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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Lick optical spectra of quasar HS 1946+7658 at 10 kilometers per second resolution Lyman-alpha forest and metal absorption systems

We present optical spectra of the most luminous known quasi stellar object (QSO) HS 1946+7658 (z(sub em) = 3.051). Our spectra have both full wavelength coverage, 3240-10570 A, and in selected regions, either high signal-to-noise ratio, SNR approximately equals 40-100, or unusually high approximately 10 km/sec resolution, and in parts of the Ly alpha forest and to the red of Ly alpha emission they are among the best published. We find 113 Ly alpha systems and six metal-line systems, three of which are new. The metal systems at z(sub abs) = 2.844 and 3.050 have complex velocity structure with four and three prominent components, respectively. We find that the system at z(sub abs) = 2.844 is a damped Ly alpha absorption (DLA) system, with a neutral hydrogen column density of log N(H I) = 20.2 +/- 0.4, and it is the cause of the Lyman limit break at lambda approximately equals 3520 A. We believe that most of the H I column density in this system is in z(sub abs) = 2.8443 component which shows the strongest low-ionization absorption lines. The metal abundance in the gas phase of the system is (M/H) approximately equals -2.6 +/- 0.3, with a best estimate of (M/H) = -2.8, with ionizaion parameter log gamma = -2.75, from a photoionization model. The ratios of the logarithmic abundances of C, O, Al, and Si are all within a factor of 2 of solar, which is important for two reasons. First, we believe that the gas abundances which we measure are close to the total abundances, because the ratio of aluminum to other elements is near cosmic, and Al is a refractory element which depletes very readily like chromium, in the interstellar medium. Second, we do not see the enhancement of O with respect to C of (O/C) approximately equals 0.5-0.9 reported in three partial Lyman limit systems by Reimers et al. (1992) and Vogel & Reimers (1993); we measure (O/C) = -0.06 for observed ions and (O/C) approximately equals 0.2 after ionization corrections, which is consistent with solar abundances. We see C II*(lambda 1335) offset by 15 km/sec with respect to C II(lambda 1334), presumably because the gas density varies from 2 to 8 cm(exp -3) with changing velocity in the DLA system. These densities imply that the damped component is 6-25 pc thick, which is reasonable for a single cloud in a cold spiral disk. They also imply that the cloud is relatively highly ionized with more C III than C II, more O III than O I, and log N(H I) = 20.72, which is 3 times the H I column. The system at z(abs) = 1.7382 is also believed to be damped with N(H I) approximately equals 10(exp 21) cm(exp -2), because we see Cr II, but its Ly alpha line will never be seen because it is below the Lyman limit of the other DLA system. We see a 2.6 sigma lack of Ly alpha forest lines well away from the QSO redshift, which may be a chance fluctuation. We also see a correlation between column density N(H I) and Doppler parameter b for 96 unsaturated Ly Alpha forest absorption lines, and although this correlation persists in the 36 Ly alpha lines which lie in regions where the SNR approximately equals 8-16, we agree with Rauch et al. (1993) that it is probably a bogus effect of low supernova remnant (SNR). The same applies to lines with very low b values: in regions where SNR less than or equal to 8 we see many Ly alpha lines which appear to have 10 less than or equal to b less than or equal to 20, but when 8 less than or equal to SNR less than or equal to 16 we see only one line with b less than or equal to 15 km/sec, and two others which we believe have b less than or equal to 20, with values of 20 and 16 km/sec. Traditional Ly alpha line samples which include all lines which have W/sigma(W) greater than or equal to 4 are not adequate to explore the distribution of the properties of individual clouds, because we need much higher (W/sigma(W)) and SNR to avoid the strong biases.

Fan, Xiao-Ming↗
NASA NTRS2004

A Hot Envelope Around the Southern Coalsack: X-ray and Far-Ultraviolet Observations

We present Far Ultraviolet Spectroscopic Explorer and ROSAT X-ray observations toward the Southern Coalsack. An almost complete X-ray halo can be seen around the cloud in the 0.75 and 1.5 keV images, and most of the observed stars show O VI absorption. Both the cloud and the stars have highly accurate distance determinations, allowing us to reliably place the stars and the cloud relative to each other. Using these distance determinations, we find no O VI-bearing gas in the foreground of the Coalsack, while for stars in the background of the cloud, O VI absorption is the norm. The column density of O VI correlates with the 0.75 and 1.5 keV intensities. These results suggest that the X-ray-emitting hot plasma is associated with the dense cloud. We propose that the heating of the Coalsack envelope is due to the hot gas in the interior of the Upper Cen-Lup superbubble. The Coalsack interaction region provides a nearby example of the hot-cold gas interfaces thought to be responsible for the O VI absorptions seen on many sight lines throughout the Galaxy.

Anderson, B.-G.↗
NASA NTRS2017

Synthetic Absorption Lines for a Clumpy Medium: A Spectral Signature for Cloud Acceleration in AGN?

There is increasing evidence that the highly ionized multiphase components of AGN disc winds may be due to thermal instability. The ions responsible for forming the observed X-ray absorption lines may only exist in relatively cool clumps that can be identified with the so-called warm absorbers. Here we calculate synthetic absorption lines for such warm absorbers from first principles by combining 2D hydrodynamic solutions of a two-phase medium with a dense grid of photoionization models to determine the detailed ionization structure of the gas. Our calculations reveal that cloud disruption, which leads to a highly complicated velocity field (i.e. a clumpy flow), will only mildly affect line shapes and strengths when the warm gas becomes highly mixed but not depleted. Prior to complete disruption, clouds that are optically thin to the driving UV resonance lines will cause absorption at an increasingly blueshifted line-of-sight velocity as they are accelerated. This behavior will imprint an identifiable signature on the line profile if warm absorbers are enshrouded in an even broader absorption line produced by a high column of intercloud gas. Interestingly, we show that it is possible to develop a spectral diagnostic for cloud acceleration by differencing the absorption components of a doublet line, a result that can be qualitatively understood using a simple partial covering model. Our calculations also permit us to comment on the spectral differences between cloud disruption and ionization changes driven by flux variability. Notably, cloud disruption offers another possibility for explaining absorption line variability.

line: formation – galaxies: nuclei – quasars: ↗
NASA NTRS1993

The detection of large amounts of cool, x ray absorbing gas in distant clusters of galaxies. What does this mean?

We present an x-ray spectral study of 12 distant (z = 0.17-0.54) rich clusters of galaxies observed with the Einstein Observatory Imaging Proportional Counter. These x-ray spectral data show evidence for substantial excess absorptions beyond those expected in the galaxy, indicating the presence of large amounts of x-ray absorbing cool gas in these distant clusters. The mean value of the excess absorptions corresponds to an absorbing gas column density approximately greater than 10(exp 21)/sq cm. We calculate the x-ray luminosities of the clusters with observed fluxes only in the 0.8-3.5 keV band where the fluxes are less effected by the absorptions, and use the temperature-to-luminosity correlation (known only for nearby clusters) to estimate the temperatures of the hot intracluster medium (ICM) in the distant clusters. These temperature estimates, together with the spectral fits, provide further constraints on the column densities in the individual clusters. For the cluster CL 0016+16, the lower limit on the column density is found to be 8 x 10(exp 20)/sq cm at the 99 percent confidence limit. We also show that the ratio of the temperature obtained from the spectral fit to the temperature expected from the correlation tends to decrease with increasing look-back time, indicating possible temperature evolution of the hot ICM in the recent past. The inclusion of this evolutionary effect further increases the absorptions required in fitting the spectra.

Wang, Qingde↗
NASA NTRS1989

Fast spectroscopic variations on rapidly-rotating, cool dwarfs. 3: Masses of circumstellar absorbing clouds on AB Doradus

New time-resolved H alpha, Ca II H and K and Mg II h and k spectra of the rapidly-rotating K0 dwarf star AB Doradus (= HD 36705). The transient absorption features seen in the H alpha line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines of sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. At any given time the star appears to be surrounded by at least 6 to 10 clouds with masses in the range 2 to 6 x 10(exp 17) g. The clouds appear to have turbulent internal velocity dispersions of order 3 to 20 km/s, comparable with the random velocities of discrete filamentary structures in solar quiescent prominences. Night-to-night changes in the amount of Ca II resonance line absorption can be explained by changes in the amplitude of turbulent motions in the clouds. The corresponding changes in the total energy of the internal motions are of order 10(exp 29) erg per cloud. Changes of this magnitude could easily be activated by the frequent energetic (approximately 10(exp 34) erg) x ray flares seen on this star.

Cameron, A. Collier↗
NASA NTRS2014

Global Free Tropospheric NO2 Abundances Derived Using a Cloud Slicing Technique Applied to Satellite Observations from the Aura Ozone Monitoring Instrument (OMI)

We derive free-tropospheric NO2 volume mixing ratios (VMRs) and stratospheric column amounts of NO2 by applying a cloud slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column versus the cloud scene pressure is proportional to the NO2 VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO2 vertical column density (VCD) (defined as the NO2 column from the cloud scene pressure to the top-of-the-atmosphere) from a differential optical absorption spectroscopy (DOAS) algorithm. Estimates of stratospheric column NO2 are obtained by extrapolating the linear fits to the tropopause. We compare OMI-derived NO2 VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO2 VMR in cloudy conditions. Enhanced NO2 in the free troposphere commonly appears near polluted urban locations where NO2 produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO2 are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud slicing data indicates signatures of uplifted and transported anthropogenic NO2 in the middle troposphere as well as lightning-generated NO2 in the upper troposphere. Comparison of the climatology with simulations from the Global Modeling Initiative (GMI) for cloudy conditions (cloud optical thicknesses > 10) shows similarities in the spatial patterns of continental pollution outflow. However, there are also some differences in the seasonal variation of free-tropospheric NO2 VMRs near highly populated regions and in areas affected by lightning-generated NOx. Stratospheric column NO2 obtained from cloud slicing agrees well with other independently-generated estimates, providing further confidence in the free-tropospheric results.

NO2↗
NASA NTRS1994

A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology

This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the geometrical properties of ice crystals before the influence of ice crystal shape on cirrus radiative properties can be adequately understood. This study provides a way of coupling the radiative properties of absorption, extinction, and single scatter albedo to the microphysical properties of cirrus clouds. The dependence of extinction and absorption on ice crystal shape was not just due to geometrical differences between crystal types, but was also due to the effect these differences had on the evolution of ice particle size spectra. The ice particle growth model in Part 1 and the radiative properties treated here are based on analytical formulations, and thus represent a computationally efficient means of modeling the microphysical and radiative properties of cirrus clouds.

Mitchell, David L.↗
NASA NTRS2000

FUSE Observations of O VI Absorption in the Local Interstellar Medium

We report the results of an initial Far Ultraviolet Spectroscopic Explorer (FUSE) survey of O VI Lambda 1032 absorption along the lines of sight to eleven nearby white dwarfs, ten of which are within the Local Bubble (LB; d < or approximately equal 100 pc). A goal of this survey is to investigate the possible formation of O VI in the conductive interfaces between cool (about 10(exp 4) K) clouds immersed in the presumably hot (10(exp 6) K) gas within the LB. This mechanism is often invoked to explain the widespread presence of 0 VI throughout the Galactic disk. We find no 0 VI absorption toward two stars, and the column densities along three additional sight lines are quite low; N(O VI) about 5 x 10(exp 13)/sq cm. In several directions, we observe rather broad, shallow absorption with N(O VI) about 1 - 2 x 10(exp 13)/sq cm. Models of conductive interfaces predict narrow profiles with N(OVI) > or about equal to 10(exp 13)/sq cm per interface, in the absence of a significant transverse magnetic field. Hence, our observations of weak 0 VI absorption indicate that conduction is being quenched, possibly by non-radial magnetic fields. Alternatively, the gas within the LB may not be hot. Breitschwerdt & Schmutzler have proposed a model for the LB in which an explosive event within a dense cloud created rapid expansion and adiabatic cooling, resulting in a cavity containing gas with a kinetic temperature of T about 50,000 K, but with an ionization state characteristic of much hotter gas. This model has a number of attractive features, but appears to predict significantly more O VI than we observe.

Oegerle, W. R.↗
DOE OSTI2020

FY2020 Rotating Bed Reactor for Iodine Removal from WTP Melter Effluent to Support DFLAW Start-Up

In Performance Assessment (PA) of the Hanford Integrated Disposal Facility (IDF), 129 I is a significant contributor to the risk. The 2017 IDF PA accounted for 0.22% of the total 129 I inventory in Hanford tank waste as residing in the solidified liquid waste from the Effluent Treatment Facility (ETF). However, recent estimates suggest that higher percentages of the iodine processed at the Hanford Waste Treatment and Immobilization Plant (WTP) may be present in the liquid waste routed to the Liquid Effluent Retention Facility (LERF) for eventual treatment at the ETF. In addition, a recent integrated melter test performed at the Vitreous State Laboratory (VSL) at The Catholic University of America (CUA) showed the possibility that a significant fraction (>50%) of the total iodine in the melter feed could be present in the aqueous waste stream destined for the ETF. This stream represents a combination of the Effluent Management Facility (EMF) evaporator overhead condensate and the liquid waste from the WTP off-gas caustic scrubber. Higher levels of 129 I in this stream could affect the LERF and ETF Hazard Categorizations as well as the acceptability of the solidified ETF liquid secondary waste brine for disposal at the IDF. Accordingly, there is a need to investigate and develop potential methods and processes to mitigate this risk. Washington River Protection Solutions, LLC (WRPS) tasked Atkins and VSL to perform development and testing work to evaluate potential methods for removal of iodine species from the waste stream routed to the LERF. In particular, the testing investigated the use of an Atkins-SpinIonic™ Rotating Bed Reactor (RBR) system as a potential alternative to conventional column-based ion exchange or absorption processes. The present report provides results obtained from testing with an RBR system for the removal of iodine from simulants of the projected WTP waste stream that discharges to the LERF.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1973

Biomass in the upwelling areas along the northwest coast of Africa as viewed with ERTS-1

Light penetration in water is affected by plankton, algae, and dissolved and suspended matter. As a consequence, the composition of backscattered light from below the air-sea interface is determined by the nature of the constituents in the water column. In contrast to the absorption spectrum of chemically pure chlorophyll in solution, algae suspensions absorb and scatter light more uniformly throughout the visible part of the electromagnetic spectrum. Because of their spectral absorption and scattering properties plankton concentration can be estimated by measuring the spectral backscattered radiance over water. Experiments using this approach were performed in upwelling regions along the northwest coast of Africa.

Szekielda, K.↗
NASA NTRS1980

The X-ray spectrum of QSO 0241+622

Proportional counters on the OsO-8 spacecraft measured the X-ray spectrum of QSR 0241+622 in the range 2-50 keV. The best power law fit has a proton spectral index and 90 percent errors gamma = 1.93 (+0.5, -0.3) and low energy absorption consistent with reported gas column densities, but a thermal bremsstrahlung form with temperature 13.1 keV cannot be excluded. No indication of spectral variability is found in three observations of the source with HEAO-A2, although a possible 15-30 percent intensity change over a period of 6 months was observed. The quasar is similar to 3C 273 in the proportion of energy emitted in various bands, excluding the radio, if reported radiation above 50 keV from its direction is indeed associated with QSO 0241+622. The two quasars are compared and possible energy generation scenarios are discussed. Implications concerning quasar contributions to the diffuse background are discussed.

Worrall, D. M.↗
NASA NTRS1980

Interstellar gas in the Gum Nebula

A survey of the interstellar gas near the Gum Nebula by optical observation of 67 stars at Ca II, 42 stars at Na I, and 14 stars in the UV with the Copernicus satellite provided radial velocities and column densities for all resolved absorption components. Velocity dispersions for gas in the Gum Nebula are not significantly larger than in the general interstellar medium; the ionization structure is predominantly that of an H II region with moderately high ionization. Denser, more highly ionized clouds are concentrated toward the Gum Nebula; these clouds do not show the anomalously high ionization observed in the Vela remnant clouds.

Wallerstein, G.↗
NASA NTRS1980

X-ray observations of the OAO1653-40 field

The region of sky containing OAO1653-40 have been observed simultaneously with the Einstein and Copernicus satellites in 1979 August. A best position of RA = 254.318 degrees, Dec = -41.577 degrees (1950) and a period of 38.019 + or - 0.009 sec were obtained for the X-ray pulsar discovered by White and Pravdo. The X-ray spectrum shows considerable photoelectric absorption with an equivalent hydrogen column density of 2.3 x 10 to the 23rd atom per sq cm. An upper limit to any 0.5-3.0 keV flux from V861 Sco of (4 + or - 1) x 10 to the -13th erg /sq cm/sec was also obtained.

Parmar, A. N.↗
NASA NTRS1981

Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2O, NO, NO2, and HNO3

A program for the measurement of latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2 and HNO3 is described, which uses airborne Fourier transform absorption spectroscopy to simultaneously determine columns, above 12 km, of the four molecules. The data may prove useful for comparison with two-dimensional models of stratospheric chemistry, since simultaneous measurement of several species with the same technique provides an inherently more reliable set for model comparisons, by eliminating uncorrelated atmospheric variability and reducing differences in instrumental biases.

Coffey, M. T.↗
NASA NTRS1981

The detection of HCN on Jupiter

The detection of HCN on Jupiter is reported. Three R-branch lines of the nu-2 fundamental of HCN near 13.5 microns were observed in absorption, from which the HCN column density is inferred to be 0.005 cm-am with an uncertainty of a factor of two. If emission from the stratosphere exists, then the derived column density is only a lower limit. It is suggested that the Jovian HCN most likely originates from the photolysis of CH4 and NH3 in the lower stratosphere and upper troposphere. In addition, an upper limit of 0.025 cm-am was established for the column density of HCN on Saturn.

Tokunaga, A. T.↗
NASA NTRS1983

Mg II profile variations of Zeta Aurigae

Variations in the Mg II 2800-A doublet of Zeta Aurigae have been observed. The Mg II profiles deviate from simple P-Cygni profiles in that they exhibit an absorption feature consistent with Chapman's (1981) interpretation of C IV absorption as evidence of a column of accretion onto the B-star component of the binary. The opening angle of the shock cone containing the accretion column is found to exceed 16 deg, implying a stellar wind velocity of approximately 67 km/s, unless the H II region temperature is unusually high. The turbulence velocity of the wind then appears to be about 33 km/s, compared to values of order 10 km/s previously determined closer to the K-star surface.

Ahmad, I. A.↗
NASA NTRS1990

Measurement of the solar UV flux in the stratosphere

Measurements of the direct solar flux from balloons at an altitude of 40 km are used to determine the effective cross sections of the Schumann-Runge bands. Transmission in these bands, which lie between 180 and 200 nm, allows the Sun's radiation in this region of the spectrum to penetrate into the lower mesosphere. Measurements by a high resolution scanning spectrometer (0.02 nm) are used to measure the transmission in the Schumann-Runge bands. Since ozone absorbs in this wavelength region, a low resolution scanning spectrometer (0.25 nm) measures the transmission between 220 and 260 nm, allowing the column ozone to be determined. Absorption due to ozone can then be calculated and the data corrected for this effect.

Mentall, James E.↗