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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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At least 991 records · Page 55
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NASA NTRS1989

Infrared circumstellar shells - Origins, and clues to the evolution of massive stars

The infrared fluxes, spatial and spectral characteristics for a sample of 111 supergiant stars of spectral types F0 through M5 are tabulated, and correlations examined with respect to the nature of their circumstellar envelopes. One-fourth of these objects were spatialy resolved by IRAS at 60 microns and possess extended circumstellar shell material, with implied expansion ages of about 10 to the 5th yr. Inferences about the production of dust, mass loss, and the relation of these characteristics of the evolution of massive stars, are discussed.

Stencel, Robert E.↗
NASA NTRS1989

A reexamination of luminosity sources in T Tauri stars. I - Taurus-Auriga

An analysis is presented of 72 T Tau stars identified by IRAS in the Tau-Aur complex. The composite energy distributions of the stars are constructed to define bolometric luminosities and the luminosity components in different spectral regimes are separated. The near- to far-IR spectral indices of these stars are analyzed. It is shown that 2/3 of typical T Tau stars have a bolometric to stellar luminosity ratio of about 1.0, which implies no appreciable disks. The distribution is bimodal, however, with a second peak at about 2.0, suggesting that 1/3 of the stars have disks. The bolometric luminosities of the north and south components of T Tau are found to be in the range of 9-21 solar luminosities and 1.5-14 solar luminosities for T Tau N and T Tau S, respectively.

Cohen, Martin↗
NASA NTRS1989

Erosion of circumstellar particle disks by interstellar dust

Circumstellar particle disks appear to be a common phenomenon; however, their properties vary greatly. Models of the evolution of such systems focus on internal mechanisms such as interparticle collisions and Poynting-Robertson drag. Herein it is shown that 'sandblasting' by interstellar dust can be an important and even dominant contributor to the evolution of circumstellar particle disks. Stars spend up to about 3 percent of their main-sequence lifetimes within atomic clouds. Among an IRAS sample of 21 nearby main-sequence A stars, beta Pictoris has the brightest disk; it also possesses the smallest random velocity and therefore the slowest predicted erosion rate.

Lissauer, Jack J.↗
NASA NTRS1989

An infrared survey of Galactic supernova remnants

A survey of Galactic supernova remnants (SNRs) in the infrared has been completed. Flux densities or upper limits on the flux densities have been measured for 157 objects in each of the four broad bands surveyed by the Infrared Astronomical Satellite (IRAS). Nearly one-third of the known SNRs exhibit some evidence of infrared emission. Confusion with other Galactic sources is a serious problem. Contour maps and halftone images are presented for 51 SNRs which are probable infrared sources. Initial analysis indicates that both the infrared spectra or colors and the ratio of infrared to radio brightnesses can discriminate between the youngest SNRs and older SNRs. In general, however, SNRs cannot be distinguished from other Galactic sources solely on the basis of their infrared colors. No apparent relation is found between the infrared surface brightnesses and the diameters of SNRs.

Arendt, Richard G.↗
NASA NTRS1988

Space Cryogenics Workshop, University of Wisconsin, Madison, June 22, 23, 1987

Papers are presented on liquid helium servicing from the Space Station, performance estimates in the Superfluid Helium On-Orbit Transfer Flight Experiment, an analytical study of He II flow characteristics in the SHOOT transfer line, a Dewar to Dewar model for superfluid helium transfer, and mechanical pumps for superfluid helium transfer in space. Attention is also given to the cavitation characteristics of a small centrifugal pump in He I and He II, turbulent flow pressure drop in various He II transfer system components, slip effects associated with Knudsen transport phenomena in porous media, and an integrated fountain effect pump device for fluid management at low gravity. Other papers are on liquid/vapor phase separation in He-4 using electric fields, an enclosed capillary device for low-gravity management of He II, cavitation in flowing superfluid helium, the long-term performance of the passive thermal control systems of the IRAS spacecraft, and a novel approach to supercritical helium flight cryostat support structures.

Source record↗
NASA NTRS1989

New emission features in the 11-13 micron region and their relationship to polycyclic aromatic hydrocarbons

Moderate-resolution spectra of NGC 7027, HD 44179, IRAS 2182+5050, and BD +30 deg 3639 are presented, showing that the 11.3-micron feature actually peaks at 11.22 microns. Evidence is found for new emission features near 11.9 and 12.7 microns, supporting an origin from PAHs. Also, the observed asymmetry of the 11.3-micron band is consistent with the anharmonicity expected in the C-H out-of-plane bending mode in PAHs. The analysis of the 11-13-micron emission suggests that the molecular structures of the most intensely emitting free PAHs vary between the high-excitation environment in NGC 7027 and the low-excitation but high-flux environment close to HD 44179. In addition, a series of regularly spaced features between 10 and 11 microns is detected in the spectrum of HD 44179, suggesting that a simple polyatomic hydride is present in the object's gas phase.

Witteborn, F. C.↗
NASA NTRS1989

An interactive, discipline-independent data visualization system

The data visualization techniques used by National Space Science Data Center Graphics System are discussed. The system includes a self-describing data abstraction for the storage and manipulation of multidimensional data for discipline-independent scientific applications. The system's data format and graphics display are described. Consideration is given to techniques developed for the rapid display and manipulation of large, complex data sets and for manipulating algorithms with portable implementations which can operate on any data object or geometry. The processes of operating the system are given and examples are presented from applying the system to various types of data, including TOMS data, data from the International Satellite Cloud Climatology Project, and IRAS data.

Treinish, Lloyd A.↗
NASA NTRS1989

Far-infrared properties of flare stars and dM stars

Results are reported from a search of the IRAS data base for flare stars and for a control sample of dM stars. At 12 microns, 70-80 percent of both samples have been detected. The K-12 colors of flare stars are significantly different from those of dM stars: for a given K magnitude, a flare star is about 70 percent brighter at 12 microns than a dM star. At 100 microns, 27 percent of the flare stars which are sources at 12 microns have been detected, while none of the comparable dM stars has been detected. Implications for microflaring are discussed.

Mullan, D. J.↗
NASA NTRS1989

On the temperature and gas composition in the region of comet formation

The gas composition and temperature in the region of Comet Halley's formation are estimated on the basis of Giotto and Vega spacecraft results, in conjunction with an experimental study of gas-mixture trapping in amorphous water ice. A CO/CH4 ratio of the order of 100, and temperature about 48 K, are inferred for the case of Halley formation in the solar nebula through water vapor condensation in the presence of gas. This formation temperature, which implies that the ice was in amorphous form, is noted to be close to the temperatures observed in circumstellar dust shells by IRAS; it also lends support to the suggestion that short-period comets were formed outside the planet-formation region.

Bar-Nun, Akiva↗
NASA NTRS1989

Pluto's atmosphere - Models based on refraction, inversion, and vapor-pressure equilibrium

Viking spacecraft radio-occultation measurements indicate that, irrespective of substantial differences, the polar ice cap regions on Mars have inversions similar to those of Pluto, and may also share vapor pressure equilibrium characteristics at the surface. This temperature-inversion phenomenon occurs in a near-surface boundary layer; surface pressure-temperature may correspond to the vapor-pressure equilibrium with CH4 ice, or the temperature may be slightly higher to match the value derived from IRAS data.

Eshleman, Von R.↗
NASA NTRS1989

Global properties of infrared bright galaxies

Infrared flux densities of 182 galaxies, including 50 galaxies in the Virgo cluster, were analyzed using IRAS data for 12, 25, 60, and 100 microns, and the results were compared with data listed in the Point Source Catalog (PSC, 1985). In addition, IR luminosities, L(IRs), colors, and warm dust masses were derived for these galaxies and were compared with the interstellar gas masses and optical luminosities of the galaxies. It was found that, for galaxies whose optical diameter measures between 5 and 8 arcmin, the PSC flux densities are underestimated by a factor of 2 at 60 microns, and by a factor of 1.5 at 100 microns. It was also found that, for 49 galaxies, the mass of warm dust correlated well with the H2 mass, and that L(IR) correlated with L(H-alpha), demonstrating that the L(IR) measures the rate of star formation in these galaxies.

Young, Judith S.↗
NASA NTRS1989

Cosmological velocity correlations - Observations and model predictions

By applying the present simple statistics for two-point cosmological peculiar velocity-correlation measurements to the actual data sets of the Local Supercluster spiral galaxy of Aaronson et al. (1982) and the elliptical galaxy sample of Burstein et al. (1987), as well as to the velocity field predicted by the distribution of IRAS galaxies, a coherence length of 1100-1600 km/sec is obtained. Coherence length is defined as that separation at which the correlations drop to half their zero-lag value. These results are compared with predictions from two models of large-scale structure formation: that of cold dark matter and that of baryon isocurvature proposed by Peebles (1980). N-body simulations of these models are performed to check the linear theory predictions and measure sampling fluctuations.

Gorski, Krzysztof M.↗
NASA NTRS1989

Contributions of low-luminosity sources to the X-ray background

We have exploited the HEAO 1 A-2 data base to determine hard X-ray fluxes, or upper limits, for complete optically selected samples of active and normal galaxies, in order to estimate or to constrain their local X-ray luminosity functions. We find that the luminosity function of Seyfert nuclei must flatten down drastically shortly below the observational limit of Piccinotti et al.; little can be added by dwarf active nuclei hidden in otherwise normal galaxies. We also analyze the possible contribution to the X-ray background from galaxies with strong star formation activity, in the light of the possibility of a substantial cosmological evolution suggested by recent radio and IRAS data.

Nuclei galaxies↗
NASA NTRS1989

AGB evolution in the Large Magellanic Cloud

Observations and theoretical studies of the evolution of massive asymptotic giant branch (AGB) stars in the Magellanic Clouds are reviewed. Recent results support the hypothesis that AGB is truncated, probably through mass loss, before these stars can attain the theoretically predicted maximum luminosity. In particular, IRAS observations of the LMC provide little evidence for the presence of highly obscured 'cocoon' stars.

Reid, Neill↗
NASA NTRS1989

Newborn stars and stellar winds in Barnard 228

Imaging and spectroscopic observations of premain-sequence stars in the B228 molecular cloud have identified three sites of extended, shock-excited nebulosity. A highly collimated, blueshifted jet is associated with the T Tauri star Sz68 (CoD -33:10685 deg). A candidate Herbig-Haro object is found near Sz68 and the T Tauri star Sz69. A third region of shock-excited nebulosity is identified near the embedded newborn star IRAS 15398-3359. IR excesses observed toward these stellar sources may imply a relationship between outflow activity and the presence of a circumstellar disk. Only one of the two outflow sources with well-defined orientations is aligned with the large-scale, magnetic-field geometry of the cloud in contrast to the global alignment of outflows in the Taurus cloud complex. Data for three previously unidentified emission-line stars are presented. A faint 18th magnitude dMe star located 48 arcsecs west of Sz68 is identified.

Heyer, Mark H.↗
NASA NTRS1990

Stability Of A Carbon-Dioxide-Removing Resin

Report describes experiments determing long-term chemical stability of IRA-45, commerical ion-exchange resin candidate for use in removing CO2 from atmosphere of Space Station. In proposed system, cabin air passes through resin, and acidic CO2 absorbed by weakly-basic hydrated diethylenetriamine bonded to porous resin substrate. When resin absorbs all CO2, disconnects from airstream and heated with steam to desorb CO2. Resin reuseable. Removed by post-treating process air with phosphoric acid on charcoal. Other chemicals removed by trace-contaminant-control subsystem of Space Station.

Wydeven, Theodore↗
NASA NTRS1989

Analytical derivation and verification of zero-gyro control for the IUE satellite

The International Ultraviolet Explorer (IUE) satellite was launched January 26, 1978 into a geosynchronous orbit over South America. From its stationary position, the telescope maintains continuous communication with the control centers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and at the European Space Agency's (ESA's) Villagranca del Castillo Satellite Tracking Station in Spain. Since its launch in 1978, the satellite has gradually lost four of the original six gyroscopes in the Inertial Reference Assembly (IRA). In August 1985, the fourth of the original six gyros failed and a two-gyro system developed by NASA-GSFC was uplinked to the satellite and is currently in use. A one-gyro system also developed by NASA-GSFC is ready for use in case of another gyro failure. In the event that the sixth gyro should also fail, a zero-gyro system is being developed. The goal of this system is to provide interial target pointing without the use of gyroscopes. The satellite has sun sensors to provide attitude information about two of the three axes. It relies upon the exchange of reaction wheel momenta to determine angular position and rate of the third axis.

Bowles, Tiffany↗
NASA NTRS1989

AFGL ten micron mosaic array spectrometer: Recent results

Recent measurements were made with a novel mosaic array prism spectrometer on long period variable stars of carbon and oxygen-rich atmospheres. These stars have generally large IR excesses and show strong SiC and silicate emission features, respectively. A comparison is provided by published spectra obtained with the IRAS Low Resolution Spectrometer. Emission feature equivalent widths are independent of the absolute photometric level of the spectra and provide information on the relative variation of the feature and continuum fluxes between the epochs of the space and groundbased observations.

Levan, Paul D.↗