample will allow us to investigate Galactic metallicity gradients as a function of galactocentric distances and azimuthal angles. Such information is currently an highly disputed issue to constrain models of Galaxy formation and evolution.

  3. Spectral Types of Red Supergiants in NGC 6822 and the Wolf-Lundmark-Melotte Galaxy

    NASA Astrophysics Data System (ADS)

    Levesque, Emily M.; Massey, Philip

    2012-07-01

    We present moderate-resolution spectroscopic observations of red supergiants (RSGs) in the low-metallicity Local Group galaxies NGC 6822 (Z = 0.4 Z ⊙) and Wolf-Lundmark-Melotte (WLM; Z = 0.1 Z ⊙). By combining these observations with reduction techniques for multislit data reduction and flux calibration, we are able to analyze spectroscopic data of 16 RSGs in NGC 6822 and spectrophotometric data of 11 RSGs in WLM. Using these observations, we determine spectral types for these massive stars, comparing them to Milky Way and Magellanic Cloud RSGs and thus extending observational evidence of the abundance-dependent shift of RSG spectral types to lower metallicities. In addition, we have uncovered two RSGs with unusually late spectral types (J000158.14-152332.2 in WLM, with a spectral type of M3 I, and J194453.46-144552.6 in NGC 6822, with a spectral type of M4.5 I) and a third RSG (J194449.96-144333.5 in NGC 6822) whose spectral type has varied from an M2.5 in 1997 to a K5 in 2008. All three of these stars could potentially be members of a recently discovered class of extreme RSG variables. This paper is based on data gathered with the 6.5 m Magellan telescopes located at Las Campanas, Chile.

  4. 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.

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

    SciTech Connect

    Levesque, Emily M.; Massey, Philip

    2012-07-15

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

  6. The evolutionary status of the bright high-latitude supergiant HD 190390

    NASA Astrophysics Data System (ADS)

    Reyniers, M.; Cuypers, J.

    2005-03-01

    Despite its mean apparent magnitude of mV = 6.39, the evolutionary status of HD 190390 (HR 7671), a luminous F-type supergiant at high galactic latitude, is still not very clear, but in most papers a post-AGB classification is assumed. New observational material has been obtained with four different instruments and is presented here. An extensive abundance analysis based on high resolution, high signal-to-noise NTT+EMMI spectra confirms the metal deficiency of this object ([Fe/H] = -1.6), together with a high lithium content (log ɛ(Li) = 1.9). A variability analysis based on Geneva photometry over seven years reveals beating with a period of ~3000 days. It is, however, not clear whether this beating is caused by a stable triplet, or it is the consequence of small changes in the main frequency. More recent data obtained with the HIPPARCOS satellite and the Mercator telescope not only confirm the main period, but also support the presence of a second periodicity of 11 days, which was also found in the Geneva photometry. A conclusive evolutionary status of this object is not given, but alternative to the UU Her (i.e. post-AGB) status, a W Vir classification is discussed. Based on observations collected at the European Southern Observatory, La Silla, Chile (programme 61.E-0426), and at the Observatorio del Roque de los Muchachos, La Palma, Spain.

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

    SciTech Connect

    Yukita, Mihoko; Swartz, Douglas A.

    2012-05-01

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

  8. Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles. II. CO line survey of evolved stars: derivation of mass-loss rate formulae

    NASA Astrophysics Data System (ADS)

    De Beck, E.; Decin, L.; de Koter, A.; Justtanont, K.; Verhoelst, T.; Kemper, F.; Menten, K. M.

    2010-11-01

    Context. The evolution of intermediate and low-mass stars on the asymptotic giant branch is dominated by their strong dust-driven winds. More massive stars evolve into red supergiants with a similar envelope structure and strong wind. These stellar winds are a prime source for the chemical enrichment of the interstellar medium. Aims: We aim to (1) set up simple and general analytical expressions to estimate mass-loss rates of evolved stars, and (2) from those calculate estimates for the mass-loss rates of the asymptotic giant branch, red supergiant, and yellow hypergiant stars in our galactic sample. Methods: The rotationally excited lines of carbon monoxide (CO) are a classic and very robust diagnostic in the study of circumstellar envelopes. When sampling different layers of the circumstellar envelope, observations of these molecular lines lead to detailed profiles of kinetic temperature, expansion velocity, and density. A state-of-the-art, nonlocal thermal equilibrium, and co-moving frame radiative transfer code that predicts CO line intensities in the circumstellar envelopes of late-type stars is used in deriving relations between stellar and molecular-line parameters, on the one hand, and mass-loss rate, on the other. These expressions are applied to our extensive CO data set to estimate the mass-loss rates of 47 sample stars. Results: We present analytical expressions for estimating the mass-loss rates of evolved stellar objects for 8 rotational transitions of the CO molecule and thencompare our results to those of previous studies. Our expressions account for line saturation and resolving of the envelope, thereby allowing accurate determination of very high mass-loss rates. We argue that, for estimates based on a single rotational line, the CO(2-1) transition provides the most reliable mass-loss rate. The mass-loss rates calculated for the asympotic giant branch stars range from 4 × 10-8 M⊙ yr-1 up to 8 × 10-5 M⊙ yr-1. For red supergiants they reach

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Bauer, Wendy Hagen

    1992-01-01

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

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

    SciTech Connect

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

    2014-07-01

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

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

    SciTech Connect

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

    2009-10-20

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

  13. Chemistry and kinematics of red supergiant stars in the young massive cluster NGC 2100

    NASA Astrophysics Data System (ADS)

    Patrick, L. R.; Evans, C. J.; Davies, B.; Kudritzki, R.-P.; Hénault-Brunet, V.; Bastian, N.; Lapenna, E.; Bergemann, M.

    2016-06-01

    We have obtained K-band Multi-Object Spectrograph (KMOS) near-IR spectroscopy for 14 red supergiant stars (RSGs) in the young massive star cluster NGC 2100 in the Large Magellanic Cloud (LMC). Stellar parameters including metallicity are estimated using the J-band analysis technique, which has been rigorously tested in the Local Universe. We find an average metallicity for NGC 2100 of [Z] = -0.43 ± 0.10 dex, in good agreement with estimates from the literature for the LMC. Comparing our results in NGC 2100 with those for a Galactic cluster (at Solar-like metallicity) with a similar mass and age we find no significant difference in the location of RSGs in the Hertzsprung-Russell diagram. We combine the observed KMOS spectra to form a simulated integrated-light cluster spectrum and show that, by analysing this spectrum as a single RSG, the results are consistent with the average properties of the cluster. Radial velocities are measured for the targets and the dynamical properties are estimated for the first time within this cluster. The data are consistent with a flat velocity dispersion profile, and with an upper limit of 3.9 kms-1, at the 95 per cent confidence level, for the velocity dispersion of the cluster. However, the intrinsic velocity dispersion is unresolved and could, therefore, be significantly smaller than the upper limit reported here. An upper limit on the dynamical mass of the cluster is derived as Mdyn ≤ 15.2 × 104 M⊙ assuming virial equilibrium.

  14. Dense molecular clumps associated with the Large Magellanic Cloud supergiant shells LMC 4 and LMC 5

    SciTech Connect

    Fujii, Kosuke; Mizuno, Norikazu; Minamidani, Tetsuhiro; Onishi, Toshikazu; Muraoka, Kazuyuki; Kawamura, Akiko; Muller, Erik; Tatematsu, Ken'ichi; Hasegawa, Tetsuo; Miura, Rie E.; Ezawa, Hajime; Dawson, Joanne; Tosaki, Tomoka; Sakai, Takeshi; Tsukagoshi, Takashi; Tanaka, Kunihiko; 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. {sup 12}CO (J = 3-2, 1-0) and {sup 13}CO(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(H{sub 2})) of the clumps are distributed from low to high density (10{sup 3}-10{sup 5} cm{sup –3}) and their kinetic temperatures (T {sub kin}) are typically high (greater than 50 K). These clumps seem to be in the early stages of star formation, as also indicated from the distribution of Hα, young stellar object candidates, and IR emission. We found that the N48 region is located in the high column density H I envelope at the interface of the two SGSs and the star formation is relatively evolved, whereas the N49 region is associated with LMC 5 alone and the star formation is quiet. The clumps in the N48 region typically show high n(H{sub 2}) and T {sub 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.

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

    SciTech Connect

    Fiocchi, M.; Bazzano, A.; Natalucci, L.; Ubertini, P.; Sguera, V.; Bassani, L.; Bird, A. J.

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    2011-01-20

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

  18. Hα Variability in the A0 Ia-Type Supergiant HR 1040

    NASA Astrophysics Data System (ADS)

    Morrison, N. D.; Gordon, K. D.

    1995-12-01

    HR 1040 (= HD 21389) is a well-known example of a luminous star with mass loss, photometric and radial-velocity variability, and a variable Hα profile. Caplinger (1991, M. S. thesis, U. Toledo) found that the Hα profile shows, at various times, different morphologies: P Cygni, inverse P Cygni, and Type III P Cygni (emission on both sides of the absorption). This result indicates that this star's wind is not steady and/or not spherically symmetric. We studied 43 CCD echelle spectra obtained between 1993 Sep. and 1994 Dec. with the 1-m telescope of Ritter Observatory. The spectral resolution of this material is 0.23 Angstroms at lambda 5800, and the continuum SNR is usually comfortably above 100 in an exposure time of 20 min or less. The spectral coverage consists of 9 disjoint 70- Angstroms regions in the yellow and red; features of interest in these spectra are Hα , He I lambda 5876, and Si II lambda lambda 6347, 6371. In addition to confirming the morphological variability found by Caplinger, our data show two episodes of dramatic increases in the width and the equivalent width of the absorption component of Hα , with the equivalent width attaining values as large as 2 Angstroms, as compared to a baseline value around 0.5 Angstroms. During these episodes, the absorption feature often showed two or more sub-components. In addition, the equivalent width of Si II lambda 6347 increased by amounts up to 50%. Presumably, these events can be interpreted as episodes of enhanced mass loss. Collection and analysis of spectra of this star are continuing at Ritter Observatory. If this star is typical of A-type supergiants in the variability of its Hα profile, our results can be used to assess the accuracy of distance estimates to external galaxies based on mass loss as a luminosity indicator in these stars (Kudritzki et al. 1992, A&A 257, 655).

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  20. 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 α 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.

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

    SciTech Connect

    Lopatin, N.

    1996-12-31

    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, Astrachan and Orenburg. The gas reserves in these basins exceed 70 x 10{sup 12} m{sup 3} and about 65% of them concentrated in supergiant fields. Among the geological prerequisites for largest gas accumulations note big size of trap (Urengoi 40x300 km{sup 2}; Astrachan l80x200 km{sup 2}), anticline type of tectonic structure (swell, megaswell, dome, arch) with amplitude from 110 m to 800 in. These tectonic structure were active long time include the latest period. The main gas productive reservoirs are slightly consulted non-marine sandstones of Cenomanian or Middle Jurassic ages (West Siberia and Barents Sea) or Middle Carboniferous reef carbonate buildups (Northern Caspian basin). The next geochemical parameters controlled of the gas accumulation histories: (1) West Siberia and Barents Sea regions gas genetically connect with dispersed or concentrated non-marine coal type kerogen distributed into productive complex under lower maturity conditions (before or early oil window zone). This is dry gas almost pure methane with {delta}{sup 13} C{sub 1} between -44,40{per_thousand}. In this case we observe widely distributed mainly sandstones reservoirs at same time gas source rocks also; (2) the Northern Caspian basin found supergiant wet gas-condensate accumulations into local distributed reef carbonate buildups. Gas source rocks is marine kerogen type II, which has a low concentration in marlaceous facies. It is gas high maturity zone.

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

    SciTech Connect

    Lopatin, N. )

    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, Astrachan and Orenburg. The gas reserves in these basins exceed 70 x 10[sup 12] m[sup 3] and about 65% of them concentrated in supergiant fields. Among the geological prerequisites for largest gas accumulations note big size of trap (Urengoi 40x300 km[sup 2]; Astrachan l80x200 km[sup 2]), anticline type of tectonic structure (swell, megaswell, dome, arch) with amplitude from 110 m to 800 in. These tectonic structure were active long time include the latest period. The main gas productive reservoirs are slightly consulted non-marine sandstones of Cenomanian or Middle Jurassic ages (West Siberia and Barents Sea) or Middle Carboniferous reef carbonate buildups (Northern Caspian basin). The next geochemical parameters controlled of the gas accumulation histories: (1) West Siberia and Barents Sea regions gas genetically connect with dispersed or concentrated non-marine coal type kerogen distributed into productive complex under lower maturity conditions (before or early oil window zone). This is dry gas almost pure methane with [delta][sup 13] C[sub 1] between -44,40[per thousand]. In this case we observe widely distributed mainly sandstones reservoirs at same time gas source rocks also; (2) the Northern Caspian basin found supergiant wet gas-condensate accumulations into local distributed reef carbonate buildups. Gas source rocks is marine kerogen type II, which has a low concentration in marlaceous facies. It is gas high maturity zone.

  3. 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.; Cotera, A.; Dong, H.; Wang, Q. D.; Morris, M. R.; Lang, C.

    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.

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

    DOE PAGES

    Annis, J.

    2016-05-27

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  6. 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, Kris; Grammer, Skyler; Kneeland, Nathan; Martin, John C.; Weis, Kerstin; Burggraf, Birgitta

    2013-08-01

    The progenitors of Type IIP supernovae (SNe) have an apparent upper limit to their initial masses of about 20 M ⊙, 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. 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 estimate the amount of mass they have shed and discuss their wind parameters and mass loss rates, which range from a few × 10-6 to 10-4 M ⊙ yr-1. On an H-R diagram, these stars will overlap the region of the luminous blue variables (LBVs) at maximum light; however, the warm hypergiants are not LBVs. Their non-spherical winds are not optically thick, and they have not exhibited any significant variability. We suggest, however, that the warm hypergiants may be the progenitors of the "less luminous" LBVs such as R71 and even SN1987A. 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

  7. Coronal Temperature and Emission Measure Distributions for he Active G Supergiant Beta Dra and other ASCA Projects

    NASA Technical Reports Server (NTRS)

    Brown, Alexander

    1998-01-01

    This NASA grant supported my ASCA observing and data analysis programs during AOs 1-4. This research involved four Guest Observer projects. Analysis of data from all four programs has been completed. This grant included the following ASCA GO programs: AO1 - "Coronal Temperature and Emission Measure Distributions for the Active G Supergiant Beta Dra" AO2 - "Contemporaneous ASCA, EUVE, IUE, and VLA/AT Observations of Atmospheric Structure of the RS CVn Binary HR1099". AO3 - "Coronal Temperature and Emission Measure Distributions for the hybrid-chromosphere star alpha TrA". AO4-"Activity on the edge of convection: The atmosphere of Canopus (alpha Car, FO Ib-II)".

  8. An optical and near-IR spectroscopic study of the extreme P Cygni-type supergiant HDE 316285

    NASA Astrophysics Data System (ADS)

    Hillier, D. J.; Crowther, P. A.; Najarro, F.; Fullerton, A. W.

    1998-12-01

    A detailed study of the Galactic P Cygni-type supergiant HDE 316285, based on high quality optical (AAT, MSO, CTIO) and near-IR (UKIRT, CFHT, CTIO) spectroscopy, is presented. As has been noted previously, its spectrum is dominated by H, He I, and Fe Ii P Cygni profiles. Emission lines due to N I, N Ii, [N Ii], O I, Na I, Mg Ii, Al Ii, Ca Ii, Si Ii, Si Iii, Fe Ii and [Fe Ii] can also be readily identified. Many of the metal lines are produced by continuum fluorescence. The rich N spectrum, the paucity of the O spectrum (only 2 O lines can be identified), and the apparent absence of emission due to C, strongly suggest that the atmosphere of the star is contaminated by CNO processed material. A comparison of the spectrum of HDE 316285 with P Cygni and He 3-519 is presented. From a spectral analysis using the non-LTE atmosphere code of Hillier (1991), and assuming a distance of 1.85 kpc, our preferred model for HDE 316285 has the following parameters: T_* = 15 kK, log L_* / L_sun = 5.44, spose M = 2.4 x 10(-4) Msun yr(-1) , v_∞ = 410 {km s(-1) }, E_B-V=1.81 mag, and H/He ~ 1.5 by number. Due to the low degree of He ionization the derived H/He abundance ratio and mass-loss rate are strongly coupled. Models with H/He=10 to 0.5 are equally capable of explaining the H and He I\\ spectrum provided the mass-loss rate is scaled according to the approximate formula spose M = 9.1 + 26.3 (He/H -0.1) x 10(-5) M_{\\odot}yr. Preliminary work, however, indicates that a solar H/He ratio can be ruled out on the basis of line strengths of other species - particularly N, Mg, Al. The stellar wind from HDE 316285 is more extreme than P Cygni with a performance number (= ratio of wind momentum to radiative momentum) 30 times greater. The low H/He abundance ratio and high N/He abundance ratio confirms that HDE 316285 is evolved. Although we find no evidence in the literature for photometric variability, we find strong evidence for significant spectral variability. Because of the spectral

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

    SciTech Connect

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

    2015-02-01

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

  10. Studies of Evolved Star Mass Loss: GRAMS Modeling of Red Supergiant and Asymptotic Giant Branch Stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, S.; Riebel, D.; Boyer, M.; Meixner, M.

    2012-01-01

    As proposed in our NASA Astrophysics Data Analysis Program (ADAP) proposal, my colleagues and I are studying mass loss from evolved stars. Such stars lose their own mass in their dying stages, and in their expelled winds they form stardust. To model mass loss from these evolved stars, my colleagues and I have constructed GRAMS: the Grid of Red supergiant and Asymptotic giant branch star ModelS. These GRAMS radiative transfer models are fit to optical through mid-infrared photometry of red supergiant (RSG) stars and asymptotic giant branch (AGB) stars. I will discuss our current studies of mass loss from AGB and RSG stars in the Small Magellanic Cloud (SMC), fitting GRAMS models to the photometry of SMC evolved star candidates identified from the SAGE-SMC (PI: K. Gordon) Spitzer Space Telescope Legacy survey. This work will be briefly compared to similar work we have done for the LMC. I will also discuss Spitzer Infrared Spectrograph (IRS) studies of the dust produced by AGB and RSG stars in the LMC. BAS is grateful for support from the NASA-ADAP grant NNX11AB06G.

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

    SciTech Connect

    Ohyama, Youichi; Hota, Ananda

    2013-04-20

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

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

    NASA Astrophysics Data System (ADS)

    Ostrowski, J.; Daszyńska-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 κ 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.

  13. 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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  16. The weak magnetic field of the O9.7 supergiant ζOrionisA

    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 ζOrionisA (ζOriA), using spectropolarimetric observations obtained with NARVAL at the 2-m Télescope Bernard Lyot atop Pic du Midi (France). ζOriA is the third O star known to host a magnetic field (along with θ1OriC and HD191612), and the first detection on a `normal' rapidly rotating O star. The magnetic field of ζOriA 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 ζOriA 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 ζOriA 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 ζOriA 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 ζOriA with respect to θ1OriC 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 ζOriA is not a fossil remnant (as opposed to that of θ1 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  18. The B Supergiant Discontinuous Drop in X-ray Luminosity at Spectra Type B1

    NASA Astrophysics Data System (ADS)

    Waldron, Wayne L.; Cassinelli, J.; Oskinova, L.; Lamers, H.

    2007-12-01

    At spectral type B1, the stellar winds of B supergiants (SGs) display a discontinuous drop in their observed terminal velocities which is referred to as the "bi-stability jump". Similarly, Einstein satellite observations of B SG also revealed evidence for a discontinuous drop in their observed X-ray luminosities at B1. Since the X-ray emission is believed to arise from stellar wind shock structures, B SGs provide an excellent laboratory for testing the still uncertain relationships between the radiation forces, wind properties, and the resultant X-ray emission. This interesting coincidence at spectral type B1 has not been explored in depth mostly due to the insufficient number of B SGs with high S/N X-ray observations. To explore the significance and interconnection of the X-ray and wind discontinuous drops, we obtained high S/N XMM-Newton EPIC observations of a sample of B SGs in the vicinity of spectral type B1. The good sensitivity of EPIC allows us to carry out a thorough X-ray spectral analysis of these stars and extract well constrained X-ray parameters. Our observations confirmed the B1 discontinuous drop in X-ray luminosity by a factor of 4, and this X-ray drop is found to coincide with the same effective temperature of the wind bi-stability jump. Although current shock X-ray emission models are found to be roughly consistent with predicting the observed drop in the X-ray luminosity, our detailed X-ray analyses have revealed several discrepancies with these models. For example, since shock produced X-ray temperatures scale with the flow velocity squared, we expected to see a dramatic drop in the spectral hardness across the discontinuity due to the drop in wind speed, but this is not observed. We discuss the significance of our X-ray results with regards to understanding the wind-dynamics of B SGs and suggest alternative X-ray source models.

  19. 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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  2. DISENTANGLING THE SYSTEM GEOMETRY OF THE SUPERGIANT FAST X-RAY TRANSIENT IGR J11215-5952 WITH SWIFT

    SciTech Connect

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

    2009-05-10

    IGR J11215-5952 is a hard X-ray transient source discovered in 2005 April with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) and a member of the new class of high-mass X-ray binaries, the supergiant fast X-ray transients (SFXTs). While INTEGRAL and Rossi X-Ray Timing Explorer observations have shown that the outbursts occur with a periodicity of {approx}330 days, Swift data have recently demonstrated that the true outburst period is {approx}165 days. IGR J11215-5952 is the first discovered SFXT displaying periodic outbursts, which are possibly related to the orbital period. The physical mechanism responsible for the X-ray outbursts in SFXTs is still debated. The main hypotheses proposed to date involve the structure of the companion wind or gated mechanisms related to the properties of the compact object. We test our proposed model which explains the outbursts from SFXTs as being due to the passage of the neutron star inside the equatorially enhanced wind from the supergiant companion. We performed a Guest Investigator observation with Swift that lasted 20 ks and several follow-up Target of Opportunity (ToO) observations, for a total of {approx}32 ks, during the expected 'apastron' passage (defined assuming an orbital period of {approx}330 days), between 2008 June 16 and July 4. The characteristics of this 'apastron' outburst are quite similar to those previously observed during the 'periastron' outburst of 2007 February 9. The mean spectrum of the bright peaks can be fitted with an absorbed power-law model with a photon index of 1 and an absorbing column of {approx}10{sup 22} cm{sup -2}. This outburst reached luminosities of {approx}10{sup 36} erg s{sup -1} (1-10 keV), comparable with those measured in 2007. The light curve can be modeled with the parameters obtained by Sidoli et al. for the 2007 February 9 outburst, although some differences can be observed in its shape. The properties of the rise to this new outburst and the comparison with the

  3. Spatially resolved dusty torus toward the red supergiant WOH G64 in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.; Driebe, T.; Hofmann, K.-H.; Weigelt, G.; Wittkowski, M.

    2008-06-01

    Aims: We present N-band spectro-interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud (LMC) using MIDI at the Very Large Telescope Interferometer (VLTI). While the very high luminosity (˜ 5 × 105 L⊙) previously estimated for WOH G64 suggests that it is a very massive star with an initial mass of ~40 M⊙, its low effective temperature (~3200 K) is in serious disagreement with the current stellar evolution theory. Methods: WOH G64 was observed with VLTI/MIDI using the UT2-UT3 and UT3-UT4 baseline configurations. Results: The dust envelope around WOH G64 has been spatially resolved with a baseline of ~60 m - the first MIDI observations to resolve an individual stellar source in an extragalactic system. The observed N-band visibilities show a slight decrease from 8 to ~10 μm and a gradual increase longward of ~10 μm, reflecting the 10 μm silicate feature in self-absorption. This translates into a steep increase of the uniform-disk diameter from 8 to 10 μm (from 18 to 26 mas) and a roughly constant diameter above 10 μm. The visibilities measured at four position angles differing by ~60° but at approximately the same baseline length (~60 m) do not show a noticeable difference, suggesting that the object appears nearly centrosymmetric. The observed N-band visibilities and spectral energy distribution can be reproduced by an optically and geometrically thick silicate torus model viewed close to pole-on. The luminosity of the central star is derived to be ˜ 2.8 × 105 L⊙, which is by a factor of 2 lower than the previous estimates based on spherical models. We also identify the H2O absorption features at 2.7 and 6 μm in the spectra obtained with the Infrared Space Observatory and the Spitzer Space Telescope. The 2.7 μm feature originates in the photosphere and/or the extended molecular layers, while the 6 μm feature is likely to be of circumstellar origin. Conclusions: The lower luminosity newly derived from our MIDI

  4. Exploring the circumstellar disk-like structure of the B[e] supergiant LHA 120-S 73

    NASA Astrophysics Data System (ADS)

    Torres, A. F.; Cidale, L.; Kraus, M.; Arias, M. L.; Maravelias, G.; Borges Fernandes, M.; Vallverdú, R.

    2016-08-01

    The Large Magellanic Cloud hosts the peculiar B8-type star LHA 120-S 73. Belonging to the B[e] supergiant group, this star is surrounded by large amounts of material which forms a circumstellar disk-like structure, seen more or less pole-on. Within its dense and cool circumstellar disk, molecules form and dust condensates. Based on medium and high-resolution optical and infrared spectroscopic data, we study the structure, kinematics and physical properties of the disk using different tracers, as the emission lines of [Oi] and [Caii] for the innermost gaseous atomic region and the first-overtone bands of CO for the inner border of the molecular disk. We also analyze near-infrared mid-resolution spectra to search for the presence of other molecules and mid-infrared low-resolution spectroscopic observations to study the composition of the dust component.

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

    SciTech Connect

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

    2015-10-20

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

  6. 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.

  7. 2D Radiation-hydrodynamic Simulations of Supernova Shock Breakout in Bipolar Explosions of a Blue Supergiant Progenitor

    NASA Astrophysics Data System (ADS)

    Suzuki, Akihiro; Maeda, Keiichi; Shigeyama, Toshikazu

    2016-07-01

    A two-dimensional special relativistic radiation-hydrodynamics code is developed and applied to numerical simulations of supernova shock breakout in bipolar explosions of a blue supergiant. Our calculations successfully simulate the dynamical evolution of a blast wave in the star and its emergence from the surface. Results of the model with spherical energy deposition show a good agreement with previous simulations. Furthermore, we calculate several models with bipolar energy deposition and compare their results with the spherically symmetric model. The bolometric light curves of the shock breakout emission are calculated by a ray-tracing method. Our radiation-hydrodynamic models indicate that the early part of the shock breakout emission can be used to probe the geometry of the blast wave produced as a result of the gravitational collapse of the iron core.

  8. Red Supergiants as Cosmic Abundance Probes: The First Direct Metallicity Determination of NGC 4038 in the Antennae

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    SciTech Connect

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

    1990-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  12. SN 2009ip and SN 2010mc: core-collapse Type IIn supernovae arising from blue supergiants

    NASA Astrophysics Data System (ADS)

    Smith, Nathan; Mauerhan, Jon C.; Prieto, Jose L.

    2014-02-01

    The recent supernova (SN) known as SN 2009ip had dramatic precursor eruptions followed by an even brighter explosion in 2012. Its pre-2012 observations make it the best documented SN progenitor in history, but have fuelled debate about the nature of its 2012 explosion - whether it was a true SN or some type of violent non-terminal event. Both could power shock interaction with circumstellar material (CSM), but only a core-collapse SN provides a self-consistent explanation. The persistent broad emission lines in the spectrum require a relatively large ejecta mass, and a corresponding kinetic energy of at least 1051 erg, while the faint 2012a event is consistent with published models of core-collapse SNe from compact (˜60 R⊙) blue supergiants. The light curves of SN 2009ip and another Type IIn, SN 2010mc, were nearly identical; we demonstrate that their spectra match as well, and that both are standard SNe IIn. Our observations contradict the recent claim that the late-time spectrum of SN 2009ip is returning to its progenitor's luminous blue variable-like state, and we show the that late-time spectra of SN 2009ip closely resemble the spectra of SN 1987A. Moreover, SN 2009ip's changing Hα equivalent width after explosion matches behaviour typically seen in core-collapse SNe IIn. Several key facts about SN 2009ip and SN 2010mc argue strongly in favour of a core-collapse interpretation, and make a non-terminal 1050 erg event implausible. The most straightforward and self-consistent interpretation is that SN 2009ip was an initially faint core-collapse explosion of a blue supergiant that produced about half as much 56Ni as SN 1987A, with most of the peak luminosity from CSM interaction.

  13. PTF11iqb: cool supergiant mass-loss that bridges the gap between Type IIn and normal supernovae

    NASA Astrophysics Data System (ADS)

    Smith, Nathan; Mauerhan, Jon C.; Cenko, S. Bradley; Kasliwal, Mansi M.; Silverman, Jeffrey M.; Filippenko, Alexei V.; Gal-Yam, Avishay; Clubb, Kelsey I.; Graham, Melissa L.; Leonard, Douglas C.; Horst, J. Chuck; Williams, G. Grant; Andrews, Jennifer E.; Kulkarni, Shrinivas R.; Nugent, Peter; Sullivan, Mark; Maguire, Kate; Xu, Dong; Ben-Ami, Sagi

    2015-05-01

    The supernova (SN) PTF11iqb was initially classified as a Type IIn event caught very early after explosion. It showed narrow Wolf-Rayet (WR) spectral features on day 2 (as in SN 1998S and SN 2013cu), but the narrow emission weakened quickly and the spectrum morphed to resemble Types II-L and II-P. At late times, Hα exhibited a complex, multipeaked profile reminiscent of SN 1998S. In terms of spectroscopic evolution, we find that PTF11iqb was a near twin of SN 1998S, although with somewhat weaker interaction with circumstellar material (CSM) at early times, and stronger interaction at late times. We interpret the spectral changes as caused by early interaction with asymmetric CSM that is quickly (by day 20) enveloped by the expanding SN ejecta photosphere, but then revealed again after the end of the plateau when the photosphere recedes. The light curve can be matched with a simple model for CSM interaction (with a mass-loss rate of roughly 10-4 M⊙ yr-1) added to the light curve of a normal SN II-P. The underlying plateau requires a progenitor with an extended hydrogen envelope like a red supergiant at the moment of explosion, consistent with the slow wind speed (<80 km s-1) inferred from narrow Hα emission. The cool supergiant progenitor is significant because PTF11iqb showed WR features in its early spectrum - meaning that the presence of such WR features does not necessarily indicate a WR-like progenitor. Overall, PTF11iqb bridges SNe IIn with weaker pre-SN mass-loss seen in SNe II-L and II-P, implying a continuum between these types.

  14. 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; Przybilla, Norbert; Gieren, Wolfgang; Pietrzynski, Grzegorz E-mail: urbaneja@ifa.hawaii.edu E-mail: bresolin@ifa.hawaii.edu E-mail: wgieren@astro-udec.cl

    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.

  15. Super-giant magnetoresistance at room-temperature in copper nanowires due to magnetic field modulation of potential barrier heights at nanowire-contact interfaces.

    PubMed

    Hossain, Md I; Maksud, M; Palapati, N K R; Subramanian, A; Atulasimha, J; Bandyopadhyay, S

    2016-07-29

    We have observed a super-giant (∼10 000 000%) negative magnetoresistance at 39 mT field in Cu nanowires contacted with Au contact pads. In these nanowires, potential barriers form at the two Cu/Au interfaces because of Cu oxidation that results in an ultrathin copper oxide layer forming between Cu and Au. Current flows when electrons tunnel through, and/or thermionically emit over, these barriers. A magnetic field applied transverse to the direction of current flow along the wire deflects electrons toward one edge of the wire because of the Lorentz force, causing electron accumulation at that edge and depletion at the other. This lowers the potential barrier at the accumulated edge and raises it at the depleted edge, causing a super-giant magnetoresistance at room temperature.

  16. The dynamical state of the atmosphere of the supergiant Alpha Cygni (A2 Iae) derived from high-resolution ultraviolet spectra

    NASA Astrophysics Data System (ADS)

    Boer, B.; de Jager, C.; Nieuwenhuijzen, H.

    1988-03-01

    In order to study the apparent near-instability of supergiant atmospheres, high-resolution BUSS (Balloon-borne Ultraviolet Stellar Spectometer) spectra of the supergiant Alpha Cyg have been investigated. Equivalent widths of lines yield the variation of the line-of-sight microturbulent velocity component zeta(mu) with optical depth tau. At tau(5) = 0.1, zeta(mu) equal to the velocity of sound is found. The consequent turbulent acceleration is directed outward. It increases outward and is about half the effective acceleration at tau(5) = 0.01. The macroturbulent velocity profile is double peaked with upward and downward velocities of 14 km/s. It is suggested that these motions are stochastic pulsations of large elements. At any time there are 30 to 40 such elements on the visible disk.

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

    NASA Astrophysics Data System (ADS)

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

    2004-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.

    2000-01-01

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

  20. Resolving the dusty circumstellar environment of the A[e] supergiant HD 62623 with the VLTI/MIDI

    NASA Astrophysics Data System (ADS)

    Meilland, A.; Kanaan, S.; Borges Fernandes, M.; Chesneau, O.; Millour, F.; Stee, Ph.; Lopez, B.

    2010-03-01

    Context. B[e] stars are hot stars surrounded by circumstellar gas and dust which is responsible for the presence of emission lines and IR-excess in their spectra. How dust can be formed in this highly illuminated and diluted environment remains an open issue. Aims: HD 62623 is one of the very few A-type supergiants showing the B[e] phenomenon. We studied the geometry of its circumstellar envelope in the mid-infrared using long-baseline interferometry, which is the only observing technique able to spatially resolve objects smaller than a few tens of milliarcseconds. Methods: We obtained nine calibrated visibility measurements between October 2006 and January 2008 using the VLTI/MIDI instrument in SCI-PHOT mode and PRISM spectral dispersion mode with projected baselines ranging from 13 to 71 m and with various position angles (PA). We used geometrical models and physical modeling with a radiative transfer code to analyze these data. Results: The dusty circumstellar environment of HD 62623 is partially resolved by the VLTI/MIDI, even with the shortest baselines. The environment is flattened (a/b~1.3±0.1) and can be separated into two components: a compact one whose extension grows from 17 mas at 8 μm to 30 mas at 9.6 μm and stays almost constant up to 13 μm, and a more extended one that is over-resolved even with the shortest baselines. Using the radiative transfer code MC3D, we managed to model HD 62623's circumstellar environment as a dusty disk with an inner radius of 3.85±0.6 AU, an inclination angle of 60±10°, and a mass of 2 × 10-7 M_⊙. Conclusions: It is the first time that the dusty disk inner rim of a supergiant star exhibiting the B[e] phenomenon is significantly constrained. The inner gaseous envelope likely contributes up to 20% to the total N band flux and acts like a reprocessing disk. Finally, the hypothesis of a stellar wind deceleration by the companion's gravitational effects remains the most probable case since the bi-stability mechanism

  1. 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 μm 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 μm 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 μm 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 μm 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

  2. Herschel SPIRE and PACS observations of the red supergiant VY CMa: analysis of the molecular line spectra

    NASA Astrophysics Data System (ADS)

    Matsuura, Mikako; Yates, J. A.; Barlow, M. J.; Swinyard, B. M.; Royer, P.; Cernicharo, J.; Decin, L.; Wesson, R.; Polehampton, E. T.; Blommaert, J. A. D. L.; Groenewegen, M. A. T.; Van de Steene, G. C.; van Hoof, P. A. M.

    2014-01-01

    We present an analysis of the far-infrared and submillimetre molecular emission-line spectrum of the luminous M-supergiant VY CMa, observed with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer for Herschel spectrometers aboard the Herschel Space Observatory. Over 260 emission lines were detected in the 190-650 μm SPIRE Fourier Transform Spectrometer spectra, with one-third of the observed lines being attributable to H2O. Other detected species include CO, 13CO, H_2^{18}O, SiO, HCN, SO, SO2, CS, H2S and NH3. Our model fits to the observed 12CO and 13CO line intensities yield a 12C/13C ratio of 5.6 ± 1.8, consistent with measurements of this ratio for other M-supergiants, but significantly lower than previously estimated for VY CMa from observations of lower-J lines. The spectral line energy distribution for 20 SiO rotational lines shows two temperature components: a hot component at ˜1000 K, which we attribute to the stellar atmosphere and inner wind, plus a cooler ˜200 K component, which we attribute to an origin in the outer circumstellar envelope. We fit the line fluxes of 12CO, 13CO, H2O and SiO, using the SMMOL non-local thermodynamic equilibrium (LTE) line transfer code, with a mass-loss rate of 1.85 × 10-4 M⊙ yr-1 between 9R* and 350R*. We also fit the observed line fluxes of 12CO, 13CO, H2O and SiO with SMMOL non-LTE line radiative transfer code, along with a mass-loss rate of 1.85 × 10-4 M⊙ yr-1. To fit the high rotational lines of CO and H2O, the model required a rather flat temperature distribution inside the dust condensation radius, attributed to the high H2O opacity. Beyond the dust condensation radius the gas temperature is fitted best by an r-0.5 radial dependence, consistent with the coolant lines becoming optically thin. Our H2O emission-line fits are consistent with an ortho:para ratio of 3 in the outflow.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  5. 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 Δ V r ≤ 8 km s-1.

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

    SciTech Connect

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

    2013-12-01

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

  7. Mass Loss from Dusty AGB and Red Supergiant Stars in the Magellanic Clouds and in the Galaxy

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel

    2016-01-01

    Asymptotic giant branch (AGB) and red supergiant (RSG) stars are evolved stars that eject large parts of their mass in outflows of dust and gas. As part of an ongoing effort to measure mass loss from evolved stars in our Galaxy and in the Magellanic Clouds, we are modeling mass loss from AGB and RSG stars in these galaxies. Our approach is twofold. We pursue radiative transfer modeling of the spectral energy distributions (SEDs) of AGB and RSG stars in the Large Magellanic Cloud (LMC), in the Small Magellanic Cloud (SMC), and in the Galactic bulge and in globular clusters of the Milky Way. We are also constructing detailed dust opacity models of AGB and RSG stars in these galaxies for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). Our sample of infrared spectra largely comes from Spitzer-IRS observations. The detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs. We seek to determine how mass loss from these evolved stars depends upon the metallicity of their host environments. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

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

    SciTech Connect

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

    2012-06-01

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

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

    SciTech Connect

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

    2014-04-10

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

  10. The Vast Population of Wolf-Rayet and Red Supergiant Stars in M101. I. Motivation and First Results

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Messina, Sergio

    2007-10-01

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

  12. Imaging the dynamical atmosphere of the red supergiant Betelgeuse in the CO first overtone lines with VLTI/AMBER

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.; Weigelt, G.; Millour, F.; Hofmann, K.-H.; Driebe, T.; Schertl, D.; Chelli, A.; Massi, F.; Petrov, R.; Stee, Ph.

    2011-05-01

    Aims: We present one-dimensional aperture synthesis imaging of the red supergiant Betelgeuse (α Ori) with VLTI/AMBER. We reconstructed for the first time one-dimensional images in the individual CO first overtone lines. Our aim is to probe the dynamics of the inhomogeneous atmosphere and its time variation. Methods: Betelgeuse was observed between 2.28 and 2.31 μm with VLTI/AMBER using the 16-32-48 m telescope configuration with a spectral resolution up to 12 000 and an angular resolution of 9.8 mas. The good nearly one-dimensional uv coverage allows us to reconstruct one-dimensional projection images (i.e., one-dimensional projections of the object's two-dimensional intensity distributions). Results: The reconstructed one-dimensional projection images reveal that the star appears differently in the blue wing, line center, and red wing of the individual CO lines. The one-dimensional projection images in the blue wing and line center show a pronounced, asymmetrically extended component up to ~1.3 R⋆, while those in the red wing do not show such a component. The observed one-dimensional projection images in the lines can be reasonably explained by a model in which the CO gas within a region more than half as large as the stellar size 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. A comparison between the CO line AMBER data taken in 2008 and 2009 shows a significant time variation in the dynamics of the CO line-forming region in the photosphere and the outer atmosphere. In contrast to the line data, the reconstructed one-dimensional projection images in the continuum show only a slight deviation from a uniform disk or limb-darkened disk. We derive a uniform-disk diameter of 42.05 ± 0.05 mas and a power-law-type limb-darkened disk diameter of 42.49 ± 0.06 mas and a limb-darkening parameter of (9.7 ± 0.5) × 10-2. This latter angular diameter leads to an effective temperature of 3690 ± 54 K

  13. Evolved Massive Stars in the Local Group. I. Identification of Red Supergiants in NGC 6822, M31, and M33

    NASA Astrophysics Data System (ADS)

    Massey, Philip

    1998-07-01

    Knowledge of the red supergiant (RSG) population of nearby galaxies allows us to probe massive star evolution as a function of metallicity; however, contamination by foreground Galactic dwarfs dominates surveys for red stars in Local Group galaxies beyond the Magellanic Clouds. Model atmospheres predict that low-gravity supergiants will have B-V values that are redder by several tenths of a magnitude than foreground dwarfs at a given V-R color, a result that is largely independent of reddening. We conduct a BVR survey of several fields in the Local Group galaxies NGC 6822, M33, and M31 as well as neighboring control fields and identify RSG candidates from CCD photometry. The survey is complete to V = 20.5, corresponding to MV = -4.5 or an Mbol of -6.3 for the reddest stars. Follow-up spectroscopy at the Ca II triplet of 130 stars is used to demonstrate that our photometric criterion for identifying RSGs is highly successful (96% for stars brighter than V = 19.5; 82% for V = 19.5-20.5). Classification spectra are also obtained for a number of stars in order to calibrate color with spectral type empirically. We find that there is a marked progression in the average (B-V)0 and (V-R)0 colors of RSGs in these three galaxies, with the higher metallicity systems having a later average spectral type, which is consistent with previous findings by Elias, Frogel, & Humphreys for the Milky Way and Magellanic Clouds. More significantly, we find that there is a clear progression with metallicity in the relative number of the highest luminosity RSGs, a trend that is apparent both in absolute visual magnitude and in bolometric luminosity. Thus any use of RSGs as distance indicators requires correction for the metallicity of the parent galaxy. Our findings are in accord with the predictions of the ``Conti scenario'' in which higher metallicities result in higher mass-loss rates, resulting in a star of a given luminosity spending an increasing fraction of its He-burning lifetime as

  14. 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

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

    SciTech Connect

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

    2013-11-20

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

  16. 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.

  17. 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

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

    SciTech Connect

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

    2014-07-20

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

  19. Soft X-ray characterisation of the long-term properties of supergiant fast X-ray transients

    NASA Astrophysics Data System (ADS)

    Romano, P.; Ducci, L.; Mangano, V.; Esposito, P.; Bozzo, E.; Vercellone, S.

    2014-08-01

    Context. Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) that are characterised by a hard X-ray (≥ 15 keV) flaring behaviour. These flares reach peak luminosities of 1036-1037 erg s-1 and last a few hours in the hard X-rays. Aims: We investigate the long-term properties of SFXTs by examining the soft (0.3-10 keV) X-ray emission of the three least active SFXTs in the hard X-ray and by comparing them with the remainder of the SFXT sample. Methods: We performed the first high-sensitivity soft X-ray long-term monitoring with Swift/XRT of three relatively unexplored SFXTs, IGR J08408-4503, IGR J16328-4726, and IGR J16465-4507, whose hard X-ray duty cycles are the lowest measured among the SFXT sample. We assessed how long each source spends in each flux state and compared their properties with those of the prototypical SFXTs. Results: The behaviour of IGR J08408-4503 and IGR J16328-4726 resembles that of other SFXTs, and it is characterised by a relatively high inactivity duty cycle (IDC) and pronounced dynamic range (DR) in the X-ray luminosity. We found DR ~ 7400, IDC ~ 67% for IGR J08408-4503, and DR ~ 750, IDC ~ 61% for IGR J16328-4726 (in all cases the IDC is given with respect to the limiting flux sensitivity of XRT, that is 1-3 × 10-12 erg cm-2 s-1). In common with all the most extreme SFXT prototypes (IGR J17544-2619, XTE J1739-302, and IGR J16479-4514), IGR J08408-4503 shows two distinct flare populations. The first one is associated with the brightest outbursts (X-ray luminosity LX ≳ 1035 - 36 erg s-1), while the second comprises dimmer events with typical luminosities of LX ≲ 1035 erg s-1. This double-peaked distribution of the flares as a function of the X-ray luminosity seems to be a ubiquitous feature of the extreme SFXTs. The lower DR of IGR J16328-4726 suggests that this is an intermediate SFXT. IGR J16465-4507 is characterised by a low IDC ~ 5% and a relatively narrow DR ~ 40, reminiscent of classical supergiant

  20. 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

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

    NASA Astrophysics Data System (ADS)

    Barba, Rodolfo; Gamen, Roberto; Morrell, Nidia

    2006-05-01

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

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

    SciTech Connect

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

    2009-12-10

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

  3. Magnetic confinement, Alfven wave reflection, and the origins of X-ray and mass-loss 'dividing lines' for late-type giants and supergiants

    NASA Technical Reports Server (NTRS)

    Rosner, R.; An, C.-H.; Musielak, Z. E.; Moore, R. L.; Suess, S. T.

    1991-01-01

    A simple qualitative model for the origin of the coronal and mass-loss dividing lines separating late-type giants and supergiants with and without hot, X-ray-emitting corona, and with and without significant mass loss is discussed. The basic physical effects considered are the necessity of magnetic confinement for hot coronal material on the surface of such stars and the large reflection efficiency for Alfven waves in cool exponential atmospheres. The model assumes that the magnetic field geometry of these stars changes across the observed 'dividing lines' from being mostly closed on the high effective temperature side to being mostly open on the low effective temperature side.

  4. 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.

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

    SciTech Connect

    Richardson, N. D.; Morrison, N. D.; Kryukova, E. E.; Adelman, S. J. E-mail: nmorris@utnet.utoledo.edu E-mail: adelmans@citadel.edu

    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.

  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

  7. 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 Brγ 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 μm. The data are complemented by X-Shooter data, which provide a higher spectral resolution view. Results: The Brγ 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 Brγ 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 Brγ 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

  8. Observations of late-type variable stars in the water-vapor radio line. The supergiant VX Sagittarii

    NASA Astrophysics Data System (ADS)

    Pashchenko, M. I.; Rudnitskii, G. M.

    1999-05-01

    Observations of the circumstellar maser emission of the M supergiant VX Sgr in the water-vapor line at 1.35 cm are presented. The observations were carried out from 1981-1998 (JD 2 444 655-2 450 966) on the 22-m radio telescope of the Pushchino Radio Astronomy Observatory of the Astro Space Center of the Lebedev Institute of Physics. Throughout the 17 years of the observations, there were two groups of emission features in the H2O-line profile, which originate in the two oppositely directed lobes of a bipolar outflow from the star. A redistribution of the integrated flux F_int between the two groups of features was noted: in 1981-1987, the group with negative velocities (V_LSR < V_*, where V_* is the stellar velocity) dominated; starting from 1993, F_int for the features with V_LSR > V_* slightly exceeded that for features with V_LSR < V_*. This redistribution of F_int in the H2O-line profile may be associated with a change in the dominant direction for the bipolar outflow due to restructuring of the overall dipolar magnetic field of VX Sgr. A model for the VX Sgr H2O maser source with a circumstellar disk and bipolar outflow in two cones with half-opening angle theta ~ 60deg is discussed. The axis of the bipolar outflow also forms an angle i ~ 60deg to the line of sight. The estimated bipolar-outflow expansion velocity V_0 in the H2O-maser region (R = (1.5-5) x 10^15 cm) is ~10 km/s. The variability of the H2O maser is correlated with the visual light curve of VX Sgr. However, the phase delay delta phi of the F_int(H2O) variations relative to the optical variations changed form 0 to ~1 stellar period (P = 732d) over the time covered by the maser observations. If the variability of the H2O-maser source is the result of periodic impacts of shock waves driven by stellar pulsations, the travel time for the shock from the photosphere to the inner boundary of the H2O maser shell may be as long as (10-15)P.

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

    NASA Astrophysics Data System (ADS)

    Minor, Robert; Guinan, Edward F.

    2016-01-01

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

  10. 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

  11. 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 μm 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 sg

  12. Ultraviolet observations of close-binary and pulsating nuclei of planetary nebulae; Winds and shells around low-mass supergiants; The close-binary nucleus of the planetary nebula HFG-1; A search for binary nuclei of planetary nebulae; UV monitoring of irregularly variable planetary nuclei; and The pulsating nucleus of the planetary nebula Lo 4

    NASA Technical Reports Server (NTRS)

    Bond, Howard E.

    1992-01-01

    A brief summary of the research highlights is presented. The topics covered include the following: binary nuclei of planetary nebulae; other variable planetary nuclei; low-mass supergiants; and other IUE-related research.

  13. Hiding in plain sight - red supergiant imposters? Super-AGB stars - bridging the divide between low/intermediate-mass and high-mass stars

    NASA Astrophysics Data System (ADS)

    Doherty, Carolyn Louise; Gil-Pons, Pilar; Lattanzio, John; Siess, Lionel

    2015-08-01

    Super Asymptotic Giant Branch (Super-AGB) stars reside in the mass range ~ 6.5-10 M⊙ and bridge the divide between low/intermediate-mass and massive stars. They are characterised by off-centre carbon ignition prior to a thermally pulsing phase which can consist of many tens to even thousands of thermal pulses. With their high luminosities and very large, cool, red stellar envelopes, these stars appear seemingly identical to their slightly more massive red supergiant counterparts. Due to their similarities, super-AGB stars may therefore act as stellar imposters and contaminate red supergiant surveys. Super-AGB stars undergo relatively extreme nucleosynthetic conditions, with very efficient proton-capture nucleosynthesis occurring at the base of the convective envelope and also heavy element (s-process) production during the thermal pulse to be later mixed to the surface during third dredge-up events. The surface enrichment from these two processes may result in a clear nucleosynthetic signature to differentiate these two classes of star.The final fate of super-AGB stars is also quite uncertain and depends primarily on the competition between the core growth and mass-loss rates. If the stellar envelope is removed prior to the core reaching the Chandrasekhar mass, an O-Ne white dwarf will remain, otherwise the star will undergo an electron-capture supernova leaving behind a neutron star. We describe the factors which influence these different final fate channels, such as the efficiency of convection, the mass-loss rates, the third dredge-up efficiency and the Fe-peak opacity instability which may lead to expulsion of the entire remaining stellar envelope. We determine the relative fraction of super-AGB stars that end life as either an O-Ne white dwarf or as a neutron star, and provide a mass limit for the lowest mass supernova over a broad range of metallicities from the earliest time (Z=0) right through until today (Z~0.04).

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

    SciTech Connect

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

    2013-09-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  16. The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption, and Aftermath of a Peculiar Supergiant High-mass X-Ray Binary

    NASA Astrophysics Data System (ADS)

    Villar, V. A.; Berger, E.; Chornock, R.; Margutti, R.; Laskar, T.; Brown, P. J.; Blanchard, P. K.; Czekala, I.; Lunnan, R.; Reynolds, M. T.

    2016-10-01

    We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d = 1.86 Mpc) spanning from ‑6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10–12 M ⊙ yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M bol ≲ ‑10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca ii emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L X ≈ 6 × 1039 erg s‑1). We additionally attribute He ii 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈1037 erg s‑1 to the presence of a compact companion.

  17. XMM-Newton and NuSTAR joint observation of the periodic Supergiant Fast X-ray Transient IGR J11215-5952

    NASA Astrophysics Data System (ADS)

    Sidoli, L.; Paizis, A.; Sguera, V.

    2016-06-01

    IGRJ11215-5952 is the only Supergiant Fast X-ray Transient showing periodic outbursts (every 165 days, the orbital period of the system). The driving mechanism causing the transient X-ray emission in this sub-class of High Mass X-ray Binaries is still a matter of debate, after 10 years from the discovery of the class. To disentangle between magnetar-like neutron stars from models requiring more usual neutron star magnetic fields (1E12G), we observed the SFXT pulsar IGRJ11215-5952 with XMM-Newton coordinated with NuSTAR on 2016, February 14, during the expected peak of the outburst, for a net exposure time of 20 ks. The source was indeed caught in outburst (1E36 erg/s), with several bright flares repeating quasi-periodically with timescales of a few thousand seconds, spanning a dynamic range of two orders of magnitude. The overlapping observation with both XMM-Newton and NuSTAR enabled the study of the simultaneous broad band spectrum from 0.3 to 78 keV. The work is still in progress, given the extreme variability of the X-ray emission. X-ray pulsations were detected at 187.14 s, consistent with the last XMM-Newton observation, performed in 2007. We will discuss XMM+NuSTAR results in light of the different models proposed to explain the SFXTs behavior.

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

    SciTech Connect

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  20. The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption and Aftermath of an Unusual Supergiant High-mass X-ray Binary

    NASA Astrophysics Data System (ADS)

    Villar, Victoria; Berger, Edo; Chornock, Ryan; Laskar, Tanmoy; Margutti, Raffaella; Brown, Peter J.

    2016-06-01

    We present high- and medium-resolution optical spectroscopy, optical/UV imaging and archival Chandra, Hubble and Spitzer observations of the intermediate luminosity optical transient (ILOT) SN 2010da, discovered in the nearby galaxy NGC 300 (d=1.86 Mpc). SN 2010da had a peak absolute magnitude of M ~ -10.4 mag, dimmer than other recent ILOTs and supernova impostors. We detect hydrogen Balmer, Paschen and Ca II emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Based on SN 2010da's light curve and multi-epoch SEDs, we conclude that the progenitor of SN 2010da is a ~10-12 Msol yellow supergiant possibly transitioning into a blue loop phase. Since the 2010 eruption, the star has brightened by a factor of ~5 and remains highly variable in the optical. SN 2010da is a unique ILOT which seems to stem from a different physical origin than red SN 2008S-like events and luminous blue variable outbursts. Furthermore, we detect SN 2010da in archival Swift observations as an ultraluminous X-ray source. We additionally attribute He II 4686 and coronal Fe emission in addition to a steady X-ray luminosity of ~10^{37} erg/s to the presence of a compact companion.

  1. 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; Nakauchi, Daisuke; Nakamura, Takashi; Suwa, Yudai

    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.

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

    SciTech Connect

    Handy, Timothy; Plewa, Tomasz; Odrzywołek, Andrzej

    2014-03-10

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

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

    SciTech Connect

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

    2010-12-01

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Pollock, A. M. T.

    2007-03-01

    XMM-Newton observations of the O supergiant ζ Orionis (O9.7 Ib) extend knowledge of its high-resolution spectrum beyond the C VI line at 33.7 Å 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. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

  6. V-Band, Near-IR, and TiO Photometry of the Semi-Regular Red Supergiant TV Geminorum: Long-Term Quasi-Periodic Changes in Temperature, Radius, and Luminosity

    NASA Astrophysics Data System (ADS)

    Wasatonic, Richard P.; Guinan, Edward F.; Durbin, Allyn J.

    2015-10-01

    Seventeen years of V-band and intermediate Wing near-IR TiO (λ719-nm to λ1024-nm) time-series photometry of the M1-4 Iab supergiant TV Geminorum are presented. The observations were conducted from 1997 to 2014 with the primary goals of determining both long-term (years) and short-term (months) periodicities and estimating temporal changes in temperature, luminosity, and radius as the star varies in brightness. Our results suggest a dominant short-term V-band period of ~411 days (~1.12 years) that is superimposed on a long-term cycle of ~3137 days (~8.59 years). Over this long-term cycle, the effective temperature varies between ~3500 K to ~3850 K and, at an adopted distance of 1.5 ± 0.2 kpc, the luminosity varies from ~6.2 × 104 Lsolar to ~8.9 × 104 Lsolar and the radius varies from ~620 Rsolar to ~710 Rsolar. Variations in temperature and luminosity are indicative of a semi-regular long-term pulsation with imposed short-term periods similar to the V-band variations. However, the calculated radius variations are apparently not generally inversely correlated with respect to the long-term temperature and luminosity changes as typically found in Cepheids and Mira-type variables. This observation suggests other undetermined mechanisms, such as the formation and subsequent dissipation of supergranules or possible complex pulsations, are taking place in this evolved red supergiant to account for these variations. Like other young, massive luminous red supergiants such as Betelgeuse (α Orionis) and Antares (α Scorpii), TV Gem shows complicated light variations on time scales that range from months to several years. These evolved high massive stars are important to study because they are nearby, bright progenitors of core-collapsed Type II supernovae.

  7. 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.…

  8. Chemical Reactors.

    ERIC Educational Resources Information Center

    Kenney, C. N.

    1980-01-01

    Describes a course, including content, reading list, and presentation on chemical reactors at Cambridge University, England. A brief comparison of chemical engineering education between the United States and England is also given. (JN)

  9. Chemical sensor

    NASA Technical Reports Server (NTRS)

    Rauh, R. David (Inventor)

    1990-01-01

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

  10. 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 μm) 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

  11. 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.

  12. NEAR-INFRARED COUNTERPARTS TO CHANDRA X-RAY SOURCES TOWARD THE GALACTIC CENTER. II. DISCOVERY OF WOLF-RAYET STARS AND O SUPERGIANTS

    SciTech Connect

    Mauerhan, J. C.; Stolovy, S. R.; Muno, M. P.; Morris, M. R.; Cotera, A.

    2010-02-10

    We present new identifications of infrared counterparts to the population of hard X-ray sources near the Galactic center detected by the Chandra X-ray Observatory. We have spectroscopically confirmed 16 new massive stellar counterparts to the X-ray population, including nitrogen-type (WN) and carbon-type (WC) Wolf-Rayet stars, and O supergiants. These discoveries increase the total sample of massive stellar X-ray sources in the Galactic center region to 30 (possibly 31). For the majority of these sources, the X-ray photometry is consistent with thermal emission from plasma having temperatures in the range of kT = 1-8 keV or non-thermal emission having power-law indices in the range of -1 {approx}< GAMMA {approx}< 3, and X-ray luminosities in the range of L{sub X} {approx} 10{sup 32}-10{sup 34} erg s{sup -1} (0.5-8.0 keV). Several sources have exhibited X-ray variability of several factors between observations. These X-ray properties are not a ubiquitous feature of single massive stars but are typical of massive binaries, in which the high-energy emission is generated by the collision of supersonic winds, or by accretion onto a compact companion. However, without direct evidence for companions, the possibility of intrinsic hard X-ray generation from single stars cannot be completely ruled out. The spectral energy distributions of these sources exhibit significant infrared excess, attributable to free-free emission from ionized stellar winds, supplemented by hot dust emission in the case of the WC stars. With the exception of one object located near the outer regions of the Quintuplet cluster, most of the new stars appear isolated or in loose associations. Seven hydrogen-rich WN and O stars are concentrated near the Sagittarius B H II region, while other similar stars and more highly evolved hydrogen-poor WN and WC stars lie scattered within {approx}50 pc, in projection, of Sagitarrius A West. We discuss various mechanisms capable of generating the observed X

  13. [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.

  14. Chemical microsensors

    DOEpatents

    Li, DeQuan; Swanson, Basil I.

    1995-01-01

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

  15. Chemical sensors

    DOEpatents

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

    1991-07-02

    Sensors responsive to small changes in the concentration of chemical species are disclosed. The sensors comprise a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment. They are operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical response. 9 figures.

  16. Chemical Peels

    MedlinePlus

    ... the complications or potential side effects of a chemical peel? Temporary or permanent change in skin color, particularly for women on birth control pills, who subsequently become pregnant or have a history of brownish facial ... after having a chemical peel? All peels require some follow-up care: ...

  17. Chemical preconcentrator

    DOEpatents

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

    2001-01-01

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

  18. Chemical sensors

    DOEpatents

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

    1991-01-01

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

  19. Chemical Emergencies

    MedlinePlus

    ... agents such as sarin and VX. Many hazardous chemicals are used in industry - for example, chlorine, ammonia, and benzene. Some can be made from everyday items such as household cleaners. Although there are no guarantees of safety during a chemical emergency, you can take actions to protect yourself. ...

  20. Chemical threats.

    PubMed

    Fry, Donald E

    2006-06-01

    The use of chemical agents as military weapons has been recognized for many centuries but reached the most feared and publicized level during World War I. Considerable political effort has been exercised in the twentieth century to restrict military strategies with chemicals. However, considerable concern currently exists that chemical weapons may be used as agents in civilian terrorism. The distribution of acetaminophen tablets contaminated with potassium cyanide and the release of sarin in the Tokyo sub-way system show that larger-scale deployment of chemical agents can be a reality. This reality makes it necessary for civilian disaster-planning strategies to incorporate an understanding of chemical agents, their effects, and the necessary treatment.

  1. 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

  2. Chemical peeling.

    PubMed

    Forte, R; Hack, J; Jackson, I T

    1993-01-01

    This article explores the wide range of chemical facial peels, which include phenol, trichloroacetic acid, and alpha-hydroxy acids. The application of these substances will be described in addition to the contraindications to this type of treatment.

  3. 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)

  4. 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.

  5. Chemical sensors

    DOEpatents

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

    1992-01-01

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

  6. Chemical sensors

    SciTech Connect

    Hubbard, C.W.; Gordon, R.L.

    1987-05-01

    The revolution in analytical chemistry promised by recent developments in the field of chemical sensors has potential for significant positive impact on both research and production activities conducted by and for the Department of Energy. Analyses which were, in the past, performed only with a roomful of expensive equipment can now be performed with miniature solid-state electronic devices or small optical probes. Progress in the development of chemical sensors has been rapid, and the field is currently growing at a great rate. In accordance, Pacific Northwest Laboratory initiated a survey of recent literature so that contributors to active programs in research on analytical methods could be made aware of principles and applications of this new technology. This report presents the results of that survey. The sensors discussed here are divided into three types: micro solid-state devices, optical sensors, and piezoelectric crystal devices. The report is divided into three corresponding sections. The first section, ''Micro Solid-State Devices,'' discusses the design, operation, and application of electronic sensors that are produced in much the same way as standard solid-state electronic devices. The second section, ''Optrodes,'' covers the design and operation of chemical sensors that use fiber optics to detect chemically induced changes in optical properties. The final section, ''Piezoelectric Crystal Detectors,'' discusses two types of chemical sensors that depend on the changes in the properties of an oscillating piezoelectric crystal to detect the presence of certain materials. Advantages and disadvantages of each type of sensor are summarized in each section.

  7. Chemical abundances of massive stars in Local Group galaxies

    NASA Astrophysics Data System (ADS)

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

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

  8. Chemical networks

    NASA Astrophysics Data System (ADS)

    Thi, Wing-Fai

    2015-09-01

    This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One on-going research subject is finding new paths to synthesize species either in the gas-phase or on grain surfaces. Specific formation routes for water or carbon monoxide are discussed in more details. 13th Lecture of the Summer School "Protoplanetary Disks: Theory and Modelling Meet Observations"

  9. 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…

  10. 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…

  11. Chemical Indicators.

    ERIC Educational Resources Information Center

    Prombain, Dorothy R.; And Others

    This science sourcebook was written for intermediate grade teachers to provide guidance in teaching a specially developed unit on chemical indicators. Directions and suggestions for guiding student science activities are given. Some of the activities concern soil testing, crystals, and household powders such as sugar and salt. A list of necessary…

  12. Chemical locomotion.

    PubMed

    Paxton, Walter F; Sundararajan, Shakuntala; Mallouk, Thomas E; Sen, Ayusman

    2006-08-18

    Research into the autonomous motion of artificial nano- and microscale objects provides basic principles to explore possible applications, such as self-assembly of superstructures, roving sensors, and drug delivery. Although the systems described have unique propulsion mechanisms, motility in each case is made possible by the conversion of locally available chemical energy into mechanical energy. The use of catalysts onboard can afford nondissipative systems that are capable of directed motion. Key to the design of nano- and micromotors is the asymmetric placement of the catalyst: its placement in an environment containing a suitable substrate translates into non-uniform consumption of the substrate and distribution of reaction products, which results in the motility of the object. These same principles are exploited in nature to effect autonomous motion.

  13. Chemical information science coverage in Chemical Abstracts.

    PubMed

    Wiggins, G

    1987-02-01

    For many years Chemical Abstracts has included in its coverage publications on chemical documentation or chemical information science. Although the bulk of those publications can be found in section 20 of Chemical Abstracts, many relevant articles were found scattered among 39 other sections of CA in 1984-1985. In addition to the scattering of references in CA, the comprehensiveness of Chemical Abstracts as a secondary source for chemical information science is called into question. Data are provided on the journals that contributed the most references on chemical information science and on the languages of publication of relevant articles.

  14. 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)

  15. The Chemical Engineer in the Chemical Industry.

    ERIC Educational Resources Information Center

    Zabicky, Jacob

    1986-01-01

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

  16. Microfluidic chemical reaction circuits

    DOEpatents

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

    2012-06-26

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

  17. Chemical Management System

    1998-10-30

    CMS provides an inventory of all chemicals on order or being held in the laboratory, to provide a specific location for all chemical containers, to ensure that health and safety regulatory codes are being upheld, and to provide PNNL staff with hazardous chemical information to better manage their inventories. CMS is comprised of five major modules: 1) chemical purchasing, 2) chemical inventory, 3) chemical names, properties, and hazard groups, 4) reporting, and 5) system administration.

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

    SciTech Connect

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

    1990-10-01

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

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

    PubMed Central

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

    1990-01-01

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

  20. Chemical Industry Corrosion Management

    SciTech Connect

    2003-02-01

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

  1. The chemical life(1).

    PubMed

    Hodges, Nathan

    2015-01-01

    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

  2. The chemical life(1).

    PubMed

    Hodges, Nathan

    2015-01-01

    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.

  3. 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.

  4. 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.

  5. Supergiant pulses from extragalactic neutron stars

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.; Wasserman, Ira

    2016-03-01

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

  6. Red Supergiants in the Local Group

    NASA Astrophysics Data System (ADS)

    Levesque, E. M.

    2013-05-01

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

  7. Personal Chemical Exposure informatics

    EPA Science Inventory

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

  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. Chemicals Industry Vision

    SciTech Connect

    none,

    1996-12-01

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

  10. 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 ...

  11. 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.

  12. Chemical Transformation Simulator

    EPA Science Inventory

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

  13. Chemical Industry Bandwidth Study

    SciTech Connect

    none,

    2006-12-01

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

  14. 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.

  15. 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.

  16. 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)

  17. Chemical Synthesis of Proteins

    PubMed Central

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

    2010-01-01

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

  18. Evolved stars as complex chemical laboratories - the quest for gaseous chemistry

    NASA Astrophysics Data System (ADS)

    Katrien Els Decin, Leen

    2015-08-01

    At the end of their life, most stars lose a large fraction of their mass through a stellar wind. The stellar winds of evolved (super)giant stars are the dominant suppliers for the pristine building blocks of the interstellar medium (ISM). Crucial to the understanding of the chemical life cycle of the ISM is hence a profound insight in the chemical and physical structure governing these stellar winds.These winds are really unique chemical laboratories in which currently more than 70 different molecules and 15 different dust species are detected. Several chemical processes such as neutral-neutral and ion-molecule gas-phase reactions, dust nucleation and growth, and photo-processes determine the chemical content of these winds. However, gas-phase and dust-nucleation chemistry for astronomical environments still faces many challenges. One should realize that only ˜15% of the rate coefficients for gas-phase reactions considered to occur in (inter/circum)stellar regions at temperatures (T) below 300K have been subject to direct laboratory determinations and that the temperature dependence of the rate constants is often not known; only ˜2% have rate constants at T<200K and less than 0.5% at T<100 K. For stellar wind models, an important bottleneck occurs among the reactions involving silicon- and sulfur-bearing species, for which only a few have documented reaction rates. Often, researchers are implementing ‘educated guesses’ for these unknown rates, sometimes forcing the network to yield predictions concurring with (astronomical) observations. Large uncertainties are inherent in this type of ‘optimized’ chemical schemes.Thanks to an ERC-CoG grant, we are now in the position to solve some riddles involved in understanding the gas-phase chemistry in evolved stars. In this presentation, I will demonstrate the need for accurate temperature-dependent gas-phase reaction rate constants and will present our new laboratory equipment built to measure the rate constants

  19. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  1. Toxic Chemical System (TCS)

    SciTech Connect

    Del Gandio, P.

    1994-09-01

    The Toxic Chemical System (TCS) will have the capacity to process chemical data, calculate chemical formulas, and format the data into the United States (US) Environmental Protection Agency (EPA) Toxic Chemical Release Inventory Reporting Form R of Section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA), hereafter be referred to as ``Form R.`` The filing of this form is required of all industries which manufacture, process or otherwise use any EPA listed chemicals in quantities in excess of their threshold planning quantities (TPQ). Facilities required to file the Form R must report the quantities of both routine and accidental releases of listed toxic chemicals on-site during the calendar year and the amount contained in waste products transferred off-site. This paper describes a specialized computer system designed for regulatory compliance.

  2. 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.

  3. 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.

  4. Chemical penetration enhancers.

    PubMed

    Newton, Stephen J

    2013-01-01

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

  5. 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.

  6. 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.

  7. Apparatus for chemical synthesis

    DOEpatents

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

    2011-05-10

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

  8. 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.

  9. 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.

  10. Students Enjoy Chemical Sensation

    ERIC Educational Resources Information Center

    Barry, Dana M.; Kanematsu, Hideyuki

    2003-01-01

    This exciting new way of teaching high school/college chemistry combines music, visual aids, and chemical experiments in multi-sensory lessons that motivate students and provide them with meaningful learning experiences in science. The method, known as the Chemical Sensation Project, acknowledges that some individuals learn by seeing or hearing,…

  11. Chemical Process Synthesis.

    ERIC Educational Resources Information Center

    Siirola, J. J.

    1982-01-01

    Process synthesis is the specification of chemical and physical operations and the selection and interconnection of equipment to implement these operations to effect desired chemical processing transformations. Optimization and evolutionary and systematic generation process synthesis approaches are described. (Author/SK)

  12. Fundamentals of Chemical Processes.

    ERIC Educational Resources Information Center

    Moser, William R.

    1985-01-01

    Describes a course that provides students with a fundamental understanding of the chemical, catalytic, and engineering sciences related to the chemical reactions taking place in a variety of reactors of different configurations. Also describes the eight major lecture topics, course examinations, and term papers. The course schedule is included.…

  13. Chemical Reaction Problem Solving.

    ERIC Educational Resources Information Center

    Veal, William

    1999-01-01

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

  14. Chemical Equation Balancing.

    ERIC Educational Resources Information Center

    Blakley, G. R.

    1982-01-01

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

  15. 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.

  16. 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)

  17. Chemicals in Everyday Life.

    ERIC Educational Resources Information Center

    Seymour, Raymond B.

    1987-01-01

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

  18. 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)

  19. 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)

  20. Microorganisms and Chemical Pollution

    ERIC Educational Resources Information Center

    Alexander, M.

    1973-01-01

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

  1. Chemical 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...

  2. Chemical burn or reaction

    MedlinePlus

    Burn from chemicals ... in contact with the toxic substance Rash , blisters , burns on the skin Unconsciousness or other states of ... Make sure the cause of the burn has been removed. Try not to come ... yourself. If the chemical is dry, brush off any excess. Avoid ...

  3. Tortuous path chemical preconcentrator

    DOEpatents

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

    2010-09-21

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

  4. Chemical recognition software

    SciTech Connect

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

    1994-06-01

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

  5. Chemical recognition software

    SciTech Connect

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

    1994-12-01

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

  6. Young Stars and Ionized Nebulae in M83: Comparing Chemical Abundances at High Metallicity.

    NASA Astrophysics Data System (ADS)

    Bresolin, Fabio; Kudritzki, Rolf-Peter; Urbaneja, Miguel A.; Gieren, Wolfgang; Ho, I.-Ting; Pietrzyński, Grzegorz

    2016-10-01

    We present spectra of 14 A-type supergiants in the metal-rich spiral galaxy M83. We derive stellar parameters and metallicities and measure a spectroscopic distance modulus μ =28.47+/- 0.10 (4.9 ± 0.2 Mpc), in agreement with other methods. We use the stellar characteristic metallicity of M83 and other systems to discuss a version of the galaxy mass–metallicity relation that is independent of the analysis of nebular emission lines and the associated systematic uncertainties. We reproduce the radial metallicity gradient of M83, which flattens at large radii, with a chemical evolution model, constraining gas inflow and outflow processes. We carry out a comparative analysis of the metallicities we derive from the stellar spectra and published H ii region line fluxes, utilizing both the direct, {T}{{e}}-based method and different strong-line abundance diagnostics. The direct abundances are in relatively good agreement with the stellar metallicities, once we apply a modest correction to the nebular oxygen abundance due to depletion onto dust. Popular empirically calibrated strong-line diagnostics tend to provide nebular abundances that underestimate the stellar metallicities above the solar value by ∼0.2 dex. This result could be related to difficulties in selecting calibration samples at high metallicity. The O3N2 method calibrated by Pettini and Pagel gives the best agreement with our stellar metallicities. We confirm that metal recombination lines yield nebular abundances that agree with the stellar abundances for high-metallicity systems, but find evidence that in more metal-poor environments they tend to underestimate the stellar metallicities by a significant amount, opposite to the behavior of the direct method.

  7. Chemical process hazards analysis

    SciTech Connect

    1996-02-01

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

  8. Chemical ecology of fungi.

    PubMed

    Spiteller, Peter

    2015-07-01

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

  9. Chemical Hygiene Program

    NASA Technical Reports Server (NTRS)

    Mayor, Antoinette C.

    1999-01-01

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

  10. Chemical ecology of fungi.

    PubMed

    Spiteller, Peter

    2015-07-01

    Fungi are widespread in nature and have conquered nearly every ecological niche. Fungi occur not only in terrestrial but also in freshwater and marine environments. Moreover, fungi are known as a rich source of secondary metabolites. Despite these facts, the ecological role of many of these metabolites is still unknown and the chemical ecology of fungi has not been investigated systematically so far. This review intends to present examples of the various chemical interactions of fungi with other fungi, plants, bacteria and animals and to give an overview of the current knowledge of fungal chemical ecology. PMID:26038303

  11. 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

  12. 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

  13. 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)

  14. 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.

  15. A bionics chemical synapse.

    PubMed

    Thanapitak, Surachoke; Toumazou, Christofer

    2013-06-01

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

  16. Reflections on Chemical Equations.

    ERIC Educational Resources Information Center

    Gorman, Mel

    1981-01-01

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

  17. 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)

  18. Chemical Physics Summer School

    SciTech Connect

    2002-06-28

    The Gordon Research Conference (GRC) on Chemical Physics Summer School was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  19. Chemical Bonds II

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

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

  20. Chemical dependence - resources

    MedlinePlus

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

  1. Quantum Chemical Calculations

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  2. Chemical contamination remote sensing

    NASA Technical Reports Server (NTRS)

    Carrico, J. P.; Phelps, K. R.; Webb, E. N.; Mackay, R. A.; Murray, E. R.

    1986-01-01

    A ground mobile laser test bed system was assembled to assess the feasibility of detection of various types of chemical contamination using Differential Scattering (DISC) and Differential Absorption (DIAL) Lidar techniques. Field experiments with the test bed system using chemical simulants were performed. Topographic reflection and range resolved DIAL detection of vapors as well as DISC detection of aerosols and surface contamination were achieved. Review of detection principles, design of the test bed system, and results of the experiments are discussed.

  3. Chemical shifts in biomolecules

    PubMed Central

    Case, David A.

    2013-01-01

    Summary NMR chemical shifts are sensitive probes of stucture and dynamics in proteins. Empirical models, based on a large database of measured shifts, take an input structure and provide increasingly accurate estimates of the corresponding shifts. Quantum chemical calculations can provide the same information, with greater generality but (currently) with less accuracy. These methods are now providing new ways to approach NMR structure determination, and new insights into the conformational dynamics of proteins. PMID:23422068

  4. Clean boiler systems chemically

    SciTech Connect

    Robinson, J.O. )

    1993-04-01

    Internal surfaces of steam generator systems are cleaned to remove contaminants that impair heat transfer and may ultimately cause tube failure. One method of doing so is chemical cleaning. All new steam generators should be chemically cleaned to remove construction contaminants. The degree of cleaning required depends on the initial condition of the boiler and on its operating requirements. This paper discusses: key considerations; pre-operational cleaning; post-operational cleaning; water flushing and steam blowing; alkaline cleaning; and solvent cleaning.

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

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1972

    1972-01-01

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

  6. Computational systems chemical biology.

    PubMed

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

    2011-01-01

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

  7. Chemical warfare agents.

    PubMed

    Chauhan, S; Chauhan, S; D'Cruz, R; Faruqi, S; Singh, K K; Varma, S; Singh, M; Karthik, V

    2008-09-01

    Chemical warfare agents (CWA's) are defined as any chemical substance whose toxic properties are utilised to kill, injure or incapacitate an enemy in warfare and associated military operations. Chemical agents have been used in war since times immemorial, but their use reached a peak during World War I. During World War II only the Germans used them in the infamous gas chambers. Since then these have been intermittently used both in war and acts of terrorisms. Many countries have stockpiles of these agents. There has been a legislative effort worldwide to ban the use of CWA's under the chemical weapons convention which came into force in 1997. However the manufacture of these agents cannot be completely prohibited as some of them have potential industrial uses. Moreover despite the remedial measures taken so far and worldwide condemnation, the ease of manufacturing these agents and effectiveness during combat or small scale terrorist operations still make them a powerful weapon to reckon with. These agents are classified according to mechanism of toxicity in humans into blister agents, nerve agents, asphyxiants, choking agents and incapacitating/behavior altering agents. Some of these agents can be as devastating as a nuclear bomb. In addition to immediate injuries caused by chemical agents, some of them are associated with long term morbidities and psychological problems. In this review we will discuss briefly about the historical background, properties, manufacture techniques and industrial uses, mechanism of toxicity, clinical features of exposure and pharmacological management of casualties caused by chemical agents. PMID:21783898

  8. The Chemical Revolution revisited.

    PubMed

    Chang, Hasok

    2015-02-01

    I respond to the critical comments by Martin Kusch and Ursula Klein on my account of the Chemical Revolution. I comment along three different lines: descriptive, explanatory, and normative. (1) I agree with Klein that Lavoisier did not introduce drastic changes in chemical ontology, but maintain that there was methodological incommensurability in the Chemical Revolution; in response to Kusch's view, I maintain that Lavoisier's victory was slow and incomplete. (2) Admitting that there were many causes shaping the outcome of the Chemical Revolution, including the convenience of Lavoisier's theoretical scheme and various complicated social factors, I still think that the general rise of compositionism was an important factor. (3) I defend my normative pluralist view on the Chemical Revolution, denying Kusch's argument that chemists had overwhelmingly good reasons to trust Lavoisier and his allies over the phlogistonists. Overall, I agree with Kusch that it would be desirable to have a good descriptive-normative sociological account of the Chemical Revolution, but I also think that it should be an account that allows for divergence in individuals' and sub-communities' self-determination.

  9. Chemical information systems

    SciTech Connect

    Zebora, M.

    1994-12-31

    The growing number of Federal and State regulations today from EPA to OSHA is putting a large burden on organizations to comply with regard to chemicals in the work place. The cornerstone of chemical information is the Material Safety Data Sheet (MSDS). The MSDS has been a requirement for chemical manufacturers for over fifteen years. Manufacturers of hazardous materials must provide MSDSs to purchasers. However, recent additional regulations from OSHA, in particular the Right To Know and the Hazard Communication Standard (Haz-Com) require that employers who use chemicals must be capable of providing an MSDS to every employee that requests one for a material that they work with. Paper filing systems to managing MSDSs are hard to maintain, costly, and inefficient. In multifacility organizations this can result in delays in distributions of those MSDSs to employees. At AT and T Bell Laboratories the Environmental Health and Safety Center has invested over a decade of development work into producing an integrated Chemical Inventory System/MSDS System. That system meets the requirements discussed in this paper and serves six major R and D laboratory facilities in three states. The system resides on a desktop personal computer. Operation of the system relies on teamwork between several diverse organizations which are involved in management of chemical safety at AT and T Bell Laboratories. The departments represented on that team are Industrial Hygiene and Safety, Environmental Management, Facilities Operations, Purchasing, Health Services, Research, and Environmental Data Management Services.

  10. The Chemical Revolution revisited.

    PubMed

    Chang, Hasok

    2015-02-01

    I respond to the critical comments by Martin Kusch and Ursula Klein on my account of the Chemical Revolution. I comment along three different lines: descriptive, explanatory, and normative. (1) I agree with Klein that Lavoisier did not introduce drastic changes in chemical ontology, but maintain that there was methodological incommensurability in the Chemical Revolution; in response to Kusch's view, I maintain that Lavoisier's victory was slow and incomplete. (2) Admitting that there were many causes shaping the outcome of the Chemical Revolution, including the convenience of Lavoisier's theoretical scheme and various complicated social factors, I still think that the general rise of compositionism was an important factor. (3) I defend my normative pluralist view on the Chemical Revolution, denying Kusch's argument that chemists had overwhelmingly good reasons to trust Lavoisier and his allies over the phlogistonists. Overall, I agree with Kusch that it would be desirable to have a good descriptive-normative sociological account of the Chemical Revolution, but I also think that it should be an account that allows for divergence in individuals' and sub-communities' self-determination. PMID:26109414

  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 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.

  13. 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.

  14. Micromachined chemical jet dispenser

    DOEpatents

    Swierkowski, Steve P.

    1999-03-02

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

  15. 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.

  16. Advanced Chemical Propulsion Study

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  17. Translated chemical reaction networks.

    PubMed

    Johnston, Matthew D

    2014-05-01

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

  18. Electropulse chemical machining

    SciTech Connect

    Allen, T.A.; Rospopo, S.D.

    1984-08-01

    Electropulse Chemical Machining is a new technique in chemical milling, and we have applied it to the photoforming of molybdenum. We apply direct current in short pulses at current densities of thousands of amperes per square foot with little thermal degradation of resists or workpieces. We have achieved etch rates an order of magnitude faster than those of existing methods, with a corresponding improvement in surface finish. Equipment designed for pulse plating can be used and is readily available from plating suppliers. Chemicals are commercially available and may be diluted to levels that protect resist images, reduce hazards to personnel, and simplify disposal. We speculate that this process can be applied to other refractory metals and noble metals.

  19. Chemical Domino Demonstration

    NASA Astrophysics Data System (ADS)

    Alexander, M. Dale

    1998-04-01

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

  20. Chemical Screening in Zebrafish.

    PubMed

    Brady, Colleen A; Rennekamp, Andrew J; Peterson, Randall T

    2016-01-01

    Phenotypic small molecule screens in zebrafish have gained popularity as an unbiased approach to probe biological processes. In this chapter we outline basic methods for performing chemical screens with larval zebrafish including breeding large numbers of embryos, plating larval fish into multi-well dishes, and adding small molecules to these wells. We also highlight important considerations when designing and interpreting the results of a phenotypic screen and possible follow-up approaches, including popular methods used to identify the mechanism of action of a chemical compound. PMID:27464797

  1. Pazufloxacin Toyama Chemical Co.

    PubMed

    Johnson, A P

    2000-09-01

    Toyama Chemical Co Ltd is developing pazufloxacin (T-3761), an orally active synthetic quinolone antibiotic, which is awaiting registration following successful clinical trials that demonstrated its pharmacological similarities to tosufloxacin (Toyama Chemical Co) with respect to clinical efficacy, adverse effects and overall safety [272136]. As of June 2000, the company had filed an NDA for marketing approval in Japan [373027]. The company is also developing an injectable formulation, pazufloxacin mesylate (T-3762), which has entered phase III trials in Japan [228819]. There is a licensing agreement with Welfide Corp (formerly Yoshitomi/The Green Cross Corp) in Japan [228819]. PMID:11249595

  2. Multiple-chemical sensitivity.

    PubMed

    Glinton, Gloria J

    2005-12-01

    Multiple-chemical sensitivity (MCS) is a condition in which individuals have an acute hypersensitivity to low levels of chemicals found in everyday substances, such as household cleaning agents, pesticides, fresh paint, new carpeting, synthetic building materials, newsprint, perfume, and numerous other petrochemical products. This condition continues to remain somewhat of a mystery to the medical community, and its true prevalence rate is unknown because many cases are not identified and reported as MCS. This article will inform the reader about the condition of MCS.

  3. Chemical space and biology.

    PubMed

    Dobson, Christopher M

    2004-12-16

    Chemical space--which encompasses all possible small organic molecules, including those present in biological systems--is vast. So vast, in fact, that so far only a tiny fraction of it has been explored. Nevertheless, these explorations have greatly enhanced our understanding of biology, and have led to the development of many of today's drugs. The discovery of new bioactive molecules, facilitated by a deeper understanding of the nature of the regions of chemical space that are relevant to biology, will advance our knowledge of biological processes and lead to new strategies to treat disease.

  4. Chemical oceanography dissertations presented

    NASA Astrophysics Data System (ADS)

    Anderson, Neil R.; Graham, William; Green, Edward

    The seventh session of Dissertations in Chemical Oceanography (DISCO VII) was convened February 8-13, 1987, at the East-West Center at the Manoa Campus of the University of Hawaii under joint support from the National Science Foundation, Office of Naval Research, and National Oceanographic and Atmospheric Administration Sea Grant Program. These symposia are dedicated to individuals who have recently received Ph.D.s in chemical oceanography or who will do so in the near future. The participants present their thesis research to their peers, and at the end of the meeting the three sponsoring agencies describe their respective programs and respond to questions.

  5. Equilibria in Chemical Systems

    1992-01-01

    SOLGASMIX-PV calculates equilibrium relationships in complex chemical systems. Chemical equilibrium calculations involve finding the system composition, within certain constraints, which contains the minimum free energy. The constraints are the preservation of the masses of each element present and either constant pressure or volume. SOLGASMIX-PV can calculate equilibria in systems containing a gaseous phase, condensed phase solutions, and condensed phases of invariant and variable stoichiometry. Either a constant total gas volume or a constant total pressuremore » can be assumed. Unit activities for condensed phases and ideality for solutions are assumed, although nonideal systems can be handled provided activity coefficient relationships are available.« less

  6. 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.

  7. Epigenetics and environmental chemicals

    PubMed Central

    Baccarelli, A; Bollati, V.

    2011-01-01

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

  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. Electro-chemical grinding

    NASA Technical Reports Server (NTRS)

    Feagans, P. L.

    1972-01-01

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

  10. Chemical conditioning of sludge.

    PubMed

    Novak, J T; Park, C

    2004-01-01

    With all the advances made in understanding the structure and composition of sewage sludges, chemical conditioning remains a trial and error process, both with regard to the type and dose of conditioner needed. Recent studies at Virginia Tech have found that biological floc consists of two types of biopolymer, material associated with iron and aluminium and material associated with calcium and magnesium. These materials behave differently when sludges undergo digestion. This results in very different material being released into solution during digestion and very different conditioning requirements. This study shows that the primary materials released during anaerobic digestion are proteins and coagulation of the colloidal protein fraction in solution is the primary mechanism for conditioning. For aerobically digested sludges, both proteins and polysaccharides make up the colloid fraction, which interferes with dewatering. This research also shows that the effectiveness of the digestion process as characterized by volatile solids destruction is directly related to the chemical dose required for conditioning. That is, as the solids destruction increases, the conditioning chemical requirement also increases. Well digested sludges dewater more poorly and require more conditioning chemical than those with less volatile solids destruction. PMID:15259940

  11. 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.

  12. 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…

  13. Making a Chemical Rainbow

    ERIC Educational Resources Information Center

    Angelin, Marcus; Ramstrom, Olof

    2010-01-01

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

  14. NETL - Chemical Looping Reactor

    ScienceCinema

    None

    2016-07-12

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

  15. 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

  16. Oscillating Chemical Reactions

    ERIC Educational Resources Information Center

    Hawkins, M. D.; And Others

    1975-01-01

    Describes several oscillating chemical reactions which can be used in undergraduate chemistry laboratories. In one such reaction, ferroin oscillates from red (reducing solution) to blue (oxidizing solution) for about an hour at a frequency which can readily be shown to depend on such factors as the temperature, type of solvent, and concentration…

  17. Chemical reacting flows

    NASA Technical Reports Server (NTRS)

    Mularz, Edward J.; Sockol, Peter M.

    1990-01-01

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

  18. 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.

  19. 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)

  20. Chemical plume source localization.

    PubMed

    Pang, Shuo; Farrell, Jay A

    2006-10-01

    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 vehicle is capable of detecting above-threshold chemical concentration and sensing the fluid flow velocity at the vehicle location. This paper reviews instances of biological plume tracing and reviews previous strategies for a vehicle-based plume tracing. The main contribution is a new source-likelihood mapping approach based on Bayesian inference methods. Using this Bayesian methodology, the source-likelihood map is propagated through time and updated in response to both detection and nondetection events. Examples are included that use data from in-water testing to compare the mapping approach derived herein with the map derived using a previously existing technique. PMID:17036813

  1. NETL - Chemical Looping Reactor

    SciTech Connect

    2013-07-24

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

  2. Chemical Calcium Indicators

    PubMed Central

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

    2008-01-01

    Our understanding of the underlying mechanisms of Ca2+ signaling as well as our appreciation for its ubiquitous role in cellular processes and has been rapidly advanced, in large part, due to the development of fluorescent Ca2+ indicators. In this chapter, we discuss some of the most common chemical Ca2+ indicators that are widely used for the investigation of intracellular Ca2+ signaling. Advantages, limitations and relevant procedures will be presented for each dye including their spectral qualities, dissociation constants, chemical forms, loading methods and equipment for optimal imaging. Chemical indicators that are now available allow for intracellular Ca2+ detection over a very large range (<50 nM to >50 μM). Higher affinity indicators can be used to quantify Ca2+ levels in the cytosol while lower affinity indicators can be optimized for measuring Ca2+ in subcellular compartments with higher concentrations. Indicators can be classified into either single wavelength or ratiometric dyes. Both classes require specific lasers, filters, and/or detection methods that are dependent upon their spectral properties and both classes have advantages and limitations. Single wavelength indicators are generally very bright and optimal for Ca2+ detection when more than one fluorophore is being imaging. Ratiometric indicators can be calibrated very precisely and they minimize the most common problems associated with chemical Ca2+ indicators including uneven dye loading, leakage, photobleaching and changes in cell volume. Recent technical advances that permit in vivo Ca2+ measurements will also be discussed. PMID:18929663

  3. Chemical Aspects of Dentistry.

    ERIC Educational Resources Information Center

    Helfman, Murry

    1982-01-01

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

  4. 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…

  5. 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 ...

  6. Common Chemicals around the House.

    ERIC Educational Resources Information Center

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

    1991-01-01

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

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. Ionization structure and chemical abundances of the Wolf-Rayet nebula NGC 6888 with integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Fernández-Martín, A.; Martín-Gordón, D.; Vílchez, J. M.; Pérez Montero, E.; Riera, A.; Sánchez, S. F.

    2012-05-01

    Context. The study of nebulae around Wolf-Rayet (WR) stars gives us clues about the mass-loss history of massive stars, as well as about the chemical enrichment of the interstellar medium (ISM). Aims: This work aims to search for the observational footprints of the interactions between the ISM and stellar winds in the WR nebula NGC 6888 in order to understand its ionization structure, chemical composition, and kinematics. Methods: We have collected a set of integral field spectroscopy observations across NGC 6888, obtained with PPAK in the optical range performing both 2D and 1D analyses. Attending to the 2D analysis in the northeast part of NGC 6888, we have generated maps of the extinction structure and electron density. We produced statistical frequency distributions of the radial velocity and diagnostic diagrams. Furthermore, we performed a thorough study of integrated spectra in nine regions over the whole nebula. Results: The 2D study has revealed two main behaviours. We have found that the spectra of a localized region to the southwest of this pointing can be represented well by shock models assuming n = 1000 cm-3, twice solar abundances, and shock velocities from 250 to 400 km s-1. With the 1D analysis we derived electron densities ranging from <100 to 360 cm-3. The electron temperature varies from ~7700 K to ~10 200 K. A strong variation of up to a factor 10 between different regions in the nitrogen abundance has been found: N/H appears lower than the solar abundance in those positions observed at the edges and very enhanced in the observed inner parts. Oxygen appears slightly underabundant with respect to solar value, whereas the helium abundance is found to be above it. We propose a scenario for the evolution of NGC 6888 to explain the features observed. This scheme consists of a structure of multiple shells: i) an inner and broken shell with material from the interaction between the supergiant and WR shells, presenting an overabundance in N/H and a

  12. Chemical genetics and regeneration.

    PubMed

    Sengupta, Sumitra; Zhang, Liyun; Mumm, Jeff S

    2015-01-01

    Regeneration involves interactions between multiple signaling pathways acting in a spatially and temporally complex manner. As signaling pathways are highly conserved, understanding how regeneration is controlled in animal models exhibiting robust regenerative capacities should aid efforts to stimulate repair in humans. One way to discover molecular regulators of regeneration is to alter gene/protein function and quantify effect(s) on the regenerative process: dedifferentiation/reprograming, stem/progenitor proliferation, migration/remodeling, progenitor cell differentiation and resolution. A powerful approach for applying this strategy to regenerative biology is chemical genetics, the use of small-molecule modulators of specific targets or signaling pathways. Here, we review advances that have been made using chemical genetics for hypothesis-focused and discovery-driven studies aimed at furthering understanding of how regeneration is controlled.

  13. Organic chemical evolution

    NASA Technical Reports Server (NTRS)

    Chang, S.

    1981-01-01

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

  14. Chemicals in the Environment

    PubMed Central

    Rudd, Robert L.

    1970-01-01

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

  15. 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

  16. Biocatalysis for biobased chemicals.

    PubMed

    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

  17. Chemical Synthesis of Glycosaminoglycans.

    PubMed

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

    2016-07-27

    Glycosaminoglycans (GAGs) as one major part of the glycocalyx are involved in many essential biological cell processes, as well as in many courses of diseases. Because of the potential therapeutic application of GAG polymers, fragments, and also derivatives toward different diseases (e.g., heparin derivatives against Alzheimer's disease), there is a continual growing demand for new chemical syntheses, which suffice the high claim to stereoselectivity and chemoselectivity. This Review summarizes the progress of chemical syntheses of GAGs over the last 10 years. For each class of the glycosaminoglycans-hyaluronan (HA), heparan sulfate/heparin (HS/HP), chondroitin/dermatan sulfate (CS/DS), and keratan sulfate (KS)-mainly novel glycosylation strategies, elongation sequences, and protecting group patterns are discussed, but also (semi)automated syntheses, enzymatic approaches, and functionalizations of synthesized or isolated GAGs are considered. PMID:27410264

  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 Kiloton Experiment schedules

    NASA Astrophysics Data System (ADS)

    The Lawrence Livermore National Laboratory will conduct a large chemical explosion (CE) called the Chemical Kiloton Experiment (CKE) in the Rainier Mesa area of the Nevada Test site. The explosion will involve a 30/70 Emulsion-to-ANFO blend of 1,147,000 kg to supply 1 kt, and is scheduled for January 29. It will be heavily instrumented with close-in, free-field surface seismic and regional seismic measurements. The CKE is located near several DNA-sponsored nuclear explosions (NEs) and will provide a unique opportunity for fundamental studies on explosion phenomenology (for example, CE/NE equivalence), scaling with CEs and NEs, and integration of multiple monitoring methods. This experiment will also address some critical proliferation monitoring problems such as CE masking of NEs, CEs as false alarms, CEs for regional calibration, and on-site inspection.

  20. Galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Chiappini, C.; Matteucci, F.

    2001-11-01

    In this paper we review the current ideas about the formation of our Galaxy. In particular, the main ingredients necessary to build chemical evolution models (star formation, initial mass function and stellar yields) are described and discussed. A critical discussion about the main observational constraints available is also presented. Finally, our model predictions concerning the evolution of the abundances of several chemical elements (H, D, He, C, N, O, Ne, Mg, Si, Ca and Fe) are compared with observations relative to the solar neighborhood and the whole disk. We show that from this comparison we can constrain the history of the formation and evolution of the Milky Way as well as the nucleosynthesis theories concerning the Big Bang and the stars. .

  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 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

  3. Biocatalysis for biobased chemicals.

    PubMed

    de Regil, Rubén; Sandoval, Georgina

    2013-10-17

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

  4. Cyanobacterial chemical production.

    PubMed

    Case, Anna E; Atsumi, Shota

    2016-08-10

    The increase in global temperatures caused by rising CO2 levels necessitates the development of alternative sources of fuel and chemicals. One appealing alternative that has been receiving increased attention in recent years is the photosynthetic conversion of atmospheric CO2 to biofuels and chemical products using genetically engineered cyanobacteria. This can help to not only provide an alternate "greener" source for some of the most popular petroleum based products but it can also help to reduce atmospheric CO2. Utilizing cyanobacteria rather than plants allows for reduced land requirements and reduces competition with food crops. This review discusses advancements in the field since 2012 with a particular emphasis on production of hydrocarbons. PMID:27238233

  5. Chemical vapor deposition sciences

    SciTech Connect

    1992-12-31

    Chemical vapor deposition (CVD) is a widely used method for depositing thin films of a variety of materials. Applications of CVD range from the fabrication of microelectronic devices to the deposition of protective coatings. New CVD processes are increasingly complex, with stringent requirements that make it more difficult to commercialize them in a timely fashion. However, a clear understanding of the fundamental science underlying a CVD process, as expressed through computer models, can substantially shorten the time required for reactor and process development. Research scientists at Sandia use a wide range of experimental and theoretical techniques for investigating the science of CVD. Experimental tools include optical probes for gas-phase and surface processes, a range of surface analytic techniques, molecular beam methods for gas/surface kinetics, flow visualization techniques and state-of-the-art crystal growth reactors. The theoretical strategy uses a structured approach to describe the coupled gas-phase and gas-surface chemistry, fluid dynamics, heat and mass transfer of a CVD process. The software used to describe chemical reaction mechanisms is easily adapted to codes that model a variety of reactor geometries. Carefully chosen experiments provide critical information on the chemical species, gas temperatures and flows that are necessary for model development and validation. This brochure provides basic information on Sandia`s capabilities in the physical and chemical sciences of CVD and related materials processing technologies. It contains a brief description of the major scientific and technical capabilities of the CVD staff and facilities, and a brief discussion of the approach that the staff uses to advance the scientific understanding of CVD processes.

  6. Micromachined chemical jet dispenser

    SciTech Connect

    Swierkowski, S.; Ciarlo, D.

    1996-05-13

    Goal is to develop a multi-channel micromachined chemical fluid jet dispenser that is applicable to prototype tests with biological samples that demonstrate its utility for molecular biology experiments. Objective is to demonstrate a new device capable of ultrasonically ejecting droplets from 10-200 {mu}m diameter capillaries that are arranged in an array that is linear or focused. The device is based on several common fabrication procedures used in MEMS (micro electro mechanical systems) technology: piezoelectric actuators, silicon, etc.

  7. Chemical propulsion technology

    NASA Technical Reports Server (NTRS)

    Priem, R. J.

    1980-01-01

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

  8. 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.

  9. 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.

  10. The Use of Chemical-Chemical Interaction and Chemical Structure to Identify New Candidate Chemicals Related to Lung Cancer.

    PubMed

    Chen, Lei; Yang, Jing; Zheng, Mingyue; Kong, Xiangyin; Huang, Tao; Cai, Yu-Dong

    2015-01-01

    Lung cancer causes over one million deaths every year worldwide. However, prevention and treatment methods for this serious disease are limited. The identification of new chemicals related to lung cancer may aid in disease prevention and the design of more effective treatments. This study employed a weighted network, constructed using chemical-chemical interaction information, to identify new chemicals related to two types of lung cancer: non-small lung cancer and small-cell lung cancer. Then, a randomization test as well as chemical-chemical interaction and chemical structure information were utilized to make further selections. A final analysis of these new chemicals in the context of the current literature indicates that several chemicals are strongly linked to lung cancer. PMID:26047514

  11. 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.

  12. 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.

  13. Metabolomics in chemical ecology.

    PubMed

    Kuhlisch, Constanze; Pohnert, Georg

    2015-07-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Chemical Evolution of Galaxies

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    Models of galactic chemical evolution study how the chemical elements have formed and dispersed in the Universe. During the Big Bang, only light elements, such as hydrogen (H), deuterium (D), helium (He), and a very tiny fraction of lithium (7Li) were formed, while all the other elements from carbon to uranium and beyond were formed inside the stars. The chemical elements and their isotopes are characterized by their mass number (A), namely, the sum of the protons and neutrons composing their nuclei. So, when we write 7Li, it means that A= 7 for Li. Elements with A = 5 and A = 8 do not exist because they would not be stable, elements with A = 9, 10, 11 are the isotopes of berillium (Be) and boron (B), which are formed, together with 6Li and some 7Li during spallation processes, which derive from the interaction between cosmic rays and interstellar atoms of carbon (C), nitrogen (N), and oxygen (O). All the elements with A ≥ 12 starting from 12C have been synthesized inside the stars and the sum of all of them in Astronomy is called metallicity and indicated with capital Z.

  18. 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)

  19. Chemical emergency preparedness program: chemical profiles. Interim guidance

    SciTech Connect

    Not Available

    1985-12-01

    The document, developed by the U.S. Environmental Protection Agency (USEPA) is part of the USEPA National Air Toxics Strategy. The document is provided in support of EPA Chemical Emergency Preparedness Program (CEPP) which deals with accidental release of acutely toxic chemicals. For each acutely toxic chemical listed in the CEPP guidance document (report number PB86-155256), a chemical profile is available. A chemical profile is a collection of information on the chemical identity hazardous identity, physical/chemical characteristics, fire and explosive hazard, reactivity, health hazard, use, and precautions for handling and use of the chemical. The information is presented in the format that conforms as closely as possible to the Occupational Safety and Health Administration (OSHA) recommended format for a Material Safety Data Sheet (MSDS).

  20. Devices for collecting chemical compounds

    SciTech Connect

    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.

  1. 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.

  2. Control in the Chemical Industry

    ERIC Educational Resources Information Center

    Jones, R. G.

    1974-01-01

    Discusses various control techniques used in chemical processes, including measuring devices, controller functions, control valves, and feedforward and feedback actions. Applications of control to a real chemical plant are exemplified. (CC)

  3. Chemical Sensing in Process Analysis.

    ERIC Educational Resources Information Center

    Hirschfeld, T.; And Others

    1984-01-01

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

  4. Chemical Educators Stress Industry Ties

    ERIC Educational Resources Information Center

    Worthy, Ward

    1975-01-01

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

  5. 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)

  6. Chemical sensor system

    DOEpatents

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

    2002-01-01

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

  7. Chemical and Biological Kinetics

    NASA Astrophysics Data System (ADS)

    Emanuel', N. M.

    1981-10-01

    Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.

  8. Chemical kinetics modeling

    SciTech Connect

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

    1993-12-01

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

  9. Lasers in chemical processing

    SciTech Connect

    Davis, J.I.

    1982-04-15

    The high cost of laser energy is the crucial issue in any potential laser-processing application. It is expensive relative to other forms of energy and to most bulk chemicals. We show those factors that have previously frustrated attempts to find commercially viable laser-induced processes for the production of materials. Having identified the general criteria to be satisfied by an economically successful laser process and shown how these imply the laser-system requirements, we present a status report on the uranium laser isotope separation (LIS) program at the Lawrence Livermore National Laboratory (LLNL).

  10. Exposing covert fragrance chemicals.

    PubMed

    Scheinman, P L

    2001-12-01

    Fragrance is the most common cosmetic allergen found when dermatitis patients are patch tested in the United States and in many places worldwide. Fragrances are ubiquitous in our daily lives and are present in items ranging from toiletries to toilet tissue. Although fragrances enhance the smell or mask unpleasant odors of various cosmetics and household items, it becomes very difficult for fragrance-allergic patients to find products they can use. Many items labeled unscented and fragrance-free contain esoteric fragrance chemicals that most consumers would not recognize. This article details some covert fragrance agents to help physicians better educate their fragrance-sensitive patients.

  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. Chemically functionalized surface patterning.

    PubMed

    Zhou, Xiaozhu; Boey, Freddy; Huo, Fengwei; Huang, Ling; Zhang, Hua

    2011-08-22

    Patterning substrates with versatile chemical functionalities from micro- to nanometer scale is a long-standing and interesting topic. This review provides an overview of a range of techniques commonly used for surface patterning. The first section briefly introduces conventional micropatterning tools, such as photolithography and microcontact printing. The second section focuses on the currently used nanolithographic techniques, for example, scanning probe lithography (SPL), and their applications in surface patterning. Their advantages and disadvantages are also demonstrated. In the last section, dip-pen nanolithography (DPN) is emphatically illustrated, with a particular stress on the patterning and applications of biomolecules.

  14. Chemical sensing flow probe

    DOEpatents

    Laguna, George R.; Peter, Frank J.; Butler, Michael A.

    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.

  15. 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.

  16. 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.

  17. Green chemistry for chemical synthesis.

    PubMed

    Li, Chao-Jun; Trost, Barry M

    2008-09-01

    Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign. PMID:18768813

  18. Quantitative Research in Chemical Education.

    ERIC Educational Resources Information Center

    Nurrenbern, Susan C.; Robinson, William R.

    1994-01-01

    Provides an overview of the area of quantitative research in chemical education, which involves the same components that comprise chemical research: (1) a question or hypothesis; (2) research design; (3) data collection and analysis; and (4) interpretation of results. Includes questions of interest to chemical educators; areas of quantitative…

  19. Chemical Waste and Allied Products.

    PubMed

    Hung, Yung-Tse; Aziz, Hamidi Abdul; Ramli, Siti Fatihah; Yeh, Ruth Yu-Li; Liu, Lian-Huey; Huhnke, Christopher Robert

    2016-10-01

    This review of literature published in 2015 focuses on waste related to chemical and allied products. The topics cover the waste management, physicochemical treatment, aerobic granular, aerobic waste treatment, anaerobic granular, anaerobic waste treatment, chemical waste, chemical wastewater, fertilizer waste, fertilizer wastewater, pesticide wastewater, pharmaceutical wastewater, ozonation. cosmetics waste, groundwater remediation, nutrient removal, nitrification denitrification, membrane biological reactor, and pesticide waste. PMID:27620094

  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. Mass Transfer with Chemical Reaction.

    ERIC Educational Resources Information Center

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  2. 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…

  3. 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…

  4. Green chemistry for chemical synthesis

    PubMed Central

    Li, Chao-Jun; Trost, Barry M.

    2008-01-01

    Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize by-products, designing new synthetic schemes and apparati that can simplify operations in chemical productions, and seeking greener solvents that are inherently environmentally and ecologically benign. PMID:18768813

  5. 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

  6. Chemical Waste and Allied Products.

    PubMed

    Hung, Yung-Tse; Aziz, Hamidi Abdul; Ramli, Siti Fatihah; Yeh, Ruth Yu-Li; Liu, Lian-Huey; Huhnke, Christopher Robert

    2016-10-01

    This review of literature published in 2015 focuses on waste related to chemical and allied products. The topics cover the waste management, physicochemical treatment, aerobic granular, aerobic waste treatment, anaerobic granular, anaerobic waste treatment, chemical waste, chemical wastewater, fertilizer waste, fertilizer wastewater, pesticide wastewater, pharmaceutical wastewater, ozonation. cosmetics waste, groundwater remediation, nutrient removal, nitrification denitrification, membrane biological reactor, and pesticide waste.

  7. Identification of Chemical Toxicity Using Ontology Information of Chemicals.

    PubMed

    Jiang, Zhanpeng; Xu, Rui; Dong, Changchun

    2015-01-01

    With the advance of the combinatorial chemistry, a large number of synthetic compounds have surged. However, we have limited knowledge about them. On the other hand, the speed of designing new drugs is very slow. One of the key causes is the unacceptable toxicities of chemicals. If one can correctly identify the toxicity of chemicals, the unsuitable chemicals can be discarded in early stage, thereby accelerating the study of new drugs and reducing the R&D costs. In this study, a new prediction method was built for identification of chemical toxicities, which was based on ontology information of chemicals. By comparing to a previous method, our method is quite effective. We hope that the proposed method may give new insights to study chemical toxicity and other attributes of chemicals.

  8. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to faciliate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  9. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1981-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  10. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate intallation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  11. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1984-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure, as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer.

  12. Chemical synthetic biology.

    PubMed

    Chiarabelli, Cristiano; Luisi, Pier Luigi

    2014-01-01

    Although both the most popular form of synthetic biology (SB) and chemical synthetic biology (CSB) share the biotechnologically useful aim of making new forms of life, SB does so by using genetic manipulation of extant microorganism, while CSB utilises classic chemical procedures in order to obtain biological structures which are non-existent in nature. The main query concerning CSB is the philosophical question: why did nature do this, and not that? The idea then is to synthesise alternative structures in order to understand why nature operated in such a particular way. We briefly present here some various examples of CSB, including those cases of nucleic acids synthesised with pyranose instead of ribose, and proteins with a reduced alphabet of amino acids; also we report the developing research on the "never born proteins" (NBP) and "never born RNA" (NBRNA), up to the minimal cell project, where the issue is the preparation of semi-synthetic cells that can perform the basic functions of biological cells.

  13. Chemical structure of interfaces

    NASA Technical Reports Server (NTRS)

    Grunthaner, F. J.

    1985-01-01

    The interfacial structure of silicon/dielectric and silicon/metal systems is particularly amenable to analysis using a combination of surface spectroscopies together with a variety of chemical structures of Si/SiO2, Si/SiO2Si3N4, Si/Si2N2O, Si/SiO2/Al, and Si/Native Oxide interfaces using high resolution (0.350 eV FWHM) X ray photoelectron spectroscopy. The general structure of these dielectric interfaces entails a monolayer chemical transition layer at the Si/dielectric boundary. Amorphous Si substrates show a wide variety of hydrogenated Si and Si(OH) sub x states that are not observed in thermal oxidation of single crystal material. Extended SiO2 layers greater than 8 A in thickness are shown to be stoichiometric SiO2, but to exhibit a wide variety of local network structures. In the nitrogen containing systems, an approach to stoichiometric oxynitride compounds with interesting impurity and electron trapping properties are seen. In native oxides, substantial topographical nonuniformity in oxide thickness and composition are found. Analysis of metal/oxide interfacial layers is accomplished by analytical removal of the Si substrate by UHV XeF2 dry etching methods.

  14. Early cosmic chemical evolution

    NASA Astrophysics Data System (ADS)

    Karlsson, T.

    2008-12-01

    The chemical abundance patterns observed in old and metal-poor stars in the Milky Way predominantly contain the signature of the first supernovae (SNe), and thus allow us to probe the first stars that formed in the universe. Of particular interest is the possible existence of a population of metal-free very massive stars, which are a natural consequence of current theoretical models for primordial star formation at the highest masses. As such, many of these stars would be destined to explode as so-called pair-instability supernovae (PISNe), thus becoming the first sources of metals in the universe. Here, I will argue that the apparent absence of the chemical signature of PISNe in extremely metal-poor (EMP) galactic halo stars may arise from an observational selection effect and should not, by necessity, be taken as an indication that our understanding of primordial star formation is incorrect. Whereas most surveys traditionally focus on the most metal-poor stars, early PISN enrichment is predicted to 'overshoot', reaching enrichment levels of [Ca/H]~- 2.5 that would be missed by current searches. It is further predicted, based on theoretical estimates for the relative number of PISNe, that the expected fraction of stars below [Ca/H]=-2 with a dominant (i.e. >90%) contribution from PISNe is only a few×10-4.

  15. Chemical simulation of greywater.

    PubMed

    Abed, Suhail Najem; Scholz, Miklas

    2016-01-01

    Sustainable water resources management attracts considerable attention in today's world. Recycling and reuse of both wastewater and greywater are becoming more attractive. The strategy is to protect ecosystem services by balancing the withdrawal of water and the disposal of wastewater. In the present study, a timely and novel synthetic greywater composition has been proposed with respect to the composition of heavy metals, nutrients and organic matter. The change in water quality of the synthetic greywater due to increasing storage time was monitored to evaluate the stability of the proposed chemical formula. The new greywater is prepared artificially using analytical-grade chemicals to simulate either low (LC) or high (HC) pollutant concentrations. The characteristics of the synthetic greywater were tested (just before starting the experiment, after two days and a week of storage under real weather conditions) and compared to those reported for real greywater. Test results for both synthetic greywater types showed great similarities with the physiochemical properties of published findings concerning real greywater. Furthermore, the synthetic greywater is relatively stable in terms of its characteristics for different storage periods. However, there was a significant (p < .05) reduction in 5-day biochemical oxygen demand (BOD5) for both low (LC) and high (HC) concentrations of greywater after two days of storage with reductions of 62% and 55%, respectively. A significant (p < .05) change was also noted for the reduction (70%) of nitrate-nitrogen (NO3-N) concerning HC greywater after seven days of storage. PMID:26745659

  16. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A.

    2011-05-20

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  17. 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

  18. 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).

  19. 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.

  20. Pressure Controlled Chemical Gardens.

    PubMed

    Bentley, Megan R; Batista, Bruno C; Steinbock, Oliver

    2016-06-30

    The dissolution of metal salts in silicate solution can result in the growth of hollow precipitate tubes. These "chemical gardens" are a model of self-organization far from the equilibrium and create permanent macroscopic structures. The reproducibility of the growth process is greatly improved if the solid salt seed is replaced by a salt solution that is steadily injected by a pump; however, this modification of the original experiment eliminates the membrane-based osmotic pump at the base of conventional chemical gardens and does not allow for analyses in terms of the involved pressure. Here we describe a new experimental method that delivers the salt solution according to a controlled hydrostatic pressure. In one form of the experiment, this pressure slowly decreases as zinc sulfate solution flows into the silicate-containing reaction vessel, whereas a second version holds the respective solution heights constant. In addition to three known growth regimes (jetting, popping, budding), we observe single tubes that fill the vessel in a horizontally undulating but vertically layered fashion (crowding). The resulting, dried product has a cylindrical shape, very low density, and one continuous connection from top to bottom. We also present phase diagrams of these growth modes and show that the flow characteristics of our experiments follow a reaction-independent Hagen-Poiseuille equation. PMID:27266993

  1. Chemical simulation of greywater.

    PubMed

    Abed, Suhail Najem; Scholz, Miklas

    2016-01-01

    Sustainable water resources management attracts considerable attention in today's world. Recycling and reuse of both wastewater and greywater are becoming more attractive. The strategy is to protect ecosystem services by balancing the withdrawal of water and the disposal of wastewater. In the present study, a timely and novel synthetic greywater composition has been proposed with respect to the composition of heavy metals, nutrients and organic matter. The change in water quality of the synthetic greywater due to increasing storage time was monitored to evaluate the stability of the proposed chemical formula. The new greywater is prepared artificially using analytical-grade chemicals to simulate either low (LC) or high (HC) pollutant concentrations. The characteristics of the synthetic greywater were tested (just before starting the experiment, after two days and a week of storage under real weather conditions) and compared to those reported for real greywater. Test results for both synthetic greywater types showed great similarities with the physiochemical properties of published findings concerning real greywater. Furthermore, the synthetic greywater is relatively stable in terms of its characteristics for different storage periods. However, there was a significant (p < .05) reduction in 5-day biochemical oxygen demand (BOD5) for both low (LC) and high (HC) concentrations of greywater after two days of storage with reductions of 62% and 55%, respectively. A significant (p < .05) change was also noted for the reduction (70%) of nitrate-nitrogen (NO3-N) concerning HC greywater after seven days of storage.

  2. 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...

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

    SciTech Connect

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

    1990-01-01

    The administration of chemicals at the maximum tolerated dose (MTD) in standard animal cancer tests is postulated to increase cell division (mitogenesis), which in turn increases rates of mutagenesis and thus carcinogenesis. The animal data are consistent with this mechanism, because a high proportion of all chemicals tested are indeed rodent carcinogens. We conclude that at the low doses of most human exposures, where cell killing does not occur, the hazards to humans of rodent carcinogens may be much lower than is commonly assumed. The toxicological significance of exposures to synthetic chemicals is examined in the context of exposures to naturally occurring chemicals. We calculate that 99.99% of the pesticides in the American diet are chemicals that plants produce to defend themselves. Only 52 natural pesticides have been tested in high-dose animal cancer tests, and about half (27) are rodent carcinogens; these 27 are shown to be present in many common foods. We conclude that natural and synthetic chemicals are equally likely to be positive in animal cancer tests. The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol and ethanol. The finding that in high-dose tests, a high proportion of both natural and synthetic chemicals are carcinogens, mutagens, teratogens, and clastogens (30-50% for each group) undermines current regulatory effects based on these tests to protect public health from low doses of synthetic chemicals.

  4. Recover chemicals from wastewater

    SciTech Connect

    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.

  5. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    The chemical vapor deposition (CVD) method for the growth of Si sheet on inexpensive substrate materials is investigated. The objective is to develop CVD techniques for producing large areas of Si sheet on inexpensive substrate materials, with sheet properties suitable for fabricating solar cells meeting the technical goals of the Low Cost Silicon Solar Array Project. Specific areas covered include: (1) modification and test of existing CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures, using standard and near-standard processing techniques.

  6. Groundwater and organic chemicals

    SciTech Connect

    Dawson, H.E.

    1995-12-01

    Groundwater is a major source of drinking water for many communities. Unfortunately, organic chemicals such as dry cleaning fluids, solvent, fuels, and pesticides have contaminated groundwater in many areas, rendering the groundwater useless as a drinking water resource. In many cases, the groundwater cannot be cleaned up with current technologies, particularly if the groundwater has been contaminated with immiscible (low solubility) organic liquids. In this talk, I will describe the path I have followed from geologist to geochemist and finally to environmental engineer. As a geologist, I studied the chemistry of rock metamorphosis. As a geochemist, I explored for gold and other metals. Now as an environmental engineer, I investigate the behavior of organic liquids in the subsurface. While these fields all appear very different, in reality I have always focused on the interaction of rocks or sediments with the fluids with which they come in contact.

  7. Concordant Chemical Reaction Networks

    PubMed Central

    Shinar, Guy; Feinberg, Martin

    2015-01-01

    We describe a large class of chemical reaction networks, those endowed with a subtle structural property called concordance. We show that the class of concordant networks coincides precisely with the class of networks which, when taken with any weakly monotonic kinetics, invariably give rise to kinetic systems that are injective — a quality that, among other things, precludes the possibility of switch-like transitions between distinct positive steady states. We also provide persistence characteristics of concordant networks, instability implications of discordance, and consequences of stronger variants of concordance. Some of our results are in the spirit of recent ones by Banaji and Craciun, but here we do not require that every species suffer a degradation reaction. This is especially important in studying biochemical networks, for which it is rare to have all species degrade. PMID:22659063

  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. 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.

  10. 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.

  11. 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.

  12. Chemical composition of Mars

    NASA Technical Reports Server (NTRS)

    Morgan, J. W.; Anders, E.

    1979-01-01

    The chemical composition of Mars is estimated from the cosmochemical model of Ganapathy and Anders (1974) with additional petrological and geophysical constraints. The model assumes that planets and chondrites underwent the same fractionation processes in the solar nebula, and constraints are imposed by the abundance of the heat-producing elements, U, Th and K, the volatile-rich component and the high density of the mantle. Global abundances of 83 elements are presented, and it is noted that the mantle is an iron-rich garnet wehrlite, nearly identical to the bulk moon composition of Morgan at al. (1978) and that the core is sulfur poor (3.5% S). The comparison of model compositions for the earth, Venus, Mars, the moon and a eucrite parent body suggests that volatile depletion correlates mainly with size rather than with radial distance from the sun.

  13. Chemical heat pump

    DOEpatents

    Greiner, Leonard

    1980-01-01

    A chemical heat pump system is disclosed for use in heating and cooling structures such as residences or commercial buildings. The system is particularly adapted to utilizing solar energy, but also increases the efficiency of other forms of thermal energy when solar energy is not available. When solar energy is not available for relatively short periods of time, the heat storage capacity of the chemical heat pump is utilized to heat the structure as during nighttime hours. The design also permits home heating from solar energy when the sun is shining. The entire system may be conveniently rooftop located. In order to facilitate installation on existing structures, the absorber and vaporizer portions of the system may each be designed as flat, thin wall, thin pan vessels which materially increase the surface area available for heat transfer. In addition, this thin, flat configuration of the absorber and its thin walled (and therefore relatively flexible) construction permits substantial expansion and contraction of the absorber material during vaporization and absorption without generating voids which would interfere with heat transfer. The heat pump part of the system heats or cools a house or other structure through a combination of evaporation and absorption or, conversely, condensation and desorption, in a pair of containers. A set of automatic controls change the system for operation during winter and summer months and for daytime and nighttime operation to satisfactorily heat and cool a house during an entire year. The absorber chamber is subjected to solar heating during regeneration cycles and is covered by one or more layers of glass or other transparent material. Daytime home air used for heating the home is passed at appropriate flow rates between the absorber container and the first transparent cover layer in heat transfer relationship in a manner that greatly reduce eddies and resultant heat loss from the absorbant surface to ambient atmosphere.

  14. 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 +/.

  15. The unfought chemical war

    SciTech Connect

    Freeman, K. )

    1991-12-01

    In December 1943, in the middle of the scorching northern Australia summer, a young Australian commando, Tom Mitchell, sweated in his respirator and gas-protective clothing as he got ready to take part in a mustard-gas experiment. He grimly watched six US aircraft, B-24 Liberators, drop bombs filled with mustard gas on Brook Island, near Innisfail in the state of Queensland. Ten minutes later, Mitchell was rushing around the island to tend sampling equipment. But a few hours later, he and another Australian soldier were ordered back onto the island - this time, stripped of their respirators and protective clothing. They were forced to camp on the island from dusk to dawn in ordinary clothing without any safety equipment. Mitchell now suffers from lung and heart disease. Last year, nearly 47 years after he was burned, Mitchell settled with the Australian government for $25,000 (Australian). Publicity over his lawsuit, filed in 1981, along with revelations made in a documentary film broadcast in Australia in 1989, has prompted thousands of other Australian survivors of chemical-warfare tests to ask the Australian Department of Veterans Affairs for disability benefits. Veterans of chemical-warfare tests are also breaking their silence in the United States and Canada, stepping forward to seek compensation for their injuries. The impetus behind the US revelations came from a campaign begun in 1989 by Cong. Porter Goss, a Florida Republican, to win benefits for four participants in US Navy mustard-gas tests. During a flurry of publicity in mid-June 1991, the Department of Veterans Affairs announced that it was relaxing its rules to make it easier for World War 2 mustard-gas victims to collect benefits. In Canada, an information hot line run by the Department of National Defense in 1988 and a 1989 book by John Bryden, Deadly Allies: Canada's Secret War 1937-1947, brought the tests to national attention.

  16. Chemical modification of asphalt

    SciTech Connect

    Ju, Ruei Fu.

    1989-01-01

    Desirable properties of asphalt pavements include high stability, flexibility, and durability. In order to achieve these properties, the asphalt should bind well with mineral aggregates and the properties of the resulting asphalt concrete should change as slowly as possible during service life. The interaction of water and asphaltic concrete under particular circumstances may cause stripping or loss of adhesion and consequential detachment of the asphalt from the aggregate. Use of aggregates treated with these polymer emulsions resulted in a much stronger bond at the asphalt-aggregate interface. Scanning electron microscope studies showed that a thin polymer film covers the aggregate surface. Ethylene-vinyl acetate copolymer resin 460, ethylene-vinyl acetate copolymer resin 240, styrene butadiene copolymer, cis-1,4-polybutadiene copolymer, and polyethylene were tested as additives. The effect of these on the resistance to permanent deformation and dynamic stiffness is described in this study. The chemical changes that occurred during weathering were also addressed. The effect of oxidation on aged asphalt was determined by measuring the change in infrared absorption with time of exposure. Antioxidants which are capable of decomposing peroxides were found to extend the durability of the asphalt. By observing the concentration of peroxy radicals during the course of a chemical process as indicated by electron spin resonance peak intensity, it was possible to obtain quantitative information on the interaction of antioxidants with peroxy radicals. Indications were obtained that antioxidants are not effective in reducing the brittleness of asphalt upon aging. The effect of six plasticizers on thermal and mechanical properties of asphalt was studied. In general, use of plasticizers resulted in lowered rigidity, increased ductility and increased toughness. Tricresyl phosphate was the most effective.

  17. Gas phase chemical detection with an integrated chemical analysis system

    SciTech Connect

    CASALNUOVO,STEPHEN A.; FRYE-MASON,GREGORY CHARLES; KOTTENSTETTE,RICHARD; HELLER,EDWIN J.; MATZKE,CAROLYN M.; LEWIS,PATRICK R.; MANGINELL,RONALD P.; BACA,ALBERT G.; HIETALA,VINCENT M.

    2000-04-12

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample preconcentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described.

  18. Gas Phase Chemical Detection with an Integrated Chemical Analysis System

    SciTech Connect

    Baca, Albert G.; Casalnuovo, Stephen A.; Frye-Mason, Gregory C.; Heller, Edwin J.; Hietala, Susan L.; Hietala, Vincent M.; Kottenstette, Richard J.; Lewis, Patrick R.; Manginell, Ronald P.; Matzke, Carloyn M.; Reno, John L.; Sasaki, Darryl Y.; Schubert, W. Kent

    1999-07-08

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample concentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described. The design and performance of novel micromachined acoustic wave devices, with the potential for improved chemical sensitivity, are also described.

  19. Chemical Engineering in Space

    NASA Technical Reports Server (NTRS)

    Lobmeyer, Dennis A.; Meneghelli, Barry J.

    2001-01-01

    The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit and escape the bonds of Earth's gravity. In the future there may be other means available; however, currently few of these alternatives can compare to the speed or the ease of use provided by cryogenic chemical propulsion agents. Cryogenics, the science and art of producing cold operating conditions, has become increasingly important to our ability to travel within our solar system. The production and transport of cryogenic fuels as well as the long-term storage of these fluids are necessary for mankind to travel within our solar system. It is with great care and at a significant cost that gaseous compounds such as hydrogen and oxygen are liquified and become dense enough to use for rocket fuel. As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a complete round-trip. The cost and the size of any expedition to another celestial body are extreme. If we are constrained by the need to take everything necessary (fuel, life support, etc.) for our survival and return, we greatly increase the risk of being able to go. As with the early explorers on Earth, we will need to harvest much of our energy and our life support from the celestial bodies. The in situ production of these energy sources is paramount to success. Due to the current propulsion system designs, the in-situ processes will require liquefaction and the application of cryogenics. The challenge we face for the near future is to increase our understanding of cryogenic long-term storage and off-world production of cryogenic fluids. We must do this all within the boundaries of very restricted size, weight, and robustness parameters so that we may launch these apparatus from Earth and utilize them elsewhere. Miniaturization, efficiency, and physically robust systems will all play a part in

  20. Cleavable linkers in chemical biology.

    PubMed

    Leriche, Geoffray; Chisholm, Louise; Wagner, Alain

    2012-01-15

    Interest in cleavable linkers is growing due to the rapid development and expansion of chemical biology. The chemical constrains imposed by the biological conditions cause significant challenges for organic chemists. In this review we will present an overview of the cleavable linkers used in chemical biology classified according to their cleavage conditions by enzymes, nucleophilic/basic reagents, reducing agents, photo-irradiation, electrophilic/acidic reagents, organometallic and metal reagents, oxidizing reagents.