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Results for “ULTRAVIOLET SPECTRA”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Visible and near-ultraviolet spectra of low-pressure rare-gas microwave discharges

The spectral emission characteristics of three commercial low pressure rare gas discharge lamps wire obtained in the near ultraviolet and visible wavelength range. All three lamps show a definite continuum over the entire wavelength range from 0.185 to 0.6 micrometers. Considerable line emission is superimposed on much of the continuum for wavelengths greater than 0.35 micrometers. These sources were used to make transmittance measurements on quartz samples in the near ultraviolet wavelength range.

Campbell, J. P.↗
NASA NTRS1994

Ultraviolet spectra and geometric albedos of 45 asteroids

Spectral reflectances and geometic albedos between 2300 and 3250 A are determined for 45 asteroids from data acquired by the International Ultraviolet Explorer satellite. The geometric albedos are consistently low, ranging from approximately 0.02 for C-type asteroids to approximately 0.08 for M-type asteroids. An exception is the single E-type asteroid (44 Nysa) with a geometric albedo of 0.3 at 2950 A. We find that the three major asteroid taxonomic classes persist into the UV. The taxonomic classes are distinguished primarily by their albedos, but S types are generally redder than C or M types. The first ultraviolet phase curved of asteroids are presented.

Roettger, E. E.↗
NASA NTRS1994

Ultraviolet Spectra and Geometric Albedos of 45 Asteroids

Spectral reflectances and geometric albedos between 2300 and 3250 Angstroms are determined for 45 asteroids from data acquired by the International Ultraviolet Explorer satellite. The geometric albedos are consistently low, ranging from ~0.02 for C-type asteroids to ~0.08 for M-type asteroids. An exception is the single E-type asteriod (44 Nysa) with a geometric albedo of 0.3 at 2950 Angstroms. We find that the three major asteroid taxonomic classes persist into the UV. The taxonomic classes are distinguished primarily by their albedos, but S-types are generally redder than C- or M-types. The first ultraviolet phase curves of asteroids are presented.

International↗
NASA NTRS1988

The outer atmospheres of the coolest M giants - Ultraviolet spectra of Rho Persei, 2 Centauri, g Herculis, Theta Apodis, and R Lyrae

New IUE observations of five M giants cooler than most studied previously have been obtained in order to study the variation of chromospheric properties with effective temperature. The ultraviolet spectrum lines of one of these stars, Rho Persei, are identified. The properties of the spectra of of the five stars are examined in detail, including the line widths and turbulence, the radial velocities of groups of lines, the structure in the Mg II resonance lines, and the fluorescent lines. The physical properties of the M giants' chromospheres are considered, including the formation of Fe II, the electron density, the degree of ionization of iron, magnesium, silicon, and carbon, the hydrogen ionization and energy balance, and the creation and destruction of photons.

Eaton, Joel A.↗
NASA NTRS1986

Studies of the ultraviolet spectra of astronomical sources

An intensive program of observations of the Comet Halley during the week of the Vega 2 and Giotto encounters was carried out by the International Ultraviolet Explorer (IUE) satellite observatory. The IUE Fine Error Sensor, normally used for target acquisition and tracking, was used in a photometer mode to provide nealy continuous light curves over an 8 hour observing shift, a unique capability relative to ground-bases observers. The ultraviolet data can be used to derive an estimate of the total gas production rate even though the models generally used for this purpose assume a steady-state gas production which is clearly not the case for Halley. Additionally, the IUE data provide column abundances of carbon, oxygen, sulfur, OH, CO, CS, C2, and CO2 to compare with the in-situ measurements of these species by Vega 2 and Giotto.

Source record↗
NASA NTRS1997

Simultaneous X-ray and Far-Ultraviolet Spectra of AGN with ASCA and HUT

We obtained ASCA spectra of the Seyfert 1 galaxy NGC 3516 in March 1995. Simultaneous far-UV observations were obtained with the Hopkins Ultraviolet Telescope on the Astro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed power law of energy index 0.78. The low energy absorbing column is significantly less than previously seen. Prominent 0 VII and 0 VIII absorption edges are visible, but, consistent with the much lower total absorbing column, no Fe K absorption edge is detectable. A weak, narrow Fe K(alpha) emission line from cold material is present as well as a broad Fe K(alpha) line. These features are similar to those reported in other Seyfert 1 galaxies. A single warm absorber model provides only an imperfect description of the low energy absorption. In addition to a highly ionized absorber with ionization parameter U = 1.66 and a total column density of 1.4 x 10(exp 22)/sq cm, adding a lower ionization absorber with U = 0.32 and a total column of 6.9 x 10(exp 21)/sq cm significantly improves the fit. The contribution of resonant line scattering to our warm absorber models limits the Doppler parameter to less than 160 km/s at 90% confidence. Turbulence at the sound speed of the photoionized gas provides the best fit. None of the warm absorber models fit to the X-ray spectrum can match the observed equivalent widths of all the UV absorption lines. Accounting for the X-ray and UV absorption simultaneously requires an absorbing region with a broad range of ionization parameters and column densities.

Kriss, Gerard A.↗
NASA NTRS1981

Integrated fluxes for emission lines in the ultraviolet spectra of several planetaries

The IUE satellite observatory was used to obtain absolutely-calibrated emission line fluxes for diagnostic lines of multiply-ionized C, N, O, Si, Ne, and Ar which occur in the ultraviolet spectral region of planetary nebulae. These data, when combined with data from the blue, visual, and near infrared, provide improved estimates of ionic concentrations, plasma temperatures and densities, and elemental abundances.

Carpenter, K. G.↗
NASA NTRS1981

The ultraviolet spectra of early type galaxies

The average spectral energy distribution for a sample of bright elliptical galaxies is presented in the range lambda lambda 2000 to 3200 A. Spectral synthesis indicates that elliptical galaxies are most likely older than 9 Gyrs. The ultraviolet flux is consistent with a population of red horizontal branch stars, as those present in metal rich globular clusters. Data for distant first ranked cluster galaxies show indications of spectral evolution.

Bruzual, A. G.↗
NASA NTRS1977

Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud

Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.

Carruthers, G. R.↗
NASA NTRS1986

Ultraviolet spectra of the N-type carbon star TX Piscium

Nine IUE low resolution spectra of TX Psc, one of the brightest N-type carbon stars, were analyzed. The integrated flux of the Mg II (UV 1) line (blend of h and k) varies by a factor of 7, and the flux of other lines varies similarly and in phase. No variations greater than a factor of 2 occur in the continuous flux. Synthetic spectra from a model chromosphere show surprisingly good agreement with the IUE observations. The enormous influence of the wings of the Mg I resonance line is noted, suggesting it may be a major part of the well-known violet and ultraviolet opacity in cool carbon stars.

Johnson, Hollis R.↗
NASA NTRS1982

Ultraviolet spectra of Herbig-Haro objects and of the environment of the Cohen-Schwartz star

Observations in both spectral regions were used in order to determine the continuous energy distribution and the emission line fluxes for H-H 2. The continuous spectrum is similar to that in H-H 1 and F lambda increases rapidly towards shorter wavelengths. This statement is found to be qualitatively correct for all obvious choices of the ultraviolet extinction curve if we use the E(B-V) value determined by the use of the S II method. The origin of the continuum remains enigmatic. The emission line spectrum of H-H 2 shows an even somewhat higher degree of ionization than the spectrum of H-H 1, indicating an even larger discrepancy between ionization information from optical data and that contained in the UV spectra. The immediate environment of the Cohen-Schwartz star emits a continuous spectrum similar to that of a H-H-object but increasing even more steeply towards shorter wavelengths.

Boehm, K. H.↗
NASA NTRS1976

Vacuum ultraviolet spectra of uranium hexafluoride/argon mixtures

The transmission properties of room temperature helium at pressures up to 20 atmospheres were determined in the wavelength range from 80 to 300 nm. Similarly, the transmission properties of uranium hexafluoride at 393 K (pressures less than 1.0 mm) were determined in the wavelength range from 80 to about 120 nm. The results show that high pressure helium is sufficiently transparent in the vacuum ultraviolet region (provided trace contaminants are removed) to be utilized as a transparent purge gas in future fissioning gaseous uranium plasma reactor experiments. Absorption cross sections for uranium hexafluoride were calculated from the data between 80 and 120 nm and were of the order of 10 to the -17 power sq cm.

Krascella, N. L.↗