Note: This page contains sample records for the topic tepid supergiants chemical from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Chemical compositions of Four B-type Supergiants in the SMC Wing  

Microsoft Academic Search

High-resolution UCLES\\/AAT spectra of four B-type supergiants in the SMC South\\u000aEast Wing have been analysed using non-LTE model atmosphere techniques to\\u000adetermine their atmospheric parameters and chemical compositions. The principle\\u000aaim of this analysis was to determine whether the very low metal abundances\\u000a($-$1.1 dex compared with Galactic value) previously found in the Magellanic\\u000aInter Cloud region (ICR) were

J.-K. Lee; W. R. J. Rolleston; P. L. Dufton; R. S. I. Ryans

2004-01-01

2

Chemical compositions of four B-type supergiants in the SMC wing  

NASA Astrophysics Data System (ADS)

High-resolution UCLES/AAT spectra of four B-type supergiants in the SMC South East Wing have been analysed using non-LTE model atmosphere techniques to determine their atmospheric parameters and chemical compositions. The principle aim of this analysis was to determine whether the very low metal abundances (-1.1 dex compared with Galactic value) previously found in the Magellanic Inter Cloud region (ICR) were also present in the SMC Wing. The chemical compositions of the four targets are similar to those found in other SMC objects and appear to be incompatible with those deduced previously for the ICR. Given the close proximity of the Wing to the ICR, this is difficult to understand and some possible explanations are briefly discussed.

Lee, J.-K.; Rolleston, W. R. J.; Dufton, P. L.; Ryans, R. S. I.

2005-01-01

3

The chemical composition of the post-asymptotic giant branch F supergiant CRL 2688  

NASA Astrophysics Data System (ADS)

We present an analysis of a high-resolution (R ˜ 50 000) optical spectrum of the central region of the protoplanetary nebula CRL 2688. This object is thought to have recently moved off the asymptotic giant branch (AGB) and displays abundance patterns of CNO and heavy elements that can provide us with important clues to help us understand the nucleosynthesis, dredge-up and mixing experienced by the envelope of the central star during its AGB stage of evolution. Analysis of the molecular features, presumably originating from circumstellar matter, provides further constraints on the chemistry and velocity of the expanding shell, expelled as a consequence of the strong mass loss experienced by the central star. We confirm that the central star shows a spectrum typical of an F-type supergiant with Teff = 7250 ± 400 K, log g = 0.5 and [Fe/H] = -0.3 ± 0.1 dex. We find that the abundance pattern of this object is characterized by enhancements of carbon ([C/Fe] = 0.6 ± 0.1), nitrogen ([N/Fe] = 1.0 ± 0.3) and Na ([Na/Fe] = 0.7 ± 0.1), similar to other previously known carbon-rich post-AGB stars. Yttrium is also enhanced, while the [Ba/Y] ratio is very low (-1.0), indicating that only the light s-process elements are enhanced. The zinc abundance is found to be normal, [Zn/Fe] = 0.0 ± 0.3, suggesting that there is no depletion of refractory elements. The H?, Na I and K I resonance lines show prominent emission components, the heliocentric radial velocities of which are offset by -41 ± 3 km s-1 relative to the photospheric metal-absorption lines. The molecular features of C2 and CN also show emission components, the velocities of which are consistent with the emission components of the H?, Na Iand K I lines. On the other hand, their absorption components are more highly blueshifted than the corresponding emission components, which suggests that the regions where the emission and absorption components arise are expanding at different velocities.

Ishigaki, Miho N.; Parthasarathy, Mudumba; Reddy, Bacham E.; García-Lario, Pedro; Takeda, Yoichi; Aoki, Wako; García-Hernández, D. Aníbal; Manchado, Arturo

2012-09-01

4

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

PubMed

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 gatekeeping in defense of population health. The principal recommendation is for increased use of financial incentives to reward physicians for compliance with recommended guidelines on antibiotic prescribing. Although not a panacea, greater experimentation with financial incentives can provide a much needed jump-start to physician interest in antibiotic conservation and likely best address physicians' legitimate clinical autonomy concerns. PMID:19216245

Saver, Richard S

2008-01-01

5

Detection of a weak surface magnetic field on Sirius A: are all tepid stars magnetic?  

NASA Astrophysics Data System (ADS)

Aims: We aim at a highly sensitive search for weak magnetic fields in main sequence stars of intermediate mass, by scanning classes of stars with no previously reported magnetic members. After detecting a weak magnetic field on the normal, rapidly rotating A-type star Vega, we concentrate here on the bright star Sirius A, taken as a prototypical, chemically peculiar, moderately rotating Am star. Methods: We employed the NARVAL and ESPaDOnS high-resolution spectropolarimeters to collect 442 circularly polarized spectra, complemented by 60 linearly polarized spectra. Using a list of about 1100 photospheric spectral lines, we computed a cross correlation line profile from every spectrum, leading to a signal-to-noise ratio of up to 30 000 in the polarized profile. Results: We report the repeated detection of circularly polarized, highly asymmetric signatures in the line profiles, interpreted as Zeeman signatures of a large-scale photospheric magnetic field, with a line-of-sight component equal to 0.2 ± 0.1 G. Conclusions: This is the first polarimetric detection of a surface magnetic field on an Am star. Using rough estimates of the physical properties of the upper layers of Sirius A, we suggest that a dynamo operating in the shallow convective envelope cannot account for the field strength reported here. Together with the magnetic field of Vega, this result confirms that a new class of magnetic objects exists among non Ap/Bp intermediate-mass stars, and it may indicate that a significant fraction of tepid stars are magnetic. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Petit, P.; Lignières, F.; Aurière, M.; Wade, G. A.; Alina, D.; Ballot, J.; Böhm, T.; Jouve, L.; Oza, A.; Paletou, F.; Théado, S.

2011-08-01

6

Molecular and dust shells around cool supergiants  

NASA Astrophysics Data System (ADS)

The last decade has witnessed a remarkable expansion of our knowledge of the chemistry occuring in the huge envelopes surrounding supergiants. The development of highly sophisticated infrared - submillimeter telescopes was crucial for this progress due their potential to detect gas-phase and solid-state species. Instruments such as Herschel, ISO, IRAM, APEX, SMA, etc. were key for these discoveries. The opening of ALMA end 2011 heralded the start of a new era thanks to an increase in sensitivity and spatial resolution of ca. 2 orders-of-magnitude. Although some supergiants have now been studied in quite some detail, a comprehensive understanding of the main chemical routes and the impact of some dominant physical processes is still lacking. In this talk, I give an overview of the current knowledge on the molecular and dust content in shells around supergiants. I discuss the importance of some chemical formation routes and their relation with some dynamical process. I end the talk with some suggestion for future research.

Decin, Leen

2013-06-01

7

Properties of Galactic B Supergiants  

NASA Astrophysics Data System (ADS)

Physical and wind properties of Galactic B supergiants are presented based upon non-LTE line blanketed model atmospheres, including Sher 25 toward the NGC 3603 cluster. We compare H? derived wind densities with recent results for SMC B supergiants and generally confirm theoretical expectations for stronger winds amongst Galactic supergiants. Mid B supergiant winds are substantially weaker than predictions from current radiatively driven wind theory, a problem which is exacerbated if winds are already clumped in the H? line forming region. We find that the so-called `bistability jump' at B1 (Teff ˜ 21kK) from Lamers et al. is rather a more gradual downward trend. CNO elemental abundances, including Sher 25, reveal partially processed material at their surfaces. In general, these are in good agreement with evolutionary predictions for blue supergiants evolving redward accounting for rotational mixing. A few cases, including HD 152236 (?1 Sco), exhibit strongly processed material which is more typical of Luminous Blue Variables. Our derived photospheric [N/O] ratio for Sher 25 agrees with that for its ring nebula, although a higher degree of CNO processing would be expected if the nebula originated during a red supergiant phase, as is suspected for the ring nebula ejected by the B supergiant progenitor of SN 1987A, Sk--69° 202. Sher 25 has an inferred age of ˜5 Myr in contrast with ˜2 Myr for HD 97950, the ionizing cluster of NGC 3603, so it may be a foreground object or close binary evolution may be responsible for its unusual location in the H-R diagram.

Crowther, P. A.; Lennon, D. J.; Walborn, N. R.; Smartt, S. J.

2008-06-01

8

The chemistry of dust formation in red supergiants  

NASA Astrophysics Data System (ADS)

Massive stars in their late stages of evolution as Red Supergiants experience mass loss. The resulting winds show various degrees of dynamical and chemical complexity and produce molecules and dust grains. This review summarises our knowledge of the molecular and dust components of the wind of Red Supergiants, including VY CMa and Betelgeuse. We discuss the synthesis of dust as a non equilibrium process in stellar winds, and present the current knowledge of the chemistry involved in the formation of oxygen-rich dust such as silicates and metal oxides.

Cherchneff, I.

2013-05-01

9

Massive compact binaries hosting supergiant stars  

NASA Astrophysics Data System (ADS)

In this review I first describe the nature of the three kinds of High-Mass X-ray Binaries (HMXBs), accreting through: i. Be circumstellar disk, ii. supergiant stellar wind, and iii. Roche lobe filling supergiants. I then report on the discovery of two new populations of HMXBs hosting supergiant stars, recently revealed by a wealth of new observations, coming from the high energy side (INTEGRAL, Swift, XMM, Chandra satellites), and complemented by multi-wavelength optical/infrared observations (mainly ESO facilities). The first population is constituted of obscured supergiant HMXBs, the second one of supergiant fast X-ray transients (SFXTs), exhibiting short and intense X-ray flares. I finally discuss the formation and evolution of HMXBs, constrain the accretion models (e.g. clumpy winds, transitory accretion disk, magneto-centrifugal barrier), show evidences suggesting the existence of an evolutionary link, include comparisons with population synthesis models, and finally build a consistent scenario explaining the various characteristics of these extreme celestial sources. Because they are the likely progenitors of Luminous Blue Variables (LBVs), and also of neutron star/black hole binary mergers, related to short/hard gamma-ray bursts, the knowledge of the nature, formation and evolution of these HMXB populations is of prime importance.

Chaty, Sylvain

2013-06-01

10

The Temperatures of Red Supergiants  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

11

Two Circumstellar Bubbles around Blue Supergiants in the LMC  

NASA Astrophysics Data System (ADS)

During its evolution, a massive star loses mass via stellar winds. A fast stellar wind may sweep up the ambient medium into a shell, appearing as a ``ring nebula" around the central star. While ring nebulae around Wolf-Rayet stars have received considerable attention in recent years, ring nebulae around O and B stars are far less well-explored. This is because very few well-defined rings around OB stars are known; in our Galaxy only two cases are known, the Bubble Nebula and NGC6164-5. Last year we discovered two ring nebulae around blue supergiants, Sk-69 279 (O9f; V=12.8 mag) and Sk-69 271 (B2; V=12.0 mag), in the Large Magellanic Cloud (Weis et al. 1995, RevMexAASC 3, 237). Both nebulae have diameter ~ 19'', corresponding to ~ 5 pc. To investigate the origin of these nebulae, we obtained long-slit H? +[N II] echelle observations with the 4m telescope at the Cerro Tololo Inter-American Observatory. The nebula around Sk-69 279 shows line-split indicating an expansion velocity of 27km s(-1) , while the nebula around Sk-69 271 shows no line-split, suggesting an expansion velocity <15km s(-1) . Assuming that t = 0.5 r/v, the dynamic age of these nebulae are 1x10(5) yr and >2x10(5) yr, respectively. The most tale-telling information comes from the [N II]/H? ratio. Both nebulae show [N II]/H? ratios significantly higher than those of the background H II emission. This behavior is typical for ring nebulae around WR stars or luminous blue variables that contain stellar nucleosynthesis processed material. Therefore, we conclude that the ring nebulae around Sk-69 279 and Sk-69 271 must be ``circumstellar bubbles" containing processed stellar material. These two blue supergiants must have evolved past the red supergiant phase. The chemical composition of these two ring nebulae could place constraints on models of stellar evolution.

Weis, K.; Chu, Y.-H.; Bomans, D. J.

1996-05-01

12

Fine structure line emission from supergiants  

NASA Astrophysics Data System (ADS)

We have detected (O I) 63 micron and (Si II) 35 micron emission from the oxygen-rich, M supergiants alpha Orionis (Betelgeuse), alpha Scorpii (Antares), and alpha Herculis (Rasalgethi). The measured fluxes indicate that the emission originates in dense, warm gas in the inner envelope or transition region where molecules and dust are expected to form and the acceleration of the wind occurs. Mass-loss rates are derived, evidence for time variability is presented, and results for other evolved stars are included.

Haas, Michael R.; Glassgold, Alfred E.; Tielens, Alexander G. G. M.

13

Theoretical Radial Pulsation Properties of Massive Yellow Supergiants  

NASA Astrophysics Data System (ADS)

We have studied the theoretical linear nonadiabatic radial pulsation periods and amplitude growth rates of two stellar models with initial masses of 30 and 40 solar masses. The intrinsic variability and dynamical properties of massive stars are very important to the understanding of the evolutionary behavior of these stars, especially those at, or near, the Humphreys-Davidson (H-D) Line, an empirically defined boundary in the upper portion of the H- R Diagram above which no stars are observed thus far to exist. Pulsation model parameters are derived from models we evolved for each initial mass. Initial chemical compositions are Y=0.28 and Z=0.02, and mass loss (according to the de Jager - Nieuwenhuijzen parameterization) and Livermore OPAL opacities are included in the modeling. Evolution was followed to core helium exhaustion, and all models are H-R Diagram first-crossing tracks; no blue loops occurred. Convection is treated using standard mixing length theory. As expected, the models did not exhibit radial pulsations blueward of an effective temperature of 6000 K. As yellow supergiants, we found them unstable to radial pulsation in an extension of the Classical Cepheid instability strip. The initial 30 solar mass model has a blue edge at 5700 K. The fundamental mode nonadiabatic pulsation period is 161 days, with an amplitude growth rate per period of 2%. At 5000 K, the period is 256 days, and the growth rate has greatly increased to 115%. The model's mass in this temperature interval is about 25.3 solar masses, and the luminosity is about 313000 solar luminosities. The initial 40 solar mass model has a blue edge at 5900 K, a period of 195 days, and a growth rate per period of 1.7%. At 4900 K, the period is 357 days, and the growth rate per period is 136%. Mass and luminosity here are about 32.3 and 527000 in solar units, respectively. While yellow supergiants, mass loss has not caused an enhancement of helium in the surface layers. For the initial 40 solar mass model, notable enhancement occurs when the star becomes a red supergiant, but this is not so for the lower initial mass model. For both models near their blue edges, helium ionization dominates as the pulsation driving mechanism. As the models evolve redwards, the pulsational driving contribution from the hydrogen ionization zone increases and becomes significant at about 5000 K. However, time dependent convection calculations may be necessary to model the effects of stronger convection at about this and cooler temperatures on the pulsational driving. If the very high growth rates calculated here indeed occur in real stars, it may be that the rapidly growing pulsations result in episodic ejections of mass of the tenuous outer layers of massive supergiants just below the H-D Line.

Soukup, M. S.; Cox, A. N.

1996-05-01

14

YELLOW SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)  

SciTech Connect

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.

Drout, Maria R.; Massey, Philip [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States); Meynet, Georges [Geneva University, Geneva Observatory, CH-1290 Versoix (Switzerland); Tokarz, Susan; Caldwell, Nelson, E-mail: maria-drout@uiowa.ed, E-mail: Phil.Massey@lowell.ed, E-mail: georges.meynet@unige.c, E-mail: tokarz@cfa.harvard.ed, E-mail: caldwell@cfa.harvard.ed [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2009-09-20

15

Yellow supergiants as supernova progenitors: an indication of strong mass loss for red supergiants?  

NASA Astrophysics Data System (ADS)

Context. The increasing number of observed supernova events allows for finding the progenitor star even more frequently in archive images. In a few cases, the progenitor star is a yellow supergiant star. The estimated position in the Hertzsprung-Russell diagram of these stars is not compatible with the theoretical tracks of classical single-star models. Aims: According to several authors, the mass-loss rates during the red supergiant phase could be underestimated. We study the impact of an increase in these mass-loss rates on the position of 12 to 15 M? stars at the end of their nuclear lives, in order to reconcile the theoretical tracks with the observed yellow supergiant progenitors. Methods: We have performed calculations of 12 to 15 M? rotating stellar models using the Geneva stellar evolution code. To account for the uncertainties in the mass-loss rates during the RSG phase, we increased the mass-loss rate of the star (between 3 and 10 times the standard one) during that phase and compared the evolution of stars undergoing such high mass-loss rates with models computed with the standard mass-loss prescription. Results: We show that the final position of the models in the Hertzsprung-Russell diagram depends on the mass loss they undergo during the red supergiant phase. With an increased mass-loss rate, we find that some models end their nuclear life at positions that are compatible with the observed position of several supernova progenitors. We conclude that an increased mass-loss rate (whose physical mechanism still needs to be clarified) allows single-star models to simultaneously reproduce the estimated position in the HRD of the YSG SN progenitors, as well as the SN type.

Georgy, C.

2012-02-01

16

PHOTOSPHERIC VARIATIONS OF THE SUPERGIANT {gamma} Cyg  

SciTech Connect

New high-resolution spectroscopic observations of the supergiant {gamma} Cyg (F8 Iab) taken between 2000 and 2008 consistently show strongly reversed-C-shaped bisectors for all unblended spectral lines. Small-amplitude variations in radial velocity and line shapes occur in an irregular manner with time scales {approx}100 days and longer. The radial velocities occasionally show changes as large as 2 km s{sup -1}, but much smaller changes are going on continuously. Differential line bisectors show shape changes and Doppler displacement characteristic of radial expansion and contraction. These might arise from non-periodic radial pulsation-like motions or from the appearance of giant convection cells that occupy most of the visible hemisphere of the star. Line-depth ratios are correlated with the line shifts on a seasonal basis and indicate temperature changes ranging up to {approx}15 K, with larger temperature occurring during times of most rapid contraction.

Gray, David F., E-mail: dfgray@uwo.c [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)

2010-11-15

17

The Red Supergiant Problem: Circumstellar dust as a solution  

NASA Astrophysics Data System (ADS)

We investigate the red supergiant problem: the apparent dearth of Type IIP supernova progenitors with masses between 16 and 30 M?. Although red supergiants with masses in this range have been observed, none have been identified as progenitors in pre-explosion images. We show that, by failing to take into account the additional extinction resulting from the dust produced in the red supergiant winds, the luminosity of the most massive red supergiants at the end of their lives is underestimated. We re-estimate the initial masses of all Type IIP progenitors for which observations exist and analyse the resulting population. We find that the most likely maximum mass for a Type IIP progenitor is 21+2 -1 M?. This is in closer agreement with the limit predicted from single star evolution models.

Walmswell, Joe; Eldridge, John

2012-09-01

18

Energy Distributions of B Supergiants in the Large Magellanic Cloud.  

National Technical Information Service (NTIS)

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)...

E. L. Fitzpatrick

1986-01-01

19

Mass-losing M supergiants in the solar neighborhood  

SciTech Connect

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. 60 refs.

Jura, M.; Kleinmann, S.G. (California Univ., Los Angeles (USA) Massachusetts Univ., Amherst (USA))

1990-08-01

20

Mass-losing M supergiants in the solar neighborhood  

NASA Astrophysics Data System (ADS)

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.

Jura, M.; Kleinmann, S. G.

1990-08-01

21

PACS and SPIRE spectroscopy of the red supergiant VY CMa  

NASA Astrophysics Data System (ADS)

With a luminosity >105 L? and a mass-loss rate of ~2 × 10-4 M? yr-1, the red supergiant VY CMa truly is a spectacular object. Because of its extreme evolutionary state, it could explode as supernova any time. Studying its circumstellar material, into which the supernova blast will run, provides interesting constraints on supernova explosions and on the rich chemistry taking place in such complex circumstellar envelopes. We have obtained spectroscopy of VY CMa over the full wavelength range offered by the PACS and SPIRE instruments of Herschel, i.e. 55-672 micron. The observations show the spectral fingerprints of more than 900 spectral lines, of which more than half belong to water. In total, we have identified 13 different molecules and some of their isotopologues. A first analysis shows that water is abundantly present, with an ortho-to-para ratio as low as ~1.3:1, and that chemical non-equilibrium processes determine the abundance fractions in the inner envelope. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Royer, P.; Decin, L.; Wesson, R.; Barlow, M. J.; Polehampton, E. T.; Matsuura, M.; Agúndez, M.; Blommaert, J. A. D. L.; Cernicharo, J.; Cohen, M.; Daniel, F.; Degroote, P.; De Meester, W.; Exter, K.; Feuchtgruber, H.; Gear, W. K.; Gomez, H. L.; Groenewegen, M. A. T.; Hargrave, P. C.; Huygen, R.; Imhof, P.; Ivison, R. J.; Jean, C.; Kerschbaum, F.; Leeks, S. J.; Lim, T.; Lombaert, R.; Olofsson, G.; Posch, T.; Regibo, S.; Savini, G.; Sibthorpe, B.; Swinyard, B. M.; Vandenbussche, B.; Waelkens, C.; Witherick, D. K.; Yates, J. A.

2010-07-01

22

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

Microsoft Academic Search

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,

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

2005-01-01

23

Wind Variability in Intermediate Luminosity B Supergiants  

NASA Astrophysics Data System (ADS)

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

Massa, Derck

1996-04-01

24

The physical properties of red supergiants  

NASA Astrophysics Data System (ADS)

Red supergiants (RSGs) are an evolved He-burning phase in the lifetimes of moderately high mass (10-25M?) stars. The physical properties of these stars mark them as an important and extreme stage of massive stellar evolution, but determining these properties has been a struggle for many years. The cool extended atmospheres of RSGs place them in an extreme position on the Hertzsprung-Russell diagram and present a significant challenge to the conventional assumptions of stellar atmosphere models. The dusty circumstellar environments of these stars can potentially complicate the determination of their physical properties, and unusual RSGs in the Milky Way and neighboring galaxies present a suite of enigmatic properties and behaviors that strain, and sometimes even defy, the predictions of stellar evolutionary theory. However, in recent years our understanding of RSGs, including the models and methods applied to our observations and interpretations of these stars, has changed and grown dramatically. This review looks back at some of the latest work that has progressed our understanding of RSGs, and considers the many new questions posed by our ever-evolving picture of these cool massive stars.

Levesque, Emily M.

2010-01-01

25

The Physical Properties of Red Supergiants  

NASA Astrophysics Data System (ADS)

Red supergiants (RSGs) are an He-burning phase in the evolution of moderately massive stars (10-25 Msun). For many years, the assumed physical properties of these stars placed them at odds with the predictions of evolutionary theory. We have recently determined new effective temperatures and luminosities for the RSG populations of galaxies with a factor of ~8 range in metallicity, including the Milky Way, the Magellanic Clouds, and M31. We find that these new physical properties greatly improve the agreement between the RSGs and the evolutionary tracks, although there are still notable difficulties with modeling the physical properties of RSGs at low metallicity. We have also examined several unusual RSGs, including VY CMa in the Milky Way, WOH G64 in the LMC, and a sample of four RSGs in the Magellanic Clouds, that show considerable variations in their physical parameters, most notably their effective temperatures. For all of these stars we re-examine their placement on the H-R diagram, where they have appeared to occupy the "forbidden" region to the right of the Hayashi track. We have updated current understanding of the physical properties of VY CMa and WOH G64; in the case of the unusual Magellanic Cloud variables, we conclude that these stars are undergoing an unstable evolutionary phase not previously associated with RSGs.

Levesque, E. M.

2010-06-01

26

Red supergiants around the obscured open cluster Stephenson 2  

NASA Astrophysics Data System (ADS)

Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red supergiants, is a strong candidate to be the most massive young cluster in the Galaxy. Aims: Stephenson 2 is located close to a region where a strong over-density of red supergiants had been found. We explore the actual cluster size and its possible connection to this over-density. Methods: Taking advantage of Virtual Observatory tools, we have performed a cross-match between the DENIS, USNO-B1 and 2MASS catalogues to identify candidate obscured luminous red stars around Stephenson 2, and in a control nearby region. More than 600 infrared bright stars fulfill our colour criteria, with the vast majority having a counterpart in the I band and >400 being sufficiently bright in I to allow observation with a 4-m class telescope. We observed a subsample of ~250 stars, using the multi-object, wide-field, fibre spectrograph AF2 on the WHT telescope in La Palma, obtaining intermediate-resolution spectroscopy in the 7500-9000 Å range. We derived spectral types and luminosity classes for all these objects and measured their radial velocities. Results: Our targets turned out to be G and K supergiants, late (? M4) M giants, and M-type bright giants (luminosity class II) and supergiants. We found ~35 red supergiants with radial velocities similar to Stephenson 2 members, spread over the two areas surveyed. In addition, we found ~40 red supergiants with radial velocities incompatible in principle with a physical association. Conclusions: Our results show that Stephenson 2 is not an isolated cluster, but part of a huge structure likely containing hundreds of red supergiants, with radial velocities compatible with the terminal velocity at this Galactic longitude (and a distance ~6 kpc). In addition, we found evidence of several populations of massive stars at different distances along this line of sight. Based on observations collected at the William Herschel Telescope (La Palma, Spain).Tables 2 and 3 are available in electronic form at http://www.aanda.org

Negueruela, I.; Marco, A.; González-Fernández, C.; Jiménez-Esteban, F.; Clark, J. S.; Garcia, M.; Solano, E.

2012-11-01

27

A detailed analysis of F-type supergiants. II Microturbulence distribution and element abundances in the atmosphere of Rho CAS  

NASA Astrophysics Data System (ADS)

A model atmosphere analysis is made of the supergiant Rho Cas (F8 Iap) on the basis of spectrograms with dispersions of 4 and 6 A/mm. The following values are obtained for the effective temperature and the surface gravity: Tef = 6000 K, lg g = 0.25. The Balmer lines observed in the spectrum of Rho Cas seem to be weaker than those calculated on the basis of the model atmosphere. It is suggested that the agreement between the theoretical and observed profiles of the Balmer series may be improved by giving up the assumption of local thermodynamic equilibrium. The abundances of 24 elements are determined, and it is shown that the chemical composition of the supergiant's atmosphere is similar to that of the solar atmosphere.

Boiarchuk, A. A.; Liubimkov, L. S.

28

B-Type Supergiants in the Magellanic Clouds  

NASA Astrophysics Data System (ADS)

The fact that early B-type supergiants lie in the theoretical blue Hertzsprung gap of the Hertzsprung-Russell Diagram is a long-standing problem in stellar evolution. This has led to considerable uncertainty over the evolutionary status of these stars: Do they indicate a bluewards extension of the hot core-helium-burning phase? If so, then are they pre-Red Supergiant (RSG) or post-RSG stars? Can one broaden the main sequence to partially fill this gap? Does binary evolution provide a significant channel for populating the gap? In this paper we discuss the properties of main-sequence stars and B-type supergiants within the context of the VLT-FLAMES Survey of Massive Stars, which has led to a paradigm shift in our understanding of massive-star evolution. We show that there is now strong evidence from consideration of surface nitrogen abundances in support of the idea that B-type supergiants do not evolve directly from the main sequence, and that rotational mixing may not be as dominant a process as was previously thought.

Lennon, D. J.; Trundle, C.; Hunter, I.; Smartt, S.; Dufton, P.; Evans, C.; Langer, N.; Brott, I.

2010-06-01

29

Another cluster of red supergiants close to RSGC1  

Microsoft Academic Search

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

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

2010-01-01

30

Empirical Determination of the Wind Velocity and Density Laws for the K Supergiant Zeta Aurigae  

NASA Astrophysics Data System (ADS)

We will derive the velocity and density laws and mass loss rate for the K4 supergiant in the eclipsing Zeta Aurigae binary system. The slow passage of the geometrically small B dwarf with its bright UV continuum behind the extended atmosphere of the K supergiant provides a splendid opportunity to probe the column densities and velocities of many absorption lines of various strengths as a function of stellar impact parameter. Our empirical determination of the wind physical parameters throughout the acceleration region will place tight constraints on the physical processes responsible for mass loss in evolved, massive stars that contribute significantly to the enrichment of the interstellar medium with chemically processed material. We request time for observations of lines of Fe I-II, Si II, Ti II, and V II at 6 orbital phases, including the terminal velocity wind, wind aceleration region, eclipse by the K star chromosphere, and total eclipse. This program is time critical but with typical tolerances of 1-7 days due to the long (972 day) orbital period.

Brown, Alexander

1992-07-01

31

Alfven waves in dusty winds of cool supergiant stars  

SciTech Connect

One of the most promising mechanisms that drive the winds of cool supergiant stars involves an outward-directed flux of Alfven waves. This mechanism can explain both the high mass-loss rate and the low terminal velocities of these winds. Many models were proposed using Alfven waves damping mechanisms such as surface resonant, non-linear, turbulent, or assuming a constant damping length. Since it is observed that late-type stars present great quantities of dust particles in their winds, we propose a damping mechanism for the waves that is caused due to their interaction with dust grains: the dust-cyclotron damping. We assume that particles are distributed over a range of sizes, implying a broad band of resonance frequencies. Our results show that this damping mechanism can accelerate the wind and reproduce observational data of cool supergiant stars, such as the mass-loss rate and the terminal velocity.

Vidotto, A.A.; Jatenco-Pereira, V. [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, USP, Rua do Matao 1226, 05508-900, Sao Paulo, SP (Brazil)

2005-09-28

32

Red supergiants as tracers of Perseus Arm structure  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

33

Another cluster of red supergiants close to RSGC1  

Microsoft Academic Search

Recent studies have revealed massive star clusters in a region of the Milky\\u000aWay close to the tip of the Long Bar. These clusters are heavily obscured and\\u000aare characterised by a population of red supergiants. We analyse a previously\\u000aunreported concentration of bright red stars ~16' away from the cluster RSGC1.\\u000aWe utilised near IR photometry to identify candidate

Ignacio Negueruela; Carlos Gonzalez-Fernandez; Amparo Marco; J. Simon Clark; Silvia Martinez-Nunez

2010-01-01

34

Observations of supergiant fast X-ray transients with LOFT  

NASA Astrophysics Data System (ADS)

Supergiant fast X-ray transients are a subclass of high mass X-ray binaries displaying a peculiar and still poorly understood extreme variability in the X-ray domain. These sources undergo short sporadic outbursts (L˜ 1036–1037 erg s?1), lasting few ks at the most, and spend a large fraction of their time in an intermediate luminosity state at about L˜ 1033–1034 erg s?1. The sporadic and hardly predictable outbursts of supergiant fast X-ray transients were so far best discovered by large field of view (FOV) coded-mask instruments; their lower luminosity states require, instead, higher sensitivity focusing instruments to be studied in sufficient details. In this contribution, we provide a summary of the current knowledge on supergiant fast X-ray transients and explore the contribution that the new space mission concept LOFT, the Large Observatory for X-ray Timing, will be able to provide in the field of research of these objects.

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

2013-05-01

35

X-Ray Emission from an Expanding Supergiant Shell in IC 2574  

Microsoft Academic Search

We present a multiwavelength study of a supergiant shell within the violent interstellar medium of the nearby dwarf galaxy IC 2574, which is a member of the M81 group of galaxies. Neutral hydrogen (H I) observations obtained with the Very Large Array (VLA) reveal a prominent expanding supergiant H I shell in the northeast quadrant of IC 2574 which is

Fabian Walter; Juergen Kerp; Neb Duric; Elias Brinks; Uli Klein

1998-01-01

36

The Yellow and Red Supergiants of M33  

NASA Astrophysics Data System (ADS)

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 ?7774 triplet. We examine ~1300 spectra in total and identify 121 YSGs (a sample that is unbiased in luminosity above log (L/L ?) ~ 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. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. MMT telescope time was granted by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by the National Science Foundation (NSF). This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.

Drout, Maria R.; Massey, Philip; Meynet, Georges

2012-05-01

37

THE YELLOW AND RED SUPERGIANTS OF M33  

SciTech Connect

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.

Drout, Maria R. [Center for Astrophysics, Harvard University, 60 Garden Street, M-S 10, Cambridge, MA 02138 (United States); Massey, Philip [Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001 (United States); Meynet, Georges, E-mail: mdrout@cfa.harvard.edu, E-mail: phil.massey@lowell.edu, E-mail: georges.meynet@unige.ch [Geneva Observatory, Geneva University, CH-1290 Versoix (Switzerland)

2012-05-10

38

Giant and supergiant stars with degenerate neutron cores  

NASA Astrophysics Data System (ADS)

Two classes of Thorne-Zytkow (TZ) stellar models are investigated: the giant models with low-mass envelopes and gravitational energy generation, and the super giant ones with more massive envelopes and nuclear energy generation. Bisnovatyi-Kogan and Lamzin (1984) argue that there is a flaw in the TZ match of the giant star's envelope onto their cores, that no equilibrium giant models will be possible when this flaw is corrected, and that such giant stars will turn out to die quickly via runaway neutrino losses and catastrophic contraction. The paper shows that Bisnovatyi-Kogan and Lamzin are mistaken: there is no flaw in the match to the core; fully self-consistent equilibrium models do exist; and the structure of those models suggests that they will be stable against neutrino-loss-triggered contraction. By contrast, there are genuine difficulties with the TZ supergiant models because their hot CNO cycle nuclear reactions get hung up waiting for beta-decays and thus have difficulty generating enough energy for hydrostatic support. An unsuccessful attempt to build self-consistent supergiant models based on a nonequilibrium hot CNO cycle is described.

Eich, Chris; Zimmermann, Mark E.; Thorne, Kip S.; Zytkow, Anna N.

1989-11-01

39

YELLOW AND RED SUPERGIANTS IN THE LARGE MAGELLANIC CLOUD  

SciTech Connect

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.

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

2012-04-20

40

Properties of Galactic early-type O-supergiants. A combined FUV-UV and optical analysis  

NASA Astrophysics Data System (ADS)

Aims: We aim to constrain the properties and evolutionary status of early and mid-spectral type supergiants (from O4 to O7.5). These posses the highest mass-loss rates among the O stars, and exhibit conspicuous wind profiles. Methods: Using the non-LTE wind code cmfgen we simultaneously analyzed the FUV-UV and optical spectral range to determine the photospheric properties and wind parameters. We derived effective temperatures, luminosities, surface gravities, surface abundances, mass-loss rates, wind terminal velocities, and clumping filling factors. Results: The supergiants define a very clear evolutionary sequence, in terms of ages and masses, from younger and more massive stars to older stars with lower initial masses. O4 supergiants cluster around the 3 Myr isochrone and are more massive than 60 M?, while the O5 to O7.5 stars have masses in the range 50-40 M? and are 4 ± 0.3 Myr old. The surface chemical composition is typical of evolved O supergiants (nitrogen-rich, carbon- and oxygen-poor). While the observed ranges of carbon and nitrogen mass-fractions are compatible with those expected from evolutionary models for the measured stellar masses, the N/C ratios as a function of age are inconsistent with the theoretical predictions for the four earliest (O4 spectral type) stars of the sample. We question the efficiency of rotational mixing as a function of age for these stars and suggest that another mechanism may be needed to explain the observed abundance patterns. Mass-loss rates derived with clumped-models range within a factor of three of the theoretical mass-loss rates. The corresponding volume-filling factors associated with small-scale clumping are 0.05 ± 0.02. Clumping is found to start close to the photosphere for all but three stars, two of which are fast rotators. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE) and by the NASA-ESA-SERC International Ultraviolet Explorer (IUE), and retrieved from the Multimission Archive at the Space Telescope Science Institute (MAST). Based on observations collected with the ELODIE spectrograph on the 1.93-m telescope (Observatoire de Haute-Provence, France). Based on observations collected with the FEROS instrument on the ESO 2.2 m telescope, program 074.D-0300 and 075.D-0061.Appendix A is available in electronic form at http://www.aanda.org

Bouret, J.-C.; Hillier, D. J.; Lanz, T.; Fullerton, A. W.

2012-08-01

41

Yellow Supergiants in the Small Magellanic Cloud: Putting Current Evolutionary Theory to the Test  

NASA Astrophysics Data System (ADS)

The yellow supergiant content of nearby galaxies provides a critical test of massive star evolutionary theory. While these stars are the brightest in a galaxy, they are difficult to identify because a large number of foreground Milky Way stars have similar colors and magnitudes. We previously conducted a census of yellow supergiants within M31 and found that the evolutionary tracks predict a yellow supergiant duration an order of magnitude longer than we observed. Here we turn our attention to the Small Magellanic Cloud (SMC), where the metallicity is 10× lower than that of M31, which is important as metallicity strongly affects massive star evolution. The SMC's large radial velocity (~160 km s-1) allows us to separate members from foreground stars. Observations of ~500 candidates yielded 176 near-certain SMC supergiants, 16 possible SMC supergiants, along with 306 foreground stars, and provide good relative numbers of yellow supergiants down to 12 M sun. Of the 176 near-certain SMC supergiants, the kinematics predicted by the Besançon model of the Milky Way suggest a foreground contamination of <=4%. After placing the SMC supergiants on the Hertzsprung-Russell diagram (HRD) and comparing our results to the Geneva evolutionary tracks, we find results similar to those of the M31 study: while the locations of the stars on the HRD match the locations of evolutionary tracks well, the models overpredict the yellow supergiant lifetime by a factor of 10. Uncertainties about the mass-loss rates on the main sequence thus cannot be the primary problem with the models.

Neugent, Kathryn F.; Massey, Philip; Skiff, Brian; Drout, Maria R.; Meynet, Georges; Olsen, Knut A. G.

2010-08-01

42

YELLOW SUPERGIANTS IN THE SMALL MAGELLANIC CLOUD: PUTTING CURRENT EVOLUTIONARY THEORY TO THE TEST  

SciTech Connect

The yellow supergiant content of nearby galaxies provides a critical test of massive star evolutionary theory. While these stars are the brightest in a galaxy, they are difficult to identify because a large number of foreground Milky Way stars have similar colors and magnitudes. We previously conducted a census of yellow supergiants within M31 and found that the evolutionary tracks predict a yellow supergiant duration an order of magnitude longer than we observed. Here we turn our attention to the Small Magellanic Cloud (SMC), where the metallicity is 10x lower than that of M31, which is important as metallicity strongly affects massive star evolution. The SMC's large radial velocity ({approx}160 km s{sup -1}) allows us to separate members from foreground stars. Observations of {approx}500 candidates yielded 176 near-certain SMC supergiants, 16 possible SMC supergiants, along with 306 foreground stars, and provide good relative numbers of yellow supergiants down to 12 M {sub sun}. Of the 176 near-certain SMC supergiants, the kinematics predicted by the Besancon model of the Milky Way suggest a foreground contamination of {<=}4%. After placing the SMC supergiants on the Hertzsprung-Russell diagram (HRD) and comparing our results to the Geneva evolutionary tracks, we find results similar to those of the M31 study: while the locations of the stars on the HRD match the locations of evolutionary tracks well, the models overpredict the yellow supergiant lifetime by a factor of 10. Uncertainties about the mass-loss rates on the main sequence thus cannot be the primary problem with the models.

Neugent, Kathryn F.; Massey, Philip; Skiff, Brian [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States); Drout, Maria R. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States); Meynet, Georges [Geneva Observatory, Geneva University, CH-1290 Versoix (Switzerland); Olsen, Knut A. G., E-mail: kneugent@lowell.ed, E-mail: phil.massey@lowell.ed, E-mail: bas@lowell.ed, E-mail: maria-drout@uiowa.ed, E-mail: georges.meynet@unige.c, E-mail: kolsen@noao.ed [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85748 (United States)

2010-08-20

43

Polarimetry and the Envelopes of Magellanic B[e] Supergiants  

NASA Astrophysics Data System (ADS)

We discuss the nature of the circumstellar envelopes around the B[e] supergiants (B[e]SG) in the Magellanic Clouds (MC). Contrary to those in the Galaxy, the MC B[e]SG have a well defined luminosity and can be considered members of a well defined class. We discuss spectroscopy and optical broadband polarimetry and spectropolarimetry data. These data show for the first time detailed changes in the polarization across several spectral features. We show that the envelopes of the B[e]SG are generally variable. Broadband polarimetry data show that the envelopes are definitely non-spherically symmetric and large non-axisymmetric ejections may occur. In addition to that, spectropolarimetry is coming of age as a tool to study the B[e]SG envelope structure.

Magalhães, A. M.; Melgarejo, R.; Pereyra, A.; Carciofi, A. C.

2006-12-01

44

Nonthermal X-ray emission from winds of OB supergiants  

SciTech Connect

The mechanisms responsible for the hard X-ray emission of OB supergiants (OBSGs) are investigated theoretically, modifying the periodic-shock model of Lucy (1982). The physical processes discussed include (1) the particle acceleration (PA) mechanism and its effect on the structure of individual shocks, (2) the energy cutoff and spectral index of the relativistic electrons and ions, and (3) the efficiency of PA by shocks and its implications for the number densities of relativistic particles. The model is used to predict the spectrum and intensity of the dominant nonthermal X-ray emission source from OBSGs, and the results are shown to be in good agreement with Einstein Observatory Solid-State Spectrometer observations of three OBSGs in Orion (Cassinelli and Swank, 1983). It is inferred that the surface magnetic fields of OBSGs are no greater than a few G, and that the PA rates are significantly lower than generally predicted for collisionless astrophysical shocks. 66 refs.

Chen, W.; White, R.L. (Johns Hopkins Univ., MD (USA) Space Telescope Science Institute, Baltimore, MD (USA))

1991-01-01

45

Supergiant Complexes of Solar Activity and Convection Zone  

NASA Astrophysics Data System (ADS)

The global distribution of solar surface activity (active regions) is apparently connected with processes in the convection zone. The large-scale magnetic structures above the tachocline could in a pronounced way be observable in the surface magnetic field. To get the information regarding large-scale magnetic formations in the convection zone, a set of solar synoptic charts (Mount Wilson 1998 - 2004, Fe i, 525.02 nm) have been analyzed. It is shown that the longitudinal dimensions and dynamics of supergiant complexes of solar surface activity carry valuable information about the processes in the convection zone of the Sun. A clear effect of large-scale (global) turbulence is found. This is a `fingerprint' of deep convection, because there are no such large-scale turbulent eddies in the solar photosphere. The preferred scales of longitudinal variations in surface solar activity are revealed. These are: ˜ 24° (gigantic convection cells), 90°, 180° and 360°.

Arkhypov, O. V.; Antonov, O. V.; Khodachenko, M. L.

2011-05-01

46

Magnetic Fields and Convection in the Cool Supergiant Betelgeuse  

NASA Astrophysics Data System (ADS)

We present the outcome of a highly-sensitive search for magnetic fields on the cool supergiant Betelgeuse. A time-series of six circularly polarized spectra was obtained using the NARVAL spectropolarimeter at Télescope Bernard Lyot (Pic du Midi Observatory (F)), between March and April 2010. Zeeman signatures were repeatedly detected in cross-correlation profiles, corresponding to a longitudinal component of about 1 G. The time-series unveils a smooth increase of the longitudinal field from 0.5 to 1.5 G, correlated with radial velocity fluctuations. We observe a strong asymmetry of Stokes V signatures, also varying in correlation with the radial velocity. The Stokes V line profiles are red-shifted by about 9 km s-1 with respect to the Stokes I profiles, suggesting that the observed magnetic elements may be concentrated in the sinking components of the convective flows.

Petit, P.; Aurière, M.; Konstantinova-Antova, R.; Morgenthaler, A.; Perrin, G.; Roudier, T.; Donati, J.-F.

47

Swift's Christmas Burst From Blue Supergiant Star Explosion  

NASA Video Gallery

GRB 101225A, better known as the "Christmas burst," was an unusually long-lasting gamma-ray burst. Because its distance was not measured, astronomers came up with two radically different interpretations. In the first, a solitary neutron star in our own galaxy shredded and accreted an approaching comet-like body. In the second, a neutron star is engulfed by, spirals into and merges with an evolved giant star in a distant galaxy. Now, thanks to a measurement of the Christmas burst’s host galaxy, astronomers have determined that it represented the collapse and explosion of a supergiant star hundreds of times larger than the sun. Credit: NASA's Goddard Space Flight Center Scientific Visualization Studio

Lynn Jenner

2013-04-16

48

Circumstellar dust as a solution to the red supergiant supernova progenitor problem  

NASA Astrophysics Data System (ADS)

We investigate the red supergiant problem, the apparent death of Type IIP supernova progenitors with masses between 16 and 30 M?. Although red supergiants with masses in this range have been observed, none has been identified as progenitors in pre-explosion images. We show that, by failing to take into account the additional extinction resulting from the dust produced in the red supergiant winds, the luminosity of the most massive red supergiants at the end of their lives is underestimated. We re-estimate the initial masses of all Type IIP progenitors for which observations exist and analyse the resulting population. We find that the most likely maximum mass for a Type IIP progenitor is ?. This is in closer agreement with the limit predicted from single star evolution models.

Walmswell, Joseph J.; Eldridge, John J.

2012-01-01

49

The energy distributions of B supergiants in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

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.

Fitzpatrick, E. L.

1986-09-01

50

Non-LTE Line-blanketed Stellar Wind Atmosphere Models for the A-supergiant Deneb  

Microsoft Academic Search

We present non-LTE metal line-blanketed stellar wind atmosphere models and synthetic spectra for comparison with the spectral energy distribution of the A-supergiant Deneb from UV to radio wavelengths. Deneb is alone among A-supergiants in having both a precisely measured angular diameter from the Navy Prototype Optical Interferometer (Nordgren, T. et al., 1999, priv. comm.) and a positive detection at centimeter

J. P. Aufdenberg; P. H. Hauschildt; E. Baron

1999-01-01

51

Radii and Effective Temperatures for G, K, and M Giants and Supergiants  

Microsoft Academic Search

Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 69 giant and supergiant stars are presented. Spectral types of the 59 giant stars generally lie between G6 and M6, although a B7 giant is included; the nine bright giants and supergiants have spectral types between F5 and M5. Comparison of the results to those from the IR

G. T. van Belle; R. R. Thompson; A. F. Boden; M. M. Colavita; P. J. Dumont; D. W. Mobley; D. Palmer; M. Shao; G. X. Vasisht; J. K. Wallace; M. J. Creech-Eakman; C. D. Koresko; S. R. Kulkarni; X. P. Pan; J. Gubler

1999-01-01

52

Supergiant Fast X-Ray Transients: A Common Behaviour or a Class of Objects?  

NASA Astrophysics Data System (ADS)

INTEGRAL monitoring of the Galactic Plane is revealing a growing number of recurrent X-ray transients, characterised by short outbursts with very fast rise times (~ tens of minutes) and typical durations of a few hours. A substantial fraction of these sources are associated with OB supergiants and hence define a new class of massive X-ray binaries, which we call Supergiant Fast X-ray Transients. Characterisation of the astrophysical parameters of their counterparts is underway. So far, we have found a number of late O and early B supergiants of different luminosities at a large range of distances. Nothing in their optical properties sets them apart from classical Supergiant X-ray Binaries. On the other hand, there is now rather concluding evidence that persistent supergiant X-ray binaries also show fast outbursts. This suggests a continuum of behaviours between typical persistent supergiant systems and purely transient systems, but offers very little information about the physical causes of the outbursts.

Negueruela, I.; Smith, D. M.; Torrejón, J. M.; Reig, P.

53

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

SciTech Connect

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

Kastner, Joel H. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Buchanan, Catherine [School of Physics, University of Melbourne, Victoria, 3010 (Australia); Sahai, Raghvendra [NASA/JPL, 4800 Oak Grove Drive, Pasadena, CA 1109 (United States); Forrest, William J. [Department of Physics and Astronomy, University of Rochester, Bausch and Lomb Hall, P.O. Box 270171, Rochester, NY 14627-0171 (United States); Sargent, Benjamin A., E-mail: jhk@cis.rit.ed, E-mail: clb@unimelb.edu.a [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-05-15

54

A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars  

NASA Astrophysics Data System (ADS)

Rotational velocity vsin i and mean radial velocity are presented for a sample of 231 Ib supergiant stars covering the spectral region F, G and K. This work is the second part of the large survey carried out with the CORAVEL spectrometer to establish the behavior of the rotation for stars evolving off the main sequence (De Medeiros & Mayor 1999). These data will add constraints to the study of the rotational behavior in evolved stars, as well as solid information concerning tidal interactions in binary systems and on the link between rotation, chemical abundance and activity in stars of intermediate masses. Based on observations collected at the Haute-Provence Observatory, Saint-Michel, France and at the European Southern Observatory, La Silla, Chile Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/395/97

De Medeiros, J. R.; Udry, S.; Burki, G.; Mayor, M.

2002-11-01

55

The chromium and titanium abundances in the atmospheres of A, F, and G supergiants in the solar neighborhood  

NASA Astrophysics Data System (ADS)

The abundances of two chemical elements of the iron group, viz., Cr and Ti, were determined by their high-resolution spectra for 22 A, F, and G supergiants in the solar neighborhood (within 700 pc). The titanium and chromium abundances were obtained using the Cr II and Ti II lines. The average chromium abundance of log?(Cr) = 5.70 ± 0.13 within the error limit corresponds to the solar abundance of log??(Cr) = 5.64. The average titanium abundance of log?(Ti) = 4.89 ± 0.10 within the error limit is very close to the solar abundance of log??(Ti) = 4.95. The average Cr and Ti abundances may be indicative of the fact that the average metallicity of young closely located stars is identical to that of the Sun.

Poklad, D. B.

2013-06-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

57

Expected angular separations of late-type supergiant +B star binaries in the Milky Way and LMC  

NASA Astrophysics Data System (ADS)

The authors develop a model for the binary frequencies of late-type supergiants. The model incorporates the semimajor-axis limitations imposed by Roche lobe overflow and is flexible enough to include the observational constraints imposed by various observing procedures. In particular, constraints on the minimum observable velocity amplitudes of the primaries and the presence of hot secondaries - observed in the UV - are predicted and found to be in excellent agreement with existing observations. The model is then used to predict the expected distribution of angular separations of late-type galactic supergiants and luminous M supergiants in the LMC. It is shown that the interferometer proposed by Massa and Endal (1987) should be capable of "resolving" more than 40 galactic Cepheid binaries, about 400 nonvariable large-type galactic supergiant binaries, and 25 M supergiant binaries in the LMC.

Massa, Derck; Endal, Andrew S.

1987-03-01

58

Rapidly Accreting Supergiant Protostars: Embryos of Supermassive Black Holes?  

NASA Astrophysics Data System (ADS)

Direct collapse of supermassive stars (SMSs) is a possible pathway for generating supermassive black holes in the early universe. It is expected that an SMS could form via very rapid mass accretion with \\dot{M}_*\\sim 0.1{--}1 \\,M_\\odot \\,yr^{-1} during the gravitational collapse of an atomic-cooling primordial gas cloud. In this paper, we study how stars would evolve under such extreme rapid mass accretion, focusing on the early evolution until the stellar mass reaches 103 M ?. To this end, we numerically calculate the detailed interior structure of accreting stars with primordial element abundances. Our results show that for accretion rates higher than 10-2 M ? yr-1, stellar evolution is qualitatively different from that expected at lower rates. While accreting at these high rates, the star always has a radius exceeding 100 R ?, which increases monotonically with the stellar mass. The mass-radius relation for stellar masses exceeding ~100 M ? follows the same track with R *vpropM 1/2 * in all cases with accretion rates >~ 10-2 M ? yr-1 at a stellar mass of 103 M ?, the radius is ~= 7000 R ? (sime 30 AU). With higher accretion rates, the onset of hydrogen burning is shifted toward higher stellar masses. In particular, for accretion rates exceeding \\dot{M}_*\\gtrsim 0.1 \\,M_\\odot \\,yr^{-1}, there is no significant hydrogen burning even after 103 M ? have accreted onto the protostar. Such "supergiant" protostars have effective temperatures as low as T eff ~= 5000 K throughout their evolution and because they hardly emit ionizing photons, they do not create an H II region or significantly heat their immediate surroundings. Thus, radiative feedback is unable to hinder the growth of rapidly accreting stars to masses in excess of 103 M ? as long as material is accreted at rates \\dot{M}_*\\gtrsim 10^{-2} \\,M_\\odot \\,yr^{-1}.

Hosokawa, Takashi; Omukai, Kazuyuki; Yorke, Harold W.

2012-09-01

59

The main sequence of three red supergiant clusters  

NASA Astrophysics Data System (ADS)

Massive clusters in our Galaxy are an ideal testbed to investigate the properties and evolution of high-mass stars. They provide statistically significant samples of massive stars of uniform ages. To accurately determine the intrinsic physical properties of these stars, we need to establish the distances, ages and reddening of the clusters. One avenue to achieve this is the identification and characterization of the main-sequence (MS) members of red supergiant (RSG) rich clusters. Here, we utilize publicly available data from the UKIDSS Galactic Plane Survey. We show that point spread function photometry in conjunction with standard photometric decontamination techniques allows us to identify the most likely MS members in the 10-20 Myr old clusters RSGC 1-3. We confirm the previous detection of the MS in RSGC 2 and provide the first MS detection in RSGC 1 and RSGC 3. There are in excess of 100 stars with more than 8 M? identified in each cluster. These MS members are concentrated towards the spectroscopically confirmed RSG stars. We utilize the J - K colours of the bright MS stars to determine the K-band extinction towards the clusters. The differential reddening is three times as large in the youngest cluster RSGC 1 as compared to the two older clusters RSGC 2 and RSGC 3. Spectroscopic follow-up of the cluster MS stars should lead to more precise distance and age estimates for these clusters as well as the determination of the stellar mass function in these high-mass environments.

Froebrich, Dirk; Scholz, Alexander

2013-09-01

60

On the Explosion Geometry of Red Supergiant Stars  

NASA Astrophysics Data System (ADS)

From progenitor studies, type II-Plateau supernovae (SNe II-P) have been decisively and uniquely determined to arise from isolated red supergiant stars, establishing the most homogeneous --- and well understood --- progenitor class of any type of core-collapse supernova. The precise nature of the mechanism responsible for the stellar explosion, however, remains the subject of considerable debate. A fundamental clue to the nature of the explosion mechanism is explosion geometry: In short, are supernovae round? Because young supernova atmospheres are electron-scattering dominated, their net linear polarization provides a direct probe of early-time supernova geometry, with higher degrees of polarization generally indicating greater departures from spherical symmetry. Here we present spectropolarimetry data for the most well-sampled SN II-P to date, SN 2008bk, and compare (and contrast) the results with those obtained for SN 2004dj, the only other SN II-P for which spectropolarimetry data were obtained with similar fine temporal sampling before, during, and after the fall off of the photometric plateau (Leonard et al. 2006). Both objects are polarized, indicating departures from spherical symmetry, although the timing of the onset -- as well as the persistence -- of the polarization differ between the two objects. Curiously, the detailed spectropolarimetric characteristics of the two objects at the epochs of recorded maximum polarization are extremely similar, feature by feature, suggesting a common cause --- or, at least, geometry. We interpret the data in light of non-Local-Thermodynamic Equilibrium, time-dependent radiative-transfer simulations specifically crafted for SN II-P ejecta. DCL acknowledges support from NSF grant AST-1009571, under which part of this research was carried out. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under observing programs 081.D-0128, 082.D-0151, and 085.D-0391 (PI: Dessart).

Leonard, Douglas C.; Dessart, L.; Hillier, D.; Pignata, G.

2012-01-01

61

SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR  

SciTech Connect

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

Van Dyk, Schuyler D.; Elias-Rosa, Nancy [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Davidge, Tim J., E-mail: vandyk@ipac.caltech.edu, E-mail: tim.davidge@nrc.ca [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, B.C., V9E 2E7 (Canada); and others

2012-01-15

62

Are the red supergiants Epsilon Peg and 12 PUP victims of mild s-processing?  

NASA Astrophysics Data System (ADS)

An abundance analysis of eight G and K supergiants has been performed with particular emphasis on two stars, Epsilon Peg and 12 Pup. It has been reported (Kovacs, 1983) that these two stars exhibit selective enhancement of Ba and, in the case of 12 Pup, Sr. Such a pattern of abundance enhancement would occur for very mild s-processing followed by extensive pollution of the star's outer envelope with this processed material. This type of mixing is not predicted by current models of stellar evolution. The previous Ba and Sr abundances were based on very strong lines of Ba II and Sr II and such lines are sensitive to microturbulence and conditions in the higher layers of the stellar atmosphere. This analysis compares the Ba II and Sr II line-strengths in Epsilon Peg and 12 Pup with six other cool supergiants and also utilizes weak Ba I and Sr I lines seen in the spectra of these stars. No enhancements of Ba or Sr, relative to the other supergiants, are found for Epsilon Peg or 12 Pup. In addition, calculations of the abundances produced by mild s-processing followed by extensive mixing with the outer envelope show that Co and Sc should also be enhanced substantially. Such enhancements are not observed in any of the supergiants.

Smith, Verne V.; Lambert, David L.

1987-06-01

63

Radii and Effective Temperatures of Giant and Supergiant Stars as Measured at the Palomar Testbed Interferometer  

Microsoft Academic Search

Using the Palomar Testbed Interferometer (PTI), we have measured angular diameters in the H and K bands for over 50 giant and supergiant stars, ranging in spectral type from A2 to M8. These diameters are part of an ongoing observational program at PTI to empirically establish effective temperatures and linear radii for these stars, in combination with existing photometry and

G. T. van Belle; R. R. Thompson

2000-01-01

64

The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought  

Microsoft Academic Search

We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members of OB associations or clusters with known distances, allowing a critical comparison with modern stellar evolutionary tracks. We find we can achieve excellent matches between the observations and the reddened model fluxes

Emily M. Levesque; Philip Massey; K. A. G. Olsen; Bertrand Plez; Eric Josselin; Andre Maeder; Georges Meynet

2005-01-01

65

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

Microsoft Academic Search

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

Richard B. Stothers; Chao-Wen Chin

1995-01-01

66

RADII AND EFFECTIVE TEMPERATURES FOR G, K, AND M GIANTS AND SUPERGIANTS G. T. VAN BELLE AND B. F. LANE  

Microsoft Academic Search

Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 69 giant and supergiant stars are presented. Spectral types of the 59 giant stars generally lie between G6 and M6, although a B7 giant is included; the nine bright giants and supergiants have spec- tral types between F5 and M5. Comparison of the results to those from the

R. R. THOMPSON; A. F. BODEN; M. M. COLAVITA; P. J. DUMONT; D. W. MOBLEY; D. PALMER; M. SHAO; G. X. VASISHT; J. K. WALLACE; M. J. CREECH-EAKMAN; C. D. KORESKO; S. R. KULKARNI; X. P. PAN; J. GUBLER

67

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

68

Macroturbulent and rotational broadening in the spectra of B-type supergiants  

Microsoft Academic Search

The absorption-line spectra of early B-type supergiants show significant broadening that im- plies that an additional broadening mechanism (characterized here as 'macroturbulence') is present in addition to rotational broadening. Using high-resolution spectra with signal-to-noise ratios of typically 500, we have attempted to quantify the relative contributions of rotation and macroturbulence, but even with data of this quality significant problems were

R. S. I. Ryans; P. L. Dufton; W. R. J. Rolleston; D. J. Lennon; F. P. Keenan; J. V. Smoker; D. L. Lambert

2002-01-01

69

The Effective Temperatures and Physical Properties of Magellanic Cloud Red Supergiants: The Effects of Metallicity  

Microsoft Academic Search

We present moderate-resolution spectrophotometry of 36 red supergiants (RSGs) in the LMC and 37 RSGs in the SMC. Using the MARCS atmosphere models to fit this spectrophotometry, we determine the stars' physical properties and compare the results to evolutionary models. The (V-R)0 broadband colors agree with those from fitting the optical spectrophotometry, but (V-K)0 results show metallicity-dependent systematic differences in

Emily M. Levesque; Philip Massey; K. A. G. Olsen; Bertrand Plez; Georges Meynet; Andre Maeder

2006-01-01

70

Radii and Effective Temperatures of Giant and Supergiant Stars as Measured at the Palomar Testbed Interferometer  

Microsoft Academic Search

Using the Palomar Testbed Interferometer (PTI), angular diameters have been measured for over 60 giant and supergiant stars, ranging in spectral type from B7 to M5. Analysis of night-to-night variations in the data reveal a consistency in the reduced results at the 1.3% level; comparison of PTI data to previous investigations with IOTA, CERGA, and lunar occultations show good agreement

G. T. van Belle

1997-01-01

71

Three-micron spectra of AGB stars and supergiants in nearby galaxies  

Microsoft Academic Search

The dependence of stellar molecular bands on the metallicity is studied using infrared L-band spectra of AGB stars (both carbon-rich and oxygen-rich) and M-type supergiants in the Large and Small Magellanic Clouds (LMC and SMC) and in the Sagittarius Dwarf Spheroidal Galaxy. The spectra cover SiO bands for oxygen-rich stars, and acetylene (C2H2), CH and HCN bands for carbon-rich AGB

M. Matsuura; A. A. Zijlstra; J. Th. van Loon; I. Yamamura; A. J. Markwick; P. A. Whitelock; P. M. Woods; J. R. Marshall; M. W. Feast; L. B. F. M. Waters

2005-01-01

72

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

NASA Astrophysics Data System (ADS)

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

Araya, Ignacio; Cure, Michel

2013-06-01

73

Systematic detection of magnetic fields in massive, late-type supergiants  

NASA Astrophysics Data System (ADS)

We report the systematic detection of magnetic fields in massive (M > 5Msolar) late-type supergiants, using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii Telescope. Our observations reveal detectable Stokes V Zeeman signatures in least-squares deconvolved mean line profiles in one-third of the observed sample of more than 30 stars. The signatures are sometimes complex, revealing multiple reversals across the line. The corresponding longitudinal magnetic field is seldom detected, although our longitudinal field error bars are typically 0.3 G (1?). These characteristics suggest topologically complex magnetic fields, presumably generated by dynamo action. The Stokes V signatures of some targets show clear time variability, indicating either rotational modulation or intrinsic evolution of the magnetic field. We also observe a weak correlation between the unsigned longitudinal magnetic field and the CaII K core emission equivalent width of the active G2Iab supergiant ? Dra and the G8Ib supergiant ? Gem. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France and the University of Hawaii. E-mail: Jason.Grunhut@rmc.ca

Grunhut, J. H.; Wade, G. A.; Hanes, D. A.; Alecian, E.

2010-11-01

74

The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought!  

NASA Astrophysics Data System (ADS)

The red supergiant (RSG) stage of massive star evolution is poorly matched by available evolutionary tracks. This is partly due to uncertainties in the derived physical properties (effective temperatures and bolometric luminosities) from observed quantities, which result in questionable placement of RSGs in the Hertzsprung-Russell diagram. The new generation of MARCS stellar atmosphere models includes a more rigorous treatment of molecular absorption, and we have used these models to make a far more robust determination of Teff and Mbol for a sample of Galactic RSGs. We obtained moderate-resolution (5Å) spectrophotometry of sixty-seven Galactic RSGs during two runs at the KPNO 2.1-m telescope and one at the CTIO 1.5-m. We reclassified the spectral types, and by comparing the depth of titanium oxide bands in the observed spectral energy distributions to those predicted by model atmospheres of various temperatures, we determined the Teff and E(B-V)'s of the observed RSGs. Here we will present our new effective temperature scale for Galactic RSGs. Our scale is warmer than those proposed in the past (Massey & Olsen 2003, Humphreys & McElroy 1983), by 60 K for the late K-type supergiants, and by 450 K for the latest M supergiants. The new scale shifts the RSGs closer to the predictions of current evolutionary theory. This work has been supported by the National Science Foundation through grant AST 00-93060 and the Research Experience for Undergraduates program at Northern Arizona University.

Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G.; White, N.

2004-12-01

75

Lithium abundance in atmospheres of F- and G-type supergiants and bright giants  

NASA Astrophysics Data System (ADS)

Lithium in the atmosphere of a F or G supergiant reflects the initial Li abundance and the internal history of the star. During evolution of a star from the main sequence (MS) to the supergiant phase, lithium may be destroyed by, for example, rotationally induced mixing in the MS stars and strongly diluted by development of the supergiant's convective envelope. In order to probe the connection between atmospheric Li abundance and evolutionary predictions, we present a non-local thermodynamic equilibrium abundance analysis of the resonance doublet Li I at 6707.8 Å for 55 Galactic F and G supergiants and bright giants (we observed 43 of them, the remaining 12 are added from Luck and Wepfer's list). The derived lithium abundances log ?(Li) may be considered in three groups, namely: (i) 10 Li-rich giants with log ?(Li) = 2.0-3.2 (all 10 are F-type or A9 stars); (ii) 13 G- to K0-type stars with Li abundances in the narrow range log ?(Li) = 1.1-1.8; (iii) all other stars provide just upper limits to the Li abundance. The derived Li abundances are compared with theoretical predictions of 2-15 M? stars (both rotating and non-rotating). Our results are generally in good agreement with theory. In particular, the absence of detectable lithium for the majority of programme stars is explainable. The comparison suggests that the stars may be separated by mass M into two groups, namely M ? 6 M? and M > 6 M?. All Li-rich giants and supergiants with log ?(Li) ? 2.0 have masses M < 6 M?; this conclusion follows not only from our work but also from a scrutiny of published data. 11 of 13 stars with log ?(Li) = 1.1-1.8, specifically the stars with M < 6 M?, show good agreement with the post-first dredge-up surface abundance log ?(Li) ? 1.4 predicted for the non-rotating 2-6 M? stellar models. An absence of Li-rich stars in the range M > 6 M? agrees with the theoretical prediction that F and G supergiants and giants with M > 6 M? cannot show detectable lithium. We note that present theory appears unable to account for the derived Li abundances for some stars, namely for (i) a few relatively low-mass Li-rich giants (M < 6 M?), whose high Li abundances accompanied by rather high rotational velocities or substantial nitrogen excess contradict theoretical predictions; (ii) the relatively high-mass supergiants HR 461 and HR 8313 (M > 6 M?) with the detected abundances log ? = 1.3-1.5. It is possible that the lithium in such stars was synthesized recently.

Lyubimkov, Leonid S.; Lambert, David L.; Kaminsky, Bogdan M.; Pavlenko, Yakov V.; Poklad, Dmitry B.; Rachkovskaya, Tamara M.

2012-11-01

76

Spectroscopic study of the outflowing disk winds of B[e] supergiants in the Magellanic Clouds.  

NASA Astrophysics Data System (ADS)

We report on UV high resolution spectroscopic observations of R50 in the Small Magellanic Cloud, and R82 and HenS22 in the Large Magellanic Cloud obtained with the International Ultraviolet Explorer. The observed stars are supposed to represent edge-on cases of B[e] supergiants for which a two-component stellar wind model has previously been suggested. The spectra are characterized by P Cygni-type lines of FeII. The observations show that the three stars have very slowly expanding winds with terminal velocities derived from the blue absorption edges of 75, 100, and 120km/s, respectively. Fits of the FeII lines of Hen S22 and R82 using the SEI method lead to even slower velocities of about 60 to 80km/s, respectively. This is about a factor of ten slower than the terminal velocity of normal B-type supergiants. The results are consistent with the assumption that the observed stars are viewed edge-on. We derived optical depths of the absorption components of the FeII resonance lines of Hen S22 and R82 of larger than about 5, yielding lower limits for the disk mass-loss rates of the order of 6x10^-7^ and 5x10^-7^Msun_/yr, respectively. The very low terminal velocity of the disk can be explained by the fact that the disks of the B[e] supergiants are on the low-velocity side of the bi-stability jump of radiation driven winds (which reduces vinfinity_/v_esc_) and a rotational velocity of about 0.75 of the critical rotation velocity (which reduces the effective v_esc_). The effective gravity derived from vinfinity_ and vinfinity_/v_esc_=1.3 is very low. It is on the order of logg_eff_=0.2 to 0.7.

Zickgraf, F.-J.; Humphreys, R. M.; Lamers, H. J. G. L. M.; Smolinski, J.; Wolf, B.; Stahl, O.

1996-11-01

77

Interferometric observations of the supergiant stars ? Orionis and ? Herculis with FLUOR at IOTA  

NASA Astrophysics Data System (ADS)

We report the observations in the K band of the red supergiant star ? Orionis and of the bright giant star ? Herculis with the FLUOR beamcombiner at the IOTA interferometer. The high quality of the data allows us to estimate limb-darkening and derive precise diameters in the K band which combined with bolometric fluxes yield effective temperatures. In the case of Betelgeuse, data collected at high spatial frequency although sparse are compatible with circular symmetry and there is no clear evidence for departure from circular symmetry. We have combined the K band data with interferometric measurements in the L band and at 11.15 ?m. The full set of data can be explained if a 2055 K layer with optical depths ?K=0.060±0.003, ?L=0.026±0.002 and ?11.15 ?m= 2.33±0.23 is added 0.33 R* above the photosphere providing a first consistent view of the star in this range of wavelengths. This layer provides a consistent explanation for at least three otherwise puzzling observations: the wavelength variation of apparent diameter, the dramatic difference in limb darkening between the two supergiant stars, and the previously noted reduced effective temperature of supergiants with respect to giants of the same spectral type. Each of these may be simply understood as an artifact due to not accounting for the presence of the upper layer in the data analysis. This consistent picture can be considered strong support for the presence of a sphere of warm water vapor, proposed by \\cite{tsuji2000} when interpreting the spectra of strong molecular lines. Based on observations collected at the IOTA interferometer, Whipple Observatory, Mount Hopkins, Arizona.

Perrin, G.; Ridgway, S. T.; Coudé du Foresto, V.; Mennesson, B.; Traub, W. A.; Lacasse, M. G.

2004-05-01

78

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

79

Supergiant, fast, but not so transient 4U 1907+09  

NASA Astrophysics Data System (ADS)

We have investigated the dipping activity observed in the high-mass X-ray binary 4U 1907+09 and shown that the source continues to pulsate in the "off" state, noting that the transition between the "on" and "off" states may be either dip-like or flare-like. This behavior may be explained in the framework of the "gated accretion" scenario proposed to explain the flares in supergiant fast X-ray transients (SFXTs). We conclude that 4U 1907 + 09 might prove to be a missing link between the SFXTs and ordinary accreting pulsars.

Doroshenko, V.; Santangelo, A.; Ducci, L.; Klochkov, D.

2012-12-01

80

Spherical opacity sampling model atmospheres for M-giants and supergiants. II - A grid  

NASA Astrophysics Data System (ADS)

A grid is presented of spherically symmetric model atmospheres for M-type giants and supergiants, covering the range T(eff) between 3000 and 4000 K, log g between -0.5 and 1.5 for 1, 2, and 5 solar masses, with some additional cooler models. The model atmospheres were computed using the program, methods, and data described by Plez et al. (1992). New line-lists, calculated from up-to-date data for the TiO, VO, and H2O molecules, are included in the opacities.

Plez, B.

1992-09-01

81

LMC O Supergiant Mass Loss Rates Determined from P V, S V and IR Excesses  

NASA Astrophysics Data System (ADS)

We use HST/STIS and FUSE spectra and Spitzer/IRAC photometry to obtain independent mass loss rates for 7 LMC O supergiants. The mass loss rates are derived from the P Cygni profiles of the P V 1118, 1128 resonance doublet, the S V 1502 and N IV 1718 excited state lines, and the IR excesses of a combination of ground based and Spitzer photometry. The different mass loss rates are compared to each other and to theoretical expectations. We discuss the causes for the differences between the various determinations.

Massa, Derck; Prinja, R.; Fullerton, A.; Lennon, D.

2012-05-01

82

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

NASA Astrophysics Data System (ADS)

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.

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

83

INTEGRAL detection of an outbursts of two supergiant fast X-ray transients  

NASA Astrophysics Data System (ADS)

During the observation of parts of the inner Galactic spiral arms performed on 2013-09-18, the INTEGRAL observatory detected the outbursts from the sources IGR J16418-4532 (see also ATEL #5398 for the Swift detection of an outburst on 2013-09-17 ) and IGR J18483-0311. The former is a supergiant fast X-ray transient (SFXT) with intermediate properties (Sidoli et al., MNRAS., 420, 554-561, 2012; Romano et al., MNRAS, 419, 2695-2702, 2012), the latter a confirmed member of this class (e.g., Romano et al., MNRAS, 401, 1564-1569, 2010).

Tuerler, M.; Ferrigno, C.; Bodaghee, A.; Romano, P.

2013-09-01

84

STRÖMGREN Photometry of the Supergiants HD 4841 (B5 Ia) and HD 194279 (B2 Ia)  

NASA Astrophysics Data System (ADS)

We investigated the variability of the B Ia supergiants HD 4841 and HD 194279 using Strömgren photometry obtained with the Four College Automated Photoelectric Telescope, Arizona and the 0.4-m telescope of TÜB?TAK National Observatory (TUG), Turkey. Both stars are definitely variable with amplitudes of order 0.10 mag in u, v, b and y. The Turkish photometry with several observations per night suggests a more rapid variability than the once per night American photometry. The periods of variability are likely to be of the order of one day.

Adelman, Saul J.; Yüce, Kutluay

85

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

NASA Astrophysics Data System (ADS)

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 ?-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, and in extreme cases, + 6000 K and ± 0.4 dex, respectively. A parameter calibration for sub-spectral types is also proposed. Moreover, we present a new bolometric correction relation to temperature based on our empirical data, rather than on synthetic grids. Conclusions: The photometric calibrations presented here are useful tools to estimate effective temperatures and surface gravities of non-supergiant OB stars in a fast manner. This is also applicable to some single-line spectroscopic binaries, but caution has to be taken for undetected double-lined spectroscopic binaries and single objects with anomalous reddening-law, dubious photometric quantities and/or luminosity classes, for which the systematic uncertainties may increase significantly. We recommend to use these calibrations only as a first step of the parameter estimation, with subsequent refinements based on spectroscopy. A larger sample covering more uniformly the parameter space under consideration will allow refinements to the present calibrations. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max- Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), proposals H2001-2.2-011 and H2005-2.2-016.Based on observations collected at the European Southern Observatory, Chile, ESO 074.B-0455(A) and from the ESO Archive.Based on spectral data retrieved from the ELODIE archive at Observatoire de Haute-Provence (OHP).Appendices A and B are available in electronic form at http://www.aanda.org

Nieva, M.-F.

2013-02-01

86

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

SciTech Connect

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.

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

2012-05-20

87

Two ring nebulae around blue supergiants in the Large Magellanic Cloud.  

NASA Astrophysics Data System (ADS)

Ring nebulae are often found around massive stars such as Wolf-Rayet stars, OB and Of stars and Luminous Blue Variables (LBVs). In this paper we report on two ring nebulae around blue supergiants in the Large Magellanic Cloud. The star Sk-69 279 is classified as O9f and is surrounded by a closed shell with a diameter of 4.5pc. Our echelle observations show an expansion velocity of 14km/s and a high [NII]?6583Å/H? ratio. This line ratio suggests nitrogen abundance enhancement consistent with those seen in ejectas from LBVs. Thus the ring nebula around Sk-69 279 is a circumstellar bubble. The star Sk-69 271, a B2 supergiant, is surrounded by an H? arc resembling an half shell. Echelle observations show a large expanding shell with the arc being part of the approaching surface. The expansion velocity is ~24km/s and the [NII]?6583Å/H? is not much higher than that of the background emission. The lack of nitrogen abundance anomaly suggests that the expanding shell is an interstellar bubble with a dynamic age of 2x10^5^yr.

Weis, K.; Chu, Y.-H.; Duschl, W. J.; Bomans, D. J.

1997-09-01

88

A Search for Galactic Red Supergiant Variables Beyond the Solar Circle  

NASA Astrophysics Data System (ADS)

The Galactic rotation curve outside of the Solar circle is particularly difficult to ascertain, yet of critical importance for characterizing the distribution of mass in the Galaxy. We propose to identify a new and large sample of stellar kinematic tracers beyond the Solar circle, in the form of red supergiant variables (RSVs; spectral type M0-M5, luminosity class Ia-Ib). RSVs are ideal tracers of the heavily extincted outer Galactic disk, because (1) they are the intrinsically most luminous Pop I standard candles in the near-infrared, (2) they are more common than the classically employed Cepheids, and (3) they exhibit a period-luminosity relation of comparable precision to that of Cepheids. With the CTIO 0.9m in queue mode, we will derive the pulsation periods of our RSV candidates, allowing us to identify the most distant RSVs for further study. In addition, follow- up observations to obtain accurate, phase-weighted (``(gamma)'') radial velocities (a prerequisite for determining the Galactic rotation curve with RSVs) cannot be planned without period information. We have preselected RSV candidates from a catalog of ~1500 red supergiants in the Galactic plane, originally identified on objective-prism plates. Spectral types and luminosity classes have been determined from 8-color Wing photometry and medium-resolution spectra. The pulsation periods are expected to be 100 to 1000 days, and thus we request long-term status.

Alves, David; MacConnell, Jack; Wing, Robert; Bond, Howard E.; Zurek, David; Hoard, Donald W.

2000-02-01

89

The Dusty Red Supergiant Progenitor of Supernova 2012aw in M95  

NASA Astrophysics Data System (ADS)

We directly detected the red supergiant progenitor of the intermediate-luminosity Type II-Plateau Supernova 2012aw in Messier 95 (NGC 3351). The star was identified in Hubble Space Telescope images of the host galaxy obtained 17 to 18 years before the explosion, as well as in ground-based, near-infrared images obtained 6 to 12 years prior to the SN. We find evidence for substantial circumstellar dust around the luminous star. We find that the effective total-to-selective ratio of extinction is significantly different than that of diffuse interstellar dust, which is also found for luminous Galactic red supergiants. The star's spectral energy distribution is consistent with an effective temperature of 3600 K and a bolometric magnitude of about -8.3. Comparing these values with recent theoretical massive-star evolutionary tracks, we infer that the star had an initial mass of about 17 to 18 solar masses. The circumstellar dust was destroyed by the SN explosion.

Van Dyk, Schuyler D.; Cenko, S. B.; Poznanski, D.; Arcavi, I.; Gal-Yam, A.; Filippenko, A. V.; et al.

2013-01-01

90

SLOW RADIATION-DRIVEN WIND SOLUTIONS OF A-TYPE SUPERGIANTS  

SciTech Connect

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

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

2011-08-10

91

Supersized: A Spitzer Survey of Dusty Disks around B[e] Supergiants in the Magellanic Clouds  

NASA Astrophysics Data System (ADS)

The enigmatic class of B[e] super/hypergiants include among the most luminous individual stars known. These stars are of great interest and importance to the study of massive stars and their environments. Via Cycle 1 Spitzer IRS observations, we discovered that two Large Magellanic Cloud (LMC) B[e] hypergiants, R 126 and R 66, display similar, flat IR spectral enegy distributions indicative of the presence of massive, dusty circumstellar disks; R 66 displays, in addition, spectral evidence for crystalline grains and PAHs. This Spitzer/IRS discovery of ``fraternal twin'' disks around R 126 and R 66 has provided new insight into the origin and composition of dusty disks around the most massive stars. We now propose to build on these results via a comprehensive Spitzer IRS and photometric survey of thermal dust emission from a complete sample of all B[e] supergiants and hypergiants in the Magellanic Clouds. The IRS spectra and IRAC/MIPS photometry data will establish the fraction of B[e] supergiants that are encircled by dusty disks and, through modeling, will yield the range of masses, radii, and scale heights that characterize B[e] star dust disks. These results will provide crucial constraints on models of the origin of disks around massive stars , as well as on mechanisms for the production of crystalline silicate grains and for the shaping of supernova remnants.

Kastner, Joel; Buchanan, Catherine; Forrest, Bill; Sahai, Raghvendra; Sargent, Ben

2006-05-01

92

Double Bow Shocks around Young, Runaway Red Supergiants: Application to Betelgeuse  

NASA Astrophysics Data System (ADS)

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.

Mackey, Jonathan; Mohamed, Shazrene; Neilson, Hilding R.; Langer, Norbert; Meyer, Dominique M.-A.

2012-05-01

93

Evolution of Massive Stars with Pulsation-driven Superwinds During the Red Supergiant Phase  

NASA Astrophysics Data System (ADS)

Pulsations driven by partial ionization of hydrogen in the envelope are often considered important for driving winds from red supergiants (RSGs). In particular, it has been suggested by some authors that the pulsation growth rate in an RSG can be high enough to trigger an unusually strong wind (or a superwind), when the luminosity-to-mass ratio becomes sufficiently large. Using both hydrostatic and hydrodynamic stellar evolution models with initial masses ranging from 15 to 40 M sun, we investigate (1) how the pulsation growth rate depends on the global parameters of supergiant stars and (2) what would be the consequences of a pulsation-driven superwind, if it occurred, for the late stages of massive star evolution. We suggest that such a superwind history would be marked by a runaway increase, followed by a sudden decrease, of the wind's mass-loss rate. The impact on the late evolution of massive stars would be substantial, with stars losing a huge fraction of their H-envelope even with a significantly lower initial mass than previously predicted. This might explain the observed lack of Type II-P supernova (SN) progenitors having initial mass higher than about 17 M sun. We also discuss possible implications for a subset of Type IIn SNe.

Yoon, Sung-Chul; Cantiello, Matteo

2010-07-01

94

Radial velocities for different spectral lines of B and A supergiants in our Galaxy and in the Large Magellanic Cloud  

Microsoft Academic Search

Coudé spectra of 23 early-type supergiants (16 of them belong to our Galaxy and 7 to the Large Magellanic Cloud (LMC)) were measured to study the radial velocities of all metallic and non-metallic lines in relation to their EP + IP (high excitation + ionization potential). The identified elements of the spectra do not show any systematic dependence (gradient) of

E. Kontizas; M. Kontizas

1981-01-01

95

AGB stars and red supergiants in the LMC as seen with DENIS  

NASA Astrophysics Data System (ADS)

The goal of this short communication is to evaluate the usefulness of Deep Near-Infrared Survey (DENIS) for the study of stars on the Asymptotic Giant Branch (AGB) and red supergiants (RSG) in the Large Magellanic Cloud (LMC). We try to answer two fundamental questions: (i) Can DENIS detect all the AGB stars and RSG in the LMC? (ii) How can we identify these sources using only the I, J, and K bands? We have used an observational approach by compiling available data in the LMC in the (V,R), I, J, H, K, (L,M) bands. About 3000 AGB stars and RSG have been measured in I, of which about 1000 have JHK measurements. Note that most of the searches were based on I and then the sample is strongly biased for optical stars, losing mass at a small rate. Only a few dust obscured objects are known, identified on the basis of Infrared Astronomy Satellite (IRAS) observations.

Loup, C.; Groenewegen, M. A. T.

1994-07-01

96

The ionized nebula surrounding the red supergiant W26 in Westerlund 1  

NASA Astrophysics Data System (ADS)

We present H? images of an ionized nebula surrounding the M2-5Ia red supergiant (RSG) W26 in the massive star cluster Westerlund 1. The nebula consists of a circumstellar shell or ring ˜0.1 pc in diameter and a triangular nebula ˜0.2 pc from the star that in high-resolution Hubble Space Telescope images shows a complex filamentary structure. The excitation mechanism of both regions is unclear since RSGs are too cool to produce ionizing photons and we consider various possibilities. The presence of the nebula, high stellar luminosity and spectral variability suggests that W26 is a highly evolved RSG experiencing extreme levels of mass-loss. As the only known example of an ionized nebula surrounding an RSG W26 deserves further attention to improve our understanding of the final evolutionary stages of massive stars.

Wright, Nicholas J.; Wesson, Roger; Drew, Janet E.; Barentsen, Geert; Barlow, Michael J.; Walsh, Jeremy R.; Zijlstra, Albert; Drake, Jeremy J.; Eislöffel, Jochen; Farnhill, Hywel J.

2013-10-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

98

The Swift Supergiant Fast X-ray Transients Project: A review, new results and future perspectives  

NASA Astrophysics Data System (ADS)

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.

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.

2013-11-01

99

LSII + 34 deg 26, an unusual B supergiant located near the outer edge of the galaxy  

SciTech Connect

Turner (1983) has found that the object considered in the present investigation is an 11th-magnitude emission-line B supergiant lying at the extremely large distance of approximately 18 kpc, somewhat below the galactic plane in a little-reddened portion of Cygnus. The star can be categorized as a member of the rare class of Population I objects found at large distances from the sun and lying more than 1 kpc away from the principal plane of the Galaxy. A summary is provided both of existing and new observational data which have been obtained for the star, giving attention to its unusual characteristics. The location of the object makes it suitable for use in an examination of the galactic rotation law at large distances from the galactic center. 20 references.

Turner, D.G.; Drilling, J.S.

1984-04-01

100

Resolving the dusty torus and the mystery surrounding LMC red supergiant WOH G64  

NASA Astrophysics Data System (ADS)

We present mid-IR long-baseline interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud with MIDI at the ESO's Very Large Telescope Interferometer (VLTI). Our MIDI observations of WOH G64 are the first VLTI observations to spatially resolve an individual stellar source in an extragalactic system. Our 2-D radiative transfer modeling reveals the presence of a geometrically and optically thick torus seen nearly pole-on. This model brings WOH G64 in much better agreement with the current evolutionary tracks for a 25 M? star — about a half of the previous estimate of 40 M? — and solves the serious discrepancy between theory and observation which existed for this object.

Ohnaka, Keiichi; Driebe, Thomas; Hofmann, Karl-Heinz; Weigelt, Gerd; Wittkowski, Markus

2009-03-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

102

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

SciTech Connect

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).

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

2012-09-10

103

A study of the brightness variations in the red supergiant BC Cygni  

NASA Astrophysics Data System (ADS)

The variability of the type C semi-regular (SRC) M3.5 Ia supergiant variable BC Cyg is examined with reference to measurements of its photographic B magnitude derived from 866 archival plates in the Harvard and Sternberg collections as well as eye estimates of its visual V magnitude made by members of the AAVSO. BC Cyg is the brightest member of the young open cluster Berkeley 87, so it has a well established reddening, distance, and age. A discrete Fourier analysis was performed on the BC Cygni light curve, as well as on individual subsets of the data. The analysis was made to study the fundamental periods of variability in this red supergiant variable. BC Cyg exhibits interesting features in its century-long baseline of brightness variations that relate to fundamental mode envelope pulsation as well as evolution: an 0 m .5 increase in [left angle bracket] B [right angle bracket] over the past century in conjunction with a steady decrease in pulsation period from ~697 d in 1900 to 688 d in 2000. Despite the increase in [left angle bracket] B [right angle bracket], the star's luminosity appears to have decreased over the past century, presumably as a result of stellar evolutionary effects. A detailed examination of a well sampled portion of the star's light curve, data spanning the interval HJD 2442000 to 2449000, by means of non-linear least squares analysis indicates that only one periodicity (686 days) exists in the observations. No secondary peridicity can be detected, to within the constraints of observational uncertainty.

Rohanizadegan, Mina

104

SN 2004A: another Type II-P supernova with a red supergiant progenitor  

NASA Astrophysics Data System (ADS)

We present a monitoring study of SN 2004A and probable discovery of a progenitor star in pre-explosion Hubble Space Telescope (HST) images. The photometric and spectroscopic monitoring of SN 2004A show that it was a normal Type II-P which was discovered in NGC 6207 about two weeks after explosion. We compare SN 2004A to the similar Type II-P SN 1999em and estimate an explosion epoch of 2004 January 6. We also calculate three new distances to NGC 6207 of 21.0 +/- 4.3,21.4 +/- 3.5 and 25.1 +/- 1.7Mpc. The former was calculated using the Standard Candle Method (SCM) for SNeII-P, and the latter two from the brightest supergiants method (BSM). We combine these three distances with existing kinematic distances, to derive a mean value of 20.3 +/- 3.4Mpc. Using this distance, we estimate that the ejected nickel mass in the explosion is 0.046+0.031-0.017Msolar. The progenitor of SN 2004A is identified in pre-explosion WFPC2 F814W images with a magnitude of mF814W = 24.3 +/- 0.3, but is below the detection limit of the F606W images. We show that this was likely a red supergiant (RSG) with a mass of 9+3-2Msolar. The object is detected at 4.7? above the background noise. Even if this detection is spurious, the 5? upper limit would give a robust upper mass limit of 12Msolar for a RSG progenitor. These initial masses are very similar to those of two previously identified RSG progenitors of the Type II-P SNe 2004gd (8+4-2Msolar) and 2005cs (9+3-2Msolar).

Hendry, M. A.; Smartt, S. J.; Crockett, R. M.; Maund, J. R.; Gal-Yam, A.; Moon, D.-S.; Cenko, S. B.; Fox, D. W.; Kudritzki, R. P.; Benn, C. R.; Østensen, R.

2006-07-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

106

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

Microsoft Academic Search

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

A. Maggio; G. S. Vaiana; B. M. Haisch; R. A. Stern; J. Bookbinder; F. R. Harnden Jr.; R. Rosner

1990-01-01

107

And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae  

NASA Astrophysics Data System (ADS)

We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula, and we discuss their significance in stellar evolution. The brighter of the two new objects, SBW 1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Although seen in Carina, its luminosity class and radial velocity imply a larger distance of ~7 kpc in the far Carina arm. At that distance its size and shape are nearly identical to the equatorial ring around SN 1987A, but SBW 1's low N abundance indicates that the ring was excreted without its star passing through a red supergiant phase. The fainter object, SBW 2, is a more distorted ring, is N-rich, and is peculiar in that its central star seems to be invisible. We discuss the implications of these two new nebulae in context with other circumstellar rings such as those around SN 1987A, Sher 25, HD 168625, RY Scuti, WeBo 1, SuWt 2, and others. The ring bearers fall into two groups: Five rings surround hot supergiants, and it is striking that all except for the one known binary are carbon copies of the ring around SN 1987A. We propose a link between these B supergiant rings and B[e] supergiants, where the large spatially resolved rings derive from the same material that would have given rise to emission lines during the earlier B[e] phase, when it was much closer to the star. The remaining four rings surround evolved intermediate-mass stars; all members of this ring fellowship are close binaries, hinting that binary interactions govern the forging of such rings. Two-thirds of our sample are found in or near giant H II regions. We estimate that there may be several thousand more dark rings in the Galaxy, but we are scarcely aware of their existence-either because they are only illuminated in precious few circumstances or because of selection effects. For intermediate-mass stars, these rings might be the preexisting equatorial density enhancements invoked to bind the waists of bipolar nebulae. Based in part on observations made at the Clay Telescope of the Magellan Observatory, a joint facility of the Carnegie Observatories, Harvard University, the Massachusetts Institute of Technology, the University of Arizona, and the University of Michigan.

Smith, Nathan; Bally, John; Walawender, Josh

2007-08-01

108

Period-luminosity relations for red supergiant variables - II. The distance to M101  

NASA Astrophysics Data System (ADS)

We report the discovery of 42 red supergiant variables (RSVs) in the late-type spiral galaxy M101. Periods for the luminosity variation of these RSVs were determined from 20 epochs of ground-based CCD photometry in the Kron-Cousins R band obtained with the KPNO 2.1-m and WIYN 3.5-m telescopes over a span of three years. The periods found were in the range 200-1300days. Using the relationship between the RSV periods and their luminosity in the Kron-Cousins I band, we estimate a reddening-corrected distance modulus to M101 of 29.40+/-0.16mag (based on a distance modulus of 18.5+/-0.1mag for the Large Magellanic Cloud). This distance is consistent with the Hubble Space Telescope Key Project Cepheid distances of 29.34+/-0.17mag for the outer field of M101 and 29.21+/-0.17mag for the inner field.

Jurcevic, J. S.; Pierce, M. J.; Jacoby, G. H.

2000-04-01

109

Type IIP supernova 2008in: the explosion of a normal red supergiant  

NASA Astrophysics Data System (ADS)

Context. The explosion energy and the ejecta mass of a type IIP supernova make up the basis for the theory of explosion mechanism. So far, these parameters have only been determined for seven events. Aims: Type IIP supernova 2008in is another well-observed event for which a detailed hydrodynamic modeling can be used to derive the supernova parameters. Methods: Hydrodynamic modeling was employed to describe the bolometric light curve and the expansion velocities at the photosphere level. A time-dependent model for hydrogen ionization and excitation was applied to model the H? and H? line profiles. Results: We found an ejecta mass of 13.6 ± 1.9 M?, an explosion energy of (5.05 ± 3.4) × 1050 erg, a presupernova radius of 570 ± 100 R?, and a radioactive 56Ni mass of 0.015 ± 0.005 M?. The estimated progenitor mass is 15.5 ± 2.2 M?. We uncovered a problem of the H? and H? description at the early phase, which cannot be resolved within a spherically symmetric model. Conclusions: The presupernova of SN 2008in was a normal red supergiant with the minimum mass of the progenitor among eight type IIP supernovae explored by means of the hydrodynamic modeling. The problem of the absence of type IIP supernovae with the progenitor masses <15 M? in this sample remains open.

Utrobin, V. P.; Chugai, N. N.

2013-07-01

110

The Period-Luminosity Relation of Red Supergiant Stars in the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

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

Yang, Ming; Jiang, B. W.

2012-07-01

111

Interferometric Measurements Of The A-type Supergiant Deneb With The CHARA Array  

NASA Astrophysics Data System (ADS)

We have obtained precise interferometric measurements of the A-type supergiant Deneb (A2Ia) at the Center for High Angular Resolution Astronomy (CHARA) Array in the infrared K' band (1.94 to 2.34 microns) using the Fiber Linked Unit for Optical Recombination (FLUOR). Our observations were obtained over 20 nights in 2004 and 2005 with five telescope pairs E2-W2, W2-S2, W1-E2, E1-W1, and S1-W2. The projected baselines span 106 to 312 meters and sample the first and second lobes of Deneb's visibility curve. Our preliminary analysis reveals that the amplitude of the second lobe of the visibility curve is weaker than that predicted by a spherical hydrostatic model atmosphere.We also find that Deneb's angular diameter varies with position angle at the level of a few percent. We will present these data and discuss our analysis using a unified expanding model atmosphere and a rotationally distorted model atmosphere.This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology. The CHARA Array is operated by the Center for High Angular Resolution Astronomy, Georgia State University, Atlanta, GA. Additional support comes from the National Science Foundation, the Keck Foundation and the Packard Foundation.

Aufdenberg, Jason P.; Mérand, A.; Ridgway, S. T.; Coudé du Foresto, V.; Kervella, P.; Berger, D.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.; Turner, N. H.; McAlister, H. A.

2006-06-01

112

An Interferometric 270--355 GHz Spectral Line Survey of the Red Supergiant VY CMa  

NASA Astrophysics Data System (ADS)

We have used the Submillimeter Array to image the molecular line emission in the circumstellar envelope of the peculiar red supergiant star VY Canis Majoris over the whole 870 ?m atmospheric window. Employing adaptive calibration using the object's continuum emission we achieve high quality one arcsecond resolution imaging of the whole 280--355 GHz range within which we find 211 distinct spectral lines from 33 molecules (including isotopologues) plus 40 unidentified lines. From the distribution of molecules we are obtaining their abundances and isotopologic abundance ratios. Using data for multiple transitions in a number of molecules we are deriving the physical conditions in the circumstellar envelope to reach a picture of the star's chemistry that can be compared with models. Our legacy survey is accompanied by a strong laboratory effort that helps with the identification of possibly newly found molecules traced by unidentified lines. We shall create a publicly accessible database of spectral-line channel-maps of the emission from all the lines detected in the survey.

Menten, K. M.; Young, K. H.; Patel, N. A.; Gottlieb, C. A.; Thaddeus, P.; McCarthy, M. C.; Gurwell, M. A.; Belloche, A.; Kaminski, T.; Verheyen, L.; Decin, L.; Brunken, S.; Holger, S. P. M.

2011-05-01

113

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

NASA Astrophysics Data System (ADS)

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.

Levesque, Emily M.; Massey, Philip

2012-07-01

114

Neutron star masses from hydrodynamical effects in obscured supergiant high mass X-ray binaries  

NASA Astrophysics Data System (ADS)

Context. A population of obscured supergiant high mass X-ray binaries has been discovered by INTEGRAL. X-ray wind tomography of IGR J17252-3616 inferred a slow wind velocity to account for the enhanced obscuration. Aims: The main goal of this study is to understand under which conditions high obscuration could occur. Methods: We have used an hydrodynamical code to simulate the flow of the stellar wind around the neutron star. A grid of simulations was used to study the dependency of the absorbing column density and of the X-ray light-curves on the model parameters. A comparison between the simulation results and the observations of IGR J17252-3616 provides an estimate on these parameters. Results: We have constrained the wind terminal velocity to 500-600 km s-1 and the neutron star mass to 1.75-2.15 M?. Conclusions: We have confirmed that the initial hypothesis of a slow wind velocity with a moderate mass loss rate is valid. The mass of the neutron star can be constrained by studying its impact on the accretion flow.

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

2012-11-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

116

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

SciTech Connect

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.

Levesque, Emily M. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Massey, Philip, E-mail: Emily.Levesque@colorado.edu [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)

2012-07-15

117

Herschel/HIFI observations of red supergiants and yellow hypergiants. I. Molecular inventory  

NASA Astrophysics Data System (ADS)

Context. Red supergiant stars (RSGs) and yellow hypergiant stars (YHGs) are believed to be the high-mass counterparts of stars in the asymptotic giant branch (AGB) and early post-AGB phases. As such, they are scarcer and the properties and evolution of their envelopes are still poorly understood. Aims: We study the mass-loss in the post main-sequence evolution of massive stars, through the properties of their envelopes in the intermediate and warm gas layers. These are the regions where the acceleration of the gas takes place and the most recent mass-loss episodes can be seen. Methods: We used the HIFI instrument on-board the Herschel Space Observatory to observe sub-millimetre and far-infrared (FIR) transitions of CO, water, and their isotopologues in a sample of two RSGs (NML Cyg and Betelgeuse) and two YHGs (IRC+10420 and AFGL 2343) stars. We present an inventory of the detected lines and analyse the information revealed by their spectral profiles. A comparison of the line intensity and shape in various transitions is used to qualitatively derive a picture of the envelope physical structure. On the basis of the results presented in an earlier study, we model the CO and 13CO emission in IRC+10420 and compare it to a set of lines ranging from the millimetre to the FIR. Results: Red supergiants have stronger high-excitation lines than the YHGs, indicating that they harbour dense and hot inner shells contributing to these transitions. Consequently, these high-J lines in RSGs originate from acceleration layers that have not yet reached the circumstellar terminal velocity and have narrower profiles than their flat-topped lower-J counterparts. The YHGs tend to lack this inner component, in line with the picture of detached, hollow envelopes derived from studies at longer wavelengths. NH3 is only detected in two sources (NML Cyg and IRC+10420), which are also observed to be the strongest water-line emitters of the studied sample. In contrast, OH is detected in all sources and does not seem to correlate with the water line intensities. We show that the IRC+10420 model derived solely from millimetre low-J CO transitions is capable of reproducing the high-J transitions when the temperature in the inner shell is simply lowered by about 30%. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A is available in electronic form at http://www.aanda.orgFITS files of the spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A99

Teyssier, D.; Quintana-Lacaci, G.; Marston, A. P.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Decin, L.; Dominik, C.; Justtanont, K.; de Koter, A.; Melnick, G.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Soria-Ruiz, R.; Schöier, F. L.; Szczerba, R.; Waters, L. B. F. M.

2012-09-01

118

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

SciTech Connect

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.

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

2010-12-10

119

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

NASA Astrophysics Data System (ADS)

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

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

120

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

SciTech Connect

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.

Lopatin, N. (VNIIgeosystem, Moscow (Russian Federation))

1996-01-01

121

Swift observations of two supergiant fast X-ray transient prototypes in outburst  

NASA Astrophysics Data System (ADS)

We report on the results from observations of the most recent outbursts of XTE J1739-302 and IGR J17544-2619, which are considered to be the prototypes of the supergiant fast X-ray transient class. They triggered the Swift/Burst Alert Telescope on 2011 February 22 and March 24, respectively, and each time a prompt Swift slew allowed us to obtain the rich broad-band data we present. The X-ray Telescope light curves show the descending portion of very bright flares that reached luminosities of ˜2 × 1036 and ˜5 × 1036 erg s-1. The broad-band spectra, when fitted with the usual phenomenological models adopted for accreting neutron stars, yield values of both high-energy cut-off and e-folding energy consistent with those obtained from previously reported outbursts from these sources. In the context of more physical models, the spectra of both sources can be well fitted either with a two-blackbody model or with a single unsaturated Comptonization model. In the latter case, the model can be either a classical static Comptonization model, such as COMPTT, or the recently developed COMPMAG model, which includes thermal and bulk Comptonization for cylindrical accretion on to a magnetized neutron star. We discuss the possible accretion scenarios derived by the different models, and we also emphasize the fact that the electron density derived from the Comptonization models, in the regions where the X-ray spectrum presumably forms, is lower than that estimated using the continuity equation at the magnetospheric radius and the source X-ray luminosity, and we give some possible explanations.

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

2012-08-01

122

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

SciTech Connect

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.

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

2010-12-10

123

The First Direct Measurement of an Early B Supergiant X-ray Source Electron Density  

NASA Astrophysics Data System (ADS)

The ratio of the He-like ion forbidden to intercombination emission lines (f/i) provides a diagnostic for determining either the electron density of an X-ray source (collisional-dominated), or the X-ray source spatial location relative to a central EUV/UV radiation source (radiation-dominated). With the advent of high energy resolution spectroscopy, this diagnostic has become a well proven technique for determining the radial distribution of X-ray sources in OB stellar winds. However, in high energy ions (e.g., Si XIII) where the strength of this ratio is controlled by the radiation shortward of the Lyman edge, we show that there is an expected transition from radiation-dominance to collisional-dominance in the early B star spectral range. Because the photospheric flux is weak in the spectral energy region controlling the Si XIII f/i line ratio, we can probe stellar wind distributed X-ray source models from a different perspective and address fundamental issues pertaining to the origin of OB stellar X-ray emission. To verify this behavior we obtained four Chandra HETGS observations of the early B supergiant ? Ori (B0.5Ia) over a time span of approximately 10 days (total exposure = 234 ks). These observations allow us to explore the expected transition to collisional dominance. But, more importantly, our analysis of the Si XIII f/i line ratio has revealed the first direct measurement of an X-ray source density ( 1013 cm-3). We discuss the implications of these results.

Waldron, Wayne L.; Cassinelli, J. P.; Miller, N. A.; Schlegel, E. M.

2012-01-01

124

Red Supergiant Stars in the Large Magellanic Cloud. I. The Period-Luminosity Relation  

NASA Astrophysics Data System (ADS)

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 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 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.

Yang, Ming; Jiang, B. W.

2011-01-01

125

THE PHYSICAL PROPERTIES OF THE RED SUPERGIANT WOH G64: THE LARGEST STAR KNOWN?  

SciTech Connect

WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic Cloud (LMC), with a number of properties that set it apart from the rest of the LMC RSG population, including a thick circumstellar dust torus, an unusually late spectral type, maser activity, and nebular emission lines. Its reported physical properties are also extreme, including the largest radius for any star known and an effective temperature that is much cooler than other RSGs in the LMC, both of which are at variance with stellar evolutionary theory. We fit moderate-resolution optical spectrophotometry of WOH G64 with the MARCS stellar atmosphere models, determining an effective temperature of 3400 {+-} 25 K. We obtain a similar result from the star's broadband V - K colors. With this effective temperature, and taking into account the flux contribution from the asymmetric circumstellar dust envelope, we calculate log(L/L {sub sun}) = 5.45 {+-} 0.05 for WOH G64, quite similar to the luminosity reported by Ohnaka and collaborators based on their radiative transfer modeling of the star's dust torus. We determine a radius of R/R {sub sun} = 1540, bringing the size of WOH G64 and its position on the Hertzsprung-Russell diagram into agreement with the largest known Galactic RSGs, although it is still extreme for the LMC. In addition, we use the Ca II triplet absorption feature to determine a radial velocity of 294 {+-} 2 km s{sup -1} for the star; this is the same radial velocity as the rotating gas in the LMC's disk, which confirms its membership in the LMC and precludes it from being an unusual Galactic halo giant. Finally, we describe the star's unusual nebula emission spectrum; the gas is nitrogen-rich and shock-heated, and displays a radial velocity that is significantly more positive than the star itself by 50 km s{sup -1}.

Levesque, Emily M. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States); Massey, Philip [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Plez, Bertrand [GRAAL, Universite Montpellier, CNRS, 34095 Montpellier (France); Olsen, Knut A. G. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85748 (United States)], E-mail: emsque@ifa.hawaii.edu, E-mail: phil.massey@lowell.edu, E-mail: bertrand.plez@graal.univ-montp2.fr, E-mail: kolsen@noao.edu

2009-06-15

126

A Five-year Spectroscopic and Photometric Campaign on the Prototypical ? Cygni Variable and A-type Supergiant Star Deneb  

NASA Astrophysics Data System (ADS)

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 Strömgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H? profile, H? equivalent widths, and radial velocities measured from Si II ?? 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? 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.

Richardson, N. D.; Morrison, N. D.; Kryukova, E. E.; Adelman, S. J.

2011-01-01

127

Multiple flaring activity in the supergiant fast X-ray transient IGR J08408-4503 observed with Swift  

NASA Astrophysics Data System (ADS)

IGR J08408-4503 is a supergiant fast X-ray transient discovered in 2006 with a confirmed association with a O8.5Ib(f) supergiant star, HD 74194. We report on the analysis of two outbursts caught by Swift/Burst Alert Telescope (BAT) on 2006 October 4 and 2008 July 5, and followed up at softer energies with Swift/X-ray Telescope (XRT). The 2008 XRT light curve shows a multiple-peaked structure with an initial bright flare that reached a flux of ~10-9 ergcm-2s-1 (2-10keV), followed by two equally bright flares within 75ks. The spectral characteristics of the flares differ dramatically, with most of the difference, as derived via time-resolved spectroscopy, being due to absorbing column variations. We observe a gradual decrease in the NH, derived with a fit using absorbed power-law model, as time passes. We interpret these NH variations as due to an ionization effect produced by the first flare, resulting in a significant decrease in the measured column density towards the source. The durations of the flares as well as the times of the outbursts suggest that the orbital period is ~35 d, if the flaring activity is interpreted within the framework of the Sidoli et al. model with the outbursts triggered by the neutron star passage inside an equatorial wind inclined with respect to the orbital plane.

Romano, P.; Sidoli, L.; Cusumano, G.; Evans, P. A.; Ducci, L.; Krimm, H. A.; Vercellone, S.; Page, K. L.; Beardmore, A. P.; Burrows, D. N.; Kennea, J. A.; Gehrels, N.; La Parola, V.; Mangano, V.

2009-01-01

128

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)

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.

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

2012-01-01

129

Modelling Dusty Circumbinary Disk around B[e] Supergiant RY Sct  

NASA Astrophysics Data System (ADS)

The supergiant RY Sct is an eclipsing binary system with a fairly large infrared (IR) excess caused by the presence of circumbinary dust. Many strong forbidden lines ([O i], [N ii], [S iii], [Fe ii]), in combination with the near-IR excess, put it in the list of peculiar Be or B[e] stars. Although RY Sct is one of the best-studied systems, even its basic physical parameters remain unreliable. Recent IR images of the system, obtained with a 0.3 arcsec resolution at the 10-m Keck telescope, showed the dusty disk at the wavelengths 3-20 ?m and stimulated us to perform its detailed modelling using our 2-D radiative transfer code. Our model reproduces all available observations of RY Sct obtained during the last few decades. The modelling demonstrated that the observations cannot be described by a single model at one moment in time, implying rapid changes in the dusty disk during the last 20 years. Assuming that a temperature of 27,000 K describes both components of the binary and that its distance is 1.8 kpc, its total luminosity is 4.2 - 105 solar luminosity. The model disk has the optical depth of 0.04 and the opening angle of 26° (between the boundaries). Dust in the disk exists between 60 AU and 105 AU, where it blends into the interstellar medium. We observe the disk almost edge-on, at an angle of 14° to its midplane. The total mass of the disk is 0.017 solar mass. There is a strong density enhancement at 1800 AU from the binary, which emits most of the IR radiation and is prominent in the Keck telescope images. Presumably, the dense ring has been created by a fast wind that swept out and compressed the previously lost material in the older and slower stellar wind. Our model predicts that presently there is a large amount of small, hot dust grains in the dust formation zone, whose emission changed the shape of the SED of RY Sct in the near IR. The dust density must now be significantly greater in the dust formation zone, suggesting a much higher massloss rate or dust-to-gas mass ratio or much lower wind velocities than before, or a combination of these factors.

Men'shchikov, Alexander; Miroshnichenko, Anatoly

2005-08-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

131

The mass-loss rates of red supergiants and the de Jager prescription  

NASA Astrophysics Data System (ADS)

Mass loss of red supergiants (RSG) is important for the evolution of massive stars, but is not fully explained. Several empirical prescriptions have been proposed, trying to express the mass-loss rate (dot M) as a function of fundamental stellar parameters (mass, luminosity, effective temperature). Our goal is to test whether the de Jager et al. (1988, A&AS, 72, 259) prescription, which is used in some stellar evolution models, is still valid in view of more recent mass-loss determinations. By considering 40 Galactic RSGs with an infrared excess and an IRAS 60-?m flux larger than 2 Jy, and assuming a gas-to-dust mass ratio of 200, we find that the de Jager rate agrees within a factor 4 with most dot M estimates based on the 60-?m signal. It also agrees with six of the only eight Galactic RSGs for which dot M can be measured more directly through observations of the circumstellar gas. The two objects that do not follow the de Jager prescription (by an order of magnitude) are ? Cep and NML Cyg. We also considered the RSGs of the Magellanic Clouds. Thanks to the results of previous research, we find that the RSGs of the Small Magellanic Cloud have mass-loss rates consistent with the de Jager rate scaled by (Z/Z?)?, where Z is the metallicity and ? is 0.7. The situation is less clear for the RSGs of the Large Magellanic Cloud. In particular, for L > 1.6 × 105 L?, one finds numerous RSGs (except WOH-G64) with dot M significantly smaller than the de Jager rate and indicating that dot M would no longer increase with L. Before this odd situation is confirmed through further analyses of LMC RSGs, we suggest to keep the de Jager prescription unchanged at solar metallicity in the stellar evolutionary models and to apply a (Z/Z?)0.7 dependence. Appendices are only available in electronic form at http://www.aanda.org

Mauron, N.; Josselin, E.

2011-02-01

132

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

NASA Astrophysics Data System (ADS)

IGR J11215-5952 is a hard X-ray transient source discovered in 2005 April with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) and a member of the new class of high-mass X-ray binaries, the supergiant fast X-ray transients (SFXTs). While INTEGRAL and Rossi X-Ray Timing Explorer observations have shown that the outbursts occur with a periodicity of ~330 days, Swift data have recently demonstrated that the true outburst period is ~165 days. IGR J11215-5952 is the first discovered SFXT displaying periodic outbursts, which are possibly related to the orbital period. The physical mechanism responsible for the X-ray outbursts in SFXTs is still debated. The main hypotheses proposed to date involve the structure of the companion wind or gated mechanisms related to the properties of the compact object. We test our proposed model which explains the outbursts from SFXTs as being due to the passage of the neutron star inside the equatorially enhanced wind from the supergiant companion. We performed a Guest Investigator observation with Swift that lasted 20 ks and several follow-up Target of Opportunity (ToO) observations, for a total of ~32 ks, during the expected "apastron" passage (defined assuming an orbital period of ~330 days), between 2008 June 16 and July 4. The characteristics of this "apastron" outburst are quite similar to those previously observed during the "periastron" outburst of 2007 February 9. The mean spectrum of the bright peaks can be fitted with an absorbed power-law model with a photon index of 1 and an absorbing column of ~1022 cm-2. This outburst reached luminosities of ~1036 erg s-1 (1-10 keV), comparable with those measured in 2007. The light curve can be modeled with the parameters obtained by Sidoli et al. for the 2007 February 9 outburst, although some differences can be observed in its shape. The properties of the rise to this new outburst and the comparison with the previous outbursts allow us to suggest that the true orbital period of IGR J11215-5952 is very likely 164.6 days, and that the orbit is eccentric, with the different outbursts produced at the periastron passage, when the neutron star crosses the inclined equatorial wind from the supergiant companion. Based on a ToO observation performed on 2008 March 25-27, we can exclude that the period is 165/2 days.

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

2009-05-01

133

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

SciTech Connect

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 previous outbursts allow us to suggest that the true orbital period of IGR J11215-5952 is very likely 164.6 days, and that the orbit is eccentric, with the different outbursts produced at the periastron passage, when the neutron star crosses the inclined equatorial wind from the supergiant companion. Based on a ToO observation performed on 2008 March 25-27, we can exclude that the period is 165/2 days.

Romano, P.; Cusumano, G.; Vercellone, S.; Mangano, V. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via U. La Malfa 153, I-90146 Palermo (Italy); Sidoli, L. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via E. Bassini 15, I-20133 Milano (Italy); Krimm, H. A. [CRESST/Goddard Space Flight Center, Greenbelt, MD (United States)

2009-05-10

134

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

SciTech Connect

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. 79 refs.

Maggio, A.; Vaiana, G.S.; Haisch, B.M.; Stern, R.A.; Bookbinder, J. (Osservatorio Astronomico, Palermo (Italy) Lockheed Research Laboratories, Palo Alto, CA (USA) Joint Institute for Laboratory Astrophysics, Boulder, CO (USA) Smithsonian Astrophysical Observatory, Cambridge, MA (USA))

1990-01-01

135

Age dating stellar populations in the near infrared: an absolute age indicator from the presence/absence of red supergiants  

NASA Astrophysics Data System (ADS)

The determination of age is a critical component in the study of a population of stellar clusters. In this Letter, we present a new absolute age indicator for young massive star clusters based on J-H colour. This novel method identifies clusters as older or younger than 5.7 ± 0.8 Myr based on the appearance of the first population of red supergiant stars. We test the technique on the stellar cluster population of the nearby spiral galaxy, M83, finding good agreement with the theoretical predictions. The localization of this technique to the near-IR promises that it may be used well into the future with space- and ground-based missions optimized for near-IR observations.

Gazak, J. Z.; Bastian, N.; Kudritzki, R.-P.; Adamo, A.; Davies, B.; Plez, B.; Urbaneja, M. A.

2013-03-01

136

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

137

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

SciTech Connect

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

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

2010-09-20

138

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

SciTech Connect

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.

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

2012-03-01

139

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

SciTech Connect

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

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

2012-06-01

140

Broadband ESO/VISIR-Spitzer Infrared Spectroscopy of the Obscured Supergiant X-Ray Binary IGR J16318-4848  

NASA Astrophysics Data System (ADS)

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

Chaty, S.; Rahoui, F.

2012-06-01

141

Red-Eye Astronomy: 15 Years of V-band and Near-IR Tio Photometry of the Red Supergiants Alpha Orionis And TV Geminorum  

Microsoft Academic Search

V-band and narrow to intermediate-band Wing TiO-band (719 nm, 754 nm), and near-IR 1024 nm pseudo-bolometric photometric observations of the SRc M2 Iab supergiants Alpha Orionis and TV Geminorum have been conducted for the past 15 years. The goals are to monitor brightness and temperature-dependent TiO-band variations, ascertain any resulting periodicities and amplitudes, and estimate variations of basic stellar parameters

Richard P. Wasatonic; E. Guinan; S. Engle

2011-01-01

142

XMM-Newton observations of IGR J18410-0535: the ingestion of a clump by a supergiant fast X-ray transient  

NASA Astrophysics Data System (ADS)

Context. IGR J18410-0535 is a supergiant fast X-ray transients. This subclass of supergiant X-ray binaries typically undergoes few-hour-long outbursts reaching luminosities of 1036-1037 erg s-1, the occurrence of which has been ascribed to the combined effect of the intense magnetic field and rotation of the compact object hosted in them and/or the presence of dense structures ("clumps") in the wind of their supergiant companion. Aims: IGR J18410-0535 was observed for 45 ks by XMM-Newton as part of a program designed to study the quiescent emission of supergiant fast X-ray transients and clarify the origin of their peculiar X-ray variability. Methods: We carried out an in-depth spectral and timing analysis of these XMM-Newton data. Results: IGR J18410-0535 underwent a bright X-ray flare that started about 5 ks after the beginning of the observation and lasted for ~15 ks. Thanks to the capabilities of the instruments on-board XMM-Newton, the whole event could be followed in great detail. The results of our analysis provide strong convincing evidence that the flare was produced by the accretion of matter from a massive clump onto the compact object hosted in this system. Conclusions: By assuming that the clump is spherical and moves at the same velocity as the homogeneous stellar wind, we estimate a mass and radius of Mcl ? 1.4 × 1022 g and Rcl ? 8 × 1011 cm. These are in qualitative agreement with values expected from theoretical calculations. We found no evidence of pulsations at ~4.7 s after investigating coherent modulations in the range 3.5 ms-100 s. A reanalysis of the archival ASCA and Swift data of IGR J18410-0535, for which these pulsations were previously detected, revealed that they were likely to be due to a statistical fluctuation and an instrumental effect, respectively.

Bozzo, E.; Giunta, A.; Cusumano, G.; Ferrigno, C.; Walter, R.; Campana, S.; Falanga, M.; Israel, G.; Stella, L.

2011-07-01

143

Revisiting the absolute-magnitude calibration of F-type supergiants and bright giants as a function of the equivalent width of the OI?7774Å triplet  

NASA Astrophysics Data System (ADS)

We reduce the published measurements of the equivalent width of the oxygen triplet (Oi?7774Å) to a single system and combine the resulting homogenized indices with revised Hipparcos parallaxes to derive the MK versus log[W(Oi?7774Å)] absolute-magnitude calibration for bright F-type giants and supergiants and use the resulting calibration to estimate both the distance to the Large Magellanic Cloud and the parameters of the Galactic rotation curve.

Dambis, A. K.

2013-02-01

144

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

NASA Astrophysics Data System (ADS)

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 ?m 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.

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.

2013-10-01

145

Spectroscopy of Supergiants with IR-Excesses: RV Tau Type Stars  

Microsoft Academic Search

Using high resolution CCD spectra obtained with the echelle-spectrometers of the 6 m telescope, we determined by the model atmospheres method the parameters Te, log g and the detailed chemical composition for 4 RV Tau type pulsating stars in the galactic field: AC Her, U Mon, RV Tau and AI CMi. For the first time from high resolution spectra the

V. G. Klochkova; V. E. Panchuk

1999-01-01

146

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

SciTech Connect

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.

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

2012-06-01

147

IGR J17354–3255 as bench test for investigation of ?-ray emission from Supergiant Fast X-ray Transients  

NASA Astrophysics Data System (ADS)

Among the different types of sources shining in the high energy sky, gamma-ray binaries are rapidly becoming the subject of major interest. In fact, in the last few years a number of High Mass X-ray Binaries (HMXBs) have been firmly detected from MeV to TeV energies, providing secure evidences that particles can be efficiently accelerated up to very high energies in such galactic systems. Similarly to this general and emerging class of gamma-ray binaries, in principle Supergiant Fast X-ray Transients (SFXTs) have all the "ingredients" to be transient high energy emitters. In this context, the SFXT IGR J17354–3255 is a good bench test and we present intriguing hints likely suggesting that it is a transient gamma-ray source flaring on short timescales. If fully confirmed by further studies, the implications stemming are huge, both theoretically and observationally, and would add a further extreme characteristic to the already extreme class of SFXTs.

Sguera, V.

2013-06-01

148

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

NASA Astrophysics Data System (ADS)

Using different state-of-the-art techniques on ESO's Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. Betelgeuse - the second brightest star in the constellation of Orion (the Hunter) - is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun [1]. It is also one of the most luminous stars known, emitting more light than 100000 Suns. Such extreme properties foretell the demise of a short-lived stellar king. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight. Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material - about the mass of the Sun - in only 10 000 years. Two teams of astronomers have used ESO's Very Large Telescope (VLT) and the most advanced technologies to take a closer look at the gigantic star. Their combined work suggests that an answer to the long-open mass-loss question may well be at hand. The first team used the adaptive optics instrument, NACO, combined with a so-called "lucky imaging" technique, to obtain the sharpest ever image of Betelgeuse, even with Earth's turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be. The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution is as fine as 37 milliarcseconds, which is roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground. "Thanks to these outstanding images, we have detected a large plume of gas extending into space from the surface of Betelgeuse," says Pierre Kervella from the Paris Observatory, who led the team. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. "This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions," adds Kervella. Two mechanisms could explain this asymmetry. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection - similar to the circulation of water heated in a pot. To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry. With the AMBER instrument on ESO's Very Large Telescope Interferometer, which combines the light from three 1.8-metre Auxiliary Telescopes of the VLT, the astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such superb resolution, the astronomers were able to detect indirectly details four times finer still than the amazing NACO images had already allowed (in other words, the size of a marble on the ISS, as seen from the ground). "Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, we detected how the gas is moving in different areas of Betelgeuse's surface ? the first time this has been done for a star other than the Sun", says Ohnaka. The AMBER observations revealed that the gas in Betelgeuse's atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. Their unrivalled observations have led

2009-07-01

149

Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters  

NASA Astrophysics Data System (ADS)

We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H2O 616-523 maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v = 1, J = 1-0, and H2O 616-523 maser lines are detected toward two of four known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F 21/F 12) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in six massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H2O line tend to distribute in a region with large L values.

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

2012-11-01

150

Detection of circumstellar dust shell around the supergiant TV Geminorum from milliarcsecond resolution near-infrared observations.  

NASA Astrophysics Data System (ADS)

A lunar occultation of the M1 supergiant TV Gem has been observed in the near infrared region at 2.2?m. A detailed analysis of the observed occultation light curve has been performed using two different reduction methods permitting the circumstellar dust envelope to be directly detected for the first time around TV Gem. The star has been resolved to yield a uniform disk diameter of 4.9+/-0.3 milliarcseconds (mas) and the stellar effective temperature has been derived to be 3670+/-125K. Its circumstellar dust envelope has a radius of ~20R_*_ with star to shell flux ratio of ~35 at 2.2?m. A simple radiative transfer dust shell model constrained by our occultation observations, 9.7?m silicate emission feature strength and far IR excess seen in IRAS observations shows that the dust is probably restricted to two well separated dust shells - the inner shell is at a radial distance of ~20R_*_ and the outer one is at ~500R_*_. Sporadic dust condensation in TV Gem as in the case of ? Ori is suggested.

Ragland, S.; Chandrasekhar, T.; Ashok, N. M.

1997-03-01

151

Swift/XRT orbital monitoring of the candidate supergiant fast X-ray transient IGR J17354-3255  

NASA Astrophysics Data System (ADS)

We report on the Swift/X-ray Telescope (XRT) monitoring of the field of view around the candidate supergiant fast X-ray transient (SFXT) IGR J17354-3255, which is positionally associated with the AGILE/GRID gamma-ray transient AGL J1734-3310. Our observations, which cover 11 days for a total on-source exposure of ~24 ks, span 1.2 orbital periods (Porb = 8.4474 d) and are the first sensitive monitoring of this source in the soft X-rays. These new data allow us to exploit the timing variability properties of the sources in the field to unambiguously identify the soft X-ray counterpart of IGR J17354-3255. The soft X-ray light curve shows a moderate orbital modulation and a dip. We investigated the nature of the dip by comparing the X-ray light curve with the prediction of the Bondi-Hoyle-Lyttleton accretion theory, assuming both spherical and nonspherical symmetry of the outflow from the donor star. We found that the dip cannot be explained with the X-ray orbital modulation. We propose that an eclipse or the onset of a gated mechanism is the most likely explanation for the observed light curve.

Ducci, L.; Romano, P.; Esposito, P.; Bozzo, E.; Krimm, H. A.; Vercellone, S.; Mangano, V.; Kennea, J. A.

2013-08-01

152

Discovery of a short orbital period in the Supergiant Fast X-ray Transient IGR J16479-4514  

NASA Astrophysics Data System (ADS)

We report here the discovery of a 3.32 d orbital period in the Supergiant Fast X-ray Transient (SFXT) source IGR J16479-4514. Using the long-term light curve of this source obtained with Swift Burst Alert Telescope (BAT) in the energy range of 15-50 keV, we have clearly detected an orbital modulation including a full eclipse of duration ~0.6 d. In the hard X-ray band of the BAT instrument, the eclipse ingress and egress are rapid. We have also used the long-term light curve obtained with the Rossi X-ray Timing Explorer (RXTE) All Sky Monitor (ASM) in the energy range of 1.5-12 keV. Taken independently, the detection of orbital modulation in the RXTE-ASM light curve is not significant. However, considering a clear detection of orbital modulation in the BAT light curve, we have used the ASM light curve for a more precise determination of the orbital period. IGR J16479-4514 has the shortest orbital period among the three SFXTs with measured/known orbital period. We discuss the implication of a short orbital period with the various mechanisms proposed to explain the transient nature of this class of sources.

Jain, Chetana; Paul, Biswajit; Dutta, Anjan

2009-07-01

153

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

SciTech Connect

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

Fok, Thomas K. T.; Nakashima, Jun-ichi; Yung, Bosco H. K.; Hsia, Chih-Hao [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Deguchi, Shuji, E-mail: junichi@hku.hk [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)

2012-11-20

154

A spectroscopic study of supergiants with infrared excesses: Pulsating RV Tau stars  

Microsoft Academic Search

We use high-resolution CCD spectra from the LYNX echelle spectrometer of the 6-m telescope to determine the fundamental parameters T_eff and log g and the detailed chemical composition for four pulsating RV Tau stars in the Galactic field - AC Her, U Mon, RV Tau, and AI CMi - by the method of model atmospheres. Based on high-resolution spectra, we

V. G. Klochkova; V. E. Panchuk

1998-01-01

155

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

NASA Astrophysics Data System (ADS)

Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6 m telescope, under programme LP185.D-0056. Based on observations obtained with the HERMES spectrograph attached to the 1.2 m Mercator telescope, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientific (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany. Based on observations obtained with the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU).

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

2013-09-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

157

A double detached shell around a post-red supergiant: IRAS 17163-3907, the Fried Egg nebula  

NASA Astrophysics Data System (ADS)

Context. We performed a mid-infrared imaging survey of evolved stars to study the dust distribution in circumstellar envelopes around these objects and to understand the mass-loss mechanism responsible for the formation of these envelopes better. During this survey, we resolved the circumstellar environment of IRAS 17163-3907 for the first time (hereafter IRAS 17163), which is one of the brightest objects in the mid-infrared sky, but is surprisingly not well studied. Aims: Our aim is to determine the evolutionary status of IRAS 17163 and study its circumstellar environment to understand its mass-loss history. Methods: We obtained diffraction-limited images of IRAS 17163 in the mid-infrared using VISIR on the VLT. Optical spectra of the object allowed us to determine its spectral type and estimate its distance through diffuse interstellar bands. Results: We show that IRAS 17163 is a post-red supergiant, possibly belonging to the rare class of yellow hypergiants, and is very similar to the well-studied object IRC +10420. Our mid-infrared images of IRAS 17163 are the first direct images of this bright mid-infrared source. These images clearly show a double dusty detached shell around the central star, caused by successive ejections of material on a timescale of the order of 400 years and a total circumstellar mass exceeding than 4 M?. This indicates that non-quiescent mass-loss occurs during this phase of stellar evolution. Based on observations made with the Very Large Telescope at Paranal Observatory under program 081.D-0130(A).Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias.

Lagadec, E.; Zijlstra, A. A.; Oudmaijer, R. D.; Verhoelst, T.; Cox, N. L. J.; Szczerba, R.; Mékarnia, D.; van Winckel, H.

2011-10-01

158

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)

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.

Barba, Rodolfo; Gamen, Roberto; Morrell, Nidia

2006-05-01

159

From B[e] to A[e]. On the peculiar variations of the SMC supergiant LHA 115-S 23 (AzV 172)  

NASA Astrophysics Data System (ADS)

Context: Optical observations from 1989 of the Small Magellanic Cloud (SMC) B[e] supergiant star LHA 115-S 23 (in short: S 23) revealed the presence of photospheric Hei absorption lines, classifying S 23 as a B8 supergiant. In our high-resolution optical spectra from 2000, however, we could not identify any Hei line. Instead, the spectral appearance of S 23 is more consistent with the classification as an A1 supergiant, maintaining the so-called B[e] phenomenon. Aims: The observed changes in spectral behaviour of S 23 lead to different spectral classifications at different observing epochs. The aim of this research is, therefore, to find and discuss possible scenarios that might cause a disappearance of the photospheric Hei absorption lines within a period of only 11 years. Methods: From our high-resolution optical spectra, we perform a detailed investigation of the different spectral appearances of S 23 based on modern and revised classification schemes. In particular, we derive the contributions caused by the interstellar as well as the circumstellar extinction self-consistently. The latter is due to a partly optically thick wind. We further determine the projected rotational velocities of S 23 in the two epochs of spectroscopic observations. Results: Based on its spectral appearance in 2000, we classify S 23 as A1 Ib star with an effective temperature of about 9000 K. This classification is supported by the additional analysis of the photometric UBV data. An interstellar extinction value of E(B-V) ? 0.03 is derived. This is considerably lower than the previously published value, which means that, if the circumstellar extinction due to the stellar wind is neglected, the interstellar extinction, and hence the luminosity of the star, are overestimated. We further derive a rotation velocity of ? sin i ? 150 km s-1, which means that S 23 is rotating with about 75% of its critical speed. The object S 23 is thus the fourth B[e] supergiant with confirmed high projected rotational velocity. The most striking result is the apparent cooling of S 23 by more than 1500 K with a simultaneous increase of its rotation speed by about 35% within only 11 years. Since such a behaviour is excluded by stellar evolution theories, we discuss possible scenarios for the observed peculiar variations in S 23.

Kraus, M.; Borges Fernandes, M.; Kubát, J.; de Araújo, F. X.

2008-08-01

160

The Aro 1 mm Survey of the Oxygen-Rich Envelope of Supergiant Star NML Cygnus  

NASA Astrophysics Data System (ADS)

Although a number of molecular line surveys of carbon-rich circumstellar envelopes (CSE) have been performed, only one oxygen-rich CSE, that of VY Canis Majoris (VY CMa), has been studied in depth. The Arizona Radio Observatory (ARO) 1 mm survey of VY CMa showed a very different and interesting chemistry dominated by sulfur- and silicon-bearing compounds as well as a number of more exotic species. A similar survey of the oxygen rich star NML Cygnus (NML Cyg) from 215 to 285 GHz is currently under way using the ARO Sub-millimeter Telescope. Initial observations show that this circumstellar envelope appears to be as chemically rich as that of VY CMa. Molecules including 12CO, 13CO, 12CN, 13CN, HCN, HCO+, CS, SO{_2}, SiO and 30SiO have been observed in NML Cyg. Line profiles of this source also suggest that there may be multiple outflows and that the circumstellar envelope is not spherically symmetric. Current results will be presented.

Edwards, Jessica L.; Ziurys, L. M.; Woolf, N. J.

2011-06-01

161

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

SciTech Connect

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.

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

2011-01-15

162

Anomaly distribution of quasar magnitudes: a test of lensing by a hypothetic supergiant molecular cloud in the Galactic halo  

NASA Astrophysics Data System (ADS)

Context. An anomaly in the distribution of quasar magnitudes based on the Sloan Digital Sky survey, was reported by Longo. The angular size of this quasar anomaly is on the order of ±15° on the sky. A smooth low surface brightness structure detected in ?-rays and at 408 MHz, coincides with the sky location and extent of the anomaly, and is close to the northern component of a pair of ?-ray bubbles discovered in the Fermi Gamma-ray Space Telescope survey. Molecular clouds are thought to be illuminated by cosmic rays. Molecular gas in the Galaxy, in the form of cold H2, may be a significant component of dark matter as suggested by Pfenniger et al. Aims: I test the hypothesis that the magnitude anomaly in the quasar distribution, is due to lensing by a hypothetical supergiant molecular cloud (SGMC) either in or falling into the Galactic halo. Methods: A series of grid lens models are built by assuming that a SGMC is a fractal structure constructed with clumps of 10-3 M?, 10 AU in size, and considering various fractal dimensions. Local amplifications are computed by using the single-plane approximation. Results: A complex network of caustics due to the clumpy structure is present. Our best single plane lens model capable of explaining Longo's effect, at least in sparse regions, requires a mass (1.5-4.1) × 1010 M? within 8.7 × 8.7 × (5-8.6) kpc3 at a lens plane distance of 20 kpc, and is constructed from a molecular-cloud building-block of 5 × 105 M? within a scale of 30 pc expanded by fractal scaling with dimension D = 1.8-2 out to 5-8.6 kpc for the SGMC. The mass budget depends on the cloud depth and on the fractal dimension. Conclusions: If such a SGMC were found to exist, it may provide at least part of a lensing explanation for the luminous anomaly discovered in quasars and red galaxies.

Giraud, E.

2012-07-01

163

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

ERIC Educational Resources Information Center

|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.…

Klein, Alyson

2012-01-01

164

Distance and Proper Motion Measurement of the Red Supergiant, PZ Cas, in Very Long Baseline Interferometry H2O Maser Astrometry  

NASA Astrophysics Data System (ADS)

We present the very long baseline interferometry H2O 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 ^{*}_{\\alpha } \\cos {\\delta }=-3.7 +/- 0.2 and \\mu ^{*}_{\\delta }=-2.0 +/- 0.3 mas yr–1 eastward and northward, respectively. The annual parallax corresponds to a trigonometric parallax of 2.81 ^{+0.22}_{-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 ~25 M ?. 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 s = 22.8 ± 1.5, V s = 7.1 ± 4.4, and W s = –5.7 ± 4.4 km s–1. This peculiar motion has rather a large U s component, unlike those of near high-mass star-forming regions with negatively large V 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.

Kusuno, K.; Asaki, Y.; Imai, H.; Oyama, T.

2013-09-01

165

SUZAKU OBSERVES WEAK FLARES FROM IGR J17391-3021 REPRESENTING A COMMON LOW-ACTIVITY STATE IN THIS SUPERGIANT FAST X-RAY TRANSIENT  

SciTech Connect

We present an analysis of a 37 ks observation of the supergiant fast X-ray transient IGR J17391-3021 (= XTE J1739-302) gathered with Suzaku. The source evolved from quiescence to a low-activity level culminating in three weak flares lasting {approx}3 ks each in which the peak luminosity is only a factor of five times that of the pre-flare luminosity. The minimum observed luminosity was 1.3 x 10{sup 33} erg s{sup -1}(d/2.7 kpc){sup 2} in the 0.5-10 keV range. The weak flares are accompanied by significant changes in the spectral parameters including a column density (N{sub H} =(4.1{sup +0.4}{sub -0.5}) x 10{sup 22} cm{sup -2}) that is {approx}2-9 times the absorption measured during quiescence. Accretion of obscuring clumps of stellar wind material can explain both the small flares and the increase in N{sub H}. Placing this observation in the context of the recent Swift monitoring campaign, we find that weak-flaring episodes, or at least epochs of enhanced activity just above the quiescent level but well below the moderately bright or high-luminosity outbursts, represent more than 60% {+-} 5% of all observations in the 0.5-10 keV energy range making this the most common state in the emission behavior of IGR J17391-3021.

Bodaghee, A.; Tomsick, J. A. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 (United States); Rodriguez, J.; Chaty, S. [Laboratoire AIM, CEA/IRFU-Universite Paris Diderot-CNRS/INSU, CEA DSM/IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette (France); Pottschmidt, K. [CRESST and NASA Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771 (United States); Walter, R. [INTEGRAL Science Data Centre, Universite de Geneve, Chemin d'Ecogia 16, CH-1290 Versoix (Switzerland); Romano, P., E-mail: bodaghee@ssl.berkeley.edu [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via U. La Malfa 153, I-90146 Palermo (Italy)

2011-01-20

166

Elemental abundance analyses with DAO spectrograms: XXXI. The early F supergiants ? Her (F2 II) and 41 Cyg (F5 Ib-II)  

NASA Astrophysics Data System (ADS)

This series of high quality elemental abundance analyses of mostly Main Sequence normal and peculiar B, A, and F stars defines their properties and provides data for the comparison with analyses of somewhat similar stars and with theoretical predictions. Most use high dispersion and high S/N (? 200) spectrograms obtained with CCD detectors at the long camera of the 1.22-m Dominion Astrophysical Observatory telescope's coudé spectrograph. Here we expand the range of stars examined to include two relatively quiescent F supergiants. ? Her (F2 II) and 41 Cyg (F5 Ib-II) are analyzed as consistently as possible with previous studies. These LTE fine analyses use the ATLAS9 and the WIDTH9 programs of R. L. Kurucz. High signal-to-noise spectrograms and high quality atomic data were employed. The derived values of these photometrically constant stars are somewhat different with the abundances of ? Her being somewhat metal-poor and those of 41 Cyg being crudely solar-like. Our analyses indicate that the basic results of Luck & Wepfer (1995) who also studied ? Her and 41 Cyg are not likely to be significantly changed by new studies of all their stars. Table 3 of this article is available at the CDS via http://cdsarc.u-strasbg.fr/ftp/cats/J/other/AN/329.4

Adelman, S. J.; Cay, I. H.; Tektunali, H. G.; Gulliver, A. F.; Teker, A.

2008-01-01

167

Suzaku Observes Weak Flares from IGR J17391-3021 Representing a Common Low-activity State in this Supergiant Fast X-ray Transient  

NASA Astrophysics Data System (ADS)

We present an analysis of a 37 ks observation of the supergiant fast X-ray transient IGR J17391-3021 (= XTE J1739-302) gathered with Suzaku. The source evolved from quiescence to a low-activity level culminating in three weak flares lasting ~3 ks each in which the peak luminosity is only a factor of five times that of the pre-flare luminosity. The minimum observed luminosity was 1.3 × 1033 erg s-1(d/2.7 kpc)2 in the 0.5-10 keV range. The weak flares are accompanied by significant changes in the spectral parameters including a column density (N H =(4.1+0.4 -0.5) × 1022 cm-2) that is ~2-9 times the absorption measured during quiescence. Accretion of obscuring clumps of stellar wind material can explain both the small flares and the increase in N H. Placing this observation in the context of the recent Swift monitoring campaign, we find that weak-flaring episodes, or at least epochs of enhanced activity just above the quiescent level but well below the moderately bright or high-luminosity outbursts, represent more than 60% ± 5% of all observations in the 0.5-10 keV energy range making this the most common state in the emission behavior of IGR J17391-3021.

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

2011-01-01

168

The Contribution of Thermally-Pulsing Asymptotic Giant Branch and Red Supergiant Stars to the 1--24 Micron Flux of the Magellanic Clouds  

NASA Astrophysics Data System (ADS)

Dust enshrouded Asymptotic Giant Branch (AGB) stars and their more massive counterparts, Red Supergiants (RSG), are among the brightest near- and mid-infrared (IR) sources in a galaxy. These stars constitute a tiny fraction of a galaxy's stellar mass, and yet can account for large fractions of the integrated near and mid-IR flux. Underestimating the AGB and RSG contributions to the IR luminosity can result in severely over-estimating a galaxy's stellar mass as well as inflation of the star formation rate estimated from the 8-micron rest-frame flux. Despite their importance, the AGB and RSG flux contribution has only been measured in a handful of galaxies at a handful of wavelengths. Recent Spitzer Space Telescope observations of the Small and Large Magellanic Clouds offer the first opportunity to quantify the IR contribution of the complete population of Thermally-pulsing (TP-)AGB stars and RSG stars to the total integrated IR light from 1 -24 microns. We find that the TP-AGB + RSG flux contribution peaks at 30% at 3--5 microns in the SMC and 25% in the LMC. Even at 8 microns these stars account for 20% of the SMC flux, with nearly half of that flux coming from a handful (3% of the AGB population) of extreme carbon stars. In the LMC, where PAH emission in the interstellar medium is stronger, the 8 micron TP-AGB + RSG flux contribution is much smaller, 4%.

Boyer, Martha L.; Melbourne, J.

2013-01-01

169

Chemical Changes  

NSDL National Science Digital Library

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

Jolley, Mr.

2005-10-25

170

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

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.

Miura, Rie; Okumura, Sachiko K.; Kurono, Yasutaka; Nakanishi, Kouichiro [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Tosaki, Tomoka [Joetsu University of Education, Yamayashiki-machi, Joetsu, Niigata 943-8512 (Japan); Tamura, Yoichi [Department of Astronomy, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 133-0033 (Japan); Kuno, Nario; Kawabe, Ryohei [Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1805 (Japan); Sakamoto, Seiichi [Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara-shi, Kanagawa 252-5210 (Japan); Hasegawa, Takashi, E-mail: rie.miura@nao.ac.j [Gunma Astronomical Observatory, Nakayama, Takayama, Agatsuma, Gunma 377-0702 (Japan)

2010-12-01

171

Red-Eye Astronomy: 15 Years of V-band and Near-IR Tio Photometry of the Red Supergiants Alpha Orionis And TV Geminorum.  

NASA Astrophysics Data System (ADS)

V-band and narrow to intermediate-band Wing TiO-band (719 nm, 754 nm), and near-IR 1024 nm pseudo-bolometric photometric observations of the SRc M2 Iab supergiants Alpha Orionis and TV Geminorum have been conducted for the past 15 years. The goals are to monitor brightness and temperature-dependent TiO-band variations, ascertain any resulting periodicities and amplitudes, and estimate variations of basic stellar parameters such as temperature, luminosity, and radius. Preliminary results for both stars indicate similar long-term V-mag periods of 6.5 years with imposed shorter-term V-mag periods of 1.2 years. The V-magnitude amplitudes were 0.8 for Alpha Ori and 1.3 for TV Gem. For both stars the temperature and luminosity variations correlate well with the V-mag changes. However, inverse radii correlations with respect to temperature and luminosity variations were not seen in either star. In Alpha Ori the the radii changes were approximately in direct correlation with the temperature and luminosity changes. In TV Gem there was a combination of correlation/inverse correlation effects. Causes for these variations are speculative, but may be due to highly convective super-granulations occurring at irregular intervals rather than fundamental mode pulsation or harmonic oscillations. Based in part on an updated RSG temperature scale and a new VLA/Hipparchos distance estimate (197 PC), the Alpha Ori temperatures ranged from 3550 K to 3730 K, with ranges in solar luminosities and radii of L = 90,000 to 115,000 and R = 760 to 820, respectively. The slightly more dynamical TV Gem underwent temperature variations from 3500 K to 3850 K with ranges in solar luminosity and radii of L = 65,000 to 90,000 and R = 620 to 720 respectively. Discussions of the observations, data reduction methods, and analysis of the data will be presented. This research is supported by NASA grant NNX10AI85G and NSF grants AST 10-09903 and AST 05-07542.

Wasatonic, Richard P.; Guinan, E.; Engle, S.

2011-05-01

172

Yellow supergiants in open clusters  

NASA Astrophysics Data System (ADS)

Superluminous giant stars (SLGs) have been reported in young globular clusters in the Large Magellanic Cloud (LMC). These stars appear to be in the post asymptotic giant branch phase of evolution. This program was an investigation of galactis SLG candidates in open clusters, which are more like the LMC young globular clusters. These were chosen because luminosity, mass, and age determination can be made for members since cluster distances and interstellar reddenings are known. Color magnitude diagrams were searched for candidates, using the same selection criteria as for SLGs in the LMC. Classification spectra were obtained of 115 program stars from McGraw-Hill Observatory and of 68 stars from Cerro Tololo Inter-American Observatory in Chile. These stars were visually classified on the MK system using spectral scans of standard stars taken at the respective observations. A total of 62 objects were found to be of high luminosity and to warrant further investigations. Seven stars were monitored over a 90 day period for luminosity variations. These observations were analyzed to measure radial velocities and to detect emission features.

Sowell, James Robert

1986-09-01

173

Chemical Biology\\/ Chemical Genetics\\/ Chemical Genomics: Importance of Chemical Library  

Microsoft Academic Search

A new field of science, chemical biology\\/ chemical genetics\\/ chemical genomics (cb\\/cg\\/cg) has emerged since the late 1990's, especially in the United States. The NIH Roadmap agenda, Molecular Libraries Screening Center Network (MLSCN), became a drive force to push cb\\/cg\\/cg forward. Cb\\/cg\\/cg studies consist of three methodologies, chemical libraries with small molecules, high-throughput screenings, and computational databases. In this review,

Fumihiko Kugawa; Masaru Watanabe; Fuyuhiko Tamanoi

2007-01-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

175

[Chemical weapons and chemical terrorism].  

PubMed

Chemical Weapons are kind of Weapons of Mass Destruction (WMD). They were used large quantities in WWI. Historically, large quantities usage like WWI was not recorded, but small usage has appeared now and then. Chemical weapons are so called "Nuclear weapon for poor countrys" because it's very easy to produce/possession being possible. They are categorized (1) Nerve Agents, (2) Blister Agents, (3) Cyanide (blood) Agents, (4) Pulmonary Agents, (5) Incapacitating Agents (6) Tear Agents from the viewpoint of human body interaction. In 1997 the Chemical Weapons Convention has taken effect. It prohibits chemical weapons development/production, and Organization for the Prohibition of Chemical Weapons (OPCW) verification regime contributes to the chemical weapons disposal. But possibility of possession/use of weapons of mass destruction by terrorist group represented in one by Matsumoto and Tokyo Subway Sarin Attack, So new chemical terrorism countermeasures are necessary. PMID:16296384

Nakamura, Katsumi

2005-10-01

176

Chemical microsensors  

DOEpatents

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.

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

1995-01-01

177

Chemical Bonds  

NSDL National Science Digital Library

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

Consortium, The C.

2011-12-11

178

Chemical agents and chemical terrorism.  

PubMed

Chemical terrorism is a new threat to the security of mankind, which scale essentially exceeds the impact of use of the most modem firearms. At present time all over the world threats from different radical elements to use radioactive materials, potent poisonous substances and pathogenic microorganisms for terrorist purposes became more frequent. High-toxic chemical substances can fall in terrorist hands through wide range of sources. Potentially misused types of chemical compounds are discussed in this article. PMID:15141987

Patocka, J; Fusek, J

2004-03-01

179

A Tale of Two Stars: The Extreme O7 Iaf+ Supergiant AV 83 and the OC7.5 III((f)) star AV 69  

NASA Astrophysics Data System (ADS)

We present a detailed study of AV 83, an O7 Iaf+ supergiant, and AV 69 [OC7.5 III((f))] in the SMC. The stars have similar effective temperatures and luminosities but show very different wind signatures. For our study we have used the non-LTE line-blanketed atmosphere code developed by Hillier and Miller, which explicitly allows for line blanketing by C, N, O, S, Ar, Ne, Fe, and other elements. Our study finds that AV 83 has an effective temperature of approximately 33,000 K and logg~3.25. It has an extended photosphere as a result of a ``low'' effective surface gravity and a much denser wind than main-sequence O stars. We can match the spectrum only by using a slow velocity law with ?~2, a value that is much larger than the values of around 1 predicted by standard radiation wind theory. Further, we show that the H? emission profile in AV 83 is sensitive to the adopted surface gravity. To fit the spectrum of AV 83, we have considered conventional models in which the wind is smooth and alternate models in which the winds are highly clumped. Both types of winds yield a satisfactory fit to the majority of lines in the observed spectrum; however, strong UV photospheric lines and the P V resonance transitions favor a clumped wind. If clumping is important, it must begin at relatively low velocities (i.e., 30 km s-1, not 300 km s-1). In the smooth wind, the line force is too small to drive the wind. In the clumped wind, the line force is generally sufficient to drive the wind, although there are still some discrepancies around the sonic point. In AV 83, the N abundance is substantially enhanced relative to normal SMC abundances, while both C and O are SMC-like, consistent with the presence of internally processed CNO material at the stellar surface. The N III ?4640 multiplet, which is known to be produced by dielectronic recombination, is well reproduced by the models. These lines, and the adjacent C III ?4649 multiplet, show a significant sensitivity to surface gravity, as well as the usual sensitivity to abundance and effective temperature. Incoherent electron scattering, occurring within the photosphere, can explain the broad wings seen on these lines. We have modeled the Fe spectrum (Fe IV-Fe VI) in the UV in both AV 83 and AV 69. For stars with an effective temperature around 33,000 K, the Fe IV-to-Fe V line ratios form a useful effective temperature diagnostic and give results consistent with those found from optical and UV line diagnostics. The derived iron abundance, which is sensitive to the adopted microturbulent velocity, is 0.2-0.4 times the solar iron abundance in AV 83, while 0.2 solar gives a good fit for AV 69. The wind of AV 69 is substantially less dense than that of AV 83. Because of the lack of suitable diagnostics, it is impossible to constrain the mass-loss rate and velocity law independently. Its spectrum indicates that it has a similar effective temperature to AV 83 (Teff~34,000 K), a substantially higher gravity (logg=3.5) than AV 83, and a CNO abundance pattern that has not been influenced by internal CNO processing. We show that the N/C abundance ratio is substantially below solar, in agreement with SMC nebular and stellar abundance studies. The differences between the spectra of AV 83 and AV 69, and between the derived masses and surface abundances, are striking. We have examined possible causes, and only one seems consistent with the observations and our current understanding of massive star evolution. AV 83 was most likely a fast rotator that experienced rotationally enhanced mass loss. The presence of enhanced N but almost normal C and O abundances is a direct indication of rotationally induced mixing. On the other hand, AV 69 is a slow rotator. As part of our analyses, we have systematically examined the influence of the H/He abundance ratio, the mass-loss rate, the velocity law, the Fe abundance, microturbulence, and clumping on the theoretical spectrum. We illustrate which lines provide useful diagnostics and highlight some of the difficulties associated with spectroscopic analyses of O st

Hillier, D. John; Lanz, T.; Heap, S. R.; Hubeny, I.; Smith, L. J.; Evans, C. J.; Lennon, D. J.; Bouret, J. C.

2003-05-01

180

Chemical Reactions  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

2009-05-01

181

Chemical spectroscopy  

Microsoft Academic Search

The purpose of chemical spectroscopy with neutrons is to utilize the dependence of neutron scattering cross sections on isotope and on momentum transfer (which probes the spatial extent of the excitation) to understand fundamental and applied aspects of the dynamics of molecules and fluids. Chemical spectroscopy is divided into three energy ranges: vibrational spectroscopy, 25-500 MeV, for which much of

J. Eckert; T. O. Brun; A. J. Dianoux; J. Howard; J. J. Rush; J. W. White

1984-01-01

182

Chemical sensors  

DOEpatents

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.

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

1991-07-02

183

Chemical Composition  

Microsoft Academic Search

Measurements of the chemical compositions of materials and the levels of certain substances in them are vital when assessing and improving public health, safety and the environment, are necessary to ensure trade equity, and are required when monitoring and improving industrial products and services. Chemical measurements play a crucial role in most areas of the economy, including healthcare, food and

Willie May; Richard Cavanagh; Gregory Turk; Michael Winchester; John Travis; Melody Smith; Paul Derose; Steven Choquette; Gary Kramer; John Sieber; Robert Greenberg; Richard Lindstrom; George Lamaze; Rolf Zeisler; Michele Schantz; Karen Phinney; Michael Welch; Thomas Vetter; Kenneth Pratt; John Scott; John Small; Scott Wight; Stephan Stranick

2006-01-01

184

Chemical Name  

Cancer.gov

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

185

Chemical threats.  

PubMed

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. PMID:16781273

Fry, Donald E

2006-06-01

186

Chemical Agents  

Center for Drug Evaluation (CDER)

... FDA has cleared for use by the US military a liquid decontamination lotion intended to remove or neutralize chemical warfare agents and T-2 fungal ... More results from www.fda.gov/drugs/emergencypreparedness/bioterrorismanddrugpreparedness

187

Unnecessary Chemicals  

ERIC Educational Resources Information Center

|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)|

Johnson, Anita

1978-01-01

188

Unnecessary Chemicals  

ERIC Educational Resources Information Center

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)

Johnson, Anita

1978-01-01

189

Chemical Emergency  

MedlinePLUS

... Prepare Your Workplace Types of Emergency Chemical Emergency Drought Preparedness Earthquake Home Fire Flood Flu Food Safety ... you have been advised by medical professionals. Next Drought Preparedness & Water Conservation Be Red Cross Ready Are ...

190

Chemical Kinetics  

Microsoft Academic Search

\\u000a While thermodynamics provides steady-state information of the combustion process, chemical kinetics describes the transient\\u000a states of the system during the combustion process. Particularly important is information related to the rate at which species\\u000a are consumed and produced, and the rate at which the heat is released. Combustion chemistry has two important characteristics\\u000a not commonly observed in other chemical systems. First,

Sara McAllister; Jyh-Yuan Chen; A. Carlos Fernandez-Pello

191

Eight Years of Watching TV (Gem) - Unraveling Long ( ˜6.2 yr.) and Short-term ( ˜400 d) Pulsations of the Red Supergiant TV Gem: Changes in Luminosity, Radius, and Teff.  

NASA Astrophysics Data System (ADS)

TV Gem (HD 42475) is a semi-regular M1 Iab supergiant accompanied by a less luminous B3.5 IV companion. The star is a bright (V = 6.2 to 6.8) member of the Gem OB1 Association at a distance of ˜1.2 kpc. Recent lunar occultation interferometric K-band observations by Mondal and Chandrasekhar yield an angular diameter of 4.46 ± 0.07 mas and show the presence of two dust shells located at ˜13 and ˜500 stellar radii from the star. Since 1997 we have been carrying out intensive V-band and narrow-to-intermediate band Wing near-IR (712 nm, 754 nm, and 1040 nm) photometry. This photometry indicates, for the first time, the presence of a long-term period of ˜6.16 years and the more familiar lower amplitude semi-regular (350-450 d) brightness changes. Variations in the molecular TiO ? (0,0) 719 nm band strength are determined from the near-IR observations, and yield spectral type changes from M1 (Teff ˜ 3750K) at maximum light to M3 (Teff ˜ 3450K) at minimum light. A near-IR color index and the TiO strengths are also used to estimate effective temperature, luminosity, and radius variations throughout the pulsational cycles. These variations indicate that TV Gem pulsates in the fundamental mode globally with the observed 6.16 year period. However, the year-by-year light variations are more complex, implying that on smaller local atmospheric scales TV Gem does not follow simplified models of a spherically symmetrical pulsating star. The overall photometrically determined mean values of Teff, Luminosity, and Radius are -- Teff ˜ 3600K, L ˜ 80000 Lsun, and R ˜ 700 Rsun. The observed long-term variation patterns and calculated ranges of these parameters may provide deeper insights into pulsational theories of TV Gem in particular and luminous M-types supergiants in general. This research is supported in part by NSF/RUI Grants AST-0507542 and AST-0507536 which we gratefully acknowledge.

Wasatonic, R.; Guinan, E.; Engle, S.

2005-12-01

192

Chemical Warfare and Chemical Disarmament.  

ERIC Educational Resources Information Center

|Described are some of the technical, military, and political considerations that bear most directly on the choices facing the United States and its NATO allies on modern lethal chemical weapons. (BT)|

Meselson, Matthew; Robinson, Julian Perry

1980-01-01

193

Chemical sensors  

SciTech Connect

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.

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

1987-05-01

194

Chemical sensors  

SciTech Connect

This review of chemical sensors contains the following topics of interest: books and reviews; reviews of sensors by their type; fabrication and selectivity; data processing; thermal sensors; mass sensors (fabrication, gas sensors, and liquid sensors); electrochemical sensors (potentiometric sensors, amperometric sensors, and conductometric sensors); and optical sensors (fabrication, liquid sensors, biosensors, and gas sensors). 795 refs., 1 tab.

Janata, J.; Josowicz, M.; DeVaney, D.M. (Pacific Northwest Lab., Richland, WA (United States))

1994-06-15

195

Delicious Chemicals.  

ERIC Educational Resources Information Center

|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…

Barry, Dana M.

196

Chemical Ionization  

Microsoft Academic Search

\\u000a Mass spectrometrists have ever been searching for ionization methods softer than EI, because molecular weight determination\\u000a is key for structure elucidation. Chemical ionization (CI) is the first of the so-called soft ionization methods we are going to discuss (cf. Fig. 1.2).

Jürgen H. Gross; Mass Spectrometry

197

Chemical Mahjong  

ERIC Educational Resources Information Center

|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…

Cossairt, Travis J.; Grubbs, W. Tandy

2011-01-01

198

Chemical Indicators.  

ERIC Educational Resources Information Center

|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…

Prombain, Dorothy R.; And Others

199

Chemical Separations  

NSDL National Science Digital Library

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

2011-05-18

200

Chemical lasers  

NASA Astrophysics Data System (ADS)

The application and the advances of quantum electronics, specifically, of optical quantum generators lasers is reviewed. Materials are cut, their surfaces are machined, chemical transformations of substances are carried out, surgical operations are performed, data are transmitted, three dimensional images are produced and the content of microimpurities, in the atmosphere, are analyzed by use of a beam. Laser technology is used in conducting investigations in the most diverse fields of the natural and technical sciences from controlled thermonuclear fusion to genetics. Many demands are placed on lasers as sources of light energy. The importance of low weight, compactness of the optical generator and the efficiency of energy conversion processes is emphasized.

Khariton, Y.

1984-08-01

201

On the detection of chemically peculiar stars using ?a photometry  

NASA Astrophysics Data System (ADS)

We have summarized all ? a measurements for galactic field stars (1474 objects) from the literature published over more than two decades. These measurements were, for the first time, compiled and homogeneously analyzed. The ? a intermediate band photometric system samples the depth of the 5200 Å flux depression by comparing the flux at the center with the adjacent regions with bandwidths of 110 Å to 230 Å. Because it was slightly modified over the last three decades, we checked for systematic trends for the different measurements but found no correlations whatsoever. The ? a photometric system is most suitable to detecting magnetic chemically peculiar (CP) stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. Furthermore, the groups of (metal-weak) ? Bootis, as well as classical Be/shell stars, can be successfully investigated. In addition, we also analyzed the behaviour of supergiants (luminosity class I and II). On the basis of apparent normal type objects, the correlation of the 3? significance limit and the percentage of positive detection for all groups was derived. We compared the capability of the ? a photometric system with the ? (V1 - G) and Z indices of the Geneva 7-color system to detect peculiar objects. Both photometric systems show the same efficiency for the detection of CP and ? Bootis stars, while the indices in the Geneva system are even more efficient at detecting Be/shell objects. On the basis of this statistical analysis it is possible to derive the incidence of CP stars in galactic open cluster and extragalactic systems including the former unknown bias of undetected objects. This is especially important in order to make a sound statistical analysis of the correlation between the occurrence of these objects and astrophysical parameters such as the age, metallicity, and strength of global, as well as local, magnetic fields.

Paunzen, E.; Stütz, Ch.; Maitzen, H. M.

2005-10-01

202

CHEMICAL PACEMAKERS  

PubMed Central

1. Iron spicules found in the brains of general paretic patients are formed from endogenous brain iron normally present in another form. This supports our earlier view that the µ value of 16,000 obtained in advanced paretics for alpha brain wave frequencies as a measure of cortical respiration comes about from the slowing of an iron catalyzed link in cortical respiration such as would result from the reduction of available cytochrome and its oxidase, thus making this step a chemical pacemaker. 2. To test the basic theory of chemical pacemakers, a study was made of the succinate-fumarate enzyme system containing succino-dehydrogenase and cytochrome-cytochrome oxidase acting sequentially. 3. The µ value for the unpoisoned system is 11,200 ± 200 calories. 4. According to theory, the addition of a critical amount of cyanide known to be a specific poison of the cytochrome-cytochrome oxidase system (and not of the dehydrogenase) should shift the µ cleanly to 16,000 calories, and it does. 5. According to theory, selenite, a specific poison for the dehydrogenase, should stop all respiration without shifting the µ. This also is found to be the case. 6. The theory also predicts that if the µ is shifted from 11,000 ± to 16,000 ± by cyanide, the subsequent addition of a critical amount of selenite should shift the µ back again to 11,000 ± calories, and this is found to occur. 7. It is concluded that approximately 11,000 calories is the energy of activation of the succino-dehydrogenase-catalyzed step and 16,000 calories is that for the cytochrome-cytochrome oxidase-catalyzed step. These two values are encountered more frequently than any others in physiological systems. It is to be recalled that a shift of µ for alpha brain wave frequencies from 11,000 to 16,000 calories occurs in the course of advancing syphilitic brain infection and is accompanied by a change in form of brain iron.

Hadidian, Zareh; Hoagland, Hudson

1939-01-01

203

Chemical Ecology: Chemical Communication in Nature.  

ERIC Educational Resources Information Center

|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)|

Wood, William F.

1983-01-01

204

Modern Chemical Technology, Guidebook for Chemical Technicians.  

ERIC Educational Resources Information Center

|This volume is a part of the ACS "Modern Chemical Technology" (ChemTeC) curriculum that is developed for chemical technicians. It is intended as a handbook that will be used throughout the instruction. Safety is stressed in eight of the ten chapters under the headings: safety in the chemical laboratory, personal protective equipment, fire safety…

Pecsok, Robert L.; Chapman, Kenneth

205

Microfluidic chemical reaction circuits  

DOEpatents

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.

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

2012-06-26

206

Algal Sensory Chemical Ecology  

Microsoft Academic Search

Sensory chemical ecology is the branch of chemical ecology that focuses on chemical communications between organisms and chemical\\u000a sensing of the environment by organisms. Algae are well known to have numerous physiological responses to variations in their\\u000a chemical environment, particularly with respect to nutrients (Lobban and Harrison 1994). However, with respect to environmental\\u000a sensing it is typical for “chemical ecology”

Charles D. Amsler

207

Nature's chemicals and synthetic chemicals: Comparative toxicology  

SciTech Connect

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.

Ames, B.N.; Profet, M.; Gold, L.S. (Univ. of California, Berkeley (USA))

1990-10-01

208

Tar sands and supergiant oil fields  

Microsoft Academic Search

Sixteen very large ''tar'' deposits are estimated to contain about 2,100 billion bbl of oil in place. This is nearly as much heavy oil as the world's total discovered recoverable oil reserves. The seven largest ''tar'' deposits of the world contain 98% of the world's heavy oil; that is, these seven heavy-oil deposits contain about as much oil in place

Demaison

1977-01-01

209

Red supergiants around Stephenson 2 (Negueruela+, 2012)  

NASA Astrophysics Data System (ADS)

Observations were carried out with the AutoFib2+WYFFOS (AF2) multi-object, wide-field, fibre spectrograph mounted on the Prime Focus of the 4.2m William Herschel Telescope (WHT), in La Palma, Spain. The observations were taken on the nights of 2009, June 5th (in service mode) and June 6th-7th (in visitor mode). (2 data files).

Negueruela, I.; Marco, A.; Gonzalez-Fernandez, C.; Jimenez-Esteban, F.; Clark, J. S.; Garcia, M.; Solano, E.

2013-01-01

210

Supergiant radial and nonradial pulsations. Lecture 10  

SciTech Connect

The stars that we consider here have luminosities above 10,000 solar luminosities and masses above 15 solar masses. We contact the 53 Per stars such as ..nu.. Ori, 10 Lac, and iota CMa at our lower luminosity limit, and at the most luminous limit, we have the famous stars eta Car, Cyg OB12, and P Cyg. Evolution tracks including a reasonable mass loss rate are given for 15, 30, 60, and 120 solar masses. It appears that our pulsators have masses less than 60 solar masses, but how do the most luminous stars observed survive mass loss. Do they have masses above 100 solar masses as indicated, or are these stars somehow superluminous due to their erratic mass loss behavior. Popper (1980) studying the masses in binary systems has never found one with a value greater than 27 solar masses.

Cox, A.N.

1983-03-14

211

Lean and Chemicals Toolkit.  

National Technical Information Service (NTIS)

This Lean and Chemicals Toolkit describes practical strategies for using Lean manufacturingthe production system developed by Toyotato reduce chemical wastes while improving the operational and environmental performance of manufacturing and industrial bus...

2009-01-01

212

The Chemical Equilibrium Problem.  

National Technical Information Service (NTIS)

It has long been known that the problem of determining the equilibrium composition of a solution of chemically reacting species could be formulated as a constrained minimum problem. Previous methods for solving the chemical equilibrium problem in this for...

J. H. Bigelow

1968-01-01

213

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 ...

214

Alternatives in Chemical Education  

ERIC Educational Resources Information Center

|Summarizes the educational objectives and strategies of the Chemical Technician Curriculum Project (Chem TeC), which has the primary objective of preparing a set of texts specifically for training chemical technicians. (PR)|

Pecsok, Robert L.

1971-01-01

215

Chemical Reactions (Netorials)  

NSDL National Science Digital Library

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

216

Physical vs Chemical Changes  

NSDL National Science Digital Library

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

217

Advanced Chemical Propulsion Study.  

National Technical Information Service (NTIS)

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 t...

G. Woodcock D. Byers L. A. Alexander A. Krebsbach

2004-01-01

218

Children and Dairy Chemicals  

MedlinePLUS

Children & Dairy Chemicals Chemicals used to clean dairy facilities and equipment, especially dairy pipeline cleaners, pose a special risk for children. Rapid medical assessment and treatment is critical in preventing long ...

219

Chemical Structural Aging Effects.  

National Technical Information Service (NTIS)

This program is determining the individual chemical rate processes that govern the aging of ANB-3066 propellant, and it is attempting to establish the effect of chemical (compositional) changes upon the system's mechanical response to enable better utiliz...

G. E. Myers A. B. Tipton

1972-01-01

220

Physical and Chemical Change  

NSDL National Science Digital Library

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

Wood, Mr.

2010-11-15

221

Chemical Synthesis Database  

NSDL National Science Digital Library

This database provides information on thousands of chemical compounds, including synthesis references and physical properties. The database is searchable by keyword and browseable by journal title. For each compound, the information includes molecular formula and weight, Chemical Abstracts Service (CAS) numbers, International Chemical Identifier (InChIKey), and Simplified Molecular Input Line Entry System (SMILES) notation. There is also information on synonyms, physical properties (boiling and melting points, density), an illustration of chemical structure, spectral data, and links to additional data.

222

Chemical of the Week  

NSDL National Science Digital Library

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

Shakhashiri, Bassam Z.

1997-01-01

223

The elusive chemical potential  

NSDL National Science Digital Library

The author offers some qualitative understanding of the chemical potential, a topic that students invariably find difficult. Three "meanings" for the chemical potential are stated and then supported by analytical development. Two substantial applications â depression of the melting point and batteries â illustrate the chemical potential in action. The origin of the term "chemical potential" has its surprises, and a sketch of the history is given.variable particle number.

Baierlein, Ralph

2011-08-31

224

Principles of Chemical Programming  

Microsoft Academic Search

The chemical reaction metaphor describes computation in terms of a chemical solu- tion in which molecules interact freely according to reaction rules. Chemical models use the multiset as their basic data structure. Computation proceeds by rewritings of the multiset which consume elements according to reaction conditions and pro- duce new elements according to specific transformation rules. Since the introduction of

Jean-pierre Banâtre; Pascal Fradet; Yann Radenac

2005-01-01

225

Principles of Chemical Programming  

Microsoft Academic Search

The chemical reaction metaphor describes computation in terms of a chemical solu- tion in which molecules interact freely according to reaction rules. Chemical models use the multiset as their basic data structure. Computation proceeds by rewritings of the multiset which consume elements according to reaction conditions and pro- duce new elements according to specic transformation rules. Since the introduction of

Jean-Pierre Ban; Pascal Fradet; Yann Radenac; Campus de Beaulieu

2004-01-01

226

Biological and Chemical Security  

Microsoft Academic Search

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.

Fitch

2002-01-01

227

Toxicology and Chemical Safety.  

ERIC Educational Resources Information Center

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)

Hall, Stephen K.

1983-01-01

228

Chemical Plume Source Localization  

Microsoft Academic Search

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

Shuo Pang; Jay A. Farrell

2006-01-01

229

Chemical warfare agents  

Microsoft Academic Search

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

S. Chauhan; R. D’Cruz; S. Faruqi; K. K. Singh; S. Varma; M. Singh; V. Karthik

2008-01-01

230

Toxicology and Chemical Safety.  

ERIC Educational Resources Information Center

|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)|

Hall, Stephen K.

1983-01-01

231

More on Chemical Changes  

NSDL National Science Digital Library

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

232

Chemical etching of aluminium  

Microsoft Academic Search

Chemical etching is employed as micromachining manufacturing process to produce micron-size components. The process applies a strong chemical etchant solution to remove unwanted part in the workpiece material. It is basically a corrosion-controlled process. Chemical etching process has a long history and accepted one of the important nontraditional machining processes during the last half century. The method is widely applied

O. Çak?r

2008-01-01

233

Adaptability in Chemical Engineering.  

National Technical Information Service (NTIS)

The adaptability issue for chemical engineering (the ability of chemical engineers to be retrained to work in other fields and for those from other fields to be retrained for work in chemical engineering) will be discussed and illustrated in terms of (1) ...

J. S. Watson

1989-01-01

234

Make a Chemical Clock  

NSDL National Science Digital Library

This lesson for Grades 6-8 combines a short video with three experiments to observe and record chemical changes. The experiments use common household materials to demonstrate chemical reaction -- a change that leads to a transformation of one substance into another substance. In the 3rd experiment, there are two chemical reactions happening at the same time. Through careful observation, learners see that the 3rd reaction represents a "chemical clock", because the time it takes the chemicals to react happens very predictably, like a regular clock. Talking Science is part of National Public Radio's Science Friday initiative.

2011-08-18

235

Toxic Chemical System (TCS)  

SciTech Connect

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.

Del Gandio, P.

1994-09-01

236

Miniature chemical measurement systems  

SciTech Connect

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

Ramsey, J.M.

1996-12-31

237

Chemical warfare agents  

Microsoft Academic Search

\\u000a Chemical warfare agents are compounds of different chemical structures. Simple molecules such as chlorine as well as complex\\u000a structures such as ricin belong to this group. Nerve agents, vesicants, incapacitating agents, blood agents, lung-damaging\\u000a agents, riot-control agents and several toxins are among chemical warfare agents. Although the use of these compounds is strictly\\u000a prohibited, the possible misuse by terrorist groups

Kamil Ku?a; Miroslav Pohanka

238

Physical and Chemical Changes  

NSDL National Science Digital Library

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

Holly, Mrs.

2010-11-15

239

310 Facility chemical specifications  

SciTech Connect

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.

Hagerty, K.J.

1997-05-21

240

RFE Chemical Taxonomy  

Center for Food Safety and Applied Nutrition (CFSAN)

... In chemical taxonomic identification ("chemotaxonomy") the comparison of characteristic gel banding patterns from biochemical analyses are used ... More results from www.fda.gov/food/foodscienceresearch/rfe

241

Apparatus for chemical synthesis  

SciTech Connect

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.

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

2011-05-10

242

Ionospheric chemical releases  

SciTech Connect

Ionospheric plasma density irregularities can be produced by chemical releases into the upper atmosphere. F-region plasma modification occurs by (1) chemically enhancing the electron number density, (2) chemically reducing the electron population, or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) determine the effectiveness of ionospheric chemical releases in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density. Subsequent processes, however, can lead to enhanced transport in chemically modified regions. Ionospheric modification by chemical releases excites artificial enhancements in airglow intensities by exothermic chemical reactions between the newly created plasma species. Numerical models have been developed to describe the creation and evolution of large scale (>l km) density irregularities and airglow clouds generated by artificial means. Experimental data compares favorably with these models. In general, we find that chemical releases produce transient, large amplitude perturbations in electron density which can evolve into fine scale irregularities via nonlinear transport processes.

Bernhardt, P.A.; Scales, W.A.

1990-10-01

243

Predicting Chemical Toxicity Effects Based on Chemical-Chemical Interactions  

PubMed Central

Toxicity is a major contributor to high attrition rates of new chemical entities in drug discoveries. In this study, an order-classifier was built to predict a series of toxic effects based on data concerning chemical-chemical interactions under the assumption that interactive compounds are more likely to share similar toxicity profiles. According to their interaction confidence scores, the order from the most likely toxicity to the least was obtained for each compound. Ten test groups, each of them containing one training dataset and one test dataset, were constructed from a benchmark dataset consisting of 17,233 compounds. By a Jackknife test on each of these test groups, the 1st order prediction accuracies of the training dataset and the test dataset were all approximately 79.50%, substantially higher than the rate of 25.43% achieved by random guesses. Encouraged by the promising results, we expect that our method will become a useful tool in screening out drugs with high toxicity.

Zhang, Jian; Feng, Kai-Rui; Zheng, Ming-Yue; Cai, Yu-Dong

2013-01-01

244

CHEMICAL CATEGORIES IN EPA'S NEW CHEMICALS PROGRAM  

EPA Science Inventory

Under section 5 of the Toxic Substances Control Act (TSCA),any person who intends to manufacture or import a new chemical substance, or mixture containing such a substance, in the United States for commercial purposes must submit a premanufacture notice (PMN) to the Environmental...

245

Chemical Dynamics Special Feature: Chemical reaction dynamics  

Microsoft Academic Search

Understanding the motions of the constituent atoms in reacting molecules lies at the heart of chemistry and is the central focus of chemical reaction dynamics. The most detailed questions one can ask are about the evolution of molecules prepared in a single quantum state to products in individual states, and both calculations and experiments are providing such detailed understanding of

F. Fleming Crim

2008-01-01

246

Biomass, Chemicals from  

SciTech Connect

This chapter describes the use and potential use of biomass resources for chemical production as a means to displace petroleum use. Therefore, the scope of the discussion is limited to large scale, commodity chemical products that can have an impact on the energy market by displacing petroleum conversion to chemical products. This article does not address in detail specialty chemical products whose limited market would have minimal impact on energy markets; nor does it describe in detail the use of biomass for material products such as cellulosic fiber for paper or lignocellulosic material for construction materials. The use of biomass for production of a vast array of specialty chemicals based on unique biochemical structures is another part of the overall concept of a sustainable economy, but is outside the scope of this article. Chemical production from biomass is an energy issue in that biomass-derived chemicals can result in a significant impact on the petroleum requirement for petrochemicals used in modern society. Petroleum thus displaced is available for use in the energy market. Petroleum utilization for chemicals production is reported at 14% of the petroleum market in the United States. Displacement of a significant fraction of this chemical synthesis from petroleum can provide an important impact on the overall market. In 1998 the U.S. Department of Energy stated as its goal the production of at least 10% of the basic chemical building blocks from plant-derived renewables by the year 2020 (a five-fold increase) and 50% by 2050 (another five-fold increase). In the long run, utilization of renewable carbon sources for the chemical requirements of society is the only option as fossil sources become more scarce.

Elliott, Douglas C.

2004-03-15

247

Access to Chemical Works  

Microsoft Academic Search

STUDENTS of chemistry so often complain of the extreme difficulty of obtaining access to chemical works that it may be well to bear in mind that the universities and technical schools of the United Kingdom have perhaps a remedy for what is a serious obstacle to a proper study of chemistry. The amount of chemicals now consumed in educational laboratories

Chemist

1908-01-01

248

Recognizing Chemical Hazards Module  

NSDL National Science Digital Library

The Center for the Advancement of Process Technology presents this free sample module on recognizing chemical hazards. It focuses on chemical hazards specific to process industries, and their impact on safety, health and the environment. The material also introduces the purpose and components of an MSDS.

2013-01-09

249

Chemicals in Everyday Life.  

ERIC Educational Resources Information Center

|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)|

Seymour, Raymond B.

1987-01-01

250

Fundamentals of Chemical Processes.  

ERIC Educational Resources Information Center

|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.…

Moser, William R.

1985-01-01

251

CHEMICAL PROCESSES IN SOILS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

252

Chemical Reaction Problem Solving.  

ERIC Educational Resources Information Center

|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…

Veal, William

1999-01-01

253

The Chemical Abstract Machine  

Microsoft Academic Search

We introduce a new kind of abstract machine based on the chemical metaphor used in the ? language of Banâtre & al. States of a machine are chemical solutions where floating molecules can interact according to reaction rules. Solutions can be stratified by encapsulating subsolutions within membranes that force reactions to occur locally. We illustrate the use of this model

Gérard Berry; Gérard Boudol

1990-01-01

254

Chemical Kinetics: Isolation Method  

NSDL National Science Digital Library

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

Blauch, David N.

255

Microorganisms and Chemical Pollution  

ERIC Educational Resources Information Center

|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…

Alexander, M.

1973-01-01

256

Great Lakes: Chemical Monitoring  

ERIC Educational Resources Information Center

|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)|

Delfino, Joseph J.

1976-01-01

257

Chemical Plant Security.  

National Technical Information Service (NTIS)

The potential harm to public health and the environment from a sudden release of hazardous chemicals has long concerned the U.S. Congress. This report reviews requirements that aim to reduce risks to the general public of exposure to hazardous chemicals a...

L. J. Schierow

2003-01-01

258

Identification of chemical compounds  

Microsoft Academic Search

We consider chemical identification as a process of setting up, testing, and screening of hypotheses, and review principles, techniques, and errors of identification. We also trace the relations between qualitative analysis and metrology and outline the range of known chemical compounds that are candidates for identification in general. We differentiate between methods for confirming identity and those for identifying unknowns,

Boris L. Milman

2005-01-01

259

Chemical profiles of switchgrass  

Microsoft Academic Search

Chemical analysis studies were conducted for four populations of switchgrass (Alamo, Kanlow, GA993, and GA992), Panicum virgatum L., which were partitioned into leaves, internodes, and nodes. The variations in carbohydrate compositions, lignin and extractives content, higher heating value (HHV), and the syringyl:guaiacyl ratio of switchgrass were determined. The experimental results indicated that bulk chemical profiles for the four populations of

Zhoujian Hu; Robert Sykes; Mark F. Davis; E. Charles Brummer; Arthur J. Ragauskas

2010-01-01

260

Chemical Encapsulation and Distribution.  

National Technical Information Service (NTIS)

A method is presented of coating chemicals that are used in the control of insects which protects the chemicals from biodegradation and improves their distribution in insect-containing bodies of water. A fat is mixed with an appropriate solvent, surfactan...

L. J. Goldberg

1975-01-01

261

Chemical Agent Detector Kits.  

National Technical Information Service (NTIS)

TOP 8-2-555 establishes general procedures and guidance for determining the technical performance and safety aspects of chemical agent detector kits that are designed to detect the presence of chemical agents in the atmosphere, on the surfaces of various ...

1989-01-01

262

Chemical and Physical Changes  

NSDL National Science Digital Library

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

263

Difficult Decisions: Chemical Warfare.  

ERIC Educational Resources Information Center

|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)|

Slesnick, Irwin L.; Miller, John A.

1988-01-01

264

Nonadiabatic chemical reactions  

Microsoft Academic Search

A mixed quantum-classical approach where the environment is treated classically and the reactive degrees of freedom are considered to be quantum mechanical can be used to describe many chemical reactions, such as proton and electron transfer processes. We present reactive flux correlation function expressions for the rate constants of nonadiabatic chemical reactions occurring in quantum-classical systems. By means of a

Alessandro Sergi; Raymond Kapral

2005-01-01

265

Chemical Biology Consortium Agreement  

Cancer.gov

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

266

Forward chemical genetic screening.  

PubMed

Chemical genetics utilizes small molecules to perturb biological processes. Unlike conventional genetics methods, which involve the alteration of genetic information mostly with lasting effects, chemical genetics allows temporary and reversible alterations of biological processes. Furthermore, it enables the alteration of biological processes in a dose-dependent manner, providing an advantage over conventional genetics.In the present chapter, the general procedures of forward chemical genetic screening are described. Forward chemical genetic screening can be performed in three steps. The first step involves the identification of small molecules that induce phenotypic or physiological changes in a biological system from a chemical library. In the second step, cellular targets that interact with the isolated chemical, which are mostly proteins, are identified. Although several methods can be applied in the second step, the most common one is affinity pull-down assay using a target protein that binds to the isolated compound. However, affinity pull-down of a target protein is a formidable barrier in forward chemical genetics. We introduced a tagged chemical library approach that significantly facilitates the identification of target proteins. The third step consists of the validation of the target protein, which should include the assessment of target specificity. This step is critical because small molecules often show pleiotropic effects due to low specificity. The specificity test may include a competition assay using cold competitors and a genetic study using mutants or transgenic lines modified for the cellular target. PMID:24057378

Choi, Hyunmo; Kim, Jun-Young; Chang, Young Tae; Nam, Hong Gil

2014-01-01

267

Combination chemical genetics  

PubMed Central

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

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

2009-01-01

268

Tortuous path chemical preconcentrator  

SciTech Connect

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.

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

2010-09-21

269

Chemical recognition software  

SciTech Connect

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.

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

1994-12-01

270

Reversible Chemical Kinetics Model  

NSDL National Science Digital Library

The Reversible Chemical Kinetics Model illustrates the time evolution of a reversible chemical reaction, from a given set of initial reactants concentration until chemical equilibrium is reached. The concentrations are plotted against time and the respective numerical values are periodically displayed at the data Table. As chemical equilibrium is attained, the concentrations become constant, the reaction quotient (Q) equalizes the equilibrium constant and Gibbs's energy change (G/RT) approaches zero. The Reversible Chemical Kinetics Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Fernandes, Fernando S.

2012-10-20

271

Chemical Biology is.....  

PubMed Central

Chemical Biology is a relatively new field, and as such is not yet simply or succinctly defined. It includes such a wide range of fundamental problems that this commentary could only include just a few snapshots of potential areas of interest. Overarching themes and selected recent successes and ideas in chemical biology are described to illustrate broadly the scope of the field, but should not be taken as exhaustive. The Chemical Biology Section of Chemistry Central Journal is pleased to receive manuscripts describing research into all and any aspects of the subject.

Ostler, Elizabeth L

2007-01-01

272

Chemical warfare agents.  

PubMed

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

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

2010-07-01

273

Chemical warfare agents  

PubMed Central

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.

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

2010-01-01

274

Selecting chemical treatment programs  

SciTech Connect

Many process equipment performance and reliability problems can be solved economically by the proper selection and application of chemical treatment programs. It is important to choose an experienced chemical vendor and to work closely with the vendor to develop a good chemical treatment program. This requires devoting sufficient manpower to ensure that the treatment program development is thorough and timely. After the treatment program is installed, the system operation and performance should be routinely monitored to ensure that expected benefits are achieved and unexpected problems do not develop.

Miller, J.E. (TOSCO Corp., Avon Refinery, Martinez, CA (US))

1988-09-01

275

Chemical Handler's Manual: A Guide to Chemical Control Regulations.  

National Technical Information Service (NTIS)

The Drug Enforcement Administration (DEA) is pleased to provide the Chemical Handler's Manual to assist you in understanding the provisions of the chemical control laws and their implementing regulations. These laws, including the Chemical Diversion and T...

2002-01-01

276

CHEMLAB: Chemical Modeling Laboratory.  

National Technical Information Service (NTIS)

CHEMLAB, the Chemical Modeling Laboratory, is the third generation of the CAMSEQ series of molecular processing programs. CHEMLAB performs a variety of structure calculations on user-defined molecules. Conformational Analysis, Quantum Mechanical calculati...

1983-01-01

277

A bionics chemical synapse.  

PubMed

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 ?-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 ?W. The total chip area is 3 mm(2) in 0.35-?m AMS CMOS technology. PMID:23853329

Thanapitak, Surachoke; Toumazou, Christofer

2013-06-01

278

Chemical modification of wood  

Treesearch

Source: Handbook of wood chemistry and wood composites. ... deterioration, wood chemistry, chemical reactions, dimensional stability, modified wood ... this page and attach it to the printout of the article, to retain the full citation information .

279

Chemical Thermal Desorption System.  

National Technical Information Service (NTIS)

A field portable chemical thermal desorption system. The system comprises a desorption tube, an injection needle operatively connected to the desorption tube, a needle valve operatively connected to the injection needle, a heater operatively connected to ...

A. Alcaraz C. Koester J. D. Eckels

2004-01-01

280

BBB - Brevetoxin Chemical Structure  

Center for Food Safety and Applied Nutrition (CFSAN)

... Print; Share; E-mail. Home; Food; Foodborne Illness & Contaminants; Causes of Foodborne Illness: Bad Bug ... BBB - Brevetoxin Chemical Structure. ... More results from www.fda.gov/food/foodborneillnesscontaminants/causesofillnessbadbugbook

281

Superfund Chemical Data Matrix.  

National Technical Information Service (NTIS)

The Superfund Chemical Data Matrix (SCDM) is a source for factor values and benchmark values applied when evaluating potential National Priority List (NPL) sites using the Hazard Ranking System (HRS). The HRS assigns factor values for toxicity, gas migrat...

1994-01-01

282

Chemical Principles Exemplified  

ERIC Educational Resources Information Center

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)

Plumb, Robert C.

1972-01-01

283

Drug & Chemical Residues Methods  

Center for Food Safety and Applied Nutrition (CFSAN)

Procedures preferred by analysts in FDA laboratories for the detection in food and cosmetic products of drug and chemical residues. More results from www.fda.gov/food/foodscienceresearch/laboratorymethods

284

Enhanced Chemical Cleaning  

ScienceCinema

Renee Spires, Project Manager at Savannah River Remediation, opens Session 3 (Accelerated Waste Retrieval and Closure: Key Technologies) at the 2010 EM Waste Processing Technical Exchange with a talk on enhanced chemical cleaning.

285

Sawmill chemicals and carcinogenesis.  

PubMed Central

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.

Huff, J

2001-01-01

286

Chemical and Thermal Analysis.  

National Technical Information Service (NTIS)

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 bo...

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

1996-01-01

287

Legendary Chemical Aphrodisiacs.  

ERIC Educational Resources Information Center

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

Waddell, Thomas G.; And Others

1980-01-01

288

KEMGAM: A Chemical Adventure.  

ERIC Educational Resources Information Center

|Describes two computer programs in which students select chemical substances and amounts for use on an imaginary trip. Written in BASIC, the 400-statement program is suitable for use on microcomputers. (SK)|

Carman, Richard T.

1981-01-01

289

Safer Science: Chemical Storage  

NSDL National Science Digital Library

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

Roy, Ken

2009-10-01

290

Crop Protection Chemical Safety  

MedlinePLUS

... use of the chemical; its proper handling, safe storage and first aid information. • Obtain Material Safety Data ... sure to keep a set separate from the storage area. • Have on hand and wear the personal ...

291

Chemical burn or reaction  

MedlinePLUS

... the skin has come in contact with the toxic substance Rash , blisters , burns on the skin Unconsciousness ... locked cabinet. Avoid mixing different products that contain toxic chemicals such as ammonia and bleach. The mixture ...

292

Chemical Processing of Glasses.  

National Technical Information Service (NTIS)

The development of chemical processing methods for the fabrication of glass and ceramic shapes for photonic applications is frequently Edisonian in nature. In Part, this is because the numerous variables that must be optimized to obtain a given material w...

R. M. Laine

1992-01-01

293

Enhanced Chemical Cleaning  

SciTech Connect

Renee Spires, Project Manager at Savannah River Remediation, opens Session 3 (Accelerated Waste Retrieval and Closure: Key Technologies) at the 2010 EM Waste Processing Technical Exchange with a talk on enhanced chemical cleaning.

Spires, Renee H.

2010-11-01

294

Chemical Principles Exemplified  

ERIC Educational Resources Information Center

|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)|

Plumb, Robert C.

1972-01-01

295

Chemical Bonding Technology.  

National Technical Information Service (NTIS)

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 st...

E. Plueddemann

1986-01-01

296

Journal of Chemical Education  

NSDL National Science Digital Library

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

2007-02-13

297

Rates of Chemical Weathering  

NSDL National Science Digital Library

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

Passow, Michael

298

Bulk chemicals from biomass  

Microsoft Academic Search

Given the current robust forces driving sustainable production, and available biomass conversion technologies, biomass-based routes are expected to make a significant impact on the production of bulk chemicals within 10 years, and a huge impact within 20-30 years. In the Port of Rotterdam there is a clear short-term (0-10 year) substitution potential of 10-15 % of fossil oil-based bulk chemicals

Jacco van Haveren; Elinor L. Scott; Johan Sanders

2008-01-01

299

Tracking toxic chemicals  

NASA Astrophysics Data System (ADS)

A new report tracking industrial pollution in North America indicates some good news, in terms of downward trends in the release and transfer of these substances.The July report, which tracks 165 chemicals released in the United States and Canada, shows that the total amount of 3.2 million tonnes of chemical releases and transfers from industrial facilities tracked by the North American Commission for Environmental Cooperation (CEC) decreased by 2% overall from 1995 to 1998.

Showstack, Randy

300

Environmental/chemical thesaurus  

SciTech Connect

The Environmental/Chemical Thesaurus approaches scientific language control problems from a multidisciplinary view. The Environmental/Biomedical Terminology Index (EBTI) was used as a base for the present thesaurus. The Environmental/Chemical Thesaurus, funded by the Environmental Protection Agency, used as its source of new terms those major terms found in 13 Environmental Protection Agency data bases. The scope of this thesaurus includes not only environmental and biomedical sciences, but also the physical sciences with emphasis placed on chemistry. Specific chemical compounds are not included; only classes of chemicals are given. To adhere to this level of classification, drugs and pesticides are identified by class rather than by specific chemical name. An attempt was also made to expand the areas of sociology and economics. Terminology dealing with law, demography, and geography was expanded. Proper names of languages and races were excluded. Geographic terms were expanded to include proper names for oceans, continents, major lakes, rivers, and islands. Political divisions were added to allow for proper names of countries and states. With such a broad scope, terminology for specific sciences does not provide for indexing to the lowest levels in plant, animal, or chemical classifications.

Shriner, C.R.; Dailey, N.S.; Jordan, A.C.; Miller, K.C.; Owens, E.T.; Rickert, L.W.

1978-06-01

301

Chemical cleaning, decontamination and corrosion.  

National Technical Information Service (NTIS)

Chemical cleaning of process equipments and pipings in chemical/petrochemical industries is necessitated for improving operation, for preventing premature failures and for avoiding contamination. In developing a chemical formulation for cleaning equipment...

H. S. Gadiyar Das Chintamani K. B. Gaonkar

1991-01-01

302

Hazardous chemicals detection experiment  

NASA Astrophysics Data System (ADS)

An experiment involving the production and measurement of chemical vapors released from two volatile liquid solvents and a toxic gas was conducted on December 9, 1992 at a remote site near Sacramento, California. During this experiment, measured quantities of liquid diethyl ether and acetone and hydrogen chloride gas were released under controlled conditions inside a mobile-home-type structure. Vapor concentrations of the two solvents and the gas were measured both inside and outside the structure with a variety of techniques. Measurement equipment included a Bruel & Kjaer Type 1302 multi-gas monitor, Miran Foxboro 1BX portable ambient air analyzer, and Microtip photoionization detectors. Supporting meteorology data was also collected. Chemical vapor and meteorological measurements have been correlated and present a limited understanding of plume dynamics for this particular release scenario and difficult weather conditions. These experiments were carried out under high- humidity conditions just after heavy rain. The data has been plotted to show the concentration dispersion over the period of chemical vapor presence for the known release quantities and exhaust rates. Typical concentrations measured were less than 1 ppm for diethyl ether and HCL and from 0.5 to 5 ppm for acetone at a distance of ten to twenty meters from the release point. The results of this experiment provide a quantitative description of low-concentration hazardous chemical releases that can be used to validate chemical plume models as well as determine the necessity, viability, and sensitivity of remote-sensing detection concepts.

Carlson, Rowena M.; Bunney, Laura; Williams, Donald N.

1994-03-01

303

Multiple chemical interactions  

SciTech Connect

One of the most complicated aspects of environmental health risk assessment is the evaluation and estimation of risk from exposures to multiple contaminants. While such multiple exposures are the norm rather than the exception, the nature of the calculational tools and models used to estimate risk have generally precluded any quantitative characterization of such risks. Thus, Calabrese's work is a much needed synthesis of knowledge on multiple chemical interactions. The work opens with a review of the historical basis and theoretical foundations of chemical interactions. The author then provides a conceptual framework for evaluating chemical interactions. Following the arguments of Rothman in the early 1970s, Calabrese identifies four contexts within which the concepts of interaction must be discussed: statistical, biological, public health, and individual decision-making. Calabrese next presents a concise but particulate set of definitions of the statistical and biochemical terminology important in studying chemical interactions. On this foundation, he then presents an expert and detailed discussion of the statistical methods and approaches which may be used to quantitatively analyze interactive effects. This section is replete with formulas from both statistics and calculus, although even then the most complicated are clearly explained. The remaining half of the book then looks at interactive effects of specific compounds and classes of compounds and in inducing specific types of health effects. Although much of the information presented in this text is not new, compilation of this chemical-specific information with the treatise on analytical approaches is a new and much needed addition to literature.

Calabrese, E.J.

1991-01-01

304

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

NASA Astrophysics Data System (ADS)

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 slight underabundance in O/H; ii) an outer shell very intense in [OIII]?5007 Å corresponding to the main sequence bubble broken up as a consequence of the collision between supergiant and WR shells. Nitrogen and oxygen do not appear enhanced here, but helium appears enriched; iii) and finally it includes an external and faint shell that surrounds the whole nebula like a thin skin representing the early interaction between the winds from the main sequence star with the ISM for which typical circumstellar abundances are derived. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Table 3 is available in electronic form at http://www.aanda.org

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

2012-05-01

305

Chemical debridement of burns.  

PubMed

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 Paraenzyme(21) and Travase.(39,48) It is possible that the short term use of systemic antibiotics begun just before and continued during, and for a short time after, the rapid chemical debridement may prove useful for the prevention of infection, as appears to be the case for abdominal operations of the clean-contaminated and contaminated types. PMID:4606330

Levenson, S M; Kan, D; Gruber, C; Crowley, L V; Lent, R; Watford, A; Seifter, E

1974-10-01

306

Chemical induced intracellular hyperthermia  

US Patent & Trademark Office Database

An invention relating to therapeutic pharmacological agents and methods to chemically induce intracellular hyperthermia and/or free radicals for the diagnosis and treatment of infections, malignancy and other medical conditions. The invention relates to a process and composition for the diagnosis or killing of cancer cells and inactivation of susceptible bacterial, parasitic, fungal, and viral pathogens by chemically generating heat, and/or free radicals and/or hyperthermia-inducible immunogenic determinants by using mitochondrial uncoupling agents, especially 2,4 dinitrophenol and, their conjugates, either alone or in combination with other drugs, hormones, cytokines and radiation.

2009-12-22

307

Chemical oceanography dissertations presented  

NASA Astrophysics Data System (ADS)

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.

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

308

Holographic chemical vapor sensor  

NASA Astrophysics Data System (ADS)

A holographic interferometer senses vapor-induced optical path length changes in polymer or other chemically sensitive films. The interferometer is inherently sensitive to changes in chemical vapor content, self-compensates for drifts, and accommodates a large array of sensor elements. A sniff-locked-loop synchronous detection method takes advantage of the interferometer's rapid response to achieve vapor concentration sensitivity in the parts-per-billion (ppb, parts in 10^9) range. We demonstrate, for example, 40 ppb sensitivity to ethyl alcohol using poly(N-vinyl pyrrolidone) with a measurement time of 5 s.

Ye, Hongke; Nilsen, Oyvind; Bright, Victor M.; Anderson, Dana Z.

2005-06-01

309

Chemical profiles of switchgrass.  

PubMed

Chemical analysis studies were conducted for four populations of switchgrass (Alamo, Kanlow, GA993, and GA992), Panicum virgatum L., which were partitioned into leaves, internodes, and nodes. The variations in carbohydrate compositions, lignin and extractives content, higher heating value (HHV), and the syringyl:guaiacyl ratio of switchgrass were determined. The experimental results indicated that bulk chemical profiles for the four populations of switchgrass were comparable. However, the results from three morphological components of switchgrass, leaves, internodes and nodes, provided a significant diversity among the analytical results studied. PMID:20074945

Hu, Zhoujian; Sykes, Robert; Davis, Mark F; Charles Brummer, E; Ragauskas, Arthur J

2010-01-13

310

Molecular Mechanisms of Toxic Chemicals  

Microsoft Academic Search

Most human cancers are caused by toxic organic or inorganic chemicals. Environmental exposure allows these chemicals to enter the body and almost every body cell. Within the body cells, five multi-enzyme systems process these chemicals. The chemicals can be activated to their ultimate carcinogenic molecular structures (usually to free radicals) or they can generate free radicals from water molecules. As

Wayne E. Criss

2003-01-01

311

Laboratory Safety and Chemical Hazards.  

ERIC Educational Resources Information Center

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

Journal of Chemical Education, 1983

1983-01-01

312

Laboratory Safety and Chemical Hazards.  

ERIC Educational Resources Information Center

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

Journal of Chemical Education, 1983

1983-01-01

313

Journal of Chemical Education  

NSDL National Science Digital Library

The Journal of Chemical Education digital library provides a collection of chemistry related education resources online. Users may search or browse the online collection. Materials are available for a range of educational levels and on a variety of chemistry related topics.

2011-03-10

314

Chemical Principles Exemplified  

ERIC Educational Resources Information Center

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…

Plumb, Robert C.

1970-01-01

315

Chemical Composition of Mish \\  

Microsoft Academic Search

This study was conducted to evaluate the chemical composition of mish during storage. Ninety samples of mish were collected on the day of manufacture (day one) from three different dairy plants (DP1, DP2, DP3), transported to the laboratory of the Department of Dairy Production, Faculty of Animal Production in ice box and stored at 7 C for 28 days. Samples

Mohamed Osman Mohamed Abdalla; Somaia Zonnoon; Abdel Nabi Ahmed

2010-01-01

316

Proton Chemical Shifts  

NSDL National Science Digital Library

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

Reich, Hans J.

2007-11-16

317

Chemical Aspects of Dentistry.  

ERIC Educational Resources Information Center

|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,…

Helfman, Murry

1982-01-01

318

Prioritizing Industrial Chemical Hazards  

Microsoft Academic Search

This article describes the approach used to develop a prioritized list of toxic and hazardous industrial chemical hazards considered to pose substantial risk to deployed troops and military operations. The U.S. Army Center for Health Promotion and Preventive Medicine published the prioritized list in November 2003. The work was performed as part of a multinational military effort supported by Canada,

Veronique D. Hauschild; Gary M. Bratt

2005-01-01

319

Biological and chemical terrorism  

Microsoft Academic Search

Many different types of potential threats have been identified in the ongoing war against terrorism. Epidemiological threats are not software threats, but perhaps can be better referred to as “soft body” threats. This requires preparedness and response to various kinds of unconventional terrorism, especially biological, chemical, and radiological or nuclear.

Stephen S. Morse

2003-01-01

320

Making a Chemical Rainbow  

ERIC Educational Resources Information Center

|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…

Angelin, Marcus; Ramstrom, Olof

2010-01-01

321

Selective chemical stripping  

Microsoft Academic Search

At the end of the 80's, some of the large European airlines expressed a wish for paint systems with improved strippability on their aircraft, allowing the possibility to strip down to the primer without altering it, using 'mild' chemical strippers based on methylene chloride. These improvements were initially intended to reduce costs and stripping cycle times while facilitating rapid repainting,

Olivier Malavallon

1995-01-01

322

Chemically enabled nanostructure fabrication  

Microsoft Academic Search

The first part of the dissertation explored ways of chemically synthesizing new nanoparticles and biologically guided assembly of nanoparticle building blocks. Chapter two focuses on synthesizing three-layer composite magnetic nanoparticles with a gold shell which can be easily functionalized with other biomolecules. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding

Fengwei Huo

2009-01-01

323

Chemical calcium indicators  

Microsoft Academic Search

Our understanding of the underlying mechanisms of Ca2+ signaling as well as our appreciation for its ubiquitous role in cellular processes has been rapidly advanced, in large part, due to the development of fluorescent Ca2+ indicators. In this chapter, we discuss some of the most common chemical Ca2+ indicators that are widely used for the investigation of intracellular Ca2+ signaling.

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

2008-01-01

324

Mining Chemical Compounds  

Microsoft Academic Search

In this chapter we study the problem of classifying chemical compound datasets. We present a substructure-based classification algorithm that decouples the substructure discovery process from the classification model construction and uses frequent subgraph discovery algorithms to find all topological and geometric substructures present in the dataset. The advantage of this approach is that during classification model construction, all relevant substructures

Mukund Deshpande; Michihiro Kuramochi; George Karypis

2005-01-01

325

Chemical constituents of Asparagus  

PubMed Central

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

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

2010-01-01

326

Chemical control of flowering  

Microsoft Academic Search

The existence of flower-forming substances has a reasonably firm foundation, although none of the substances responsible have yet been isolated. The studies which have been performed on the alteration of flowering behaviour by the application of various chemical substances have helped to elucidate the internal mechanism of control of flowering to a marked degree. The purpose of this review is

S. Kolli

1969-01-01

327

Great Lakes: chemical monitoring  

Microsoft Academic Search

The article discusses a symposium sponsored by the 10th Great Lakes Regional Meeting of the American Chemical Society (ACS) that addressed various aspects of the theme ''Chemistry of the Great Lakes''. The symposium attempted to gather together environmental information produced by chemists, and included: watershed studies, involving investigation of the sources, transport, and fate of sterols in the Menomonee River;

Joseph J. Delfino

1976-01-01

328

Endocrine disrupting chemicals  

PubMed Central

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.

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

2011-01-01

329

Visionlearning: Chemical Bonding  

NSDL National Science Digital Library

This digital learning module provides an easily-understood overview of chemical bonding for users with little formal background in chemistry or physics. It explores ionic bonding through the example of sodium (an alkali metal) reacting with chlorine gas to produce common table salt. A concept simulation further illustrates the process.

Carpi, Anthony

2011-07-12

330

Tourniquet associated chemical burn  

PubMed Central

Chemical burn under pneumatic tourniquet is an iatrogenic preventable injury and is rarely reported in the literature. The two important mechanisms are maceration (friction) and wetness underneath the tourniquent. In this report, our experience with two illustrative patients who presented with iatrogenic tourniquet associated burn is described.

Yang, Jae-Hyuk; Lim, Hyungtae; Yoon, Jung-Ro; Jeong, Hyeon-Il

2012-01-01

331

Theory of Chemical Modeling  

Microsoft Academic Search

In order to deal with the complexity of natural systems simplified models are employed to illustrate the principal and regulatory factors controlling a chemical system. Following the aphorism of Albert Einstein: Everything should be made as simple as possible, but not simpler, models need not to be completely realistic to be useful (Stumm and Morgan 1996), but need to meet

Michael Kühn

2001-01-01

332

Rates of Chemical Reactions  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

1900-01-01

333

Chemicals from biomass feedstocks  

Microsoft Academic Search

This article shows how production of industrial chemicals from biomass is technically feasible, either as fractionated compounds by thermochemical conversion to synthesis gas or by fermentation. Emphasizes that a significant problem in using biomass feedstocks for fuels is the high cost of the assembled feedstock when compared to the value of the final fuel product. Presents typical costs of centrally

L. D. Clements; S. R. Beck; C. Heintz

1983-01-01

334

Chemical Sensing with Nanowires  

NASA Astrophysics Data System (ADS)

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.

Penner, Reginald M.

2012-07-01

335

Chemical Modification of Polysaccharides  

PubMed Central

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.

Cumpstey, Ian

2013-01-01

336

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.

337

Chemical oxygen generation.  

PubMed

While pressurized oxygen in tank form, as well as oxygen concentrators, are ubiquitous in civilian healthcare in developed countries for medical use, there are a number of settings where use of these oxygen delivery platforms is problematic. These settings include but are not limited to combat casualty care and healthcare provided in extreme rural environments in undeveloped countries. Furthermore, there are a number of settings where delivery of oxygen other than the pulmonary route to oxygenate tissues would be of value, including severe lung injury, airway obstruction, and others. This paper provides a brief overview of the previous and current attempts to utilize chemical oxygen production strategies to enhance systemic oxygenation. While promising, the routine use of chemically produced oxygen continues to pose significant engineering and physiologic challenges. PMID:23271828

Ward, Kevin R; Huvard, Gary S; McHugh, Mark; Mallepally, Rajender R; Imbruce, Richard

2013-01-01

338

Cooee bitumen: Chemical aging  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

339

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

ERIC Educational Resources Information Center

|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)|

Wright, Stephen W.

2002-01-01

340

Chemical emergency preparedness program: chemical profiles. Interim guidance  

SciTech Connect

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).

Not Available

1985-12-01

341

Modeling in chemical engineering  

Microsoft Academic Search

In its 90 year life what has chemical engineering (ChE) contributed to society? Firstly, we have invented and developed processes to create new materials, more gently and more efficiently, so as to make life easier for all.Secondly, ChE has changed our accepted concepts and our ways of thinking in science and technology. Here modeling stands out as the primary development.

Octave Levenspiel

2002-01-01

342

Chemical Communication in Crayfish  

Microsoft Academic Search

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

Thomas Breithaupt

343

Micromachined chemical jet dispenser  

SciTech Connect

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.

Swierkowski, S.; Ciarlo, D.

1996-05-13

344

Psychogenic chemical sensitivity  

Microsoft Academic Search

A middle-aged woman with a 10-year history of disability attributed to chemical sensitivities complained that exposure to specific fragrances immediately elicited seizures. Video-EEG monitoring was performed in a hospital neurodiagnostic laboratory during provocative challenge studies employing fragrances identified by the patient as reliably inducing symptoms. The baseline clinical EEG was normal. Immediately after each provocation with air deodorant and perfume,

Herman Staudenmayer; Ronald E Kramer

1999-01-01

345

Chemical measurements in Drosophila.  

PubMed

The fruit fly, Drosophila melanogaster, has been extensively used as a model organism in genetics research and has significantly contributed to understanding molecular, cellular and evolutionary aspects of human behavior. Recently, research has focused on developing analytical methods to obtain highly sensitive chemical quantification along with spatiotemporal information from Drosophila melanogaster. We review a number of these advances in capillary electrophoresis, high-performance liquid chromatography, mass spectrometry and technologies involving intact organisms, including in vivo electrochemistry. PMID:20161412

Makos, Monique A; Kuklinski, Nicholas J; Berglund, E Carina; Heien, Michael L; Ewing, Andrew G

2009-12-01

346

Chemical measurements in Drosophila  

PubMed Central

The fruit fly, Drosophila melanogaster, has been extensively used as a model organism in genetics research and has significantly contributed to understanding molecular, cellular and evolutionary aspects of human behavior. Recently, research has focused on developing analytical methods to obtain highly sensitive chemical quantification along with spatiotemporal information from Drosophila melanogaster. We review a number of these advances in capillary electrophoresis, high-performance liquid chromatography, mass spectrometry and technologies involving intact organisms, including in vivo electrochemistry.

Makos, Monique A.; Kuklinski, Nicholas J.; Berglund, E. Carina; Heien, Michael L.; Ewing, Andrew G.

2009-01-01

347

Chemical transformation of yeast.  

PubMed

Transformation of chemically competent yeast cells is a method for introducing exogenous DNA into living cells. Typically, the DNA is either a plasmid carrying an autonomous replication sequence that allows for propagation or a linear piece of DNA to be integrated into the genome. The DNA usually also carries a marker that allows for selection of successfully transformed cells by plating on the appropriate selective media. PMID:24011057

Bergkessel, Megan; Guthrie, Christine

2013-01-01

348

Environmental chemicals targeting thyroid.  

PubMed

Thyroid hormones (THs) are required for normal brain and somatic development and for the proper regulation of physiology in both children and adults. Thyroid function is controlled by the dynamic interrelationships between the hypothalamus, the pituitary and the thyroid. These dynamic relationships maintain circulating levels of THs within a narrow range under normal conditions. Normally, there is likely to be a tight relationship between changes in circulating levels of THs and changes in TH action in various target tissues. This relationship is maintained by tissue-level mechanisms that include TH metabolism and transport. Environmental chemicals that interfere with TH signaling mechanisms (Endocrine Disrupting Chemicals, EDCs) may produce adverse effects both in the individual and in a population. Because of the complex nature of the regulation of thyroid function and TH action, the consequences of EDC exposure is also likely to be complex and our ability to understand these effects as well as to screen for potential EDCs must consider this complexity. Specifically, if there are chemicals in the environment that directly interfere with TH action through their receptors but do not affect circulating TH levels, they would not be identified as thyroid toxicants by currently applied screening methods or by epidemiological studies. The goal of this review is therefore to identify the issues that must be clearly resolved before effective risk assessment can be performed. PMID:20363719

Zoeller, Thomas R

349

Chemical Industry Archives  

NSDL National Science Digital Library

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

2001-01-01

350

The Chemical Scorecard  

NSDL National Science Digital Library

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

1998-01-01

351

Miniature Chemical Sensor  

SciTech Connect

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.

Andrew C. R. Pipino

2004-12-13

352

Marine Pollution from Offshore Chemicals.  

National Technical Information Service (NTIS)

The report analyses the influencing impact on the marine environment caused by the various chemical effluents from the offshore drilling and production. The offshore chemicals used at the Statfjord and Ekofisk fields on the Norwegian Continental Shelf are...

O. Bjoerseth G. Halmoe R. Romslo T. Syvertsen

1986-01-01

353

CHEMICAL STORAGE: MYTHS VERSUS REALITY  

SciTech Connect

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.

Simmons, F

2007-03-19

354

Chemical Discovery as Belief Revision.  

National Technical Information Service (NTIS)

This paper describes STAHLp, a system that constructs componential models of chemical substances. STAHLp is a descendent of Zytkow and Simon's (1986) STAHL system, and both use chemical reactions and known componential models in order to construct new che...

D. Rose P. Langley

1986-01-01

355

Chemical Hazards to Human Reproduction.  

National Technical Information Service (NTIS)

This report is an evaluation and documentation of the current evidence for reproductive hazards of chemicals, an evaluation of the policy implications of the state of knowledge about chemical hazards to human reproduction, a review of occupational exposur...

1981-01-01

356

Chemical Control of Vampire Bats.  

National Technical Information Service (NTIS)

Two different chemical methods for reducing populations of vampire bat populations are described. Both methods are based on an anitcoagulant, diphenadione. The chemical is either injected into the rumen of cattle or applied directly to the back of vampire...

G. C. Mitchell R. J. Burns

1973-01-01

357

Ultrasensitive Detection of Chemical Substances.  

National Technical Information Service (NTIS)

Our proposal 'Ultrasensitive Detection of Chemical Substances' submitted to the Defense Advanced Research Projects Agency in September 1983, proposed the development of an ultrasensitive detection system for chemical agents of small molecular size. This s...

R. Dean

1984-01-01

358

Chemical Dosimetry of Ionizing Radiations.  

National Technical Information Service (NTIS)

This volume generalizes the theoretical and experimental material that has been accumulated during recent years in the field of chemical dosimetry. Attention is focused on the justification for the use of chemical-dosimetry methods to solve problems that ...

A. M. Kabakchi Y. I. Lavrentovich V. V. Penkovskii

1966-01-01

359

Explosive chemical emissions from landmines  

NASA Astrophysics Data System (ADS)

Chemical sensing for buried landmines is a complex phenomenon that includes mine chemical emissions, soil chemical transport/degradation, and detection at the ground surface. The technology to assess soil chemical transport has evolved and now provides a complex systems analysis capability using high fidelity computational simulation tools. Data requirements to evaluate a chemical sensing scenario include soil chemodynamic properties, micrometeorological conditions, and mine chemical emissions. Mine chemical emission tests were performed on four antipersonnel landmines using whole landmines in soil flux chambers. Soil flux chambers are simple containers that surround landmines with dry soil that act as an adsorbent. After a certain soak time, residue analysis of the soil provides the total chemical emission - a combination of both permeation and leakage. An evaluation of permeation differences into wet soil versus dry soil was also completed using thin polymer coupon sections.

Phelan, James M.; Barnett, James L.; Romero, Joseph V.; Kerr, Dayle R.; Griffin, Fawn A.

2003-09-01

360

LLNL Chemical Kinetics Modeling Group  

SciTech Connect

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.

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

2008-09-24

361

Physical and Chemical Changes Paper  

NSDL National Science Digital Library

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

Wall, Mr.

2008-10-28

362

Modern Chemical Technology, Volume 6.  

ERIC Educational Resources Information Center

|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,…

Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.

363

Graph kernels for chemical informatics  

Microsoft Academic Search

Increased availability of large repositories of chemical compounds is creating new challenges and opportunities for the application of machine learning methods to problems in computational chemistry and chemical informatics. Because chemical compounds are often represented by the graph of their covalent bonds, machine learning methods in this domain must be capable of processing graphical structures with variable size. Here we

Liva Ralaivola; Sanjay Joshua Swamidass; Hiroto Saigo; Pierre Baldi

2005-01-01

364

Stochastic Simulation of Chemical Kinetics  

Microsoft Academic Search

Stochastic chemical kinetics describes the time evolution of a well- stirred chemically reacting system in a way that takes into account the fact that molecules come in whole numbers and exhibit some degree of randomness in their dynamical behavior. Researchers are increasingly using this approach to chemical kinetics in the analysis of cellular systems in biology, where the small molecular

Daniel T. Gillespie

2007-01-01

365

Modern Chemical Technology, Volume 5.  

ERIC Educational Resources Information Center

|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…

Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.

366

Chemical Kinetics: Rate of Reaction  

NSDL National Science Digital Library

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

Blauch, David N.

367

Modern Chemical Technology, Volume 2.  

ERIC Educational Resources Information Center

This volume contains chapters 8 to 13 of the ACS "Modern Chemical Technology" (ChemTeC) curriculum material which is intended to prepare chemical technologists. The content is centered around the background needed to understand the structure of the atom, covalence, electrovalence, elements and compounds, liquids and solutions, and chemical

Pecsok, Robert L.; Chapman, Kenneth

368

Chemical ecology of bark beetles  

Microsoft Academic Search

Summary The purview of chemical ecology and the recent criticisms of improper application of theory to bark beetle phenomena is briefly discussed. Seven levels of research in chemical ecology are presented as well as their relationship to research on bark beetles. The biology and chemical ecology of several pest bark beetles from North America and Europe are discussed in regard

J. A. Byers

1989-01-01

369

Primary Teachers' Conceptions of "Chemical."  

ERIC Educational Resources Information Center

|Examines what primary teachers actually understand about the word 'chemical' and what they do to help young students arrive at a scientific conception of chemical. Indicates three main categories of teachers' views of a chemical and discusses the effects of a professional development course on this subject. (ASK)|

Hickey, Ruth; Schibeci, Renato A.

2000-01-01

370

Galactic Chemical Evolution & the Hot Star - H II Region Connection in NGC6822  

NASA Astrophysics Data System (ADS)

H II regions provide fundamental data about heavy element abundances that constrain galactic chemical evolution (GCE) models. We propose to use Spitzer/IRS to follow up on our Spitzer observations of M83 and M33 H II regions. We will measure S IV 10.5, Ne II 12.8, Ne III 15.6, S III 18.7, & H7-6 12.4 micron cospatially with IRS/SH. By measuring all the major ionic states of Ne and S in H II regions with an H line, there is a unique opportunity to estimate S3+/S++, Ne++/Ne+, Ne/H, S/H, & Ne/S ratios and test if they vary with galactocentric radius (R_G). The high Ne/S ratios we derived for M83 are likely upper limits due to our estimate of the S abundance not accounting for S+ or dust. The M33 H II regions have much lower metallicity and higher ionization, leading to a truer total S abundance & a Ne/S close to the Orion Nebula value 14. The H II regions in the nearby, dwarf irregular galaxy NGC6822 are both low metallicity (O/H ~3.5x lower than Solar) and high ionization, allowing a reliable derivation of gas-phase Ne/S. The solar Ne abundance is very controversial, with much evidence pointing to a higher Ne value than the current Ne/S~5. NGC6822 observations will test how robust and universal the ratio of ~14 is. Such a finding will place important constraints upon GCE models. Our derivation of ionic abundances from Spitzer data depends on nebular models, which rely on the spectral energy distribution (SED) which comes from stellar atmosphere models. From our M83 and M33 data, we derive / & / vs. / ratios for the various H II regions and compare with theoretical loci, which show a factor >10 spread in y at a given x. The data points best follow the trend of the loci using the supergiant SEDs of Pauldrach, who will compute a set of atmosphere models with metallicity similar to that of NGC6822. Data for a third galaxy with a very different history and gas content will further validate whether or not any SED set preferentially fits the nebular observations.

Rubin, Robert; Buckalew, Brent; Colgan, Sean; Dufour, Reginald; Erickson, Edwin; Haas, Michael; Janet, Simpson; Pauldrach, Adalbert

2007-05-01

371

Advanced Chemical Propulsion  

NASA Astrophysics Data System (ADS)

Improving the performance and reliability characteristics of chemical propulsion systems requires research and testing of higher-performance propellants, higher efficiency thrusters, cryogenics technology, lightweight components and advancements in propulsion system design and assessment. Propellants are being investigated to identify practical combinations with higher efficiencies and better thermal properties to reduce thermal control requirements. This includes combinations with modest increases, such as LOX-hydrazine, as well as a new evaluation of major improvements available from fluorine-bearing oxidizers. Practical ways of implementing cryogenic propulsion to further increase efficiency are also being studied. Some potential advances include small pump-fed engines, and improvements in cryocooler technology and tank pressure control. Gelled propellants will be tested to determine the practicality of letting propellants freeze at low environmental temperatures and thawing them only when required for use. The propellant tank is typically the single highest non-expendable mass in a chemical propulsion system. Lightweight tank designs, materials and methods of fabrication are being investigated. These are projected to offer a 45-50 percent decrease in tank mass, representing the potential inert system mass savings. Mission and systems analyses are being conducted to guide the technology research and set priorities for technology investment, based on estimated gains in payload and mission capabilities. This includes development of advanced assessment tools and analyses of specific missions selected from Science Missions' Directorate. The goal is to mature a suite of reliable advanced propulsion technologies that will promote more cost efficient missions through the reduction of interplanetary trip time, increased scientific payload mass fraction and longer on-station operations. This talk will review the Advanced Chemical technology development roadmap, current funded technology development work, future funding opportunities and results from on-going mission studies.

Alexander, L.

2004-11-01

372

Chemical Explosion Database  

NASA Astrophysics Data System (ADS)

A database containing information on chemical explosions, recorded and located by the International Data Center (IDC) of the CTBTO, should be established in the IDC prior to entry into force of the CTBT. Nearly all of the large chemical explosions occur in connection with mining activity. As a first step towards the establishment of this database, a survey of presumed mining areas where sufficiently large explosions are conducted has been done. This is dominated by the large coal mining areas like the Powder River (U.S.), Kuznetsk (Russia), Bowen (Australia) and Ekibastuz (Kazakhstan) basins. There are also several other smaller mining areas, in e.g. Scandinavia, Poland, Kazakhstan and Australia, with large enough explosions for detection. Events in the Reviewed Event Bulletin (REB) of the IDC that are located in or close to these mining areas, and which therefore are candidates for inclusion in the database, have been investigated. Comparison with a database of infrasound events has been done as many mining blasts generate strong infrasound signals and therefore also are included in the infrasound database. Currently there are 66 such REB events in 18 mining areas in the infrasound database. On a yearly basis several hundreds of events in mining areas have been recorded and included in the REB. Establishment of the database of chemical explosions requires confirmation and ground truth information from the States Parties regarding these events. For an explosion reported in the REB, the appropriate authority in whose country the explosion occurred is encouraged, on a voluntary basis, to seek out information on the explosion and communicate this information to the IDC.

Johansson, Peder; Brachet, Nicolas

2010-05-01

373

Radiation chemical synthesis  

SciTech Connect

The authors consider processes in radiation chemical synthesis which are being developed in various scientific-research organizations. The important advantages of radiation chlorination, viz. the lower temperature compared with the thermal method and the absence of dehydrochlorination products are discussed. The authors examine the liquid-phase chlorination of trifluorochloroethyltrichloromethyl ether to obtain the pentachloro-contining ether, trifluorodichloroethyltrichloromethyl ether. The authors discuss radiation synthesis processes that have be used formulated kinetic equations on which models have been based. It is concluded that the possibilities of preparative (micro- and low-tonnage) radiation synthesis are promising.

Zagoretz, P.A.; Poluetkov, V.A.; Shostenko, A.G.

1986-03-01

374

Chemical sensing flow probe  

DOEpatents

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.

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

1999-02-16

375

Chemical sensor system  

DOEpatents

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.

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

2002-01-01

376

Chemical and Biological Kinetics  

NASA Astrophysics Data System (ADS)

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.

Emanuel', N. M.

1981-10-01

377

Chemical toxins that cause seizures.  

PubMed

Seizurogenic chemicals include a variety of toxic agents, including chemical warfare agents, toxic industrial chemicals, and natural toxins. Chemical weapons such as sarin and VX, and pesticides such as parathion and carbaryl cause hyperstimulation of cholinergic receptors and an increase in excitatory neurotransmission. Glutamatergic hyperstimulation can occur after exposure to excitatory amino acid toxins such as the marine toxin domoic acid. Other pesticides such as lindane and strychnine do not affect excitatory neurotransmission directly, but rather, they block the inhibitory regulation of neurotransmission by antagonism of inhibitory GABA and glycine synapses. In this paper, chemicals that cause seizures by a variety of molecular mechanisms and pathways are discussed. PMID:23085523

Jett, David A

2012-10-18

378

a Submillimeter Chemical Sensor  

NASA Astrophysics Data System (ADS)

Rotational spectroscopy has been recognized a potentially powerful tool for chemical analysis since the very beginnings of the field. A typical rotational fingerprint consists of 10^5 resolvable spectral channels, leading to `absolute' specificity, even in complex mixtures. Furthermore, rotational spectroscopy requires very small amounts of sample with detection limits as low as picograms. Nevertheless, this technique has not yet been widely applied to analytical science because of the size, cost, and complexity of traditional spectrometers. A resurgence of interest in spectroscopic sensors has been fueled by increases in performance made possible by advances in laser systems and applications in medicine, environmental monitoring, and national security. Most of these new approaches make use of the optical/infrared spectral regions and their well established, but still rapidly evolving technology base. The submillimeter (SMM) spectral region, while much less well known, has also seen significant technological advances, allowing the design of powerful spectroscopic sensors. Using modern solid-state multiplier technology we have built a small bench top SMM spectrometer designed for use as a chemical sensor. This spectrometer includes a sample acquisition system including the vacuum equipment to provide the ideal pressures (1--10 mtorr) for SMM spectroscopy and a sorbent tube for analyte collection and preconcentration. The entire spectrometer, including power supplies, frequency synthesizers, a 1.2 m folded sample cell, and a computer for data analysis fits into a cubic foot box.

Neese, Christopher F.; Medvedev, Ivan R.; De Lucia, Frank C.; Plummer, Grant M.; Ball, Christopher D.; Frank, Aaron J.

2010-06-01

379

Early cosmic chemical evolution  

NASA Astrophysics Data System (ADS)

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.

Karlsson, T.

2008-12-01

380

Selective chemical stripping  

NASA Astrophysics Data System (ADS)

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

Malavallon, Olivier

1995-04-01

381

Chemical Reactions in DSMC  

SciTech Connect

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.

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

2011-05-20

382

Controlling toxic chemicals  

SciTech Connect

The use of pesticides in agriculture and the disposal of industrial chemical wastes constitute two major pathways by which people are inadvertently exposed to toxics. These practices release hundreds of millions of tons of potentially hazardous substances into the environment each year. In many ways the situation with industrial chemical waste parallels the predicament with pesticides: Not only are current practices contaminating the environment and creating health risks, but they are unsustainable over the long term. Strategies that reduce pesticide use in agriculture and minimize waste generation in industry offer cost-effective approaches to decreasing risks from toxics. Such strategies differ fundamentally from current practice and require new ways of thinking. The quick fixes of pesticide spraying and end-of-pipe pollution control are replaced with new production systems aimed at reconciling economic profits with environmental protection. Current efforts in integrated pest management and industrial waste reduction, although clearly promising, only hint at their long-term potential for detoxifying the environment.

Postel, S.

1988-01-01

383

Chemical heat pump  

DOEpatents

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.

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

1984-01-01

384

Chemical heat pump  

DOEpatents

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.

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

1984-01-01

385

Chemical heat pump  

DOEpatents

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.

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

1984-01-01

386

Chemical heat pump  

DOEpatents

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.

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

1981-01-01

387

Chemical Looping Combustion Kinetics  

SciTech Connect

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).

Edward Eyring; Gabor Konya

2009-03-31

388

Chemically advanced nanolithography  

NASA Astrophysics Data System (ADS)

The development of hybrid strategies combining chemical self-assembly with conventional fabrication techniques for the advancement of lithography into the sub-100 nm regime has been the focus of the research presented in this thesis. The main objective was the development of the "molecular ruler" process, which utilizes self-assembled multilayers as nanoscale resists for the definition of metal electrode structures with precise nanogap spacings in the 10--100 nm regime. These self-assembled multilayers were composed of alternating, coordinated alpha,o-mercaptoalkanoic acid molecules and Cu2+ ions. The molecular ruler process begins with a lithographically defined gold structure, henceforth called the "parent". Subsequently, the self-assembled multilayers are grown selectively on this parent structure to form a type of lift-off resist. After metal deposition, this resist is removed chemically leaving behind only the newly created "daughter" structure and the lithographic parent structure. The width of the gap between the created daughter structure and the parent structure is measured out precisely by the tailored thickness of the multilayer resist. Gaps of differing sizes between parent and daughter structures can be generated through changing both the number of molecular ruler layers deposited as well as by altering the length of the molecular ruler itself. This process has been characterized by field emission scanning electron microscopy, and gap sizes have been demonstrated routinely in the 10--50 nm range. The molecular ruler process has been extended to fabricate complex hierarchical architectures. Tertiary structures (granddaughters) have been created by depositing multilayers on the daughter structures as well as the parent structures. Removing a sacrificial parent and/or daughter structure by selective chemical etching can isolate the tertiary structures. Using reactive ion etching and the parent and daughter structures as an etch mask, nanogaps can be transferred into the underlying substrate to create precise recessed features. The molecular ruler process has also been combined with nanosphere lithography to display the versatility of the molecular ruler resists around nonplanar edges. Aligned microstructures with precisely defined nanometer-scale spacing and edge resolution were produced by combining multiple levels of photolithography with the molecular ruler process. Photolithography was used to define the structures' orientations and self-assembled multilayer resists were used to tailor the structures' spacings precisely. This work opens the door for future device fabrication by demonstrating the compatibility and robustness of hybrid strategies employing molecular rulers with conventional photolithographic fabrication processes. The integrity of the nanoscale gaps produced by this hybrid technique has been investigated by electrical and structural characterization. The primary failure mode that caused shorting in these structures was identified. Methods for improved lithographic processing were developed and optimized to eliminate the identified failure mode and to create high quality structures. Another important aspect of the hybrid strategies incorporating molecular rulers is that the lithographic resist must be robust enough to withstand the deposition of self-assembled multilayers without compromising their formation. The use of a lithographic resist compatible with self-assembly has opened an avenue for directed chemical patterning of multi-component self-assembled films. A major advantage of this technique is that the different components of the film are shielded by the resist against displacement and intercalation. Additional benefits of this process over other unconventional methods for chemical patterning are the ability to have multiple levels of alignment, reproducible one-to-one feature size transfer, and parallel processing. This thesis research has focused on addressing precision for the creation of nanostructures. Self-assembly and lithographic processing have b

Anderson, Mary Elizabeth

389

Gas phase chemical detection with an integrated chemical analysis system  

SciTech Connect

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.

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

390

Chemical comminution of coal  

SciTech Connect

The objective of the present research is to study the chemical reactivity of a mixture of methyl alcohol and aqueous sodium hydroxide solution in the temperature range 298 to 363 K, and a caustic concentration of 0 to 10 wt. %, on an Iowa bituminous coal. The sample studied was collected from coal zone 4, equivalent to most historical references to Laddsdale coal. The coals in this zone are typical high-sulfur, high-ash middle Pennsylvania Cherokee group coals. The apparent rank is high-volatile C bituminous coal. The relatively high content of sulfur and 23 other elements in these coals is related to near neutral (6-8) pH conditions in the depositional and early diagenetic environments, and to postdepositional sphalerite/calcite/pyrite/kaolinite/barite mineralization.

Mamaghani, A.H.; Beddow, J.K.; Vetter, A.F.

1987-02-01

391

Nanometric chemical clocks  

PubMed Central

Field ion microscopy combined with video techniques and chemical probing reveals the existence of catalytic oscillatory patterns at the nanoscale. This is the case when a rhodium nanosized crystal—conditioned as a field emitter tip—is exposed to hydrogen and oxygen. Here, we show that these nonequilibrium oscillatory patterns find their origin in the different catalytic properties of all of the nanofacets that are simultaneously exposed at the tip's surface. These results suggest that the underlying surface anisotropy, rather than a standard reaction–diffusion mechanism, plays a major role in determining the self-organizational behavior of multifaceted nanostructured surfaces. Surprisingly, this nanoreactor, composed of the tip crystal and a constant molecular flow of reactants, is large enough for the emergence of regular oscillations from the molecular fluctuations.

McEwen, Jean-Sabin; Gaspard, Pierre; de Bocarme, Thierry Visart; Kruse, Norbert

2009-01-01

392

Chemically modified photochemical cell  

SciTech Connect

A chemically modified photoelectrochemical cell is disclosed including at least one cathode and a plurality of anodes, at least said plurality of anodes being constituted with a semiconductor, each of said plurality of anodes being formed by fixing through covalent bonds molecules of at least one sensitizer dye on the surface of a light-transmissible flat plate of an n-type semiconductor or a light-transmissible flat plate covered with a thin film of an n-type semiconductor, and said plurality of anodes being disposed parallelly to each other and in the form of layers in an electrolyte solution, together with said at least one cathode. Thus, since this photoelectrochemical cell can convert photoenergy of a longer wavelength to electric energy with a high efficiency by making the use of the dye sensitization effect, sufficient practical utility to the photodevices is obtained.

Osa, T.; Fujihira, M.

1983-09-06

393

Chemical composition of patikaraparpam.  

PubMed

Patikaraparpam, a Siddha formulation in prepared by trituration of potash alum with egg albumin followed by calcinatin. The three authentic laboratories made parpams as well as six commercial samples have been examined for their chemical composition. The analytical data that emerged from the analysis of the above samples showed that seven parpams contained only aluminium sulphate and they did respond to tests for potassium. An inspection of the crude drugs patikaram' available in the market established that potash alum and ammonia alum are indiscriminateldy taken for use, according to literature, only potash alum should be used in Indian system of medicine. Patikarapparapam is indicated in urinary inflammations and obstructions and is a reputed diuretic. Potassium salts are established diuretic. These studies show that the raw drugs sellers, the pharamaceutists or manufacturers of medicine and the physician as well should make sure that only potash alum is used in Indian medicine. PMID:22556804

Saraswathy, A; Rani, M G; Susan, T; Purushothaman, K K

1997-04-01

394

Chemical heat pump  

DOEpatents

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.

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

1980-01-01

395

Thermal hyperspectral chemical imaging  

NASA Astrophysics Data System (ADS)

Several chemical compounds have their strongest spectral signatures in the thermal region. This paper presents three push-broom thermal hyperspectral imagers. The first operates in MWIR (2.8-5 ?m) with 35 nm spectral resolution. It consists of uncooled imaging spectrograph and cryogenically cooled InSb camera, with spatial resolution of 320/640 pixels and image rate to 400 Hz. The second imager covers LWIR in 7.6-12 ?m with 32 spectral bands. It employs an uncooled microbolometer array and spectrograph. These imagers have been designed for chemical mapping in reflection mode in industry and laboratory. An efficient line-illumination source has been developed, and it makes possible thermal hyperspectral imaging in reflection with much higher signal and SNR than is obtained from room temperature emission. Application demonstrations including sorting of dark plastics and mineralogical mapping of drill cores are presented. The third imager utilizes a cryo-cooled MCT array with precisely temperature stabilized optics. The optics is not cooled, but instrument radiation is suppressed by special filtering and corrected by BMC (Background-Monitoring-on-Chip) method. The approach provides excellent sensitivity in an instrument which is portable and compact enough for installation in UAVs. The imager has been verified in 7.6 to 12.3 ?m to provide NESR of 18 mW/(m2 sr ?m) at 10 ?m for 300 K target with 100 spectral bands and 384 spatial samples. It results in SNR of higher than 500. The performance makes possible various applications from gas detection to mineral exploration and vegetation surveys. Results from outdoor and airborne experiments are shown.

Holma, Hannu; Hyvärinen, Timo; Mattila, Antti-Jussi; Kormano, Ilkka

2012-05-01

396

Gas Phase Chemical Detection with an Integrated Chemical Analysis System  

SciTech Connect

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.

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

397

Bright Ideas for Chemical Biology  

PubMed Central

Small-molecule fluorescent probes embody an essential facet of chemical biology. Although numerous compounds are known, the ensemble of fluorescent probes is based on a modest collection of modular “core” dyes. The elaboration of these dyes with diverse chemical moieties is enabling the precise interrogation of biochemical and biological systems. The importance of fluorescence-based technologies in chemical biology elicits a necessity to understand the major classes of small-molecule fluorophores. Here, we examine the chemical and photophysical properties of oft-used fluorophores, and highlight classic and contemporary examples in which utility has been built upon these scaffolds.

Lavis, Luke D.; Raines, Ronald T.

2009-01-01

398

Rapid Prediction of Chemical Cloud Dispersion from Chemical Spill Accidents  

Microsoft Academic Search

Responders to spill accidents need to have at their fingertips a method of rapid prediction of chemical cloud dispersion behavior and other relative information to protect the public from death and injury during evacuation of the affected area. A survey of 123 chemical spill accidents in the United States where evacuations occurred revealed that available mathematical models were not used

J. NORDIN; D. SHEESLEY; S. B. KING; T. ROUTH; V. SMITH

1998-01-01

399

Chemicals in Classrooms. Pesticides and Maintenance Chemicals in Vermont Schools.  

ERIC Educational Resources Information Center

|This report is the second in a series of studies on the serious threat toxic chemical use may pose to the health of Vermont's children, teachers, and school staff. The first report, "Toxic Chemical Exposure in Schools: Our Children at Risk," provided an overview of the problem of poor indoor air quality (IAQ) in schools and discussed sources of…

Sterling, Peter; Browning, Brigid

400

Commodity chemicals from renewable resources: a chemicals industry model  

Microsoft Academic Search

A comprehensive (approximate) model has been developed to simulate the interdependent nature of a conceptual chemicals industry using common renewable resources to produce a wide array of chemicals by a variety of conversion processes. The model also includes petroleum, natural gas, and coal resources and associated processes; hence the relative role of each resource can be examined under various scenario

T. L. Donaldson; O. L. Culberson

1984-01-01

401

Chemical Structures of Native Oxides Formed during Wet Chemical Treatments  

Microsoft Academic Search

The chemical structures of the native oxides formed during various wet chemical treatments were measured nondestructively by changing the effective electron escape depth. The structures of the native oxides can be characterized by the distribution of suboxide Si3+ in the native oxide films. If Si3+ is correlated with Si-H bonds, the formation rate of the native oxide during the wet

Takeo Hattori; Kazuhiko Takase; Hiroaki Yamagishi; Rinshi Sugino; Yasuo Nara; Takashi Ito

1989-01-01

402

[Chemically-induced scleroderma].  

PubMed

Scleroderma-like diseases can be induced by a number of chemical compounds, such as plastics, solvents and drugs. Contaminated rapeseed oil was the cause of the toxic oil syndrome and L-tryptophan induces the so-called eosinophilia-myalgia-syndrome. On the other hand, paraffin and silicon can trigger so-called adjuvant disease, while long-term exposure to silica can lead to idiopathic scleroderma (associated with silicosis in some cases). In addition to the clinical features, some pathogenetic data in the literature, such as genetic factors (HLA, chromosomal anomalies, enzyme deficiencies) and the metabolism of chlorinated ethylenes via reactive epoxide intermediate products, and our own findings are reported. Silica-induced scleroderma cannot be distinguished from the idiopathic form by epidemiological, clinical or immunological studies or by parameters referring to the blood vessels or collagen metabolism. In cell culture studies it has been shown that macrophages/monocytes release IL1, IL6 and TNF after ingestion of silica, which affects fibroblasts, T-helper cells and endothelial cells. Comparative results from the silicosis literature are reported. Finally, the possibly stimulating role of ionizing irradiation (uranium mining) in favouring the development of scleroderma is discussed. PMID:1506211

Haustein, U F; Ziegler, V; Herrmann, K

1992-08-01

403

Chemical Elements Bingo  

NASA Astrophysics Data System (ADS)

An important part of the high school chemistry program is the topic of periodic classification and periodicity. We have observed that one of the obstacles for the study of the matter is the new vocabulary necessary to initiate this work. Our students have to understand that the periodic classification is an orderly way of presenting the elements and its properties, they compare the table with other classification systems that they already know, nevertheless for the average student it is difficult to deduce or predict properties with periodic classification. As an example of this concept, we can point out the electronic configuration, atomic radii, oxidation state, and valence number. In order to facilitate the learning-teaching process of this topic in high school level, we stimulate the class to play with the periodic table, to get familiar with the general concepts of periodicity. We started our work dealing with the most common elements in each group. Chemical Elements Bingo (CEB) is a game we designed to teach periodic classification.

Tejeda, Silvia; Palacios, Joaquin

1995-12-01

404

Chemical Stockpile Disposal Program  

SciTech Connect

As part of the Chemical Stockpile Disposal Program mandated by Public Law 99--145 (Department of Defense Authorization Act), an independent review is presented of the US Army Phase I environmental report for the disposal program at the Umatilla Depot Activity (UMDA) in Hermiston, Oregon. The Phase I report addressed new and additional concerns not incorporated in the final programmatic environmental impact statement (FPEIS). Those concerns were addressed by examining site-specific data for the Umatilla Depot Activity and by recommending the scope and content of a more detailed site-specific study. This independent review evaluates whether the new site-specific data presented in the Phase I report would alter the decision in favor of on-site disposal that was reached in the FPEIS, and whether the recommendations for the scope and content of the site-specific study are adequate. Based on the methods and assumptions presented in the FPEIS, the inclusion of more detailed site-specific data in the Phase I report does not change the decision reached in the FPEIS (which favored on-site disposal at UMDA). It is recommended that alternative assumptions about meteorological conditions be considered and that site-specific data on water, ecological, socioeconomic, and cultural resources; seismicity; and emergency planning and preparedness be considered explicitly in the site-specific EIS decision-making process. 7 refs., 1 fig.

Krummel, J.R.; Policastro, A.J.; Olshansky, S.J.; McGinnis, L.D.

1990-10-01

405

Chemical Stockpile Disposal Program  

SciTech Connect

As part of the Chemical Stockpile Disposal Program mandated by Public Law 99--145 (Department of Defense Authorization Act), an independent review is presented of the US Army Phase I environmental report for the disposal program at the Pine Bluff Arsenal (PBA) in Arkansas. The Phase I report addressed new and additional concerns not incorporated in the final programmatic environmental impact statement (FPEIS). Those concerns were addressed by examining site-specific data for the PBA and by recommending the scope and content of a more detailed site- specific study. This dependent review evaluates whether the new site-specific data presented in the Phase I report would alter the decision in favor of on-site disposal that was reached in the FPEIS, and whether the recommendations for the scope and content of the site-specific study are adequate. Based on the methods and assumptions presented in the FPEIS, the inclusion of more detailed site-specific data in the Phase I report does not change the decision reached in the FPEIS (which favored on-site disposal at PBA). It is recommended that alternative assumptions about meteorological conditions be considered and that site-specific data on water, ecological, socioeconomic, and cultural resources, and emergency planning and preparedness be considered explicitly in the site-specific EIS decision-making process. 13 refs., 1 fig.

Krummel, J.R.; Policastro, A.J.; Olshansky, S.J.; McGinnis, L.D.

1990-10-01

406

Continuous chemical reaction chromatography  

SciTech Connect

The past three years have been devoted to investigating simulated countercurrent chomatographic moving bed separators (SCMCS) and simulated countercurrent moving bed reactors (SCMCR). These are novel separators and reactors used for separation, or for carrying out a chemical reaction and separation continuously and simultaneously in fixed bed. In the SCMCR and the SCMCS the process aspects of a countercurrent moving bed, in which a stream of solids flows countercurrent to an inert fluid and past stationary reactant inlet, is simulated by successively switching feed and product take-off streams through a series of inlets located at fixed intervals along a fixed bed or between a series of packed columns. The flow of solids past a fixed feed point, characteristic of countercurrent moving beds, is replaced by motion of the feed past a fixed packed bed. Feed enters a particular column for a fixed length of time, and then is switched to the next column. Product streams are also advanced simultaneously. When the feed point has progressed to the end it is returned to the starting position and the process repeated. The shifting of the feed and the product positions in the direction of fluid flow thus simulates the movement of solids in the opposite direction. The requisite motion between the feed and the bed, which is continuous for true countercurrency, is replaced by periodic, discrete steps in simulated countercurrency. The continuous, steady state operation characteristic of true countercurrency is replaced by periodic transients at each switch of the feed.

Aris, R.; Carr, R.W.

1992-01-01

407

Chemical Sensors in Oceanography  

NASA Astrophysics Data System (ADS)

About 40 years ago, I served as graduate student labor on the International Indian Ocean Expedition, where I carried out what seemed to be vast numbers of routine chemical analyses of sea water. I vowed, as have many others, that on my return I would find a better way. From this effort, the first uses of “autoanalyzers” for sea water emerged. Over the years, the demand for fundamental scientific data from the oceans has increased enormously, as has the range of properties and the need for precision and rapidity. The recent global ocean survey of carbon dioxide and related properties carried out by the Joint Global Ocean Flux Study, and World Ocean Circulation Experiment, cruises is but one example of the huge effort involved. There has long been a desire for a set of sophisticated yet robust sensors that would do the job with minimum labor and produce data of maximum quality in environments ranging from the sea surface to the ocean floor. This is quite a tall order!

Brewer, Peter G.

408

Theory of Chemical Modeling  

NASA Astrophysics Data System (ADS)

In order to deal with the complexity of natural systems simplified models are employed to illustrate the principal and regulatory factors controlling a chemical system. Following the aphorism of Albert Einstein: Everything should be made as simple as possible, but not simpler, models need not to be completely realistic to be useful (Stumm and Morgan 1996), but need to meet a successful balance between realism and practicality. Properly constructed, a model is neither too simplified that it is unrealistic nor too detailed that it cannot be readily evaluated and applied to the problem of interest (Bethke 1996). The results of a model have to be at least partially observable or experimentally verifiable (Zhu and Anderson 2002). Geochemical modeling theories are presented here in a sequence of increasing complexity from geochemical equilibrium models to kinetic, reaction path, and finally coupled transport and reaction models. The description is far from complete but provides the needs for the set up of reactive transport models of hydrothermal systems as done within subsequent chapters. Extensive reviews of geochemical models in general can be found in the literature (Appelo and Postma 1999, Bethke 1996, Melchior and Bassett 1990, Nordstrom and Ball 1984, Paschke and van der Heijde 1996).

Kühn, Michael

409

Chemical Control of Plant Growth.  

ERIC Educational Resources Information Center

|Seven experiments are presented in this Science Study Aid to help students investigate the control of plant growth with chemicals. Plant growth regulators, weed control, and chemical pruning are the topics studied in the experiments which are based on investigations that have been and are being conducted at the U. S. Agricultural Research Center,…

Agricultural Research Center (USDA), Beltsville, MD.

410

Properties of chemically bonded phases  

Microsoft Academic Search

Retention on non-polar chemically-bonded stationary phases depends on the silica carrier, the kind of bonded silane, the surface concentration of bonded alkyl groups and the number of surface silanol groups before and after chemical modification. The influence of carbon content of bonded phases, column temperature and how the eluent mixture has been prepared on solute retention is demonstrated. For comparison

H. Engelhardt; G. Ahr

1981-01-01

411

Aspects of chemical laser simulation  

Microsoft Academic Search

Theoretical models for chemical lasers depend on a variety of assumptions and empirical data to provide closure and simplify solution of the governing equations. Among the various assumptions and empirical data built into models for chemical lasers are assumptions regarding steadiness in the time domain and geometric similarity of the computational domain. The objective of our work is to generate

Timothy J. Madden; James H. Miller

2003-01-01

412

Modern Chemical Technology, Volume 7.  

ERIC Educational Resources Information Center

This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: the nature of reversible processes, equilibrium constants, variable reaction tendencies, practical…

Pecsok, Robert L.; Chapman, Kenneth

413

Modern Chemical Technology, Volume 9.  

ERIC Educational Resources Information Center

|This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: ion exchange, electrphoresis, dialysis, electrochemistry, corrosion, electrolytic cells, coulometry,…

Pecsok, Robert L.; Chapman, Kenneth

414

The origin of chemical elements  

Microsoft Academic Search

A review is given on the origin of chemical elements. One part consists of the theory of stellar nucleosynthesis which includes the formation mechanism of the elements via nuclear fusion, capture reaction of light nuclei and capture processes of neutrons and the related topics of the chemical evolution of galaxies. Another part reviews the theory of cosmological nucleosynthesis for light

L.-P. Xu

1987-01-01

415

Chemicals, Health, Environment, and Me.  

ERIC Educational Resources Information Center

|The CHEM (Chemicals, Health, Environment, and Me) Project is a series of 10 units designed to provide experiences for fifth and sixth graders that help them to accomplish an understanding of: (1) the nature of chemicals and how they interact with the environment; (2) how to collect, process, and analyze information; (3) how to use scientific…

California Univ., Berkeley. Lawrence Hall of Science.

416

Great Experiments in Chemical Education.  

ERIC Educational Resources Information Center

|Summarizes papers presented during a symposium at the Seventh Biennial Conference on Chemical Education (Stillwater, Oklahoma 1982). Topics addressed included history of summer institutes and high school CHEM Study Program, educational activities of American Chemical Society (ACS), and activities of ACS Committee on Professional Training and…

Journal of Chemical Education, 1983

1983-01-01

417

Natural selection in chemical evolution  

Microsoft Academic Search

We propose that chemical evolution can take place by natural selection if a geophysical process is capable of heterotrophic formation of liposomes that grow at some base rate, divide by external agitation, and are subject to stochastic chemical avalanches, in the absence of nucleotides or any monomers capable of modular heredity. We model this process using a simple hill-climbing algorithm,

Chrisantha Fernando; Jonathan Rowe

2007-01-01

418

Making Models of Chemical Compounds.  

ERIC Educational Resources Information Center

Describes the benefits and techniques of having students create models of chemical compounds. This hands-on approach uses colored paper and other inexpensive materials to construct the models. A step-by-step approach provides objectives, materials, an explanation on how to calculate chemical ratios, procedures, follow-up activities, and a resource…

Hoehn, Robert G.

1992-01-01

419

Chemically treated kindling and process  

SciTech Connect

A chemically treated kindling and process for the production thereof wherein the kindling is comprised of a pressed mixture of wood fibers, alum, and cornstarch, and is saturated with a prepared composition comprising a plurality of chemically distinct compositions, each of the compositions containing a different predetermined amount of refined petroleum wax and refined oil.

Earlywine, R.T.

1984-10-09

420

Chemicals from Cradle to Grave  

ERIC Educational Resources Information Center

|About two years ago, an urban school district had planned for the disposal of some hazardous chemicals. It contracted with a chemical recycling company that was considered to be reputable. The school district, along with several other companies, was charged and fined by the Environmental Protection Agency for improperly releasing hazardous…

Science Scope, 2005

2005-01-01

421

Chemical Compatibility of Polymeric Materials.  

ERIC Educational Resources Information Center

|Presents some principles for specifying general classes of polymers for predicting relative chemical attack from acids, bases, oxidants, and certain common antagonists. Also discusses predicting relative solvent effects. Suggests uses of this information in two or three lectures in a chemical engineering materials course. (YP)|

Solen, Kenneth A.; Kuchar, Marvin C.

1990-01-01

422

Job Prospects for Chemical Engineers.  

ERIC Educational Resources Information Center

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

Basta, Nicholas

1985-01-01

423

Modern Chemical Technology, Volume 9.  

ERIC Educational Resources Information Center

This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: ion exchange, electrphoresis, dialysis, electrochemistry, corrosion, electrolytic cells, coulometry,…

Pecsok, Robert L.; Chapman, Kenneth

424

Chemicals, Health, Environment, and Me.  

ERIC Educational Resources Information Center

The CHEM (Chemicals, Health, Environment, and Me) Project is a series of 10 units designed to provide experiences for fifth and sixth graders that help them to accomplish an understanding of: (1) the nature of chemicals and how they interact with the environment; (2) how to collect, process, and analyze information; (3) how to use scientific…

California Univ., Berkeley. Lawrence Hall of Science.

425

Chemical hazards in the organisation.  

PubMed

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

Winder, Chris

2012-01-01

426

Magnetic Effects in Chemical Reactions  

Microsoft Academic Search

The Review discusses in what elementary chemical reactions the intrinsic angular momentum of electrons and nuclei is conserved and in what reactions it is not conserved, how weak electron-nuclear magnetic interaction and an external magnetic field influence the conservation of angular momentum and what are the consequences of this effect, and what magnetic effects occur in chemical reactions, as well

Anatolii L Buchachenko

1976-01-01

427

Millisecond chemical reactions and reactors  

Microsoft Academic Search

Short contact time chemical reactors have many features which are very different from conventional packed bed reactors in that temperatures are determined by inlet parameters only, performance is nearly unchanged over wide variations in flow rate, and highly nonequilibrium products can be obtained at high conversions. Chemical reactions occur in regions of large gradients in composition and temperature, so the

Lanny D. Schmidt

2000-01-01

428

CHEMICAL PROTECTION AGAINST IONIZING RADIATION  

Microsoft Academic Search

Recent work on chemical protection against radiation effects in mammals ; is reviewed, especially with respect to whole-body exposure to external radiation. ; This survey shows that many explanations are being offered to account for the ; action of radioprotective agents. In general, the proposed mechanisms are ; concerned with inactivation of radicals and other chemical intermediates, ; depletion of

R. L. Straube; H. M. Patt

1963-01-01

429

Titan's chemical complexity  

NASA Astrophysics Data System (ADS)

We review here our current knowledge of Titan's gas phase chemistry. We base our discussion on photochemical models as well as on laboratory experiments. We identify the lower mass positive [1,2] and negative [3] ions detected in the upper atmosphere and we show that their formation is a direct consequence of the presence of heavy neutrals. We demonstrate that the observed densities of CO, CO2 and H2O can be explained by a combination of exogenous O, and OH/H2O input [4]. We argue that benzene [5] and ammonia [6] are created in the upper atmosphere through complex chemical processes involving both neutral and ion chemistry. These species diffuse downward where they are at the origin of heavier aromatics and amines, respectively. Finally, we discuss the impact on hydrocarbon densities of recent theoretical calculations of the rate constants of association reactions [7]. [1] V. Vuitton, R. V. Yelle and V. G. Anicich, Astrophys. J., 647, L175 (2006). [2] V. Vuitton, R. V. Yelle and M. J. McEwan, Icarus, 191, 722 (2007). [3] V. Vuitton, P. Lavvas, R. V. Yelle, M. Galand, A. Wellbrock, G. R. Lewis, A. J. Coates and J.-E. Wahlund, Planet. Space Sci., 57, 1558 (2009). [4] S. M. Hörst, V. Vuitton, and R. V. Yelle, J. Geophys. Res., 113, E10006 (2008). [5] V. Vuitton, R. V. Yelle and J. Cui, J. Geophys. Res., 113, E05007 (2008). [6] R. V. Yelle, V. Vuitton, P. Lavvas, S. J. Klippenstein, M. A. Smith, S. M. Hörst and J. Cui, Faraday Discuss., 147, 31 (2010). [7] V. Vuitton, R. V. Yelle, S. J. Klippenstein and P. Lavvas, Astrophys. J., in press.

Vuitton, Veronique

2012-04-01

430

Supergiant oil fields and future prospects in the Middle East  

Microsoft Academic Search

Upper Jurassic carbonates, Lower Cretaceous sands, Lower Cretaceous carbonates and Tertiary carbonates of the Middle East contain more than 50% of the worlds oil. Our area of interest covers SE Turkey and Syria in the north to the borders of Yemen and Oman in the south, and from the Red Sea across Saudi Arabia, the Emirates and the Arabian\\/Persian Gulf

L. Christian; D. Johnston

1995-01-01

431

RV and vsini of Ib supergiant stars (de Medeiros+, 2002)  

NASA Astrophysics Data System (ADS)

The observations are from De Medeiros & Mayor, 1999, Cat. . The large majority of the observations were carried out from March 1986 to May 1994, except for those stars having a larger time base. All stars north of declination -25° were observed with the CORAVEL mounted on the Swiss 1-meter telescope at the Haute-Provence Observatory, Saint-Michel (France). The stars south of declination -25° have been measured with the southern CORAVEL at the Cassegrain focus of the 1.5m Danish telescope at ESO La Silla (Chile). (1 data file).

de Medeiros, J. R.; Udry, S.; Burki, G.; Mayor, M.

2003-01-01

432

Supergiant Complexes of Solar Activity and Convection Zone  

Microsoft Academic Search

The global distribution of solar surface activity (active regions) is apparently connected with processes in the convection\\u000a zone. The large-scale magnetic structures above the tachocline could in a pronounced way be observable in the surface magnetic\\u000a field. To get the information regarding large-scale magnetic formations in the convection zone, a set of solar synoptic charts\\u000a (Mount Wilson 1998?–?2004, Fe?i, 525.02 nm)

O. V. Arkhypov; O. V. Antonov; M. L. Khodachenko

2011-01-01

433

2 supergiants and 2 hypergiants radio spectra (Teyssier+, 2012)  

NASA Astrophysics Data System (ADS)

SourceName_LineRestFreqMHz.fits, FITS file created by GILDAS/Class where - SourceName is one of "AFGL2343", "BETELGEUSE", "NML_CYG" or "IRC+10420" - LineRestFreq is the rest frequency in MHz of the main spectral line concerned by the file. (2 data files).

Teyssier, D.; Quintana-Lacaci, G.; Marston, A. P.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Decin, L.; Dominik, C.; Justtanont, K.; de Koter, A.; Melnick, G.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Soria-Ruiz, R.; Schoeier, F. L.; Szczerba, R.; Waters, L. B. F. M.

2012-09-01

434

Tengiz oil field, Kazakstan: A carbonate platform and supergiant field  

SciTech Connect

The Tengiz oil field was discovered in 1979 on the northeastern shore of the Caspian Sea in western Kazakstan. The Carboniferous and Devonian age carbonate reservoir is more than 2000 in, thick, 270 km[sup 2] in area extent and buried to a depth of 4000 m (13,120 ft.). The oil column exceeds 1450 m in length and is highly overpressured. The Tengiz reservoir resembles a modem day constructional-type carbonate platform in size, shape and lithofacies. The top of the platform is relatively flat, except for structural highs along the northern, eastern and southern platform margins that developed during post-depositional down-faulting of the platform interior. The platform edge is a depositional escarpment along which subsequent faulting has occurred. Debris-slope conglomerates, shed off the platform during growth, surround the platform escarpment. Bashkirian age ootitic, crinoidal, algal grainstones comprise the upper 100 m of the platform and overlie 350 m of Serpukhovian and Okskian age brachiopodal, crinoidal, algal packstones. Lithofacies are a really widespread and show little variation in composition and stratigraphic thickness across the entire platform. Depositional cycle thicknesses are less than 5 meters for the Bashkirian grainstones and up to 30 meters for the Serpukhovian/Oksky packstones. Lagoonal and reefal lithofacies have not been identified in core to date. Porosity is highly variable and includes interparticle, moldic, channel, vuggy and fracture pore types. Solid bitumen is present in much of the pore space. Secondary porosity formed both before and after bitumen precipitation. Production logs and core data reveal that zones with secondary porosity provide fluid entry into the wellbore.

Wood, W.R. (Chevron Overseas Petroleum, Inc., San Ramon, CA (United States)); Garber, R.A. (Chevron USA, Midland, TX (United States))

1996-01-01

435

Chevron near green light to tap supergiant Tengiz in Kazakhstan  

SciTech Connect

Chevron Crop. may soon have a green light to proceed with its Tengiz project in the former Soviet republic of Kazakhstan. The company confirmed an earlier announcement in Alma Ata that it signed a protocol agreeing to principles of cooperation with Kazakhstan on exploration an oil field development. Chevron and Kazakh officials are preparing documents for signature that will enable the project to move forward. The action caps more than 2 years of discussion with officials of the former Soviet Union as well post-Soviet Russia and Kazakhstan. This paper reports that Chevron's original proposal called for it to add Tengiz to its existing Caspian Sea joint venture. The venture, Tengizchevroil, was to involve exploration and production in an area of about 8,900 sq miles and include Tengiz. It would have to construct an oil and gas processing plant with special desulfurization capabilities for each 65,000 b/d of production.

Not Available

1992-05-18

436

An emerging coherent picture of red supergiant supernova explosions  

NASA Astrophysics Data System (ADS)

Three lines of evidence indicate that in the most common type of core-collapse supernovae, the energy deposited in the ejecta by the exploding core is approximately proportional to the progenitor mass cubed. This result stems from an observed uniformity of light-curve plateau duration, a correlation between mass and ejecta velocity, and the known correlation between luminosity and velocity. This result ties in analytical and numerical models together with observations, providing us with clues as to the mechanism via which the explosion of the core deposits a small fraction of its energy into the hurled envelope.

Poznanski, Dovi

2013-10-01

437

Chemical Soil Physics Phenomena for Chemical Sensing of Buried UXO  

SciTech Connect

Technology development efforts are under way to apply chemical sensors to discriminate inert ordnance and clutter from live munitions that remain a threat to reutilization of military ranges. However, the chemical signature is affected by multiple environmental phenomena that can enhance or reduce its presence and transport behavior, and can affect the distribution of the chemical signature in the environment. For example, the chemical can be present in the vapor, aqueous, and solid phases. The distribution of the chemical among these phases, including the spatial distribution, is key in designing appropriate detectors, e.g., gas, aqueous or solid phase sampling instruments. A fundamental understanding of the environmental conditions that affect the chemical signature is needed to describe the favorable and unfavorable conditions of a chemical detector based survey to minimize the consequences of a false negative. UXO source emission measurements are being made to estimate the chemical flux from a limited set of ordnance items. Phase partitioning analysis has been completed to show what the expected concentrations of chemical analytes would be fi-om total concentrations measured in the soil. The soil moisture content in the dry region has been shown to be critical in the attenuation of soil gas concentrations by increased sorption to soil particles. Numerical simulation tools have been adapted to include surface boundary conditions such as solar radiation, surface boundary layer (which is a function of wind speed), precipitation and evaporation, and plant cover/root density to allow transport modeling and evaluate long term processes. Results of this work will provide performance targets for sensor developers and support operational decisions regarding field deployments.

Phelan, James, M.; Webb, Stephen W.

1999-06-14

438

Chemical Force Microscopy of Chemical and Biological Interactions  

SciTech Connect

Interactions between chemical functionalities define outcomes of the vast majority of important events in chemistry, biology and materials science. Chemical Force Microscopy (CFM)--a technique that uses direct chemical functionalization of AFM probes with specific functionalities--allows researchers to investigate these important interactions directly. We review the basic principles of CFM, some examples of its application, and theoretical models that provide the basis for understanding the experimental results. We also emphasize application of modern kinetic theory of non-covalent interactions strength to the analysis of CFM data.

Noy, A

2006-01-02

439

Method of forming a chemical composition  

DOEpatents

A method of forming a chemical composition such as a chemical hydride is described and which includes the steps of selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of hydrogen; and exposing the selected composition to an amount of ionizing radiation to encourage the changing of the chemical bonds of the selected composition, and chemically reacting the selected composition with the source of hydrogen to facilitate the formation of a chemical hydride.

Bingham, Dennis N. (Idaho Falls, ID); Wilding, Bruce M. (Idaho Falls, ID); Klingler, Kerry M. (Idaho Falls, ID); Zollinger, William T. (Idaho Falls, ID); Wendt, Kraig M. (Idaho Falls, ID)

2007-10-09

440

Predicting Anatomical Therapeutic Chemical (ATC) Classification of Drugs by Integrating Chemical-Chemical Interactions and Similarities  

Microsoft Academic Search

The Anatomical Therapeutic Chemical (ATC) classification system, recommended by the World Health Organization, categories drugs into different classes according to their therapeutic and chemical characteristics. For a set of query compounds, how can we identify which ATC-class (or classes) they belong to? It is an important and challenging problem because the information thus obtained would be quite useful for drug

Lei Chen; Wei-Ming Zeng; Yu-Dong Cai; Kai-Yan Feng; Kuo-Chen Chou

2012-01-01

441

Chemical mapping of Vesta  

NASA Astrophysics Data System (ADS)

Vesta’s surface mineralogy and composition have been studied for decades via telescopic spectroscopy and laboratory analyses of the howardite, eucrite, and diogenite (HED) meteorites, which are thought to originate from Vesta. Visible and infrared reflectance measurements by Dawn have broadly confirmed the paradigm established by Earth-based work, strengthening the Vesta-HED connection. The Dawn mission has achieved a milestone by completing the first chemical measurements of a main-belt asteroid using nuclear spectroscopy. Dawn’s Gamma Ray and Neutron Detector (GRaND) has globally mapped the composition of Vesta, including the portions of the northern hemisphere not illuminated by solar radiation. GRaND is sensitive to the composition of the bulk regolith to depths of several decimeters. Abundances and/or detection limits for specific elements and elemental ratios, such as H, Fe, Si, Fe/O, Fe/Si, and K, have been measured. Variations in the average atomic mass and neutron macroscopic absorption cross section have been characterized. The measurements constrain the relative proportions of HED whole-rock end-members, providing measurements of the pyroxene and plagioclase content of the regolith, thereby constraining the processes underlying Vesta’s differentiation and crustal evolution. The spatial resolution of GRaND is sufficient to determine basin-average compositions of Veneneia and Rheasilvia, which may contain outcrops of Vesta’s olivine-rich mantle. While the elemental composition of Vesta’s regolith is similar to the meteorites, there are notable departures from HED whole-rock compositions. While these differences are not sufficient to topple the Vesta-HED paradigm, they provide insight into global-scale processes that have shaped Vesta’s surface. Questions addressed by the analysis of GRaND data include: (i) Is Vesta the source of the Fe-rich mesosiderites? (ii) Are evolved, igneous lithologies present on Vesta’s surface? (iii) What are the origins of exogenic materials found in Vesta’s regolith? (iv) Is the vestan mantle exposed within the southern basins?

Yamashita, Naoyuki; Prettyman, T. H.; Mittlefehldt, D. W.; Lawrence, D. J.; Beck, A. W.; McSween, H. Y.; Feldman, W. C.; McCoy, T. J.; Titus, T. N.; Toplis, M. J.; Reedy, R. C.; Forni, O.; Mizzon, H.; Peplowski, P. N.; Raymond, C. A.; Russell, C. T.

2012-10-01

442

Chemical detection of buried landmines  

SciTech Connect

Of all the buried landmine identification technologies currently available, sensing the chemical signature from the explosive components found in landmines is the only technique that can classify non-explosive objects from the real threat. In the last two decades, advances in chemical detection methods has brought chemical sensing technology to the foreground as an emerging technological solution. In addition, advances have been made in the understanding of the fundamental transport processes that allow the chemical signature to migrate from the buried source to the ground surface. A systematic evaluation of the transport of the chemical signature from inside the mine into the soil environment, and through the soil to the ground surface is being explored to determine the constraints on the use of chemical sensing technology. This effort reports on the results of simulation modeling using a one-dimensional screening model to evaluate the impacts on the transport of the chemical signature by variation of some of the principal soil transport parameters.

Phelan, J.M.; Webb, S.W.

1998-03-01

443

Extragalactic Chemical Abundances: Do H II Regions and Young Stars Tell the Same Story? The Case of the Spiral Galaxy NGC 300  

NASA Astrophysics Data System (ADS)

We have obtained new spectrophotometric data for 28 H II regions in the spiral galaxy NGC 300, a member of the nearby Sculptor Group. The detection of several auroral lines, including [O III] ?4363, [S III] ?6312, and [N II] ?5755, has allowed us to measure electron temperatures and direct chemical abundances for the whole sample. We determine for the first time in this galaxy a radial gas-phase oxygen abundance gradient based solely on auroral lines, and obtain the following least-square solution: 12 + log(O/H) = 8.57(±0.02) - 0.41(±0.03)R/R 25, where the galactocentric distance is expressed in terms of the isophotal radius R 25. The characteristic oxygen abundance, measured at 0.4 × R 25, is 12 + log(O/H) = 8.41. The gradient corresponds to -0.077 ± 0.006 dex kpc-1, and agrees very well with the galactocentric trend in metallicity obtained for 29 B and A supergiants in the same galaxy, -0.081 ± 0.011 dex kpc-1. The intercept of the regression for the nebular data virtually coincides with the intercept obtained from the stellar data, which is 8.59(±0.05). This allows little room for depletion of nebular oxygen onto dust grains, although in this kind of comparison we are somewhat limited by systematic uncertainties, such as those related to the atomic parameters used to derive the chemical compositions. We discuss the implications of our result with regard to strong-line abundance indicators commonly used to estimate the chemical compositions of star-forming galaxies, such as R 23. By applying a few popular calibrations of these indices based on grids of photoionization models on the NGC 300 H II region fluxes, we find metallicities that are higher by 0.3 dex (a factor of 2) or more relative to our nebular (Te based) and stellar ones. We detect Wolf-Rayet stellar emission features in ~1/3 of our H II region spectra, and find that in one of the nebulae hosting these hot stars the ionizing field has a particularly hard spectrum, as gauged by the "softness" parameter ? = (O+/O++)/(S+/S++). We suggest that this is related to the presence of an early WN star. By considering a larger sample of extragalactic H II regions we confirm, using direct abundance measurements, previous findings of a metallicity dependence of ?, in the sense that softer stellar continua are found at high metallicity. Based on observations collected at the European Southern Observatory, Chile, under program 077.B-0269.

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

2009-07-01

444

EXTRAGALACTIC CHEMICAL ABUNDANCES: DO H II REGIONS AND YOUNG STARS TELL THE SAME STORY? THE CASE OF THE SPIRAL GALAXY NGC 300  

SciTech Connect

We have obtained new spectrophotometric data for 28 H II regions in the spiral galaxy NGC 300, a member of the nearby Sculptor Group. The detection of several auroral lines, including [O III] {lambda}4363, [S III] {lambda}6312, and [N II] {lambda}5755, has allowed us to measure electron temperatures and direct chemical abundances for the whole sample. We determine for the first time in this galaxy a radial gas-phase oxygen abundance gradient based solely on auroral lines, and obtain the following least-square solution: 12 + log(O/H) = 8.57({+-}0.02) - 0.41({+-}0.03)R/R {sub 25}, where the galactocentric distance is expressed in terms of the isophotal radius R {sub 25}. The characteristic oxygen abundance, measured at 0.4 x R{sub 25}, is 12 + log(O/H) = 8.41. The gradient corresponds to -0.077 {+-} 0.006 dex kpc{sup -1}, and agrees very well with the galactocentric trend in metallicity obtained for 29 B and A supergiants in the same galaxy, -0.081 {+-} 0.011 dex kpc{sup -1}. The intercept of the regression for the nebular data virtually coincides with the intercept obtained from the stellar data, which is 8.59({+-}0.05). This allows little room for depletion of nebular oxygen onto dust grains, although in this kind of comparison we are somewhat limited by systematic uncertainties, such as those related to the atomic parameters used to derive the chemical compositions. We discuss the implications of our result with regard to strong-line abundance indicators commonly used to estimate the chemical compositions of star-forming galaxies, such as R {sub 23}. By applying a few popular calibrations of these indices based on grids of photoionization models on the NGC 300 H II region fluxes, we find metallicities that are higher by 0.3 dex (a factor of 2) or more relative to our nebular (T{sub e} based) and stellar ones. We detect Wolf-Rayet stellar emission features in {approx}1/3 of our H II region spectra, and find that in one of the nebulae hosting these hot stars the ionizing field has a particularly hard spectrum, as gauged by the 'softness' parameter {eta} = (O{sup +}/O{sup ++})/(S{sup +}/S{sup ++}). We suggest that this is related to the presence of an early WN star. By considering a larger sample of extragalactic H II regions we confirm, using direct abundance measurements, previous findings of a metallicity dependence of {eta}, in the sense that softer stellar continua are found at high metallicity.

Bresolin, Fabio; Kudritzki, Rolf-Peter; Urbaneja, Miguel A. [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Gieren, Wolfgang; Pietrzynski, Grzegorz [Universidad de Concepcion, Departamento de Astronomia, Casilla 160-C, Concepcion (Chile); Carraro, Giovanni [European Southern Observatory, Alonso de Cordova 3107, Santiago (Chile)

2009-07-20

445

ROLE OF THE CHEMICAL WEAPONS CONVENTION IN COMBATING CHEMICAL TERRORISM  

Microsoft Academic Search

The Chemical Weapons Convention (CWC) is shortly characterised stressing its main principles, inter alia the General Purpose\\u000a Criterion. Status of its implementation as of December 2004 shows the main data obligatory declared by already 167 States\\u000a Parties and main achievements in destruction of Chemical Weapons (CW) stockpiles and destruction \\/ conversion of CW production\\u000a facilities and the verification efforts. The

Jiri Matousek

446

Chemical metrology, chemistry and the uncertainty of chemical measurements  

Microsoft Academic Search

Chemical results normally involve traceability to two reference points, the specific chemical entity and the quantity of this\\u000a entity. Results must also be traceable back to the original sample. As a consequence, any useful estimation of uncertainty\\u000a in results must include components arising from any lack of specificity of the method, the variation between repeats of the\\u000a measurement and the

John L. Love

2002-01-01

447

Hearing: the effects of chemicals  

SciTech Connect

Recent studies of human beings exposed to environmental chemicals, as well as experimental animal studies, have identified a number of chemical agents that are commercial products, chemical intermediaries, waste products, or contaminants that are potentially ototoxic. The classes of compounds discussed in this review include organic solvents, asphyxiant gases, and heavy metals that are present in the environment as industrial pollutants or byproducts. Both human and animal investigations are summarized in discussing the actions of these ototoxic compounds. The suggested gaps in our knowledge are highlighted to help direct future research.87 references.

Rybak, L.P. (Department of Surgery, School of Medicine, Southern Illinois University, Springfield (United States))

1992-06-01

448

Development of a chemical vision spectrometer to detect chemical agents.  

SciTech Connect

This paper describes initial work in developing a no-moving-parts hyperspectral-imaging camera that provides both a thermal image and specific identification of chemical agents, even in the presence of nontoxic plumes. The camera uses enhanced stand-off chemical agent detector (ESCAD) technology based on a conventional thermal-imaging camera interfaced with an acousto-optical tunable filter (AOTF). The AOTF is programmed to allow selected spectral frequencies to reach the two dimensional array detector. These frequencies are combined to produce a spectrum that is used for identification. If a chemical agent is detected, pixels containing the agent-absorbing bands are given a colored hue to indicate the presence of the agent. In test runs, two thermal-imaging cameras were used with a specially designed vaporizer capable of controlled low-level (low ppm-m) dynamic chemical releases. The objective was to obtain baseline information about detection levels. Dynamic releases allowed for realistic detection scenarios such as low sky, grass, and wall structures, in addition to reproducible laboratory releases. Chemical releases consisted of dimethylmethylphosphonate (DMMP) and methanol. Initial results show that the combination of AOTF and thermal imaging will produce a chemical image of a plume that can be detected in the presence of interfering substances.

Demirgian, J.

1999-02-23

449

Coatings with controlled porosity and chemical properties  

DOEpatents

Coatings and sensors having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided.

Frye, Gregory C. (Bernalillo County, NM); Brinker, C. Jeffrey (Albuquerque, NM); Doughty, Daniel H. (Albuquerque, NM); Bein, Thomas (Albuquerque, NM); Moller, Karin (Albuquerque, NM)

1996-01-01

450

Coatings with controlled porosity and chemical properties  

DOEpatents

Coatings and sensors are disclosed having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided. 7 figs.

Frye, G.C.; Brinker, C.J.; Doughty, D.H.; Bein, T.; Moller, K.

1996-12-31

451

Coatings with controlled porosity and chemical properties  

DOEpatents

Coatings and sensors having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided.

Frye, Gregory C. (P.O. Box 763, Cedar Crest, NM 87008); Brinker, C. Jeffrey (14 Eagle Nest Dr., NE., Albuquerque, NM 87122); Doughty, Daniel H. (11724 Woodmar La., NE., Albuquerque, NM 87111); Bein, Thomas (1114 Princeton Dr., NE., Albuquerque, NM 87106); Moller, Karin (1114 Princeton Dr., NE., Albuquerque, NM 87106)

1993-01-01

452

High Repetition Rate Chemical Laser.  

National Technical Information Service (NTIS)

A hydrogen fluoride (HF) chemical laser with an active medium 10 cm in length was constructed for operation at high pulse repetition rates using transverse excitation. The device employed 29 resistively loaded electrodes; open-cycle operation was achieved...

T. V. Jacobson G. H. Kimbell A. R. Lambert D. R. Snelling

1973-01-01

453

Organic Chemicals: Angels or Goblins?  

ERIC Educational Resources Information Center

|Discusses some of the controversial organic chemical substances such as DDT, Red Dye No. 2, DES, Tris, Laetrile, cyclamate, and saccharin. Concludes that the use of some has to be considered on a benefit/risk ratio. (GA)|

Ferguson, Lloyd N.

1978-01-01